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Sedimentology of a composite inner-shelf sand body resulting from the resuspension of nearshore sediment by episodic, storm-generated currents: Oceanside, California

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Sedimentology of a composite inner-shelf sand body resulting from the resuspension of nearshore sediment by episodic, storm-generated currents: Oceanside, California

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Content SEDIMENTOLOGY OF A COMPOSITE INNER-SHELF SAND BODY RESULTING FROM THE RESUSPENSION OF NEARSHORE SEDIMENT BY EPISODIC, STORM-GENERATED CURRENTS: OCEANSIDE CALIFORNIA by Kyung Ha Cho 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 SCIENCE (Geological Sciences) May 1989 Copyright 1989 Kyung Ha Cho UMI Number: EP58803 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. UMI Dissertation Publishing UMI EP58803 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 UNIVERSITY OF SOUTHERN CALIFORNIA THE GRADUATE SCHOOL UNIVERSITY PARK LOS ANGELES. CALIFORNIA 90 0 0 7 This thesis, written by under the direction of Thesis Committee, and approved by a ll its members, has been p re sented to and accepted by the D ean of The Graduate School, in p a rtial fu lfillm en t of the requirements fo r the degree of *89 C 5 4 S Kyung Ha Cho Master of Science Dean D a te February ^8, 1989 THESIS COMMITTEE Chairman For iMy Family and Sabina i i TABLE OF CONTENTS Page LIST OF FIGURES................................................. v LIST OF TABLES vi i ABSTRACT.....................................................vi i i INTRODUCTION....................................................1 METHODS..........................................................9 Sample Collection............................................9 Sample Preparation for Fourier Grain-Shape Analysis... 13 Fourier Methodology........................................16 Statistical Analysis................................... 18 Cluster Analysis........................................ 19 Factor Analysis......................................... 20 Discriminant Function Analysis........................21 QUATERNARY STRATIGRAPHY OF THE OCEANSIDE AREA............ 22 STRATIGRAPHY AND SEDIMENTARY STRUCTURES OF VIBRACORES...27 Stratigraphy of Vibracores................................27 Sedimentary Structures.....................................28 GRAIN-SIZE CHARACTERISTICS OF AGGRADATIONAL AREA.........36 FOURIER GRAIN-SHAPE ANALYSIS................................42 Results and Interpretation................................42 Identification of Sand from Beach Nourishment Project Completed by May 1982........................ 72 Identification of Sand from Beach Nourishment Project Completed by March 1984 .......................75 DISCUSSION.....................................................76 CONCLUSION.....................................................85 REFERENCES.....................................................87 APPENDIX A: VIBRACORE LOGS AND SEDIMENT DESCRIPTIONS....93 i v LIST OF FIGURES Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Location map Page . . 3 Map showing historical changes in topography offshore of Oceanside between 1934 and 1971-72 (from Tekmarine, Inc., 1986 , p. 65).......................................5 Sample location map............................ 14 Panel diagram showing the microstratigraphic relationships among the vibracores recovered offshore of Oceanside, California............30 Mean phi grain-size values for sediment samples from the recovered vibracores. The predominant offshore fining trend can be discerned from the 3.25 phi and 3.50 phi contours......................................... 39 Dendrogram of the eleven vibracore samples (ISB = inner sand body facies; MBA = modern beach affinities; OSB = outer sand body fac ies).......................................... 44 Dendrogram of the two sand body facies and four cliff samples (ISB = inner sand body facies; OSB = outer sand body facies)....... 46 Dendrogram of the two sand body facies and beach samples north of the Santa Margarita River (ISB = inner sand body facies; OSB = outer sand body facies).......................49 Dendrogram of the two sand body facies and beach samples south of the Santa Margarita River (ISB = inner sand body facies; OSB = outer sand body facies).......................51 Dendrogram of the two sand body facies and the 1981 beach samples with the Santa Margarita River and San Luis Rey River samples (ISB = inner sand body facies; OSB = outer sand body facies).......................53 v Figure 12. Figure 13. Figure 14. Figure 15. Figure 16. Figure 17. Figure 18. Figure 19. Dendrogram of the eleven vibracore samples and the 1981 beach samples (ISB = inner sand body facies; MBA = modern beach affinities; OSB = outer sand body facies).................55 Bivariate plot of factor loadings for the "1981" sample set and associated grain-shape facies (ISB = inner sand body facies; MBA = modern beach affinities; MRA = modern river affinities; OSB = outer sand body facies; PA = Pleistocene affinities)..................58 Examples of the more elongate and rough quartz grains typical of the Pleistocene sand from vibracore P1970 ..................... 60 Examples of the more equant and smooth quartz grains typical of sand from vibracore 1656..............................................62 Examples of the quartz grains typical of sand from vibracore sample 1970 .............. 64 Scanning electron photomicrographs of the more elongate and rough quartz grains typical of the Pleistocene sand from vibracore P1970 . Scale bar is 0.5 mm.......66 Scanning electr more equant and of sand from vi 0.5 mm......... on photomicrogra smooth quartz g braeore 1656. S phs of the rains typical cale bar is 68 Dendrograms of (a) the beach samples with the San Luis Rey River sample, and (b) the 1982 beach samples with the San Luis Rey River sample............................................7 7 Dendrogram of the 1987 beach samples with two Oceanside Harbor samples and the San Luis Rey River sample.....................................79 vi LIST OF TABLES Table 1. Table 2. Table 3. Page The length of the eleven vibracores and the water depth from which each was recovered.... 10 Mean phi and phi standard deviation values for the eleven vibracore samples...............37 The result of discriminant function analysis for the 1981 Oceanside beach samples. Possible source samples are from Camp Pendleton cliff (CPI), the Santa Margarita River (SMR), the San Luis Rey River (SLRR), north fillet beach (NF), vibracore P1970 (P1979) and vibracore 1656 (1656)....................................... 73 vi i ABSTRACT An inner shelf sand body, which formed between 1934 and 1971-72, occurs at water depths from 40 to 60 feet and extends more than 7 miles along the coast offshore of Oceanside, California. This sand body averages about 0.5 mile wide, is as much as 6 feet high, and has a volume of 4.4 million cubic yards. Earlier studies suggest that the sand was transported to the aggradationa1 area by a swell generated, semi-permanent rip current associated with the breakwater at Oceanside Harbor and deep-water longshore currents. Grain-size trends suggest net offshore rather than longshore sand transport. The probable occurrence of hummocky cross stratification in eleven vibracores recovered from the aggradational area suggests that these strata were deposited by a combination of waning storm generated unidirectional flows with superimposed oscillatory storm-generated wave activity. The planar to slightly-curving laminations observed in the vibracores are interpreted as segments of hummocky cross stratification. The result of the Fourier quartz grain-shape analysis demonstrates five distinct grain-shape facies in the Oceanside area. These are: 1) inner sand body facies, 2) outer sand body facies, 3) modern beach and beach- vi i i influenced facies, 4) modern fluvial and fluvially- influenced facies, and 5) Pleistocene and Pleistocene- influenced facies. This result indicates that the aggradational area samples are distinct from the modern beach and river samples. The grain shapes associated with the inner and outer sand body represent extremes. The outer sand body is characterized by more equant and smoother grains, whereas the general grain shape of the inner sand body is more elongate and rough. The occurrence of the most regularly-shaped grains in the most seaward position is exactly opposite of the relationship expected by shape sorting. The more ir r egulary-shaped grains may be expected to be transported farther, because they remain in suspension longer than more regularly- shaped grains. The sediment in the outer sand body should be derived by the resuspension of older inner-shelf sediment during episodic storm events, which greatly diluted any contribution from the modern beach and rivers. The late Pleistocene sediment whose quartz grain-shape is characterized by more elongate and rough would be the local sand source to the overlying Holocene strata of the inner sand body during episodic storm events differentiating grain-shape characteristics from those of the outer sand body and modern beach and rivers. The area of vibracores 1884 and 1979.6, modern beach sand is identifiable suggesting that the area has not been substantially diluted by mixing with older resuspended inner shelf sediment. At least three episodic events are responsible for the occurrence and quartz grain-shape characteristics of the offshore aggradational area in the Oceanside area. The oldest event would represent deposition of strata in the outer sand body; the medial event would be the deposition of strata in the inner sand body; and the youngest event would be the deposition of strata in the upper parts of vibracores 1884 and 1979.6. It is possible that these three preserved events might represent the remnants of a series of storms of decreasing intensity and duration, each of which was progressively less capable of resuspending inner shelf sediment. The effects of beach nourishment projects on Oceanside beaches completed in May 1982 and March 1984 may be identified by Fourier quartz grain-shape analysis. x INTRODUCTION The paucity of knowledge concerning the nature of sediment transport under given oceanographic conditions in natural marine environments has impaired the development of cost-effective coastal engineering structures. The City of Oceanside, California (Fig. 1) has suffered severe economic losses as a result of beach erosion much of which has been attributed to the construction of the jetty at Camp Pendleton during World War II that interupts downcoast sand transport. Futhermore, drought conditions from 1945-1977 and damming of the San Luis Rey River has reduced the contribution of sand to the ocean, narrowing beaches and increasing wave erosion (Osborne and Pipkin, 1982). Emery (1960) and Inman and Chamberlain (1960) identified a series of littoral cells along the southern California coast based on the concept of longshore transport of dominantly fluvially-derived sediment, which is entrapped either by submarine canyon heads or by points of land which extend seaward from the general position of the coastline. The study area is included in the Oceanside Littoral Cell (Fig. 1). Tekmarine, Inc. (1986) described the occurrence of an offshore sand body, seaward of the 30-foot isobath, from 1 an area immediately offshore of Oceanside Harbor and extending downcoast (Fig. 2). The offshore aggradational area with more than 2 feet of vertical aggradation occurs between the 40- and 60-foot isobaths, and is located about 1.5 miles from the shore near Oceanside Harbor to less than 1 mile offshore approximately 5 miles downcoast. The offshore aggradational area averages about 0.5 mile in width, and extends somewhat north of Oceanside Harbor to more than 7 miles downcoast. This offshore sand body was discovered by comparing the National Ocean Survey bathymetric charts of 1934 and 1971-1972. This sand body area developed sometime during a period of about 38 years. Aggradation along most of the sand body area ranges from 2 to 4 feet, but as much as 6 feet of aggradation occur in restricted areas. The total sediment volume in the offshore sand body area has been estimated at 4.4 million cubic yards (Tekmarine, Inc., 1986). Tekmarine, Inc. (1986) postulated that the development of this offshore sand body may be due to sediment deflected offshore by engineered structures associated with the Del Mar Boat Basin and Oceanside Harbor. Subsequently, such sediment would be moved parallel to the coast by bottom currents. The rate of offshore sediment transport was estimated at 2,400,000 cubic yards per year for the period from 1962 to 1972 (Tekmarine, Inc., 1986). The first 635 m of the North 2 Figure 1. Location map. 3 Point Conception Santa Barbara A. Santa Barbara Cell B. Dume Cell C. Santa Monica Cell D. San Pedro Cell E. Oceanside Cell 0 20 40 km 1 _____. ___1 SCALE • Los Angeles Oceanside 1 . Hueneme Canyon 2. Mugu Canyon 3. Dume Canyon 4. Redondo Canyon 5. Newport Canyon 6. La Jolla Canyon Oceanside San Diego Figure 2 Map showing historical changes in topography offshore of Oceanside between 1934 and 1971-72 (from Tekmarine, Inc., 1986, p. 65). 