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Oxygen-related biofacies in slope sediment from the Western Gulf of California, Mexico
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Oxygen-related biofacies in slope sediment from the Western Gulf of California, Mexico
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INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. UMI A Bell & Howell Information Company 300 North Zeeb Road, Ann Arbor MI 48106-1346 USA 313/761-4700 800/521-0600 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R e p ro d u c e d with p erm issio n of th e copyright ow ner. F u rth e r reproduction prohibited w ithout perm issio n . NOTE TO USERS This reproduction is the b est copy available UMI Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. R e p ro d u c e d with p erm issio n of th e copyright ow ner. F u rth e r reproduction prohibited w ithout perm issio n . OXYGEN-RELATED BIOFACES IN SLOPE SEDIMENT FROM THE WESTERN GULF OF CALIFORNIA, MEXICO Copyright 1998 by Teresa Ann De Diego A Thesis Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF SCENCE (Geological Sciences) December 1998 Teresa Ann De Diego Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI N um ber: 1 394766 UMI Microform 1394766 Copyright 1999, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UNIVERSITY O F S O U T H E R N C ALIFO R NIA THE GRADUATE SCHOOL UNIVERSITY PARK LOS ANGELES, CALIFORNIA 9 0 0 0 7 This thesis, written by ._ m e rja s a ..J iim „ D .e „ J li£ .g :Q _______________________ under the direction of hj~IL Thesis Committee, and approved by all its members, has been pre sented to and accepted by the Dean of The Graduate School, in partial fulfillment of the requirements for the degree of Master of Science Date D e c e m b e r 10, 1998 T H E S I S ^ C O M M I ' JLu Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DEDICATION u I would like to dedicate this thesis to my parents who helped me get through college. They were always proud of everything I endeavored to do and never told me what I couldn’t do. I would also like to dedicate this to my boyfriend, Kenny Forbis, who was always there for me when I thought I couldn’t do this. You always said I could and well, I did. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. hi ACKNOWLEDGEMENTS I would like to thank first and foremost Dr. Robert Douglas. Without his help I would probably still be sitting and staring at the X-radiographs trying to figure out what I was seeing. His editing work on this paper is greatly appreciated, otherwise, no one but myself would understand it. Thank you for everything Dr. Douglas! I would also like to thank Dr. Donn Gorsline for teaching me how to use the Leco Apparatus for the carbonate and organic carbon analyses and the X-ray machine for the X-radiographs. His advise on the various subjects needed for this paper was greatly appreciated. I also thank him for the all the time and effort he put in to help me slab cores and X-radiograph them in time for this paper. Dr. David Bottjer’s help and advice with the sediment fabrics analysis is much valued. I would also like to thank him for his help in editing this paper. T would like to next thank Dr. Douglas Hammond for his help and patience in teaching me how to determine the opal silica in sediments. I am very thankful for the use of this technique and his Photospectrometer. In doing the research for this paper, I had the great fortune to work with Kristi Rikansrud, another graduate student at USC, whose work ran parallel to mine. Thank you Kristi, for all the help and use of your data. I would also like to thank her for just being there, otherwise the lab would have been very boring. I would also like to acknowledge Dr. Adolfo Molina-Cruz, for inviting the Earth Science Department at U.S.C. to take part in the past three Paleo-cruises. Without his help there would be no data for this research. I would also like to thank him for allowing me to participate in the last cruise, Paleo-IX. I enjoyed myself thoroughly on that cruise and learned all the fine points of core sampling and what the Gulf of California looks like from a ship. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Last but not least, I would like to thank Enrique Nava-Sanchez, for all the work he did in Gulf and for producing so many wonderful graphs which were useful for this paper. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V TABLE OF CONTENTS Dedication ii Acknowledgements tii List of Figures vn List of Tables x Abstract xi Chapter 1 1 Introduction 1 Purpose 1 Core Data 3 General Background 3 Plate Tectonics 8 Water Masses and Circulation 10 Thermohaline Circulation 11 Water Masses 13 Tides 15 Primary Productivity 15 Gulf Sediments and Lamination Formation 16 Organic Carbon in Sediments 20 Carbonate in Sediments 22 Sediment Fabrics 23 Chapter 2 36 Study Methods 36 Field Methods 36 Sediment Core Sampling 36 Laboratory Methods 37 Carbonate and Organic Carbon Analyses 37 Silica Analyses 39 Macrobenthic Organism Analyses 41 X-Radiograph Analyses 41 Chapter 3 43 Results 43 Carbonate and Organic Carbon 43 Silica Analyses 50 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VI Macrobenthic Organism Analyses 51 Alfonso Basin/La Paz Basin 51 Santa Rosalia 53 X-Radiograph Analysis 54 Potential Errors 54 Chapter 4 55 Discussion 55 Geochemical Data 55 Core CP 55 Carbonate 55 Organic Carbon 58 Opal Silica 59 Core FF 59 Carbonate 61 Organic Carbon 63 Opal Silica 63 Comparison of core FF and core CP 63 X-Radiographs 65 Surface Patterns 65 Down Core 69 Alfonso Basin 69 Santa Rosalia 69 Macrobenthic Organisms Analyses 70 Alfonso Basin 70 Santa Rosalia 72 Patterns o f Bioturbation and Lamination 72 Chapter 5 79 Conclusions 79 F urther Research 81 References 82 Appendix 1 86 Appendix 2 92 Appendix 3 95 Appenidx 4 102 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VII LIST OF FIGURES Figure 1. Bathymetry of the Gulf of California 2 Figure 2. Location map of the Gulf of California and research sites, Santa Rosalia and El Coyote (from Nava-Sanchez, 1997). 4 Figure 3. Bathymetry of Alfonso Basin. Localities of cores are plotted on the map 6 Figure 4. Bathymetry of Offshore Santa Rosalia Locality. Locations of cores are plotted on the map 7 Figure 5. Tectonic map of the Gulf of California. Extension shown occurring in a rifting transform system (from Nava-Sanchez 199 9 Figure 6. A) Diagram of upwelling patterns in the Gulf of California. Upwelling areas: a) with northwesterly winds, b) with southeasterly winds and c) area characterized by intense tidal mixing(ffom Roden and Groves 1959). B) Gyres in the Gulf of California. From north to south: the cyclonic Guaymas gyre, the anticyclonic Carmen gyres and the cyclonic Farallon gyre (from Molina-Cruz 1986). 12 Figure 7. Diagram of water masses in the Gulf of California. a) Longitudinal profile and the water mass distributions. Arrows indicate the hypothesized thermohaline circulation. b) T-S characteristics of the Gulf water masses. Vertical exaggeration = 5x (from Bray 1988). 14 Figure 8. Sources and dispersion of sediments in the Gulf of California exaggeration = 5x (from Bray 1988). 18 Figure 9. Schematic diagram o f sediment microfabric types. Corresponding bottom water oxygen levels and relative position of the redox level. 30 Figure 10. X-radiograph of core CP showing sediment microfabric type 2. In this type microfabric laminations are well defined and continuous. 32 Figure 11. X-radiograph of sediment microfabric type 3A. In this sediment type, laminations are wavy and not always continuous. 33 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. v iii Figure 12. X-radiograph of core CP showing sediment microfabric type 3B. This sediment type is semi-laminated with blurred lamination boundaries. Figure 13. X-radiograph of core CP shows sediment microfabric type 4. This sediment type is bioturbated. Figure 14. Comparison of sediment microfabrics, carbonate, total organic carbon and silica opal plotted against core depth in core Figure 15. Comparison Scatter Plot of Geochemical Data From Core CP. Total Organic Carbon vs. Carbonate, Carbonate vs. Silica Opal and Total Organic Carbon vs. Silica Opal were compared to determine any correlating characteristics. Figure 16. Comparison of sediment microfabrics, carbonate, total organic carbon and silica opal in core FF, plotted against core depth in ci Figure 17. Comparison Scatter Plots of Geochemical Data From Core FF. Total Organic Carbon vs. Carbonate, Carbonate vs. Silica Opal and Total Organic Carbon vs. Silica Opal were compared to determine any correlating characteristics. Figure 18. Profile of Alfonso Basin, with core locations, sediment microfabrics down core and location o f macrobenthic organisms Figure 19. Profile of Santa Rosalia, with core location, sediment fabric type down core and Iocationof macrobenthic organisms Figure 20. Plot of maximum age in years of oxygenation vs. depth in m in Santa Rosalia and Alfonso Basin. Figure 21. Comparison of sediment microfabrics down core from cores CB, CP and FF. Duration of oxygen cycles listed to the right. Figure 22. Schematic diagram of a typical ventilation cycle as seen in core sediments micro fabrics. Figure 23. Comparison of sediment microfabrics down core in core CP with potential oxygen levels at time o f deposition. 34 35 56 57 60 62 66 67 68 71 73 75 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. IX Figure 24. Variations in dissolved oxygen at the mouth (near La Paz) and mid Gulf (Santa Rosalia) at four intervals between 1939 and 1998. Data summaries from various sources, including Sverdrup (1939), Roden (1961), Alvarez-Borrego and Lara-Lara (1991) and Paleo-IX (1998). Hydrocasts in 1998 were only complete to 100( 76 Figure 25. Diagram shows the position and potential oxygen values of the oxygen minimum zone in the central gulf at different time interv 78 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. X LIST OF TABLES Table 1. Core and Sample Locations from the Gulf of California 5 Table 2. T-test and z-test values for Core CP 43 Table 3. Calculated Statistics for Core CP 44 Table 4. T-test values for core FF 46 Table 5. Calculated Statistics for Core FF 47 Table 6. T-test and z-test values for Cores CP and FF comparisons 49 Table 7. Macrobenthic Organisms in the Gulf of California 52 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. XI ABSTRACT Oxygen-related biofacies based on sediment microfabrics were analyzed from cores collected during cruises Paleo Vm and IX in the Gulf o f California. Cores from two different slope settings were used: At Santa Rosalia, located on the western side of the Gulf of California, [approximately in the middle of the Baja California Peninsula] 11 cores were collected on the open slope along a transect between 250m to 1250m water depth. Alfonso Basin, also located on the western side of the Gulf of California, near the southern end of the Baja California Peninsula, is a shallow, perched basin with maximum depths of420m and a sill at 275m. A total of 13 cores from the Alfonso Basin were used for this analysis. In addition to the sediment fabric analysis, carbonate, total organic carbon, and opal silica were determined for core CP in Alfonso Basin and core FF in Santa Rosalia. The sediment fabric model of Savdra-Bottjer (1993) was modified and used to interpret oxygen-related biofacies. Based on detailed examination of x-radiographs of core sediment, to the 5 original biofacies, type-1) anaerobic, type-2) quasi-anaerobic, type-3) exaerobic. type-4) dysaerobic and type-5) aerobic, was added a second exaerobic biofacies. The original type-3) exaerobic was renamed 3A and the new exaerobic is labeled 3B. These sediment microfabrics were used to interpret the pattern of down-core sediment fabrics which were in turn used as proxies of seafloor oxygen values. Use of this sediment microfabric model showed that there is an underlying pattern in the gulf sediments between times of bioturbation and times of laminations. The oxygen-biofacies pattern seen in the sediments in one of rapid oxygenation followed by a slow return to anoxia. This pattern is seen in both location sites. Age models based on varve counts and lead 210 profiles, indicate that these cycles lasted between 130 and 150 years. The tops of the cores also indicate that the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. X ll start of the latest cycle, with increased oxygenation o f the seafloor, began approximately 35 years ago. Geochemical analyses o f carbonate, total organic carbon and silica opal were used to evaluate the cause, of the biofacies patterns. Neither silica opal or total organic carbon correlate with sediment microfabrics, suggesting that the changes in sediment microfabrics are related to primary productivity. The effects of dissolution, however, is unknown and may have effected opal silica and total organic carbon. Carbonate, however, is correlated with sediment microfabric with increasing carbonate occurring with increased lamination. A plot o f dissolved oxygen values within the Oxygen Minimum Zone (OMZ) for the last 60 years indicate that the oxygen minimum zone has decreased in thickness and intensity (increased in oxygen levels), to the point that today the OMZ supports abundant benthos. A fairly rapid change in oxygen occurred sometime in the past 20 years, corresponding to the change observed in the sediment microfabric. This implies that the patterns o f sediment lamination and bioturbation in the Gulf of California is controlled by ventilation in oxygen levels within the oxygen minimum zone and that the oxygen minimum zone goes through a 130 - 150 year cycle of ventilation. Since the oxygen minimum zone lies within the Pacific Intermediate Waters this implies that the ultimate control of the pattern o f laminations and bioturbation within the Gulf of California may be primarily controlled by changes within the Pacific Intermediate Waters. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 1 1 Introduction Purpose Despite more than 60 years of oceanographic and geologic investigation, depositional systems in the Gulf of California remain poorly documented and understood. In general, the focus of past research in the Gulf has been on structural and tectonic geology with little on the geobiological aspects the o f sediments. This research focuses on the effects of biotic-sediment interactions as controlled by dissolved oxygen on the seafloor in two locations in the Gulf of California (Figure 1). The first location, Santa Rosalia, is located on the western side of the Gulf, in the middle of the peninsula. At this location, the open continental slope grades into the Guaymas Basin at a depth of > 1200m. The oxygen minimum zone intersects the slope at depths of 500 - 800m creating areas of anoxia on the seafloor. The second location, Alfonso Basin, is located off of the coast of El Coyote, just north of La Paz, in southern Baja California. This basin is a shallow perched basin about 420 m deep and a sill at 275m. These two locations represent different water depths and ocean floor topographies and offer different sediment environments in which to examine the occurrence of bioturbation and lamination in sediments. The formation of bioturbated and laminated sediments is controlled by seafloor oxygen levels. During times of adequate seafloor oxygenation, benthic burrowing organisms will be present and sediment fabrics will be disturbed. When seafloor oxygen levels are anaerobic, benthic organisms will be restricted or eliminated and sediment laminations will form. There are two models for the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9/ nnnm Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1. B athym etry of the Gulf of C a lifo rn ia formation o f laminated sediments. One is the formation of bottom anoxia by upwelling in which oxygen consumption is higher than it is replenished because the primary productivity is high and the other is by water circulation in which the replenishment of dissolved oxygen is limited by some barrier (Pederson and Calvert, 1990; Pilson, 1998). The main question is what controls the Oxygen Minimum Zone oxygen levels in the Gulf, is it the result of local surface primary productivity or due to oxygen levels in intermediate waters which form the OMZ? Core Data Data used in this project were obtained from core samples recovered by the Mexican research vessel, R/V El Puma during the Paleo VII (1994), PaleoVm (1996) and Paleo IX (1998) cruises (Figures 1 and 2 and Table 1). In Alfonso Basin, cores were taken at depths between 170 and 405m and at 620 m outside the basin (Figure 3). At Santa Rosalia, cores were collected along a slope transect (Figure 4) between 265 and 1250m. General Background The Gulf of California, or the Sea of Cortez, is a long, narrow marginal sea 1000km long by 100 km wide. (Figure 1). To the west, the Gulf is bordered by the Peninsula o f Baja California, a westward-tilting tableland. The steep Gulf coastline is interrupted only by the low isthmus at La Paz and by large alluvial fans. On the eastern side of the Gulf, south of Guaymas, an extensive coastal plain of Quaternary deltaic and littoral sediments borders the Sierra Madre Occidental Range. North of Guaymas, the Sonoran coastal area consists o f several mountain ranges rising through alluvial plains (van Andel, 1964). Due to the arid climates in the mainland states of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UNITED STATES OF AMERICA GUAYMAS. SANTA ROSALIA' MAZATLAN. CABO*' SAN LUCAS Figure 2. Location map of the Gulf of California and research sites, Santa Rosalia and El Coyote (from Nava- Sanchez, 1997). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 1. Core and Sample Locations from the Gulf of California. Area Cruise StationiLatitude Longitude Depth degree minutes degree minutes meters El Covote Paleo-VII CA 24 33.93 110 36.83 370 CB 24 38.91 110 34.3 391 CC 2 4 : 42.51 110 34.37 390 CD 24 43.49 110 36.18 380 CE 24 38.04 110 39.04 350 CF 2 4 ; 40.4 : 110 38.21 378 CG 24 41.79 110 36.38 385 € H 24 : 39.41 : 110 40.18 255 Paleo-VIIICF2 24 40.01 110 40.83 170 CL 24 49.56 110 27.8 620 CM 24: 40.85 110 25.43 405 CN 24 33.34 110 35.17 370 CP 24; 38.12 i 110 33.42 390 Paleo-EX 9 24: 38.04 i 110: 20.97 890 22 2 4 : 38.33 110 28.7 275 24 24 : 38.82 110: 36.88 395 25 24 38.09 i 110 37.04 420 Santa RosaliaPaleo-VII SR-22 27 20.1 112 12.6 360; Paleo-VIII FA 27 19.59 ! 112; 0.8 1250 : FB 21 25.18 112 i 4.84 880 : FC 27 30.59 112; 9.36 900 i FD 21' 22.66 112 8.44 740 : FF 27 21.46 112 9.94 620 : FG 27 20.41 112 13.09 330: FH 27 23.75 112 13.45 500 Paieo-IX 62 27 21.41; 112 4.88 1030 63 27 21.15 i 112 9.87 630 64 27 21.2 112 14.16 265 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6 CL GENERAL AREA OF ALFONSO BASIN B. COYOTE FAN DELTA LA PAZ BASIN < 2 * CM C B | i : x m 5 o : AULT 3 8 * 3 8 * CN 3 6 * 1 Rgure 3. Bathymetry of Alfonso Basin. Localities of cores are plotted on the map. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 4. Bathymetry of Offshore Santa Rosalia Locality. Locations of core are plotted o n the map. 8 Sonora and Sinaloa, to the east and the equally arid Baja California Peninsula on the west, the gulf is a large evaporation basin, with the main exchange to the Pacific Ocean at the southern end. The Colorado River, which enters the Gulf at the northern end, made a significant influence on to the environment and oceanography of the northern gulf, before it was dammed. Today its contributions is minimal. Topographically, the gulf can be divided into a series of basins, deepening to the south and separated by traverse ridges (Roden, 1964; Alvarez-Borrego and Schwartzlose, 1979). Hydrographically, the gulf can be divided into two different parts at the middle drift islands (Alvarez-Borrego, 1979; Bray, 1988; Alvarez-Borrego and Lara-Lara, 1991; Bray and Robles, 1991). Plate Tectonics The Gulf of California opening represents a rifting ocean system at the boundary of the Pacific and North American Plates (Figure 5; Nava-Sanchez, 1997). The transform faults in the Gulf lie parallel to the direction of the Pacific-North American plate motion and help to constrain it (Atwater, 1989). The Gulf of California is one of two currently active transform-rift plate boundaries in the world. Studies from Deep Sea Drilling Project (Moore and Curray, 1982) show that the rifting began at the mouth of the Gulf about 5.5 Ma. Magnetic anomalies indicate that the spreading rate at the mouth of the Gulf is about 5.6 mm/y and has been steady for at least 4.5 Ma. A simple model for tectonic evolution of the Gulf suggests that a convergent margin with a terrestrial volcanic arc was present prior to rifting about 25 to 12 Ma. Extensional faulting occurred behind the arc during this period (Axen, 1995; Umhoefer et al., 1996). The subduction zone shut down from north to south as a Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 30° N - 25c N - Diego- v N V V N . V V V X V V V V V S . N . V V V V ' V V NORTH AMERICAN Guaymas Basinyyy PACIFIC PLATE Cabo San Lucas East Pacific Rise Farallon Basinl'l'l'l'l'l'l I _ / / / / / / "V. \ \ \ \\ \ V \ \ N V V N / \N .V V N .\, V V V > . \N N S Pescadero Basin'\> — * - - % S % % V S V \ \ / / / / / / / / , \ \ S \ N S V \ / Ar /r A / / / Mazatlan^/!/^ Tamayo Transfer m y 1 / / y / RIVERA PLATE 115° W 110° W 105° W Figure 5. Tectonic map of the Gulf of California. Extension shown occurring in a rifting transform system (from Nava-Sanchez 1997) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10 transform plate boundary formed on the west side of future Baja peninsula. From about 15 to 5 Ma, a proto-gulf formed by rifting, with a transform system to the west of Baja California and a zone of extensional faulting in the present gulf and east on mainland Mexico. From about 5 Ma to the present the modem transform faults and rift basins system formed as the plate boundary shifted into the gulf (Umhoefer et al„ 1996). The opening of the Gulf o f California is attributed to two extentional event (Stock and Hodges, 1989). One from the middle to late Miocene protogulf extension and the other during the Pliocene development of the Pacific-North American Plate boundary. W ater Masses and Circulation The Gulf of California differs in many ways from other mid-latitude marginal seas. In the gulf, salinity and temperature both decrease with depth which prevents the expected two-layer thermohaline system of warm , low salinity surface inflow and cold, salty subsurface outflow. Also the gulf has a very high surface primary productivity (Alvarez-Borrego, 1983; Bray, 1988; Bray and Robles, 1991). Both of these characteristics are a result of atmospheric forcing. The gulf gains heat from the atmosphere at a rate of 20 - 80 W m ' 2 . while at the same time it is losing moisture to the atmosphere at a rate of about 1 m y 1 (Bray, 1988). These air-sea fluxes create a estuarine-style circulation with inflow' occurring at deeper depths than the outflow. This deep inflow also supplies the nutrients that form the highly productivity gulf waters. The circulation in the gulf is driven by the atmosphere through large-scale winds, air-sea fluxes of heat and moisture and temporally or spatially local Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I I phenomenon. The large-scale wind field over the gulf is monsoonal with seasonal signals consisting of northwesterly winds during the winter and southerly or southeasterly winds during the summer. These seasonal winds tend to modify the near-shore breeze, which led to seasonal shifts in upwelling, with upwelling occurring on the mainland coast during the winter and upwelling on the Baja Peninsula coast during the summer (Figure 6) (Molina-Cruz, 1986). Upwelling does not appear to play a dominant role in shelf circulation in the Gulf as it does along other coast lines (Bray and Robles, 1991). This maybe due to the fact that the G ulfs overall winds are weaker than those in upwelling-dominated systems. Other factors which may contribute to this is the that the Gulf is more stratified, tidal mixing plays an important role in the north Gulf, and the Gulf is a semi-enclosed sea which may limit certain types o f circulation (Bray, 1988; Bray and Robles, 1991). Thermohaline Circulation Thermohaline circulation in the Gulf occurs in such a way that cold, lower salinity water is imported into the Gulf at deeper depths and warm, high saline water is exported at shallower depths. This can be observed by the vertical structure of temperature and salinity in the Gulf, which both decrease with depth from the surface to about 600m. Bray (1988) and Bray and Robles (1991) demonstrated through empirical orthogonal function analyses that changes in the near stratification dominate both temperature and density structures across the Gulf. Bray (1988) and Bray and Robles (1991) also showed that salinity did not vary seasonally and the baroclinic velocity fields on the average were weakly cyclonic with the stronger cyclonic circulation occurring in the summer and weak but anticyclonic circulation in the spring and fall. Average profiles of temperature and salinity of the Gulf Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission o f the copyright ow ner. Further reproduction prohibited without perm issio n . B < a i A PUERTO PEMASCO ISLA ANGEL OE L A GUAROA k jI S L A TIBURON TOPOLOBAMPO LA PAZ CABO SAN LUCAS CABO CORRIENUS 105’W 1 1 0 * w Figure 6. A) Diagram o f upwelling patterns in the Gulf o f California. U pw elling areas: a) with northwesterly winds, b) with southeasterly winds, and c) area characterized by intense tidal m ixing (from Roden and Groves 1959). B) Gyres in the G ulf of California. From north to south: the cyclonic G uaymas gyre, the anticyclonic Carmen gyres, and the cyclonic Farallon gyre (from M olina-Cruz 1986). 