DEPOSITIONAL AND DIAGENETIC HISTORY
OF THE LATE TRLASSIC DOCKUM GROUP,
YOUNG RANCH, NOLAN COUNTY, TEXAS
by
JASON P. SLAYDEN, B.S.
A THESIS
IN
GEOSCIENCE
Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE ACKNOWLEDGEMENTS
I would like to extend a huge "thank you" to Dr. George Asquith for serving as my committee chairman. His tremendous enthusiasm and excitement for "getting out in the field" made this project seem less like work, and more like having a good time while learning something new. I will forever be indebted to Dr. Asquith for the experiences he provided me.
I would also like to extend thanks to Dr. Tom Lehman and Dr. James
Barrick for serving on my committee. Thanks are also extended to Mike
Gower for making all of my slides, and to Lenny Wood and Anthony
Gonnell for their assistance in my field work. I would like to thank the
Texas Tech University Graduate School, Mewbourne Oil Company,
Texaco Exploration and Production, the Independent Petroleum
Association of America, and the Texas Tech Geology Department for providing financial support for this project. Thank you to the Young family for allowing me on their ranch which made this project possible.
Finally, I would like to thank hA/o people that deserve a lot of credit for the completion of this project, my wife, Angle, and daughter, Alyssa.
Angle was very supportive and understanding of all the time this project required of me. Alyssa shared my opinion that rocks are pretty. TABLE OF CONTENTS
ACKNOWLEDGEMENTS ii
ABSTRACT vi
TABLES viii
FIGURES ix
I. INTRODUCTION 1
Study Locality 1
Objectives and Methods of Study 1
Previous Work 3
II. TRIASSIC STRATIGRAPHY OF THE YOUNG RANCH 9
III. PETROGRAPHY 16
Section Tr-1 17
Section Tr-2 19
Section Tr-3 20
Section Tr-4 22
Section Tr-5 23
Santa Rosa versus Trujillo 25
IV. PALEOCURRENT ANALYSIS 33
III Section Tr-1 34
Section Tr-2 34
Section Tr-4 36
Section Tr-5 36
V. LITHOFACIES 41
Santa Rosa Formation 41
Trujillo Formation 47
VI. DEPOSITIONAL MODELS 49
General 49
Dockum Depositional Model 59
Santa Rosa Depositional History 61
Trujillo Depositional History 69
VII. DIAGENETIC HISTORY 77
Kaolinite 83
Iron Oxide 84
Zoned Dolomite 84
Quartz Overgrowths and Microcrystalline Quartz 86
Poikilitopic Calcite/Dedolomite Cement and Grain Replacement 87
Gypsum 89
iv VIII. SUMMARY 90
REFERENCES CITED 95
Appendix
A. MEASURED STRATIGRAPHIC SECTIONS 103
B. POINT COUNT DATA AND CLASSIFICATION 113
C. TERNARY DIAGRAMS 123
D. PALEOCURRENT DATA 129 ABSTRACT
The Late Triassic Dockum Group is a series of continental sediments comprised of lacustrine, deltaic, and fluvial deposits. Dockum sediments are found in Eastern New Mexico, Colorado, and West Texas,
Oklahoma, and Kansas. The Santa Rosa and Trujillo Formations represent the Dockum Group on the Young Ranch, Nolan County, Texas.
Santa Rosa and Trujillo Formations are fluvial deposits consisting of alternating layers of sandstone and conglomerate. These formations are found on the same topographic level on the ranch. Identification of the
Santa Rosa and Trujillo formations can be made through petrographic and paleocurrent analysis. The Santa Rosa Formation tends to be more quartzose and arkosic, while the younger Trujillo Formation is more lithic, with an abundance of metamorphic rock fragments and rare volcanic rock fragments. The Santa Rosa Formation has a reported sediment provenance in the present day Wichita-Arbuckle Mountains. Santa Rosa paleocurrent direction on the Young Ranch trend toward the south. The
Trujillo Formation has a reported provenance in the lower Ouachita
Tectonic Belt. Trujillo paleocurrent directions on the Young Ranch trend toward the north. Therefore, the paleocurrent analysis on the Young
VI Ranch supports the reported Santa Rosa and Trujillo sediment provenances.
Lithofacies types and vertical sequences along with a muitistoried channel stacking architecture indicate a braided fluvial system for the deposition of the Santa Rosa Formation. The presence of the Trujillo
Formation at the same topographic level on the ranch leads to the conclusion of deposition in two incised valleys.
Diagenetie history of the Dockum Group is marked by a variety of cementation events. Kaolinite and iron oxide occurred as eariy, shallow burial cementation. Zoned dolomite cement was emplaced during burial.
Quartz overgrowths and microcrystalline quartz cement formed during
Early Cretaceous Edwards exposure due to pedogenic silerete formation in the overiying Lower Cretaceous Antlers Sandstone.
Dedolomite/Poikilitopic calcite formed because of dissolution of the
Kirsehberg Evaporite during Early Cretaceous Edwards exposure.
Desiccation of recent freshwater springs precipitated gypsum as the final diagenetie event
VII TABLES
3.1 Petrographic differences in the Santa Rosa and Trujillo Formations 32
5.1 Lithofacies and sedimentary structures of fluvial deposits 42
6.1 Characteristics of braided, anastomosed, and meandering stream deposits compared to characteristics of the Triassic Dockum Group on the Young Ranch 62
B.1 Point count data from samples on the Young Ranch 113
B.2 Classification of samples 119
D.1 Paleocurrent calculations for section Tr-1 129
D.2 Paleocurrent calculations for section Tr-2 132
D.3 Paleocurrent calculations for section Tr-4 134
D.4 Paleocurrent calculations for section Tr-5 137
Vlll FIGURES
1.1 Locationofthe Young Ranch, Nolan County, Texas 2
1.2 Comparison of the stratigraphie nomenclature proposed by various authors for the Dockum Group in Eastern New Mexico 5
1.3 Comparison of the stratigraphie nomenclature proposed by various authors for the Dockum Group in west Texas 6
1.4 Location of Dockum Basin and prominent structures influencing deposition 8
2.1 Extent of Triassic Dockum Group outcrops 10
2.2 Map illustrating paleogeography of North America with respect to paleoequator during the Late Triassic Period 11
2.3 Cross section of the Young Ranch illustrating measured stratigraphie sections correlated based on proximity to the Permian Quartermaster Formation 12
2.4 Topographic map of Young Ranch illustrating cross section
line of section 13
2.5 Outcrop photos of Triassic rocks on the Young Ranch 15
3.1 Folk classification diagram comparing Santa Rosa Formation to the Trujillo Formation 27 3.2 Folk classification diagram comparing Santa Rosa Formation
to the Trujillo Formation with conglomerates removed 27
3.3 Photomicrographs of Triassic sandstones 28
3.4 Photomicrographs of Triassic conglomerates 30
3.5 Photomicrograph of common grains of Triassic Rocks 31
IX 4.1 Paleocurrent rose diagrams for Triassic rocks 35
4.2 Paleocurrent rose diagrams illustrating the composite directions of the both the Santa Rosa and Trujillo Formations. 38
4.3 Topographic map of the Young Ranch illustrating paleocurrent rose diagrams with location of measured section where readings were obtained 39
4.4 Cross section of the Young Ranch illustrating formation names as determined by petrographic and paleocurrent analysis 40
5.1 Outcrop photographs of individual lithofacies 44
5.2 Outcrop photographs of individual lithofacies 46
6.1 Fluvial stream models compared to model from Young Ranch 50
6.2 Illustration of multi-storied channel stacking architecture found
in the Santa Rosa Formation 64
6.3 Outcrop photograph of a single channel in the Santa Rosa... 64
6.4 Photomicrograph of caliche layer in section Tr-2 67 6.5 Photomicrographs of radiolarian ghosts in chert grains of the Santa Rosa Formation 67
6.6 Illustration of fluvial systems that incised the Santa Rosa Formation and deposited the Trujillo Formation 72
6.7 Photomicrograph of caliche layer in section Tr-5 72
6.8 Photomicrographs of radiolarian ghosts in chert grains of the Trujillo Formation 76
7.1 Paragenetic sequence of cementation events shown in relative order versus time since deposition 78 7.2 Photomicrographs of individual cementing minerals 79
7.3 Photomicrographs of quartz overgrowths and microcrystalline quartz cement 81
7.4.A Photomicrographs of individual cementing minerals 82
A.1 Legend of Lithology symbols used in stratigraphie sections.. 103
A.2 Measured section Tr-1A 104
A.3 Measured section Tr-1 B 105
A.4 Measured section Tr-1 C 106
A.5 Measured section Tr-1 D 107
A.6 Measured section Tr-2 108
A.7 Measured section Tr-3 109
A.8 Measured seetionTr-4 110
A.9 Measured section Tr-5 111
A.10 Measured section Tr-6 112
C.I Ternary diagram of classification for section Tr-1 A 123
C.2 Ternary diagram of classification for section Tr-1 B 124
C.3 Ternary diagram of classification for section Tr-2 125
C.4 Ternary diagram of classification for section Tr-3 126
0.5 Ternary diagram of classification for section Tr-4 127
C.6 Ternary diagram of classification for section Tr-5 128
D.I Paleocurrent rose diagram for section Tr-1 131
XI D.2 Paleocurrent rose diagram for section Tr-2 133
D.3 Paleocurrent rose diagram for section Tr-3 136
D.4 Paleocurrent rose diagram for section Tr-4 139
XII CHAPTER I
INTRODUCTION
Study Locality
The location of this study area is the Young Ranch, Nolan County,
Texas (Figure 1.1). The Young Ranch is located five miles south of the town of Roseoe, Texas on State Highway 608. The Dockum sediments found in Nolan County represent the easternmost extent of the present day
Dockum Group. The Santa Rosa Formation and the Trujillo Formation are the only members of the Dockum Group found in this area due to erosional truncation.
Obiectives and Methods of Study
The primary objective of this study is to describe the depositional and diagenetie history of the Late Triassic Dockum group that is present on the Young Ranch, Nolan County, Texas. Depositional history was determined based on comparisons of vertical assemblages of lithofacies, paleocurrent data, and petrographic analysis to modern fluvial depositional systems. The sedimentary structures and fades relationships are described for both the Santa Rosa and Trujillo Formations. A petrographic analysis of these formations was performed, and mineralogieal differences
1 Nolan County
Figure 1.1. Map illustrating the location of the Young Ranch five miles south of the town of Roseoe in Nolan County, Texas. noted. Mineralogy, paleocurrent trends, and reference to paleogeography were used to determine sediment provenance, or source area.
Stratigraphie sections were measured using a brunton compass and a
Jacob staff. Because of the extreme variability in sediments, sections have been correlated using topographic level (maps and GPS), and proximity to
Permian Quartermaster Formation as reference points. Scaled outcrop drawings were made to show lateral relationships and variability of sediments. Paleocurrent measurements were made using a brunton compass along bedding surfaces to determine paleocurrent trends.
Diagenetie sequences are determined by petrographic analysis.
Previous Work
W. F. Cummins first studied the Triassic sediments of west Texas in 1889. Cummins (1889) named the Triassic sediments the "Dockum
Beds" in the First Annual Report of the Geological Society of Texas. The beds were named for the outcrops near Dockum Creek outside the former town of Dockum in Dickens County, Texas. Cummins (1890) proposed that these sediments were deposited in a freshwater, continental basin.
The following year, N. F. Drake (1891) correlated the Dockum beds along the eastern Caprock Escarpment and subdivided the beds into three mappable horizons: a lower sandy clay unit, a middle sandstone and conglomeratic unit, and an upper sandy clay unit E. D. Cope (1891) later
studied the vertebrate remains in the Dockum beds and confirmed
Cummins' statement that the Dockum beds were deposited in a continental
setting (Green, 1954). Gould (1907) first elevated the Dockum beds to
group status. He named Drake's lower sandy clay unit the Tecovas
Formation, and the middle and upper units were named the Trujillo
Formation. Darton (1922) first described and named the basal sand unit of
the Dockum Group as the Santa Rosa Sandstone, so named for the
proximity of outcrops in the Pecos River valley to the town of Santa Rosa,
New Mexico (Bunting, 1994). Adams (1929) correlated the Santa Rosa
sandstone to the basal sand unit along the southern and eastern margins
of the Dockum Group in Texas (Adams, 1929; Gawloski, 1983).
There has been much debate over the accepted nomenclature of the
Dockum Group since its original naming. Changes have been accepted
over the years. Recently, however, workers from New Mexico studying the
Dockum Group have accepted a nomenclature for the entire extent of the
Dockum Group that differs from workers in Texas studying the Dockum
group. Changes in nomenclature through time are noted on the tables on the following pages (Figures 1.2 and 1.3).