5 OCEANSIDE HARBOR SCALE 1 $ $ $ ' ACCRETION GREATER THAN 2 FT NUMERALS OENOTE ACCRETION (OR EROSION) IN FT Breakwater at the Del Mar Boat Basin was constructed in 1942. As this was the first engineered structure potentially capable of offshore sediment deflection in this area, the estimated volume of sediment deflected offshore for the 30-year period from 1942 to 1972 is 7,200,000 cubic yards. This value is considerably larger than the 4.4 million cubic yards computed for the volume of the offshore sand body, therefore in terms of volumetric consideration the sedimentologic process proposed by Tekmarine, Inc. (1986) may serve as a forcing agent. Furthermore, it should be pointed out that this model suggests rather continuous sediment supply to the offshore sand body area as well as sediment transport paths essentially parallel to the coast within the aggradational area. Inman and Jenkins (1983) suggested the occurrence of a semi-permanent rip current, which presumably is responsible for transporting a plume of sand offshore of the southern end of the North Breakwater at Oceanside Harbor to water depths as much as 42 feet. The sedimentologic model proposed by Tekmarine, Inc. (1986) is similar in some respects to that discussed by Inman and Jenkins (1983). They suggested that this rip current was responsible for depositing approximately 3.168 million cubic yards of sed iment offshore of Oceanside Harbor from 1942 to 1983 . The analysis of bathymetric maps from 7 March, 1934 to October, 1950 led Inman and Jenkins to delimit three areas of sediment aggradation as discrete aggradational areas as opposed to the continuous sand body area shown in Figure 2: 1) between 30 and 42 feet off the Santa Margarita River; 2) to as much as 42 feet off Oceanside Harbor; and 3) from 24 to 42 feet off South Oceanside and Carlsbad (Inman and Jenkins, 1983, their Figure 3.4.3). The offshore sand body identified by Tekmarine, Inc. (1986) may or may not have been present in January and February 1981, when the vibracores used in this study were recovered. The nature of the submarine topography in the aggradational area after 1972 is not known. Likewise, the absolute age of the strata in the aggradational area is not known; however, the occurrence of a stocking in the upper part of vibracore 1970 suggests that the strata penetrated in that area are fairly recent. Bathymetric data associated with the recovered vibracores are too widely- and irregularly-spaced to discern the morphology of the sand body. The purpose of this study is to examine the microstratigraphy and vertical sedimentary sequences from a set of vibracores recovered from the general offshore aggradational area; to determine the local sources and transport paths of sand contained in the aggradational area by means of grain-size and Fourier quartz grain-shape 8 analyses; to integrate these data to determine the depositional characteristics of these strata; and to test the effects of the beach nourishments by Fourier grain- shape analysis at Oceanside beaches. METHODS Sample Collection A total of 13 vibracores were collected in the Oceanside area during January and February of 1981 by personnel of Ocean Surveys, Inc. on board the RV Piamond Lady under contract to the U.S. Army Coastal Engineering Research Center. Eleven vibracores were used in this study. From north to south, these are: 1721, 1852, 1675, 2120 , 1656 , 1970 , 1884 , 1979. 6, 1891, 1986 and 2053 (Fig. 3) . A 6.1 m long, 9.8 cm in diameter core pipe with a pneumatic piston vibrator was used to obtain the vibracores. The recovered cores of interest range from 0.92 to 3.00 m in length, and were taken in water depths from 11.3 to 20.4 m (Table 1). Core description, subsampling, archiving, and conventional grain size and petrographic modal analysis were performed at the Sedimentary Petrology Laboratory at the University of Southern California. The results of these analyses are discussed in Osborne and others (1983), Darigo (1984), and Darigo and Osborne (1986). Of particular interest to the present study are detailed core descriptions and vibracore 9 Table 1 The length of the eleven vibracores and the water depth from which each was recovered. 10 Core No. Core Length (cm) Water Depth ( 1 721 1 86 52 1 852 208 55 1 675 200 67 2120 1 68 37 1 656 290 55 1970 93 45 1884 270 50 1979.6 221 52 1 891 300 55 1 986 92 41 2053 250 55 11 logs presented in Appendix A (after Osborne and others, 1983, Appendix A; and Darigo, 1984, Appendix A). For this study, sand samples from the upper 50 cm were collected from each of the archived vibracores of interest. One Pleistocene sand sample (P1970) was taken at depth of 60 cm in vibracore 1970. Sand samples from the bed of Las Flores Creek (LFC), the Santa Margarita River (SMR) and the San Luis Rey River (SLRR) were collected April 3-5 1986 , during the wet winter season. These samples were collected approximately 2 km above the mouth of the streams to avoid the effects of tidal currents on the grain size and composition of the fluvial samples. Four cliff samples (CPI, CP2A, CP2B and CP3) were taken during June 1986 from three stratigraphic sections in Camp Pendleton area. Two harbor samples near South Jetty were collected in April 1986 at water depth of 12 feet and 18 feet below MLLW. A total of eighteen beach samples were collected from November 30 through December 3, 1981 (1ST81, WIS81 and HAY81); from June to July, 1982 (1ST82, WIS82 and HAY82); from April 3 to 5, 1986 (LFS, SMN, SMS and NF); October 8, 1986 (SLFN, SLFS, SSMN and SSMS); and July 10 , 1987 (SMS2, 1ST87, OP87 and HAY 8 7) . Sample locations are shown on Figure 3. 12 Sample Preparation for Fourier Grain-Shape Analysis Quartz grains from the 0. 2 5-0 . 50 mm (1.0-2.0 phi) or medium sand fraction from each sample was used for the Fourier grain-shape analysis. Samples were first wet- sieved to obtain the desired size fraction minimizing attrition of the quartz grains during sieving. Sieving was followed by drying in convection ovens. After drying was completed, all strongly magnetic minerals were removed from the samples using a hand magnet. The samples were boiled in a solution of 10% HC1 acid and stannous chloride for 20 minutes to remove iron-oxide coatings and carbonate cement (Carver, 1971). The HC1 acid residue was removed by rinsing the samples in de-ionized water. One minute of exposure to hydrofluoric acid etched the quartz grains clean. Such etching does not significantly alter the shape of the grain (Schultz, 1980). All samples were then rinsed in de-ionized water and dried thoroughly. Samples were examined under a petrographic microscope using a reflecting light source. Quartz grains were picked by using a very small brush. These grains were dry mounted on a glass slide, which enhances the constrast between the grain and its background (Ehrlich and Weinberg, 1970). Adequate contrast is essential in the operation of the Fourier grain-shape digitizing program. 13 Figure 3. Sample location map 14 L « . F l o r .. C rta k S .n L u l. R .y R lv.r S*nt* Mtrqtritt Ktvtr SLRR SMR 3RD STREET FORSTER STREET Bu«nt Vliti Ltqoon WIS82 WIS8 I I ST8 7 I ST82 SLFS LFS SMS2 SSMS SMS HAYB7 HAY82 HAYS I SLFN SSMN SMN CP2A CP2B CP3 CPl OP87 pA CD , w «»* NORTh)N^s breakwater . <o I 979.6 MBA . CD ISB _ ...M.MMM.nH, ... 2053 OSB I 675 BOOO fact SCALE Fourier Methodology Fourier quartz grain-shape analysis is quite useful in determining relatively mixed populations of varying grain shape and possibly the budget of the sediment in beach and nearshore environment. Quartz grain shape is a highly satisfactory natural tracer of sediment flux and accumulation and do not appreciably change shape during transportation (Ehrlich and others, 1974; Ehrlich and Chin, 1980). After the first few kilometers of transport from the source, quartz grains undergo little shape modification as long as they are in an aqueous medium (Kuenen, 1960). Each source rock and each source terrane generates quartz grains with distinctive shape signatures, presumably because quartz is susceptible to idiosyncratic 1 ate-tectonic-geochemica 1 events in such terranes (Przygocki and others, 1977; Ehrlich and others, 1980) . Ehrlich and Weinberg (1970) explained detailed mathematical Fourier grain-shape analysis. The shape analysis system was first developed and applied to sand sized quartz in fluvial (Redmond, 1968; and Przygocki and others, 1977), beach (Ehrlich and others, 1974; Porter and others, 1979 ; and Ahlschwede, 198 7 ) , estuarine (Van Nieuwenhuise and others, 1978 ) , and shelf environments (Yarus and others, 1978; Brown and Ehrlich, 1980). Digitizing of the individual quartz grains was accomplished using a Digital Graphics CAT-100 optical 16 digitizer. In this process, a black and white camera projects the maximum two-dimensional image of the quartz grain from a standard binocular petrographic microscope to a video screen. The image of the grain appears dark in relation to the surrounding background since the microscope is lighted from below. A maximum contrast between grain edge and background allows the computer to scan the pixels of the video image and record all boundary points of the grain as Cartesian coordinates (X-Y coordinates). A pixel is determined as a boundary point if it is dark and one of its neighbors is light. While the Cartesian coordinates are computed, the centroid of the projected grain is also computed. The data is stored on floppy disk and transferred from the microcomputer to a Digital Equipment Corporation VAX-11/750 computer. The next step in the digitizing process is to prepare the data for the Fourier transform. The Cartesian coordinates are converted to polar coordinates (radius versus angle). The radius is the distance from a boundary point to the centroid; the angle used is the angle from the horizontal line bisecting the centroid to the boundary point. In order to examine the entire wavenumber amplitude spectrum of a grain during statistical analysis, the Fast Fourier Transform (Brigham, 1974) is used instead of a closed-form Fourier Transform. One requirement of the Fast Fourier Transform is that the data be evenly- 17 spaced. Since the boundary points of a grain are not evenly spaced, the data must be linearly interpolated. The boundary points are interpolated to 128 evenly-spaced points. The Fast Fourier Transform also requires that the data set be centered around zero. To center the data, the mean radius is subtracted from the radius versus angle data. This radius is later placed in the final amplitude spectrum set (Ahlschwede, 1987). Statistical Analysis Upon completion of the Fast Fourier Transform, the amplitude of each wavenumber is calculated by the aquation: SQRT(Real**2 + Imaginary** 2) where SQRT = square root, Real = real number, Imaginary = imaginary number, and **2 = square of the number (Brigham, 1974). This computation allows the amplitude spectrum of an individual grain to be compared to the amplitude spectrum of other grains. This comparison is the first step in the analysis process and directs the path the statistical analyses will follow. Since the input data is real half of the wavenumbers are reflection, and are not used in the statistical analyses. This leaves 64 wavenumbers for analysis. Each wavenumber is represented by a vector. The occurrence of 64 wavenumbers results in the analysis of 64 dimensions in space. 