13 demonstrate that water is outflowing between 50 and 250m, inflowing between 250 and 500m, and is variable in the top 50m. The surface layer shows tendencies to reverse direction with seasonal winds, southerly in the winter and northerly in the summer. Water Masses There are several water mass types in the Gulf and their presence varies depending on location in the Gulf (Alvarez-Borrego and Schwartzlose, 1979; Molina-Cruz, 1988; Bray, 1988; Bray and Robles, 1991) (Figure 7). At the southern end, where the Gulf meets the Pacific Ocean, the water mass stratification consists of Tropical Surface Waters, Subtropical Subsurface Waters, California Current Waters, Pacific Intermediate Waters and Pacific Deep Waters. Moving north towards the center of the Gulf the California Current and Surface Waters are replaced with the Central Gulf Waters. In the northern part of the Gulf, the Central Gulf Waters are in turn replaced by the Northern Gulf Waters and the Pacific Intermediate and Pacific Deep Waters are eliminated by the sill of the Ballenas Channel. The northernmost part of the Gulf contains the last water mass, the Wagner Basin Waters and the Colorado Delta Waters. Whereas the most common mechanisms for water mass formation is vertical convection, driven by rapid surface cooling. The cooling in Gulf produces a net heat gain and this type of water mass formation is not possible. When the Subtropical Subsurface Waters reaches the northernmost end of the Gulf where the Colorado Delta Water enters the Gulf, these waters are transformed through a variety of mechanisms, such as limited vertical convection, tidal mixing, and a buoyancy-driven, large-scale horizontal circulation pattern in the northern gulf, to produce the Northern Gulf Water (Bray, 1988; Bray and Robles, 1991). As the Northern Gulf Waters flow to the south, intense tidal mixing dismpts the vertical Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. D E P T H (m) 3 WATER MASS DISTRIBUTIONS IN THE GULF O F CAURDRMA DISTANCE (km) o 200 500 1000 1500 _ 2000 2500 - 3000 CDW- T SW ssw CCW N G W C G W Wagner Basin Demn oasm Farallon Basm Carmen Basin 10 00 TSW * Tropical Surtaca Watar CGW « Cantral Gulf Watar Guaymas Basin PACIFIC OCEAN CCW « CalH. Currant Watar SSW a Subtropical Subsurfa Watar PIW * Pacific Intartnadiata Watar PDW » Pacific Oaap Watar NGW » Nortbam Gulf Watar WBW « Wagnar Basin WaUr COW v Colorado Dalta Watar WATER MASSES O FTH E GULF OF CAUR0RMA 3 0 2 6 2 2 < 1 8 1 “ UJ ZC b- 1 4 1 0 6 2 T S W I » — J _J-— — t ^ — ~ ~ ~ 7 b o w ____ /-«-» i / - CGW r ' / ' n g w ^ ' __ V L l 5 /T • - -------- - S S W ^ ^ 1 " ' , , \ P D W y ' ; -----W B W ... ---------------------- - L - - - - 1 -------- 1 -------- 1 -------- 1 -------- 1 --------- 34 TSW « Tropical Surtaca W atar CCW - Calif. Currant W atar SSW m Subtropical Subsurface W atar 3 5 SALINITY, psu PIW • Pacific IntamMdiats Watar PDW m Pacific Oaap Watar 3 6 CGW « Cantral Gulf Water NGW m Northern Gulf Watar WBW » Wagner Basin Watar COW « Colorado Delta Watar Figure 7. Diagram of water masses in the Gulf o f California, a) Longitudinal profile and the water mass distributions. Arrows indicate the hypothesized thermohaline circulation, b) T-S characteristics o f the G ulf water masses. Vertical exaggeration = 5x (from Brav 1988). permission of the copyright owner. Further reproduction prohibited without permission. 15 circulation and results in the Central Gulf Waters, which contain a reduced salinity and increased volume. These Central Gulf Waters continue to the mouth of the Gulf. During El Nino years, the changing water mass distributions in the eastern Pacific Ocean cause an influx of surface tropical water masses far into the Gulf. These warm, lower salinity water masses appear to affect water mass formation in the northern part of the Gulf. During El Nino events, winter convection is more widespread. Tides The tides in the Gulf are dominated by co-oscilation with the Pacific. The amplitude of diumal tides do not change substantially with distance into the Gulf. The diumal tides appear to modeled by a standing wave pattern. The amplitude for the semi-diurnal tide, however, increases greatly into the Gulf. These tides in the Gulf dominate circulation near the midriff islands and tide currents are the most constant source o f energy for mixing in the northern Gulf. Tides are also one of the components of shelf circulation in the central and southern parts of the Gulf (Bray and Robles, 1991). Primary Productivity Based on phytoplankton distribution, the Gulf is divided into four geographical regions: The southern region is south of lat. 25 degrees N; the central region is between lat. 25 degrees N and 27 degrees N; the northern is region 27 degrees N and the Angel de la Guarda and Tiburon Island and; the inner region is north of the islands (Alvarez-Borrego and Lara-Lara, 1991). Surface productivity values are lower in the southern Gulf than the those in the northern. The highest values seem to be in Guaymas Basin and the region near the Angel de la Guarda and Tiburon Island. The lowest values were found in the central inner region of the Gulf Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 6 at all depths from the surface to 50m. Productivity values reflect the seasonality of upwellings in the Gulf, however, the periods o f productivity maxima are debatable. According to Alvarez-Borrego and Lara-Lara (1991) the highest values occur during the spring and beginning of summer with productivity dependent on two processes: The decline of northwesterly winds in the fall which cause upwelling and surface cooling in the upper Gulf At the beginning of summer when the northwesterly winds die down and surface waters warm up, the phytoplankton growth ends. This model has the largest population during the spring before the winds die. Pride et al. (1998) and Thunell (1998) show that the productivity maxima occurs in November when the northwesterly winds strengthen and upwelling begins, and a secondary productivity maxima occurs in February when eddy circulation carries nutrient-rich waters across the Gulf. During the El Nino-Southern Oscillation events primary productivity is greatly effected. How primary productivity is effected, however, it under debate as well. In the past, it was believed that ENSO events produced higher primary productivity values (Baumgartner et al., 1985; Lara-Lara et al., 1984), however more recent studies (Pride et al., 1998; Thunell, 1998) show that the opposite is true, that ENSO events produce lower primary productivity values than during non-ENSO events. Gulf Sediments and Lamination Formation Basin sediments in the Gulf of California are dominated by silty muds, containing large amounts of diatomaceous and radiolarian silica. North of lat. 26 degrees N, diatoms constitute the major source of biogenous opal (Calvert, 1964). In the southern Gulf, biogenous silica production is lower than the terrigenous sediment supply and silty clays predominate both on the slope and in the basins. Sandy foraminiferal and radiolarian sediments are found around isolate hills and banks. On Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17 the western slope, north of La Paz, coarse, highly glauconitic, foraminiferal calcarenites are found. Coarse sands and gravels that are highly volcanic are found north and south of the sills that separate the central Gulf from the south. The sediments of the eastern and western shelves of the central and southern Gulf are different. The western shelf is covered with coarse, highly calcareous sands and calcarenites. The eastern shelf sediments are also sandy, but the sands are not as coarse or calcareous. Almost everywhere, a transitional zone of clayey silt is well developed on the outer shelf and upper slope. In the northern Gulf, sands are glauconitic and foraminiferal rich and commonly mottled in structure (van Andel, 1964). There are three principle source areas which supply terrigenous sediments to the Gulf of California, all of which are mountainous with arid climates, little chemical weathering and rapid erosion (van Andel, 1964) (Figure 8). Acid-intermediate batholiths provide an amphibole-rich arkose, Ternary and Quaternary rocks supply basic volcanics with graywackes rich in pyroxenes, basaltic hornblende and volcanic rock fragments, and lastly, the mixed drainage basins of the Colorado, the Concepcion and the Costa de Hermosillo are source areas for arkosic or feldspathic sands with heavv-mineral suites containing characteristic amounts of stable minerals (van Andel, 1964). The basin in the northern Gulf is the largest area covered with Colorado sediments. These sediments were probably deposited during the post-Pleistocene sea level rise and are now in a nondepositional zone. The basin is fringed by marginal deposits derived from the hinterland with mainly longitudinal transportation . The central and southern Gulf areas are filled entirely from the sides with little or no longitudinal transportation. The sediment sources are batholithic and volcanic rocks with well defined distributive regions. On the western side, the boundaries of these provinces coincide with outcrop boundaries on land. On the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ''A "■ «'*< * / 7 % ALTERNATING OR SUPERIMPOSED VOLCANIC BATHOLITIC OR METAMORPHIC Colorado BATHOLITIC VOLCANIC | ] 0 . 200m [ J 1000 . 2000m | I 2 00. 1000m r n > 2000m B O U NDARYBETW EN EASTERN A ND W ESTERN SUPPLY PACIFIC L ________ x__ L OCEAN so 100 km Figure 8, Sources and dispersion of sedim ents in the Gulf of California (from van Andel, 1964) o o 1 9 eastern side, the situation is more complex because of many mixed-supply areas. However, the eastern margin, due to its higher precipitation and the presence o f many permanent streams, supplies more sediments to the Gulf than the Peninsula. Consequently, the zone o f marine sediments derived from the Peninsula is narrow and ends at the foot of the western slope. The eastern sources, however, supply not only the sediments forming the wide coastal plain and covering the continental shelf and slope but also most of the sediment in the G ulfs basins (van Andel, 1964). Slope and basin sediments in the Gulf consist of homogenous and laminated types. Homogenous sediments vary from totally bioturbated to occasional burrows to fuzzy laminations. Laminated sediments contain alternating bands of dark and light laminae. The origin of laminae formation has been much debated over the years. Biyne and Emery (1960) suggested that the laminae were from a seasonal pulse of diatoms and a constant supply of inorganic material. Calvert (1966), however, suggested that the laminae are a seasonal pulse in terrigenous material and a constant diatom supply. More recent authors-(Donegan and Schrader, 1982; Lange and Schimmelmann, 1994; Thunell, 1998) have proposed that the light layers are deposited during the late fall to spring when sediment fluxes are dominated by diatoms and the dark laminae are deposited during the summer to early fall when terrigenous input is high. In general, laminated sediments are believed to be deposited under conditions of little or no oxygen when bioturbation is precluded. Oxygen can only be added to the oceans at the surface by either exchange with the atmosphere or as a by-product of photosynthesis (Duxbury and Duxbury, 1997). Because of this the concentration of oxygen at the surface is high. Below the surface layer, oxygen decreases as animal respiration and the decomposition of organic material remove oxygen (Pederson and Calvert, 1990; Duxbury and Duxbury, 1997; Pilson, 1998). This area below the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 0 surface water is called the oxygen minimum zone and represents the lowest oxygen values with depth. Below this zone, the rate o f removal of oxygen decreases because the population density and the abundance of decaying organic matter decreases. This replenishment of oxygen occurs through the movement of oxygen-rich waters from the surface down to greater depths (Duxbury and Duxbury, 1997; Pilson, 1998). Because o f this the concentration of the oxygen minimum zone varies with age of the water mass (older water masses will have lower oxygen values due to consumption) and the level of primary productivity in the overlying waters (high primary productivity will increase oxygen consumption due to increased organisms and organic matter decay) (Pederson and Calvert, 1990). When oxygen values in the oxygen minimum zone reach 0 ml/1 or close to 0 ml/1, the waters are considered anoxic and can no longer support life (with the exception of anaerobic bacteria). It is at these times in which laminations in sediments will form. Another way anoxia can occur is if replacement of the bottom waters are impeded, such a deep basin with a shallow sill. In this instance, deep water becomes stagnant and all the oxygen is consumed forming an anoxic basin. In this case too, laminations will form where the anoxia zone occurs. Organic Carbon in Sediments A popular belief for the origin of organic carbon-rich sediments and rocks is that they are the result of deposition in anoxic areas. Organic matter is produced by primary productivity from either the overlying photic zone or in adjacent nearshore and estuarine waters, erosion from the contintental shelf sediments, and terrestrial sources, transported either by river discharge or atmospheric transport (Jahnke and Shimmield, 1995). Primary productivity is controlled in the open ocean by nutrient supply to the euphoric zone (Pedersen and Calvert, 1990). A fraction of the organic Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 1 matter produced in the euphotic zone is exported and settles into deeper water. Part of this material is oxidized while settling, part is used as food by benthic organisms, part undergoes further degradation in the sediments, part is exported laterally and the last o f the organic matter is buried (Pedersen and Calvert, 1990; Jahnke and Shimmield, 1995). The importance of these processes varies from place to place depending on the level of primary productivity, the water depth, the rate of sedimentation and the availability of oxidants. In areas where higher production rates make grazing inefficient, more carbon settles to the sea floor than in areas where the production rate is lower (Eppley and Peterson, 1979). The amount of organic carbon in marine sediments depends on the rate of supply, the extent of preservation after burial and the degree of dilution by other sedimentary components. In general, sediments in the open ocean contains less organic carbon than sediments in marginal areas. This distribution can be explained by a combination of the settling flux and transit time for sinking particulate carbon before it reaches the sediment (Pedersen and Calvert, 1990). The margins of the ocean are more productive, so a higher total and export flux of carbon from surface waters is expected. The flux in marginal areas settle through a shallower water column so that oxidative and respiratory losses are less. There is also a significantly larger mass of carbon buried in these areas due to the accumulation rate of carbon relative to the production rate and the bulk sedimentation rate (Pedersen and Calvert, 1990). The dvsaerobic conditions in these waters, however, are not the cause of the high carbon content of the sediments, but are the results of the extremely high productivity in the surface waters and the associated high water column and benthic oxygen demand (Pedersen and Calvert, 1990). The preservation of organic matter in marine sediments depends on the degree to which sediment-dwelling bacteria are able to metabolize the components of deposited organic matter. In the past, the preservation of organic matter in marine sediments Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 2 was thought to be greater in areas of anoxia. In these areas, where there was not enough oxygen to support organisms, sediments remained relatively untouched or laminated due to lack of bioturbation by organisms. This in turn allowed sedimentation to bury the organic carbon and preserve it. However, more recent studies (Jewell and McCarthy, 1971; Kristensen and Blackburn, 1987; Henrichs and Reeburgh, 1987; Pedersen and Calvert, 1990) have discovered that earlier conclusions were not necessarily true. Jewell and McCarthy (1971) demonstrated that the rate of decomposition of algae is roughly the same under oxic and anoxic conditions. Kristensen and Blackwell (1987) went further and found that in some cases the degradation rate of organic matter in shallow-water sediments was slightly higher in anoxic conditions than in oxic conditions. In Henrichs and Reeburgh’s (1987) study of organic matter mineralization, they determined that the rates of mineralization were similar in both oxic and anoxic waters. In most seafloor environments, the majority o f deposited organic carbon is lost from the sediment record by biological remineralized processes (Jahnke and Shimmield, 1995). These processes include remineralization using oxygen, nitrate, and sulfate as oxidants and the oxidation of sulfide and ammonium. Add to this physical processes such as particle input, particle mixing, partical burial and solute pore-water diffusion, it makes for a very complex system with many uncertainties (Jahnke and Shimmield, 1995). Carbonate in Sediments In the present oceans only calcium carbonate forms a significant part of carbonate sediment (Pilson, 1998). Calcium carbonate in sediments is nearly all produced by foraminfera, coccoliths and molluscs. When organisms die their shells either already lie on the ocean surface or sink to the bottom directly or through fecal Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 3 pellets. In oxygenated zones of the ocean, carbonate is readily dissolved because of high biotic demand and waters are undersaturated with respect to carbonate. Other factors effect carbonate precipitation, such as pressure due to increased water depth, pH changes, redox levels, and sulfate reduction (Flocks, 1993; Pilson, 1998). Because of these facts, higher values of carbonate are found in laminated sediments than in bioturbated sediments. Changes in carbonate concentration can change over time by several factors: 1) increasing productivity in surface waters increasing the flux of carbonate components, 2) decreasing detrital flux, which dilutes the marine derived fraction, or 3) decreasing dissolution rates o f the foraminifera/coccoliths tests as they settle through the water column, as a result of water chemistry (Flocks, 1993). Loss of seafloor calcium carbonate is primarily controlled by the saturation state of the overlying bottom water. However, studies performed by Archer (1991) suggest that the remineralization of organic carbon in surface sediments may drive dissolution and influence calcium carbonate preservation. When organic carbon is oxidized, C 02 is released. This C 02 in turn will facilitate calcium carbonate dissolution. When there is no organic carbon rain, there is no metabolic dissolution and all of the deposited calcium carbonate accumulates (Archer, 1991; Jahnke and Shimmield, 1995). However, attempts to verily Archer’s (1991) model have yielded ambiguous results, making attempts to relate changes in the calcium carbonate content of sediments to variations in surface-water processes and sediment input unresolved (Jahnke and Shimmield, 1995). Sediment Fabrics In earlier (and the present) oxygen-related mudrock studies, many geologists and paleontologists struggled to understand oxygen-related mudrock environments, especially black shales environments because of their significance as indicators of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 4 oxygen-deficient environment and in the production of petroleum. Black shales are a subset of mudrocks that are laminated and/or fissile. They are deposited in oxygen-deficient environments and sometimes contain remarkably well-preserved fossil fauna. These fossil faunas exhibit a mixture of planktonic, pseudoplanktonic, nektonic, and benthic life habits. Traditionally, benthic fauna found in black shales have been classified as planktonic, pseudoplanktonic or nektonic because oxygen levels were considered too low to support benthic life. Based on these observations Rhoads and Morse (1971) and later Byers (1977) developed criteria for identifying three oxygen-related biofacies in the stratigraphic record. a) Aerobic Biofacies - oxygen > 1.0 ml/1; abundant bioturbation and fossils b) Dvsaerobic Biofacies- oxygen between 1.0ml/l and 0.1 ml/1; partially bioturbated fabric and poorly calcified benthic fauna c) Anaerobic-Biofacies - oxygen < 0.1ml/l; laminated sediment lacking all benthos This definition reinforced older ideas that benthic fossils found in laminated black shales could not be in situ, but must have been transported from a more oxygenated environment. This definition ran counter to findings of obviously in situ fauna, such as Posidonia radiata and Pseudamyti/oides dubis within laminated black shale (Bottjer and Savrda. 