Workers studying the Dockum Group are in agreement that the depositional environment of the Dockum was a combination of lacustrine, 1920s 1940s 1970s 1985 1989 1993
1 1 n 10 w -o o « SE CO > •DU. •ouS.E. SB T3U. O I-gus. Q: o: Ii K i o e O C i lio n ny o co-S 0}.^ lio n t-E L. E OE S 9 0 rm a &5 c S5 to"" u.
li o 3 3 0 cs 2 0 c < 1 o5 c 0.9 0
S 2E C h Cuerv o
's'i Pe d Membe r Cuerv o . S
Membe r t-o Chinl e Fonn a u. u. c
Chinl e Formatio n a Chinl e Fonnatio n
Docku m Grou p m Docku m Grou p «
ocku m Grou p undivWe d .S 0 c Q £ 9 j 03.0 wE wE o« So oE Membe r O "S 0 Lowe r Sh a .i3i 0 o o c c upss n^ T.L. Mbr T.L Mbr
missmbr oc Tec. Mbr Ros a F m Tec. Mbr eoK c CQK c ID
0) CO CD Fotmal i Sant a R Issmbr Anton Chico Fm Moenkopi Fm / ^C.Mbf
Figure 1.2. Comparison of the stratigraphie nomenclature proposed by various authors for the Triassic Dockum Group in Eastern New Mexico (Lehman, 1994). Nomenclature Used in this Study 1993 1990 1986 1920S-70S 1900s 1890s
r^ Redonda 1 Fm. c ! S c £1 =o c ».9 o SS i U a c « >. 2E Q. I O C a OS Q.O U o5 OS P 8"- qu i «> = u. o O ffi C E (B ^ Trujillo o 5l o. jiil o m SS O3
Dock u 2>^ Trujill o
Memb e o t- amed m tl t-s O
l e Grou p u. m Forma l c t- F E n = 3 JC 3 u be r va s Do c ov a mb e Dock u a ^£
aS, s «• S «05 E =.Q E.C.O m ooj III 05 Oi «3^' Bjo: Anton CJnco Fm | 31^
Figure 1.3. Comparison of the stratigraphie nomenclature proposed by various authors for the Triassic Dockum Group in west Texas, and noting the accepted nomenclature for this project (Lehman, 1994). fluvial, and deltaic systems. Sediment provenance, however, has been a source of disagreement over the years. Baker (1915) proposed that the coarse sandstones and conglomerates originated from the ancestral Rocky
Mountains and/or from the Wichita-Arbuckle Mountains in Oklahoma
(Gawloski, 1983). Roth (1943) conducted petrographic analysis on siliceous pebbles from the eastern margins of the Dockum to determine sediment provenance. Apparent sediment provenance was predominately from the Glass Mountains, Marathon Uplift, Llano Uplift, Ouachita Tectonic belt, and the Wichita-Arbuckle Mountains (Roth, 1943). Later studies have suggested a peripheral filling of the basin from all directions: Amarillo,
Llano, Marathon, and Sangre de Cristo Uplifts, the Sierra Grande Arch, and the Ouachita Tectonic Belt (McGowen et al., 1979). This depositional model appears to be correct for the younger sediments of the Dockum
Group. However, dating of detrital zircons in the Santa Rosa Formation has shown that a through-going river system flowing west to the
Cordilleran Sea was the earliest mode of deposition for the Dockum Group
(Figure 1.4) (Lehman etal., 1996; Dottand Batten, 1988). __-.^—-_—j < r 7 A Amarillo P Phoenix Ankareli\ Ij*, ', 'Popo'^gie D Denver SLC Salt Lake City / rAu'id"U/)g"-75?---f--^™-"^r' EP El Paso "^ Chinle Formation Hermositlo r' f^_j-.^ and equivalents • Paleocurrent ' trend 4i\t Fluvi^ sediment H^ dispersal path Ar^ '// Late Triassic '' -'' highlands Cambrian plu- ; Ijasement
/(//J" P ^-- WCD0<^1^' ' ( DO(!^Unr^ - ^, -lAmarillo--- 11 Amamio-yAmaraio-WichitV v a iT,^o„n,o«X/X^ . i o..Pedema^f'jVxSFOiipK- .'^ \'r<,V.i,«»C x ,'' 7/ UDlif"P««l '' Uplift V) ^v ' .':. V - >
x'Mogolton *;-\4!v// 'uplands"
Kilometers
Figure 1.4. Location of Dockum Basin and prominent structures influencing deposition (Riggs et al., 1996)
8 CHAPTER II
TRIASSIC STRATIGRAPHY OF THE
YOUNG RANCH
The Dockum Group includes all Triassic sediments spanning from
Eastern New Mexico and Colorado to Western Kansas, Oklahoma, and
Texas (Figure 2.1). These sediments were deposited in fluvial, deltaic, and lacustrine depositional environments during the Late Triassic Epoch
(McGowen et al., 1983). The Dockum Basin was located approximately 5-
10° north of the paleoequator (Figure 2.2). The maximum thickness of the
Dockum Group is approximately 2000 feet in the center of the basin
(Johns, 1989).
On the Young Ranch, the Dockum Group rests unconformably on the Permian Quartermaster Formation, and overlain unconformably by the
Lower Cretaceous Antlers Sandstone (Figure 2.3). The Permian
Quartermaster Formation is a reddish siltstone with light gray mottled texture, and contorted horizontal stratification. The Permian sediments were deposited in arid hypersaline water bodies, and tidal flats (McGowen, et al., 1979). The Antlers Sandstone is part of the Lower Cretaceous
Trinity Group. The Antlers Sandstone was deposited in fluvial and shallow marine environments. The Antlers is represented by friable quartzarenites
9 Figure 2.1. Shaded area represents extent of Triassic Dockum Group in outcrop and subsurface (modified from McGowen et al., 1979).
10 Figure 2 2. Map Hlustrafing paleogeography of North Amenca with respect To the equator during the Late Triassic Period. Red dot represents the present location of the Young Ranch (Dott and Batten, 1988).
11 ^
12 1 mile
Figure 2.4. Topographic map of the Young Ranch showing the locations of measured sections on the ranch. Black lines l>etween locations represents line 13 and completely silieified quartzarenites or pedogenic silcretes (Wood, 2001). The Santa Rosa Formation is composed of alternating sand and conglomeratic layers. The sand units are pooriy indurated, yellowish- brown, medium- to very fine-grained sublitharenites (Figure 2.5.A). The conglomeratic layers are moderately indurated, yellowish-brown to brown chert pebble or granule conglomerates. The conglomerates are predominately elast supported (Figure 2.5.B). The Trujillo Formation is composed of pooriy indurated, yellowish- brown, micaceous litharenite, sublitharenite, and quartzarenite sandstones (Figure 2.5.C). Conglomerates are typically moderately indurated, brownish chert pebble or granule conglomerate. The conglomerates of the Trujillo Formation are matrix supported (Figure 2.5.D). Sand units in both the Santa Rosa and Trujillo have planar and trough cross bedding structures. Conglomerates of the Santa Rosa Formation are typically massive or contain faint horizontal stratification. Some of the conglomerates of the Trujillo Formation have trough and planar erossbeds. However, they predominately contain graded and inversely graded bedding (see Chapter V). 14 Figure 2.5. Outcrop photos from Young Ranch. (A) Typical appearance of Santa Rosa sandstone in outcrop. (B) Typical appearance of Santa Rosa conglomerate in outcrop. (C) Typical appearance of Tnjjillo sandstone in outcrop. (D) Typical appearance of Tmjillo conglomerate in outcrop. 15 CHAPTER III PETROGRAPHY Samples were collected from six outcrops where stratigraphie sections were measured. A total of 62 samples were thin sectioned for petrographic analysis: nine from section Tr-1 A, nine from section Tr-1 B, fourteen from section Tr-2, seven from section Tr-3, thiri:een from section Tr-4, and ten from section Tr-5. Some slides were stained with Alizarin Red-S to indicate calcite or dolomite. Slides were impregnated with blue epoxy to illustrate porosity. The thin sections were counted using Folk's (1968) point counting scheme of three constituent grain types: quartz, feldspar (plagioelase and potassium feldspars), and lithic fragments (all non-quartz or feldspar grains, and accessory minerals). Specific accessory and cementing minerals, as well as, grain size were also counted. A total of 500 points were counted per slide, which has a maximum 4.5% error (Van der Plas and Tobi, 1965). All samples have been classified using Folk's (1968) classification scheme. Grainsize was determined by petrographic analysis. It should be noted that grainsize analysis from thin sections is typically lower than correct values. The thin sections would have to be cut through the intermediate axis of every grain for a correct value. 16 These thin sections include samples from both the Santa Rosa and Trujillo Formations. These formations are found on the same topographic level in this study area (Figure 2.3). As a result, identification and separation of the Santa Rosa and Trujillo Formations petrographieally is the primary purpose of this analysis. Section Tr-1 This section includes samples from Tr-1 A and IB (Figure 2.3). These sections are composed of alternating beds of conglomerate and sandstone. The predominant grains in these sediments are quartz, feldspar, chert, metamorphic rock fragments, and accessory minerals. These rocks are classified as sublitharenites, chertarenites, and sedarenites (Appendix B). Samples in section Tr-1 contain approximately 59% quartz. The quartz grains are predominantly monocrystalline quartz grains with an equal proportion of straight and undulose extinction. Polycrystalline quartz grains (> 2 crystals per grain) with undulose extinction are also found within these rocks. Approximately 3% of the grains are feldspars, with the predominate feldspar type as potassium feldspar (mieroeline) and some minor plagioelase. Lithic fragments make up the remaining 38% of the grains in this section. Lithic fragments are comprised of chert, 17 metamorphic, and sedimentary rock fragments with some minor accessory minerals (biotite, muscovite, and zircons) (Appendix B). The mean grainsize for the sandstone samples is approximately 0.125-0.25 mm (fine sand). The grains are well sorted and typically subrounded to subangular. The overall texture of all sandstones in this section is mature. Conglomerates have a mean grainsize between 4-64 mm (pebble). The conglomerates are pooriy sorted with rounded to subangular grains. The overall texture of the conglomerates is submature (Appendix B). The cementing minerals in the sandstones are kaolinite, iron-oxide, and poikilitopic calcite. Kaolinite and iron-oxide are the most common cement types. The sandstones are very pooriy cemented, with the exception of the samples cemented by poikilitopic calcite (Tr-1A-2B and 1A-3C). Primary intergranular porosity is well preserved. The conglomerates are cemented with dolomite/dedolomite, calcite, iron oxide, and gypsum. The most common cementing minerals in the conglomerates are calcite and iron-oxide. Gypsum is found in samples Tr-1B-1 and 1B-6, and dolomite/dedolomite is found in sample Tr-1A-1 A. Porosity is not well preserved in conglomerates (Appendix B). 18 SECTION Tr-2 This section is primarily composed of sandstone with one conglomerate layer at the base of the section (section Tr-2-1 in Appendix). The predominant grains in these sediments are quartz, sedimentary and metamorphic rock fragments, chert, accessory minerals and feldspars. These rocks are classified as sublitharenites, with one sedarenite, one subarkose, and one caliche in sample Tr-2-6b (Appendix B). Samples in section Tr-2 contain approximately 74% quartz. The quartz grains are predominantly monocrystalline quartz grains with undulose extinction. Polycrystalline quartz grains (> 2 crystals per grain) with undulose extinction and monocrystalline quartz grains with straight extinction are also found within these rocks in relatively equal proportions. Approximately 6% of the grains are feldspars with potassium feldspar (mieroeline) and plagioelase in equal proportions. Lithic fragments make up the remaining 20% of the grains in this section. Lithic fragments are comprised of metamorphic rock fragments, chert, and minor sedimentary rock fragments and accessory minerals (biotite, muscovite, zircon, and minor chlorite) (Appendix B). The mean grainsize for the sandstone samples is approximately 0.0625-0.125 mm (very fine sand). The grains are very well sorted and typically rounded to subrounded. The overall texture of all sandstones in 19 this section is supermature. The conglomerate sample has a mean grainsize between 4-64 mm (pebble). The conglomerate is pooriy sorted with rounded to subangular grains. The overall texture of the conglomerate is submature (Appendix B). The cementing minerals in the sandstones are kaolinite, iron-oxide, poikilitopic calcite, and dolomite/dedolomite. The cementation of the sandstones is evenly distributed with equivalent amounts of kaolinite, iron oxide, calcite, and dolomite/dedolomite. The sandstones are very poorly cemented, with the exception of the samples cemented by poikilitopic calcite (Tr-2-4, 2-7, and 2-8a). Primary intergranular porosity is well preserved. The conglomerate is cemented with dolomite/dedolomitized calcite. Porosity is not well preserved in the conglomerate sample (Appendix B). Section Tr-3 This section (Figure 2.3) is comprised of alternating layers of conglomerate and sandstone. The predominant grains in these sediments are quartz, chert, metamorphic rock fragments, feldspar, and accessory minerals. These rocks are classified as sublitharenites, chertarenite, and one quartzarenite (Appendix B). 