18 Each sample cotains approximately 215 digitized quartz grains. For ease in initial calculations, the characteristic, or average, grain was computed for each sample. To do this, all the vectors of a sample were summed and averaged. The average amplitude spectrum of each sample then was used in statistical analyses (Ahlschwede, 1987) . Cluster Analysis Cluster analysis is a heirarchial classification for comparing similarities of any given data set. In general, an n x m matrix is used where n represents the number of objects and m represents the number of vectors analyzed. When using the cosine-theta similarity coefficient, the resulting matrix is known as a cosine-theta similarity matrix (Joreskog and others, 1976) . In order to determine a similarity measurement among all possible samples in a grain-shape analysis set, an n x n symmetrical matrix must be used. To obtain an n x n symmetrical matrix, the n x m matrix is transposed to an m x n matrix. If the transposition is not performed, the result would not be an n x n similarity matrix, but a m x m correlation matrix of the similarity between variables (Davis, 1973). After the similarity matrix is computed using the IMSL (1982) Q-mode cluster analysis computer program OCLINK, the average amplitude spectrum of all of the 19 samples are grouped in a heirarchy so that those samples with the highest similarity were grouped, or clustered, together. This cluster of highest similarity is then treated as a unit and clustered with the sample showing the next highest similarity. This procedure continues until all of the samples were correctly classified according to similarity (Davis, 1973). The values of similarity range from 0.0 (perfectly similar) to 1.0 (perfectly dissimilar) . Upon completion of the clustering, the sample heirarchy is printed out in the form of a dendrogram for visual inspection. Factor Analysis In multivariate data collection, the purpose of factor analysis is to simplify the interpretation of the structure within a variance-covariance matrix. Eigenvalues and eigenvectors are extracted from the correlation matrix (Davis, 1973). In grain-shape analysis, factor analysis enables the researcher to determine the number and importance of the fundamental properties leading to a particular grain-shape. Q-mode factor analysis was used to facilitate the interpretation of the complex data set by fitting several reference axes to the data. Each individual axis represents a unique causal factor. Interpretation of these factors occurs after their respective sample loadings are computed. 20 Since the factors are computational in nature, the meaning of each individual factor is subject to interpretation (Harmon, 1967). In the factor analysis method used in this study, the measure of similarity is the cosine-theta coefficient (Joreskog and others, 1976). The angular difference between vectors represents the degree of similarity. A value of +1.00 indicates perfect similarity, a value of 0.00 indicates independence, and a value of -1.00 indicates perfect dissimilarity. The factor loading plots contain two axes. When these plots are computed using the same factor for both the X and Y axes, the distribution of samples indicates the relative effect that that particular factor has had on the grain-shapes of a sample. When factor loading plots are computed using different factors for the X and Y axes, samples tend to group in one or more fields, which are interpreted to have genetic significance. Discriminant Function Analysis The discriminant function analysis was computed using IMSL (1982) computer program ODNORM. Discriminant function analysis was used to determine the relative contributions of the end members and possible source samples to the beach samples. Each source was assigned equal probability of contributing sand to the Oceanside 21 beach. The assigning of probabilities established a source set to compare samples against. Beach samples were tested against the source sets and percentage composition was calculated (Ahlschwede , 1 98 7 ) . In discriminant function analysis, a transform gives the minimum ratio of the difference between a pair of group multivariate means to the multivariate variance within the groups (Ahlschwede, 1987). The orientation of the groups that results in the maximum separation must be determined (Davis, 1973). After this transform was computed for the end members, the average amplitude spectrum set was classified as belonging to one of the end members. Each grain of each 215 grain file was classifed as belonging to one of the end members. QUATERNARY STRATIGRAPHY OF THE OCEANSIDE AREA The Quaternary geology of the mainland shelf off San Diego County (Oceanside, La Jolla, Mission Beach and San Diego Bay) recently has been discussed by Darigo and Osborne (1986). Offshore of Oceanside, shoreline angles designated as Pleistocene were identified at depths of 25 to 26 m, 33 to 34 m, 46 to 50 m, and 56 to 59 m below present sea level (b.p.s.l.). The two smaller shoreline angles are farther inshore than the others, and may outline the shoreline of a lagoon or estuary, as suggested by the character of the overlying reflectors (Darigo, 22 1984) . The terraces at 46 to 50 m and 56 to 59 m truncate Tertiary and older Pleistocene strata, and provide the base for a late Pleistocene progradational shelf deposit. The nearshore parts of these two terraces disappear near the Oceanside pier due to later channelling, but their abrasion platforms continue much farther to the north and sometimes appear to merge into one terrace due to their small vertical separation and the resolution limits of the seismic data. A stratigraphic section of prograded marine shelf strata from 7 to 15 m thick overlies two of the late Pleistocene terraces at Oceanside (Darigo and Osborne, 1986). These strata are tentatively correlated with unit D of Young (1980), who identified this unit as part of a Pleistocene marine sequence that fills the trough between the South Coast fault zone and the shoreline north of Oceanside. Unit D overlies the 46 to 50 m and 56 to 59 m terraces, and forms a continuous strip along the Oceanside shelf (Darigo and Osborne, 1986, Figs. 5, 11 and 12). In the Oceanside area, Pleistocene sediment was recovered only in vibracore 1970. The late Pleistocene nonmarine strata are covered by Holocene marine sediment almost everywhere along the inner San Diego County shelf. The thickness of this unit has been mapped by Henry (1976) , Fischer and others (1980), Young (1980), and Osborne and others (1983) . The Holocene marine strata often overlie 23 marine terraces. Holocene depositional history along the San Diego County shelf is relatively simple. The thickest Holocene stratigraphic sections occur where there has been downcutting and filling of river valleys. Ellis and Lee (1919) described the Holocene alluvial fill onshore as sand and silt, with occasional layers of gravel and clay. Near the mouths of tributary canyons and along the margins of the valleys where cliffs are actively eroding, Holocene sediment also may include slope wash or debris flows composed of clay, sandy clay or small boulders in a clay matrix. The shoreline angles of the Holocene terraces occur at five different depths: 24 to 29 m, 30 to 36 m, 38 to 45 m, 42 to 46 m, and 63 to 71 m (Darigo and Osborne, 1986) . The 38 to 45 m terrace is the most continuous and widespread of all the terraces mapped, and may correlate to a low sea level stand at 46 m b.p.s.l. proposed by Scheidemann (1980) and Nardin and others (1981). The 24 to 29 m shoreline angle appears in short segments offshore of Oceanside and Mission Beach. This terrace may correlate with the 24 m terrace in Santa Monica Bay, which is thought to have been cut during a minor sea level high about 12,000 years ago (Scheidemann, 1980; Nardin and others, 1981; Darigo and Osborne, 1986) . This event immediately preceded the oscillation that cut the 38 to 45 m terrace 11,000 years ago. The Holocene terraces at 24 30 to 36 m, 4 2 to 46 m, and 63 to 71 m appear only offshore of Oceanside (Darigo and Osborne, 1986). Although certain of these Holocene terraces may be capped by thin, coarse-grained nonmarine sediment, virtually all of the Holocene strata in the Oceanside area consists of Holocene Type I and Holocene Type II sediments (Darigo and Osborne, 1986). The vast majority of samples in the Oceanside area are composed of Holocene Type I sediment, which consists of an olive-gray, poorly-to moderately-sorted, micaceous, silty, very fine- to fine grained marine sand with occasional sand- and gravel-size whole shells and shell fragments. The sand of Holocene Type I sand is more homogeneous and better sorted than that of any other sediment group. At a stratigraphic scale, it is present in every area of the inner San Diego County shelf, and blankets the shelf as a nearly continuous deposit. It is present throughout the inner shelf in the Oceanside area. Although its fine grain size may reflect settling from suspension in more quiescent offshore water, high-energy, episodic events such as storms and flooding may have been the forcing events responsible for transporting this sediment offshore. Holocene Type II sediment includes all Holocene sediment coarser-grained than Type I, and Type II typically occurs within or marginal to drowned offshore river valleys. These deposits contain silt- to gravel-size sediment with 25 occasional shell fragments and pebble layers, and typically are poorly- to very-poorly sorted. Type II sediment occurs in vibracores 1721, 1979.6 and 2120, and was deposited either in a fluvial or marine environment by floods that flushed sediment through or along a fluvial channel. Late Pleistocene alluvial sediment occurs in the stratigraphic interval from 40 to 93 cm in vibracore 1970 in the Oceanside area. In the northern Oceanside area, the base of the Holocene nonmarine section occurs below the 50 m penetration limit of the seismic signal used by Darigo and Osborne (1986) . A longitudinal cross-section through water wells in the San Luis Rey River reveals that the base of the Holocene channel fill occurs at about 50 m b.p.s.l. near the coastline. Shlemon (1979) reported a similar occurrence near the mouth of the Santa Margarita River. North of the San Luis Rey River, Holocene nonmarine strata occur everywhere above approximately 20 m b.p.s.l., and therefore is not really restricted to discrete channels. This implies that when the sea reached 20 m b.p.s.l. during the Holocene transgression, the Santa Margarita and San Luis Rey Rivers had coalesced into one broad alluvial plain. 