1993). More modem studies of oxygen-deficient black shale have found benthic fauna present in the shale's laminations. From these observations it is clear that the Rhoads-Morse-Byers model is lacking in oxygen deficient environments. Bottjer and Savrda (1993), redefined the Rhoads-Morse-Byers’ Model of oxygen-related biofacies. Two new biofacies were added: the exaerobic biofacies and the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 5 quasi-anaerobic biofacies. These two new biofacies lie between the anaerobic and the dysaerobic biofacies. The Savrda-Bottjer model (Savrda, 1983; Savrda and Bottjer, 1991; Bottjer and Savrda, 1993) is as follows: Aerobic Bio facies - oxygen >1.0 ml/l; bioturbated strata contains diverse assemblages of relatively large, heavily calcified macrobenthic body fossils; trace fossils and ichnofabrics are variable as a function of environmental energy, substrate consistency, etc.. Dysaerobic Biofacies- oxygen between 1.0ml/l and 0.1ml/l; bioturbated strat contains low diversity of relatively small, poorly calcified macrobenthic body fossils or absence of body fossils; diversity, size and depth of penetration of burrows decrease systematically with declining oxygen. Exaerobic Biofacies - oxygen between 1.0ml/l and 0.1ml/l; laminated strata similar to that of the anaerobic or quasi-anaerobic biofacies but contains in situ epibenthic macroinvertebrate body fossils. Quasi-Anaerobic Biofacies - oxygen between 0.1 ml/1 and 0 ml/1; laminated strata contains microbenthic body fossils, but lacking in situ macrobenthic body fossils; transported vertebrates and invertebrates and fecal material mat be common; laminae disrupted slightly by microbioturbation. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 26 Anaerobic Biofacies - oxygen 0 ml/1 or close to Oml/1; well-laminated strata lacking in situ macro and microbenthic fossils and microbioturbation; may contain well-preserved remains of nektonic vertebrates, planktonic, epiplanktonic or other transported invertebrates, and fecal material of planktonic and/or nektonic origin. The exaerobic biofacies is defined as laminated sediments that contain epibenthic macroinvertebrate body fossils. This implies that since oxygen values are so low bioturbation is not apparent, but are high enough to support a refuge from predators which require higher levels of oxygen. The quasi-anaerobic biofacies is defined as laminated sediments containing microbenthic body fossils, but lacking macrobenthic fossils. These laminations can be disturbed slightly by microbioturbation. These microbioturbations produce a “fuzzy” lamina where the sediment within the lamina is disturbed but the lamina is preserved. Around the same time as the Savrda-Bottjer Model was produced, another biofacies model for oxygen-deficient facies in epicontinental seas was designed by Sageman et al. (1991). The purpose of this model was for much the same reasons as the Savrda-Bottjer Model, it represented a way in which to classify black shales by way of physical, chemical and biological characteristics of the benthic zone. Sageman et al. believed that black shales represented long-term stagnation under anoxic conditions with a series of short term oxygenation and sedimentation events that can be seen in stratigraphic units. In the Sageman et al. Model there are two types: a Type I and a Type II. These Types represent two different paleoenvironments. A Type I environment represents an environment which contains a high level o f benthic community diversity and biomass at bottom water oxygen levels between 0.1 and 1.0 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 7 ml/1. In a Type I environment not only are the bottom waters oxygenated, but the uppermost sediment layer as well, allowing for the presence of deposit feeders. The sediment layer can become anoxic due to consumption of oxygen through bacterial decay o f decreasing organic matter, and decreased oxygen supply through stratification of water masses. A Type II environment is one in which physical, chemical, or biological conditions create a sharp boundary at to near the sediment-water interface between anoxic sediments and dysoxic to oxic water column. Because of the anoxic sediments, fauna groups are epifaunal and are most likely adapted to withstand lethal quantities of H2S. These organisms are either anaerobic bacteria or benthos which have developed some form of chemosybiosis. This environment is typically low in diversity and contain bacteria, suspension feeders or bacterial farmers. From these two Types, a biofacies model was designed. This model contained six levels named A - F. Level A - contains well laminated sediment fabrics and no macrofauna. This level represents anoxic levels in the sediments. Level B - contains mono- to paucispecific assemblages composed of oxygen-adapted pioneers. In Type I environments sediments fabrics are slightly disturbed by tiny horizontal or vertical burrows. In a Type II environment sediments are well laminated with a flat clam pioneer. Level C- consists of paucispecific associations of Iow-oxygen pioneers and successors. Type I biofacies may contain nuculiod bivalves and discrete trace fossils. Type II biofacies contain flat clam assemblages with scattered shell island epibonts in well laminated sediments. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 8 Level D - biofacies do not change significantly from level C in Type I environments. Type II represents the first evidence of substrate surface habitability by organisms other than adapted pioneers. Level E and F - these levels represent changes in bottom water oxygen and the redox gradient such that the benthic boundary condition is effectively diminished. Type I and Type II biofacies can resemble each other. Additional observational details can be added to the Savrda-Bottjer oxygen-related mudrock biofacies and Sageman et al. Model based upon research in this study (Figure 9). These observations are based on details observed in x-radiographs of slope sediment in the Gulf. The Exaerobic Biofacies of Savdra-Bottjer can be divided into two exaerobic biofacies. 1. Anaerobic Biofacies - are well laminated with sharp boundaries to layers; no macro- or microbenthic organisms are found; the redox boundary is at the sediment interface. These sediments accumulate where bottom waters contain 0.0 ml/1 and H,S occurs at the sediment interface or in the water column. 2. Quasi-Anaerobic Biofacies - these are well laminated sediments with microbenthic organisms. Laminations may be wavy and/or discontinuous. The redox boundary is millimeters below the interface. Vertebrate bones are found intact. The bottom water oxygen values are projected to be between 0.0 and 0.1 ml/1 (Figure 10). 3 A. Exaerobic-A - sediments are well laminated with microbenthic organisms present. Tiny horizontal and vertical burrows may Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 9 be seen. Lamination can be wavy and/or contain gradational boundaries. Vertebrate bones are usually scattered. Macrobenthic organisms may be found (polychaetes). The bottom water oxygen values are greater than 0.1 ml/1 (Figure 11). 3B. Exaerobic-B - sediments are laminated to semi-laminated with microbenthic organisms present. In situ epibenthic bivalves can be found. Polychaetes can be seen at the surface. Lamination boundaries are blurred and not distinct. Tiny horizontal and/or vertical burrows are present. The bottom water oxygen is between 0.1 and 0.2 ml/1 (Figure 12). 4. Dysaerobic - sediments are homogenous with some indistinct layers. Larger vertical and horizontal burrows are preserved. A diverse macrobenthos can be found at the sediment-water interface and within the sediments. The bottom water oxygen values are greater than 0.2 ml/1 (Figure 13). 5. Aerobic - sediments are homogenous with distinct vertical and horizontal burrows. No apparent sediment layering can be seen. The redox boundary is deep compared to the other biofacies and the bottom water oxygen values are greater than 0.3 ml/1. In the above scheme Anaerobic and Dyaerobic Biofacies are similar to those discussed by the Savrda-Bottjer Model. The new biofacies Exaerobic-B (Figure 12) includes sediment fabrics that are a combination o f both laminated and semi-laminated. Laminations can be distinguished in the sediment but are disturbed and recognizable due to vertical change in sediment color. In other words, sediments Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SEDIMENT MICROFABRIC TYPES o o WELL LAMINATED 1 ____________l _ H2S 1 SEMI-LAM. | K > 4 STRONGLY BIOTURBATED I + 0.1 0.2 >0.3 0 m m s c m s | SEDIMENT-WATER L INTERFACE , * REDOX LEVEL 0.1 0.2 OXYGEN LEVELS ( m l/ l ) >0.3 (after Savrda & Bottjer, 1991 ;I993) Figure 9. Schem atic diagram o f sediment microfabric types. Corresponding bottom water oxygen levels and relative position o f the redox level. OJ o 31 are homogenized, but not to the point that general sedimentation patterns (i.e. more terrigenous input, more diatomaceous input, etc.) are completely erased. In Exaerobic-A Biofacies (Figure 11) laminations can be readily identified but do not always continue horizontally. These laminations do not have sharp boundaries possible due to the effects of microbioturbation at horizontal levels. These laminations are often wavy and may be indicators of the microbial mats, which thrive in these very low oxygen regimes or diatom mats. The next biofacies Quasi-Anaerobic Biofacies (Figure 10) is used to define laminations similar to those in the Exaerobic-A Biofacies, but where the laminations continue throughout the section and contain sharp lamination boundaries. There is no obvious mixing of sediments between lamination boundaries. The last biofacies Anaerobic, represent well developed laminations formed when there is no bioturbation. This lamination contain sharp boundaries and no presence of any type of in- or epi-faunal organisms. For the purpose of this paper, sediments will be labeled by the numbers given for each type of biofacies in the new model. These characteristics will be used to determine oxygen biofacies patterns and used as proxies of bottom oxygen levels in the Gulf of California. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Core CP 56 cm 65.5 cm SEDIMENT MICROFABRIC TYPE 2 Figure 10. Picture from core CP showing sediment microfabric type 2. In this type of microfabric laminations are well defined and continuous. to Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Core CP iJlt - ; . - V ' - '?r 139 cm 147 cm SEDIMENT MICROFABRIC TYPE 3 A Figure 11 . Picture shows sediment microfabric type 3A. This sediment type is laminated, however, laminations are wavy and not always continuous. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. CORE CP ? v - - ^ ■ *•:■ >.., . . ■ > • } • . v l " " ■ . • * v > '■ y^'V v 'M c ^ : }:: ^ • : K -rS'V- 156 cm 162.5 cm SEDIMENT MICROFABRIC TYPE 3B Figure 12. Picture from core CP showing sediment microfabric type 3B. This sediment type contains poorly formed laminations with blurred lamination boundaries. OJ 3 5 Q LU (/) C L Q- O O Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 13. Picture fro m core C P shows sediment microfabric type i n top o f core. This sediment type i s bioturbated. 3 6 CHAPTER 2 Study Methods Field Methods Sediment Core Sampling Sediment cores were taken using various coring devices includeing Kasten, gravity and a modified Reinecke giant box cores. On board ship at the time of collection sedimentary structures (i.e. sediment color, smell, fabrics, etc.) were observed, organisms recorded, and the cores prepared for storage. After collection, cores were kept in cold storage to preserve sediments and prevent unwanted microbial growth. Kasten and gravity cores were up to 200 cm in length. Box core samples were generally between 18 and 60 cm in length. Cores were taken during two research cruises aboard the Mexican vessel El Puma. The first cruise occurred during the summer of 1994 and was labeled as Paleo-VTI. All cores taken from this cruise and the following Paleo-Vm (1996) were label by location first and site second, for example the El Coyote location is labeled C and sites where cores were taken were given A-Z labels, so that these cores were called CA, CB, CC etc.. In total, 13 cores from the El Coyote location and 7 from the Santa Rosalia location were examined for this research. The third cruise, Paleo-IX, was held during the summer of 1998. AH cores taken on this cruise were labeled by site alone, for example, core from the El Coyote area were labeled 9 - 30 in order of site progression. Due to problems with cores taken from the El Coyote area, only the Paleo-IX cores taken from the Santa Rosalia area will be used for this paper. All cores were sliced vertically for slab x-radiographs. The remainder of the cores was cut horizontally either every centimeter or every 2 cm. These core cuts Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3 7 were placed into cold storage until needed. The horizontal slabs were used for x-radiographs and/or geochemical analyses. Laboratory Methods The analytical results were obtained as part of several collaboration research projects. The geochemical analyses, i.e. Carbonate, Silica, etc., were conducted by myself, Kristi Rikansrud, and Dr. Donn Gorsline. Data collected from Rikansrud and Gorsline were used for downcore for analyses and dating. Analyses conducted by myself were made at intervals where sediment fabrics changed from type 2 to 4 or vice versa. This was done in order to determine any geochemical patterns and/or relationships between the different biofacies present in the cores. Most of the geochemical analyses were conducted on the cores FF and CP. Statistical analysis were performed for all data collected using a Macintosh Excel program or an IBM Microsoft Works spreadsheet. Statistical analyses used for geochemical data and microbiofacies indices were mean, median, standard deviation and z- or t-test to determine any correlations between samples within locations and to locations. Both t- and z-tests were computed at a significancy level of 0.05. All geochemical and microbiofacies data were plotted using Kalidograph computer program for graphs. Plots were used as visual comparison for data collected. Carbonate and Organic Carbon Analyses For carbonate, total carbon and organic carbon percentages were determined for core FF from Santa Rosalia and CP from El Coyote. Carbonate percentages were also determined for core CB in order to compare with carbonate values for the same depth locations in the Alfonso Basin. For CP, carbonate values were determined for Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3 8 every centimeter up to 99.5 cm by Ivette Granados, thereafter values were taken at every 10 cm except in a few special intervals which were sampled every centimeter. Samples for total carbon and organic carbon in core CP were collected at ten centimeters intervals except in interval points of special interest which were sampled every centimeter. In core CB, carbonate samples were collected; value result from the analysis were collected for at ten centimeters intervals to gain an overall profile. In core FF, carbonate, total carbon and organic carbon samples, were taken at every -10 centimeters except for special intervals which were sampled every 2 centimeters. Carbonate and total carbon were determined by a LECO Analysis. Samples were dried in a laboratory oven over night and powered the next day. For both total carbon and carbonate analyses, 0.5 g were used for each sample. For the total carbon analysis, samples were placed in a crucible with one part tin and four parts iron. The crucible was then placed in the LECO furnace and burned at high temperatures to ensure melting. During the burning all carbon, both inorganic and organic is converted to C 02 gas and then flushed into the LECO apparatus. The gas is then placed into a reservoir where the C 02 is absorbed by KOH. When absorption is complete, the gas is delivered to the LECO burette where the volume of converted C02 is read. Data was then read from the LECO burette and entered into the following formula: % Total Carbon = (Factor)(Burette Reading)(Scale/Weight of Sample) where Factor is the corrected temperature-pressure factor and Scale is the burette scale of 1 g.. For the Carbonate Analysis, preweighed samples were placed in test tubes. The test tubes were attached to a Kolpack-Bell Attachment, 5 ml of HC1 acid was added to each sample and heated with a Bunsen Burner. The HCI reacts with the sample so that only the inorganic carbon is converted into C 02. The CO, from the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3 9 acid burning flows into the LECO burette and as with the Total Carbon Analysis the CO, is absorbed by the KOH and the volume of converted CO, read from the burette. The reading is recorded and placed into the following formula %Carbonate = %Inorganic Carbon x 8.33 where the %Inorganic Carbon is the same formula as the previous %Total Carbon formula and 8.33 is a constant. The constant is derived from the ratio of the molecular weights of carbon to carbonate. molecular weight of C / molecular weight of CaC03 = 12/(40+ 12+ (3 * 18)) = 8.33 Using the two previous formulas the organic carbon can be determined through a simple subtraction. %Organic Carbon = %Total Carbon - %Inorganic Carbon Silica Analyses Silica content was determined for samples from cores CP and FF and used to compare down core silica at the two locations and between the two locations. In core CP samples were taken at 10 cm intervals and at special points of interest at every centimeter. Core FF had silica data taken from focus points at 2 cm intervals. Amorphous silica was measured to gain the weight percents of biogenic silica in order to determine possible paleoproductivity in the Gulf at the two locations. Silica Analysis was performed using a two-fold Na2 C 03 leaching method which allows amorphous silica to be extracted from dry sediment samples. The first part of the experiment is the leaching water bath sequence and the second part is the analysis with the Colorimeteric Photospectometer. For the first part of the analysis approximately 60 mg of dried and powered sediment sample was leached with 50 ml Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 40 of 5% Na2C 0 3 in a capped plastic centrifuge tube. These solutions were placed in an 80 degree C water bath and shaken every 30 minutes. The leaching was monitored every hour for 4 hours by removal of the tubes from the water bath, centrifuging it immediately for 4 minutes at approximately 2000 rpm, withdrawing 0.2 ml with a pipette, and diluting this aliquot with 1.8 ml of ?% HC1 and deionized water. Standards were made using 5% Na2 C 0 3 and were similarly diluted. Samples were then placed in a cool dark area overnight. The following day 0.8ml of a molybdate solution (4.0 g Ammonium molybdate, 300ml deionized water and 24 ml of 6 N hydrochloride acid) and 1.2 ml of a reducing reagent were added to each sample. The reducing reagent consisted of 50 ml of methylaminophenol sulfate/sulfide solution (3 g sodium sulfite, 250 ml deionized water, and 5 g of 4-methylaminophenol sulfate filtered through a U1 Whatman filter paper), 30 ml of oxalic acid solution (25 g of oxalic acid dehydrate and 250 ml deionized water), 30 ml of sulfuric acid solution (equal parts concentrated sulfuric acid and deionized water), and 40 ml of deionized water. The samples were then placed in a cool dark area and let stand for about 2 hours. This process allows the seawater in the sample to react with the molybdate solution which allows the formation of silicomolybdate, phosphomolybdate and arsenomolybdate complexes. The reducing reagent is then added which reduces the silicomolybdate complex to give a blue reduction compound and decomposes the other two complexes. This way the resulting solution can be measured for silica. After 2 hours, the samples are measured with a Colorimetric/Spectrophotometer at 800nm wavelength. These measurements are then used in an x-y plot of weight percent silica released vs. time to determine % silica weight in each original sample. The amount of amorphous silica in the samples was approximated using methods o f Boucher (1984). This method assumes that amorphous silica dissolves mostly within the first two hours of leaching and that increases in dissolved silica Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 1 detected after this time are due to the release of silica from clays (Boucher, 1984). Boucher (1984) showed that silica releases from clays in a linear fashion in 80 degrees C, 5% Na2 C03 solution. At the start of leaching, no silica from clays or biogenous silica should be in solution. Because of this, a best fit line drawn through the linear portion of a weight percent silica released vs. time plot should have a y-intercept at the weight percent of amorphous silica originally present in the sample. Macrobenthic Organism Analyses Marcobenthic organisms were collected at 4 locations in Alfonso Basin and three locations on the slope of Santa Rosalia. These locations were at different depths along a transect; from outside the basin to the center of the basin in Alfonso and from ~1000m to ~200m up slope at Santa Rosalia. Macrobenthic organisms were collected from the tops of box cores at the time of collection. Samples were taken using a 4 in x 4 in x 1 cm metal cube and washed through sieves at the site to ensure organisms were alive at the time of collection. All organisms found were recorded and placed in glass jars filled with methanol for preservation. Samples were taken back to the laboratory where they were cataloged by family type, i.e. polychaete, crustacean, etc., and width and lengths were measured. These organisms were then compared with each other for differences in locations and type of sediment. X -radipgraph Analyses X-radiographs were taken of all cores collected from cruises Paleo-VII, Paleo-VIII and Paleo-IX. Core samples were extruded and slabbed in vertical cross-sections, and in some cases horizontal cross-sections 1 -2 cm in width were made. The vertical and horizontal cross-sections were then X-rayed using the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 2 Penetrex Industrial X-ray machine at the University of Southern California Earth Science Building. Length o f time varied from core sample to core sample depending on thickness and sediment texture of the cores. These x-radiographs were analyzed for presence of bioturbation and laminations. For each core x-radiograph, sediment structures were identified, measured and recorded. These observations were then used to compare cores and patterns in lamination and bioturbation. Identification of laminations were broken down into five oxygen-related biofacies. These biofacies are based on the modified Savdra-Bottjer Biofacies Model (1991) discussed in the previous section. To make labeling clearer and simpler these groups were given index or order of magnitude numbers. The Aerobic and Dysaerobic Biofacies are labeled as 5 and 4, respectively for non-laminated fabrics. Exaerobic Biofacies are considered a 2, and the Quasi-Anaerobic and Anaerobic Biofacies are labeled 3 and 4 respectively. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 3 4 3 RESULTS Carbonate and Organic Carbon Analyses Carbonate values ranged from 0% to 22.9% (Appendices 1 and 2). For core CP and FF, carbonate values were grouped by sediment biofacies. For core CP, the values ranged from 0% to 22.9% with the highest values occurring in type 2 and the lowest occurring in type 3B. For all sediment microfabrics in core CP, the mean for carbonate was 8.75 (Table 3). For the sediment microfabrics the highest carbonate mean was in type 2 and the lowest was in type 3B. Comparison t- z-tests for carbonate in core CP at a significancy level of 0.05 indicated that there was a significant difference between all sediment types except between types 3B and 3A (Table 2). Table 2. T-test and z-test values for Core CP. Sediment Sediment ;t- or z-values i ta/2[df] or za/2 Factor 1 Microfabrics; 1at 0.05 significance iOpal Silica 4 and 3B 0.5461 2.052 4 and 3A -0.226 i 1.96 4 and 2 -0.239! 2.212 :3B and 3A 0.639! 1.96 3B and 2 -0.483 1 2.16 3A and 2 -0.068 * 2.086 ! Total Organic Carbon 4 and 3B -1.765! 