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Petrofabric analysis of late Precambrian-Cambrian quartzites from southeastern California

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Petrofabric analysis of late Precambrian-Cambrian quartzites from southeastern California

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Content PETROFABRIC ANALYSIS OF LATE PRECAMBRIAN- CAMBRIAN QUARTZITES FROM SOUTHEASTERN CALIFORNIA by Maria Mann Zrupko 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) August 1975 UMI Number: EP58625 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. Dissertation Publishing UMI EP58625 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 LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 UNIVERSITY OF SOUTHERN CALIFORNIA T H E G R A D U A T E S C H O O L U N IV E R S IT Y P A R K L O S A N G E L E S . C A L IF O R N IA 9 0 0 0 7 This thesis, written by Maria M ann Z rup k o under the direction of h.§Zl..Thesis Committee, and approved by all its members, has been pre sented to and accepted by the Dean of The Graduate School, in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE (Geological Sciences) Dean THESIS COMMITTEE CONTENTS Page ILLUSTRATIONS..................... iii ABSTRACT . . • . ............ v INTRODUCTION ........ ................... 1 Purpose of study ••••• ........ .... 1 Previous work ........ ••••• 2 Acknowledgments ........ •••••••••• 9 LOCATION AND STRATIGRAPHY ................. 10 PROCEDURES AND RESULTS..................... 18 Sample preparation ••••••••••••• 18 Microscopic method ••.•••••••••• 18 Petro fabric diagrams •••• 25 Cross-stratified set ••••••• ........ 27 Horizontally-laminated set ............ 33 Massive set •••••••••••...••. 57 Statistical analysis . ..................... 79 DISCUSSION OF RESULTS ........................... 102 CONCLUSIONS...................................... 109 REFERENCES ............................. 110 ii ILLUSTRATIONS Figure Page 1. Index map showing locations of* strati- graphic sections from which oriented samples were collected ........ • • • 11 2. Map showing cratonal (eastern) and mio- geoclinal (central) facies and their relationship to the location of strati- graphic sections • •••••••.••• 13 3-12. Grain fabric diagrams, cross-stratified s e t .................................... 34-32 13-21. Grain fabric diagrams, horizontally- laminated set ...••• •• ........ 58-74 22-31. Grain fabric diagrams, massive set . . . 80-98 Tables Page 1* Correlation chart of upper Precambrian and lower Cambrian units in southeastern Cali fornia .......... 15 2. Location of stratigraphic sections • • • • • 17 3* Sample numbers for each set . ........... * 19 4. Strike and dip of oriented samples and direction of thin section cut • •••••• 20 5# Variables recorded with c axis measurements 22 6. Cross-stratified sets Tabulation showing grain size, shape, angle of extinction and angle between c axis and apparent long axis 29 7# Horizontally-laminated set: Tabulation showing grain size, shape, angle of extinc tion and angle between c axis and apparent long a x i s .......... 34 8, Massive set: Tabulation showing grain size, shape, angle of extinction and angle between c axis and apparent long axis • •••••• 77 9* Average percent distribution by set of each variable measured ..••••.. ........ 106 10., Grain elongation versus c axis orientation • 107 iv ABSTRACT Petrofabric analysis was conducted on samples of* quartzite collected from seven cratonal and miogeoclinal sections of late Precambrian-Carabrian age in the eastern Mojave Desert, southeastern California, The optic axis orientation of 300 quartz grains was measured along with four other variables in each of 29 petrographic thin sections. The purpose was to establish the degree of grain orientation within sample sets displaying cross stratification, horizontal-lamination and apparently mas sive stratification. Samples with megascopically dis tinctive cross-stratification do not show any evidence of preferred grain orientation. Similarly, equal area diagrams of horizontally-laminated and massive sedimentary quartzites do not reveal any symmetry pattern to indicate preferred grain orientation. One sample from the hori zontally-laminated group exhibits slight orthorhombic symmetry. This sample displays fairly good sorting and is mainly composed of equidimensional and unstrained grains. This combination of variables is infrequent among the measured samples, and unfortunately does not provide a satisfactory explanation for the observed preferred grain orientation* Discriminant function analysis of nine variables reveals that there are no significant textural and extinc tion differences either between or among sets of sedi mentary structures* The null hypothesis that the mean values are the same in all three sets is accepted at the 0.05 level of significance* Results of this study show that optic axis measure ments do not indicate any significant alignments, cor- relatable with primary sedimentary structures* This is probably because of the high percentage of equidimensional grains (37 percent average) which have no particular align ment within the transporting current, and tend to obscure grain fabric* Optic axes of unequidimensional quartz grain, how ever, indicate clustering, when related to the direction of long axes* The angle between long axis and optic axes most often measured (39 percent) ranges from 30“^5°* This angle is parallel with the rhombohedral crystal face of quartz, along which cleavage and probably disintegration of grains occur. Parallelism between optic axis and apparent physi cal long axes occurred in 26 percent of the total unequi dimensional grains. An angle of 80-90° was measured in 12.5 percent of the unequidimensional grains. Quartz optic axis orientation by itself does not provide a self-sufficient means for sedimentary petro- fabric studies. INTRODUCTION j | Purpose of1 Study j i I The present thesis is a grain fabric analysis of t sedimentary quartzites of late Precambrian and Cambrian i age using optic axis orientation. The main purpose of this study is to establish the degree of preferred orienta tion within three different sets of primary sedimentary i structures: tabular cross—stratified, horizontally- laminated, and massive quartzites. The results will allow one to ascertain which, if any, of the primary sedimentary ' 1 structures exhibit preferred directions. Preferred orien- j tations indicated by optic axis measurements then can be correlated with other current indicators and used as a tool in paleoenvironmental studies. Massive samples are expected to show the lowest degree of preferred orientation due to turbulence during deposition or postdepositional burrowing. On the other hand, cross-laminated specimens may exhibit preferred I orientations comparable with cross-bed directions. j Secondarily, the purpose of this study is to test I the degree of parallelism between quartz optic axes and direction of elongation, a basic assumption of petro- fabric studies based on measurement of optic axes* Previous Work Grain-orientation studies were long used for various disciplines of geology* Deformational fabric of tectonites may be studied by structural petrologists and used to determine the direction of tectonic forces and stresses* Depositional fabric of current-laid sedimentary rocks is studied by sedimentary petrologists in order to establish the paleo-environment, direction of paleoslopes, paleocurrent and source directions* Grain-orientation studies find practical applications in petroleum explora tion geology through determining trends of ancient sub surface sand bodies* Pairbridge (195*0 recommended the use of depositional petrofabric along with micro-facies for stratigraphic correlations. Grain-orientation studies may be achieved through several methods. Measurement of optic axis of quartz grains, the method used in this thesis, assumes that physical elongation of the grains is parallel with the optic axis (Wayland, 1939)* Dimensional measurements of the long axes of grains and the direction of their preferred elongation are used to determine the trends of sand bodies in recent and ancient sediments. It is established that wave deposited sands have their preferred dimensional orientation perpen- j dicular to the shoreline, fluvial deposits show an align- | ! ment parallel to the current, and wind deposited sand 1 grains lie parallel to the air current (Curray, 1956)* i Measurement of maximum dielectric constant of j quartzitic sands is based on the dielectric anisotropy of quartz* Passage of electric current in the direction of the crystaliographic c axis is faster than in any other direction* By measuring the highest dielectric constant 1 of a quartzite plug, the prevailing grain-orientation may be determined (Arbogast, i960)* Xt was found that di electric anisotropy checks well with results obtained through the measurement of c axes (Shelton and Mack, 1970)*! The distinct advantage of the dielectric method is that it replaces the lengthy and tedious microscopic, grain-by- | grain measurement with an expedient bulk method in which . millions of grains contribute rather than just a few I hundred, which are customarily measured in a thin section* The principle disadvantage of this method is that other properties, such as bedding surfaces, cleavage and fracture, may be superimposed and interfere with the grain ; orientation. The photometer method is another technique used to | 1 measure bulk property of