26 STRATIGRAPHY AND SEDIMENTARY STRUCTURES OF VIBRACORES Stratigraphy of Vibracores A total of eleven vibracores were recovered in the Oceanside area (Fig. 3). Five of the vibracores, 1656, 1675, 1852, 1884 and 1891, which range in length from 200 to 4 80 cm (Table 1) , penetrated only Holocene marine strata. These vibracores consist mainly of micaceous, silty, very fine-grained sand with occasional shell fragments (see Appendix A). The average Holocene marine sand sampled in the Oceanside area is very fine-grained and moderately well-sorted. It is referred to as the Type I Holocene sediment (Darigo and Osborne, 1986). Three of the vibracores, 1721, 1979.6 and 2120, passed through Holocene marine strata and recovered from 16 to 30 cm of the Holocene channel-fill facies. It consists of a poorly-sorted conglomerate with grain sizes ranging from silt to cobble. Two vibracores in the southern Oceanside area, 1986 and 2053, are composed mainly of the Holocene marine sediment but penetrated sand of the Eocene Santiago Formation (Darigo, 1984; Darigo and Osborne, 1986). The Eocene strata consist predominantly of medium- to coarse grained sand with shell fragments. These cores only penetrated 20 and 24 cm of the Eocene strata, respectively. Vibracore 1970 consists of the Holocene 27 marine sediment and penetrated 53 cm of the alluvial fan facies of a late Pleistocene estuarine sequence (Darigo, 1984 ; Darigo and Osborne, 1986). The base of the marine unit contains pebbles and cobbles. The Pleistocene sediment consists of a micaceous, moderately well-sorted, and medium-grained sand. A generalized panel diagram was constructed to show the microstratigraphy of the viracores (Fig. 4). Sedimentary Structures Due to the small geographic, stratigraphic and temporal scales of this study, the vibracores were quite useful in determining the sedimentologic history of the offshore aggradational area. In particular, the presence of erosional surfaces, the character of vertical sedimentary sequences, the types of stratification present, and the degree of bioturbation evident in the vibracores are essential in determining the genesis of the Oceanside offshore sand body. The principal sedimentary sequence observed in most vibracores begins with an erosional base marked by a relatively coarse-grained unit containing transported shells and shell fragments, plant debris, and rock-fragment or intraclastic pebbles (Fig. 4 and Appendix A). This relatively coarse-grained unit is overlain by the principal part of the sequence, which consists of bioturbated, laminated, silty, fine-grained 28 sand. Pebbles and well-defined heavy-minera 1 laminae occur but are uncommon within the interval of laminated, fine-grained sand. Although small-scale, wave-ripple laminae might form along the water-sed iment interface at the top of the laminated-sand interval, such features were not observed. The sedimentary sequence described is identical to that of a typical storm sequence described by Kumar and Sanders (1976). In their study of modern and ancient shoreface storm deposits, they suggest the following storm sequence, from bottom to top: a) basal lag deposit, consisting of pebbles or possibly cobbles or coarse-grained shell debris, b) laminated sand, of variable thickness, composed of sediment deposited rapidly from suspension as the storm waned and while bottom shear was intense enough to exclude rhythmic bed forms, and c) a fair-weather capping of variable thickness, consisting either of wave-ripple laminae (if landward of fair weather wave base) or of burrow-mottled sediment (if seaward of fair-weather wave base). Interestingly enough, Figure 4 shows that there is apparently only one bioturbated, fining-upward sequence present in the vibracores. This, in turn, might suggest that the bulk of the sediment represented by the vibracores may have transported to the depositional site during one high-energy event. 29 Figure 4 Panel diagram showing the microstratigraphic relationships among the vibracores recovered offshore of Oceanside, California. 30 Buena Vista Lagoon Santa Margarita River San Luis Rey River I 9 7 9 .6 I 9 7 0 2 I 20 I 89 I • 8 8 4 Water Depth I 0 feet .a. • 65 Core Length • 85 2 25 cm SCALE u> In general, these strata have been bioturbated to the degree that only remnant primary sedimentary and biogenic structures remain. The only primary structures preserved are remnants of planar to slightly-curving laminations in the laminated-sand interval. Poorly-defined shell layers are present in a number of the vibracores examined. Bioturbation tends to obscure sedimentary structures and sequence boundaries within the vibracores. It is possible that the heavy mineral concentrates described in the vibracore logs represent the intrastratal traces of a burrowing polychaete similar to Nephtys cali for iens is , which concentrates heavy minerals along the bottom of its burrow (Howard and Reineck , 1981). The planar to slightly-curving laminations observed in the vibracores are interpreted as segments of hummocky cross stratification (HC3), which consists of curving laminations both hummocks and swales, with maximum dips of from 12 to 15 degrees. Full geometric descriptions of HC3 have been provided by Walker (1982), Dott and Bourgeois (1982), and Walker and others (1983). Dott and Bourgeois ( 1982) , Walker and others (1983) , and Swift and others (1983) discuss the mechanics of HCS formation, and suggest a combination of waning storm-generated unidirectional flows with superimposed oscillatory storm-generated wave action. In a study of 105 occurrences of HCS, Duke (1985) points out that the only storms capable of profoundly 32 affecting shallow-marine depositional environments are severe tropical cyclones and mid-latitude winter wave cyclones. Clearly the latter type of storm system would be more appropriate for the Oceanside area. If the interpretation of the planar to slightly- curving laminations observed in the vibracores as representing segments of HCS is correct, compelling evidence is presented in favor of a storm-generated, episodic origin rather than a gradualistic accretionary origin for the bulk of the sediment occurring in the Oceanside offshore sand body area. The lack of large- scale, high-angle cross strata in the vibracores argues against interpreting these strata as a series of coalesced bedforms (dunes and ripples). The stratigraphy, sedimentary sequence, primary sedimentary structures, grain-size and degree of bioturbation compare closely with the transition facies described by Howard and Reineck (1981) for the nearshore and inner continental shelf offshore of Ventura-Port Hueneme, California. Their transition facies occurs at depths from 9.3 to 18.7 m below sea level, and is characterized by bioturbated, laminated, silty, fine grained sand with some small-scale oscillation-ripple laminae. Biogenic structures such as shell nests, polychaete tunnels, plant fragments, and sediment-filled burrows also appear in cores from the transition facies. 33 The laminae present are interpreted as remnants of HCS by Howard and Reineck (1981) . Howard and Reineck (1981) also describe similar sedimentary sequence in their transition facies using either (1) the lower contact as determined by shell layers or the erosional contact between bioturbated sediment and nonb i oturbated sediment; or (2) the tops of sequences as defined by the presence of silt or clayey mud. The thickness of such sequences range from 10 to 50 cm, with 4 5 cm being an average. Seaward of the Santa Clara River, some sequences are as much as 190 cm thick, with an average of 74 cm. It should be noted that the thicknesses of the sequences descr ibed from the Ventura- Port Hueneme area are quite similar to the one described from the Oceanside offshore sand body area. Howard and Reineck (1981) identify two factors which appear to control sedimentation in the transition facies: (1) the influence of sediment from the Santa Clara River and associated wave-induced currents, and (2) the influence of wave-induced currents associated with storms. Drake and others (1972) studied the continental shelf in the Oxnard-Ventura area following major floods of the Santa Clara River in January and February 1969. Their work shows that more than 70 percent of the flood-derived sediment initially was deposited in less than 30 m of water depth on the inner shelf, and that sand-size grains were confined to the coastal strip within 1.5 km of the 34 shoreline. They also noted that material deposited immediately after the flood was subsequently spread farther across the shelf by wave-generated currents. The sed imentary sequences and probable HCS observed in the Ventura-Port Hueneme area strongly suggest that these strata were deposited largely in response to storms that erode the substrate to a greater depth than normal- or fair-weather wave base. During storms, there is a piling up of water in the nearshore zone; and, as the storm subsides the thickened water mass moves seaward as a relaxation or storm surge ebb current, and at that time, sediment is spread across and perhaps along the shelf as storm layers. For example, such storm layers have been described in the Gulf of Mexico (Hayes, 1967) and the North Sea (Reineck, 1963; Reineck and others, 1967; Gadow and Reineck, 1969; Reineck and Singh, 1971). The deposition of sediment associated with severe storms is episodic in character rather than gradua1istic . It is interesting to note that their transition facies appears to result from a two-part process in which sediment is initially brought to the shelf and deposited nearshore by river floods and subsequently it is redistributed by storms. 35 GRAIN-SIZE CHARACTERISTICS OF AGGRADATIONAL AREA Sediment transport paths may be identified by the reduction of mean grain size and standard deviation in the transport direction (McLaren, 1981). The grain-size data was supplied by the Los Angeles District of the U.S. Army Corps of Engineers. Grain-size data representing the weight percent of sediment passing through a given sieve was recomputed to the weight percent of sediment retained in a given sieve. Mean and standard deviation were computed using the phi scale. Standard deviation values in the offshore sand body area (Table 2) show very small differences, and due to the small sample size, are not considered further. The 3.25 phi and 3.50 phi contours (Fig. 5) show a general shore-parallel rather than a snore-normal fining trends, therefore the available grain size data suggests offshore rather than shore-parallel sand transport. At least 90 percent of the strata in the aggradational area consists of sediment that is less than 2.64 phi in diameter. The linear proportions of the sand body suggests that approximately 37.5 percent of the sediment in the aggradational area was derived from south of Oceanside Harbor, which would involve the upcoast transport of 1.65 million cubic yards of fine-grained sediment; and that 62.5 percent of the strata in the 36 Table 2 Mean phi and phi standard deviation values for the eleven vibracore samples. 