2.11 4 and 3A -0.166 i 2.08 3B and 3A -1.231 ! 2.069 Carbonate 4 and 3B 3.012! 1.96 4 and 3A 3.411 : 1.96 4 and 2 -2.572; 1.96 3B and 3A 0.172; 1.96 3B and 2 -4.597! 1.96 3A and 2 -4.826! 1.96 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 3. Calculated Statistics for Core CP. Statisitics For Sediment Microfabrics in CP: %Opal Weight 4 %Opal Weight 3B %Opal Weight 3A %Opal Weight 2 Minimum 0.634 0.62699997 0 .47099999 1.0420001 Maximum 2.875 2.7249999 4.3769999 1.881 Sum 21.824069 14.803728 24.098513 2.9230001 Points 1 6 12 17 2 Mean 1.3640043 1.233644 1.4175596 1.4615 Median 1.1317608 0.92693585 1.1257157 1.4615 rvs 1.4932451 1.4117819 1.7094903 1.5205139 Std Deviation 0.62760764 0.71700186 0.9848538 0.59326258 Variance 0.39389135 0.51409166 0 .9 6 9 9 3 7 0.35196049 Std Error 0.15690191 0.20698061 0.23886213 0.41949999 Skewness 0.93840226 1.2881149 1.8873072 0 Kurtos/s 0.025806174 0.17233547 3 .1 1 2 9 6 8 4 -2 Total Carbon 4 Total Carbon 3B Total Carbon 3A Total Carbon 2 Minimum 3.9200001 6.2540002 4.2199998 Maximum 7.7399998 7.4689999 8.3500004 Sum 67.775 53.985 75.366 Points 11 8 12 0 Mean 6.1613636 6.748125 6.2805 Median 6.1630001 6.6819999 6.2855 FM S 6.2347111 6.757418 6.3 9 2 6 4 6 4 Std Deviation 1.0000716 0.37873179 1 .2451716 Variance 1.0001432 0.14343777 1.5504524 Std Error 0.30153294 0.13390191 0.35 9 4 5 0 0 9 Skewness -0.77494723 0.73203419 0 .023947126 Kurtosis 0.65071851 -0.22745407 -0.50845841 %Organic Carbon 4 %Organic Carbon %Organic Carbon 3A %Organic 2 38 Minimum 2 .8399999 4.7579999 2.9300001 Maximum 6.3800001 6.77 7.3600001 Sum 55.102 45.596 61.073 Points 11 8 12 Mean 5 .0092727 5.6995 5.0 8 9 4 1 6 7 Median 5.0819998 5.7804999 4.8110001 R M S 5 .0947063 5.7273219 5 .240168 Std Deviation 0.97444381 0.60277073 1.3033658 Variance 0.94954074 0.36333256 1.6987625 Std Error 0.29380586 0.21311164 0.37624931 Skewness -0.78590258 0.20488812 0.15524549 Kurtosis 0.55809933 -0.31208161 -0.50419941 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 3 Cont.. Calculated Statistics for Core CP. %Carbonate 4 %Carbonate 3B %Carbonate 3A %Carbonate 2 Minimum 6.2199998 0 2.0599999 3.1300001 Maximum 14.265 16.290001 15.52 22.9 Sum 164.592 287.343 546.403 162.17 Points 17 36 66 14 Mean 9.6818824 7.98175 8.2788333 11.583571 Median 9.4700003 6.6949999 8.29 8.9699998 RM S 9.8934807 9.0268125 8.8021317 12.914272 Std Deviation 2.0978554 4.275847 3.0126327 5.9251103 Variance 4.4009971 18.282868 9.0759561 35.106932 Std Error 0.50880466 0.71264117 0.37082946 1.5835523 Skewness 0.58053653 0.31907133 -0.21448151 0.71510067 Kurtosis -0.06568193 -0.7948271 -0.43589677 -0.68335628 Statistics For Entire Core CP: Core Depth (cm) %Total Carbon %Carbonate %Organic Carbon Minimum 0.5 3.9200001 0 2.8399999 Maximum 204.5 8.3500004 22.9 7.3600001 Sum 16316.5 197.126 1160.508 161.771 Points 185 31 133 31 Mean 88.197297 6.3589032 8.7256241 5.2184193 Median 76.5 6.335 8.474 5.2340002 R M S 105.48237 6.4339838 9.5168197 5.3202183 Std Deviation 58.016913 0.99625008 3.8134874 1.0528928 Variance 3365.9622 0.99251423 14.542686 1.1085832 Std Error 4.2654883 0.1789318 0.3306713 0.18910513 Skewness 0.34131178 -0.51498919 0.63710448 -0.34180102 Kurtosis -1.1220313 0.64055441 1.3385324 0.27365187 Core Fabric %Opal Weight %Fisn Bones Minimum 2 0.47099999 0.5 Maximum 4 4.3769999 20 Sum 593 63.64931 95.5 Points 185 47 28 Mean 3.2054054 1.3542406 3.4107143 Median 3 1.108 2.5 FM S 3.2511952 1.5567152 5.3859937 Std Deviation 0.54520935 0.77602031 4.2449394 Variance 0.29725323 0.60220752 18.019511 Std Error 0.040084588 0.1131942 0.80221814 Skewness -0.59036253 1.7646106 2.4470237 Kurtosis 0.25443198 3.5795244 6.5255579 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 6 In core FF, values ranged from 6.2% to 12.8% with the highest occurring in type 2 and the lowest in type 3 A. No data was collected for biofacies 4 in core FF, instead core top values in core FG and IX-63 were used (8.3% and 7.1% respectively). For all sediment microfabric types in core FF, the mean value for %carbonate was 8.9844 (Table 5). For the sediment types the highest mean values were found in type 2 and the lowest were found in type 3B. Comparison t- and z-tests of the different sediment microfabric types in core FF showed at significance level of 0.05 there was no difference (Table 4). Table 4. T-test values for core FF. Sediment Sediment t- or z-values ta/2rdfl orza/2 Factor 1 Microfabrics at 0.05 significance: iOpal Silica 3B and 3A 2.356 2.262 i 3B and 2 -0.135 2.571 i :3A and 2 -1.634 2.447 i 1 1 Total Organic Carbon 4 and 3B -2.638 2.2281 4 and 3A -1.691 2.131 i 4 and 2 -2.599 2.447! !3B and 3A 0.864 2.069! •3B and 2 0.319 2.145 i :3A and 2 -0.436 2.093! 1 Carbonate 4 and 3B -0.8351 2 .2 2 8 ‘ 4 and 3A 0.706! 2.131 i 4 and 2 -1.529! I 3B and 3A 2.2451 2.0691 3B and 2 -0.525! 2.131 ; 3A and 2 -2.242! 2.086! In both cores, biofacies 2 tended to have the highest carbonate compared to the other biofacies. By comparison, core CP had higher carbonate content than core FF. A comparison t-tests of sediment microfabric types between core FF and CP showed that there were significant differences for type 3 A at a significance level 0.05. Types 3B and 2 showed no significant diferences (Table 6). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 5. Calculated Statistics for Core FF Statistics For Sediment Microfabrics: %Opal Weight 4 %Opal Weight 3B %Opal Weight 3A %Opal Weight 2 Minimum 9.1899004 4.6869001 10.001 Maximum 13.877 13.46 12.219 Sum 54.552401 54.197448 22.22 Points 0 5 7 2 Mean 10.91048 7.7424926 11.11 Median 10.581 5.9768801 11.11 FM S 11.029175 8.4 1 1 9 5 3 7 11.165213 Std Deviation 1.8042025 3.5520749 1.5683625 Variance 3.2551465 12.617236 2.4597608 Std Error 0.80686387 1.3425581 1.1089997 Skewness 0.94132293 0 .8 2 2 3 1 6 3 2 0 Kurtosis -0.41950664 -1.0590629 -2 %Organic Carbon 4 %Organic Carbon 3B %Organic Carbon 3A %Organic Carbon 2 Minimum 2.1270001 1.74 2.312 Maximum 3.881 3.95 3.54 Sum 28.404 39.485 19.822 Points 0 10 15 7 Mean 2.8404 2.6 3 2 3 3 3 3 2.8317143 Median 2.7460001 2.7780001 2.9000001 FM S 2.8813686 2.7030531 2.8648023 Std Deviation 0.51035133 0 .6 3 5 8 2 1 0 5 0.46893558 Variance 0.26045848 0.40426841 0.21990057 Std Error 0.16138726 0 .16416829 0.17724099 Skewness 0.64863813 0 .33681509 0.25148873 Kurtosis -0.19697441 -0 .79561642 -1.2447701 %Carbonate 4 %Carbonate 3B %Carbonate 3A %Carbonate 2 Minimum 6.8179998 6.1500001 6.2800002 Maximum 11.21 10.571 12.84 Sum 87.574999 135.369 64.558 Points 0 10 15 7 Mean 8.7574999 9.0246 9.2225714 Median 8.7724996 9 .4 5 1 0 0 0 2 8.9399996 R M S 8.9048398 9 .1310806 9.3945079 Std Deviation 1.7004467 1.4392063 1.9324716 Variance 2.891519 2 .0713149 3.7344463 Std Error 0.53772846 0 .37160148 0.73040559 Skewness 0.15419813 -0 .85913787 0.54111146 Kurtosis -1.4561051 -0 .30146335 0.43454379 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 5 Cont. Calculated Statistics for Core FF Statistics For Entire Core FF: Core Depth (in cm) %Carbonate Core Fabric % Organic C Minimum 0 6.1500001 2 1.74 Maximum 186 12.84 4 3-95 Sum 6349 287 .5 0 2 217 87.711 Points 75 32 75 3 2 Mean 84.653333 8.9844375 2.8933333 2.7409687 Median 80 9.0474997 3 2.7870001 FM S 102.12884 9.119705 2.9495762 2.7954759 Std Deviation 57.517152 1.5899372 0.57711616 0.55813114 Variance 3308.2228 2.5279005 0.33306306 0.31151037 Std Error 6.6415087 0.28106385 0.066639634 0.098664579 Skewness 0.34699703 -0.038421435 -0.47930631 0.23768448 Kurtosis -1.2211357 -0.25186152 -0.8340065 -0.55367576 %Opal Weight Minimum Maximum Sum Points Mean Median R M S Std Deviation Variance Std Error Skewness Kurtosis 4.6869001 13.877 130.97007 14 9.3550048 9.9242501 9.8302374 3.1334958 9.8187959 0.83746198 -0.17570623 -1.287204 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 9 Table 6. T-test and z-test values for Cores CP and FF comparisons. Sediment Sediment t- or z-values ta/2[df] or za/2 Factor : Microfabrics at 0.05 significance iOpal Silica 3B -9.179 2.16 !3A -7.98! 2.074 ! Total Organic Carbon ;3B 10.906 i 2.12 :3A 6.701 : 2.056 Carbonate :3B -1.025! 1.96 :3A 3.935 I 1.96 2 1.016 i 2.093 Organic carbon percentages ranged from 1.7% to 7.4% for all cores. In core CP organic carbon percentages ranged from 2.8% to 7.4% based on 31 data points. Type 3 A had the highest values and type 4 had the lowest. No values were taken at biofacies 2 sites. For all sediment microfabrics, the mean for organic carbon in core CP was 5.218 (Table 3). For the sediment microfabrics type 3B had the highest mean and type 4 had the lowest. Comparison z- and t-tests of sediment microfabrics at a significance level of 0.05 showed that for sediment microfabrics there are no significant differences (Table 2). In core FF organic carbon percentages ranged from 1.7% to 3.9% (based on a total of 32 data points) with highest and lowest values occuring in type 3 A. No values were taken at biofacies 4 in core FF, instead core top values were taken from cores FG and EX-63, 1.9% and 1.8% respectively. For organic carbon in core FF, all sediment microfabric types had a mean of 2.7409 (Table 5). For individual sediment types, the highest organic carbon was in type 3B and lowest was in 3A. The comparison z- and t-tests of organic carbon in core FF showed that at a significance level of 0.05 there is a significant difference between sediment types 4 and 3B and 4 and 2 (Table 4). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5 0 Overall, organic carbon percentages were the highest in biofacies 3A in both cores, with core CP tending to be higher in organic carbon percentages than FF. Comparison t-tests for sediment types between cores CP and FF showed that at a significance level of 0.05 there were no significant differences (Table 6). Silica Analyses Silica content was determined for cores CP and FF (Appendices 1 and 2). Overall range in silica weight percentage was 0.5% to 13.9%. In core CP the silica weight percentage ranged from 0.5% to 4.4%. Both the highest and lowest silica weight values were in type 3 A. In core CP, the silica weight percenage for all sediment types had a mean of 1.354 (Table 3). Statistics for silica weight percentage for sediment microfabrics indicated that sediment type 2 had the highest mean and median and type 3B had the lowest. Comparison t- and z-tests for the sediment microfabrics types showed that at a significance level of 0.05 microfabrics were not significantly different (Table 2). In core FF, the silica weight percentage ranged from 4.7% to 13.9% with the highest values occurring in type 3B and the lowest occurring in type 3A. For all sediment microfabric types in core FF, the mean of the silica weight percentage was 9.355 (Table 5). For individual sediment microfabrics, the highest mean and median occurred in type 2 and the lowest in type 3 A. Comparison z- and t-tests showed that for sediment microfabric types all types, except between types 3B and 3A, indicated no significant differences at a significance level of 0.05 (Table 4). A comparison of sediment types shows that in core FF silica weight percentages were highest in type 3B, whereas core CP shows that the silica weight percentages were highest in type 3 A. Of the two cores, FF demonstrated much higher silica weight percentages than CP. The lowest value in FF is still higher than the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 51 highest value in CP. Comparison t-test for sediment types between cores CP and FF showed no significant differences (Table 6). M acrobenthic Organism Analyses Alfonso Basin/La Paz Basin In the Alfonso and La Paz Basin area, samples were collected at four locations (Table 1 and 7 and Figure 3). At station 9 in the La Paz Basin at a depth of 890 m only one tube of a tube worm and a few small polychaetes were found. The small polychaetes were red in color and about a millimeter in diameter and between one and two centimeters in length. None of the polychaetes from this location survived transportation back to the laboratory (it is believed they disintegrated during transport). Station 22 in the Alfonso Basin is located on the sill at a depth o f 275 m. At this station only a tube of a tube worm and a few polychaetes were found. This area looked much the same as the La Paz Basin even though it is located at a shallower depth. Station 24, at a depth of 395 m, is close to the center part o f the Alfonso Basin. This location contained two different types o f polychaetes types A and B, crustaceans and a few gastropods. Not found in samples transported to the laboratory, but recorded from the box core were a few small gastropods and an orange film on the surface of the core. The orange film on the surface of the box core is believed to be a species of Beggiotoa sp.. Another observations of the box core at this site was that it produced a very strong sulfur smell. Station 25 is located at the center of the Alfonso Basin at a depth o f420 m. At this station two polychaete types were found. The first type was the same as those found in station 24 labeled polychaete A. The second type was something different. The second type labeled polychaete C was a small polychaete about 1 mm in width and 2 cm long. This polychaete contained many detrital-like tentacles located at the head of the organism. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 7. Macrobenthic Organisms in the Gulf of California Alfonso Basin Santa Rosalia Location_ La Paz Basin Station ~9 22 24 25 62 63 64 Depth Found Organism Number of Notes Type Organisms 890 surface - 1cm Tube Worm Tube 1 surface -1 cm other polychaetes were seen at time of samolinq 275 surface -1 cm Tube Worm Tube " T .' J j however none survived transport/storage 395 surface - 1cm Polychaete A ....... 7 1 mm wide, 1-2 cm long surface : 1cm surface -1 cm surface Polychaete B Crustacean gastropods _______ J. .......2 3 mm wide, 16 cm long; tube casing attached________ one five mm,. the other 3mm a few small gastropds were seen at time of sampling_ _ 420 surface - 1cm Polychaete A 25 1 mm wide, 1-2 cm long surface -1 cm PolychaeteC____ ............... 1 1 mm wide, 2 cm long; contains many tentacles? 1030 30 cm worm _ soft pink gelatin-like, with tentacles at mouth surface small polychaetes and few bivalves seen at time 30 cm bivalve 630 surface - 1cm Brittle Stars 18 surface -1 cm Tube Worm Tube 1 6 mm wide, at least 7 cm long surface - 1cm Leptopectin Shells 6 only half shells found surface polychaetes and bivalves were seen at time of sampling however none survived transport/storage 265 surface - 1cm Polychaetes A -30 pieces of polycheates make it hard to determine actual numbers surface - 1cm Tube Worm Tube/ 1 4 mm wide, made out of clay/mud surface -1 cm Tube Worm Tube E 1 3 mm wide, made out of shells and sand surface - 1cm Crustacean 4 one 7 mm long, the rest 3-4mm long unknown Polychaete D 1 only top of worm saved 3cm; tentacles at mouth segmented, black and yellow worm-like body U l N J 5 3 Santa Rosalia Three locations were sampled for macrobenthic organisms at the Santa Rosalia (Figure 4 and Tables 1 and 7). At Station 62, polychaetes, bivalves and three worm-like organisms were found. The worm-like organisms pink and sac-like with tentacles located at the head. They were found 30 cm below the surface of the sediment and were covered with a slimy film. A few bivalves were recorded on the surface o f the core at the time of collection and one was found later in the laboratory at about 30 centimeters below the sediment surface. This bivalve was believed to be alive at the time of collection because it is stained with Rose Bengal, which reacts to living tissue. The polychaetes were few in number and only recorded at time of collection, none survived transportation to the laboratory. At Station 63, ophiuroids, leptopectins, bivalves and polychaetes were found. All ophiuroids were yellowish brown in color and found on the top of the sediment. There was one tube worm tube found with no resident. The polychaetes were seen at the time of sampling but did not survive transportation back to the laboratory. Six leptopectins were found in the top centimeter of the core and several more were seen at various depths within the core itself. Bivalves were also seen in surface sediments at the time of collection, but none were found in samples brought back to the laboratory. At Station 64, polychaetes, various tube worm tubes, and crustaceans were found. There were two types of polychaetes found, the general type A which is found just about everywhere in the Gulf (as seen in this sampling) and a second type labeled type D. Polychaete type D was found on the outside of the box core so exact depth of habitat of this specimen is unknown. Also only the top 3 cm of this specimen was found, the other half possibly sliced by the box core itself. This polychaete had a yellow head with tentacles surrounding the mouth, and a black segmented body. Two types of worm tubing was found at this site. There were four crustaceans found, one was 7 mm long and rest Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5 4 were 3 -4 mm long. These crustaceans looked similar to the ones found in the Alfonso Basin. X-Radiograph Analyses X-radiographs were examined in negative and positive prints and sediment microfabrics were identified using the modified Savrda-Bottjer Model (Appendix 3). Sediments in both the Alfonso Basin and off Santa Rosalia contain various exhibit varieties in sediment microfabric down-core. At present, bioturbated sediments, type 4 or 5 (dysaerobic to aerobic) occur at the surface in both locations and contained various bivalve and gastropod shells. Many more contained both vertical and horizontal burrows with some mm scale ones. Wavy laminations were common and frequent in ares were bottom water oxygen levels reached below 0.2 ml/1. Potential Errors In the carbonate, TOC and opal silica analyses there is a potential error in that many of the sediment micro fabrics boundaries are gradual rather than sharp, abrupt changes and sampling at intervals of 1 cm to 2 cm may include more than one sediment microfabric type. This potential mixing probably' reduces the distinction between sediment microfabric types. In the opal silica analyses there is a potential error if the 80 degree bath is too hot or too cold. A too hot bath will lower final opal silica values and a too low temperature bath may raise the final opal silica values. Finally there is always a potential for human error which is not always apparent. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5 5 CHAPTER 4 Discussion Geochemical Data Core CP Geochemical data (i.e. carbonate, total organic carbon and opal silica) from core CP were compared to sediment microfabrics (Figure 14). As seen on figure 14, carbonate values appear to correlate with sediment mfcrofabrics, with higher values corresponding to more laminated sediments and low values with less laminated to bioturbated sediment microfabrics. Total organic carbon does not appear to correlate with either sediment microfabrics or carbonate, however down core patterns in TOC seems to correlate with silica opal (Figure 14). Cross-correlation scatter plots showed that there is no apparent correlation between TOC and carbonate (Figure 15). Scatter plot of carbonate and silica opal also revealed no apparent correlation. TOC versus silica opal, however, shows a distinct correlation of increasing silica opal with increasing TOC. Implications o f both Figure 14 and 15 are discussed in further detail below. Carbonate For the carbonate in core CP, the highest mean value was found in sediment microfabric type 2 and the lowest in type 3B and the t- and z-tests indicated that sediment microfabric types 4 and 2 are significantly different from sediment microfabrics 3B and 3A. This pattern can also be seen in Figure 14. It implies that carbonate values change significantly as bottom oxygen levels change from 0.1ml/l to Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CORECPDATA pjBJ p f l l l | I I I I | i i i I i l l rm 1111111111 1 n 11 ii ii i m 111111 1 1 il.i.i i 11 n u 1 . S 2 2 . 5 3 3 . 5 4 t l S 1 I S 2 0 2 3 4 5 6 7 B T 1 2 Scdim cntM icrofabric Carbonate TotalO rganicCarbon OpaEilica Rgure 14. Comparison of sediment microfabrics, carbonate, total oragnic carbon, and opal silica, plotted against core depth in core CP. ON Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. COMPARISON OF GEOCHEMICAL DATA FROM CORE CP C o i. ra _ O 6 o 'E ( 0 E » 5 o 1 0 o 4 H 3 2 TOC vs Carbonate l i i i % □ ‘ I v I I | I I I I * 0 □ □ 0 #4 Sedim ents q ff3B Sediments o #3A Sedim ents a #2 Sedim ents 0 5 10 15 2 0 2 5 Carbonate Carbonate v s Opal Silica < u ( 0 c ( 0 O - 5 0 5 oO" 1 0 1 5 20 25 0 1 2 4 3 5 Opal Silica TOC vs Opal Silica c o •£ n > O o 'E ( 0 o 3 2 □ a □ # 0 .1111 > °tL n ■ 11111111 ■ 1 1 1 1 1 i.i 0 1 2 3 4 5 Opal Silica Figure 15. Comparison Scatter Plots of Geochemical Data From Core CP. Total Organic Carbon vs. Carbonate, Carbonate vs. Opal Silica and Total Organic Carbon vs. Opal Silica were com pared to determ ine any correlating characterisitics. ^ 58 l.Oml/L This also indicates that the relationship of carbonate to bottom oxygen values found within the Gulf are similarto other carbonate models (Flocks, 1993; Pilson, 1998). In general, higher values of carbonate are expected in sediments representing anoxic conditions. Organic Carbon The mean, median and standard deviation for organic carbon in the Alfonso Basin shows that like the opal silica there is little difference in the percentage of organic carbon between the sediment fabric types (Table 3 and Figure 14). This is supported by the t-tests performed on the sediment microfabrics (Table 2). On average, laminated and non-laminated sediment have similar organic carbon content suggesting that geochemical breakdown of organic carbon in the Alfonso Basin may is not consistent over time. Preservation of the organic carbon is probably the key. According to Zobell (1942), bacteria contribute to calcium carbonate dissolution by producing acid during decomposition of organic matter. However, Grant (1991) showed that Beggiatoa in Santa Monica Basin is found in sediments with increased organic carbon, suggesting that Beggiatoa sp. might be chemolithotropic and introduce a substantial amount of organic carbon to anaerobic sediments. If Beggiatoa is present in the Gulf it would help explain why there is no difference between organic carbon in 3B sediments and 2 sediment types, however this does not explain differences in 3A. The only variable that correlates with organic carbon is opal silica (Figures 14 and 15). According to Figures 14 and 15, organic carbon has a positive correlation with opal silica . This could be attributed to one of two factor: 1) Organic carbon is controlled by primary productivity, thus correlates with opal silica, and 2) both organic carbon and opal silica are affected by the same dissolution. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5 9 The most important process controlling the organic carbon content in the sediments of the Gulf may be the rate of dissolution/decomposition before and after burial. If the rate of dissolution and decomposition were known it would be possible to determine amount of organic carbon before decomposition. However, there is no known organic carbon model for the Alfonso Basin, making it very difficult to determine the amount of organic carbon that is produced by current primary productivity, settling to the bottom, being recycled and being buried. It is possible that these unknown factors can explain the variations in organic carbon between sediment types. Opal Silica Statistical analysis of the opal silica in core CP indicates that there is little difference between the sediment microfabrics. The range between the highest and the lowest mean values (1.47% vs. 1.23%) is small and the t- and z-test indicate that these differences are not statistically significant (Table 2). Cross-comparison o f the sediment microfabric types show no significant differences between the types at the 0.05 level. Thunell (1998) and Pride et al. (1998) suggest that opal silica is the best proxy of primary productivity in the Gulf. However, the sediment microfabrics in Alfonso Basin have about the opal silica content which suggests that either the microfabrics are not indicative of shifts in surface productivity or that if there were originally differences in the opal silica content, diagenesis/dissolution of silica in the sediments has destroyed this signal. Core FF In general, down core variations in carbonate, TOC and opal silica in core FF are similar to those in core CP (Figure 16): Carbonate and sediment microfabrics are Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. CO REFFD A TA I I IT | I I I I | I I I I 50 u H H 100 W Q 150 O u 20Q ■LU1 .............. n U t t I I t H 1 1 I u 1U 1 LLLL p T i r p r n ij m i i T T T T rT T IT T T I I I I I I I rr i i ITT I I I T H IM ttlltltlt • • M I ItlM ttM tfllM lH •••••••••••• 1 .1 , I ••••••••••ft* •9 9 i i.i TTT • • . . i — J — L TTT TTT • • I I I I I I I 1 .5 2 2 .5 3 3 .5 4 4 .5 7 8 9 10 11 12 13 2 25 3 35 4 S ed im en t M icrofabric C a rb o n a te T o ta l O rgan ic C arb on 6 8 10 12 O pal Silica 14 Figure 16. Comparison of sediment microfabrics, carbonate, to tal organic carbon and opal silica in core FF, plotted against core depth in cm. O s o 6 1 inversely correlated with type 2 having the highest values. Trends in opal silica and TOC are similar. Scatter plots of carbonate, TOC and opal silica for FF are similar to the results in core CP (Figure 17). TOC versus carbonate shows no obvious patterns. Opal silica is positively correlated with TOC but negatively correlated with carbonate. The latter is different in core CP. It would appear that this does not agree with Flock’s (1993) and Prison’s (1998) models of carbonate increasing with decreasing oxygen values due to higher productivity. However, as stated earlier, this does not take into account down-core changes due to diagenesis. More on the implications of geochemical data will be discussed below. Carbonate The mean values for carbonate in core FF showed that the highest mean was in sediment type 2 and the lowest in 3B (Table 5 and Figure 16). T-tests values however, suggest that sediment microfabrics 3B and 3A are significantly different, whereas sediment microfabrics 3B and 2 are not. The t-test values also showed that sediment microfabrics 3 A and 2 are significantly difference. These values showed that 3 A was basically different than the other two types. Since 3 A lies between the other two sediment types it is difficult to determine the underlying control on the deposition and preservation of carbonate in FF. Sediment microfabric type 4 showed no differences with the other types. As with core CP it is obvious that the control of carbonate down core is controlled by many factors, including production and preservation. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. COMPARISON OF GEOCHEMICAL DATA FROM CORE FF TOC v s Carbonate C arb on ate v s Opal S ilica TOC v s Opal Silica 3 .5 c o X ) c 5 2 o | a . 5 O 1 5 o c 1 1 1 1 1 n 1 1 1 4 ...a;...... q □ 1 .5 TTTT ..s .. ft 1 1 1 1 1.LU- TTTT d .4 ... □ A y 1 1 I I'l T T T 1 1 1 1 I I 1 1 I II □ TTTT 1 2 1 1 1 0 C D 4 * * C D o 9 J Q i_ C O O □ #3B Sediments « #3A Sediments a #2 Sediments 6 7 8 9 1 01 11 21 3 Carbonate 8 7 6 T 1 1 i i i 'TTT I I I -] m i < ‘ 0 :tP ........ ........1 ...a... © ; iiil i i i C _ l_ l i a ■ ■ ■ c iii' 8 1 0 1 2 1 4 Opal Silica 3.5 c o ■ 2 3 c o O f a . s o 1 5 _ £ 2 .rrr T1 1 | i i q TIT □ TTT O ii ‘H P z < i i i » " J j ! iii- _ l_ l_ l_ 1 ,1 1 6 8 1 0 1 2 1 4 Opal Silica Figure 17. Comparison S catter Plots of Geochemical Data Form Core FF. Total Orgainc Carbon vs. Carbonate, Carbonate vs. Opal Silica and Total Organic Carbon vs. Opal Silica were compared to determ ine any correlating characteristics. O n Is) 6 3 Organic Carbon The organic carbon in core FF showed little difference between sediment microfabric types (Table 5 and Figure 16). The highest mean value was 2.84 % in sediment type 3B and the lowest was 1.84% in sediment type 4. According to the t-tests the only significant difference is between sediment microfabric types 4 and 3B and 4 and 2 (Table 4). Similar to core CP, TOC and silica opal correlate in core FF (Figure 17) it is possible that TOC is reflecting productivity. However, there is always the question of diagenesis and organic matter decomposition and the role it could play in organic carbon burial. Opal Silica Statistical analysis from core FF indicated that the opal weight in the core showed that the highest mean value was in sediment microfabrics 2 and the lowest in 3 A. The t-tests however, show that even though 2 and 3A have the furthest away means there is no significance difference between the two. The interesting part is that even though sediment microfabric 3B had a mean between 2 and 3 A, t-test analysis showed that it is significantly difference than 3 A. As seen in the discussion of silica opal in core CP, these differences between sediment microfabric types may be a produce of many factors. Comparison of core FF and core CP From the previous two sections it can be seen that there many differences between samples taken from Santa Rosalia and Alfonso Basin. Statistically, comparisons of cores FF and CP show that opal silica values are much higher in FF than in CP for all sediment fabric types. T-tests also indicate that there is a significant Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 64 difference between sediment types in FF and CP (Table 6). This implies that one or more of following is currently working in the Gulf: l)the area where FF is located has a much greater primary productivity than CP, 2) area FF recieves more biogenic debris, or 3) area FF experiences less opal silica dissolution. The difference is silica content closely matches the variation in surface productivity in which the highest values with the greatest diatom production occurs in the Guaymas Basin area (Thunell, 1998). However, CP contains the higher mean values in organic carbon. T-test values also indicate that 3 A and 3B sediment types are significantly difference between the two locations (sediment types 4 and 2 were not compared because they were missing from the data set) (Table 6). Compared to FF it suggests that CP has either: 1) a greater preservation rate of organic carbon, 2) a greater organic carbon flux, 3) less biological consumption of organic carbon or 4) a lower dilution rate due to lower sedimentation rates. Without knowing the diagenetic effects in both areas it hard to tell which factors are in control. Also, since CP is a silled basin, organic carbon may accumulate (higher organic carbon flux) more due to less lateral displacement. Carbonate between the two cores are very similar. Mean value in CP run between 7.98 and 11.58, while mean values in FF lie between 8.75 and 9.22 (Tables 2 and 5). Statistical t-tests showed that between cores FF and CP there are no significant differences between sediment microfabric types 3B and 2 (Table 6). Like all the other t-tests for the the two cores. 3 A is significantly different. According to the modified Savrda-Bottjer, type 3A is formed under bottom oxygen values of 0.1ml/l. For this sediment type to occur with a significant difference between the two locations implies that different factors occur at these locations when 0.1ml/l is reached. Why sediment type 3 A is significantly different between FF and CP is not known, but it is possible that a difference in bottom water chemistry may be the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6 5 control. Tables 3 and 5 indicate that for sediment type 3 A, CP has a larger range of carbonate values than FF. This could mean that carbonate product, dissolution, and/or preservation fluctucates more in Alfonso Basin when bottom water oxygen values reach 0.1 ml/1. X-Radiographs X-radiographs were examined and given sediment microfabric types based on the Savrda-Bottjer model as mentioned earlier in this paper. Cores from the both the Alfonso Basin and the slope off Santa Rosalia contained many turbidite/flood laminae which facilitated correlation between cores. Surface Patterns X-radiographs showed that at least the top 4 cm of all the cores examined from Alfonso Basin (Figure 18) and Santa Rosalia (Figure 19), except for core CG (CG may be missing its top), were bioturbated, indicating that seafloor oxygen values at present are greater than 0.2ml/l. This indicates that in within the oxygen minimum zone, dissolved oxygen values are presently about 0.2 ml/1. In the Gulf of California, Calvert (1964), Donegan and Schrader (1982) and Thunell (1998) show that the sediment couplets o f one light and one dark laminae represents one year of accumulation and that varve counts can be used to construct a simple age model for slope sediments. Using this method the average sedimentation rates for the Alfonso Basin is 1.7 mm/y and the slope off Santa Rosalia is 2.3 mm/y. These rates are in good agreement woth those determined from 210 Pb profiles (Nava-Sanchez, 1997). Assuming that the first appearance of laminations down core represents the transition from laminated to bioturbated conditions, that is, an increase in seafloor oxygen values, then the core data indicate that increase oxygenation Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ALFONSO BASIN CL L L I Q 200 4 0 0 6 0 0 '<A 8 0 0 ___ CE U X lA ❖ u X u X ❖ dX UX A L F O N S O B A S I N C -pr E2 Leo, s : CGCC CB CP pa civ C ore - in cm - 5 0 I - 0 10 2 0 DISTANCE (KM) 4 / 5 ( 2 ] 3 B |~ | 3 A G IB 2 ■ Turb m Disturbed g g POLYCHAETES CRUSTACEANS BEGQOTOA Rgure 18. Profile of Alfonso Basin, with core locations, sediment microfabrics down core and location of macrobenthic organisms. BENTHIC ORGANISMS O n O n Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SA N T A ROSALIA 0 4 0 0 8 0 0 1 200 CORE LENGTH BIOTURBATED * LAMINATED 5 0 c m OMZ Poly chaet es Crust aceans O p h iu roids L e p to p e c t in s M olluscs 0 2 4 6 8 1 0 DISTANCE (k m ) Figure 19. Profile of Santa Rosalia, with core location, sediment fabric type down core and location of macrobenthic organisms, BENTHOS Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 160, 140 120 100 Age (yr) of Oxygenation vs. Depth (m) 0 ) CT) < 80 60 40 2 0! 300 ♦ ♦ ♦ ♦ I - 400 500 600 700 800 900 1000 1100 1200 Depth (m) Santa Rosalia ♦ Alfonso Basin 1300 Figure 20. Plot of maximum age in years of oxygenation vs, depth in m in Santa Rosalia and Alfonso Basin. oo 6 9 occurred first at the deepest cores and progressed upslope (Figure 20). The transition at 900m is dated at approximately 50 years ago and at 350m at 35 years ago. In Alfonso Basin, the sill depth probably controlled flushing within the basin and the transition in ail the cores below the sill depth occurred at about the same time, approximately 35 years ago. Down-Core - Alfonso Basin In Alfonso Basin indicate that bioturbated intervals down-core are very few. Below the top bioturbated layer, the most common pattern of sediment microfabrics is 4 or 3B followed by 3 A and 2. This can be interpreted as intervals of oxygenation followed by a slow, gradual decrease in oxygen. A comparison of the two longest cores, CB and CP, show that this pattern o f 4/3B to 3A to 2 is repeated in both cores. To compare the down-core age of cores CP and CB the extrapolated ages were adjusted by subtracting out any turbidites (a centimeter or larger), assuming the turbidites represent “instantaneous” events. It was found that the oxygen-related patterns in both cores ranged between 130 and 150 years in duration and that the patterns can also be correlated between the two cores down to about 58 cm in core CB, where an erosional surface is present. Santa Rosalia In cores FC, FD, FF and IX-63 on the slope off Santa Rosalia, the top 5 to 8 cm is bioturbated but below this layer the sediments are moderately to well laminated. In cores EX-62 and FA, the first laminations are not encountered until 27 and 34 cm below the surface. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7 0 The pattern of sediment microfabrics was analyzed down-core in core FF and found to be very similar to the repetitive pattern found in cores CP and CB from Alfonso Basin: Well laminated sediments grade quickly into bioturbated sediments which gradually become more laminated with time. Applying the same method for determining the duration o f these microfabric events gives ages between 104 to 150 years for each ventilation event, again, similar to the duration o f the oxygen events in Alfonso Basin (Figure 21). The sequence of microfabric facies and the duration of the oxygen events they represent can be correlated between Santa Rosalia and Alfonso Basin for at least the past 600 years. Macrobenthic Organism Analyses Alfonso Basin The type and size of macrobenthic organisms in the Alfonso Basin indicate the presence of two different benthic faunal zones (Figure 18 and Table 7). Any type of ecological stress, such as oxygen, placed on community can be recorded as a reduction in 1) species diversity, 2) the size of organisms and 3) the amount o f endobenthic activity' (Bromley 1996). The first faunal zone at station 24, contains two types of polychaetes, crustaceans and small gastropods. The second faunal zone at station 25, contains only polychaetes. Also the size of the polychaetes in station 24 are larger than those in station 25. Polvchaete B in station 24 is 3 mm wide and 16 cm long, much large then the two types in station 25 ( 1 mm wide and 1 - 2 cm long). The higher species diversity and larger organism size at station 24, indicates that: 1 )seafloor oxygen values are higher, 2) organic content is higher, 3) seafloor energy regime is different, 4) water temperature is different, 5) sediment texture is different or 6) light penetration is different (Savrda et aL, 1984). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 71 COIVPAHSON OF SEDIMENT MICROFABHCS BETWEEN CO FES CB, CP, AND FF C B CP G C > 0 - I 2 0 0 - 4 0 0 - 6 0 0 - LU o < 8 0 0- L U DC O O 1 oooH 1 20(H Z222 153 130 83 130 2 1 2 206 176 l£ l£ l£ l 142 1 53 1 05 142 [W A WXA V K J W . 77WI M m 241 1 00 200 FF TuW 130 SE«3| S K M K M tS B 150 ___2 6 96 Age (yr) of Cycles 144 104 AA/ #4 MICFCFABRC #3BMICR0FABRC #3AMlCFCFABRC #2 MICFCFABRC Figure 21. Com parison of sedim ent m icrofabrics down core from cores CB, CP and FF. Duration of oxygen cycles listed to the right. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7 2 Santa Rosalia At Santa Rosalia, three faunal assemblages can be recognized (Table 7 and Figure 19). At station 62 at a depth of 1015m, small polychaetes and bivalves were found at the surface and worm-like organisms and bivalves were found down-core at approximately 30 cm. Organisms living 30 cm below the sediment surface implies that one of three things: 1) these organisms had some sort of ventilation system that was destroyed during coring, or 2) these organisms were utilizing a different form of respiration. Because of the presence of very small polychaetes and bivalves at the surface number 1 can be ruled out. Also, according to Bottjer (1998, personal communication), clams can burrow below the redox level. At station 63 a population of brittle stars, leptopectins, small polychaetes and bivalves can be seen. Except for one bivalve found 30 cm below surface, all were found on the surface. At station 64 a population of polychaetes and crustaceans were found. Station 64 contains the largest diversity of species and number of individuals per species so this would imply that station 64 has the highest amount o f oxygen compared to the two other sites. Station 63 contains a higher species diversity than station 62, however station 63 contains leptopectins which are believed to use chemosynthesis (Bottjer, 1998, personal communication) and also station 62 contains more organisms which dwell way below the sediment surface. This indicates that station 62 contains higher oxygen values than station 63. Patterns of Bioturbation and Lamination Sediment microfabrics in cores CB, CP and FF suggest a distinct pattern in which bioturbated sediment are followed by increase in lamination (Figure 21). Figure 22 demonstrates how this pattern can be interpreted as a trend of decrease in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VENTILATION CYCLE SEDIMENT MICROFABRIC 2 _ L _ 3A _]_ _ 3B = H CORE CYCLE TURBIDITE PROBABLE ERROR DUE TO BIOTURBATION 0 T ” 0.1 T 1 ------- 0 .2 > 0 .3 3B 2 3A 3B 4 3A SEAFLOOR OXYGEN LEVEL Figure 22. Schem atic diagram o f a typical ventilation cycle as seeii in core sed im en ts m icrofabrics. 7 4 oxygen following ventilation. In a typical pattern, decrease begins with an interval in which sudden seafloor oxygen values appear to increase. This can be seen as sediment microfabric type 2 shifts to a 4 or 3B. Following the original onset of oxygenation, oxygen values slowly decrease so that over time a sediment microfabric of 4 gradually changes to 3B, to 3A and so on. Many times changes from one sediment microfabric type to the next is gradual and difficult to pinpoint the exact beginning and end. This suggests that the shift in seafloor oxygen levels is gradual rather than rapid. It is also possible that the onset of oxygenation is gradual because some intervals contain a sequence o f 2 sediment types followed by 3 A and 3B and so on. Some ventilation cycles may be less intense than others. During these less intense intervals sediment microfabrics may be preserved either by oxygen values not reaching high enough values to allow for vertical bioturbation. During times of more intense oxygenation events the gradual sediment microfabric changes may be destroyed by intense bioturbation. These ventilation cycles are depicted for core CP (Figure 23). What can be seen (Figure 21 - 23) is that in the past 1200 years there have been seven intervals of oxygenation in core CP and CB. If core FF is added (Figure 21), four intervals have occurred in the past 600 years with the present being the onset of a new interval. To evaluate the variations in bottom oxygen values in the OMZ, hydrocast data for the Gulf of California were gathered from various studies (Sverdrup, 1941; Roden, 1964; Alvarez-Borrego and Lara-Lara, 1991) and Paleo VTH and Paleo IX cruises. Oxygen profiles for the mouth (near La Paz ) area and middle of the Gulf (Santa Rosalia) were compiled for the past 60 years (Figure 24). This data represents roughly twenty year intervals from 1939 to 1998. Data from the in-between years were not available, but do need to be taken in consideration. Hydrocast data from Paleo VIII and Paleo E X cruises were only available down to depths of 1000 m. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. O 0 1 2 0 - 40- 60- 8 0 - I h C L U J 100-1 Q UJ 120- C C 8 1 4 0 H 1 6 0 - 1 80- 200 - 2 1 2 - CORE SEDIMENT MICROFABRICS CP m m h ri h » j-j '1 /,ri n? 1 & ( i i : ^. V. V .V . V /y v w ^ a « a a « w m B n a i 1 2 3A 3 B 4 5 CYCLE I 0 0.1 0 . 2> 0 .3 OXYGEN LEVELS (ML7L) Figure 23. Comparison of sediment microfabrics down core in core CP with potential oxygen levels at time of deposition. "4 Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. GULF OF CALIFORNIA DISSOLVED OXYGEN (ml/I) 1939 - 1998 200 _ 400 _ J E X 600. t- CL U J Q 800. 0 C U J 5 1000 $ 1200 39 59 78 ‘98 LA PAZ ' * % • • N 0.5 " •s..'' • 0.1- • \ N N # m 0 m « » » ------ -0.5 s’ • ------ -0.2 ' <0.1 0.1* <0.1 • « • * t • • « <0.1 • • • • y • * 0.2- ------ * * * «( '0.2'* \ \ W ^ n S WV ^ s > s 0.5, ✓ 39 59 78 '98 SANTA ROSALIA Figure 24, Variations in dissolved oxygen at the mouth (near La Paz) and mid Gulf (Santa Rosalia) at four intervals between 1939 to 1998. Data summaries from various sources, including Sverdrup (1 9 3 9 ), Roden (1961), Alvarez-Borrego and Lara-Lara (1991) and PaleolX (1998). Hydrocasts in 1998 were only com plete to 1000m. 7 7 From this data oxygen values in the OMZ are lowest in 1939 and highest now. The oxygen minimum zone appears to have varied in intensity and thickness with the greatest changes at depth. In 1939, the OMZ is between 200 and 1000 m at La Paz and between 300 and 1000 m in Santa Rosalia. Twenty years later in 1959, the OMZ had shrunk to between 400 and 800m in La Paz and Santa Rosalia. During 1978, the OMZ has widen to between 300 and 900 m in La Paz, but has shrunk even more in Santa Rosalia to between 600 and 800 m. At present, the oxygen values within the OMZ are greater than 0.1 ml/1 and all areas sampled beneath the OMZ are bioturbated. The shift in oxygen over the past 60 years agrees with the age of the onset of bioturbation in the core tops (Figure 20). In the Santa Rosalia area and Alfonso Basin, the oxygen minima increased from <0.1 ml/1 in 1978 to >0.1 in 1998. By combining hydrocast data and oxygen biofacies based on the position of the sediment microfabrics, the OMZ in the central Gulf can be reconstructed (Figure 25). Sediment microfabrics in core FA indicate that at about 500 years ago the oxygen isopeth of <0.1 ml/1 reached a depth of at least 1250 m since FA shows extensive laminations during that time. The Gulf of California has been through several fluctuations in the thickness and intensity of the OMZ in the past several hundred years. From this analysis of the Gulf of California, patterns of bioturbation and laminations seem to be controlled by changes in the oxygen content of the Pacific Intermediate Waters which in turn control the OMZ in the Gulf. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. X H CL LU Q C C LU h- < § 0 TODAY 5 0 YEARS AGO 5 0 0 YEARS AGO 250 _ \ \ - 500_ 1Q00_ fK > 0.15 ml/l V Js. ^ < 0.15 ml/l 3 . <0.15ml/l 1 5 0 0 . C v S v s ‘ N. 7 - POSITION OF THE OXYGEN MINIMUM ZONE IN THE CENTRAL GULF Figure 25. Diagram show s the position and potential oxygen values of the oxygen m inim um zone in the central gulf at different lime intervals 0 0 CHAPTER 5 7 9 Conclusions The Gulf of California is a modem rifting ocean basin which is accumulating the modem equivalent of “black shale”. From this study several things can be said about the patterns of bioturbation and lamination in the Gulf of California sediments. 1) Modem slope sediments in the Gulf exhibit distincit sediment fabrics generated by burrowing benthic organisms which can be directly related to seafloor oxygen levels. Sediment patterns range from completely bioturbated where oxygen levels on the seafloor are greater than 0.3 ml/l to undisturbed laminations where oxygen values are less than 0.1 ml/l. 2) Sediments presently accumulating at all depths beneath the Oxygen Minimum Zone (OMZ) are bioturbated, including those below the sill depth (275m) in Alfonso Basin and the open slope off Sanat Rosalia (between 400 and 1000 m). However, below this surficial layer, laminated sediments are present. This shift in sediment fabrics indicated that there has been an increase in the dissolved oxygen within the OMZ in the Gulf, probably within the last 20-30 years. The shift observed in the sediment fabrics agrees with variations in the intensity and thickness of the OMZ compiled from published hydrocast data over the past 60 years. 3) Using a modified version of the Savrda-Bottjer sediment fabric/biofacies model, sediment fabrics can be objectively subdivided into six microfabrics and calibrated as oxygen-controlled biofacies from which benthic oxygen values can be estimated. The microfabric types: type 2, very well laminated without indication of burrows: types 3 A and 3B, well laminated with evidence of horizontal and vertical burrows; type 4, faintly laminated with obvious vertical burrows; and type 5, completely bioturbated. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 0 4) Down-core analysis of sediment cores from Alfonso Basin and the slope off Santa Rosalia reveal cyclic patterns in the microfabric types, with a typical cycle shifting from type 4 to 3B/3 A to 2, and then shifting back to a type 4/3 and repeating. These cycles can be interpreted as oxygen-controlled biofacies developed with ventilation events followed by slow decrease in seafloor oxygen. 5) The age and duration of the ventilation cycles can be estimated using a simple linear age model based on varve counts and Lead 210 profiles. The best-fit model for Alfonso Basin suggest average sedimentation rates o f 1.7 mm/yr and 2.3 mm/yr for slope sediments off Santa Rosala. Based on these values, the ventilation cycles range from 130 to 150 years and average 136 years. 6) The shift from lamination to bioturbated conditions appears to have occurred “from the bottom up”, with the transition occurring first at deeper sites within the OMZ and migrating into shallower depths over time. The shift, appears to have occurred about 60 years ago at the deepest locations and 20 years ago at the shallowest sites. This pattern suggests that the shift is related to changes in water quality in the Pacific Intermediate Waters. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Further Research The most important question that needs to answered is what ultimately controls the oxygen content in the Pacific Intermediate Waters that enters the Gulf of California. That property will answer what is controlling the patterns of bioturbation and lamination in the gulf. Other areas o f further research, are detailed refinement of the sediment microfabric model. At this time, it is extremely difficult to determine whether or not a 3B or 3 A was formed while sediments were being deposited or after lamination formation with small scale bioturbation occurring after. Another area of further research is a more detailed sampling of cores according to sediment microfabrics. Ten centimeter interval sampling is useless if the interval misses changes in sediment type. Also potential errors can be avoided if cores are cut where sediment microfabrics type are located and not in general areas. And above all, more cores, more cores, more cores. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 2 REFERENCES Alvarez-Borrego, S. and R.A. Schwartzlose. 1979. Water masses of the Gulf of California. Ciencias Marinas, v. 6, p. 43-63. Alvarez-Borrego, S. and J.R. Lara-Lara. 1991. The physical environment and primary productivity of the Gulf of California. In: Dauphin, J.P. and B.R.T. Simoneit, (eds.), The Gulf and Peninsular Provinces of the Califomias. Mem. Am. Asso. Pet. Geo., v. 47, p. 555 - 567. Archer, D. 1991. Modeling the calcite lysocline. Journal of Geophysical Research, v. 96, p. 17,037- 17,050. Atwater, T.. 1989. Plate tectonic history of the northeast Pacific and western North America. In: Winterer, E.L., D.M., Hussong and R.W. Decker, (eds.), The Eastern Pacific Ocean and Hawaii: Boulder, Colorado, Geological Society of America, The Geology of North America, v. N, p. 21 - 72. Axen, G.. 1995. Extensional segmentation of the main gulf escarpment, Mexico and United States. Geology, v. 23, p. 515 - 518. Baumgartner, T.R., V. Ferreira-Bartrina, H. Schrader, and A. Soutar. 1985. A 20-year varve record of siliceous phytoplankton variability in the central Gulf of California. Marine Geology, v. 64, p. 113 - 129. Bottjer, D.J. and C.E. Savrda.1993. Oxygen-related mudrock biofacies, p. 92-102. In: Wright, V.P. (ed.), Sedimentology Review/1, Blackwell, London. Boucher, J.M.. 1984. Silica dissolution and reaction kinetics in Southern California Borderland sediments. MS Thesis. University of Southern California. Bray, N.A.. 1988. Thermohaline circulation of the Gulf of California. J. of Geophysical Research, v. 93. p. 4993 - 5020. Bray, N.A. and J.M. Robles. 1991. Physical Oceanography of the Gulf of California. In: Dauphin, J.P. and B.R.T. Simoneit, (eds.), The Gulf and Peninsular Provinces of the Califomias. Mem. Am. Asso. Pet. Geo., v. 47, p. 511 - 553. Bromley, R.G. 1996. Trace Fossils: Biology, taphonomy and applications. Chapman & Hall, London, 361 p. Bryne, J. V. and L.P. Emery. 1960. Sediments in the Gulf of California. Geol. Soc. Am. Bull., v. 71, 983 - 1010. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 3 Byers, C.W..1977. Biofacies patterns in euxinic basins: a general model. In: Cook, R E . and Enos, P. (eds.), Deep-Water Carbonate Environments. Soc. Econ. Paleon. Miner. Spec. Publ., v. 25, p. 5 - 17. Calvert, S.E.. 1964. Factors affecting distribution of laminated diatomaceous sediments in Gulf of California. In: T. R van Andel and G.G. Shor, Jr. (eds.), Marine Geology of the Gulf of California. Mem. Am. Assoc. Pet. Geo., v. 3, p. 311 -330. Calvert, S.E.. 1966. Origin of diatom-rich, varved sediments from the Gulf of California. J. of Geology, v. 76, p. 546 - 565. Donegan, D. and H. Schrader. 1982. Biogenic and abiogenic components of laminated hemipelagic sediments in the Central Gulf of California. Marine Geology, v. 48, p. 215 - 237. Duxbury, A.C. and A.B. Duxbuy. 1997. An Introduction to the World’s Oceans. Wm. C. Brown Publishers, Dubuque, 504 p. Eppley, R.W. and B.J. Peterson. 1979. Particulate organic matter flux and planktonic new production in the deep ocean. Nature, v. 282, p. 677 - 680. Flocks, J.G. 1993. Transport mechanisms and element distribution in a semi-enclosed, anoxic basin, and the influences o f natural and anthropogenic input, California Continental Borderland. Unpublished MS Thesis, University of Southern California, Los Angeles, 230 p. Grant, C.W.. 1991. Distribution of bacterial mats (Beggiatoa sp.) in Santa Barbara Basin, California: A modem analog for organic-rich facies of the Monterey Formation. M.S. Thesis, California State University, Long Beach, 20 lp. Henrichs, S.M. and W.S. Reeburgh. 1987. Anaerobic mineralization o f marine organic matter: rates and the role of anaerobic processes in the oceanic carbon economy. Geomicrobiology Journal, v. 5, p. 191 - 237. Jahnke, R.A. and G.B. Shimmield. 1995. Particle flux and its conversion to the sediment record: coastal ocean upwelling systems. In: Summerhayes, C.P., Emeis, K.C., Angel, M.V., Smith, R.L. and B. Zeitzschel, (eds.). Upwelling in the Ocean: Modem Processes and Ancient Records. John Wiley & Sons Ltd. Jewell, W.J. and P.L. McCarty. 1971. Aerobic decomposition of algae. Environmental Science and Technology, v. 5 , p. 1023 - 1031. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 4 Kristensen, E. and T.H. Blackburn. 1987. The fate of organic carbon and nitrogen in experimental marine sediment systems: influence of bioturbation and anoxia. Journal of Marine Research, v. 45, p. 231 - 257. Molina-Cruz, A. 1986. Evolucion oceanographica de la boca del gulfo de California. Anales del Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico, 13(2), p. 95 - 120 Moore, D.G. and J.R. Curray. 1982. Geologic and tectonic history of the Gulf of California. In: Initial Reports of the Deep Sea Drilling Project: Washington, D.C., U.S. Goverment Printing Office, v. 64, p. 1279 - 1294. Nava-Sanchez, E.H. 1997. Modem fan deltas o f the west coast of the Gulf of California, Mexico. Unpublished Ph.D.. dissertation, University of Southern California, Los Angeles, Ca., 229 p. Parrish, J.T. 1982. Upwelling and petroleum source beds, with reference to Paleozoic. AAPG Bulletin, v. 66, p. 750 - 774. Parrish, J,T, and R.L. Curtis. 1982. Atmospheric circulation, upwelling, and organic-rich rocks in the Mesozoic and Cenozoic eras. Paleogeography, Paleoclimatology, Paleoecology, v. 40, p. 31 - 66. Pedersen, T.F. and S.E. Calvert. 1990. Anoxia vs. productivity: what controls the formation of organic-carbon-rich sediments and sedimentary rocks? The American Association of Petroleum Geologists Bulletin, v. 74, p. 454 - 466. Pilson, M.E.G. 1998. An Introduction to the Chemistry of the Sea. Prentice Hall, Inc.. New Jersey, 431 p. Pride, C., R. Thunell. and E. Tappa. 1998. Evaluating productivity proxies: results from the Gulf of California, (in press). Rhoads, D.C. and J.W. Morse. 1971. Evolutionary and ecologic significance of oxygen-deficient basins. Lethia, v. 4, p. 413 - 428. Roden G.I. and G. W. Groves. 1959. Recent oceanographic observations in the Gulf of California. Journal of Marine Research, v. 18, p. 10 - 35. Roden, G.I.. 1964. Oceanographic aspects of the Gulf of California. In: T. H. van Andel and G.G. Shor, Jr. (eds.), Marine Geology of the Gulf of California. Mem. Am. Assoc. Pet. Geo., v. 3, p. 30 - 58. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 85 Sageman, B.B., P.B. Wignall, and E.G. Kauffman. 1991. Biofacies models for oxygen-deficient facies in epicontinental seas: tool for paleoenvironmental analysis. In: Einsele et al. (eds.). Cycles and Events in Stratigraphy, p. 542 - 564. Savrda, C.E. 1983. Refinement of Euxinic Biofacies Models: California Continental Borderland. MS Thesis. University of Southern California, p. 167. Savrda, C.E. and D.J. Bottjer. 1983. Trace fossils as indicators o f bottom-water redox conditions in ancient marine environments. In: Bother, D.J. (ed.), New Concepts in the Use of Biogenic Sedimentary Structures for Paleoenvironmental Interpretation. Society o f Economic Paleontologists and Mineralogists, Pacific Section, no. 52. Savrda, C.E., D.J. Bottjer, and D.S. Gorsline. 1984. Development of a comprehensive oxygen-deficient marine biofacies model: Evidence from Santa Monica, San Pedro, and Santa Barbara basins, California Continental Borderland. The American Association o f Petroleum Geologists Bulletin, v. 68, p. 1179 - 1192. Savrda, C.E. and D.J. Bottjer. 1991. Oxygen-related biofacies in marine strata: and overview and update. In: Tyson, R.V. and Pearson, T.H. (eds.), Modem and Ancient Continental Shelf Anoxia, Geological Society Special Publication, n. 58, p. 201-219. Stock, J.M. and K.V. Hodges. 1989. Pre-Pliocene extension around the Gulf of California and the transfer of Baja California to the Pacific Plate. Tectonics, v. 8, p. 99-115. Sverdrup, H.Y. 1941. The Gulf of California: preliminary discussion on the cmise of the E.W. Scripps in February and March 1939. Sixth Pacific Science Congress Proceedings, v. 3, p. 161 - 166. Thunell, R.. 1998. Seasonal and annual variability in particle fluxes in the Gulf of California: a response to climate forcing. Deep-Sea Research (in press). Umhoefer, P.J., J. Stock, and A. Martin. 1996. Tectonic evolution of the Gulf of California and its margins. GSA Today 1996, p. 16 - 17. van Andel, T.H.. 1964. Recent marine sediments of the Gulf of California. In: T. H. van Andel and G.G. Shor, Jr. (eds.), Marine Geology of the Gulf of California. Mem. Am. Assoc. Pet. Geo., v. 3, p. 30 - 58. Zobell, C. E. 1942. Changes produced by microorganisms in sediments after deposition. Journal of Sedimentary Petrology, v. 12, p. 127 - 136. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix 1. Core CP Data. Core Depth Core Age Total in cm in years Carbon 0.5 2.941 176 7.74 1.5 8.823529 2.5 14.70588 3.5 20.58824 4 23.52941 4 23.52941 4.5 26.47059 8.35 5.5 32.35294 6.5 38.23529 7.5 44.11765 8.5 50 9.5 55.88235 10.5 61.76471 11.5 67.64706 12.5 73.52941 13.5 79.41 176 14.5 85.29412 8.13 15.5 91.17647 16.5 97.05882 17.5 102.9412 18.5 108.8235 19.5 1 14.7059 20 1 17.6471 20 1 17.6471 20.5 120.5882 21.5 126.4706 22.5 132.3529 23.5 138.2353 Carbonate 11.36 9.81 7.23 6.22 8.25 4.1 3.6 6.19 6.68 10.32 9.8 9.84 7.76 9.32 9.76 11.82 10.79 8.73 10.78 10.26 1 1.36 15.99 5.16 0 Total Organic Carbon 6.38 7.36 6.96 Core M icrofabric 4 4 4 4 4 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3B 3B 3B 3B 3B Silica Percent Opal Fish Bones 2.875 4.377 3,089 o o O n Appendix 1 Cont. 24.5 144.1 176 7.08 2.58 6.77 3 B 2.725 C D O C D C O C O C Q C Q C O C Q < < < < < < < < < < < < < < < < < < < < < < < < i:D (]D n c o n n n n n o n n o o n n n n n c o n n n n n n n n n c o c o o n C M C M C D C O C D ID C M O t O C O C M C D C M C D C D O ' O ' C O C DC D L D C O C O C O C O L O C M C O C M C DC DID C D C O * T - o o ' C D O ' C O o - C O C O C OC D c m C O C M c m o - C O co C O C D C O o C O o T - d c d ’ d r ~ - O ' co’ C O C M c m ’ c m ’ o- C D C O C M C M O' r -~ C M C M O' 00 T- L D C O C M C D C D C M C D C D C O C O O' i— O' 00 i— ID oo C M O " r - ~ O O C O C D — o- C D C O • » — C O L O C O O C M ID N * C M O' f-- C D I— O' C D oo t — 1 O O C D O' C O 00 C M i — C D C ' - L D O' C M O C O f'- ID C O * 1 — o 00 C D O " C M ■ » - C D r- I D O O C D C O r - ~ C D C D C D C D O ’ C M • « — O C D 00 h- ID o - C O C M T " I m 00 f - C D L D O' C M O O O C D r-- O d co’ C D C D r-- C M O O o- O d C M O O C M ID D- C O d ID T- r^ C O C O C D C D co r^ 1 " ' - r - ~ h- 00 C D C D O O T -- C M C M C O C O ID C D C D C O c n > C D T — t — T — ‘ r* ’ T — T — ' C M C M C M C M C M C M C M C M C M C M C M C M C M C M C M C M ID C D C D C D C D C D C D L D ID ID ID ID ID ID ID ID in in ID ID ID L D ID ID ID ID C D C D . • . . • • • » • » ♦ • • • • • T * “ T ” C D C D r ^ . 00 C M C M C D o T — C M C O O' C D C D N- C O C D o C M C O O' ID C D r-- 00 C D o ID ID C M C M C M C M C M C O C O C O C O C O C O C O co C O C O O' O' O' O' O' o - O' O' ID C M O ' c d o C O C D C D Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix 1 Cont. 52.5 308.8235 4.65 53.5 314.7059 5.64 54.5 320.5882 4.6 55 323.5294 55 323.5294 55.5 326.4706 6.67 56.5 332.3529 8.72 57.5 338.2353 8.73 58.5 344.1 176 9.21 59.5 350 10.3 60.5 355.8824 8.42 61.5 361.7647 7.9 62.5 367.6471 3.13 63.5 373.5294 7.33 64 376.4706 64 376.4706 64.5 379.41 18 7.33 65.5 385.2941 7.73 66.5 391.1765 7.24 67.5 397.0588 10.34 68 400 68 400 68.5 402.9412 11.97 69.5 408.8235 9.31 70.5 414.7059 15.41 71.5 420.5882 6.66 72.5 426.4706 3.56 73 429.41 18 73 429.4118 73.5 432.3529 2.06 74.5 438.2353 5.67 75.5 444.1 176 9.77 3B 3B 3B 3B 2 2 2 2 2 2 2 2 2 2 2 3A 3A 3A 3A 3A 3A 3B 3B 3B 3B 3B 3B 3B 3A 3A 3A 3A 0.863 1.108 1 .3 7 2 O O oo 89 0 5 C O • < s - C\J 05 CM i - ■ ^ 00 O 00 n n n c o c o n n n c o c o n n n n o n n n n n n n o n ^ ^ ^ ^ ^ ^ ^ n C M U 5 in C O C O C O ■ o - in C O o o C O C O C O T —■ » — o o ’ i n ’ ■ ' 3 " h - ’ c o ’ 0 5 o ® . • o in co C M 05 C O cm r-- 00 co’ CM 0 5 05 0 0 CO CO t''- ■ '3 " L O f'- CM 0 5 T -- 05 in CM 0 0 CM CM OO CM 05 ■'3' CM o ’ o ’ T— ' o ’ ■O' CO • t — C M C M CO C M T --- C M t* - T — ■^r o o i n 0 0 CM ■cr i n 0 5 C M CO 0 5 CO CD ^ r r - T — C M C M ■^r o o T — 0 5 ^3" 0 5 0 5 C M ■ '3 ' 0 5 T — •O’ CO 0 0 T — C M C M CO i n 0 0 o C M i n f" - C M •o - t ''- o o 0 0 0 5 T - ■ ^ i n 0 5 C M C M o O O CO ■^ C M T— 0 5 r - i n 00 00 C M o 00 r^- m CO T— o o o CO '3 ' 00 00 C M 1 — 0 5 o C M i n i n m 0 0 r^- CO i n •^3' C M * r— o 0 5 CO o o 0 0 r^- i n -'3' CO C M m o o CD i n i n i n C M r - - i n CO CO ■ m - i n h-’ CO 0 5 m t— t" . CM i n i n 0 0 ■sf o c o ’ C M 0 0 i n i n T ~ h - o o CO 0 5 i n CO C M C M i n CD CO r - r-'- 0 0 0 5 0 5 O o o o T — C M CM CO CO • ^ 3 - i n CD CO t-- h - 00 T — f - 0 0 o o ^3" ■ < 3 - •<3- ■ S 3 " t 3" ■ ’3 ' i n i n i n m m i n LO i n i n m i n i n i n i n i n m i n i n CO co CO CO = CO S .'- Q . < in in in in in in m in in CO co in in in in in m m i n m m in in m CD • • • • • • • . N - * • r-^ o o ’ 0 5 o ^— C M C O ^3" in oo 00 co 00 0 5 o C M C O ■ * 3 - in CO 0 5 0 5 h-’ oo 0 5 r-- r-'- 00 oo 00 00 O O 0 0 oo 00 00 0 0 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 in in ■ ' 3 - - < 3 - O i- CO CO Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 90 in C M C M i n rv c n c o ■ M - 0 0 0 0 C M CO C M CO in 0 5 in CM t v in T — CO CO i — r v 0 0 O 0 0 o in i — 0 5 CO in o 0 0 -t— r~ - ■ , - - 0 0 * . • . T “” T — o ’ C M 'T — o CO rv 0 0 00 00 i n t v C M CO in C O C O C O C O ^ C O C O C O C O ^ ^ ^ C O C O C O C O C O C O C O C O r - 0 0 0 0 i n t v m CO r v 0 0 CO 0 5 o 0 5 I v C M C M i n o i n 0 5 CO 0 5 0 0 3,3 i n i n m m i n c o ’ i n CO C M C M *3- ■<- 0 5 [ v CO C M O CO CO c m ’ i n cm [ v o o ’ « CO 0 0 0 0 in C O r v T“ in - M - 0 5 00 <3" CO in 00 C O C M CO C M ■sf ’ C O 0 C O O * co ’ c d O CM C M 0 0 ’ 0 5 0 r v t— y — • * — ^ T— CO CO 00 in CO CO co’ w 0 5 c o 0 5 CD •t — 0 5 ■ '4 - t v r v r v c o co r v 0 0 r v tv . 0 0 CO .— i n C M 0 t v CD CD r v co’ CO i n IV ■ M " C M 0 5 CO C M C M i n r v CO 0 5 CO C M i n c o t v T— T f CO 0 0 0 5 i n CO C M C M i n i n m CO t v IV C M T— i n r v r v C M 0 5 0 5 i — C M CO 0 5 ■ < 3 - rv - 0 5 T— C M CO CO T— T — CO CO CO t v ■'3" T— ■0- •O’ CO T f • > — i n i n r v 0 0 0 C M CO C M T— i n 0 5 tv . i n "M " • *3 " C M C M r v y— CO CD O 0 5 0 5 0 C M CD CO ■ M - 0 0 0 0 t v m tv - CO i n •M " •O ' CO C M 0 0 5 0 5 00 0 0 t v t v m 0 5 C M C M 0 0 0 r v r v 0 5 IV t v CO LO CO [ v co’ 0 5 0 5 C M i n rv - C M C M 00 CO .— ■ < 3 - ,- 1 y-i CO C M i n i n 0 5 CO t— T - C M I V 0 CO C M 7— T— C M C M C M CO CO ■ M " ■ < 3 - i n i n i n i n 0 5 0 5 t — y— i n CO 0 0 0 T --- y — i n CO CO CO t v r v CO ( v tv - tv . f v fv . fv . fv . tv . tv . f v r v tv . tv - r v t v CO CO 00 CO CO 0 5 05 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 X ■ 5 ^ _ C M CO '3 " c C M C M C M C M C M <D T “ y — T— .— c . c . < LD in CO CO in i nin CO in in CO f v CO CO 0 5 0 5 in in . *3- C M C M C M C M C M C M C M ■ m - CO CO CO ■ * 3 " 0 o ’ in *3" C M T “ ' 1 — T~ 'r ~ CO ■ * “ ■O' T _ i nin T — ‘ in i n i n cm t " M " i n i n c o c o c o i n i n c0 IV -= 3 - CO CO CO CO V“ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 91 LO LO ID LO LO LO LO LO LO LO LO LO LO - - t — T — L O * L O L O . - . - O O O O O CM O C M C M C M C M O O I"- 05 N- O CO 0 5 C M N - CM 0 5 CO CO T ™ - CO CO CO CO p . — 1— CO i — ^— CD r— 0 5 C M CO O CD 1^ 1— N CO CD 0 5 0 5 LD CD LO C M CD C M LO 0 5 CO CD 1 — CO T — CD LO 0 0 N - 0 5 N - 0 5 LD ' 0 0 1 — 0 5 O C 5 o o ’ O C 5 C M T -‘ C N J o o o LO N - CO ■ * CD ' CD C M CO O LD r 1 C O C O 0 5 CO CO CM O CD LO CD LO g O j LD 0 5 CO CO j - CO £ S n o o n o n c D n c o o n o n n ^ Tt't T f ^ ^ ^ ' t 't o J w n n o n c o CO oo CO o o t o ID 1— CO N - CM 00 ID* Tt- LD 05 00 C O C M C M O O C M C O C D “ o C O ’“I O C O ID « d LD ID L D ’ ■ M - CO C M LO CO -M- ^ m ^ h - CO CD S ^ C M S S „ O 0 5 0 O - r - . 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O [ j ) S ( D C D C D L O ' t C M C M ' - O O O ) t D N L O ^ O W N N C D 0 T - C ) O o 5 r _ o ..........................................................................................................................................................................................................LOLO r .^oin'-NNNCODLnLO'-NSCMOOM-ODCMmT-T-NNM^^.CM QOOM-r- 0 ’-T-T-i-CMCMnCO'tM-M-lOLODNSOOffl'-i-'-r-M-^^0 r ) 00 05 O O O O O O O O O O O O O O O O O O O l — T - 7 — T — CM U 05 05 ^ LO LO LO LO nCOO)O'-CMOOOM-lOCO0SCOCOO)O'-WO^inO)O)OO ^-CDCDNNNNNNNNNNNNSNCOCOODCOCDQOtOmCTim^lOLO^' £ 3 _________________________________________*— ■ * — ■ » — t— t— t— ^— t— 05 05 05 CD CO i— CO o o CD CM CD CO CO CO CO 00 CO CD CD CO CO ■*- O CO CD d d CD CO CO ID O CO N - ID CO N - ID ■'3" CO C M •M" d d c m ’ CO CD N - N - CO CO O o o o o r— C M CO ■ M - ID CO CO CO CO 0 0 o. a. < CM Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Core Depth Core Age Carbonate Core Total Silica 92 I — 0 5 LO h - CO T --- 0 5 CO 0 5 N - 0 T— LO CO O ' 0 0 0 CM o ’ 0 5 ’ CO CD co’ T “ CO d cm’ " c c o co - Q o o CO 05 D- IO CO CM 05 05 CM CO 05 T” CO CO CO 1- IO O CM CO CM CM CM CM CO CM O - CM IO 05 CO CM o Si , f ° in 1 0 in m tn in in — ■ t r co co co cm cm w w c v i n n cm c v i w co n co n o L . o CO CO CO CO CO CO CO CO CO O' CO 1 0 t- CO CO CO 1 — 05 CO 1- 0 CO CO O O’ CO CO 00 1 0 05 CO 1— CO CD CO CO CO CO CO CO CD •O’ CM CD ■ 1 — T “ “ CD C M C M D '- C M C M r" - CO CO r - CD CO 0 5 CO C M C M 0 0 1 0 in T— r - m C M C M CO r~ - 10 10 0 CO CO C M O - O ’ CD CO CO D - T — CO CO CO i ninin CO CO CO r - - CM 10 10 C M 0 5 CD CO O ’ O ’ CO O ’ O " C M t o 0 5 05 ’ CO CO co’ in 0 0 0 CO CO 10 CD CD co CO 0 0 0 5 ■ >— i n m C M C M r — CD O ’ O ' t" - CO CO C M CO CO i n in CD 0 5 CO i-'- f '- CO 0 0 O ’ O ’ C M O ’ O ’ CO CO CO CO (■'- 1— T — O 0 0 0 i n 0 0 i n i n t " - 1 ''- C M C M CO CO CO CO CO CO co’ CD 0 5 t -I cm’ in ’ LO cm’ CM 1 — T-in I — T — T — T— CM C M in CO CD OO 0 0 0 5 0 5 0 5 1 — T- 1- - ---- T --- 1 — i— 1— i — 1— ^— 1 — ■ * E o LO to C M I O C D C O O O O W M ’ M ' I O C D C D • • C O C O t O O O C O C V I O J ' J ^ ’ lO O CO CO __ r \ t r\i /-* i a i r \ r r \ I r \I /%i f 1" £\J £\J qt) Qf) jr) CMCMCMCMCMCMCMCM CM CM Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix 2 Cont. 52 226.087 3 52 226.087 2 55 239.1304 6.28 2 2.55 60 260.8696 2 60 260.8696 3 65 282.6087 9.69 3 3.1 65 282.6087 3.5 75 326.087 7.62 3.5 3.19 78 339.1304 10.586 3.5 2.796 80 347.8261 9.065 3.5 3.881 80 347.8261 3 82 356.521 7 10.571 3 2.778 82 356.5217 3.5 85 369.5652 9.33 3.5 2.51 85 369.5652 3 95 413.0435 6.15 3 1.74 96 417.3913 3 96 417.3913 3.5 105 456.5217 11.21 3.5 3.27 108 469.5652 3.5 108 469.5652 3 1 1 0 478.2609 3 110 478.2609 2 1 1 5 500 8.94 2 3.27 118 513.0435 2 123 534.7826 2 123 534.7826 3 125 543.4783 10.51 3 3.18 135 586.9565 10.1 3 3.95 140 608.6957 3 145 630.4348 3 145 630.4348 12.84 2 2.93 11.057 12.068 U > Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A ppendix 2 C ont. 153 665.2174 153 665.2174 155 673.913 9.03 165 717.3913 7.66 167 726.087 1 67 726.087 175 760.8696 8.7 1 75 760.8696 176 765.2174 8.317 178 773,913 10.308 180 782.6087 10.452 180 782.6087 1 82 791.3043 9.532 185 804.3478 8.85 1 86 808.6957 9.451 2 3 3 3 3 2 2 3 3 3 3 3 3 3 3 2.84 3.3 2,32 2.337 1.948 7.297 1,961 5.9769 5.704 2.064 5.0047 2,25 2.044 4.6869 M 3 4 * Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix 3. Core Fabrics of the Gulf of California Area Station Depth Length of Core Depth Sediment Observations in m Core in m El Coyote CA 370 45.5 CB 391 204 in cm Microfacies 0 -5 4/5 small shells 5-6 2 thin 1mm to <1mm laminations 6 turbidite 6-8,5 2 small shells 8.5-15 3A 15-17 3B 17-18 turbidite 18-30 3B burrows at 18 cm; small shells 30 turbidite 30-41,5 thin 1mm thick laminations 0 -5 4 5-14 2 14-17 3A 17-19 turbidite 19-31 3B 31 -41 3A turbidite at 35 & 39 cm 41-48 3B turbidite at 42 cm 48-53 4 53-59 3A erosional surface at 58 cm 59 - 65,5 3A 65,5 - 67 3B erosional surface at 69 cm 67-79 3A erosional surfaces at 70, 73 & 79 cm 79-89 3B 89-104 3A 104-125 4 erosional surface at 122 125-138 3A turbidite at 126 & 127 138-160 4 160-167 3A 167 -190 4 turbidite at 153 -155 190-204 0 -5 4/5 burrows CC 390 39 0 -5 4/5 burrows >5 Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. CD 380 118 CE 45 6 6 - 9 9-13,5 13.5-16 16-20 20-24 24-29 29 29-33 33 33 - 35,5 35.5 35.5 - 39 0-8 8 8-20 20 20-40 40-52 52-58 58-67 67 - 68,5 68.5 68.5 - 70,5 70.5 - 74.5 74.5 - 88 88-98 98-100,5 100.5 100.5-118 0 -4 4 - 5 5 5 -6 6-19 turbidite 3B 3A 2 disturbed/slump 2 erosional surface at 22 cm 3B 3A 2 3B 4 3B 3B 3B turbidite turbidite turbidite 2 4 turbidite 3A fish bones at 9 cm scour/ slump? 