a sedimentary quartzite and is ; based on the measurement of the intensity of light pass- y ing through quartz crystals. The intensity is maximal , j along the optic axis* This method is conducted with i crossed nicols involving a 360 rotation of the micro scopic stage* A gypsum plate is employed to determine the direction of the slow ray, which is also the direction of the optic axis* This study is concerned with the measurement of I I quartz optic—axis orientation related to cross-stratifica- j t tion, horizontal lamination and apparent massive stratifi- j i 1 cation. The microscopic measurement of quartz optic axis j 1 orientation was first used in petrotectonic studies. j Structural deformation tends to reorient the rock com ponents. Preferred orientation of grains may be indica- i tive of the stress field, forming the deformational fabric j I | and may help to decipher obscure structural trends (Sander, 1 1930)* The technique of petrofabric analysis was develop- | I ed by Sander, Schmidt and other Austrian coworkers. They i found that not only crystal grains such as mica and amphi- j j bole tend to align themselves parallel to the foliation ‘ i and lineation in metamorphic rocks, but that more equi- I i ; dimensional crystal grains as quartz and calcite also have 1 1 preferred orientation. Sander (1930) recognized that the components of sedimentary rocks are also symmetrically I related to the current direction in water-laid sediments and magmatic flow in igneous rocks. Sander (l95l) studied the depositional fabrics of limestones and dolomites of the Alps in detail and established that calcite, without k I i exception, shows preferred orientation and the concentra- j tion of optic axes is in the surface of growth. Dolomite J is commonly without preferred orientation, and has a ' girdle concentration of optic axes in the surface of j ! growth. I Attempts were later made to establish the relation- ) ship between physical elongation and optic axis of quartz ! I grains in sedimentary rocks. This was necessary in order j l to allow correlation between grain-fabric studies based on ! measurement of apparent elongation and measurement of optic axes. If related to the elongation, the optic | method is a more accurate means for orientation studies I ' because it eliminates the inadequacy of measuring apparent j frather than true elongation in thin section. With the aid j i of the universal stage, the exact tridimensional position J | of the optic axes may be determined for each grain. This is in contrast with the two-dimensional, apparent long- j i axis orientation of grains as observed on the flat stage. I Wayland (1939) proposed that the direction of elongation of quartz grains is parallel with the direction ! i of the optic axis. He substantiated his hypothesis with ; i I the petrofabric analysis of one thin section from the St. j j Peter Sandstone which was cut along the greatest elonga tion of the grains. The petrofabric diagram showed an i axial concentration of poles of 7*1 percent within a unit ! area of one percent and revealed a good correlation with | the diagram of the direction of physical elongation. The concentration of dimensional long axes was greater; 33 percent within a unit area. To further test the idea of parallelism of optic axes with the physical long axes, Wayland randomly selected 100 grains from a sample of the Jordan Sandstone of Minnesota and examined them using a universal stage. The relationship between optic axes and elongation was consistent with the results from the study of one sample of St. Peter Sandstone. The theory outlined in Waylandfs (1939) paper did not encourage many subsequent studies, supposedly because it was not a well-founded and documented method. The principal drawbacks of this study were that only one formation was analyzed and that a limited number of grains (155) were measured. Orientation analyses based on the dimensional fabric of sand deposits were used more widely to determine transport direction. Sand-grain orientation studies using this technique were undertaken for academic and practical aspects by numerous investigators. Many of these studies were isolated experiments; for example, Dapple and Roming- er (19^5)9 Rowland (19^6), Gryaznova (19^9)» Griffiths and Rosenfeld (1953)* More extensive, experimental grain fabric studies on recent deposits were conducted by Nanz (1955) and Curray (1956) for beach sands and by Rusnak (1957) for 6 stream deposits. The importance of these studies is the I potential prediction of source direction and ancient shorelines and the prediction of trends for reservoir sand bodies based on transport direction, J j Lene and Owen (1969) performed a dimensional grain I orientation study on an ancient sand filled channel with j a well established trend, and found that the resultant j preferred orientation agreed with the known trend of the j 1 channel. They furthermore found that the paleocurrent I direction agreed with the cross-bed directions and that the former showed a more consistent value with a smaller 1 I standard deviation, I Especially valuable is Martini*s (l97l) study on I I quartz grain orientation. He also used the dimensional | I technique and established that the resulting preferred | orientations are close to cross-bed azimuths. Although a | 1 1 large number of thin sections were used and the results i were favorable, Martini still regarded the dimensional ! grain-orientation study as a complementary tool along with ; other directional features (especially cross-bedding), j rather than as gin independent means for establishing cur- | I rent directions. Reliable preferred orientations were ob- i tained especially when the reference plguie for thin j i section was the depositional surface, j I Martini (1971) made several important contributions j I to grain-orientation study: he recognized the presence of I \ imbrication in current laid sediments, including sands, along with the preferred orientation mentioned only for pebble fabric in earlier literature. Imbrication is part i of the grain fabric and may be seen in sections parallel to the depositional dip and perpendicular to the deposi- j tional surface. Imbrication may be important in establish-1 , ! ing current directions. He reduced the number of grains ! i used for measurement. Fifty to 100 measurements were em- I ployed for sections cut perpendicular to the depositional j I surface and 150 to 250 for sections parallel to the de- j i I positional surface, depending on variability of the | measurements observed. This is an improvement compared to I 300-400 counts by other investigators made without known 1 thin section orientation. He established a preferred j I I order and way in which sections should be cut and studied, j First a section parallel to the depositional surface is to | be cut (if possible) and the vector mean of the preferred 1 j orientation determined. The trend of the transporting medium is found in this manner. In order to complete the 1 study, a second section, parallel to the vector mean of thei preferred orientation, is cut. This is cut so that the ! I greatest imbrication angle can be obtained. The direction 1 of imbrication will then define the azimuth of current j I direction together with the preferred orientation of the | I 1 previous section. Martini does not specify what the | direction of imbrication is, although there is a hint that j he means downcurrent imbrication. This is inconsistent with other investigators results (Shelton and Mack, 1970, p. 1109) who found the imbrication to be upcurrent. 1 Acknowledgments ! X extend my grateful appreciation to Dr. Robert H. 1 Osborne, who suggested the topic and gave substantial help j in various phases of this study. I also thank Dr. Donn j S. Gorsline and Dr. Donald F. Palmer for critically read- 1 ! ing the1 manuscript and providing many valuable suggestions.| My thanks^ are also directed to Texaco, Inc., my employer, ; | for granting tuition aid all through my graduate work. | Bob Clover*s help in preparing the thin sections is great- j ly appreciated. My husband, Ernie, was of tremendous help 1 i in encouraging me during my thesis work. I LOCATION AND STRATIGRAPHY The area of study is in the eastern Mojave Desert, San Bernardino County, California (Fig* l)* Outcropping late Precambrian and early Cambrian sedimentary rocks consist mainly of quartzites, which were deposited in the incipient Cordilleran geosyncline (Burchfiel and Davis, 1971)• The formations sampled for this thesis belong to two facies, the eastern cratonal facies and the central miogeoclinal facies (Fig. 2). The majority of the samples for this study were collected from the Tapeats Sandstone of the cratonal facies. Formations of the miogeoclinal facies ares the Noonday Dolomite, Johnnie Formation, Stirling Quartzite, Wood Canyon Formation, and Zabriskie Quartzite (Stewart, 1970) (Table l). Only the Johnnie and Wood Canyon Formations of the miogeoclinal facies are represented in the present study. Predominant structural style is that of imbricate thrust faulting of Mesozoic age. The Clark Mountain Thrust Complex, within which the sampled area lies, is an outstanding example of easterly directed crustal shorten ing. Three overlying thrust plates are recognized by Burchfiel and Davis (l97l)j the Keystone, Mesquite Pass 10 Figure 1. Index map showing locations of* strati graphic sections from which oriented samples were collected* Locality 9 7 6 5 1 k 3 Name of Section Winters Pass Mesquite Pass Taylor Mine Mountain Pass Oro Wash Kelso Marble Mountain N El/A DA C LA R K * MTNS 9 M O U N T A IN ^ pass~Z • 4 35°- AMBO)' o IIG 115 12 Figure 2. Map showing cratonal (eastern) and miogeoclinal (central) facies and their relationship to the location of stratigraphic sections. N El/A DA 35°3 0- MTNS MOUNTAIN. PASS i f CLARK bAKE CENTRAL REGION •4 o ,< KELSOR ^ / AMBOY 0 ew<0 $*' 3 5°- EASTERN REGION C RAT OS^ U5°30 I 34°30l f(5 14 EASTERN REGION CENTRAL REGION TAPEATS S. ZABR1SK1E QUART&l£ WOOD CANYON FORMATION HIATUS STIRLING QUARTZITE JOHNNIE FORMATION NOONDAY DOLOMITE GNEISS AND SCHIST GNEISS AND SCHIST Table 1 Correlation chart of upper Preearabrian and lower Cambrian units in southeastern Cali fornia. (Modified from Stewart, 1970.) 