37 Core Upper Mean Mean P h i S t a n d a r d No. U n it (cm) P h i mm D e v i a t i o n 1 721 0 - 90 3.40 0.095 0.4 1852 0 - 1 00 3.50 0.088 0.4 1675 0 - 1 1 1 3.10 0.117 0.6 2120 0 - 70 3.10 0.117 0.3 1656 0 - 83 3.55 0.085 0.55 1970 0 - 40 1 .95 0.259 1 .7 1884 0 - 70 3.43 0.093 0.325 1979.6 0 - 80 3.25 0.105 0.4 1891 0 - 100 3.50 0.088 0.4 1986 0 - 72 3.28 0.103 0.475 2053 0 120 3.33 0.099 0.425 38 Figure 5 Mean phi from the offshore 3.25 phi grain-size values f recovered vibracore fining trend can be and 3.50 phi contou r sediment samples The predominant discerned from the s. 39 i 2 5 3 . 2 8 3.1 1 9 70 ' 98 .63 3 3 2*20 3.25________ ___.................... ............................ »9. 3.50........ •...................................... . 3 . 5 5 ,852 1656 3.1 • • 6 7 5 q I K m i_---1 SCALE aggradational area was derived from north of Oceanside Harbor, which would involve the downcoast transport of 2.75 million cubic yards of fine-grained sediment. It is possible to estimate the volume of beach sand that must be eroded from north and south of the harbor to supply 4.4 million cubic yards of sediment less than 2.64 phi in d i ameter. The grain-size distributions of littoral sediment samples collected from +5 to -12 foot MLLW and from +5 to -30 foot MLLW (Osborne, 1985) at range lines 15+00N (immediately upcoast of the North Breakwater) and 25+00S (immediately downcoast of the South Jetty) (Fig. 3) were examined to determine the percentage of sediment less than 2.64 phi in diameter present in each sample. At range line 15+00N, approximately 43 percent of the sediment in the +5 to -12 foot sample set and 58 percent of the +5 to -30 foot sample set is less than 2.64 phi in diameter. As this source presumably would contribute 2.75 million cubic yards of fine-grained sediment to the aggradationa1 area, approximately 8.09 million cubic yards would have to be eroded from the beach if derived from the +5 to -12 foot zone, whereas 4.74 million cubic yards would have to be eroded if derived from the +5 to -30 foot zone. At range line 25+00S, approximately 67 percent of the sediment in the +5 to -12 foot sample set and 79 percent of the sediment in the +5 to -30 foot sample set is less than 41 2.64 phi in diameter. As this source would contribute 1.65 million cubic yards of fine-grained sediment to the aggradational area, approximately 2.46 million cubic yards would have to be eroded from the +5 to -12 foot zone, and 2.09 million cubic yards from the +5 to -30 foot zone. Thus a total of approximately 10.55 million cubic yards of sediment would have to be eroded from the +5 to -12 foot zone to supply the aggrada t i o na 1 area with 4.4 million cubic yards of fine-grained sediment, and 6.83 million cubic yards would have to be eroded from the +5 to -30 foot zone to achieve the same result. At this time it is not known whether or not erosion of from 6.83 to 10.55 million cubic yards of beach sediment between 1934 and 1971-72 can be documented. It is possible that much of the fine-grained sediment within the sand body may represent resuspended inner shelf material. FOURIER GRAIN-SHAPE ANALYSIS Results and Interpretation Sand transport paths were determined primarily by using cosine-theta cluster analysis. Cluster analysis determined the pair of samples that were the most similar in shape composition. A third sample was compared to the linked pair, and its relative similarity was calculated. A close linkage on a resultant dendrogram indicates extreme similarity. A distant linkage on a dendrogram 42 represents a lack of similarity. The nature of linkage on the dendrogram indicates possible sand transport paths. For instance, if a river sample is closely linked with a beach sample to the north rather than a beach sample to the south, transport from the river to the north at least as far north as the northern sample is the most probable transport direction of the river-derived sediment. The result of cluster analysis on the eleven vibracore samples can be seen in Figure 6. There are two major groups; vibracore samples 2120, 1721, 1986 and 2053; and 1656, 1675, 1852 and 1891. Geographically these two groups may be considered as inner sand body and outer sand body, respectively. Vibracore samples 1884, 1970 and 1979.6 are distinct from these two groups. To test the sediment transport direction for the vibracore samples, several cluster analyses were performed on samples from the agg r ada t i ona 1 area and associated beach, river and cliff samples. Figure 7 is the result of cluster analysis on the two major sand body facies and four cliff samples. None of the four cliff samples is linked closely with any sample from the sand body. Figure 8 shows the result of the cluster analysis comparing beach samples north of the Santa Margarita River and the two sand body facies. No beach sample is closely linked with any sample from the sand body, and the identity of the two sand body facies is maintained. Cluster analysis also was 43 Figure 6. Dendrogram of the = inner sand body affinities; OSB = eleven vibracore samples (ISB facies; MBA = modern beach outer sand body facies). 44 OSB MBA ISB p 2120 - 1721 -» 2053 -i - 1986 - 1970 --- - 1979.6 --- - 1884------- p 1891 — 1675 — 1656------- L 1852 ---- 45 Figure 7 Dendrogram of the two sand body facies and four cliff samples (ISB = inner sand body facies; OSB = outer sand body facies) . 46 1891 1675 1656 1852 2120 1721 2053 1986 CP2B CP2A CP3 CPI performed on beach samples south of the Santa Margarita River and north of the North Breakwater with the two sand body facies (Fig. 9) . Only one beach sample, SMR2, is linked closely with the sample from vibracore 1891. Figure 10 shows the result of cluster analysis for samples from the two sand body facies with three 1981 beach samples, the Santa Margarita River and the San Luis Rey River. Only one beach sample, HAY81, is linked closely with the outer sand body facies. Cluster analysis also was performed for vibracore samples 1884, 1970 and 1979.6, which did not group with the other sand body samples (Fig. 11). Vibracore samples 1884 and 1979.6 link closely with the three 1981 beach samples, whereas vibracore sample 1970 clusters with the inner sand body facies. Interestingly the inner and outer sand body facies are stochastically distinct in every cluster analysis. Only two beach samples, SMS2 and HAY81, link with the outer sand body facies. In this study, it was assumed that the shape characteristics of the beach samples collected north of the North Breakwater are essentially constant, because of the more natural state of this beach segment. This assumption enabled beach samples from this area to be compared with slightly older samples from the offshore sand body. The three 1981 beach samples which were collected from November 30 through December 3, 1981 also 48 Figure 8. Dendrogram of the two sand body facies and beach samples north of the Santa Margarita River (ISB = inner sand body facies; OSB = outer sand body facies). 49 2120 1721 2053 1986 SSMN SMN LFC LFS SLFS SLFN 1891 1675 1656 1852 Figure 9. Dendrogram of the two sand body facies and beach samples south of the Santa Margarita River (ISB = inner sand body facies; OSB = outer sand body facies). 51 2120 1721 2053 1986 S SMS HF SMS SMS2 1891 1675 1656 1852 Figure 10. Dendrogram of the two sand body facies and the 1981 beach samples with the Santa Margarita River and San Luis Rey River samples (ISB = inner sand body facies; OSB = outer sand body facies) . 53 ISB OSB r- 1891 HAY81 1675 1852 «- 1656 r- 2120 1721 2053 1986 WIS81 1ST81 SLRR SMR 54 Figure 11. Dendrogram of the eleven vibracore samples and the 1981 beach samples (ISB = inner sand body facies; MBA = modern beach affinities; OSB = outer sand body facies). 55 OSB MBA ISB I- 2120 1721 — 1 2053 — - 1986 — * 1970 --- r- WIS81 — 1ST81 — I 1979.6 — | NF - 1884------- - 1891 — HAY81 -- 1675 1852 --- - 1656------- 56 were assumed to be similar to the beach grain-shape characteristics at the time when the vibracores were recovered. Figure 12 shows the results of rotated, orthogonal factor analysis of the first 63 wave numbers for the 26 sand samples thought to approximate sedimentologic conditions typical of the Janua r y-Febr ua r y 1981 period when the vibracores were recovered. Factors 1 and 2 account for 51.8 and 31.7 percent of the total samples variance, respectively, which is a measure of the grain- shape information explained. Thus a total of 83.5 percent of the sample variance is explained by these two factors. The most extreme quartz grain-shape differences occur in sand samples from vibracores P1970 and 1656. All other samples may be explained as mixtures of these two grain- shape end members. Figure 13 shows that the quartz grains typical of vibracore P1970 are elongate and rough; whereas those typical of vibracore 1656 are more equant and smoother (Fig. 14). Figure 15 shows the quartz grains typical of vibracore 1970. Figures 16 and 17 show Scanning Electrone Microscopy pictures of these grains. Accordingly, factor 1 (abcissa) may be interpreted as a measure of grain elongation, and factor 2 (ordinate) may be interpreted as a measure of grain asperity or roughness. Thus from the origin to the left along factor 1, grains become more equidimensional; and from the origin 57 Figure 12, Bivariate plot of factor loadings for the "1981" sample set and associated grain-shape facies (ISB = inner sand body facies; MBA = modern beach affinities; MRA = modern river affinities; OSB = outer sand body facies; PA = Pleistocene affinities). 58 . •! 656 OSB MRA MBA * ISB . • I 970 PA P I 970 - I .0 FACTOR 1 0.0 Figure 13. Examples of the more elongate and rough quartz grains typical of the Pleistocene sand from vibracore P1970. 60 6 1 Figure 14. Examples of the more equant and smooth quartz grains typical of sand from vibracore 1656. 62 6 3 Figure 15. Examples of the grains typical of sand from vibracore sample 1970. 64 65 Figure 16. Scanning electron photomicrographs of the more elongate and rough quartz grains typical of the Pleistocene sand from vibracore P1970. Scale bar is 0.5 mm. 66 67 Figure 17. Scanning electron photomicrographs of the more equant and smooth quartz grains typical of sand from vibracore 1656. Scale bar is 0.5 mm. 68 downward along factor 2, grain asperity or roughness increases. The combination of grain elongation and asperity may be used to identify local sand sources. More elongate, rougher grains tend to reflect first-cycle fluvial grains; whereas more equant, smoother grains tend to reflect quartz grains exposed to environments more consistently exposed to higher mechanical energy such as beaches and eolian dunes. Thus the factor plot (Fig. 12) may be interpreted as representing more fluvially-influenced sand in the lower right to more high-energy beach- or eolian- influenced sand in the upper left. The grain-shape characteristics of the "1981" beach sample set may be assigned to five facies (Fig. 12) . These are: (1) inner sand body facies (2053, 1986, 1721 and 2120); (2) outer sand body facies (1852, 1891, 1675, 1656 and SMS2) ; (3) modern beach and beach-influenced facies (SSMS, SSMN, SLFS, SLFN, SMS, NF, 1ST81, WIS81, HAY81 , 1884 and 1979 . 