3A fish bones at 25,5 cm 3B 4 3A 2 turbidite 2 3A 3B fish bones at 76 cm 3A 3B turbidite turbidite s O o\ Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. CF 378 41 CF 2 170 21 CG 385 43 CH 255 116 CL 620 29 CP 390 212 19-20 20-26 26-43 43-45 0-41 0-21 0 -4 4 -5 5 5-7,5 7,5 7.5-19 19-20 20-30 30-35 35-43 0-116 0 -3 3 -5 5 -7 7-29 0 -4 4 -19 19-20 20-29 29-30 30 30-51 51 -55 55-64 64-68 68-73 73-86 86-97 97-116 turbidite with burrows at the bottom 4 3B fish bones at 30 cm erosional surfaces 5 fish bones 5 burrows 3B 3A decreasingly fuzzy laminations turbidite 3A turbidite 3B burrows at 15 -19 cm? turbidite 3B 3A 2 5 4 3B 3A slump 4 3A shell fragments turbidite 3B 3A turbidite 3A fish bones at 38 cm 3B 2 3A 3B turbidite at 70 cm 3A fish bones at 74 cm 4 2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Santa Rosalia CN 370 42 C M 405 43 FA 1250 190 116-124 124-138 138 - 150,5 150.5-155 155-162 162 162-164 164-173 173- 178,5 178.5- 189 189-190 190- 195,5 195.5-212 0-6,5 6.5 6,5-10 10-12 12-19 19-22,5 22.5 - 27 27 - 32,5 32.5 - 35,5 35.5 - 37,5 37.5-41,5 0-6 6 6-12 12-15 15-26 26-31 31 -33 33-43 0-34 34-36 36-90 burrows at 116 cm fish bones at 146 cm turbidite at 153 cm turbidite fish bones at 168 cm turbidite laminations small shells burrows turbidite burrows fish bones at 18 cm shell fragments Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. FB 880 165 FC 900 28 FD 740 22 FF 620 220 90-106 106-112 112-114 114-121 122-138 138-142 142-155 155-190 0-165 0-8 8-18 18-28 0-8 8-22 0-8 8-20 20-21 21 -24 24-27 27-27.5 27.5-28 28-32 32-33 33-34 34-36 36-38 38-42 42 42-44 44-45 45-52 52-56 56 56-58 58 2 3A 3B 3A 3B 3A 3B turbidite; shell fragments 4 mixed sediments; bioturbation 4 shell fragment 3A 4 shell fragments; burrows 4 bivalves 2 4 3B 3A 2 3A 2 2 3A 3B turbidite turbidite turbidite turbidite turbidite turbidite turbidite 3A 2 burrow or shell at 52 - 54 cm turbidite 2 turbidite g Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 58-60 60 60-65 65 65-79 79-80 80-82 82 82-85 85 85-86 86 86-89 89 89-95 95 95-107 107-108 108-110 110 110-120 120 120-122 122 122 -123 123-140 140 140-142 142 142-144 144 144-145 145 145-153 153-155 2 turbidite 3B shell fragments and bivalves at 64 - 65 cm; bivalves at 70 and 79 - 80 err turbidite 3B turbidite 3A bivalves at 81,5 cm turbidite 3B 3A 3B 3B 3B 3A 2 2 turbidite turbidite turbidite turbidite turbidite turbidite turbidite turbidite 2 3A bivalves turbidite 2 2 2 2 3A § turbidite turbidite turbidite Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. FG 330 23 FH 500 29 Str - 22 42 IX-62 1015 37 IX-63 630 33 IX-64 265 18 155 155-164 164 164-174 174-178 178-220 0-23 0-29 0-16 17-18 18-42 0-25 25 25-27 27 27-33 33-34 34-37 0 -5 5-20 20-24 24-33 0 -5 5-18 turbidite 3A turbidite 2 3A unknown/turbidite 5 U-shaped burrows 4/5 burrows 5 U-shaped burrows 3A 4 4/5 denser pellets? faint laminations; turbidite? 3B turbidite turbidite 3B 4 3B 3A 3B 5 1 mm wide burrows/tubes 5 o Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix 4. T-tests for Cores CP and FF. t-tests for CP %Opal Weight 4 3B 3A 2 X x - mean (x - mean)A 2 X x - mean (x - mean)A 2 X x - mean (x - mean)A 2 X x - mean (x - mean)A 2 2.875 1.52881063 2,33726193 2.725 1.51516923 2.2957378 4.377 2.963432 8,78192922 1.042 -0.4195 0.17598025 1.426 0,07981062 0,00636974 0.863 -0,3468308 0,12029158 3,089 1.675432 2.80707239 1,881 0,4195 0.17598025 1.0036 -0.3425894 0,11736748 0.924 -0.2858308 0.08169923 0.61 -0,803568 0.64572153 1,4615 0.3519605 0.85351 -0.4926794 0.24273297 0,84685 -0.3629808 0.13175504 0,786 -0,627568 0.39384159 2.1119 0,76571063 0.58631276 1.2814 0.07156923 0.00512215 1.108 -0,305568 0.0933718 1.125 -0.2211894 0,04892474 0.924 -0,2858308 0,08169923 1.372 -0,041568 0.0017279 1.7977 0.45151063 0.20386184 0,627 -0,5828308 0.33969171 1,39 -0,023568 0.00055545 1,1385 -0.2076894 0.04313488 0.92987 -0.2799608 0.07837803 0.873 -0.540568 0,29221376 0,85012 -0.4960694 0.24608482 0.75231 -0,4575208 0.20932525 0.471 -0.942568 0.88843443 1.48 0,13381063 0.01790528 0.99827 -0.2115608 0.04475796 1,532 0.118432 0.01402614 0.588 -0.7581894 0,57485113 2.5601 1,35026923 1,823227 1.1257 -0,287868 0.08286799 1.8173 0.47111063 0.22194522 1.66 0.45016923 0.20265234 1.8079 0,394332 0,15549773 2,1313 0.78511063 0,61639869 0,636 -0.5738308 0,32928175 1.6989 0,285332 0,08141435 0.78803 -0,5581594 0,31154189 1,20983077 5.74361907 0,86167 -0,551898 0.3045914 0,634 -0.7121894 0,50721371 0,75622 -0,657348 0.43210639 0.91907 -0.4271194 0.18243096 0,627 -0,786568 0,61868922 1,34618938 6.26433804 0,92987 2,5601 1.66 0,636 1.413568 -0.483698 0,23396376 1.146532 1,31453563 0.246432 0,06072873 -0.777568 0.60461199 17.8079014 u1 =true mean of bloturbated sediments n1 =number of sam ples In bloturbated sediments u2=true mean of very fuzzy laminated sediments n2=number of samples in very fuzzy laminations m eanl -m ean of bioturbated sediments x1 =bloturbated sample mean2=mean of very fuzzy laminated sediments x2=very fuzzy lamination sample s1=standard deviation of bioturbated sediments s2=standard deviation of very fuzzy laminated sediments H: u1 =u2 (there Is no difference between %opa| weight in bioturbated or very fuzzy laminated sediments o t o A: u1#u2 (there is significant difference between %opal weight in bioturbated and very fuzzy laminated sediments) We reject H In favor of A if |t|>ta/2(n1+n2-2] where ta/2[n1+n2-2)=t0,05/2[16+13-2]=t0,025[27]=2,052 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. t=(mean1-mean2)/sqrt(((sum(x1-mean1)A 2+sum(x2-mean2)A 2)/(n1+n2-2))*((1/n1)+(1/n2))) t= 0,54759886 |0,5475989|<2.145 so we accept H at significance level 0.05 At significance level 0.05 there is no difference between %opal weight in bioturbated and very fuzzy laminated sediments u1 =true mean of bioturbated sediments n1=number of samples in bloturbated sediments u2=true mean of fuzzy laminated sediments n2=number of samples in fuzzy laminations m eanl =mean of bioturbated sediments x1 =bloturbated sample mean2=mean of fuzzy laminated sediments x2=fuzzy lamination sample H: u1=u2 (there is no difference between %opal weight in bioturbated or fuzzy laminated sediments A: u1#u2 (there is significant difference between %opal weight in bioturbated and fuzzy laminated sediments) W e reject H In favor of A if |z|>za/2 where za/2=z0,05/2=z0,025=1,96 z=(mean1 -mean2)/sqrt((s1 A 2 /n1 )+(s2A 2/n2)) z= -0,2261131 |-0,22611311<1,96 so we accept H At significance level 0.05 there is no difference between %opal weight in bioturbated and fuzzy laminated sediments u1 =true mean of bioturbated sediments n1 =number of samples In bloturbated sediments u2=true mean of laminated sediments n2=number of sam ples in laminations meanl=m ean of bioturbated sediments x1 =bioturbated sediment sample mean2=mean of laminated sediments x2= lamination sample H: u1=u2 (there is no difference between %opal weight in bioturbated or laminated sediments A: u1#u2 (there is significant difference between %opal weight in bioturbated and laminated sediments) We reject H in favor of A if |t|>ta/2[n1+n2-2j where ta/2[n1 +n2-2]=t0.05/2H 6+2-2]=t0.025[16]=2.120 g t=(meanf-mean2)fsqrt(((sum(xVmeanf)A 2+sum(x2-mean2)A 2)l(nf+n2-2))*((f/nf)+(f/n2))) t= -0,2390895 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. |-0,2390895|<2,120 so we accept H at significance level 0.05 At significance level 0.06 there is no difference between %organic carbon in bioturbated and laminated sediments u1=true mean of fuzzy sediments n1=number of sam ples in fuzzy sediments u2=true mean of very fuzzy laminated sediments n2=number of samples in very fuzzy laminations m eanl =mean of fuzzy sediments x1=fuzzy sample mean2=mean of very fuzzy laminated sediments x2=very fuzzy lamination sample s1=standard deviation of fuzzy sediments s2=standard deviation of very fuzzy laminated sediments H: u1=u2 (there is no difference between %opal weight in fuzzy or very fuzzy laminated sediments A: u1#u2 (there Is significant difference between %opal weight in fuzzy and very fuzzy laminated sediments) We reject H in favor of A if |t|>ta/2[n1+n2-2] where ta/2[n1+n2-2]=t0,05/2(17+8-2j=t0,025[23]=2,069 We reject H in favor of A if |z|>za/2 where za/2zt0.05/2=z0,025=1.96 z=(mean1 -mean2)/sqrt((s1 A 2 /n1 )+(s2A 2/n2)) z= 0.63910482 |0.6391048|<1.96 so we accept H At significance level 0.06 there is no difference between %opal weight in fuzzy and very fuzzy laminated sediments u1 =true mean of very fuzzy sediments n1=number of samples in very fuzzy sediments u2=true mean of laminated sediments n2=number of samples in laminations m eanl =mean of very fuzzy laminated sediments x1 =very fuzzy laminated sample mean2=mean of laminated sediments x2= lamination sample H: u1=u2 (there is no difference between %opal weight in very fuzzy laminated or laminated sediments A: u1 #u2 (there is significant difference between %opal weight in very fuzzy laminated and laminated sediments) •P We reject H in favor of A if |t|>ta/2[n1+n2-2J where ta/2[n1+n2-2J=t0,05/2[13+2-2j=t0.025[13]=2,160 t=(mean1 -mean2)/sqrt(((sum(x1 -m eanl )A 2+sum(x2-mean2)A 2)/(n1 +n2-2))*((1 /n1 )+(1 /n2))) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. t= -0,4838774 |-0.4838774|<2.160 so we accept H At significance level 0.05 there is no difference between %opal weight In very fuzzy laminations and laminated sediments H: u1=u2 (there is no difference between %opal weight in fuzzy laminated or laminated sediments A: u1#u2 (there is significant difference between %opal weight in fuzzy laminated and laminated sediments) We reject H in favor of A if |t|>ta/2[n1 +n2-2) where ta/2(n1 +n2-2]=t0.05/2[20+2-2)=tO,025I20]=2.086 t=(mean1 -mean2)/sqrt(((sum(x1 -meanl )A 2+sum(x2-mean2)A 2)/(n1 +n2-2))‘((1/n1 )+(1 /n2))) t= -0.0678271 |-0,06782711<2.086 so we accept H At significance level 0.05 there no difference between %opal weight in fuzzy laminations and laminated sediments u1=true mean of fuzzy sediments u2=true mean of laminated sediments n1=number of samples In fuzzy sediments n2=number of samples in laminations m eanl =mean of fuzzy laminated sediments mean2=mean of laminated sediments x1=fuzzy laminated sample x2= lamination sample 105 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. t-tests for CP % Carbonate 4 3B x x - mean (x - mean)A 2 X x - mean (x - mean)A 2 11,36 1.67811765 2,816078837 11,36 3,1502 9,92376004 9,81 0,12811765 0,016414131 15,99 7,7802 60,53151204 7,23 -2.4518824 6,011727073 5,16 -3,0498 9.30128004 6,22 -3,4618824 11,98462943 2,58 -5,6298 31,69464804 10,75 1,06811765 1,140875308 2,06 -6,1498 37,82004004 7,502 -2.1798824 4,751887073 6,15 -2,0598 4,24277604 10,234 0,55211765 0,304833896 2,05 -6,1598 37.94313604 13,388 3,70611765 13,73530801 5,32 -2,8898 8.35094404 14,265 4.58311765 21,00496737 3,64 -4.5698 20,88307204 9,47 -0.2118824 0.044894131 4,65 -3,5598 12,67217604 10,1 0,41811765 0,174822367 5,64 -2,5698 6,60387204 11,216 1,53411765 2,353516955 4,6 -3.6098 13,03065604 8,688 -0,9938824 0,987802131 11,97 3,7602 14,13910404 8,361 -1,3208824 1.74473019 9.31 1.1002 1,21044004 8.328 -1,3538824 1,832997426 15,41 7,2002 51.84288004 8.64 -1,0418824 1.085518837 6,66 -1,5498 2,40188004 9,03 -0.6518824 0,424950602 3,56 -1,5498 2,40188004 9,68188235 70.41595376 12,35 4,1402 17.14125604 8,29 0,0802 0,00643204 6,73 -1.4798 2.18980804 11,87 3.6602 13.39706404 7.82 -0,3898 0,15194404 4.69 -3,5198 12.38899204 5,69 -2,5198 6,34939204 10,24 2,0302 4,12171204 10,27 2,0602 4.24442404 10,2 1,9902 3,96089604 14,89 6,6802 44,62507204 13,31 5,1002 26.01204004 16.29 8,0802 65,28963204 12.07 3,8602 14,90114404 8,497 0,2872 0,08248384 6,503 -1,7068 2,91316624 6,206 -2,0038 4.01521444 5,317 -2,8928 8,36829184 8.2098 555,1530216 3A x x - mean (x - mean)A 2 8.25 -0.0288333 0.00083136 4,1 -4,1788333 17,462648 3.6 -4,6788333 21.8914814 6,19 -2.0888333 4,36322469 6,68 -1.5988333 2,55626803 10,32 2.04116667 4,16636136 9.8 1,52116667 2,31394803 9.84 1,56116667 2,43724136 7.76 -0,5188333 0,26918803 9.32 1.04116667 1,08402803 9.76 1,48116667 2,19385469 11.82 3,54116667 12,5398614 10,79 2,51116667 6.30595803 8.73 0,45116667 0.20355136 10,78 2,50116667 6,25583469 11 10,26 1,98116667 3,92502136 9.48 1,20116667 1,44280136 6.84 -1,4388333 2.07024136 5,79 -2.4888333 6,19429136 5,75 -2.5288333 6.39499803 7.85 -0,4288333 0,18389803 8.33 0.05116667 0.00261803 11.31 3,03116667 9,18797136 8.25 -0,0288333 0,00083136 9,28 1.00116667 1,00233469 11.34 3.06116667 9,37074136 11.34 3,06116667 9.37074136 10.31 2,03116667 4.12563803 7.73 -0,5488333 0,30121803 5,15 -3,1288333 9,78959803 10.82 2,54116667 6.45752803 7,22 -1,0588333 1,12112803 4.64 -3,6388333 13,241108 6,18 -2,0988333 4,40510136 3,13 -5,1488333 26,5104847 2.6 -5.6788333 32.249148 2.08 -6,1988333 38.4255347 2.08 -6,1988333 38.4255347 7.33 -0.9488333 0,90028469 2 x x - mean (x - mean)A 2 6,67 -4.9135714 24.1431842 8.72 -2,8635714 8,20004133 8.73 -2,8535714 8,1428699 9.21 -2,3735714 5,63384133 10,3 -1,2835714 1,64755561 8.42 -3.1635714 10,0081842 7,9 -3.6835714 13,5686985 3.13 -8,4535714 71,4628699 7,33 -4.2535714 18,0928699 18.21 6.62642857 43,9095556 22,9 11,3164286 128,061556 16,95 5,36642857 28,7985556 12.42 0,83642857 0.69961276 21,28 9,69642857 94,020727 ,5835714 456,390121 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7.73 -0.5488333 0.30121803 7,24 -1,0388333 1.07917469 10,34 2.06116667 4.24840803 2,06 -6.2188333 38,673888 5,67 -2,6088333 6,80601136 9,77 1.49116667 2,22357803 15,52 7,24116667 52.4344947 8,33 0.05116667 0.00261803 5.66 -2,6188333 6,85828803 4.66 -3.6188333 13,0959547 4.14 -4.1388333 17.1299414 7.15 -1.1288333 1.27426469 6.73 -1.5488333 2,39888469 9.8 1,52116667 2.31394803 11,31 3,03116667 9.18797136 10,9 2,62116667 6,87051469 12,95 4.67116667 21.819798 12.84 4.56116667 20,8042414 10.85 2.57116667 6.61089803 7.66 -0.6188333 0,38295469 6,836 -1,4428333 2,08176803 12,685 4,40616667 19,4143047 11.23 2,95116667 8,70938469 8.474 0,19516667 0,03809003 12,647 4.36816667 19.08088 12,387 4.10816667 16.8770334 8,004 -0.2748333 0.07553336 8,27883333 589,937121 u1=tme mean of 4 sediments u2=true mean of 3B sediments m eanl =mean of 4 sediments mean2=mean of 3B sediments s1=standard deviation of 4 sediments s2=standard deviation of 3B sediments H; u1=u2 (there is no difference between %carbonate in 4 or 3B sediments , O A: u1#u2 (there Is significant difference between %carbonate in 4 and 3B sediments) n1=number of samples in 4 sediments n2=number of samples in 3B laminations x1= 4 sample x2= 3B sample We reject H in favor of A if |z|>za/2 where za/2=z0.05/2=z0.025=1,96 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. z=(mean1 -mean2)/sqrt((s1 A 2 /n1 )+(s2A 2/n2)) z= 3.01207191 |3,0120719|>1,96 so we reject H in favor of A At significance level 0.05 there is a significant difference between %carbonate in 4 and 3B sedim ents u1 =true mean of 4 sediments n1 =number of samples In 4 sediments u2=true mean of 3A sediments n2=number of samples in 3A sediments m eanl =mean of 4 sediments x1 = 4 sample mean2=mean of 3A sediments x2= 3A sample H: u1=u2 (there is no difference between %carbonate in 4 or 3A sediments A: u1#u2 (there Is significant difference between %carbonate In 4 and 3A sediments) We reject H In favor of A If |z|>za/2 where za/2zt0.05/2=z0,025J=1,96 z=(mean1-mean2)/sqrt((s1A 2 Zn1)+(s2A 2/n2)) z= 3.41244984 |3.14124498|>1.96 so we reject H In favor of A At significance level 0.05 there is a significant difference between %carbonate in 4 and 3A sedim ents u1 =true mean of 4 sediments n1 =number of samples In 4 sediments u2=tme mean of 4 sediments n2=number of samples in 2 sediments m eanl =mean of 4 sediments x1 = 4 sediment sample mean2=mean of 2 sediments x2= 2 sample H: u1=u2 (there is no difference between %carbonate in 4 or 2 sediments A: u1#u2 (there Is significant difference between %carbonate in 4 and 2 sediments) We reject H In favor of A if |z|>za/2 where za/2zt0,05/2=z0,025j=1,96 _ o z=(mean1 -mean2)/sqrt((s1 A 2 /n1 )+(s2A 2/n2)) 00 z- -2.57214 |-2.57214|>1,96 so we reject H in favor of A Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. At significance level 0.05 there Is a significant difference between %carbonate in 4 and 2 sediments s1=standard deviation of 3A sediments s2=standard deviation of 3B sediments H: u1=u2 (there Is no difference between %carbonate in 3A or 3B sediments A: u1#u2 (there is significant difference between %carbonate In 3A and fuzzy laminated sediments) W e reject H in favor of A if |z|>za/2 where zaf2=z0,05/2=z0.025=1.96 z=(mean1 -mean2)/sqrt((s1 A 2 /n1 )+(s2A 2/n2)) 0.17199458 (0.1719946|<1.96 so we accept H At significance level 0.06 there is no difference between %carbonate in 3A and 3B sediments u1=true mean of 3A sediments u2=true mean of 3B sediments n1=number of samples In 3A sediments n2=number of samples in 3B sediments m eanl =mean of 3A sediments mean2=mean of 3B sediments x1“ 3A sample x2= 3B sample z= u1=true mean of 3B sediments u2=true mean of 2 sediments n1-number of samples In 3B sediments n2=number of samples in 2 sediments m eanl =mean of 3B sediments mean2=mean of 2 sediments x1 = 3B sample x2= 2 sample H: u1=u2 (there is no difference between %carbonate in 3B or 2 sediments A: u1#u2 (there is significant difference between %caibonate In 3B and 2 sediments) We reject H in favor of A if |z|>za/2 where za/2zt0,05/2=z0,025=1.96 z=(mean1 -mean2)/sqrt((s1 A 2 /n1 )+(s2A 2/n2)) o 'O -4.5967709 |-4.5967709|<1,96 so we reject H in favor of A Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. At significance level 0.05 there Is a significance difference between %carbonate in 3B and 2 sediments u1 =true mean of 3A sediments n1 =number of samples in 3A sediments u2=tme mean of 2 sediments n2=number of samples in 2 sediments m eanl =mean of 3A sediments x1 = 3A sample mean2=mean of 2 sediments x2= 2 sample H: u1=u2 (there Is no difference between %carbonate in 3A or 2 sediments A: u1#u2 (there is significant difference between %carbonate In 3A and 2 sediments) W e reject H in favor of A if |z|>za/2 where za/2zt0.05/2=z0,025=1,96 z=(mean1 -mean2)/sqrt((s1 A 2 /n1 )+(s2A 2/n2)) z= -4.8262709 |-4.8262709|<1.96 so we reject H in favor of A At significance level 0.05 there Is a significance difference between %carbonate in 3A and 2 sediments Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. t-tests for CP %Organic Carbon 4 3B 3A X x - mean (x - mean)A 2 X x - mean (x - mean)A 2 X x - mean (x - mean)A 2 6,38 1.37072727 1,87889326 6,77 1.0705 1,14597025 7.36 2,27058333 5,15554867 5,387 0,37772727 0,14267789 5,871 0,1715 0.02941225 6.96 1,87058333 3.49908201 4.909 -0.1002727 0.01005462 4.758 -0,9415 0,88642225 6.22 1,13058333 1.27821867 6.227 1.21772727 1,48285971 5,35 -0,3495 0.12215025 2.93 -2.1594167 4,66308034 5.045 0.03572727 0,00127644 5.234 -0.4655 0.21669025 3.3 -1.7894167 3,20201201 3,95 -1,0592727 1.12205871 5,69 -0,0095 9.025E-05 4,515 -0,5744167 0,32995451 2.84 -2.1692727 4.70574417 5.91 0.2105 0.04431025 4.774 -0,3154167 0,09948767 5.33 0.32072727 0.10286598 6,013 0,3135 0.09828225 4,753 -0,3364167 0,11317617 5.12 0.11072727 0.01226053 5,6995 2,543328 5,257 0.16758333 0,02808417 5.082 0,07272727 0,00528926 4.718 -0,3714167 0,13795034 4.832 -0,1772727 0.03142562 4.848 -0,2414167 0.05828201 5,00927273 9.49540618 5,438 0.34858333 0,12151034 5.08941667 18.6863869 2 x - mean ( u1=true mean of bloturbated sediments n1=number of sam ples In bloturbated sediments u2=true mean of very fuzzy laminated sediments n2=number of samples in very fuzzy laminations m eanl =mean of bloturbated sediments x1=bioturbated sample mean2=mean of very fuzzy laminated sediments x2=very fuzzy lamination sample s1=standard deviation of bioturbated sediments s2=standard deviation of very fuzzy laminated sediments H: u1=u2 (there is no difference between %carbonate In bloturbated or very fuzzy laminated sediments A: u1#u2 (there is significant difference between %carbonate In bioturbated and very fuzzy laminated sediments) We reject H in favor of A if |t|>ta/2[n1 +n2-2] where ta/2[n1+n2-2]=t0.05/2[11+8-2J=t0,025[17]=2,110 t=(mean1 -mean2)/sqrt(((sum(x1 -m eanl )A 2+sum(x2-mean2)A 2)/(n1+n2-2))*((1 /n1 )+(1 /n2))) t= -1.7651869 (-1,7651869|<2.110 so we accept H |-1.7651869|>1,74 so we reject H in favor A At significance level 0.05 there is no difference between %organic carbon in bioturbated and very fuzzy laminated sediments - mean)A 2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. At significance level 0.1 there is a significance difference between %organic carbon in bioturbated and very fuzzy laminated sediments u1 =true mean of bioturbated sediments n1 =number of samples in bioturbated sediments u2=true mean of fuzzy laminated sediments n2=number of sam ples in fuzzy laminations m eanl =mean of bioturbated sediments x1 =bioturbated sample mean2=mean of fuzzy laminated sediments x2=fuzzy lamination sample H: u1=u2 (there is no difference between %carbonate in bloturbated or fuzzy laminated sediments A: u1#u2 (there is significant difference between %carbonate in bioturbated and fuzzy laminated sediments) W e reject H in favor of A if |t|>ta/2[n1 +n2-2] where ta/2[n1 +n2-2]=t0,05/2(11+12-2]=t0,025[21 ]=2,080 t=(mean1-mean2)/sqrt(((sum(x1-mean1)A 2+sum(x2-mean2)A 2)/(n1+n2-2))*((1/n1)+(1/n2))) t= -0.1657368 j-0,1657368|<2,080 so we accept H At significance level 0.0S there is no difference between %organic carbon in bioturbated and fuzzy laminated sediments u1 =true mean of fuzzy sediments n1=number of samples In fuzzy sediments u2=true mean of very fuzzy laminated sediments n2=number of samples in very fuzzy laminations m eanl =mean of fuzzy sediments x1=fuzzy sample mean2=mean of very fuzzy laminated sediments x2=very fuzzy lamination sample s1=standard deviation of fuzzy sediments s2=standard deviation of very fuzzy laminated sediments H; u1=u2 (there Is no difference between %carbonate in fuzzy or very fuzzy laminated sediments A: u1#u2 (there is significant difference between %carbonate In fuzzy and very fuzzy laminated sediments) We reject H in favor of A if |t|>ta/2[n1 +n2-2) where ta/2(n1+n2-2j=t0.05/2[12+8-2)=t0,025(18j=2,101 t=(mean1 -mean2)/sqrt(((sum(x1 -meanl )A 2+sum(x2-mean2)A 2)/(n1 +n2-2))*((1/n1)+(1/n2))) t= -1.2307616 |-1,2307616|<2,101 so we accept H At significance level 0.05 there is no difference between %organic carbon in fuzzy and very fuzzy laminated sediments Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. t-tests for FF %Opal W eight 3B 3A 2 X x - m ean (x - m ean )A 2 X x - m e a n (x - m e a n ) ^ X x - m ean (x - m e a n )A 2 10.581 -0.32948 0 ,1085570 7 13.46 6,4 3 8 4 1 6 6 7 41.4532092 10,001 -1.109 1,229881 9.1899 -1.72058 2 .96039554 7,297 0 ,27541667 0,07585434 12,219 1,109 1,229881 9.8475 -1,06298 1.12992648 5.9769 -1.0446833 1,09136327 11,11 2.459762 13.877 2 ,96652 8,80024091 5,704 -1 ,3175833 1,73602584 11,057 0.14652 0.02146811 5.0047 -2,0168833 4.06781838 10,91048 13,0205881 4 .6869 7.02158333 -2.3346833 5,45074627 53,8750173 u1= true m ean of 3B se d im e n ts n 1 = num ber of sa m p le s in 3B sed im en ts u2= true m ean of 3A se d im e n ts n 2 = num ber of sa m p le s in 3A sed im en ts m e a n l= m e a n of 3B se d im e n ts x1= 3B sam p le m ean 2 = m ean of 3A se d im e n ts x2= 3A sa m p le H: u1=u2 (there is no difference b etw een % opal w eight in 3B o r 3A sed im en ts A: u1#u2 (th ere is significant difference b etw een % opal w eight in 3B an d 3A sed im en ts) W e reject H in favor of A if |t|>ta/2[n1+n2-2] w h ere ta/2[n1+n2-2]=t0.05/2[5+6-2]=t0,025[9]=2,262 t= (m ean1-m ean 2 )/sq rt(((su m (x 1 -m ean 1 )''2 + su m (x 2 -m ean 2 )ft2)/(n1+n2-2))*((1/n1)+(1/n2))) t= 2,35 5 6 6 2 9 4 |2,3556629|> 2,262 so w e reject H in favor of A At significance level 0.05 there is a significant difference betw een %opal w eight in 3B and 3A sedim en ts u1=true mean of 3B sediments u2=true mean of 2 sediments n 1 = n u m b e ro f sa m p le s in 3B sed im en ts n2 = n u m b er of sa m p le s in 2 sed im en ts Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. m ean 1 = m ean of 3B sed im en ts x1= 3B sam ple m ean 2 = m ean of 2 sed im en ts x2= 2 sam p le H: u1=u2 (there is no difference b etw een % opal w eight in 3B or 2 sed im en ts A: u1#u2 (there is significant difference betw een % opal w eight in 3B an d 2 sed im en ts) W e reject H in favor of A if |t|>ta/2[n1+n2-2] w h ere ta/2[n1+n2-2]=t0.05/2[5+2-2]=t0,025[5]=2.571 t= (m ean1-m ean2)/sqrt(((sum (x1-m ean1)A 2+ su m (x 2 -m ean 2 )/'2)/(n1+n2-2))*((1/n1)+(1/n2))) t= -0.13 55289 |-0 ,13 5 5 2 8 9 |< 2 .5 7 1 so w e a c c e p t H At sig n ifica n ce lev el 0.05 th ere is no d ifferen ce b etw een % opal