15 and Winters Pass thrust plates. Oriented samples used in this study were collected from the autochthonous Tapeats Sandstone (localities 7j 6* 5, and l), and the Johnnie and Wood Canyon Formations of i the allochthonous Winters Pass plate (localities 9 and 4), | Samples from locality No, 3 are assigned to the Tapeats i i I Sandstone of allochthonous origin (Lobo, 197*0* Sample j localities are shown on Figure 1, and the precise location j of each section is given in Table 2, ! j Stratigraphic relationship of units of the cratonal j facies (Eastern Region) and the miogeoclinal facies I (Central Region) is shown on Table 2 which was modified I from Stewart (1970)* Each unit has a separate strati- ■ graphic nomenclature which reflects lithologic differences,' Correlation between formations of the two facies was made j i by Stewart (1970) and Lobo (197*0 with similar results, ! Based on petrologic and statistical evidence, Lobo (197*0 ' t established that much of the Tapeats Sandstone can be ! correlated with the Wood Canyon Formation and the upper i part of the Tapeats Sandstone with the Zabriskie Quartzite, i Lobo (l97*0 favored a time-transgressive model for the I 1 deposition of the late Precambrian-early Cambrian sedi- 1 t i mentary rocks, I Table 2. Location of stratigraphic sections (after Lobo, 197*0 Section Location Formation Facies Winter* s Pass (9) ; Mesquite ; Pass (7) I Taylor jMine (6) ! * |Mountain [Pass (5) Gro Wash (l) Kelso Hills (4) Marble Mountain (3) 8 km, northwest of Winter*s Pass, Sec, 36, R 11 E, T 19 N 2,5 km east of Mes quite Pass, Sec, 29» T 17 1/2 N, R 13 E 1 km north of Taylor Mine, Sec. 9, T 17 N, R 13 E 6 km northwest of Moun tain Pass, Sec. 35» T 17 N, R 13 E 0.6 km east of Allured Mine, Sec. 22, T 15 N, R 14 E 4 km northwest of Kelso, Sec. 14, 15, T 11 N, R 12 E 3 km northeast of Cadiz, Sec. 12, T 5 N, R 14 E Johnnie Formation Tapeats Sandstone Tapeats Sandstone Tapeats Sandstone Tapeats Sandstone Johnnie Formation Wood Canyon Formation Tapeats Sandstone Miogeoclinal Allochtonous Cratonal Autochtonous Cratonal Autochtonous Cratonal Autochtonous Cratonal Autochtonous Miogeoclinal Alio chtonous Cratonal Alio chtonous PROCEDURES AND RESULTS Sample Preparation Thirty samples were selected from a collection of 559 oriented hand specimens representing fifteen strati graphic sections of Precambrian and Cambrian rocks from southeastern California* The fifteen sections were sampled and studied by Cyril F. Lobo (1974). The selection; of thirty samples for preparation of thin sections was j random; however, a predetermined number of ten samples werel used for each set of the three sedimentary structures: i cross-stratified, horizontally-laminated, and massive j (Table 3)• Thin sections parallel and subparallel to the true strike and dip were cut, one for each hand specimen* | i Table 4 shows the true strike and dip of oriented samples ' and the angle of deviation of thin sections from the strike, i or dip. i Microscopic Method j A five axis universal stage was attached to the petrographic microscope to measure the orientation of optic axes of 300 quartz grains in each thin section* The vari ables recorded along with the azimuth of the optic axis 18 jTable 3# Sample numbers for each set Sample set (sedimentary structure) Sample No# 1-13 1-42 1-44 3-16 Cross-stratified 3-35 3-56 3-60 6-15 6-28 1 .. 7-18. _ 3-22 ; 3-54 ! 3-70 ! 4-67 | Horizontally-laminated 4-70 i 6-11 9-14 9-36 ; ...._ _ 9-50 ; 1-20 3-20 ; 7-24 3-67 Massive-stratification 3-71 3-77 5-20 6-40 : 7-16 j - ...........................................7-50 , ; i r*V-7>r / *?$<' i, Table 4. Strike and dip of oriented samples and directionJbf thin section cut ________________________________________ &__________________ V*-v ' ■ ___________* a V . D*p|ff Strike Dip True True Slab Angular thin thin Set Sample strike dip ? - I ? ? * — / ■ * % j angled direction difference section section 1-15 N 90° E N 0°E - ?& 40° f 66° M 54° Dip -0.4° N 0°E £ o • H 1-42 1-44 S S 65° E •75° E N N 25°E 15°E Strike Strike +0.5° +3.5° S S 65°E 71°E + J 1 < 0 3-16 N 8°E N 82°W M’ s ' r • • O 00 Strike +2.5° N 6°E W O W » H 3-35 N 16°E N 74°W . 53°' ^ Strike 0° N 16°E O 4 - 1 U * H 3-56 N 5°E N 85°W 40° Strike -3.0° N 8°E ° % 3-60 N 8°E N 82°W 48° > ’ s '. Dip -5.0° N 77°W H 4 - > 6-15 N 30°W N 60°E 79° Dip +1.0° N 61°E W 6-28 N 36°W N 54° E 82° * Dip -2.0° N 52°E 7-18 N 25°E N 65°W 38° Dip +1.5° N 67°W 1 3-22 N 10°E N 80°W 64° Dip +6.5° N 86°W 3-54 N 11°W N 79°E 30° Dip -1.0° N 78° E i - H r —1 X > 3-70 N 20°W N 70°E 36° Dip +3.0° N 73°E < 0 < D 4 - 1 4 - » £ < 0 O £ 4-67 4-70 N N 90°E 85°E N N 0°E 5°W 58° 57° Strike Dip +1.0° -4.0° N 89°E N 1°W N * H • H S H C d O H 6-11 N 10°W ' N 80° E 78° ‘ > Dip 0° • N 80° E 9-14 N 25°W N 65°E 62° ^ Strike 0° N 25°W n c 9-36 N 16°W N 74° E 67° ' ' Strike -3.5° N 20°W 9-50 N 52°W N 38° E 55° ^ Strike +6.0° N 46°W 1-20 N 80° E N 10°W 30° < Dip -3.5° N 6°W 3-20 N 10°W N 80° E 44° v ' Dip +1.5° N 82° E 3-67 N 4°E N 86° W 52°;; Dip -1.0° N 85°W < U K k . 3-71 N 15°E N 75°W 44°> Dip -3.5° N 71°W • H 3-77 n 5°E N 85°W • 44? - r ' Dip -0.5° N 85° W C O C O 5-20 N 20°W N 70°E 31 v : Strike +5.0° N 15°W < d 6-40 N 34° W N 56° E • 16% Strike -5.0° * N 39°W 7-16 N 30°W N 60°E 31?;-: - n " Strike -5.0° N 35°W 7-24 N 10"E N 80°W 16ly ;<^V Strike +0.5° N 10°E 7-50 N 5°W N 85°E Dip -1.0° N 84° E and amount of dip are shown on Table 5* Direction of dip i [is shown by an arrow. Grain size was determined with the ! t aid of occular micrometer. Descriptive terms (small, ; medium, large) for grain size were used as a relative > \ qualitative measure within each section. Three average quantitative values measured in mm are indicated for each section to define the descriptive terms. The shape of grains is expressed in axial ratio equal to one for j "equant" grains, 0.66 for ’ ’elliptical” grains, and 0.50 j i for ’ ’elongate” grains. The degree of undulatory extinc- j .tion is the amount of angular separation between optic , axes of various segments of a strained crystal. Blatt, j Middleton, and Murray (1972, p. 27l) was used as a guide j for the description of the extinction. Quartz grains | designated ”non-strained" are homogeneous for their extinc- I tion, those ’ ’slightly strained” show undulatory extinction, j * O 1 the amount of angular separation varying between 2-11 . i i o ! Grains with 12-28 undulatory extinction were described as ! I ’ ’ markedly strained. ” The degree of extinction was measur- j i * i ed on a flat stage. The last variable measured is the j I angle between the optic axis and apparent long axis of the 1 f I grain. This variable was measured for elliptical and j i Q I elongate grains and varies between 0 and 90 • The interval! ! r The measurement of optic axis on the five axis uni- j versal stage was made with the aid of the gypsum plate. j 21 i Table 5* Variables recorded with c axis measurements Grain size Grain shape Extinction - small - medium - large - equant (b/a = l) - elliptical fb/a = 0.66) - elongate (b/a = 0.50) - non-strained (0-2°) ) o Angle between c axis and elongation measured at 5 intervals. The direction of optic axis was determined by parallelism with the direction of slow ray. ,This is valid for all uni axial minerals (Kerr, 1959> P* 90)* The following steps were employed to determine the spacial position of each quartz grain in reference to the long side of the section i that is parallel to the bedding plane, respectively to the j plane of the thin section that is normal to the bedding j I plane: 1. A number of traverses were selected for each | i section, perpendicular to the long side. The number of | t traverses depended on the grain size. For an average graini i size of O.36 mm, five traverses proved to be adequate; for larger grain size (0.96 mm) the number of traverses were I j increased up to seven; whereas, for small grained speci- j I mens a number of three traverses were sufficient to com- | prise the necessary 300 grains* Each single grain along i the pre-selected traverse was measured and tabulated. 2. Every quartz grain was centered at the cross hairs and brought into maximum illumination using crossed 1 nicols. In this position maximum interference color is ; i obtained when observed with the gypsum plate. The inter- ! 