20 Samples in section Tr-3 (Figure 2.3) contain approximately 67% quartz. The quartz grains are predominantly monocrystalline quartz grains with undulose extinction. Polycrystalline quartz grains (> 2 crystals per grain) with undulose extinction and monocrystalline quartz grains with straight extinction are also found within these rocks in relatively equal proportions. Approximately 2% of the grains are potassium feldspar (mieroeline). Lithic fragments make up the remaining 31 % of the grains in this section. Lithic fragments are comprised of chert, minor metamorphic rock fragments, and accessory minerals (muscovite, and zircon) (Appendix B). The mean grainsize for the sandstone samples is approximately 0.125-0.5 mm (fine to medium sand). The grains are moderately sorted and typically rounded to subrounded. The overall texture of all sandstones in this section is mature. The conglomerate samples have a mean grainsize between 4-64 mm (pebble). The conglomerates are pooriy sorted with rounded to subangular grains. The overall texture of the conglomerates is submature (Appendix B). The cementing minerals in the sandstones are kaolinite, iron-oxide, and poikilitopic calcite. The cementation of the sandstones is predominantly kaolinite with minor iron-oxide and calcite. The sandstones are very pooriy cemented, with the exception of the sample cemented by 21 poikilitopic calcite (Tr-3-3). Primary intergranular porosity is well preserved. The conglomerates are cemented with quartz overgrowths and calcite. Quartz overgrowths are found in samples Tr-3-6a and 3-6b at the top of the section. Porosity is not well preserved in conglomerates (Appendix B). Section Tr-4 This section (Figure 2.3) is primarily composed of sandstone with two sandy conglomerate layers. The predominant grains in these sediments are quartz, chert, metamorphic and sedimentary rock fragments, minor feldspar, and accessory minerals. These rocks are classified as sublitharenites (Appendix B). Samples in section Tr-4 contain approximately 79% quartz. The quartz grains are predominantly monocrystalline quartz grains with undulose extinction. Polycrystalline quartz grains (> 2 crystals per grain) with undulose extinction and monocrystalline quartz grains with straight extinction are also found within these rocks in relatively equal proportions. Approximately 1% of the grains are potassium feldspar (mieroeline). Lithic fragments make up the remaining 20% of the grains in this section. Lithic fragments are predominantly comprised of chert, minor metamorphic and sedimentary rock fragments, and accessory minerals (biotite, muscovite, chalcedony, and garnet) (Appendix B). 22 The mean grainsize for the sandstone samples is approximately 0.25-0.5 mm (medium sand). The grains are well sorted and typically rounded to subrounded. The overall texture of all sandstones in this section is supermature. The conglomerate samples have a mean grainsize between 4-64 mm (pebble). The conglomerates are pooriy sorted with rounded to subangular grains. The overall texture of the conglomerates is submature (Appendix B). The cementing mineral in the sandstones is kaolinite. Pebbly and granule sandstones have dolomite/dedolomite cement (samples Tr-4-1, 4- 4, 4-4a, and 4-5). The pebbly and granule sandstones have little to no preserved porosity, while the "clean" sandstones are very pooriy cemented with primary intergranular porosity well preserved. The conglomerates are cemented with kaolinite in sample Tr-4-7 and calcite in sample Tr-4-9. Porosity is well-preserved in kaolinite cemented sample, while calcite cemented sample has very little preserved porosity (Appendix B). Section Tr-5 This section (Figure 2.3) is primarily composed of alternating layers of sandstone and conglomerate. The predominant grains in these sediments are quartz, chert, metamorphic rock fragments, minor feldspar, sedimentary rock fragments, and accessory minerals. These rocks are 23 classified as quartzarenites, sublitharenites, and chertarenites (Appendix B). Samples in section Tr-4 contain approximately 70% quartz. The quartz grains are predominantly polycrystalline quartz (> 2 crystals per grain) with undulose extinction. Monocrystalline quartz with undulose extinction and minor monocrystalline quartz grains with straight extinction are also found within these rocks. Approximately 2% of the grains are feldspar, with plagioelase being the predominant feldspar type. Lithic fragments make up the remaining 28% of the grains in this section. Lithic fragments are predominantly comprised of chert, metamorphic rock fragments, and minor sedimentary rock fragments, and accessory minerals (biotite, muscovite, hornblende, chalcedony, and garnet) (Appendix B). The mean grainsize for the sandstone samples is approximately 0.125-0.25 mm (fine sand). The grains are moderately sorted and typically subrounded to subangular. The overall texture of all sandstones in this section is mature. The conglomerate samples have a mean grainsize between 2—4 mm (granule). The conglomerates are pooriy sorted with rounded to subangular grains. The overall texture of the conglomerates is submature (Appendix B). The cementing mineral in the sandstones is kaolinite. All sandstones in this section are pooriy cemented, and primary intergranular 24 porosity is well preserved. The conglomerates are cemented with calcite. Conglomerates are well cemented, and porosity is non-existent (Appendix B). Santa Rosa Versus Trujillo Formation The Santa Rosa Formation can be separated from the Trujillo Formation through petrographic differences between the two formations. Previous work by Fritz (1991) and May (1988) classified the Santa Rosa as quartzarenite, sublitharenite, and subarkose using Folk's classification. The Trujillo Formation plots on Folk's classification diagram as quartzarenite, sublitharenite, and litharenite (May, 1988). Metamorphic and volcanic minerals and fragments dominate sediments of the Trujillo Formation (Long and Lehman, 1993). When the Santa Rosa and Trujillo Formations are plotted on a Folk Classification Diagram, they overiap each other with no separation (Figure 3.1). The predominantly chert-bearing conglomerates, result in the Santa Rosa and Trujillo sediments on the Young Ranch plotting more lithic (Figure 3.1). Figure 3.2 illustrates the Santa Rosa and Trujillo sediments plotted on Folk's diagram with the conglomerates removed. With conglomerates removed, Santa Rosa sediments plot on Folk diagrams as quartzarenite, sublitharenite, and subarkose. Trujillo sediments plot as 25 quartzarenite, sublitharenite, and litharenite. These differences in composition in the Santa Rosa and Trujillo Formations (Figure 3.2) have been previously noted by Fritz (1991) and May (1988). The sandstone units of both formations are very similar in outcrop being pooriy indurated, and pooriy cemented. Porosity is well preserved in the sandstones of both formations. Sandstones of the Santa Rosa Formation are composed of larger sand grains than the Trujillo Formation (Figure 3.3.A-D; table 3.1). Conglomerates of the Santa Rosa and Trujillo Formations are also similar in outcrop. Conglomerates are well indurated, supporting most of the Triassic topographic highs on the ranch. The conglomerates in the Santa Rosa and Trujillo are well cemented, and contain little to no preserved porosity. The conglomerates of the Santa Rosa tend to be elast supported, with little fine grained matrix, and Trujillo conglomerates are matrix supported (Figure 3.4.A-D). Santa Rosa sections Tr-1, 2, and 3 (Figure 2.3) are more arkosic (red data points) than the sediments in the Trujillo sections Tr-4, and 5 (Figures 2.3 and 3.2). Santa Rosa sections can also be differentiated from the Trujillo sections by the Santa Rosa's greater percentage of single crystal quartz grains (30%) with straight extinction (plutonic quartz) when compared to the Trujillo sections (14%) (Table 3.1). Dominant accessory minerals in the Santa Rosa are predominantly muscovite, biotite, and 26 Folk's Classification Santa Rosa vs. Trujillo Fms. Quartzarenite - Sublitharenite Santa Rosa Trujillo Fm. Feldspar Lithic Figure 3.1. Folk classification diagram comparing Santa Rosa Formation to Trujillo Formation. Folk's Classification Santa Rosa and Trujillo Fms. Conglomerates Removed Qtz ^Quartzarenite Sut)ar1 ' 1 \ J. \ • Santa Rosa Fm. Y\ \ \ % Trujillo Fm. / /Arkose j Lithic Feldspathic VjthareniteX Arkose Litharenite \ \ Feldspar Lithic Figure 3.2. Folk classification diagram comparing Santa Rosa Formation to Trujillo Formation with conglomerates removed. 27 Figure 3.3.A-D. Photomicrographs of typical Dockum sandstones. (A) Santa Rosa sandstone In plane light. (B) Sample A shown in polarized light. (C) Trujillo sandstone in plane light. (D) Sample C shown in polarized light. Field of view for all photos = 3.5 mm. 28 zircons (Figures 3.5.A-B). Polycrystalline (metamorphic) quartz grains are the dominant quartz type in sections Tr-4 and 5 (Appendix B). Trujillo sections Tr-4, and 5 contain a larger percentage of lithic fragments (25%) in relation to Santa Rosa sections Tr-1, 2, and 3 (16%) (Table 3.1). Lithic fragments in sections Tr-4, and 5 are predominantly metamorphic rock fragments (e.g., phyllite, quartz schist, and muscovite schist). Metamorphic and volcanic accessory minerals also dominate sections Tr-4 and 5 (e.g., muscovite, biotite, garnet, and hornblende) (Figure 3.5.C-D). Possible volcanic rock fragments are present in section Tr-4 (Figure 3.5.E- F). Using Folk's classification of sediments in this locality, with conglomerates removed, the sediments of the Santa Rosa and Trujillo agree with previous work done by Fritz (1991) and May (1988). Separation of the Santa Rosa and Trujillo Formaitions can be achieved by examination of rock fragments and accessory minerals in the sandstones of the Trujillo and Santa Rosa Formations. Sections Tr-1, 2, and 3 (Figure 2.3) represent sediments from the Santa Rosa Formation, and sections Tr- 4, and 5 (Figure 2.3) represent sediments from the Trujillo Formation. Using these methods and comparisons, a Triassic measured section on the ranch can now be determined to be either Santa Rosa or Trujillo based on petrographic analysis. 29 Figure 3.4.A-D. Photomicrographs of typical Dockum conglomerates. (A) Santa Rosa conglomerate in plane light. (B) Sample A shown in polarized light. (C) Trujillo conglomerate In plane light. (D) Sample C shown in polarized light Field of view for all photos = 3.5 mm. 30 Figure 3.5.A-D. Photomicrographs of typical Santa Rosa and Trujillo Formation accessory minerals and rock fragments. (A) Santa Rosa sandstone with feldspars and muscovite. (B) Santa Rosa sandstone with feldspar and zircon. (C) Trujillo sandstone with biotite, zircon, muscovite schist, and phyllite. (D) Trujillo sandstone with hornblende and garnet. (E) Trujillo sandstone with volcanic rock fragment In plane light. (F) Photo E In polarized light. Field of view = 3.5 mm. for A, B, D, E, and F. Field of view = 0.85 mm for C. 31 Table 3.1. Petrographic differences between the Santa Rosa and Trujillo Formations. Santa Rosa Formation Trujillo Formation Mean Grainsize 0.32 mm 0.25 mm Monocrystalline 29.80% 13.80% Straight Extinction Quartz Polycrystalline 18.10% 30.10% Undulose Extinction Quartz Total Feldspars 4.00% 1.60% Lithic Fragments 32.00% 23.60% in Sandstone and Conglomerate Lithic Fragments 16.10% 25.40% in Sandstones 32 CHAPTER IV PALEOCURRENT ANALYSIS A paleocurrent analysis was peri'ormed to determine direction of flow for the fluvial systems responsible for deposition of the Santa Rosa and Trujillo Formations. Paleocurrent measurements were taken from the areas where four stratigraphie sections were measured (Figure 2.3). The data taken from section Tr-1 included readings from sections 1A, 1B, and 1C. A total of 167 paleocurrent directions were taken. Trough erossbedding provides a reliable source for paleocurrent measurement, as troughs have been proven to provide accurate estimates of channel flow direction in modern environments (Wulf, 1962). However, planar erossbeds are frequently not reliable, and a large number of readings are necessary to provide an accurate estimate flow direction in the absence of trough erossbeds (High and Picard, 1974). Ninety-four percent of the readings were performed on trough cross-stratified sandstones. Five percent of the readings were taken from planar cross- stratified sandstones (section Tr-1), and a further one percent were taken from planar cross-stratified conglomerates (section Tr-4). The data was processed for statistical information using formulas for vector mean (Vmean), vector magnitude (R), and consistency ratio (L) 33 from Potter and Pettijohn (1963). Rose diagrams were plotted using GEOrient version 7.2 (Holcombe, 1999). Section Tr-1 Thirty-two paleocurrent measurements were taken in section Tr-1 (Figure 2.3). Twenty-three measurements were taken from trough cross- stratified rocks, and nine readings were obtained from planar cross- stratified rocks. The vector mean for this section is S10E (azimuth=170°) (Figure 4.1 .A). The vector magnitude is 38, and the consistency ratio is 93% (Appendix C). There is very little variance in the paleocurrent readings (circular standard deviation of 22°), which illustrates a unimodal distribution for this section (Appendix C). The consistency of the readings suggests that there were no significant changes in paleoslope or channel direction during deposition of these sediments in section Tr-1. Section Tr-2 Twenty-six paleocurrent measurements were taken in section Tr-2 (Figure 2.3). All twenty-six measurements were taken from trough cross- stratified sandstones. The vector mean for this section is S43W (azimuth=223°) (Figure 4.1 .B). The vector magnitude is 25, and the consistency ratio is 96% (Appendix C). There is very little variance in the 34 B 1^^ . lin, :pn, jf^ , in . ?n . :jifi, ^ 7\7 Figure 4.1 .A-D. Vector rose diagrams illustrating paleocurrent diretions in Triassic Dockum Group. (A) Vfector rose for section Tr-1, (B) Vector rose for section Tr-2, (C) Vector rose for section Tr-4, (D) Vector rose for section Tr-5. 