6); (4) modern fluvial and fluvially- influenced beach facies (LFC, LFS, SMR, SMN and SLRR); and (5) Pleistocene and Pleistocene-influenced facies (1970 and PI970) . It is of considerable importance to note that the grain shapes associated with the offshore sand body are quite distinct and may be considered as end members for the Holocene strata. The modern fluvial and beach sample 70 fields occur in the central part of Figure 12. Such differences in grain-shape populations characteristic of the inner and outer sand body as compared to the modern fluvial and beach fields conceivably might be explained in terms of either different local sand sources or by selective sorting by grain shape. The grain size and density of the quartz grains used in this Fourier grain- shape analysis are very similar, therefore selective sorting by grain size and/or grain density is minimized. More irregularly-shaped grains remain in suspension longer than more r eg u 1 a r 1 y-shaped grains (Kennedy and Ehrlich, 1985; Moss, 1966), therefore more irregularly-shaped grains may be expected to be transported farther. Inasmuch as terminal sand deposition may be expected to mostly occur during the waning or relaxation phase of a grains may be expected to occur in more offshore or downcurrent depositional area, whereas more regularly- shaped grains may be expected to occur in more landward or upcurrent depositional areas. In this study, the more regularly-shaped grains occur in the outer sand body, which forms a shore-parallel band in the most offshore position of the sample set studied. The occurrence of the most regularly-shaped grains in the most seaward position is exactly opposite of the relationship expected if sorting by grains shape was the forcing mechanism. high-energy event, more irregularly-shaped 71 Therefore, it seems that contributions from different local sand sources may serve to explain the grain-shape groups obtained by factor analysis. Table 3 shows the results of the discriminant function analysis on the 1981 Oceanside beach samples, 1ST81, HAY81 and WIS81. The samples from Camp Pendleton cliff (CPI) , the Santa Margarita River (SMR) , the San Luis Rey River (SLRR), north fillet beach (NF) and two grain- shape end members of "1981" sample set (vibracore samples 1656 and P1970) were considered as possible sources. It seems that the outer sand body sample, 1656, is the major sand source sample for the 1981 Oceanside beach samples. Three Oceanside beach samples are made up of 40 percent vibracore sample 1656 (Table 3). The fact that Oceanside beach samples show relatively close relationship to the outer sand body sample rather than cliff, river or upcoast beach samples may indicate shelf sediment contributions to the beach samples resulted from episodic storm events. Identification of Sand from Beach Nourishment Project Completed by May 1982 The beaches from the Third to Forster Streets in Oceanside were nourished with 463,000 cubic yards of sand from Oceanside Harbor by June 1981. By May 1982, 920,000 cubic yards of sand from the San Luis Rey River were 72 Table 3. The result of discriminant function analysis for the 1981 Oceanside beach samples. Possible source samples are from Camp Pendleton cliff (CPI), the Santa Margarita River (SMR), the San Luis Rey River (SLRR), north fillet beach (NF), vibracore P1970 (P1970) and vibracore 1656 (1656) . 73 CP1 % SMR % SLRR % NF % P1970 % 1 656 % 1ST81 5.6 8 . 8 15 .8 25.6 7 .4 3 6 .7 HAY81 7.0 6 . 5 9 .8 20.9 18.6 3 7 .2 WIS81 4.2 1 .9 7 .0 14.0 2 6 .6 4 6 .3 placed on Oceanside beaches from First Street to the upcoast groin at Buena Vista Lagoon. Cluster analyses on 1981 and 1982 beach samples were performed to determine if the effects of the 1982 beach nourishment were identifiable by Fourier grain-shape analysis (Fig. 18). Figure 18a shows that beach samples from Wisconsin Street (WIS81) and First Street (1ST81) are linked with the north fillet beach sample (NF) . The Hayes Street beach sample (HAY81) is distinct. The San Luis Rey River sample (SLRR) is linked with all of the 1982 beach samples, except Hayes Street (Fig. 18b) . This is an important result, because the 1982 beach samples were collected in June-July 1982 shortly after the beach nourishment program using sand from the San Luis Rey River bed. Clearly, this change in beach sediment source was identified efficiently by Fourier grain-shape analysis. Much of the San Luis Rey River sand was removed from Oceanside beach during the storms of November and December 1982. The volume of this sand returned to the beach area is unknown. Identification of Sand from Beach Nourishment Project Completed by March 1984 By March 1984, 406,000 cubic yards of sand from Oceanside Harbor were placed on Oceanside beaches from the Third to Forster Streets. Cluster analysis of 1987 Oceanside beach samples and two harbor samples with north 75 fillet beach sample and the San Luis Rey River sample was performed to determine if the effects of the 1984 beach nourishment were identifiable (Fig. 19). Figure 19 shows that all beach samples are linked closely with the harbor and north fillet beach samples. The San Luis Rey River sample is quite distinct. The result of this cluster analysis indicates that the grain-shape characteristics of the Oceanside beaches from the Third to Forster Streets returned to the 1981 beach condition, and clearly reflects the March 1984 nourishment program. DISCUSSION The result of grain-size analysis suggests that the dominance of offshore rather than longshore sediment transport in Oceanside area. Analysis of the primary sedimentary structures and vertical sedimentary sequences in the recovered vibracores indicates that the strata in the aggradational area were deposited by a combination of waning storm-generated unidirectional flows with superimposed oscillatory storm-generated wave activity. Kuhn and others (1987) discuss the storm years recorded in southern California for the period from 1947 to 1986 , and Kuhn and others (in press) discuss similar information for the period from 1887 to 1947 . Review of these reports indicates at least six major storm periods occurred between 1934 and 1972: summer, 1934; winter, 1936-37; 76 Figure 18. Dendrograms of (a) San Luis Rey River beach samples with sample. the beach samples with the sample, and (b) the 198 2 the San Luis Rey River 77 WIS81 1ST81 NF SLRR HAY81 WIS82 1ST82 SLRR HAY82 Figure 19. Dendrogram of the 1987 beach samples with two Oceanside Harbor samples and the San Luis Rey River sample. 79 0P87 H18 1ST87 HAY87 NF H12 SLRR March, 1938; September, 1939; December-January, 1940-41; and January-February, 1968-69. It is interesting to note that all but one of these storms occurred before initial construction of the North Breakwater in 1942. Inasmuch as the exact age of the strata within the aggradational area is unknown, it cannot be determined which combination of these or perhaps other storms may have been the forcing agent responsible for deposition of strata in the offshore aggradational area. The outer sand body is characterized by more equant and smoother grains (Fig. 14 and 17), which suggests that a large proportion of these grains were entrained in a relatively high mechan i ca 1 -ener gy regime at some state during their transport history. Assuming reasonable entrainment periods, environments such as high-energy beaches or eolian dunes may provide adequate mechanical energy for grain breakage and attrition to produce more equant and smoother quartz grains. Inasmuch as the sediment in the outer sand body contains a relatively high percentage of more regularly-shaped quartz grains, it seems likely that such grains were derived from a different local source, perhaps an older beach or eolian sand with more equant and smoother grains than those along the present Oceanside beaches. It is possible that such grains were incorporated into the strata recovered in the 81 vibracores by the resuspension of older Quaternary or, perhaps even Eocene strata. Vibracore 1970 consists of 40 cm of Holocene strata overlying 53 cm of a late Pleistocene alluvial fan facies associated with an estuarine sequence (Darigo, 1984; Darigo and Osborne, 1986) . Figure 15 shows that the quartz grains typical of Holocene strata in vibracore 1970 are elongate and rough similar to those of P1970 (Fig. 13). The elongate and rough quartz grains contained in vibracore sample 1970 most likely reflect grain derivation from the underlying late Pleistocene strata. This also can be seen in Figure 12 that vibracore sample 1970 is in the Pleistocene-influenced field. It is, therefore, the late Pleistocene sediment that contributed substantial numbers of quartz grains to the overlying Holocene strata in the area of vibracore 1970 . The quartz grains in vibracore sample P1970 are quite similar to those from the Santa Margarita River sample (SMR) with respect to grain elongation (Fig. 12); however, the grains in sample P1970 are much rougher. This relationship may be expected, because vibracore sample P1970 is from a late Pleistocene alluvial fan facies, whereas the Santa Margarita River sample (SMR) was taken at a much more distal position near the river's mouth. Inasmuch as vibracore samples 1656 and P1970 are the grain-shape extremes with regard to both grain elongation and asperity, the grain-shape 82 characteristics of all other samples included in this study may be explained as mixtures of these end member samples. The general similarity of the grain size, sedimentary structures, sedimentary sequences, degree of bioturbation, etc. observed in the vibracores from the sand body suggest rather similar depositional and biogenic processes. However, the fact that the grain-shape facies of the inner and outer sand body are strikingly different demonstrates the pervasive role of at least two local sand sources that are distinct from the modern rivers and beaches in the Oceanside area. One of these local inner-shelf sources has been identified as the Pleistocene strata in vibracore 1970. It seems that much of the sand in the aggradational area represents the resuspension of older sand within the inner shelf off Oceanside. Modern beach sand is identifiable in vibracore samples 1884 and 1979.6, which suggests that these strata have not been substantially diluted by mixing with older resuspended inner shelf sediment. The fact that the quartz grain-shape characteristics of strata recovered in vibracores 1884 and 1979.6 are similar to those of modern Oceanside beach samples but distinct from those recovered from vibracore 1970 suggests that the area of vibracore 1970 was bypassed effectively during one or more storms and that any Pleistocene sediment contributed by 83 resuspension was greatly diluted by modern beach sediment before being deposited in the area of vibracores 1884 and 1979.6. The fact that the quartz grain-shape characteristics of the inner and outer sand body are distinct from the modern beach and fluvial sample fields (Fig. 12), the absence of large-scale, high-angle cross strata in the vibracores, and the likely presence of hummocky cross strata in the vibracores render the sedimentologic model proposed by Tekma rine, Inc. (1986) untenable to explain the deposition of strata in the aggradational area. If, in fact, sand has been deflected offshore by engineered structures associated with the Del Mar Boat Basin and Oceanside Harbor, it most likely is stored temporarily at comparatively shallow water depths. During a significant storm, any such sediment may be expected to be resuspended, and, in this case, greatly diluted by resuspended older inner-shelf sediment. Eventually, such a mixture might be transported seaward and perhaps alongshore, and deposited during the relaxation or waning phase of a storm. The probable occurrence of hummocky cross strata argues for the occurrence of waning storm generated unidirectional flows with superimposed oscillatory storm generated wave action during the deposition of sediment recovered in the vibracores. 