1 ference colors range from white to straw to yellow to ; t orange for higher order colors and from green to blue for lower order interference colors. Higher order inter ference colors are observed when the direction of slow ray j 1 of the gypsum plate is perpendicular to the direction of j 23 1 ; the slow ray of the quartz grain, respectively to the optic j axis of it. Conversely, lower order interference colors |are observed when the two slow ray directions are parallel. i • Variation of colors within each group is due to the in- ;clination of the optic axis of the grain in reference to j i the plane of the section. The interference colors can be j j explained by maximum retardation or addition of vibrations i i when slow rays intersect at right angles, and minimum retardation or subtraction for parallel slow rays of the | i crystal and the gypsum plate. If any one group of colors is observed, the position of the slow ray vibration or the ! i I position of the optic axis itself can be inferred. In j ! order to measure the angle of azimuth, the optic axis is | | placed in an east-west position. This is achieved by i rotating the inner circle 45° around the vertical axis \ \ (i.V.) either to the right (in case of lower order colors),i or to the left (higher order colors). Given the diagonal I position of the accessory slot, the 45° rotation will ! bring the quartz grain in total extinction. The single . i then is read on the inner circle and recorded as the azi muth of the quartz grain optic axis. j 3. The dip or inclination of the optic axis within i the plsucie of the thin section was then measured. In order i to do this, the outer circle is tilted around the east- west axis (O.E.-W.) to obtain illumination. The north- i i south axis (N.-S.) is then tilted either way until the ! 24 I grain comes into extinction. In this position the optic axis is found in the horizontal plane of the microscope. The amount of tilting or the dip of the optic axis is read on the upright scale and recorded. An arrow indicates whether the tilting was executed to the right or to the left. This information is essential for the correct plotting of the angle on the stereo net. There is a pos- j i sibility that the optic axis is vertical to the stage of [ i the microscope, in which case we record the complementary | angle. ! i Petrofabric Diagrams ! I I l Haffs (1938) description was used to plot the j poles of optic axes and contour their density. Modifica- j i 1 tions were required for a five axis stage to account for j the west position of the 0° gradation on the inner verti- \ cal circle (i.V.) compared to the south position of same J I on the four axis universal stage. ; A collective diagram for each thin section was made i which showed 300 poles of the measured axes. The pole ! j plots were executed using the Schmidt equal area stereo j net, which is a surface true projection in plane of the lower hemisphere of a reference sphere. On the Schmidt stereo net the circumference is graduated from 0 to 3^0°, which is an exact duplication of the calibrations of the inner circle of the universal stage. This is used to plot ____________ 25 . | the azimuth of* optic axis# Degrees of inclination are jmarked on the east-west diameter from 0 to 90°# These in- I crease from the periphery toward the center# This grada- i !tion agrees with the inner upright circle of the universal stqge on which the inclination of the optic axis is measured# i Using the Schmidt stereo net for each petrographic i i section, the poles of 300 axes are marked on a tracing j i paper. i i In order to determine the percentage distribution : per unit area of poles, the density of the poles is con- i toured. A circle template of 2 cm diameter, representing j 1 percent of the total area, is used which is walked on a 1 I i square centimeter grid# The center of the template is J placed over the intersection of the centimeter lines# Within the circle area of 2 cm diameter, the number of j dots is counted and written at the intersection. This j i operation is carried on moving the template 1 cm at a j time until the whole area of the diagram is covered. The I operation is then repeated in such a fashion that the ' center of the template now coincides with the center of ! | each square# The intermediate density figures help to a more precise contouring. Marginal areas at the circum- j ference are counted with a special template called peri- ! ! meter counter# Contour interval used was 0.5 percent. j I Various patterns were used to show the percent concentra- | tion of poles. The highest concentration of poles in each diagram is represented in solid black; less than 0.5 per cent is shown in white. Crdss-stratified Set Cross-stratification is a frequently observed primary sedimentary structure in cratonal and miogeoclinal sediments of the southern Great Basin (Stewart, 1970)* According to McKee and Weir’s (1953) definition, a cross stratified unit has layers deposited at an angle to the original dip of the formation. PettiJohn et al. (1973) define cross-stratification as a structure confined to a single sedimentation unit, characterized by internal bedding or laminations, called foreset bedding, inclined to the principal surface of accumulation. Cross-beds are the product of down-current migration of sand. The magnitude of cross-stratified units here dis cussed is small to medium (Lobo, 1972). Hand specimens with obvious cross-stratification were selected for orientation study in order to establish correlation be tween megascopic directional features and grain fabric. In thin section they also display visible cross stratification due to an alternation of laminae consisting of sutured quartz grains with floating grains in an abundant matrix; the presence of clean, well-sorted quartz grain layers alternating with poorly sorted layers contain- 27 ing abundant matrix, and alternating layers of large grains with smaller grains. In the ten thin sections examined, matrix is pre sent in amounts ranging from 10 to kO percent. The matrix mainly consists of sericitic material, secondarily ferruginous with some biotite and muscovite filling the interstices between quartz grains. Mineralogically all ten samples are comprised primarily of quartz grains of differing textural character istics. Plagioclase, orthoclase, biotite, muscovite and quartzitic rock fragments are present in various amounts. Usually the total for these constituents does not exceed 20 percent by volume. The grain size of quartz ranges from 0.11 mm to 1.43 mm in the set of ten cross-stratified thin sections examin ed. Grain size for each thin section is given in Table 6. Sorting is poor, and the grains are generally subangular. Apparent shape of grains ranges from equidi- mensional (axial ratio equals 1.0) to elongated (axial ratio equals 0.66), with the following percent distribu tion; 34 percent of the measured grains have an average axial ratio of 1, 25 percent have an average axial ratio of 0.50, and 4l percent have an average axial ratio of 0.66. The majority of the measured grains (66 percent) are unequidimensional by their apparent shape. This makes the cross-stratified group susceptible to preferred 28 Table 6* Cross-stratified set Tabulation showing grain size, shape, angle of extinction and angle between c axis and apparent long axis* 29 E x t i n c t i o n ( i n d e g r e e s ) G r a i n s h a p e ( b / a U n - S l i g h t l y M a r k e d l y A n g l e b e t w e e n c a x i s J . p l i „ O r a I n s i r e i n 7 : 0 , L g n P H a r , E l l i p t . ' * 5 -» a t r a i n e d s t r a i n e d s t r a i n e d a n d a p p a r e n t e i c m g , N g . 5 : . : 0.11 M o u i 1 . 1 : 7 1 L a r g e 1 0 . 5 r , ‘t ’ f 0 ° - 2 ° 2 ° - 1 . 1 ° 1 1 ° ~ 2 3 ° 0 ° - 1 0 ° 3 0 ° - 4 5 ° S C > ° - 9 0 ° O t h e r ! - . 1 5 0 . 3 3 A . V 0 * - t - 110 o o - ® . ■ 4 G 1 9 6 9 1 1 C 2 0 7 1 5 9 4 5 3 3 5 0 3 9 7 2 1 - 7 0 .2 1 1 0 6 0 ? •' ft ” ? -8. 0 , " 4 1 9 " 1 0 6 6 2 1 3 2 1 6 5 122 1 3 3 ° 5 5 O o 7 7 i - 4 4 0 . 1 P 9 0 * 21 1 0 5 0 , 6 " i 2 4 4 7 12 ° 1 5 9 1 2 4 I 7 5 2 6 7 20 3 7 ^ ^ A 0 * 3 6 1 3 " 0 . 1 2 1 1 9 O . S 7 4 4 1 0 5 100 q q 1 7 6 1 0 8 1 6 6 7 6 5 2 3 6 0 3 ~ 3 5 0*1 1 6 1 0 . 1 6 1 9 8 f : •-> 0 * V # -- *• • 9 p C p 3 7 1 7 6 1 3 5 1 . 6 5 0 01 9 0 O / . - P 4* ? 37 0 . 2 6 1 6 : 0 , 6 9 7 0 1 , 4 3 6 2 1.1 0 7 5 ’ ’ 9 7 p 1 100 1 9 6 1 p o j 5 3 - 6 0 0 . 1 9 8 0 0 , 3 2 1 4 8 0 , 4 2 6 ° ' • n c 7 9 1 ; 3 1 6 4 1 2 7 9 66 68 7 O i r . 1 -- 4 6 6 - 1 5 0 . 1 0 1 3 8 0 . 3 7 9 3 0 . 6 4 6 ° 0 9 8 0 ] 7 n 1 P C - A. ^ X 1 3 3 2 8 4 4 8 0 7 1 6 5 A _ ? -1 0 , 1 ” 1 0 8 0 , 3 4 111 0 . 7 4 8 1 8 9 9 2 1 3 4 1 . 3 4 3 ? 4 6 7 0 3 6 6 1 7 * I c 0 , 1 6 1 3 1 0 , 2 6 1 2 ? 0 . 5 8 3 9 100 7 5 1 2 5 1 3 2 1 . 3 7 3 1 8 7 6 5 3 1 6 7 N o , 1 1 5 2 1 1 6 3 66 5 1 0 2 4 7 3 8 1 T * > O J . . - J .. 1 4 8 2 1 3 0 8 210 4 6 6 6 7 1 2 6 7 5 7 2 T u t a i * 7 T O 3 9 ? ? 