35 paleocurrent readings (circular standard deviation of 16°), which illustrates a unimodal distribution for this section (Appendix C). The consistency of the readings suggests that there were no significant changes in paleoslope or channel direction during deposition of these sediments in section Tr-2. Section Tr-4 Fifty-three paleocurrent measurements were taken in section Tr-4 (Figure 2.3). All fifty-three measurements were taken from trough cross- stratified sandstones. The vector mean for this section is N16E (azimuth=16°) (Figure 4.1 .C). The vector magnitude is 47, and the consistency ratio is 90% (Appendix C). There is very little variance in the paleocurrent readings (circular standard deviation of 20°), which illustrates a unimodal distribution for this section (Appendix C). The consistency of the readings suggests that there were no significant changes in paleoslope or channel direction during deposition of these sediments in section Tr-4. Section Tr-5 Forty-seven paleocurrent measurements were taken in section Tr-5 (Figure 2.3). All forty-seven measurements were taken from trough cross- stratified sandstones. The vector mean for this section is N28W (azimuth=332°) (Figure 4.1 .D). The vector magnitude is 44, and the 36 consistency ratio is 94% (Appendix C). There is very little variance in the paleocurrent readings (circular standard deviation of 21°), which illustrates a unimodal distribution for this section (Appendix C). The consistency of the readings suggests that there were no significant changes in paleoslope or channel direction during deposition of these sediments in section Tr-5. The Santa Rosa Formation has a known source in the Wichita- Arbuckle Mountains (Riggs et al., 1996). The Trujillo Formation has a sediment source in the Lower Ouachita Tectonic Belt (Marathon Uplift) (Long and Lehman, 1993). Therefore, it is concluded that the sediments containing unidirectional flow structures that indicate southward paleoflow directions (sections Tr-1 and Tr-2) represent the Santa Rosa Formation (Figure 4.2). Those containing structures that indicate a northward flow direction (sections Tr-4 and Tr-5 represent the Trujillo Formation (Figure 4.2). Figure 4.3 shows the location of sections measured along with corresponding paleocurrent rose diagrams. Figure 4.4 illustrates the cross-sectional view of the Triassic deposits (Dockum; Figure 2.3) on the Young Ranch, which are now broken down into Santa Rosa and Trujillo Formations based on the petrographic and paleocurrent data gathered from measured stratigraphie sections. 37 Vector Mean=356' Circ. Variance=K).14 Circ. Std. Dev.=3r Max= 15.0% (15pts) N=100 B. Vector Mean=189° Circ. Variance=0.17 Circ. Std. Dev.saS" Max= 14.9% (1Dpts) N=67 Figure 4.2. Paleocurrent rose diagramsifiustrating paleoflow direction. (A) Paleocurrent rose dtagranr for the Trupofi^rrnatfon. (B) Paleocurrent rose diagram for the Santa Rosa Formation. 38 Section TR-4 SecttonTR-1 Section TR-5 Imile Figure 4.3. Topographic map of the Young Ranch showing paleocun^ent rose diagrams with corresponding stratigraphie section where measure- -ments were taken. Dashed lines indicate approximate boundary between Santa Rosa and Tnjjillo Formatk)ns. Sections Tr-1 and 2 are Santa Rosa and Sectior« Tr-4 and 5 are TrujIUo, 39 'i'i'i'i'ifi I'i'i'i'i'i' (C c c <0 4) O o o to 'i'l'ili o ^ l!l!i;i|i|!| TO Z l!l!i;l||'l^ C "* o O (D ^3 r- a>i> c «J >-^ © = li o T3 |ii! «0 «>« auoispues sjaijuvW°';ji sno»3«»aJ0i i°. i°. i°. I oto ^o I''' '1 '1 'I'i ill . CD 40 LL -D en CHAPTER V LITHOFACIES The Santa Rosa and the Trujillo Formations represent the Dockum Group in the study locality. These formations were deposited in a fluvial depositional system. Within these formations, however, are different sets of lithofacies that mark deposition in separate environments within the fluvial depositional system. Each of these lithofacies has been recognized in outcrops within the Young Ranch. The relative position, sequence of, and types of lithofacies can be used together to interpret the depositional environment of the formations. Vertical relationships of lithofacies can be observed in the measured stratigraphie sections (Appendix A). The following is a description of the lithofacies found on the Young Ranch, in the Santa Rosa and Trujillo Formations. Santa Rosa Formation Lithofacies The Santa Rosa Sandstone in this locality is represented by six individual lithofacies. Each lithofacies represents a separate depositional environment within the depositional system of the area, and is noted by an abbreviation according to Miall's (1981) Table of fluvial lithofacies (Table 5.1). The lithofacies present are: (1) massive to horizontally stratified 41 Table 5.1. Lithofacies and sedimentary structures of fluvial deposits (Miall, 1981). Fades Code Lithofacies Sedimentary Structures laterpretation Gms massive, matrix none debris flowdeposit s supported gravel Gm massive or crudely horizontal bedding longitudinal bars bedded gravel imbrication of gravel lag deposits sieve deposits Gt gravel, stratified trough erossbeds minor channel fills Gp gravel, stratified planar erossbeds linguoid bars or deltaic growths from older bar remnants St sand, medium to solitary (theta) or grouped V. coarse, may be (pi) trough erossbeds dunes (lower flow pebbly regime) Sp sand, medium to solitary (alpha) or grouped linguoid, ttansverse V. coarse, may be (omikron) planar erossbeds bars, sand waves pebbly (lower flow regime) Sr sand, very finet o ripple marks of all types ripples (lower flow coarse regime) Sh sand, very fine to horizontal lamination, parting planar bed flow very coarse, may be or streaming hneation (1. and u. flow pebbly regime) SI sand, fine low angle (<10 degrees) scour fills, crevasse erossbeds splays, antidunes Se erosional scours with crude erossbedding scour fills intr aclasis Ss sand, fine to coarse broad, shallow scours scour fills may be pebbly including eta cross stratification Sse, She sand analogous to Ss, Sh, Sp eoUan deposits Spe Fl sand, silt, mud fine lamination, very overbank or waning small ripples flood deposits Fsc silt, mud laminated to massive backswamp deposits Fcf mud massive, with freshwater backswamp pond molluscs deposits Fm mud. silt massive, dessication cracks overbank or drape deposits Fr silt, mud rooflets seatearth C coal, carbonaceous mud plants, mud films swamp deposits p carbonate pedogenic features soil 42 conglomerate, Gm, (2) grouped trough cross-bedded sandstone, St, (3) grouped tabular cross-bedded sandstone, Sp, (4) ripple cross-stratified sandstone, Sr, (5) low-angle to horizontally stratified sandstone, SI, and (6) interclast bearing or erosional scour sandstone, Se. The massive to horizontally stratified conglomerate, Gm (Figure 5.1.A), occurs in multiple layers throughout the vertical successions. This conglomerate varies from elast and matrix supported with pebbles and granules as the dominant grains. Thickness varies from 8.5 ft. (Section Tr- 1B) to 2 ft. (Section Tr-IC). Lateral extent ranges from area wide, at the base of the Santa Rosa, to less than three feet at varied positions within sections. The coarse pebble conglomerate is typically found at the base of depositional cycles, directly overiying erosional contacts. Planar cross-bedded sandstone, Sp (Figure 5.1.B), is a minor lithotype in this area. This unit is comprised of medium sands. It is found in only one section of the Santa Rosa Sandstone (Section Tr-IB). The thickness of this bed is 1.0 ft., and the exact lateral extent is unknown, because it is not found in adjacent sections. The lateral extent is limited to less than 1000 ft. The grouped trough cross-bedded sandstone, St (Figure 5.1 .C-D), is also found in multiple layers throughout the vertical successions. The grainsize ranges from very fine to medium sand, and occasionally contains 43 Figure 5.1 .A-D. Outcrop photographs of individual lithofacies units. (A) Horizontally stratified conglomerate (note Permian contact). (B) Planar cross-stratification. (C) Trough cross-stratification. (D) Trough cross- stratification (note fossil wood aligned with paleoflow direction). Jacob staff is five feet tall with one foot increments. 44 pebbles or granules. Thickness ranges from 7 ft. (Section Tr-IB) to 1 ft. (Section Tr-1 A). Lateral extent of a continuous bed ranges from approximately 200 ft. to less than 3 ft. The lithofacies type intraelast bearing or erosional scour sandstone, Se (Figure 5.2.A-B) is found only in Section Tr-2 (Appendix A). Thickness ranges from 1-5 ft. Lateral extent is not known because of poor outcrop exposure adjacent to Tr-2. Intraclasts are composed both clay clasts and reworked sandstone. A thin scour fill is present at sample Tr-2-8a (Appendix A). Grainsize in all beds is very fine sand. Ripple cross-stratified sandstone, Sr (Figure 5.2.C), is an uncommon lithotype. This lithotype is found only in Section Tr-1 A. Thickness ranges from 2 ft. to 2.5 ft. Lateral extent is less than 1000 ft., as this lithofacies is not found in either adjacent vertical succession. The final lithofacies type found in the Santa Rosa is low angle to horizontally stratified sandstone, SI. This lithofacies is present throughout the Santa Rosa outcrops. Thickness ranges from 4.5 ft. (Section Tr-1 A) to 2 ft. (Section Tr-IC). This lithofacies type most likely represents trough cross-stratification, in which the tops of the troughs have been eroded away by migrating dunes, leaving only the low angle bases. If correlated with St at the same level, lateral extent is less than 500 ft. 45 Figure 5.2.A-C. Outcrop photographs of Individual lithofacies units. (A) Erosional scour with llthoclast. (B) Erosional scour with lithodast. (C) Current ripples in cross section. 46 Truiillo Formation Lithofacies The Trujillo Sandstone is represented by five different lithofacies. Each lithofacies type represents a unique depositional environment. The five lithofacies are: (1) massive to horizontally stratified conglomerate, Gm, (2) trough cross-bedded conglomerate, Gt, (3) tabular cross-bedded conglomerate, Gp, (4) trough cross-bedded sandstone, St, and (5) tabular cross-bedded sandstone, Sp. The massive to horizontally stratified conglomerate lithofacies, Gm (Figure 5.1 .A), is the same lithologically to the same lithofacies in the Santa Rosa. In the Trujillo, however, the conglomerates trend more toward matrix supported, with granule sized grains becoming more prevalent. Thickness varies from 7 ft. (Section Tr-4) to 1 ft. (Section Tr-5). Lateral extent can only be traced up to a few tens of feet to less than 5 ft. due to covered section, and being separated by older Santa Rosa outcrops. Trough cross-bedded conglomerate, Gt, is the second lithofacies type in this formation. Trough cross-bedded conglomerates are composed of matrix supported pebble and granule conglomerates. Most trough cross-bedded conglomerates grade into medium to coarse trough cross- bedded sandstones in this formation. Thickness ranges from 1 ft. (Section 47 Tr-5) to 3 ft. (Section Tr-4). Lateral extent falls into the same category as lithofacies Gm. Tabular cross-bedded conglomerate, Gp, is found in one bed in section Tr-4. This tabular conglomerate is found interbedded with tabular cross-bedded sandstone, Sp. It is composed of matrix supported pebble conglomerate. The tabular sandstone lithofacies. Sp, of the same bed is composed of coarse sand. Thickness of this bed is approximately 3 ft. (a minor amount of thickness may have been lost due to off-setting the section over a hill during measurement). Trough cross-bedded sandstone, St (Figure 5.1.C-D), represents the final lithofacies type of the Trujillo in this locality. Grainsize varies from fine to medium sand, with some pebbly/granular beds, in this lithofacies. Thickness ranges from 9.5 ft. to 1 ft. (both in Section Tr-4). Lateral extent fall into the same category as previous lithofacies of the Trujillo. 48 CHAPTER VI DEPOSITIONAL MODELS General The late Triassic Dockum Group is a set of alternating fluvial, deltaic, and lacustrine deposits. The sediments representing the Dockum Group on the Young Ranch, Nolan County, Texas are fluvial deposits. The depositional environment can be determined by analyzing paleocurrent directions obtained from unidirectional flow structures, grainsize, petrography, and the relationships of vertical successions of lithofacies. This data is compiled and compared to modern depositional environments to obtain a more specific view of the depositional history for this locality. The depositional environment can be further specified into a particular depositional system or systems. The depositional systems in question are braided, meandering, or anastomosed fluvial systems. These systems can be broken down further into fluvial styles (Figures 6.1 .A-P). Each fluvial style is represented by a vertical succession of lithofacies that would indicate a particular depositional system or systems (Miall, 1996). Within each of the figures of vertical lithofacies successions (Figure 6.1.A-P) is a vertical succession of Triassic Dockum sediments (Section Tr-1 A) that can be compared to the fluvial models illustrated. It should be 49 (V > • £ (5 00 - C5 "D -«- (O ^^ 0) JO > 0 TO T3 O E Q. c - 0) -a x ."2 "co 2 £f O « 2 0:2 XI CD CO o S^ • cCO o <0 — CO CO O CC o Q. u D) •D C CO O CO O •- ^ "^ o# • 2 S X 05.0 T3 £ t5 CO $ CO < ."2 ":: CD -Q -i u- O ^ 50 C CD CO "53 > CD i_ O LT 05 _C '^ 0) •D C CD woicxcnonne! Moof CTtcsnnB o I ,o.°»'S<..°o°''o."?d°%.%'='o„.) > i ,'':o?? o'.o?" ,">">« ,°-»i'»,' CD ^^ . a) -o^ •?c C CD CD 0) Q: E D) >^ C "O 3 C ff u. — j=.c.C j= j:: r: O CD ;£;ww Oc^a OOC > ^ E CD .3.