84 It is clear that at least three episodic events are recorded in the recovered vibracores. The oldest event would represent deposition of strata in the outer sand body; the medial event would be the deposition of strata in the inner sand body; and the youngest event would be the deposition of strata in the upper parts of vibracores 1884 and 1979 . 6. One may consider the possibility that these three preserved events might represent the remnants of a series of storms of decreasing intensity and duration, each of which was progressively less capable of resuspending inner shelf sediment. CONCLUSION The bathymetric data associated with vibracores recovered from the agg r ada t i o na 1 area in 1981 are too widely and irregularly spaced to discern a low-relief topographic feature on the seafloor. Therefore these data cannot be used to determine whether or not the sand body was present in this area in 1981. Because of the small number of nearshore vibracore samples, the results of this study do not necessarily oppose the occurrence of the rip current which transports sands offshore of the southern end of the North Breakwater at Oceanside Harbor. Grain-size analysis indicates that the 3.25 phi and 3.50 phi contours show a general offshore fining trend suggesting the offshore sediment transport. The range of 85 standard deviation values is too small to define a likely transport direction. Analysis of the primary sedimentary structures and vertical sedimentary sequences in the recovered vibracores indicates that the strata in the offshore aggradational area were deposited by storm-generated wave action. The planar to slightly-curving laminations observed in the vibracores are interpreted as segments of hummocky cross stratification. Fourier grain-shape analysis demonstrates five distinct grain-shape facies in the Oceanside area. These are: outer sand body facies; modern beach and beach- influenced facies; modern fluv ial and fluv ially-influenced facies; inner sand body facies; and a Pleistocene and Pleistocene-influenced facies. The most extreme quartz grain-shape differences occur in sand samples of vibracores 1656 and P1970 . All other samples may be explained as mixtures of these two grain-shape end members. The outer sand body is generally characterized by relatively equant and smooth grains. The typical PIeistocene-inf1uenced quartz grains are relatively elongate and rough. Fourier grain-shape analysis demonstrates that the inner sand body is composed of sand largely derived from late Pleistocene shelf sediment. It seems likely that the outer sand body also consists of sand derived from older shelf sediment. 86 At least three storm-generated, episodic events, each capable of resuspending and transporting shelf sand to the aggradationa1 area, are required to explain the observed grain-shape facies mosaic. The effects of beach nourishment projects completed in May 1982 and March 1984 may be identified by Fourier grain-shape analysis. REFERENCES Ahlschwede, K. S., 1987, Sources and littoral transport of sand in San Diego and southern Orange Counties, southern California: Fourier grain-shape analysis: unpublished M.S. thesis, University of Southern California, Los Angeles, California, 135 p. Brigham, E. 0., 1974, The Fast Fourier Transform, Prentice-Ha11, Inc., Englewood Cliffs, New Jersey, 252 p. Brown, J. B., Ehrlich. R., and Colquhoun, D. J., 1980, Origin of patterns of quartz sand types on the southeastern U.S. continental shelf and implications on contemporary shelf sedimentation - Fourier grain shape analysis: Jour. Sed. Petrology, v. 50, p. 1095-1100. Carver, R. E., 1971, Procedures in Sedimentary Petrology, Wiley-Interscience, New York, 653 p. Darigo, N. J., 1984, Quaternary stratigraphy and sedimentation of the mainland shelf of San Diego County, California: unpublished M.S. thesis, University of Southern California, Los Angeles, California, 393 p. Darigo, N. J., and Osborne, R. H., 1986, Quaternary stratigraphy and sedimentation of the inner continental shelf, San Diego County, California: iri Knight, R. J., and McLean, J. R., eds., Shelf sands and sandstones: Canadian Society of Petroleum Geologists, Memoir II, p. 73-98. 87 Davis, J. C. , 1973, Statistics and Data Analysis in Geology, John Wiley and Sons, New York, 550 p. Dott, R. H., Jr., and Bourgeois, J., 1982, Hummocky stratification: significance of variable bedding sequences: Geol. Soc. America Bull., v. 93, p. 663-680. Drake, D. E., Kolpack, R. L., and Fischer, P. J., 1972, Sediment transport on the Santa Barbara-Oxnard shelf, Santa Barbara Channel, California: i_n Swift, D. J. P., Duane, D. B., and Pilkey, 0. H., eds. , Shelf Sediment Transport: Process and Pattern, Hutchinson and Ross, Stroudsburg, Pennsylvania, Dowden, p. 307-331. Duke, W. L., 1985, Hummocky cross stratification, tropical hurricanes and intense winter storms: Sedimentology, v. 32, p. 167-194. Ehrlich, R., Brown, P. J., Yarus, J. M., and Przygocki, R. S., 1980, The origin of shape frequency distributions and the relationship between size and shape: Jour. Sed. Petrology, v. 50, p. 475-483. Ehrlich, R., and Chin, M. , 1980 , Fourier grain shape analysis: a new tool for sourcing and tracking abyssal silts: Marine Geology, v. 38, p. 475-484. Ehrlich, R., Orzeck, J. J., and Weinberg, B., 1974, Detrital quartz as a natural tracer - Fourier grain shape analysis: Jour. Sed. Petrology, v. 44, p. 145-150. Ehrlich, R., and Weinberg, B., 1970, An exact method for characterization of grain shape: Jour. Sed. Petrology, v. 40, p. 205-212. Ellis, A. J. and Lee, C. H., 1919, Geology and ground waters of the western part of San Diego County, California: U.S. Geol. Survey Water Supply Paper, 446 p. Emery, K. 0., 1960, The sea off southern California: A modern habitat of petroleum, John Wiley and Sons, New York, 366 p. 88 Fischer, P. J., Kreutzer, P. A., Morrison, L. R., Rudat, J. H., Ticken, E. J., Webb, J. F., Woods, M. M., Berry, R. W. , Henry, M. J., Hoyt, D. H., and Young, M., 1980, Offshore sand and gravel deposits, southern California: unpublished report, MESA, Inc., Whittier, Cali fornia, 55 p. Gadow, S., and Reineck, H. -E., 1969, Ablandiger Sandtransport bei Sturmfluten: Senckenb. Mar., v. 1, p. 63-78. Harmon, H. H., 1967, Modern factor analysis: Chicago, Univ. of Chicago Press, Chicago, 474 p. Hayes, M. 0., 1967, Hurricanes as geological agents, south Texas coast: Amer. Assoc. Petroleum Geologists Bull., v. 51, p. 937-942. Henry, M. J., 1976, The unconsolidated sediment distribution on the San Diego County mainland shelf, California: unpublished M.S. thesis, San Diego State University, San Diego, California, 82 p. Howard, J. D., and Reineck, H. -E., 1981, Depositional facies of high-energy beach-to-offshore sequence: comparison with low-energy sequence: Amer. Assoc. Petroleum Geologists Bull., v. 65, p. 807-830. Inman, D. L., and Chamberlain, T. K., 1960, Littoral sand budget along the southern California coast: Inter. Geol. Congr . , 21st, Copenhagen, Abstra. , p. 245-246 . Inman, D. L., and Jenkins, S. A., 1983, Oceanographic report for Oceanside beach facilities: Technical Report, City of Oceanside, 206 p. International Mathematical Subroutine Language, 1982, FORTRAN statistical programs: International Mathematical Subroutine Language Library, Dallas, Texa s. Joreskog, K. G., Klovan, J. E., and Reyment, R. A., 1976, Geological factor analysis: Elsevier Scientific Publishing Co., New York, 178 p. Kennedy, S. K., and Ehrlich, R., 1985, Origin of shape chage of sand and silt in a high-gradient stream system: Jour. Sed. Petrology, v. 55, p. 57-64. Kuenen, P. H., 1960, Experimental abrasion, 4. Eolian action: Jour. Geology, v. 68, p. 427-449. 89 Kuhn, G. G., Osborne, R. H., Ahlschwede, K. S., and Compton, E. A., 1987, Processes, locations and rates of coastal cliff erosion from 1947 to present, Dana Point to the United States-Mexico border and the stratigraphy of contributing cliffs and bluffs at San Onofre, Camp Pendleton, and Torrey Pines: Technical Report, Los Angeles District, U.S. Army Corps of Engineers, 298 p., 11 plates. Kuhn, G. G., Osborne, R. H., Compton, E. A., and Fogarty, T., in review, Processes, locations and rates of coastal cliff erosion from 1887 to 1947, Dana Point to the Mexican border: Technical Report, Los Angeles District, U.S. Army Corps of Engineers, 283 p., 6 plates. Kumar, N., and Sanders, J. E., 1976, Characteristics of shoreface storm deposits: Modern and ancient examples: Jour, Sed. Petrology, v. 46, p. 145-162. McLaren, P., 1981, An interpretation of trends in grain- size measures: Jour. Sed. Petrology, v. 51, p. 611- 624 . Moss, A. J., 1966, Origin, shaping, and significance of quartz sand grains: Jour. Geol. Soc. Australia, v. 13, p. 97-136. Nardin, T. R., Osborne, R. H., Bottjer, D. J., and Scheidemann, R. C., Jr., 1981, Holocene sea level curves for Santa Monica shelf, California continental borderland: Science, v. 213, p. 331-333. Osborne, R. H., 1985, Coast of California storm and tidal wave study: Littoral zone sediments: Technical Report, Los Angeles District, U.S. Army Corps of Engineers, 148 p. Osborne, R. H., 1986, Oceanside Harbor experimental sand bypass system monitoring program: littoral zone sediments: Technical Report, Los Angeles District, U.S. Army Corps of Engineers, 101 p. Osborne, R. H., Darigo, N. J., and Scheidemann, R. C., Jr., 1983, Potential offshore sand and gravel resources of the inner continental shelf of southern California: State of California, Dept, of Boating and Waterways, 302 p. 90 Osborne, R. H., and Pipkin, B. W., 1982, Geomorphic and sedimentologic analysis for the Oceanside Project: Phase II: Technical Report, Los Angeles District, U.S. Array Corps of Engineers, 121 p. Porter, G. A., Ehrlich, R., Osborne, R. H., and Corabellick, R. A., 1979, Sources and non-sources of beach sand along southern Monterey Bay, California-- Fourier shape analysis: Jour. Sed. Petrology, v. 49, p. 727-732. Przygocki, R. S., Yarus, J. M. , Ehrlich, R., and Onofryton, J. K., 1977, The nature of shape frequency distributions of primary and secondary quartz and the relatinship between size and shape: Southeast Sect. Geol. Soc. Am. Proc., v. 8, p. 250. Redmond, B. T., 1968, The utility of Fourier estimates of grain shape in sedimentological studies: thesis, Michigan State University, E. Lansing, Michigan. Reineck, H. -E., 1963, Sedimentgefuge im Bereich der sudlichen Nordsee: Senckenberg. Naturf. Ges., Abh. 505, 134 p. Reineck, H. -E., Gutmann, W. F., and Hertweck, G., 1967, Das Schlickgebier sudlich Helgoland als Beispiel Schelfablagerungen: Senckenb. Lethaea, v. 48, p. 219- 261. Reineck, H. -E., and Singh, I. B., 1971, Der Golf von Gaeta/Tyrrhenisches Meer. 3. Die Gefuge von Vorstrand-und-Schelfsedimenten: Senckenb. Mar., v. 3, p. 185-201. Scheidemann, R. C., Jr., 1980, Quaternary stratigraphy and sedimentation of the Santa Monica shelf, southern California: unpublished M.S. thesis, University of Southern California, Los Angeles, California, 222 p. Schultz, D. J., 1980, The effects of hydrofluoric acid on quartz grain shape-Fourier grain shape analysis: Jour. Sed. Petrology, v. 50, p. 644-645. Shlemon, R. J., 1979, Late Pleistocene channel of the Santa Margarita River, San Diego County, California: in Geologic guide of San Onofre nuclear generating station and adjacent regions of southern California: Pacific Sect. Amer. Assoc. Petroleum Geologists, Soc. Econ. Paleon. Mineral., and Soc. Econ. Geophysicists, 1979 Guidebook 46, p. A63-A70. 