3 4 2 5 4 1 4 9 4 3 3 2 3 3 4 1 7 7 W • 2 9 5 30 orientation study. Undulatory extinction was noted in all thin sec tions. The angular separation ranges from 2 to 28°. As shown on Table 6, 51 percent of the measured grains have undulatory extinction. The presence of strained grains suggests a provenance from igneous, quartz-bearing rocks and metamorphic rocks. This also was established by Lobo (l972)* Krynine (l94o) inferred that igneous rocks are the source for unstrained and slightly strained quartz grains and metamorphic rocks are the parent rocks for the strongly strained quartz grains with undulous extinction. More recent work by Blatt and Christie (1963), however, shows that the percentage of nonundulatory quartz grains is the same in both plutonic and metamorphic (schist and gneiss) rocks (15 percent). It is difficult to infer the nature of the source by the presence or absence of undula tory extinction. The high percentage (49 percent) of non undulatory quartz grains in the samples examined is prob ably because of the maturity of the rocks rather than an extrusive origin. During transportation and repeated sedi mentation the originally high percentage of unstable un dulatory quartz grains break down and result in a higher proportion of unstrained fragments. Angular separation between the apparent long axis of grains and optic c axis was measured and is tabulated in Table 6. The angle most frequently measured is that 31 between 30 to 45°, which, comprises 34 percent of* the total number of unequiclimensional grains (Table 6). Twenty- three percent of the grains showed a maximum of ten degree deviation in either direction. Only 13*5 percent of the grains had their long axis at 80 to 90° from the optic axis. The remainder of 29*5 percent did not show any preferred angle. These results are consistent with the relationship illustrated in Table 10. The direction of most frequently measured angle (30 to 45°) is the ex pression of the rhombohedral crystal face (lOll) or (Olll). Cleavage, when present, is usually parallel to the rhombohedron face at 38°13* (Dana, 1966) to the optic axis. It is likely that fractured grains break down along preferred planes of weakness and result in grains elongat ed parallel to the rhombohedron crystal face. Fabric diagrams, constructed for each of the ten cross-stratified specimens, do not reveal any particular preferred orientation pattern. The poles are scattered on the surface of the equal area diagram. No symmetry of the most often observed kinds (axial, monoclinic, triclinic and orthorhombic) can be identified. The highest concen tration of poles is 3 * 5 and 3 percent of the total 300 grains per unit area of one percent. This concentration is insignificant. Furthermore, the lower order contours of 2.5, 2 and 1.5 percent value are not concentrically ar ranged around the maxima. The reference plane is the true bedding surface, marked with S on each diagram. The slabs were cut per pendicular to the bedding surface, parallel or subparallel with the depositional strike and dip. The angle of strike or dip and the top of thin section is shown on each diagram. Figures 3 to 12 are the orientation diagrams of each sample of the cross-stratified set studied. Horizontally-laminated Set Horizontal lamination is also a common sedimentary structure in quartzitic sandstones of late Precambrian and early Cambrian age of the southern Great Basin. Horizontal layering may be due to textural, compositional, and/or fabric differences. Laminations in the samples studied are due mostly to textural variations. Clean sandstone laminae alternate with matrix rich layers. Thompson (1937) connected even-laminated sands with beach foreshore en vironment and Allen (1963) with swash-backwash environ ment . The mineralogy of the samples studied consists main ly of quartz (27-89 percent), feldspar (0-1^ percent), and accessory minerals (Lobo, 1972). The amount of matrix varies from 10-75 percent. Grain size ranges from 0.05 to 0.95 mm. Size limits for each individual sample are given in Table 7* Sorting 33 Figure 3» Grain fabric diagram Set: Cross-stratified No. 1-15* Plane of section: N 0° E. Angle between dip and thin section: 0.4 . Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3» 2 and 1.5 percent of measured grains per unit area of one percent. 34 0>; N 0° £ 35 Figure 4. Grain fabric diagram* Set: Cross-stratified No* 1-42* Plane of section: S 65° E, Angle between strike and thin section: 0.5 • Equal area stereo projection of pole of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3* 2,5» 2 and 1.5 percent of measured grains per unit area of one percent. o o o <o o 37 Figure 5« Grain fabric diagram. Sets Cross-stratified No. 1-44. Plane of section: S 71° E* Angle between strike and thin section: 3*5 * Equal area stereo projection of poles of 3G0 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3* 2.5* and 1.5 percent of measured grains per unit area of one percent. 38 T iop 39 Figure 6. Grain fabric diagram. Set: Cross-stratified, No. 3-16. Plane of section: N 6° E. Angle between strike and thin section: 2.5 • Equal area stereo projection of pole of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3* 2.5* 2 and 1.5 percent of measured grains per unit area of one percent. S Ct-tue bec/c/mo) N G° £ 41 Figure 7* Grain fabric diagram. Sets Cross-stratified, No. 3-35* Plane of sections N 16° E* Angle between strike and thin sections 0 . Equal area stereo projection of pole of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3* 2.5» 2 and 1.5 percent of measured grains per unit area of one percent. Figure 8 Grain fabric diagram. Set s Cross-stratified, No. 3-56. Plane of sections N 8° E. Angle between strike and Q thin section: 3 • Equal area stereo projection of pole of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3* 2.5* 2 and 1.5 percent of measured grains per unit area of one percent. S C true bec/dmo) q 45 Figure 9# Grain fabric diagram. Set: Cross-stratified, No. 3-60. Plane of section: N 77° W. Angle between dip Q and thin section: 5 • Equal area stereo projection of pole of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3* 2.5» 2 and 1.5 percent of measured grains per unit area of one percent. top © S C true beda/ino) 0 © Figure 10. Grain fabric diagram. Sets Cross-stratified No. 6-15* Plane of section: N 6l° E. Angle between dip and thin sections 1 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3* 2.5* 2 and 1.5 percent of measured grains per unit area of one percent. 48 6-15 S Cit'UQ bedding) N 61° E arm 03 49 Figure 11. Grain fabric diagram. Set: Cross-stratified No. 6-28. Plane of section: N 52° E. Angle between dip and thin section: 2 . Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3 (maximum concentra tion in solid black), 2.5t 2, and 1.3 percent of measured grains per unit of one percent. 50 0 S Ctrue beef ding) N 52° E L o 51 Figure 12. Grain fabric diagram. Set: Cross-stratified No. 7-18. Plane of section: N 67° W. Angle between dip and thin section: 1.5 • Equal area stereo projection of pole of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3* 2.5* 2 and 1.5 percent of measured grains per unit area of one percent. 7 - / 8 C tru e b e d d in g ) /V S7a I 53 Table 7* Horizontally-laminated set* Tabulation showing grain size, shape, angle of extinction and angle between c axis and apparent long axis* 5h E x t i n c t i o n ( i n d e g r e e s ) G r a i n s h a p e (b/a) t i n - S I i g h t l y M a r k e d l y A n g l e b e t w e e n c a x i s S a m p ] c . G r a u ■ i O p M i r l * ' p a kj u U x -. s . * Ellipt. Ei - o n g • s t r a i n e d s t r a i n e d s t r a i n e d a n d a p p a r e n t e l o n g . N o » S m a l 1 M e d i u m c i X 7 , v ' 1 0 . 5 0 . 66 0 ° - 2° 2 ° - 1 1 ° 1 1 ° - 2 8 ° 0 ° - 1 0 ° 3 0 ° - 4 5 ° 8 0 ° - 9 0 ° O t h e r o 9 7 0 , 1 0 0 . 1 5 0 , 3 0 1 6 5 1 1 7 1 8 3 2 39 I -5 9 202 p. o 1 7 9 5 7 6 9 2 5 6 7 Q C ■ * - * * ; - f 0 . 2 9 1 7 p. r * U « .3 / 1 3 2 0 . 6 4 1 5 1 9 9 1 0 1 101 1 9 0 9 3 1 7 6 0 7 4 22 4 6 3 - 7 0 0 . 2 0 0 7 0 , 3 6 1 70 A ” o 7 7 1 5 4 50 9 6 2 5 0 4 0 10 3 8 6 7 1 7 2 4 4 - 6 7 0 . 0 6 1 1 7 1 0 - # X , • - - 1 . 3 5 0 . 2 1 a 1 4 3 69 O O 1 5 7 1 3 5 8 4 4 8 2 2 3 1 R 4 - 7 0 0 . 0 5 1 2 7 0 . 0 8 1 i X * - * X . 0 . 1 4 1 7 9 9 9 93 1 0 8 2 5 0 4 4 6 5 5 5 7 1 5 7 4 6 - 1 1 0 . 2 6 9 3 0 . 4 0 1 1 3 0 . 6 9 8 9 1 7 ? x u . . 4 3 50 1 2 8 1 3 1 1 4 1 2 8 4 2 9 1 2 2 0 " 3 9 - 1 4 r> n r m . # v O A | 1 0 . 1 7 1 4 0 i i n ,i. J ^ “7 1 1 4 106 o n - . 9 U 1 7 0 1 1 6 1 4 5 9 4 9 2 3 5 5 9 - 3 6 n o s 0 0~ n i o 1 7 5 1 1 7 Q 1 2 5 64 111 1 2 4 1 6 4 1 . 2 4 0 7 0 2 9 3 6 9 - 5 0 n i s • y » X _ / n /• 7 f \ o c, 2 3 7 1 6 1 4 0 4 8 112 6 4 O C ) 1 3 7 5 1 7 3 I S 1 8 N o . T o ' t i 1 1 6 9 /, - > 1 0 3 4 0 C A O " 7 1 o I C "]7 4.0 6 2 0 23 1 0 0 3 O 1 5 3 8 0 7 9 2 1 3 4 o /. o 4 4 6 6 3 2 1 9 4 7 7 7 0 1 ? 3 5 1 7 7 i s g e n e r a l l y g o o d , r o u n d n e s s i s f r o m s u b r o u n d e d t o r o u n d e d a n d t h e s a n d g r a i n s o f t e n f l o a t i n m a t r i x . O p t i c a l l y c o n t i n u o u s q u a r t z o v e r g r o w t h s a r e f r e q u e n t i n a s m u c h a s t h e o u t l i n e o f t h e w e l l - r o u n d e d p a r e n t g r a i n c a n o f t e n b e n o t e d . A p p a r e n t s h a p e o f g r a i n v a r i e s f r o m e q u i d i m e n s i o n a l t o e l o n g a t e d ( T a b l e 7 ) * S i x t y p e r c e n t o f t h e m e a s u r e d g r a i n s a r e u n e q u i d i m e n s i o n a l w i t h t h e f o l l o w i n g r e l a t i o n s h i p b e t w e e n t h e a p p a r e n t l o n g a x i s a n d c a x i s . T h e m a j o r i t y ( 7 8 p e r c e n t ) c l u s t e r a r o u n d t h r e e v a l u e s . T h i r t y - n i n e p e r c e n t s h o w a n a n g u l a r s e p a r a t i o n f r o m 3 0 - ^ 5 ° * T h i s i s s i m i l a r t o t h e c r o s s - s t r a t i f i e d s e t , a n d i s p r o b a b l y d u e t o t h e e l o n g a t i o n o f t h e q u a r t z g r a i n s i n t h e d i r e c t i o n o f t h e r h o m b o h e d r a l c r y s t a l f a c e l y i n g a t 3 8 ° 1 3 * t o t h e o p t i c a x i s . P a r a l l e l o r s u b p a r a l l e l ( 0 - 1 0 ° ) g r a i n s a r e p r e s e n t i n 2 7 p e r c e n t . o f t h e o b s e r v a t i o n s , a n d 1 2 p e r c e n t o f t h e g r a i n s h a d a n a n g l e o f 8 0 - 9 0 ° b e t w e e n t h e o p t i c a x i s a n d a p p a r e n t l o n g a x i s . T h e r e m a i n d e r o f 2 2 p e r c e n t d i s p l a y e d n o a p p a r e n t c l u s t e r i n g . S t r a i n e d g r a i n s ( w i t h u n d u l a t o r y e x t i n c t i o n ) p r e v a i l o n l y i n t h r e e s e c t i o n s . I n s i x o f t h e s e c t i o n s t h e g r a i n s a r e p r e d o m i n a n t l y u n s t r a i n e d . F o r t h e e n t i r e s e t , 5 7 p e r c e n t i s u n s t r a i n e d a n d k “ } p e r c e n t h a s u n d u l a t o r y e x t i n c t i o n r a n g i n g f r o m 2 - 2 8 ° , T h i s i s i n d i c a t i v e o f t h e m a t u r i t y o f t h e o r t h o q u a r t z i t e s w h i c h w e r e d e p o s i t e d o n a s t a b l e s h e l f w i t h s u b s t a n t i a l r e w o r k i n g ( L o b o , 1 9 7 2 ) , 56 O r i e n t a t i o n d i a g r a m s , c o n s t r u c t e d f o r e a c h o f t h e n i n e t h i n s e c t i o n s , d o n o t s h o w a s i g n i f i c a n t c o n c e n t r a t i o n o f p o l e s t o i n d i c a t e p r e f e r r e d a l i g n m e n t . T h e h i g h e s t c o n c e n t r a t i o n i s f o u r p e r c e n t o f t h e t o t a l o f 3 0 0 g r a i n s p e r u n i t a r e a o f o n e p e r c e n t . F u r t h e r m o r e , t h e r e i s n o s y m m e t r y p a t t e r n r e c o g n i z a b l e w h i c h i s s i m i l a r t o t h e c r o s s - s t r a t i f i e d s e t . O n e s a m p l e , N o . 