= f ss o 0 C 0 2 -^ C0£ X ^- . c •a "c 0 0 c c •.^ CD C 0 o E ^• -os> X c •?c55 UJ en •r^ .2 CD 0 V3 V3;«w M 3 CD cn 0 E E 51 O) Lc- 0 Maicxctxyrna Mo)of CJxymei •D T3 —• CD XI xz CO o ^.^ CcD _J o: ' ' O) CO c CD 3 C^ C) > 0 8 ?-5 E CD uc. .1n- <4— Se c •D X CD .Q •D >» "55 o inu e -i c c o CO O § , o X —I •o 5^ CD , 1 •o 0 —; CO ^ o CD E 0 o I— (0 _5 rn a U) c U- < 52 XI 05 T3 0 •g 'cD l_ Xi •g "c MOfCxOionnel MclcrOvnntf C "O i-cP" ° Po D^D^O I 0 0 • • H" "» °'0' O • li • Dl C„ ^„ , , ^^ o-0 o p 00 ° Oc«e«rODOo joo4 ,y QL 2 ''OO''6'^-B';O?O?O»O^ Q.-Q m E E CO CO CO CO CO CD 0 2 o O 0 (V CO 0)u_ >- . 2:2 "^ CD o iS 0 CO CO ^ cS o . _o 0 to 3 0 c 0 JZ CO %St'i. ><"S Sgf T^ im ^- yj yj "^. ro CD «« 0 ^ ^ 0 u. -0 53 noted that it is common for a fluvial system to possess characteristics of one or more fluvial styles (Miall, 1996). Therefore, assigning a specific depositional system to a depositional environment should be done with caution. Multiple channeled streams dominated by suspended load sediments characterize anastomosed streams. Anastomosed streams can be eliminated as a possible model as a result of the lack of suspended load sediments the Dockum (compare Figure 6.1.J to Figure 6.1.X). This leaves the possibility of either a braided stream, or meandering stream. Each of these systems must be addressed in detail to determine the system or systems responsible for deposition of the Dockum Group in this locality. A single major channel characterizes meandering river systems. The banks tend to be resistive to erosion, which keeps the river channel from wandering. These stream channels tend to be sinuous with lower gradients (Boggs, 1995). Channel lag, point bar, crevasse splay, abandoned channel, and overbank deposits dominate meandering systems. Channel sands tend to be linear bodies with a shoestring type appearance (Miall, 1987). Overbank and abandoned channel deposits are primarily composed of very fine grained sediments in all styles of 54 meandering streams. Channel lags and point bars can be composed of sediments ranging from clay to cobble sized clasts (Boggs, 1995). The meandering styles that are similar to the Dockum sediments are styles E and F (compare Figures 6.1 .E-F to Figure 6.1 .X). These styles are meandering streams dominated by sand and gravel sized sediments. The Babbage River, Yukon, Canada is a modern example of a gravel to gravel-sand meandering stream. The Babbage River is a single sinuous channel system dominated by gravel within the channel and sandy point bars. However, the Babbage River also has a significant finer grained sediment fraction that is found in numerous abandoned channels, crevasse splay deposits, and along its well developed floodplain (Forbes, 1983). The Babbage River (Figure 6.1 .E-F) deposition differs from the Dockum Group in the study locality in many aspects. The current directions of flow structures in this type of river vary up to 180° within a one square kilometer section studied by Forbes (1983). Paleocurrent directions on the Young Ranch vary by a maximum of 50°, which would suggest a low sinuosity system. Finer grained sediments are only present in the study locality as rip-up clasts in the Santa Rosa Formation (Section Tr-2). This would indicate floodplain development at some point during deposition. However, these floodplain deposits do not appear to be well 55 preserved or well developed in the area of the Santa Rosa Formation, and no evidence of floodplain deposits are found within the deposits of the Trujillo Formation (compare Figures 6.1.E and F with Dockum; Figure 6.1.X). The Santa Rosa and Trujillo channel deposits are laterally extensive, as opposed to lenticular channel bodies typical of meandering systems. Braided river systems are composed of multiple active channels that are separated by bars or islands (Boggs, 1995). These systems are characterized by very high width to depth ratios ranging between 40 and 300 (Miall, 1982). Slopes are generally greater than other river systems, and banks are easily eroded. This erodability provides a generous sediment source and allows channels to migrate easily and form laterally extensive channel deposits (Miall, 1987). Sediment architecture of braided streams is found as muitistoried channel stacking (Leopold and Wolman, 1957). Braided streams can vary between low to moderate sinuosity, and develop epsilon crossbedded point bars similar to meandering streams (Miall, 1985). Sediment is abundant and water discharge is high, although commonly sporadic (Boggs, 1985). Braided streams are typically found as bed-load fluvial systems. Sediments are transported by bouncing, rolling, or creep along the channel base. Dominant sediment types in braided 56 streams are gravel and sand sized particles. Boulder, cobble, and suspended load sediments may also be present, although not as common. (Pettijohn, 1996). Braided streams are separated into six principle lithofacies assemblage models of deposition. These models are based on modern examples of braided river systems. The models are represented in Figures 6.1.A-P as: Trollheim (A), Scott (B), Donjek (C), Platte (L), South Saskatchewan (M), and Bijou Creek (P) (Miall, 1978). All six braided stream models are defined as low to moderate sinuosity, multiple channeled river systems. The Trollheim type model (Figure 6.1.A) is found in alluvial fan and braidplain settings. Lithofacies are dominated by non-channeled debris flows (Rust, 1978). The Scott type model (Figure 6.1 .B) is found in alluvial fans. Lithofacies are typically horizontally bedded conglomerates, and large longitudinal gravel bars (Boothroyd and Ashley, 1975). This model is composed of greater that 90% gravel through a vertical succession of sediments (Miall, 1978). The Donjek type model (Figure 6.1.C) is composed of horizontally bedded to crossbedded conglomerates and crossbedded to laminated sandstones. This model typically contains from 10-90% gravel through a vertical succession of sediments (Miall, 1978). South Saskatchewan (Figure 6.1.M) and Platte River type models (Figure 57 6.1 .L) are dominated by sandy macroforms with moderately well developed muddy floodplain deposits (Cant and Walker, 1978; Scholle and Spearing, 1982). South Saskatchewan and Platte River models contain less than 10% gravel through a vertical succession of sediments. Bijou Creek type model (Figure 6.1.P) is represented by superimposed flood cycles (Miall, 1978). These deposits are typically lacking macroforms, such as large migrating dunes. Desiccation features, in the form of mud cracks, may be abundant in Bijou Creek systems due to sporadic flow/flood cycles (Miall, 1985). Fluvial systems responsible for deposition of the Santa Rosa and Trujillo formations can be separated from these models. There are no debris flow deposits, and the overall gravel percentage is less than 90%, which eliminates Trollheim and Scott models of deposition (compare Figures 6.1 A and B with Dockum; Figure 6.1.X). The Dockum does contain greater than 10% gravel (see Dockum; Figure 6.1.X). This eliminates the possibility of a South Saskatchewan (Figure 6.1 .M) or Platte River type model (Figure 6.1 .L) of deposition. Finally, there are no superimposed flood cycles that would indicate a Bijou Creek type model (compare Figure 6.1.P with Figure 6.1.X). 58 Dockum Depositional Model It should be reiterated that classification of a depositional system as a single model could be erroneous. However, a comparison of the Dockum (Figure 6.1 .X) to that of the Donjek River model (Figure 6.1 .C) in Yukon, Canada reveals a model which most closely fits the sedimentation style of the late Triassic Dockum Group on the Young Ranch. The Donjek type model is that of a low to moderate sinuosity, mixed-load, braided fluvial system (Rust, 1978). This model is represented by distinct fining upward cycles ranging from massive or horizontally bedded gravel to crossbedded to laminated sandstones (Scholle and Spearing, 1982). Gravel abundance in the Donjek model ranges between 10-90% (Miall, 1978). There are two more possible fluvial depositional models that may have been responsible for deposition of the Triassic sediments on the Young Ranch. The possibility of an incised valley-fill environment or deposition in a low-sinuosity, channel belt must be taken into account. Incised valleys represent periods of sediment bypass/erosion due to increased stream discharge and decreased/stable sediment influx. Valleys are typically narrow, steep walled, and are lacking development of floodplain fades. Valley incision occurs based on changes in discharge and sediment supply. This is controlled by local variables such as 59 teetonism, climate change, glaeiaflon, and base level changes (Zaiflin et al., 1994). Sedimentation occurs as flow is subsiding by climate change, or by channel avulsion. This deposition is often represented as a distinct fining upward sequence (Miall, 1996). Channel geometry within an incised valley can occur as either meandering or braided fluvial systems, depending on slope and geometry of the incised valley. A problem can arise in concluding that an ancient fluvial system is a braided stream. For a fluvial system to be braided, there must be two or more active channels. If only one channel were active over long periods of time, then a low-sinuosity channel belt fluvial system must be addressed as a possible depositional environment. A low-sinuosity, channel belt can create sediment architecture similar to that of a braided stream environment. During a period of aggradation or tectonic slope change, channel avulsion causes stream flow to abandon the main channel and create a new channel. If there is great frequency of avulsion, channel belt deposits remain substanfially interconnected (Bridge and Tye, 2000). These connected channel belts may resemble a mulfi-storied channel stacking architecture, forming large-scale sheet-like channel bodies similar to that of a braided stream (Bridge, 1984). Channel belt abandonment due to aggradation can be caused by tectonic shifts, climate changes, or changes in base level similariy to incised valley formation (Bridge, 1984). 60 Teetonism provides changes to drainage network, sediment supply, and climate. Climate can affect discharge, sediment supply, and affects relatively large areas simultaneously. Local glaeiaflon would have no effect in this area based on the area's proximity to the equator during the Late Triassic Epoch. Base level change could be represented by basinal subsidence, which might alter stream flow. Any of these factors separately, or in conjuneflon, could create an environment beneficial for fluvial incision, or channel belt abandonment during aggradafion (Blum, 1993; Bridge, 1984). The possibility of an incised valley fill or channel belt abandonment as deposiflonal environments will be introduced in the next secfion. Santa Rosa Depositional History As previously stated, the depositional system responsible for transport and sedimentation of the Santa Rosa is inferred as a braided river system from comparison to modern fiuvial systems (Figures 6.1-4). The interpretation of the Santa Rosa as a braided stream can also be made by direct comparison of characteristics of meandering, anastomosed, and braided streams (Table 6.1). No point bar deposits (lateral accretion surfaces) are found within the Santa Rosa Formation on the Young Ranch. Fades representing the 61 Table 6.1: Characteristic's of braided, anastomosing, and meandering stream deposits compared to characteristics of Triassic Dockum Group on the Young Ranch (Pettijohnet. al., 1987). Meandering Braided Anastomosing Cyclicity Weil-defined classic point Weak to poor for both grain Well-defined but interuptible bars; multistory: NO size and structures; multi fining-upward to blocky story: YES cycles; multistory: NO Lithology Sand, silt, and mud, plus Gravel, sandy gravel, and Sand, silt, and mud, plus peat peat, climate permitting: NO sand, with negligible mud; climate permitting: NO some debris flows: YES Map Pattern Narrow to broad belts, with Nan-ow to broad linear belts, Narrow to broad belts with sharply scalloped boundaries plus fans, all fairly straight straight channels and bound resulting from low channel boundaries, many multiple aries, resulting from high stability, many splays: NO unstable, interconnected channel stability; some inter channels: YES connected channels: YES Size gradients down dip Weak for sand fraction b/c Commonly strong trends, b/c Weak for sand fraction b/c of low gradients: NO of high gradients: YES of low gradients: NO Paleocurrents High variance; epsilon cross- Low variance: YES Low variance: YES bedding common: NO Fossils Never abundant, but trace Rare, but some vertebrate Never abundant, but trace fossils, logs, and freshwater debris and logs possible as fossils, logs, and freshwater invertebrates possible: YES channel lag: YES invertebrates possible: YES 62 Santa Rosa are primarily channel deposits, with minor fades indicating linguoid and transverse bars. Sequences of lithofacies are bounded by erosional surfaces in a very similar manner as fluvial deposits in the Donjek River, Yukon, Canada described by Rust (1972). This set of lithofades reflects the cydie deposition characteristic of the Donjek type model (Rust, 1972). Sediments of the Santa Rosa Formation are composed of a continuous series of channel deposits, while meandering streams are composed of lenticular channel deposits with abundant epsilon erossbeds. Deposits are arranged in a muitistoried channel stacking architecture (Figures 6.2 and 6.3). The paleocurrent analysis illustrates a mean flow direction of 191° with a standard deviation of 35° (see Chapter V), over the nine square mile area studied, throughout deposition of the Santa Rosa. Paleocurrent data, vertical relationships of lithofacies, and deposit architecture suggest deposition in a braided stream environment. Massive to horizontally stratified conglomerates represent channel lag deposits, which are typically overiying erosional surfaces. These sediments were deposited in major channels during higher stream discharge (Allen, 1965). Trough cross-bedded sandstone overiies the conglomerates. Trough cross-bedded sandstones (Figure 5.1.C-D) 63 Figure 6.2. Drawing of multi-storied channel stacking architecture found in the Santa Rosa Formation. Figure 6.3. Outcrop photograph of a single channel deposit In the Santa Rosa Formation, which pinches out in both directions (Jacob staff is five feet tall, and channel is outlined in black). 