w eigh t in 3B and 2 se d im e n ts u1=true m ean of 3A sed im en ts n 1 = num ber of sa m p le s in 3A sed im en ts u2=true m ean of 2 sed im en ts n2= num ber of sa m p le s in 2 sed im en ts m ean 1 = m ean of 3A sed im en ts x1= 3A sam p le m ean 2 = m ean of 2 sed im en ts x2= 2 sam p le H: u1=u2 (th ere is no difference b etw een % opa| w eight in 3A o r 2 sed im en ts A: u1#u2 (there is significant difference b etw een % opal w eight in 3A an d 2 sed im en ts) W e reject H in favor of A if |t|>ta/2[n1+n2-2] w h ere ta/2[n1+n2-2]=t0.05/2[6+2-2]=t0.025[6]=2.447 t= (m ean 1 -m ean 2 )/sq rt(((su m (x 1 -m ean 1 )A 2+ su m (x 2 -m ean 2 )A 2)/(n1+n2-2))*((1/n1)+(1/n2))) t= -1.6341357 (-1,6341357|< 2.447 so w e a c c e p t H At sig n ifica n ce le v e l 0.05 th ere is n o d ifferen ce b etw een % opal w eig h t in 3A and 2 se d im e n ts Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. t-tests for FF %Carbonate very fuzzy laminations fuzzy laminations laminations X x - mean (x - mean)A 2 X x - mean (x - mean)A 2 X x - mean ;x - mean)A 2 10.74 1,9825 3.93030625 8.508 2,2273333 4,96101378 9.6 0.3774286 0.1424523 8.48 -0.2775 0.07700625 6.24 -0.040667 0.00165378 8,838 -0,384571 0,1478952 6,895 -1.8625 3.46890625 9.69 3.4093333 11.6235538 9,36 0.1374286 0.0188866 6.831 -1.9265 3.71140225 10.571 4.2903333 18.4069601 6.28 -2.942571 8,6587266 6.818 -1.9395 3.76166025 6,15 -0,130667 0,01707378 8,94 -0.282571 0.0798466 7.62 -1.1375 1,29390625 10,51 4.2293333 17.8872604 12,84 3.6174286 13,085789 10.586 1.8285 3,34341225 10.1 3,8193333 14.5873071 8.7 -0.522571 0,2730809 9.065 0.3075 0,09455625 9.03 2.7493333 7.55883378 9.2225714 22.406678 9.33 0.5725 0,32775625 7.66 1.3793333 1.90256044 11.21 2.4525 6,01475625 8.317 2.0363333 4,14665344 8.7575 26,0236685 10.308 4.0273333 16.2194138 10.452 4,1713333 17.4000218 9,532 3.2513333 10.5711684 8,85 2.5693333 6.60147378 9.451 3.1703333 10.0510134 6.2806667 141.935962 u1 =true mean of 3B sediments n1 =number of samples in 3B sediments u2=true mean of 3A sediments n2=number of samples in 3A samples meanl =mean of 3Bsediments x1 = 3B sample mean2=mean of 3A sediments x2= 3A sample H : u1=u2 (there is no difference between %carbonate in 3B or 3A sediments Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A : u1#u2 (there is significant difference between %carbonate in 3B and 3A sediments) We reject H in favor of A if |t|>ta/2[n1+n2-2] where ta/2[n1+n2-2]=t0.05/2[10+15-2]=t0.025[23]=2.069 t=(mean1-mean2)/sqrt(((sum(x1 -meanl )A 2+sum(x2-mean2)A 2)/(n1+n2-2))*((1/n1)+(1/n2))) t= 2.2450906 |2.2450906|>2.069 so we reject H in favor of A At significance level 0.05 there is a significance difference between %carbonate in 3B and 3A sediments u1 =true mean of 3B sediments n1 =number of samples in 3B sediments u2=true mean of 2 sediments n2=number of samples in 2 sediments meanl =mean of 3B sediments x1 = 3B sample mean2=mean of 2 sediments x2= 2 sample H : u1=u2 (there is no difference between %carbonate in 3B or 2 sediments A : u1#u2 (there is significant difference between %carbonate in 3B and 2 sediments) We reject H in favor of A if |t|>ta/2[n1+n2-2] where ta/2[n1+n2-2]=t0,05/2[10+7-2]=t0.025[15]=2,131 t=(mean1-mean2)/sqrt(((sum(x1-mean1)A 2+sum(x2-mean2)A 2)/(n1+n2-2))*((1/n1)+(1/n2))) t= -0.525208 |-0.5252077|<2,131 so we accept H At significance level 0.05 there is no difference between %carbonate in 3B and 2 sediments u1=true m ean of 3A sedim ents u2=true m ean of 2 sedim ents n1=number of samples in 3A sediments n2=number of samples in 2 sediments Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. meanl =mean of 3A sediments x1 = 3A sample mean2=mean of 2 sediments x2= 2 sample H : u1=u2 (there is no difference between %carbonate in 3A or 2 sediments A : u1#u2 (there is significant difference between %carbonate in 3A and 2 sediments) We reject H in favor of A if |t|>ta/2[n1+n2-2] where ta/2[n1 +n2-2]=t0,05/2(15+7-2]=t0.025[20]=2.086 t=(mean1-mean2)/sqrt(((sum(x1-mean1)A 2+sum(x2-mean2)A 2)/(n1+n2-2))*((1/n1)+(1/n2))) t= -2.242084 |-2,2420835|>2,086 so we reject H in favor of A At significance level 0.05 there is a significant between %carbonate in 3A and 2 sediments — j Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. t-tests for FF %Organic Carbon 3B 3A 2 X x - mean ;x - mean)A 2 X x - mean |x - mean)A 2 X x - mean |x - mean)A 2 2.696 -0.1444 0.0208514 3,073 0.4406667 0.1941871 2.9 0.1413333 0.0199751 3 0.1596 0.0254722 2,92 0.2876667 0,0827521 2,312 -0,446667 0,1995111 2,399 -0,4414 0,194834 3,18 0.5476667 0,2999388 3,54 0.7813333 0,6104818 2.127 -0,7134 0,5089396 3,95 1,3176667 1,7362454 2.55 -0,208667 0.0435418 2.535 -0,3054 0.0932692 2,84 0,2076667 0,0431254 2.93 0,1713333 0.0293551 2.51 -0.3304 0.1091642 3.3 0,6676667 0.4457788 2,32 -0,438667 0.1924284 3.19 0.3496 0.1222202 2,337 -0,295333 0.0872218 2.7586667 1,0952933 2.796 -0,0444 0,0019714 1,948 -0.684333 0,4683121 3,881 1.0406 1,0828484 1,961 -0.671333 0.4506884 3.27 0.4296 0,1845562 2.778 0,1456667 0,0212188 2.8404 2,3441264 3,1 1.74 2.064 2.25 2.044 0,4676667 -0.892333 -0,568333 -0.382333 -0.588333 0.2187121 0,7962588 0,3230028 0.1461788 0.3461361 2.6323333 5.6597573 u1 =true mean of 3B sediments n1 =number of samples in 3B sediments u2=true mean of 3A sediments n2=number of samples in 3A sediments meanl =mean of 3Bsediments x1 = 3B sample mean2=mean of 3A sediments x2= 3A sample H : u1=u2 (there is no difference between %organic carbon in 3B or 3A sediments A : u1#u2 (there is significant difference between %organic carbon in 3B and 3A sediments) 118 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. We reject H in favor of A if |t|>ta/2[n1 +n2-2] where ta/2[n1+n2-2]=t0,05/2[10+15-2]=t0.025[23]=2,069 t=(mean1-mean2)/sqrt(((sum(x1-mean1)A 2+sum(x2-mean2)A 2)/(n1+n2-2))*((1/n1)+(1/n2))) t= 0,8639561 |0.86395611 <2.069 so we accept H At significance level 0.05 there is no difference between %organic carbon in 3B and 3A sediments u1 =true mean of 3B sediments n1 =number of samples in 3B sediments u2=true mean of 2 sediments n2=number of samples in 2 sediments meanl =mean of 3B sediments x1 = 3Bsample mean2=mean of 2 sediments x2= 2 sample H : u1=u2 (there is no difference between %organic carbon in 3B or 2 sediments A : u1#u2 (there is significant difference between %organic carbon in 3B and 2 sediments) We reject H in favor of A if |t|>ta/2[n1+n2-2] where ta/2[n1+n2-2]=t0.05/2[10+6-2]=t0,025[14]=2,145 t=(mean1 -mean2)/sqrt(((sum(x1 -meanl )A 2+sum(x2-mean2)A 2)/(n1 +n2-2))*((1/n1 )+(1/n2))) t= 0.3193275 |0.3193275|<2.145 so we accept H At significance level 0.05 there is no difference between %organic carbon in 3B and 2 sediments u1 =true m ean of 3A sedim ents n1 =number of sam ples in 3A sedim ents ^ u2=true m ean of 2 sedim ents n2=number of sam ples in 2 sedim ents ~ m eanl =m ean of 3A sedim ents x1 = 3A sam ple Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. mean2=mean of 2sediments x2= 2 sample H : u1=u2 (there is no difference between %organic carbon in 3A or 2 sediments A : u1#u2 (there is significant difference between %organic carbon in 3A and 2 sediments) We reject H in favor of A if |t|>ta/2[n1+n2-2] where ta/2[n1+n2-2]=t0,05/2[15+6-2]=t0.025[19]=2,093 t=(mean1 -mean2)/sqrt(((sum(x1 -meanl )A 2+sum(x2-mean2)A 2)/(n1 +n2-2))*(( 1 /n1)+(1 /n2))) t= -0.438624 |-0.436237|<2,093 so we accept H At significance level 0.05 there is no difference between %organic carbon in 3A and 2 sediments to o t-tests for CPand F F %opal weight 121 o C D CM < C C O C D E T - CD t o CD M O CO O c o c n cm r r CD CO 0 5 CM CO O 0 5 O O CD CM O t - 0 5 -c - 0 0 U . ffl L L C O c CO o CM T~ G O o CD CO c o C M C M ■ ^ r m 0 5 to CO 0 5 o C M CD CD CM C O CM l". 8 $ ’T o 1 1 i cm' o' 0 5 to f '- 1^- CO 0 5 r*- r^- CO c n CO 00 o o' T — CD co' T— 0 5 ' O i T — T — T - CD CO CO CD CD M" O t - CM CM O O co c o o 0 5 O 00 C D CO 0 5 M CM CD O 0 5 CM i CM t - X CM ' o ' c co 05 E CM CO CM CM 0 5 CD CM 0 5 I — CM 0 5 t- t - CD CO ID T - T - o CO o ' o o 0 5 C O C O o o ' N 0 0 CO t — r— c o 0 5 CO CM CD CO CO 0 5 N ( 3 1 CO o o CO o CM o o 0 5 CO S CO CO ID CM CM N CN ID CO CO CD CM CD M - CM CM 0 5 CO o CO O CM O ' O ^ CM CO N O O ID OL f f i O c o — CM-*- t - C M t— t - t - t- t— C M C M t— E O 5 C 0 C 0 C D 0 5 C O C O C D C M C D 0 5 0 5 C0 S c D C O C O C n C D C O C O C n i D l D C O C D C O t— C 0 I D C M I D C D C M O 5 M t — C M t— CO E iD ^ rc o ffiT -c o c o M n T -o o s C O ( N | M N C M I D ( M ' T C M I O U 5 I D i o ’ o ' o ' ° . o ’ o ' o ' o ' o ’ I I Q I I I I I I D CO M- iDcoTrm^rM’ S N T -N i- C M C D C M O O t — C M C M C O C O C M O t— C O O 5 C D C O O 5 C D O 5 C M C p C 0 cm' o ' o ' S o ' o ' c m i o o i m o o o CD CD CO CD CO O ' CO CO o' 0 0 ° 0 5 o CM CL o LL _ c LL 05 C c 0) 05 C D E Q . TJ E C D C D 05 05 CQ CQ CO CO c c 05 05 C D C D Q . Q . E E CD CD 05 05 » ! ta— O o i_ o (D JD X! E E 3 3 C C II II CM C C ^ CM U . JL 0 . L L . O L L c c < n c/5 -t— • . — • c c C D C D E E tj "a C D C D C/5 C/5 m m c o c o o c CD C D C D CD E E C D C D 3 33 i i_ IT "if r - CM 3 3 a . Li_ O L L . c c 0) 05 a . o . E E CD CD C/5 C/5 C Q C D CO CO II II X ^ Q_ LL O u . c .c c/5 co c c CD © E E 10 io CD CD co co C D C D CO CO * ♦ — u— o o c c r CD CD CD (D E E 1 1 I I t - CM c c CD CD CD CD E E LL. Li. i_ O C L O c c CD E T 3 C D C O C Q CO g > '<D £ CO CL O c C D C D £ CD JO CD 0 c CD 1 ____ CD fc T3 O C CO CD I — C D CM 3 I I 1 5 x T 3 C C D Q . O c c C D E T O C D C O C D CO _ c o g > '(D $ C D Q . O C C D C D © s c © I c 03 o c O) * 0 05 0 0 CM 3 T“ 3 < to in' C M o o TT CM I to + CM r » CM IO O O TT C M I CM c + d C M Is 0 L_ 0 J3 £ C M i CM d + c _ CM 2 7 T < o o > 03 C X o 0 * 0 L_ 0 C M d CM i C M d + CM < C M * C 0 0 E % E 3 0 + CM < v C 0 0 E E 3 0 tT c r 0 CM d 0 0 E i c C D C D E . n ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. -9.178894 |-9,1788935|<2,160 so we reject H in favor of A At significance level 0.05 there is a significant difference between %opal weight in 3B sediments in CP and FF CP FF 3A 3A X x - mean |x - mean)A 2 x x - mean |x - mean)A 2 4.377 2.963432 8,7819292 13.46 6.4384167 41.453209 3.089 1.675432 2.8070724 7.297 0.2754167 0,0758543 0.61 -0.803568 0,6457215 5,9769 -1,044683 1,0913633 0.786 -0.627568 0,3938416 5,704 -1,317583 1,7360258 1.108 -0,305568 0,0933718 5.0047 -2.016883 4.0678184 1.372 -0.041568 0.0017279 4,6869 -2,334683 5,4507463 1.39 -0.023568 0,0005555 7.0215833 53.875017 0.873 -0.540568 0.2922138 0.471 -0.942568 0,8884344 1.532 0.118432 0,0140261 1.1257 -0.287868 0.082868 1.8079 0.394332 0,1554977 1.6989 0,285332 0.0814144 0.86167 -0.551898 0.3045914 0,75622 -0.657348 0.4321064 0.627 -0.786568 0,6186892 0.92987 -0.483698 0.2339638 2.5601 1,146532 1.3145356 1.66 0.246432 0.0607287 0.636 -0.777568 0,604612 1.413568 17.807901 u1=true mean of 3A sediments in CP u2=true mean of 3A sediments in FF meanl =mean of 3A sediments in CP mean2=mean of 3A sediments in FF n1=number of sam ples in 3A sedim ents in CP n2=number of sam ples in 3A sam ples in FF x1= 3Asample in CP x2= 3A sample in FF to to Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. H : u1 =u2 (there is no difference between %opal weight in 3A sediments in CP or FF A : u1#u2 (there is significant difference between %opal weight in 3A sediments in CP and FF) We reject H in favor of A if |t|>ta/2[n1 +n2-2] where ta/2[n1+n2-2]=t0,05/2(17+7-2]=t0.025[22]=2,074 t=(mean1 -mean2)/sqrt(((sum(x1 -meanl )A 2+sum(x2-mean2)A 2)/(n1 +n2-2))*((1 /n1 )+(1 /n2))) t= -7.979849 |-7,97984911>2.074 so we reject H in favor of A At significance level 0.05 there is a significance difference between %opal weight in 3A sediments in CP and FF IO Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. t-test for CP and FF %carbonate CP FF 3B 3B X x-mean ;x-mean)A S X x-mean ' ( x-mean)A 2 11.36 3.1502 9.92376 10,74 1,9825 3,9303063 15.99 7.7802 60,531512 8,48 -0.2775 0.0770062 5.16 -3.0498 9.30128 6,895 -1.8625 3,4689063 2,58 -5.6298 31.694648 6,831 -1,9265 3.7114022 2.06 -6.1498 37.82004 6.818 -1.9395 3,7616603 6.15 -2.0598 4.242776 7.62 -1,1375 1,2939063 2.05 -6,1598 37.943136 10,586 1,8285 3.3434123 5,32 -2,8898 8.350944 9,065 0,3075 0,0945563 3.64 -4.5698 20.883072 9,33 0,5725 0.3277563 4.65 -3,5598 12.672176 11.21 2.4525 6.0147563 5.64 -2,5698 6.603872 8,7575 26,023669 4.6 -3.6098 13,030656 11.97 3.7602 14.139104 9.31 1,1002 1.21044 15.41 7.2002 51.84288 6,66 -1.5498 2,40188 3,56 -1.5498 2.40188 12.35 4,1402 17.141256 8,29 0.0802 0.006432 6.73 -1.4798 2,189808 11.87 3.6602 13.397064 7.82 -0.3898 0.151944 4.69 -3.5198 12,388992 5.69 -2.5198 6.349392 10.24 2.0302 4.121712 10.27 2.0602 4.244424 10.2 1,9902 3.960896 14.89 6,6802 44.625072 13.31 5,1002 26,01204 16.29 8.0802 65.289632 to Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. 12,07 3.8602 14.901144 8.497 0.2872 0.0824838 6,503 -1.7068 2.9131662 6.206 -2,0038 4.0152144 5.317 -2.8928 8,3682918 8,2098 555,15302 u1=true mean of 3B sediments in CP n1=number of samples in 3B sediments in CP u2=true mean of 3Bsediments in FF n2=number of samples in 3B samples in FF meanl =mean of 3B sediments in CP x1 = 3B sample in CP mean2=mean of 3B sediments in FF x2= 3Bsample in FF s1=standard deviation of 3B sediments in CP s2=standard deviation of 3B sediments in FF H : u1=u2 (there is no difference between %carbonate in 3B sediments in CP or FF A : u1#u2 (there is significant difference between %carbonate in 3B sediments in CP and FF) We reject H in favor of A if |z|>za/2 where za/2=z0.05/2=z0.025=1,96 z=(mean1-mean2)/sqrt((s1 A 2 /n1 )+(s2A 2/n2)) z= -1.025045 |-1.0250446|<1.96 so we accept H At significance level 0.05 there is no difference between %carbonate in 3B sediments in CP and FF CP FF 3A 3A x x-m ean |x-mean)A 2 x x-m ean |x-mean)A 2 8,25 -0.028833 0.0008314 8.508 2,2273333 4,9610138 4.1 -4.178833 17.462648 6.24 -0.040667 0.0016538 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.6 -4,678833 21.891481 9,69 3,4093333 11,623554 6.19 -2,088833 4.3632247 10.571 4.2903333 18.40696 6,68 -1,598833 2.556268 6,15 -0,130667 0,0170738 10,32 2.0411667 4.1663614 10.51 4.2293333 17,88726 9,8 1.5211667 2.313948 10.1 3,8193333 14,587307 9.84 1.5611667 2.4372414 9.03 2.7493333 7.5588338 7.76 -0,518833 0.269188 7,66 1.3793333 1,9025604 9.32 1.0411667 1,084028 8.317 2,0363333 4,1466534 9.76 1.4811667 2.1938547 10,308 4.0273333 16,219414 11.82 3.5411667 12,539861 10,452 4,1713333 17.400022 10.79 2.5111667 6,305958 9.532 3,2513333 10.571168 8.73 0.4511667 0,2035514 8,85 2,5693333 6,6014738 10,78 2.5011667 6,2558347 9,451 3,1703333 10,051013 10.26 1,9811667 3.9250214 6.2806667 141,93596 9.48 1.2011667 1,4428014 6.84 -1,438833 2.0702414 5.79 -2.488833 6.1942914 5,75 -2,528833 6.394998 7.85 -0.428833 0.183898 8.33 0.0511667 0.002618 11.31 3.0311667 9.1879714 8,25 -0,028833 0,0008314 9.28 1.0011667 1,0023347 11.34 3.0611667 9.3707414 11.34 3,0611667 9.3707414 10.31 2.0311667 4.125638 7.73 -0.548833 0.301218 5.15 -3.128833 9,789598 10,82 2.5411667 6,457528 7,22 -1,058833 1,121128 4.64 -3,638833 13.241108 6.18 -2,098833 4.4051014 3.13 -5,148833 26.510485 2,6 -5,678833 32,249148 2.08 -6,198833 38.425535 2.08 -6.198833 38.425535 t o O N Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7.33 -0,948833 0,9002847 7,73 -0.548833 0,301218 7,24 -1.038833 1.0791747 10,34 2,0611667 4.248408 2,06 -6.218833 38.673888 5,67 -2,608833 6.8060114 9.77 1.4911667 2.223578 15,52 7,2411667 52,434495 8,33 0.0511667 0.002618 5,66 -2.618833 6,858288 4,66 -3,618833 13,095955 4.14 -4.138833 17.129941 7.15 -1,128833 1.2742647 6.73 -1,548833 2,3988847 9.8 1.5211667 2.313948 11.31 3.0311667 9.1879714 10.9 2.6211667 6.8705147 12,95 4.6711667 21,819798 12.84 4.5611667 20.804241 10.85 2.5711667 6.610898 7.66 -0,618833 0.3829547 6.836 -1.442833 2.081768 12,685 4.4061667 19.414305 11.23 2.9511667 8.7093847 8.474 0.1951667 0.03809 12.647 4,3681667 19.08088 12.387 4.1081667 16.877033 8.004 -0.274833 0.0755334 8.2788333 589.93712 u1=true mean of 3A sediments in CP u2=true mean of 3A sediments in FF meanl =mean of 3A sediments in CP mean2=mean of 3A sediments in FF n1=number of sam ples in 3A sedim ents in CP n2=number of sam ples in 3A sam ples in FF x1= 3A sample in CP x2= 3A sample in FF Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. s1=standard deviation of 3A sediments in CP s2=standard deviation of 3A sediments in FF H ; u1=u2 (there is no difference between %carbonate in 3A sediments in CP or FF A : u1#u2 (there is significant difference between %carbonate in 3A sediments in CP and FF) We reject H in favor of A if |z|>za/2 where za/2=z0,05/2=z0,025=1,96 z=(mean1-mean2)/sqrt((s1A 2 /n1)+(s2A 2/n2)) z= 3.9345191 |3.93451911 > 1 ,96 so we reject H in favor of A At significance level 0.05 there is a significance difference between %carbonate in 3A sediments in CP and FF CP FF 2 2 X x - mean |x - mean)A 2 X x - mean |x - mean)A 2 6.67 -4.913571 24.143184 9.6 0.3774286 0.1424523 8.72 -2.863571 8.2000413 8,838 -0.384571 0,1478952 8.73 -2.853571 8.1428699 9,36 0.1374286 0,0188866 9.21 -2.373571 5.6338413 6.28 -2,942571 8.6587266 10.3 -1,283571 1.6475556 8.94 -0.282571 0,0798466 8.42 -3.163571 10,008184 12.84 3.6174286 13.085789 7.9 -3,683571 13.568698 8.7 -0,522571 0.2730809 3.13 -8.453571 71.46287 9,2225714 22.406678 7.33 -4.253571 18.09287 18.21 6.6264286 43.909556 22,9 11.316429 128,06156 16,95 5.3664286 28.798556 12.42 0.8364286 0.6996128 21.28 9.6964286 94.020727 583571 456.39012 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. u1=true mean of 2 sediments in CP u2=true mean of 2 sediments in FF n1=number of samples in 2 sediments in CP n2=number of samples in 2 samples in FF meanl =mean of 2 sediments in CP mean2=mean of 2 sediments in FF x1= 2 sample in CP x2= 2 sample in FF H : u1=u2 (there is no difference between %carbonate in 2 sediments in CP or FF A : u1#u2 (there is significant difference between %carbonate in 2 sediments in CP and FF) We reject H in favor of A if |t|>ta/2[n1+n2-2] where ta/2[n1+n2-2]=t0,05/2[14+7-2]=t0,025(19]=2,093 t=(mean1 -mean2)/sqrt(((sum(x1 -meanl )A 2+sum(x2-mean2)A 2)/(n1 +n2-2))*((1/n1 )+(1/n2))) t= 1.016016 |1.016016|<2.093 so we accept H At significance level 0.05 there is no difference between %carbonate in 2 sediments in CP and FF to Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. t-tests for CPand FF %organic carbon CP FF 3B 3B X X -mean ;x-mean)A 2 X x-m ean |x-mean)A 2 6.77 1.0705 1,1459703 2,696 -0.1444 0,0208514 5.871 0.1715 0.0294123 3 0,1596 0.0254722 4.758 -0.9415 0.8864222 2.399 -0.4414 0.194834 5,35 -0.3495 0.1221503 2.127 -0.7134 0,5089396 5.234 -0.4655 0.2166903 2,535 -0,3054 0,0932692 5.69 -0,0095 9.025E-05 2.51 -0.3304 0.1091642 5,91 0.2105 0.0443103 3.19 0.3496 0.1222202 6.013 0.3135 0.0982823 2.796 -0.0444 0.0019714 5,6995 2.543328 3.881 1,0406 1.0828484 3.27 0.4296 0.1845562 2.8404 2.3441264 true mean o f 3B sediments in CP n1=number o f samples in u2=true mean of 3B sediments in FF meanl =mean of 3B sediments in CP mean2=mean of 3B sediments in FF n2=number of samples in 3B samples in FF x1 = 3B sample in CP x2= 3B sample in FF H : u1=u2 (there is no difference between %organic carbon in 3B sediments in CP or FF A : u1#u2 (there is significant difference between %organic carbon in 3B sediments in CP and FF) We reject H in favor of A if |t|>ta/2[n1+n2-2] where ta/2[n1+n2-2]=t0.05/2[8+10-2]=t0.025[16]=2.120 t=(mean1-mean2)/sqrt(((sum(x1-meanl )A 2+sum(x2-mean2)A 2)/(n1+n2-2))*((1/n1)+(1/n2))) t= 10.90578 |10.90578|>2,120 so we reject H in favor of A At significance level 0.05 there is a significant difference between %organic carbon in 3B sediments in CP and FF 131 u . < L L. C O < * t _ r - -p 5 « ® £ g IT C M E C D C D . t- O x . o o ' r— r— ^ C D c o 5 CO CO ® CO CD E o r~ , •o- co ' - T C M o o ' r - o x co CD GO •ta CO CO T — ■o- CO T — 00 CO CO T— CO CO LO i n CO C M 00 CO C M CO C M CO CO r - CO C M f> - C M CO T — t n O CO t o C D C M T — r - C M CO 8 C M 1^- C M O T — C D CO CO m r - CO c o CO CO CO CO < D C D CO • t r • t r c o CO m C M T— CD C M M" ^ 3 - i n CM r - - 0 • t r 0 TT ■sr O C M I - - CO t - c o CD O T ~ o ' 0 0 0 o ' o ' o ' o ' o ' o ' 0 i d CO CO h - . 8 r - c 0 CD 1 ^ - c o CO CO CO CO CO CO CO CO CO CO CD CO l" - CD CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO t n M- T“ CO CO CM 0 0 C M 0 0 r - . 1 — f - r - - CD 0 0 I - - IO CD CD CO OO O CO C M CO c o t r CO CO t n CO c o t o CO C M CO o ' o ' o ' t j - o ' o ' o ' 0 0 1— o ' o ' t t t o ' O t 1 1 1 00 i n t r CO 1"- CO CO T- T m - t o CO CO CD c o ' 0 0 cm' c o ' c o CO C M M- CD i — CO CD r - - cm' c o ' CO 0 c m' C M C M * O C M * CO CO CO C M C O C O C M < * S CM I— CO •C O CD CO O TJ" O f - CO in CD CM o IO CD 0 0 CO I f i 'T I — CO P CO' P P i n ■ < - "cr c C D © E C M C O t— C M O C O C O N- C M C D O’ t- O C D C D C O C M C M C D C M C O C M C O N O’ O C O o oo co in cm t- co O C D C O to C O CO i CO 00 1 ^- to CM CO O P o o o CL < O o _ C O C O C O s c C O C O C O T- s C O C O 00 M- 2 to IO to C D E o o o to , r*- co 1 — x P T _- c m ' ( M r r 1 C D C D C M C O C O C D C M C D C O co' cm ' O T - o o ' r^ . i - - - c- s- TT V T T T C D M " IO C O oo r— r - co _ . N tO C O C O C O C O C M T-' o o ' o ’ P o ' o ' CO N N C O r r - 00 M- M to T- T- r * - r- - t a - c o cm co P c o o T - co co o o to CO i-s co to t r co n co oo r N IO IO r t f C J l O f ' - N -C M p 0 0 M " M " t ' in' tT Tf 0 0 r - ~ - CO CO t— 10 cn co o to' 0 . 0 LL c LL i s g c 0 < D 0 E CL X ) E < D 0 C O 0 < < C O C O c _g C O 0 C D 0 CL CL E E C D 0 < n 0 ^ — 0 0 u . L_ 0 0 m X ) E E 3 3 c c 1 1 1 1 T— CM c C Q _ L L 0 LL c g < o c o c c C D C D E E TO TO 0 0 C O C O < < co co ‘o ‘o c c 0 0 0 0 E E 0 0 3 3 1 u T ¥ t - CM 3 3 LL l l u . o 0. o .g — — C O c 0 E T 3 0 C O < CO c Cl ll O L l .g _g 0 0 CL CL E E 0 0 0 0 < < C O C O 1 1 II ~ > < s CL LL O LL g g 0 0 c c 0 0 E E TO TO 0 0 0 0 < < CO CO o o c c 0 0 0 0 E E ii i i t- CM c c 0 0 0 0 E E TO C 0 C L O c c 0 E T O 0 0 < CO c o JO s 8 c o JO s g c 0 CD c 0 I 0 JO 0 O c £ fc TO 0 c 0 £ 0 £ C M 3 II 3 1 g ' c 0 CD 1 _____ O 'S o ’ c 0 0 M a) .D a> 0 c C D 1 TJ C I 'E C T > '0 0 0 L_ 0 £ CM 3 % r * 3 < Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. W e reject H i n favor o f A i f |t|>ta/2[n1+n2-2] w here ta/2[n1+n2-2]=t0.05/2[13+15-2]=t0.025[26]=2.056 t=(mean1-mean2)/sqrt(((sum(x1-mean! )A 2+sum(x2-mean2)A 2)/(n1+n2-2))*((1/n1)+(1/n2))) 132 T J C CO Q . O JZ CO c © E © CO < n c c o ■ e (0 o c CO c n © a > © n © u c £ £ < * — 0 1 _ o > .2 c X a < D ' © i — 0 o C O ID C O O c m ' A CO OO £ £ S I CO g O O ° 2 h - I "- . IL co c o _ c CQ U I ? c g > ’ 3 3 c o « £ a > x: to o © ■© > © u c CQ u c 'E .5* ' c / 3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. IMAGE EVALUATION TEST TARGET (Q A -3 ) A ✓ A « / r 1 . 0 l.l I« I I I ^ *2 - lii IJJj m t I n £ 3^ l i i I I 2.2 12.0 1 .8 1.25 1.4 1 . 6 1 5 0 m m I M / 4 GEE . I n c 1653 East Main Street Rochester, NY 14609 USA Phone: 716/482-0300 Fax: 716/288-5989 O 1993. Applied Image. Inc., All Rights R eserved Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
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De Diego, Teresa Ann
(author)
Core Title
Oxygen-related biofacies in slope sediment from the Western Gulf of California, Mexico
Degree
Master of Science
Degree Program
Geological Sciences
Publisher
University of Southern California
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University of Southern California. Libraries
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Geology,OAI-PMH Harvest,paleoecology
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English
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https://doi.org/10.25549/usctheses-c16-26936
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De Diego, Teresa Ann
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The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...
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paleoecology