3 - 7 0 ( F i g . 1 3 ) , s h o w s a w e a k o r t h o r h o m b i c s y m m e t r y . T h e p e r i p h e r a l g i r d l e p a t t e r n i n d i c a t e s t h a t t h e m a j o r i t y o f t h e g r a i n s a r e a l i g n e d w i t h i n t h e p l a n e o f t h e t h i n s e c t i o n w h i c h i s t h e p l a n e o f t h e d i p . T h e d i p d i r e c t i o n i s N 7 0 ° E . A n a l m o s t e a s t - w e s t t r e n d i n g c u r r e n t d i r e c t i o n c a n b e i n f e r r e d f r o m t h e s y m m e t r y p a t t e r n o f s a m p l e N o . 3 - 7 0 . T h i s o b s e r v a t i o n i s c o n s i s t e n t w i t h S t e w a r t * s ( 1 9 7 0 ) r e s u l t s , w h o u s e d t h e d i p o f c r o s s - s t r a t i f i c a t i o n t o i n f e r g e n e r a l l y w e s t w a r d d i r e c t e d p a l e o c u r r e n t s i n t h i s r e g i o n . T h e p e t r o f a b r i c d i a g r a m f o r e a c h h o r i z o n t a l l y - l a m i n a t e d s a m p l e i s p r e s e n t e d o n F i g u r e s 1 4 t o 2 1 . M a s s i v e S e t U n s t r a t i f i e d o r t h o q u a r t z i t e s a r e a l s o a c o m m o n t y p e o f s e d i m e n t a r y s t r u c t u r e i n t h e s o u t h e r n G r e a t B a s i n ( L o b o , 1 9 7 * 0 • L a c k o f p r i m a r y d e p o s i t i o n a l s t r u c t u r e i s e v i d e n t i n m i n e r a l o g i c a l l y a n d t e x t u r a l l y h o m o g e n e o u s d e p o s i t s . M a s s i v e u n i t s m a y b e g e n e r a t e d b y p r o c e s s e s o f s h o r t d u r a t i o n s u c h a s f l o o d s a n d s t o r m s w i t h a r a p i d s e t t l i n g o f 57 Figure 13# Grain fabric diagram. Sets Horizontally-laminated No. 3-70 Plane of sections N 73° E. Angle between dip and thin sections 3 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3* 2.5, 2 and 1.5 percent of measured grains per unit area of one percent. 58 3-70 S C true beddino) N 73°£ 59 Figure 14. Grain fabric diagram. Set: Horizontally-laminated No. 3-22. Plane of section: N 86° W. Angle between dip and thin section: 6.5 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent k (maximum concentra tion in solid black), 3*5* 3* 2.5, 2 and 1.5 percent of measured grains per unit area of one percent. 60 S C£fue hedc/mo) I \ 61 Figure 15* Grain fabric diagram. Sets Horizontally-laminated No. 3-5^* Plane of section: N 78° E. Angle between dip and thin sections 1 . Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3* 2*5» 2 and 1.5 percent of measured grains per unit area of one percent. 62 Figure 16. Grain fabric diagram Set: Horizontally-laminated No. 4-67 Plane of section: N 89° E. Angle between strike and tbin section: 1 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con- tours represent 3*5 (maximum concen tration in solid black), 3* 2.5* 2 and 1.5 percent of measured grains per unit area of one percent. 64 S Ctrue bec/dina) N 89°£ Figure 17# Grain fabric diagram. Set s Horizontally-laminated No. 4-70 Plane of sections N 1° ¥. Angle between dip and thin section: 4 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 4.0 (maximum concen tration in solid black), 3*5, 3*0, 2.5, 2.0 and 1.5 percent of measured grains per unit area of one percent. 66 4-70 S C ttue bedding) n r w 67 Figure 18 Grain Fabric diagram Set J Horizontally-laminated No. 6-11 Plane of section: N 80° E, Angle between dip and thin section: 0 . Equal area stereo projection of poles of 300 quartz grain optic axes* Con tours represent 3 * 0 (maximum concen tration in solid black), 2.5» 2*0 and 1*5 percent of measured grains per unit area of one percent* 68 6 - // ^STln/e bec/d/no) _ A 30° £ 69 Figure 19* Grain fabric diagram. Set; Horizontally-laminated No. 9-1^ • Plane of section: N 25° W. Angle between strike and thin section: 0 . Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3«0, 2.5» 2.0 and 1.5 percent of measured grains per unit area of one percent. 70 o . • ( D .(O O ,9 fit'u e bed<Ji ng2_JL£JL 71 Figure 20. Grain fabric diagram Set: Horizontally-laminated No. 9-36. Plane of section: N 20° ¥. Angle between strike and thin section: 3*3 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*3 (maximum concen tration in solid black), 3*0, 2.3* 2*0 and 1.5 percent of measured grains per unit area of one percent. 72 73 Grain fabric diagram. Set: Horizontally-laminated No. 9-50 Plane of section: N 46° ¥. Angle between strike and thin section: 6 • Equal area stereo projection of poles of* 300 quartz grain optic axes* Con tours represent 3*5 (maximum concen tration in solid black), 3*0, 2*5, 2.0 and 1.5 percent of* measured grains per unit area of* one percent. 74 9 - 5 0 S C tru e b eddin g) N 5&°IV 75 detritus from suspension. Sheet sands also may be pro duced by slow and continuous sedimentary processes with a uniform sediment supply and stable sea level over a stable shelf environment. The massive quartzitic sandstones studied have a homogeneous appearance under the microscope. They are characterized by fair to good sorting and angular grains which suggests the proximity of the source. Lobo (1972) postulated that textural and mineralogical maturity varia tions may be related to an unstable tectonic environment. Matrix is present in lesser amounts than in the previously discussed sets. The volume of matrix ranges from 0 to 30 percent, and averages less than 10 percent. Optically continuous overgrowths on quartz grains are fre quent and is probably a result of diagenetic recrystalliza tion. Grain size ranges from 0.06 to 1.16 mm. Sixty- three percent of the grains are equidimensional (Table 8)• The latter should favor the presence of preferred orienta tion which, however, was not observed. One sample, No. 3-77» exhibits a good visual apparent alignment of grain long axes parallel to the long side of the thin section. The petrofabric diagram, however, does not show a strong symmetry pattern which would indicate a preferred orienta tion of optic axes. Over 50 percent of the total number of measured 76 Table 8. Massive set. Tabulation showing grain size, shape, angle of extinction and angle between c axis and apparent long axis. 77 S a m p l e N o . H r a I n f i i . 7 € : i n m r : O r a i n l i q u i d i r ; 1 . 1 s h a p e ( b / a ) L l l i p t . E l e n g , 0 . 5 ?»66 E n t i n c t U n - s t r a i n e d 0 0 - ? 0 i o n ( i n c s S l i g h t l y s t r a i n e d 0 0 - 7 1G . S A A i i L , M a r h e d l y a t r a i n e d 1 1 ° - 2 8 ° A n g I a b e t r e e a n c a i . a a n d a p p a r e n t e l o n e . S r a a l 1 M e d i u m i C l 1. a \... 0° - 10° 3 0 ° - 4 5 ° e p ° - 9 0 ° O t h e r 1-20 0 , " 3 p p c : l a * A . P 0 „ 5 ° R Q 7 - ? O 6 3 ' ■ 01 1 4 0 » R O 20 2 6 3 1 7 5 7 9 5 2 4 3 3 7 - 0 0 t \ • . f \ 0 6 C J T # a ] A 6 7 ~ 1 o q ‘ 1 D X .... - 8 5 9 6 1 3 6 I 0 4 6 0 6 2 S 4 1 7 ] ^ 3 - 1 7 0 . O S 0.12 0 , 1 6 1 1 6 1 0 4 5 0 1 1 C ' 6 4 7 1 O i n o o p 1 1 1 - X 3 0 - 5 - k I S 3 7 7 7 p . •? o V « A . 0 . 2 5 0 , 3 6 1 C 7 ] p i 9 2 1 O 3 8 1 7 v ''; q q a 9 6 9 3 7 7 4 1 r LQ A O O . - 7 - 0 . 0 6 0 . 1 7 0 . 3 " 1 3 1 4 0 1 7 1 A ; o X 1 : m - 1 1 8 0 7 0 n 7 ■ i . 1 7 9 1 P Q 1 7 S . , . O p a 01 • - * — 3 - o p 7 n f , ■ ' • « ' o °6 ’ 5? n / , 5 3 1 5 3 r5 7 * 7 H — 5 1 c 0 9 ^ A 0 e „ ?, r i 0 . 3 6 0 . 4 2 0 , 6 9 7 r 10? 1 1 6 * f \ o 101 O . p O 1^7 91 4 3 n 1 O 0 3 1 I r . 0 . 3 2 0 . 4 3 A “ C . j-7 A ' 1 ' A 1 ^ ? 100 O " 7 3 S'- O 9 4 7 / . O O 1 8 n o p ■ * > o * - • ' — - n . 6 3 o , 0 4 r - 9 5 - . 1 ; 66 5 0 c O A A 7 c /. p 6 0 p p x ^ 3 8 “7 - ” P 0 . 01 / 9 q c - S ' . • * . . . ) r o 1 4 0 - p - 7 7 T 0 6 4 1 1 3 . 1 T *7 1A 6 9 7 9 O 7 • _ tr 2 3 N o , " O a ; 1 7 1 0 1 ? 1 0 ° r 7 2 9 a 1 4 £ 6 1 2 ‘ 7 " ’ 2 3 7 5 1 2 8 4 7 7 O p . 3 1 7 T o t a l 2 6 . 5 o p r - • * . a 3 4 . 0 3 6 . 5 2 4 . 5 o S', A . 4 9 . 5 / . 9 “ 9 . 0 2 7 . 0 4 4 , 5 1 2 . 0 1 6 . 