64 indicate deposition by migrating lunate dunes in deeper major channels (Wulf, 1962; Miall, 1985). Thick sections of trough cross-bedded sandstones represent channels that remained stationary over a long period of time (Fritz, 1991). Tabular cross-bedding (Figure 5.1.B) and low-angle erossbeds may have been deposited in either sand wave deposits, linguoid or transverse bars at the lower flow regime (Boothyard and Ashley, 1975; Miall 1977). Current ripples (Figure 5.2.C) form a minor part of the Santa Rosa. They are deposited in channels and along bar tops during low flow regime (Karpeta, 1993). Section Tr-2 contains crudely cross-bedded fades that contain intraclasts (Figure 5.2.A-B). These deposits most likely represent scour fills on transverse bars (Miall, 1982). There is a problem in interpreting an ancient fluvial system as braided. To be braided, a system must have multiple active channels. Although multiple channels are visible in outcrop, there may not have been more than one active channel over a substantial period of time. In this case, a low-sinuosity, channel belt that frequentiy abandoned its major channel due to aggradation could be an alternative model of the depositional environment. As discussed eariier in this chapter, channel belt abandonment creates multiple channels due to avulsion from tectonic, dimate, or base level changes. If avulsion occurs frequentiy, the channels remain somewhat interconnected, and stack on top of previous channels 65 similariy to multi-storied channel stacking architedure that is indicative of braided stream systems (Bridge, 1984). If two or more channels were not active at the same time, this is the depositional model for the Santa Rosa Formation. The paleoclimate can be inferred from lithofades, and paleocurrent analyses. Sheetflood sand deposits present may indicate an ephemeral stream flow in ancient river systems. The structure indicating sheetflood deposits is an upper flow regime plane bedded or horizontally laminated sandstone (Fritz, 1991). There are no upper flow regime sheetflood structures found in the Santa Rosa on the Young Ranch that might suggest deposition by ephemeral streams. The fluvial system can be inferred as a perennial stream, as a result of lack of periodic flow deposits. In section Tr-2, a layer of caliche is present within the vertical succession of deposits (Figure 6.4). Formation of caliche requires a stable substrate for a sufficientiy long period of time with consistent climate conditions for pedogenic development. This caliche layer indicates a subhumid to semi-arid climate (Scholle et al., 1983). The indication of a perennial stream and presence of a caliche horizon suggests an overall subhumid climate for this area during deposition of the Santa Rosa Formation. 66 Figure 6.4. Photomicrograph of Santa Rosa caliche layer in section Tr-2. Field of view = 3.5 mm. Figure 6.5.A-B. (A) Photomicrograph of radiolarian ghosts in a chert grain of the Santa Rosa Fonnation shown in plane light. (B) Same photomicrograph shown in polarized light. Field of view for botii photos = 3.5 mm. 67 The source area for the Santa Rosa Formation over the extent of the Dockum Basin had been previously described as a peripheral filled basin from all structural highs surrounding the area (McGowen et al., 1979). Previous work demonstrated that the sediments of the Santa Rosa of west Texas were derived from erosion of the present-day Wichita and Arbuckle Mountains (Riggs et al, 1996). This sediment provenance determination is based on uranium/lead isotopie dating (2°^Pb/"®U, ^'^^Pb/^^^U, and 207p|^/206p|3^ in detrital zircon grains (Figure 3.5.B). The detrital zircon study coincides with paleocurrent structures found on the Young Ranch. The overall paleocurrent direction for the Santa Rosa Formation is 191°, as stated in Chapter V. This would also indicate a sediment provenance in the Wichita-Arbuckle Mountains to the northeast. Sediment provenance can also be determined petrographieally, although not as definitive by itself. Chert pebbles with radiolarians found in the Santa Rosa have been traced to chert and flint deposits in the Woodford Formation of Oklahoma and the Arkansas Novaculite (Roth, 1943). Tracing of chert grains is done based on the similarity of grains and the presence of radiolarian ghosts found in these pebbles (see Figure 6.5.A-B). This petrographic study has been used in conjunction with paleocurrent direction to delineate the most likely sediment source of the Santa Rosa Formation. The southward paleocurrent direction (Chapter V) 68 used in conjunction with petrographic analysis indicates a sediment provenance in the Wichita-Arbuckle Mountains. Truiillo Depositional History Deposition of the Trujillo Formation was preceded by a change in basin geometry, tectonic slope of the region, or both. During the Late Triassic Epoch, there was uplift along the interior zone of the Ouachita Tectonic Belt after Pangea had broken up, and the present day Gulf of Mexico was opening (Long and Lehman, 1993). The stratigraphically older Santa Rosa Formation was deposited in a southwest flowing fluvial system. Changes in tectonic slope or basinal subsidence allowed for entrance of a younger fluvial depositional system to enter this locality in a northward flowing fluvial system. The sediments representing the Trujillo are lithologically similar to those representing the Santa Rosa Formation, and separation of the two systems has been noted in Chapters IV and V. The lithofacies present within the Trujillo Formation also resemble those of a braided river system. The Trujillo consists of lithofacies representing both major and minor channel fades. The channel fades exhibit a fining upwards sequence, although not as pronounced as that in the Santa Rosa. The typical sequence found in the Trujillo Formation is as follows: massive to horizontally stratified conglomerate, trough eross- 69 bedded conglomerate, trough cross-bedded sandstone, and interbedded tabular cross-bedded conglomerate and sandstone. The massive to horizontally stratified conglomerate represents channel lag deposits within a major channel at high stream velocity. Direetiy overiying coarse pebble conglomerates is the trough cross-bedded sandstone fades. This fades represents deposition by migrating lunate dunes in major channels at lower flow regime (Wulf, 1962; Miall, 1985). Possible minor channel fades are represented by trough cross-bedded conglomerate overiying an erosional or gradational contact. These deposits are overiain by trough cross-bedded sandstones, which represent deposition by migrating lunate dunes at lower flow regime (Wulf, 1962; Miall, 1985). This depositional sequence of lithofacies is also similar to the Donjek type model described by Rust (1972) and that of the Santa Rosa Formation. This might suggest deposition in a braided stream environment similar to that of the Santa Rosa Formation. However, stream flow appears to be either less sporadic than the fluvial system that deposited the Santa Rosa. Fewer erosional contacts are present, and gradational contacts, as opposed to erosional surfaces, mark grainsize cycles. Multi- storied channels are not evident in outcrops of the Trujillo, although they may be present as Trujillo outcrops are not exposed as well as those of the 70 Santa Rosa. As a result of the proximity of the younger Trujillo Formation to that of the older Santa Rosa Formation at the same topographic level, a braided fluvial system does not appear to be the actual depositional environment of the Trujillo Formation on the Young Ranch. The inferred depositional environment responsible for the Trujillo Formation in this locality is that of an incised valley fill (Figure 6.6). The inference is made based on the close proximity of the Trujillo sediments to those representing the Santa Rosa Formation at the same topographic level. No floodplain deposits are found, nor is there any evidence of their presence at anytime during deposition (e.g., mud intraclasts). Unconformable surfaces are not exposed between the Santa Rosa and either of the inferred channel fills of the Trujillo Formation, but a paleocurrent reversal is found near the base of section Tr-4, where the section was measured over a hill (Figure 4.3). As a result, the incised valley fill depositional system can only be speculated based on topographic level, and relatively close proximity of the Trujillo in relation to the Santa Rosa. Sediments within the incised channels commonly exhibit a series of fining upward sequences (Miall, 1996). In both sections (Tr-4 and 5), fining upward sequences can be seen as gradational contacts that indicate slowly depleting discharge. This is a common occurrence in incised 71 Figure 6.6. Drawing offluvial system s that incised the Santa Rosa Formation and depositedtine Trujill o Fonnation within the incised valleys. Figure 6.7. Photomicrograph of Trujillo caliche layer in section Tr-5. Field of view = 3.5mm. 72 channels due to channel avulsion and short term dimatic changes (Miall, 1996). The incised valleys of the Trujillo Formation on the Young Ranch may or may not have been deposited at the same time. Grainsize remains fairiy constant through both sections, but there are subtie differences in mineralogieal composition. Samples taken from the top of section Tr-5 appear to be lithologically similar to samples from the base of section Tr-4 (Appendices A and B). The indsed valley represented in section Tr-4 may be stratigraphically younger than the valley represented by section Tr-5. Paleoclimate can be inferred from lithofacies and paleocurrent analyses of the Trujillo, similariy to that of the Santa Rosa. There are no horizontally laminated sheetflood deposits present that would indicate an ephemeral stream (Fritz, 1991). This indicates that a perennial stream deposited the Trujillo, as well. A caliche layer is located within the vertical lithofacies assemblage in section Tr 5 (Figure 6.7). This caliche deposit is not as thick, nor as well developed as the Santa Rosa caliche in section Tr-2. Evidence of perennial stream flow and presence of the caliche layer indicate climate conditions during the deposition of the Trujillo Formation as subhumid. If dimate conditions remained constant during the hiatus between deposition of the Santa Rosa and the Trujillo Formations, this would support basinal subsidence, and/or regional teetonism as the cause 73 for changing fluvial systems and sediment provenance for deposition of stratigraphically younger Trujillo Formation. The sediment provenance of the Trujillo is determined form paleocurrent analysis and petrographic analysis. Overall paleocurrent flow direction for the Trujillo is 354° (see Chapter V). The apparent sediment provenance from flow direction is the southern portion of the Ouachita Tectonic Belt. Petrographic analysis reveals sediments that are very similar to those of the Santa Rosa Formation. However, there are fewer sediments in the gravel sized fraction (>2 mm) compared to the Santa Rosa Formation. Gravel sediments in the Trujillo Formation are composed of various pebble types (same as Santa Rosa) with sediment provenance predominately in the Marathon Uplift area. Quartzite and quartz schist pebbles are much more common in the Trujillo Formation, and were most likely derived from the Marathon Uplift, as well. In the sandstone layers, mica schist and phyllite are common, as well (see Chapter III). These metamorphic rock fragments were also likely derived from the same source area as quartzite and quartz schist clasts (Roth, 1943). Micas have been dated using K'^^/Ar'^" and Rb^VSr^'' for both muscovite and biotite grains. The source of muscovite is the Devonian rocks of the Southern Ouachita Tectonic Belt, and the source of the biotite grains Is from late Triassic volcanism (see Chapter III) in the same area (Long and Lehman, 74 1993). Radiolarian ghosts are found in chert pebbles of the Trujillo Formation, as well (Figure 6.8.A-B). The source of these chert pebbles has been reported as the Caballos Novaculite (Roth, 1943). The radiolarians should be identified to ensure they were not derived from the erosion of the Santa Rosa Formation during incision, however. Petrography and paleocurrent analyses, used in conjunction, demonstrate that the likely sediment provenance for the Trujillo was Southern Ouachita Tectonic Belt (Marathon Uplift). 