91 Swift, D. J. P., Figueiredo, A. G., Freeland, G. L., and Oertel, G. F., 1983, Hummocky cross stratification and megaripples: a geological double standard: Jour. Sed. Petrology, v. 53, p. 1295-1317. Tekmarine, Inc., 1986, Oceanside littoral cell, Preliminary sediment budget: Technical Report, Los Angeles District, U.S. Army Corps of Engineers, 181 p. Van Nieuwenhuise, D. S., Yarus, J. M., Przygocki, R. S., and Ehrlich, R., 1978, Sources of shoaling in Charleston Harbor--Fourier grain shape analysis: Jour. Sed. Petrology, v. 48, p. 373-383. Walker, R. G., 1982, Hummocky and swaley cross stratification: i_n Walker, R. G., ed. , Clastic units of the Front Ranges, Foothills and Plains in the area between Field, British Columbia and Drumheller, Alberta: International Assoc. Sedimentologists , 11th International Congress on Sedimentology (Hamilton, Canada) , Guidebook to Excursion 21A, p. 22-30 . Walker, R. G., Duke, W. L., and Leckie, D. A., 1983, Hummocky stratification: significance of its variable bedding sequences: Discussion: Geol. Soc. America Bull., v. 94, p. 1245-1249. Yarus, J. M., Brown, P. J., and Ehrlich, R., 1978, A new tool for recent sediment studies--Fourier grain shape analysis: Abstr. EOS, v 59, p. 296. Young, J. M., 1980, Geology of the nearshore continental shelf and coastal area, northern San Diego County, California: unpublished M.S. thesis, San Diego State University, San Diego, California, 140 p. 92 APPENDIX A: VIBRACORE LOGS AND SEDIMENT DESCRIPTIONS. 93 VIBRACORE LOG Core number: 1656 Total core length (cm): 290 Date: Sheet 2/81 of Wmber of core sections:____ Water depth (ft) : _________55 Vertical scale: 1 cm = 25 cm Distance in cm from topof core Descrintion Log 0-83 83-156 156-220 220-290 S i lt y Sand. very fine grained, ranges from s i l t to fin e sand; moderately well sorted; olive black (5 Y 2 /1 ); apparently massive with fain t (oossibly heavy mineral) laminae from 80-82 cm.; very micaceous; gradational lower contact. S i lt y Sand: very fine grained, ranoes from s i l t to fine sand; moderately well sorted; dark gray (N 3 );_ apnarently massive; very s lig h tly micaceous; shell fragments concentrated from 127-129 cm. and 148- 151 cm.; gradational lower contact. Sand: very fine grained, ranges from s i l t to medium sand; moderately well sorted; medium dark qray (N4); apparently massive; very s lig h tly micaceous;, shell fragments rare throughout and concentrated from 206-208 cm.; gradational lower contact. Sand: very fin e grained, ranges from s i l t to medium sand; well sorted: medium gray (N5); apparently massive with a concentrated mass of clasts (1-3 - cm. d ia .) and abundant fine to coarse sand and gravel size shell fragments from 220-231 cm.; s iig h tly micaceous. ^ o - i t (j W * • ' * \r> o L 3 S - , £ 5 Vr- 94 VIBRACORE LOG Cere number: 1675 Tctal core length Cc™): 200 Date: Sheet 2/81 of Number of core sections:____ Water depth (ft) :_________67 Vertical scale: 1 cm = 25 cm Distance in an from too of core Description Log 0-111 111-200 Sand: very fine to fine grained, ranges from s i l t to fine sand; moderately sorted; olive black (5 Y 4 /1 ) ; apparently massive; highly micaceous; SDarse shell fragments with a high concentration from 100-110 cm., grading downward to slig h tly micaceous. Sand: very fin e to fine grained, ranges from s i l t to medium sand; moderately sorted; medium gray (M5)— grading to medium lig h t gray ( N6); predominantly massive with o liv e black (5 Y 2/1) bandinq (possibly due to heavy minerals) from 152-175 cm.; highly micaceous. 95 VTERACORE LOG Core number: 1721 Total core length (cm): 1P 6 Date: Sheet Number of core sections:___ Water depth (ft) :_________5? 2 /SI of Vertical scale: 1 cm = 25 cm Distance in cm trom top of core DescriDtion Log 0-90 90-170 170-180 S i lt y Sand: s i l t to very fine grained; well sorted; o liv e gray (5 Y 2 /1 ) ; apparently massive; s lig h tly micaceous; rare shell fragments; no lower contact. S ilty -S a n d : same as interval 0-90 cm. but contains fin e grain sands; occasional shell fragments with a concentrated pocket from 90-101 cm. Conglomerate: s i l t to gravel in size; very poorly sorted; concentrated mass of cobbles, pebbles, granule and sand with fine sand to gravel size shell fragments; apparently massive. 96 VIBRACORE LOG Core number: 1852 Total core length (cn): Number of core sections: Water depth (ft) :_______ 208 Date: Sheet 2/81 of 55 Vertical scale: 1 cm = 25 cm Distance in an from tapof core DescriDtion LO£ 0-100 100-208 S i1ty-Sand: very fine grained, ranges from s i l t to fine sand; moderately well sorted; o liv e black (5 Y 2 /1 ); apparently massive; s lig h tly micaceous; rare shell fragments with a thin concentration from 51-52 cm.; no lower contact. Sand: dominantly fine grained, ranges from s i l t to — medium sand; moderately well sorted; o liv e black (5 Y 2/1) grading to medium gray ( N5); apparently massive; s lig h tly micaceous; rare shell fragments throughout with moderate concentrations from 100- 120 cm. and 155-170 cm.; clasts (1-3 cm. d ia .) found intermixed with shell fragments. <rO l . " O O ’ I < = > S- .. 97 : l°0|v: VIBRACORE LOG Cere number: 1884 Total core length Cot) •____ 270 Number of core sections: _ Water depth (ft):_______ Date: Sheet 2/31 50 Vertical scale: 1 cm = 25 an Distance in cm from top_of core DescriDtion Log 0-70 70-144 144-207 207-270 S ilt y Sand: very fine grained, ranges from s i l t to fine sand; well sorted; o liv e black (5 Y 2 /1 ); apparently massive with fa in t laminae (possibly heavy mineral) from 54-60 cm.; s lig h tly micaceous; rare shell fragments; no lower contact. S ilt y Sand: same as interval C-70 cm.; very micaceousr gradational lower contact. S ilt y Sand: dominantly very fine grained, ranges from s i l t to fine sand; well sorted; medium dark gray — (N4); apparently massive; very s lig h tly micaceous; rare shell fragments; no lower contact. S i lt y Sand: same as in terval 144-207 cm. 98 VIBRACORE LOG Cere number: 1891 Total core length (cm): 300 Date: Sheet 2/81 of Number of core sections: Water depth (ft) :_______ Distance in cm from top of core 55 Vertical scale: 1 cm = 25 cm Description Log 0-100 S i l t y Sand: dominantly very fine sand and s i l t ; well sorted; o liv e gray (5 Y 3 /2 ); apparently massive; s lig h tl y micaceous; sparse shell fragments; no lower contact. c i . ;' j ' t 100-200 S i l t y Sand: same as interval 0-100 cm.; fa in t mica — laminae from 114-119 cm.; no lower contact. — - i - t 7 ; - 200-300 S i l t y Sand: same as interval 0-100 cm.; medium to _ coarse sand size shell fragments throughout. ; ' _v_. o __ <., . • • • '• ’• > 99 VIBRACORE LOG Core number: 1970 Total core length (cm): 93 Date: Sheet 2/81 of Number of core sections:____ Water depth (ft) :_________45 Vertical scale: 1 cm = 25 cm Distance in cm from too of core DescriDtion Log 0-40 40-93 Sand: very fine grained, ranges from s i l t to fin e sand; well sorted: o liv e gray (5 Y 3 /2 ); sparse shell fragments; apparently massive with in terval 24-40 cm. containing fin e sand to gravel with abundant shell fragments and occasional whole gastropod and pelecypod shells, pebbles anc cobbles (1-8 cm. d i a . ) ; very poorly sorted; sharp lower contact. Sand: medium grained, ranges from s i l t to gravel ; moderately sorted; dusky yellow (5 Y 5/4) with bands of grayish black (N2) from 78-93 cm.; predominantly massive with a bed of very coarse sand from 60-55 cm.; very micaceous; rare shell fragments. 100 VTERACORE LOG Core number: 1979.6 Total core length (cm): 221 Date: Sheet 2/81 of Number of core sections:____ Water depth (ft) :_________S2_ Distance in cm from topof core Vertical scale: 1 cm = 25 cm DescriDtion hog 0-80 80-167 167-197 197-221 Sand: dominantly very fine grained, ranges from s i l t to fine sand; well sorted; o live gray (5 Y 3 /2 ); apparently massive; s lig h tly micaceous; rare shell fragments; no lower contact. S i lt y Sand: same as in terval 0-80 cm. but contains more s i l t and a minor amount of fine sand; sharp lower contact. Sand: very fin e grained, ranges from very fin e sand to g ra v e l, the coarse sand to gravel fractions are dominantly shell fragments; moderately sorted; o liv e gray (5 Y 3 /2 ) ; apparently massive; gastropod, pelecypod shells and other shell fragments heavily concentrated throughout with clasts (1-7 cm. d ia . ); sharp lower contact. Sand: fine grained, ranges from s i l t to fine sand; well sorted; medium lig h t gray (N6); aoparently massive with fa in t (possibly heavy mineral) laminae; very s lig h tl y micaceous; rare shell fragments. 101 VIBRACORE LOG Core number: 1986 Total core length (cn):____ 92 NTmber of core sections:____ 1_ Water depth (ft) :_________ a] Date: Sheet 2/81 of Vertical scale: 1 cm = 25 cm Distance in an trom top of core Description Loe 0-72 72-92 Si 1ty Sand: very fin e sand, ranges from s i l t to medium sand, the coarse to very coarse sand frac tion consists o f shell fragments; moderately well sorted; o liv e black (5 Y 2/1); apparently massive; s lig h tly micaceous; sparse shell fragments with a high concentration of fragments and pelecypod shells from 60-72 cm.; sharp lower contact. Sand: medium grained, ranges from s i l t to very coarse sand; moderately sorted; lig h t o live gray (5 Y 6/1); apparently massive; s lig h tly micaceous; rare shell fragments. 102 VIBRACORE LOG Core number: 2053 Total core length (cm) :____ 0 50 Date: Sheet 2/81 of Number of core sections:____ Water depth (ft) :_________55 Vertical scale: 1 an = 25 cm Distance in cm rrcm top of core Description Log 0-120 120-226 226-250 S ilty Sand: very fine grained, ranges from s i l t to fine sand; moderately well sorted; o live black (5 Y 2 /1 ) ; apparently massive; very micaceous grading downward to s lig h tly micaceous; sparse shell fragments; no lower contact. Sand: very fin e grained, ranges from s i l t to fin e sand, the coarse to very coarse sand fractions contain shell fragments; moderately well sorted; o liv e black (5 Y 2 /1) grading to medium gray (N5); apparently massive; very s lig h tly micaceous; sparse shell fragments with higher concentrations from 120-143 cm. and 170-173 cm.; sharp lower contact. Sand: very coarse grained grading downward to medium to coarse grained, ranges from s i l t to gravel , the very coarse sand and gravel fractions contain abundant shell fragments; poorly sorted; medium gray (N5) grading to yellowish gray (5 Y 8 /1 ); apparently massive with s lig h t graded bedding. ? ■ S' ^ • O , * f c * • % r ' ^ ' l »<- o * < _ • 103 VIBRACORE LOG Core number: Total core length (cm): Date : Sheet 2./ 81 of Number of core sections:____ Water depth (ft) :_________37 Vertical scale: 1 cm = 25 cm Distance in cm rrcm top of core DescriDtion Log 0-70 70-138 138-168 Sand: very fin e grained, ranges from s i l t to medium sand; well sorted; o live black (5 Y 2 /1 ) ; apparently massive; very micaceous; no lower contact. Si 1ty-Sand: same as interval 0-70 cm., but contains more s i l t : sharp lower contact. Cong!omerate: ranges from s i l t to gravel; very poorly sorted; o liv e gray (5 Y 4 /1 ) ; predominant!y massive u n it of sand, gravels (1-8 cm. dia.), and medium sand to gravel size shell fragments; si i ghtly mi caceous . 104

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Creator Cho, Kyung Ha (author)

Core Title Sedimentology of a composite inner-shelf sand body resulting from the resuspension of nearshore sediment by episodic, storm-generated currents: Oceanside, California

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