3 grains are strained (Table 8)• The angle between c axes and apparent long axes is between 30-45° for 44.5 percent of the unequidimensional grains parallel with the rhombo- hedral crystal face. Parallel or subparallel (0-10°) optic axes and long axes were observed for 27 percent of the grains. Only 12 percent showed 80-90° separation of the two axes. No preferred angle was observed for 16.5 percent of the grains (Table 8). Fabric diagrams of each of the ten massive samples are shown in Figures 22 to 31# No particular symmetry can be identified. Where axial symmetry of poles is present, the concentration of poles per unit area is not sufficient ly large to be significant. Statistical Analysis Discriminant function analysis on the three sample sets was performed using nine variables. The purpose of this statistical technique is to establish whether tex tural and optical characteristics (grain size, shape and extinction) are suitable variables to distinguish among various sets of sedimentary structures. Discriminant function analysis requires that the available data be classified \ priori (Kendall, 1948) by a certain criteria. Such a requirement is satisfied since there are three well-defined sets distinguishable by their primary sedimentary structures. Figure 22. Grain fabric diagram* Sets Massive No* 1-20* Plane of sections N 6° ¥. Angle between dip and thin sections 3*5 ♦ Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*0 (maximum concen tration in solid black), 2.5* 2.0 and 1.5 percent of measured grains per unit area of one percent. 80 1-20 A / 0 °yz 81 Figure 23. Grain fabric diagram. Set: Massive No. 3-20. Plane of section: N 82° E. Angle between dip and thin section: 1.5 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*0 (maximum concen tration in solid black), 2.5» 2.0 and 1.5 percent of measured grains per unit area of one percent. 82 3-20 S C 3/-ue h e . c / c / / n Q ) N S 2 ° E 83 Figure 24. Grain fabric diagram Set: Massive No. 3-67* Plane of section: N 85° W. Angle between dip and thin section: 1 . Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3*0» 2.5* 2.0 and 1.5 percent of measured grains per unit area of one percent. 84 S ( i t u a b e e f c / i n Figure 25* Grain fabric diagram. Set: Massive No. 3-71* Plane of section: N 71° W. Angle between dip and thin section: 3*5 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3*0, 2.5* 2.0 and 1.5 percent of measured grains per unit area of one percent. 86 • -^5* Cttue bec/c/fm. 87 Figure 26. Grain fabric diagram. Set! Massive No. 3-77* Plane of sections N 85° W. Angle between dip and thin sections 0.5 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3*0, 2.5* 2.0 and 1.5 percent of measured grains per unit area of one percent. 88 w CD. SCt/'ue bedc/i no) N 8S° IV © CD Figure 27. Grain fabric diagram. Sets Massive No. 5-2. Plane of section: N 15° W. Angle between strike and thin section: 5 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3*0, 2.5> 2.0, and 1.5 percent of measured grains per unit area of one percent. N ! S ° W 91 Figure 28, Grain fabric diagram. Sets Massive No, 6-4, Plane of section: N 39° W. Angle between strike and thin section: 5*0°* Equal area stereo projection of pole of 300 quartz grain optic axes. Con tours represent 2,5 (maximum concen tration in solid black), 2,0 and 1,5 percent of measured grains per unit area of one percent. G - 4 0 <SCtf-ue hecfcf/. no) N 3 9°W 93 Figure 29* Grain fabric diagram. Sets Massive No. 7-16. Angle between strike and thin section: 5 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3*0» 2*5» 2.0 and 1.5 percent of measured grains per unit area of one percent. 9^ 7' !G 95 Figure 30. Grain fabric diagram. Sets Massive No. 7-24. Plane of section: N 10° E. Angle between strike and thin sections 0.3 • Equal area stereo projection of pole of 300 quartz grain optic axes. Con tours represent 4.0 (maximum concen tration in solid black), 3*5, 3*0, 2.3, 2.0 and 1.5 percent of measured grains per unit area of one percent. 7 - 2 4 S C tr u e b e d d in g ) N lo°E 97 Figure 31* Grain fabric diagram. Set: Massive No. 7-5# Plane of section: N 84° E. Angle between dip and thin section: 1 • Equal area stereo projection of poles of 300 quartz grain optic axes. Con tours represent 3*5 (maximum concen tration in solid black), 3*0, 2,5» 2.0 and 1.5 percent of measured grains per unit area of one percent. 98 Sedimentary structures represent environmental indicators dependent on the site of deposition, energy of the depositing current, and nature of source. Resulting deposits may have certain textural characteristics that define one or more sedimentary structures. For example, cross-stratified sandstones may consist predominantly of unequidimensional grains of similar sizes, whereas massive sandstones may be mostly equidimensional with differing sizes. This may be a hypothesis based on the suscept ibility of certain textures and fabrics to form correlat- able sedimentary structures. If such a hypothesis were true, it would provide a geological tool for the correla tion between sedimentary structures and grain texture. This may be useful to classify future samples of unknown sedimentary structures by textural criteria. In this study it was attempted to define textural and optic variables characteristic of observed sedimentary structures. The University Computing Center at the University of Southern California was used to perform a discriminant function analysis. Two programs, BMD01D and BMD05M (Dixon, 1967) were employed. The program BMD01D (Simple Data Description) was run for raw and percentage data matrix for each of nine variables. The mean, standard deviation and variance were computed within this program. In order to establish significant differences between and among 100 groups, the program BMB05M (Discriminant Analysis Between Groups) was run. Mean scores for each variable from each group were analyzed using the cross products of deviation from means for each group and inverse dispersion matrix. The level of significance was equal to 0.05* The null hypothesis stated that the mean values are the same in all three groups for the nine variables ob served. The null hypothesis was tested with a generalized Mahalanobis D-square test. The resultant value was 24.25. This value was used as a chi-square test with 18° freedom. The null hypothesis was accepted at 0.05 level of signifi cance. Consequently, there is no statistically signifi cant difference among the three sample sets based on tex ture and extinction. The printout of the two programs is on file at the Sedimentary Petrology Laboratory at the University of Southern California, Los Angeles. 101 DISCUSSION OF RESULTS The grain orientation study performed on three sets of sedimentary structures of orthoquartzites did not demonstrate any significant preferred orientation of quartz optic axes. The presence of a conspicuous lineament was expected at least for the cross-stratified set which indi cates westerly paleocurrent directions (Stewart, 1970, p, 67)* Dimensional particle orientation study was not con ducted, but it is suspected to be present, given the good apparent visual alignments of grains observed in both cross-stratified and horizontally-laminated specimens. Indeed, it is expected that physical shape of the grain, precisely its elongation, is most decisive in the deter mination of the orientation patterns. Unequidimensional grains tend to align themselves in response to the direc tion of the depositing current, and most often the elonga tion is parallel to the current direction. The samples studied proved to satisfy the require ment that unequidimensional grains comprise more than 50 percent of each sample. An average of 63 percent of the measured grains are oval to elongate for their apparent shape (axial ratio; b/a = 0.5-0.66). 102 In order to obtain more conclusive results, reflect ing grain fabric, one has to measure either physical elonga-r tion or employ it in conjunction with the direction of optic axis. The present study was based on the assumption that reasonable coincidence of these two directions exists. Parallelism between dimensional long axis and optic axis (or crystaliographic c axis) was suggested by Wayland (1939)* He proposed that hardness and resistance to abrasion of quartz grains is greater in the direction of the crystallographic c axis. Results of Wayland*s work substantiated his hypothesis; the elongation of the quartz grains studied by him were parallel with the optic axis. The results of this thesis demonstrate that para- lelism is not the only and perhaps not the prevailing relationship in these samples. Dominant relationship observed in all three primary sedimentary structures is that of an angle between 30-45°. This kind of angle existed in 39 percent of the unequidimensional grains measured. Secondly, an average of 26 percent of the total grains showed parallelism of the long axis and c axis. The third highest percentage observed is a 90 or near 90° angle between the two directions (12.5 percent). Results concerning the relationship of the dimen sional long axis and c axis are consistent with those of many earlier workers. Conclusions at which various authors arrived when they examined this relationship are 103 shown on Table 10. The angle most often encountered is 40°. This may be the result of the differential hardness in the direction of the rhombohedral (lOll) crystal face, along which cleavage most often occurs. Xngerson and Ramish (19^2) conducted an experiment, the result of which was that crushed quartz grains in a mortar broke along the rhombohedral face. It is indeed expected that quartz grains disintegrate along the prevailing cleavage system. Dana (1966) and other authors of mineralogy manuals observed the frequent occurrence of cleavage at 38013* from the c axis (lOll), Rarely, cleavage may develop parallel to the prismatic crystal face (1010) in which case Wayland's (1939) hypothesis may hold. It is probable that both situations exist and quartz grains break along both crystal faces, depending on the develop