75 Figure 6.8.A-D. Photomicrographs of radiolarian ghosts in chert pebbles of the Trujillo Formation. (A) Radiolarians in plane light. (B) Photo A shown in polarized light. (C) Radiolarians in plane light. (D) Photo C shown in polarized light. Field of view for all photos is 1.7 mm. 76 CHAPTER VII DIAGENETIC HISTORY Evidence of eight diagenetie events has been observed in the rocks of the Late Triassic Dockum Group. These diagenetie events are marked by precipitation of minerals in pore spaces, alteration of pre-existing minerals/cements, and grain replacement by precipitated minerals. Diagenetie events are controlled by chemistry of pore fluids flowing through sediments, temperature, and burial depth (Boggs, 1995). The diagenetie events found in the Dockum Group on the Young Ranch are: precipitation of kaolinite, iron-oxide, baroque (zoned) dolomite, calcite, silica, and gypsum cements, dedolomitization of baroque dolomite, and grain replacement during emplacement of poikilitopic calcite. The relative sequence of diagenetie events has been determined through petrographic analysis (Figure 7.1). Timing of some events has been approximated through correlation of diagenetie events in overiying Cretaceous formations. Kaolinite (Figure 7.2.A) and iron oxide (Figure 7.2.B) cement precipitation are the primary diagenetie events in the Dockum Group. Kaolinite is the primary pore filling cement with iron oxide filling the remaining pore space in some samples, while others have iron oxide grain 77 Diagenetie Minerals Late Triassic Dockum Group Kaolinite Iron-Oxide Zoned Dolomite Dedolomitization/ Poikilitopic Calcite Quartz Overgrowths and Microcrystalline Quartz Gypsum Time > Figure 7.1. Paragenetic sequence of cementation events shown in relative order versus time since deposition. 78 Figure 7.2.A-D. Photomicrographs of diagenetie events. (A) Kaolinite cement In polarized light (field of view = 0.85 mm). (B) Iron oxide cement in polarized light (field of view = 3.5 mm). (C) Zoned dolomite and dedolomite in polarized light (field of view = 3.5 mm). (D) Zoned dolomite in poikilitopic calcite in plane light (field of view =1.7 mm). 79 coatings with kaolinite filling the remaining pore space. Precipitation of compositionally zoned dolomite (Figure 7.2C-D) is the secondary diagenetie event. Dolomite cementation occurred after kaolinite and iron oxide, and before quartz cementation and poikilitopic calcite/dedolomitization. Due to the proximity of timing of emplacement of quartz and calcite during post-Lower Cretaceous exposure, it is assumed that the dolomite occurred prior to quartz overgrowths. Quartz overgrowths and microcrystalline quartz emplacement (Figure 7.3.A-D) represent tertiary diagenetie events. Silica cementation occurred relatively dose to the surface, during exposure of the overiying Cretaceous formations. Dedolomitization (Figure 7.2.C), precipitation of poikilitopic calcite (Figure 7.4.A-B), and grain replacement by poikilitopic calcite represent the quaternary diagenetie events (Figure 7.4.B). Timing of quartz and calcite cannot be separated petrographieally as they do not occur within similar rocks. They cannot occur at the same time, as silica is in solution in basic groundwaters, and carbonate is in solution in acidic groundwaters. Jacka (1977) determined that the silica in this area was emplaced prior to dissolution of the Lower Cretaceous Kirsehberg Evaporite and subsequent predpitation of poikilitopic calcite. A reemergenee of iron-oxide predpitation began during emplacement of 80 -?-# •» Figure 7.3.A-D. Photomicrographs of diagenetie events. (A) Microcrystalline quartz and quartz overgrowths in plane light. (B) Photo A shown in polarized light. (C) Microcrystalline quartz and quartz overgrowths In plane light. (D) Photo C shown in polarized light. Field of view In all photos = 3.5 mm. 81 Figure 7.4.A-D. Photomicrographs of diagenetie events. (A) Poikilitopic calcite cement. (B) Poikilitopic calcite with caldte replacing quartz grains. (C) Gypsum cement (D) Gypsum cement Field of view = 3.5 mm in photos A, B, and C. Field of view = 1.7 mm in photo D. 82 poikilitopic calcite, in the form of grain coatings. Gypsum (Figure 7.4.C-D) is the most recent event in the Dockum Group on the Young Ranch. Kaolinite Cement Kaolinite, occurring as a pore filling cement, is one of the primary diagenetie events (Figure 7.2.A). Kaolinite can be predpitated in a variety of ways. Dissolution of potassium feldspars can create a large volume of aluminum required for kaolinite formation (Stoessell and Thomson, 1985). Kaolinite can be formed through transformation of mixtures of detrital smectite and weathered micas, as well (Pettijohn et al., 1972). Another possible mechanism for kaolinite formation is a relationship of relatively eariy emplacement of kaolinite in correspondence with eariy generation of organic acids by decarboxylation of kerogen (Carothers and Kharaka, 1978). Potassium feldspar grains appear relatively unaltered, and there is no evidence of detrital clays that may have been altered. Due to the relatively eariy emplacement of kaolinite, the most likely source of precipitation is relatively fresh groundwaters entering the sandstones from a recharge outcrop that contained an abundant supply of dissolved silica from chemical weathering (Pettijohn et al., 1987). 83 Iron Oxide Cement Iron-oxide minerals represent primary and quaternary diagenetie events in the form of pore filling and grain coating cements (Figure 7.2.B). The iron-oxide cements in the Triassic Dockum group appear to be in the form of hematite (pore filling) and limonite (grain coating). Iron-oxide minerals typically form in sediments from the alteration of iron-rich minerals. Alteration of iron-rich minerals in vadose and phreatic zones shortly after deposition creates the availability of iron, which is necessary to form iron-oxide cements (Malicse and Mazzulo, 1996). The diagenetie process involves the dehydration of the brown amorphous ferric oxide to limonite, and dehydration of limonite to hematite. The source of the iron oxide is most likely a result of alteration of iron-rich minerals (magnetite, and hematite). Dissolution of iron-rich silicates can also lead to precipitation of hematite in the presence of well- circulated, oxidized meteoric water (Pettijohn et al., 1987). Zoned Dolomite Cement Precipitation of compositionally zoned dolomite (Figure 7.2.C-D) is the secondary diagenetie event. For the most part, dolomite crystals have been replaced by calcite (dedolomite). There are, however, isolated crystals that were not replaced by calcite. Staining by Alizarin Red-S 84 reveals dolomite crystals that have been replaced by calcite, while unaltered crystals are unstained (Figure 7.2.C). Zoning in dolomite crystals can be observed by the presence of iron oxide layers within the individual crystals. This suggests a compositional zoning with alternating layers of iron-rich and iron-poor dolomite. Compositionally zoned or baroque dolomite is typically considered a burial diagenetie event, occurring at depths greater than 500 m (Mountjoy and Amthor, 1994). Temperature of formation is typically thought to be between 60 and 150° C, which would tend to be at greater burial depths or in hydrothermal settings (Hesse and Abid, 1998; Spoti and Pitman, 1998). However, near surface formation of zoned dolomite has been found in temperature between 25-40° C with 5^^0 values close to 0 %o SMOW (Assereto and Folk, 1980; Spoti and Pitman, 1998). The burial depth of the Triassic Dockum Group in this area is subject to question. However, if the Cretaceous section is correlated to back to the area from the Gulf Coast, a burial depth of greater than 500 m. is possible. The coarse dolomite crystal size also suggests a relatively deep burial diagenetie event. Emplacement of zoned-dolomite was most likely the result of vigorous drculation of relatively warm basinal brines. A similar process for the origin of zoned dolomite has been reported by Radke and Mathis (1980), in the Black Lake Field, Louisiana. 85 Quartz Overcrowths and Microcrvstalline Quartz Precipitation of quartz overgrowths and microcrystalline quartz cement (Figure 7.3.A-D) represent the tertiary diagenetie events. The rock units of the Triassic Dockum Group containing silica overgrowths are found in two sections (Tr-1 D and 3). The silieified layers are the uppermost layers of each section, which is just below the Lower Cretaceous Antiers Sandstone. These layers are both within a silieified "channel" of the Antiers Sandstone (Wood, 2001), and most likely received silica emplacement in the same manner as the overlying Antlers. The overiying Antiers Sandstone is concluded to be a shallow burial, pedogenic silerete or silieified soil horizon that formed during post-Lower Cretaceous Edwards exposure (Wood, 2001). Pedogenic silcretes are represented by large amounts of opal, chalcedony, and microquartz cement (Thiry et al., 1991). Initial cementation in a pedogenic silerete is typically in the form of opal (amorphous quartz) (Graetsch, 1994). Dissolution and reprecipitation of pedogenic silica in the form of microcrystalline and megaquartz overgrowths appears to be the mode of emplacement of silica cement in the topographically high Triassic rocks located below the silieified Antiers "channel" (Wood, 2001). The quartz overgrowths have preferentially nudeated on single crystal quartz grains of 86 similar composition, and microcrystalline quartz cement predpitated on chert (microcrystalline quartz) grains. Poikilitopic Calcite/Dedolomite Cement and Grain Replacement Dedolomitization (Figure 7.2.A) and precipitation of poikilitopic calcite (Figure 7.4.A-B) are the quaternary diagenetie events. The event of dedolomitization involves the previously emplaced zoned dolomite crystals being replaced by calcite. This process is initiated by a change in the Ca/Mg ratio in the pore fluids. Dissolution of anhydrite/gypsum evaporites in close proximity to dolomites may lead to an increase in the Ca/Mg ratios which results in the dolomites being replaced by crystalline calcite (Blatt, 1992). An outcrop of the Lower Cretaceous Edwards Formation in the Mulberry Canyon area (10 miles from this study area) contains large vugs that have been interpreted as dissolution of anhydrite/gypsum nodules (Welch, 2001). This correlates with crystalline limestone and collapse breeda in the Robert Lee Section near San Angelo (Welch, 2001) and the Kirsehberg Evaporite, which is exposed near Junction, Texas (Moore, 1969; Welch, 2001). These crystalline limestones are reported to contain dedolomite (Moore, 1969). 87 Dissolution of the gypsum and anhydrite in the Lower Cretaceous Kirsehberg Evaporite, due to subaerial exposure, has been conduded to cause the collapse breccia (Moore, 1969), and would signifieantiy raise the Ca/Mg ratio (Blatt, 1992). The post-Edwards exposure and dissolution of the Kirsehberg Evaporite may have caused the dedolomitization of the zoned dolomite (Figure 7.2.A) in the Triassic Dockum Group on the Young Ranch. Poikilitopic calcite and grain replacement by calcite are commonly found in clastic sedimentary units in close proximity to dedolomite due to the high Ca/Mg ratio in the pore fluids (Morad, 1998). Poikilitopic calcite cement involves large crystals of calcite engulfing framework detrital grains as the calcite crystals grow (Morad, 1998). Poikilitopic calcite-cemented rocks often appear to be loosely packed which is due to grain replacement. Grain replacement occurs in relatively large pores when large calcite crystals engulf and partially replace clays, kaolin, and dolomite as the calcite crystals grow. These calcite crystals also corrode framework grains such as quartz, and totally replace feldspars (Morad et al., 1998). Figure 7.4.B shows remnant grains that have been almost totally replaced, along with embayments within quartz crystals. 88 Gvpsum Cement Gypsum cement (Figure 7.4.C-D) is the most recent diagenetie event. The Santa Rosa Formation has numerous freshwater springs on the Young Ranch. Evaporite cements may precipitate where Ca or Mg carbonate-bearing groundwaters mix with Ca or Mg sulfate or chloride rich groundwaters in arid conditions. They preferentially form where drainages converge, flow gradients decrease, where permeabilities are low, or flow is draining from outcrop (Wright, 1992). An alternative method of emplacement of gypsum could be dissolution of gypsum from the Permian Quartermaster Formation, and precipitation of gypsum from desiccation of the spring. Gypsum cementation is a relatively minor component in the Triassic Dockum Group on the Young Ranch. 89 CHAPTER XIII SUMMARY The Late Triassic Dockum Group is composed of a series of continental fluvial, lacustrine, and deltaic deposits that range from west Texas, Eastern New Mexico, Southeastern Colorado, and Western Oklahoma and Kansas. The Dockum unconformably overiies the Permian Quartermaster Formation, and is unconformably overiain by the Lower Cretaceous Antlers Sandstone on the Young Ranch. The Dockum Group is represented by the Santa Rosa and Trujillo Formations at this location. The Santa Rosa is the basal unit of the Dockum Group. This formation consists of alternating layers of fluvial sandstones and conglomerates. The stratigraphically younger Trujillo formation is also comprised of alternating layers of fluvial sandstones and conglomerates. The two formations are virtually inseparable in outcrop, as they are almost identical lithologically. This problem is compounded by the fact that they are found on the same topographic level across the ranch. A petrographic analysis was performed on the Triassic sediments to enable identification of the Santa Rosa and Trujillo Formations based on lithologieal differences. The rocks were classified using Folk's (1968) classification scheme. There was still no separation in the two formations. 