ment of the cleavage system. The prevailing 38° direction (average from 30-45°) did not result in an obvious symmetry pattern due to fol lowing reason. Although 39 percent of the measured un equidimensional grains are in this category, when the total number of grains is considered this proportion is only 23 percent. Owing to the complex relationship of long axis and optic axis, it is assumed that dimensional grain orienta tion studies are more efficient technique to obtain paleo- current directions. It is known that the alignment of quartz grains in a depositing current is a function of the shape of the grain which, in turn, is dependent upon the source and the mode of abrasion during transportation. Igneous plutonic rocks, which in this case constitute one major source, often release equidimensional grains; meta mo r phi c rocks (the other major source) may free prismatic grains. The equidimensional grains will possibly become spherical during transportation, will roll and be de posited independently of the c axes. Some of these grains may disintegrate along the rhombohedral crystal face. Elongation of the latter will be determined by the (lOll) direction and will be deposited parallel to the current direction. Prismatic grains, released mainly from meta- morphic rocks, probably preserve their original shape dur ing transportation and may become deposited either parallel or perpendicular to the transporting current. A correla tion between source and optic axis direction may be at tempted. Approximately 39 percent of the unequidimensional grains in the present study are in a class whose elongation is parallel with the rhombohedron face (Table 9)» and they possibly originated from igneous intrusive rocks. About 38 percent of the grains exhibit parallel and perpendi cular position of the two axes. These may have originated from metamorphic rocks. It is difficult to use undulatory extinction to determine the provenance because of the high maturity of 105 extinction (in degrees) Grain shape (b/a) Un Slightly Markedly Angle between c axis Sample Grain size in r 1 girl din. Elli, # 1 o_. strained strained strained and apparent eloisg. set: Small Medium 1 0. 0° - 2° pO.1 ) O 0°-10° 30°“45° 50°-90° Other Cl C 3- s tt'*•;fled m 30 -59 n ! ~ or c * * 49 43 £ 23 34 13,5 29,5 Horizontal lamination n - • • 1 o CO o ? CM 57 • 5 / , Pi _ > ~r ■ > 9"? on i o ? ^ Massive 20,3 39* 5 o —■ J f 36,5 24* 3 ■ 0 - O ; 49.5 42.5 S 27 44.5 12 16,5 T o t a 1 a v e r a g e 1 e . 33,3 25,5 23.5 37.5 9 0 52 40 3 26 39 12.5 99 c percent distribution by set of each variable oeasured i r \ C . Table 10. Grain elongation versus c axis orientation Grain elongation vs c-axis Medium angle Parallel ( k 0 ° ) High angle Author X X X X X X Sander (1930) X X xxx X Griggs-Bell (1938) xxx X X X Wayland (1939) X X xxx X Schuman (19^+2) X xxx X X Ingerson-Ramisch (19^2) X X xxx X Engelhardt (19^-4) X xxx X X Rowland (1946) X xxx Bonham (1957) X X xxx X Pluegel (1953) xxx X X X Turnau-Morawska (l95^) X X xxx X Bloss (1957) xxx Abundant xx Common x Rare Table reproduced from Zimmerle and Bonham (1962). 107 the orthoquartzites. Unstrained grains are present in excess of 50 percent (52 percent), which shows that these sediments have undergone a long transportation and sedi mentation history. During recycling the percentage of unstrained grains increases. Blatt and Christie (1963) proposed a 15 percent initial volume of nonundulatory grains from either source, plutonic or metamorphic. It is assumed that both parent rocks contributed to the ortho quartzites discussed as well as the recycled sedimentary rocks. 108 CONCLUSIONS Three types of* primary sedimentary structures of* orthoquartzites from southeastern California did not re veal any significant quartz optic axis symmetry patterns which might indicate preferred orientation. Dimensional orientation seems to be present but is not possible to apply to these samples. The apparent elongation of quartz grains is most frequently (39 percent) observed parallel to the rhombohedral crystal face. Twenty-six percent of the grains have their apparent long axes parallel to the c axes, and 12,5 percent of the grains show an angular dispersion of 90°. The amount of angular separation is a function of source and abrasion history. 109 REFERENCES 110 REFERENCES Allen, J. R. L. , 1963, Internal sedimentary structures of well washed sands and sandstones in relation to flow conditions: Nature, v. 200, p. 326-327* Arbogast, J. L. , i960, An instrument for measurement of grain orientation by the dielectric anisotropic method: Exxon Production Research Corp., Report 258, Houston, Texas, 11 p. Blatt, H. and Christie, J. M., 1963, Undulatory extinction in quartz of igneous and metamorphic rocks and its significance of provenance studies of sedimentary rocks: Jour. Sed. Petrology, v. 33* no. 3> P* 559- 579* Blatt, H., Middleton, G. V. and Murray, R. C., 1972, Origin of sedimentary rocks: Prentice-Hall, New Jersey, 634 p. Burchfiel, B. C. and Davis, G. A., 1971> Clark Mountain thrust complex in the Cordillera of southeastern California; Field Trip Guide, Univ. California Riverside, 28 p. (Geol. Soc. Am. Cordilleran Section Meeting). Curray, J. R., 1956, Dimensional grain orientation studies of recent coastal sands: Am. Assoc. Petroleum Geologists Bull., v. 40, p. 2440-2456. Dana, E. S., 1966, Textbook of Mineralogy: ¥iley & Sons, New York, 4th edition, 851 p. Dapples, E. C. and Rominger, J. F., 1945* Orientation analysis of fine-grained clastic sediments: Jour. Geology, v. 53> P* 246-261. Dixon, ¥. J. (ed.), 1967, BMD Biomedical computer programs: University of California Press, Berkeley and Los Angeles, 600 p. Ill Fairbridge, R. ¥. , 1954, Stratigraphic correlation by microfacies: Am. Jour. Sci., v. 252, p. 683-694. Griffiths, J. C. and Rosenfeld, M. A., 1953, A further test of dimensional orientation of quartz grains in Bradford sand: Am. Jour. Sci., v. 251, p. 192-214. Gryaznova, T. E., 1949, Orientation of sand grains, methods of studying it and utilizing it in geology: Leningrad University Herald, Student's Scientific Papers No, 2, p. 97-105 (Russian), Haff, J. C., 1938, Preparation of petrofabric diagrams: Am. Mineralogist Jour., v. 23, p. 543-574. Hills, E. S., 1967, Elements of structural geology: John Wiley & Sons, New York, 483 p. Xngerson, E . and Ramisch, J, L., 1942, Origin of shapes of quartz grains: Am. Mineralogist Jour., v. 27, P. 595- 606. Kendall, M. G., 1948, The advanced theory of statistics: C. Griffin & Co., London, 503 P* Kerr, P. K,, 1959, Optical Mineralogy: McGraw-Hill, New York, 442 p. Knopf, E , B., 1933, Petrotectonics: Am. Jour. Sci., v. 25, p. 432-470. Krynine, P. D. f 1940, Petrology and genesis of* the third Bradford sand: Pennsylvania State College Bull. 29, p. 13-20. Lene, G. ¥. and Owen, D. E . , 1969, Grain orientation in a Berea Sandstone channel at South Amherst, Ohio: Jour. Sed. Petrology, v. 39, p. 737-743. Lobo, C. F., 1972, Petrography and statistical analysis of the Tapeats Sandstone (Late PreCambrian), Southern California: Unpubl. M.S. thesis, Univ. of Southern Calif., Los Angeles, 112 p. _______, 1974, Petrology and depositional history of Late PreCambrian-Cambrian quartzites in the eastern Mojave Desert, southeastern California: Unpubl. Ph.D. dis sertation, Univ. of Southern Calif., Los Angeles, 198 p. 112 Martini, I« P., 1971* A test of validity of quartz grain orientation as a paleocurrent and paleoenvironmental indicator: Jour. Sed. Petrology, v. 4l, p. 60-68. McKee, E. D. and ¥eir, G. ¥. , 1953* Terminology for strati fication and cross-stratification in sedimentary rocks: Geol. Soc. America Bull., v. 64, p. 381-390* Nanz, R. H., 1955* Grain orientation in beach sands: a possible means for predicting reservoir trend: Jour. Sed. Petrology, v. 25 (Abs.), p. 130. Pettijohn, F. J., Potter, P. E . , and Siever, R., 1973* Sand and sandstone: Springer-Verlag, New York, p. 6l8. Rowland, R, A., 1946, Grain shape fabrics of clastic quartz: Geol. Soc. America Bull., v. 59* P* 547-564. Rusnak, G. A., 1957* Orientation of sand grains under conditions of unidirectional fluid flow. Theory and experiment: Jour. Geology, v. 65, p* 384-409* • * Sander, B., 1930, Gefugekunde der Gesteine: Springer, Vienna, 352 p. , 1951* Contributions to the study of depositional fabrics: Am. Assoc. Petroleum Geologists, Tulsa, Oklahoma. Shelton, J. ¥. and Mack, D. E . , 1970, Grain orientation in determination of paleocurrent and sandstone trends: Am. Assoc. Petroleum Geologists Bull., v. 54, no. 7* p. 1108-1119. Stewart, J* H., 1970, Upper Precambrian and Lower Cambrian strata in the southern Great Basin, California and Nevada: U. S. Geol. Survey Prof. Paper 620, 206 p. Thompson, ¥. 0., 1937* Original structures of beaches, bars and dunes: Geol. Soc. America Bull., v, 48, p. 723-752. Turner, F. J. and Verhoogen, J., i960, Igneous and meta- morphic petrology: McGraw-Hill, New York, 694 p. Turner, F. J. and ¥eiss, L. F., 1963, Structural analysis of metamorphic tectonites: McGraw-Hill, New York, ^31 p. 113 Wayland, R« G., 1939» Optical orientation in elongate clastic quartz: Am. Jour. Sci., v. 237, p. 99-109* Ziramerle, ¥. and Bonham, L. C., 1962, Rapid methods for grain orientation measurements: Jour. Sed. Petrology, V . 32, p. 751-763. 11U

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Creator Zrupko, Maria Mann (author)

Core Title Petrofabric analysis of late Precambrian-Cambrian quartzites from southeastern California

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