90 The dassification was performed again with conglomerates removed. This method revealed a petrographic separation of the two formations that agreed with previous work done on the Dockum Group in New Mexico and the Texas Panhandle. The Santa Rosa Formation is more quartzose and arkosic than the younger Trujillo Formation. The Trujillo contains a larger amount of lithic fragments. Further separation can be made based on accessory minerals present in the two formations. The Santa Rosa Formation contains more muscovite and zircons than the Trujillo, and the zircons are much larger in the Santa Rosa Formation (closer to the mean sand grainsize). The Trujillo Formation contains more metamorphic and volcanic rock fragments. Schist fragments, phyllite fragments, biotite, muscovite, garnets, and hornblende are found as accessory minerals and rock fragments in the Trujillo Formation. In addition, the Santa Rosa Formation is comprised of a coarser grainsize than the Trujillo Formation. Zircon dating in the Santa Rosa Formation shows a sediment provenance in the present day Wichita and Arbuckle Mountains. The Trujillo Formation's sediment provenance is known from dating of both muscovite and biotite grains. The muscovite is dated as Devonian, and the biotite is dated as Triassic. This indicates a Southern Ouachita Tectonic 91 Belt (Marathon Uplift) source (Devonian) and a Triassic volcanic source located to the south. The conclusions made from the petrographic analysis are supported by the paleocurrent analysis. There is an overall 180° shift in paleocurrent direction in the Dockum Group on the ranch. The Santa Rosa has a generally south to southwest paleocurrent direction, and the Trujillo Formation trends to the north. The Santa Rosa and Trujillo Formations have been identified on the ranch based on comparison of paleocurrent and petrographic data to previous work done on the Dockum Group. The depositional model for the Santa Rosa Formation is based on comparison of lithofacies, and sediment architecture to that of Miall's (1981) sixteen modern fluvial environments. Sedimentary structures present, cumulative gravel-sized grain percentage, and a muitistoried channel stacking architecture indicate deposition in a deep, gravel-bed, braided stream environment. This fluvial model contains between 10-90 % gravel, and no debris flow or sheetflood sedimentary structures. The depositional model for the Trujillo Formation is made in the same manner. However, there is no evidence of muitistoried channel stacking to indicate a braided stream. The proximity of the two sections of the Trujillo sediments to the Santa Rosa sections at the same topographic level lead to the conclusion of an incised valley fill as the depositional 92 environment for the Trujillo Formation. The abundance of graded and inversely graded bedding found in the Trujillo Formation further supports deposition in a restricted channel. Climate during the Late Triassic Epoch in this area is inferred based on the lack of ephemeral stream evidence, such as plane-bedded sandstones. Caliche layers are present in both the Santa Rosa and the Trujillo Formations. The lack of ephemeral sheetflood deposits and the presence of caliche layers indicate a subhumid climate during the Late Triassic Period in this area. The diagenetie history of the Dockum Group in this area has been determined through petrographic analysis. Kaolinite and iron oxide are the primary cementing events. Zoned dolomite is the secondary cementing event. This type of dolomite is typical of deeper burial (> 500 m.), and is comprised of relatively coarse crystals. Quartz overgrowths and microcrystalline quartz are the tertiary cementing event. These cement types occur only in topographically high areas on the ranch that were once direetiy overiain by the Lower Cretaceous Antiers Sandstone, where the Antiers is represented by a pedogenic silerete. Timing of this cement is interpreted as post-Lower Cretaceous Edwards from previous work. Dedolomite and poikilitopic calcite are the quaternary cementing events. Most of the previously emplaced zoned dolomite was replaced by calcite, 93 and where no dolomite was present, poikilitopic calcite was precipitated. Timing of this diagenetie event is inferred from comparison to the Lower Cretaceous Edwards Formation in nearby Taylor County, Texas. In Taylor County, dedolomite occurred during post Edwards exposure due to the dissolution of the Kirsehberg Evaporite. 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R., 1994, The Stratigraphie Organization of Indsed-Valley Systems Associated With Relative Sea-Level Change, in Dalrymple. R. W., Boyd, R., and Zaitiin, B. A., Incised-Valley Systems: Origin and Sedimentary Sequences: SEPM Spedal Publication 51, 45-60 p. 102 APPENDIX A MEASURED STRATIGRAPHIC SECTIONS . •:•...•.•.•••.•.:.••. O 0 0 O O C C G O 0 C 0 M •"•••• .••.•••••.•.•••.••.•..-••.•. n O o O n o o C r 0 c 0 n O o ° 1 Sandstone Conglomerate Siltstone Trough Crossbedded Sandstone ['•yf>^•: • .'.;^;.' •; •^^•••.: •.••.•• "J •^^^. ' '.'"•" -^-i::^ ' .• ' ' ' ."-^ "j Ripple Cross-stratified Low Angle Cross-Stratified Sandstone Sandstone O .o-o -o-o -O 'C • 0 • C. 6 -6 • o '• '0 |G 0 o' O 0 C C O O 0 O G M . o 9 'o—^c". ''-"-o • o .'r. .0. o-c."n .o-^: o; Horizontal Stratified Low Angle Cross-Stratified Conglomerate Conglomerate O C O O 0 O O 0 O C C o C] |G • C . C • C • O • 0 -O O • O • C • G • G • '-• Trough Crosst)edded Trough Crossbedded Conglomerate Sandy Conglomerate 1 0 O •"' c . C • (-' • L; - ^ • C . C ..O O'O O'C'O O'O o lo- o-o o- c-o-o -o-o- Planar Crossbedded Trough Crosst>edded Sandstone arKi Conglonnerate Pebbly Sandstone o.o '0 -o-o -O -O-O-O. O -G • o "'J ; • ." -'c . '.•••'•. 'o.' ''. •'. •'. -o- • •- M Sandy Conglomerate Pebbly Sandstone =/ c- 0 c.°'o '^ 0 . c c c _o • o 0. 6 =• .O'^.O .^'o-r-o'C-O-O-"^ •C.cr.c..! Zi iT-ll L^ Un LTi '^1 LI t-^i L Granular Sandstone Caliche Sandy Conglomerate Lens Conglomerate Lens Sandstone Lens Clay Lens Fossil Wcxxl Erosional Contact Erosional Unconformity Gradational Contact Figure A.I. Legend of litiiology symbols used in measured stratigraphie sections. 103 Section Tr-1 A 48. Yellowish-brown very fine sandstone: Kaolinite = 2ft. Sr cemented supermature meta fragment bearing sublitharenite St 4A. Yellowish brown medium sandstone: Kaolinite cemented supermature meta fragment bearing sublitharenite • 6 9 6 -^-c. °-c -""c .c -o- o °. o'P c-r~s -o -c. o .c"^ .o-o. C .0 'o. ' Oo • 3C. Reddish brown sandy pebble conglomerate: •O ?'o .°'C'. '^•c • O .'o -O. O'C'O .° "c-c;--o Gh Calcite cemented submature chert and limestone o . 0-iC .o • Q -c -o .c • o. o-o •O'D •O o.o 'O -C - C. -0 'Ciji. o. o' -o •O 'C -o fragment bearing sedarenite 3B ' o_,9>-= • d, --0 '.o .'o .o. 0 «.'o .0 'o-°::=^' '• a_z o • o St 3B. Tan fine sandstone: Calcfte cemented mature CO . £•• o. c. -o micaceous sublitharenite. • o .'c .0. Q-e. Q p -e-^. c •o'^-^o O.C'O :C. 0_'0 -C-O'C. o • f' • o 9o .'^•c; •-o-^ •o -o-o-I . o> 0.0 -O -C ."TJ" -o -o .o- o- o 'O, c? - .(^Jj'c . = -0'. *=-0'0 .'c -2-0^' O . O 'O -O • Q 'O -o -o- o. • o •? o St 2C. Tan Leisgang banded very fine sandstone: calcite cemented mature micaceous sublitharenite. ••<^~~i::' Sr >^~-,i' .^fS'V 26. Brown sandy granule conglomerate: Calcite 2B cemented submature, caliche and chert bearing 81 sublitharenite •.-^' • • '^$3>"' .^^:=-" 2A. Reddish brown fine sandstone: Hematite 2A cemented submature micaceous sublitharenite O- 0-0 -o-o-O. o-o -O 'O' 0'( • Q'. "-C • O .'o •C'- C ^•. O -° 'O • <^ : .< Gh 1A. Reddish brown sandy pebble conglomerate: Calcite cemented submature chertarenite Permian: Reddish siltstone vffth light gray mottled texture and contorted horizontal stratification Figure A.2. Illustration of measured section Tr-IA. 104 Section Tr-1 B 9. Reddish brown pebble conglomerate: Hematite cemented submature chertarenite Gm 8. Reddish brown pebble conglomerate: Hematite cemented submature chertarenite 7. Brown medium sandstone: Umonite cemented supermature chert sublitharenite 6. Reddish brown sandy pebble conglomerate: Gypsum cemented submature shale fragment sedarenite 5. Tan fine sandstone: Kaolinite/Hematite cemented supermature meta fi^gment • O O o—£^0'. °-0'C ."o .o, „ . c . c -o • o • o -o -o . o - c" o 4. Reddish Brown sandy pebble conglomerate: O V o o . O'o o- o.C-O" • o .. ^-O-c -oO -o."r .- o.0 •. O'O.o. "o Hematite cemented submature chertarenite o .?^o O^o'. o.o • O .', St 3. Tan to Brown pebbly fine sandstone: Kaolinite cemented supermature micaceous subliHiarenite 00 0° 00000 ooooooooooco o Gm 2 Reddish brown pebble conglomerate: Hematite oOoOo°cOcOo<^C^'0<' o ooooooooooco o.o cemented submature chertarenite 0 oO - - - - 1. Brown Pebble conglomerate: Gypsum cemented Gm subrtiature chertarenite Permian: Reddish siltstone with light gray mottled texture and contorted horizontal stratification Figure A.3. Illusti-ation of measured section Tr-1 B 105 Section Tr-IC o . o o . C^— . o • —^o -o o. o>-<5 -6 ^— Gh St •o. ' o p- • .o .•-'. O'O. o o -f^, o' . y, q --0 -o^.o.pr- o -b -^o -o r, .< Gm •Q O'o .0.0, . °-O'0 ."o .o. b-o.'o .C'Q: ^' SI 0.0 'O -O- O'O .o-o-o. O -O -o 'Oo'o'^ -o O'o .0-C-. ^-O'O ."o .o. o'O-o .O'cio.' ••.'o Gm 0.0 -O -O. O -O -O-O-O. O -O -o' O- -o' • .O O'o .O.Q'. 'O-O'O .'o .o. ojo^co,- f^ • — \---"'«° •%•.'«•• •<>''•" -'o ''^ S . •• o- i .o"-'" "-^ °- '^' •^-' ! => '-=• V c ^ i - t = r, °t> '^' "^ .. t.^'c ^ p . o c «,C' c c. i c-t A c- * .0 .--o-o-c'o.o.&-e -o-oo-Q-o'c^c. O.O'C-O-Q -o-o-o-o. o-o -o 'O.Q 'C Gm -O 0"o .O.Q'. O.Q.O .'Q .O. C^^-O .°'O' °.' 'O^ °! SI Gm O ' O ' o - o • o c 0. 0 o- o Figure A.4. Illusti-ation of measured section Tr-1 C. 106 Section Tr-ID b S .- •o'.-c-'g. C o°'^^0 0 . o^—ro . , 'c . O ' 'jO' • A 'O * ^ - . O. . -o - -O'O .Q .c.Q-o.^^C'Q • oo , o -o o - o. -r. - c • q -o -o-o- o. c - o -1-1 -o o o .°'o', 0.0-0 b -o. o<^.o .o-o o; .o o'o_o. 0-0 'O - o - CL -O ^0, .Q^O. p. .o-o • r. O . b -O . • o o'o_o^c-, •O .c . O .'-' 'o o' -o 9 o .^• o • O'O . o - c -o -o-o- o. o -o -o • b o . o -o • •C'O .'o .0. ^-,-0•"r^ .O 'n'. Gh O -O -O .Q. O. 0-0-0 o' . o 9 'o—^• °-o-o -"o'^^^o-o-c .o-o. ' b c . o-o - • oo . c -o - O ' - o o 'o . o - - b o • 0-0 - 0- .0 9 0.°' o> .'O- . .o-. 0. • '... 'Q .0'. '"• .'O' 'o.' •'. . 'Q'. • , •0 -o . o -o -q -o- o. o. -o -c, • o ' 'o • 'o o -o' o • o . 0 . o . C'O .o -C- o b -o ' 6 "O -o 'O o -o -o-o. o .0 -Q: o; o _,o 'O • •c-o-o-o-c-o-o-o-o b -O-O'O-- o-' o -B 'O'.o-.c-.o Gm 5 •°- o'. ^-o'O .'o .0. o'O.'.^ .o -o-' o; Oo-Oo-Oc- •c-o-c-c-o-o-o. o-o -0 -o-.. O .°-b. ^-O'O .b -O. o'O-'o .O'O-' o.'o ?o °o ? . C/-—\- o - ,—s> -o /—^p. o — o :r^ \. -o. Figure A.5. Illustration of measured section Tr-ID. 107 Section Tr-2 10. Gravel Float: Triassic indicated by presence of coarse pebbles in float 9. Red fine sandstone: Kaolinite/Hematite cemented supennature meta fl-agment 8a. Scour Fill: Tan very fine sandstone: Calcite cemented supermature meta fi^g sublitharenite 8. Red fine sandstone: kaolinite/Hematite cemented submature meta fragment sublitharenite 7c. Laminated tan -^rery fine sandstone: Kaolinite cemented supermature meta fragment subarkose 7b. Sand Pod: Gray very fine sandstone: Calcite cemented mature meta fragment sublitharenite 7a. Tan very fine sandstone: calcite cemented mature micaceous meta fragment sublitharenite 7. Gray very fine sandstone: Kaolinite/Hematite cemented mature meta fragment sublitharenite 6a. Sand Lens: Tan very fine sandstone: calcite cemented supermature meta frag sublitharentie 6. VVfe-y/y horiz. stratified gray very fine sandstone: Calcite cemented supermature meta fragment sublitharenite with red mud clasts 5, Laminated to low angle trough cross stratified red very fine sandstone: Kaolinite cemented supennature meta fragment sublitharenite 4. Tan Leisgang ttanded very fine sandstone: Calcite cemented supennature meta fragment sublitharenite 3. Tan Leisgang banded very fine sandstone: Kaolinite cemented mature meta fragment sublitharenite 2. Reddish to gray fine sandstone: Kaolinite/hemafrte cemented mature meta fragment bearing sublitharenite 1. Gray pebbly fine sandstone: Calcite cemented submature chert limestone fragment bearing sedarenite Figure A.6. Illustration of measured section Tr-2. 108 Section Tr-3 -•O • O • O -'O • O • o - O. O To -O'O 6b. Reddish brown sandy pebble conglomerate: Silica cemented submature ctiertaren'ite <°\^-y-o^-°Jc^-^-^c 4. Grayish tan pebbly fine sandstone: Kaolinite cemented submature chert sublitharenite . c - Sh 3. Grayish tan slightly pebbly fine sandstone: Calcite cemented supermature chert sublitharenite St 2 Tan medium sandstone: Kaolinite/Hematite cemented supennature quartzarenite o.o -O -0 . o -o -c -c, ' c . b '-' • - b c D ."^ 'O • o.'o ' -o.o • • ro i'p •°-<^ •.^•C'_ C _.' o .0 o 'O-.O?„'.00 o.o '0-0 • ' Figure A.7. Illustration of measured section Tr-3. 109 Section Tr-4 Gm 9. Dark brown sandy pebble conglomerate: Calcite ,-0 -O • Q. -O -O .0-0. 0.0 • o ."^-b. '-'-o-o .'o .0. cO.'c p. cemented submature chert bearing sublitharenite o^o- p -o -o-o-o- o -o .0.-' "c,• O 'o .'o .O. o'O.'o -O = 2ft. • b • • rP- - o. 8a •^' . o-^ - oV • o 8a. Brown medium sandstone: Kaolinite cemented -T-fc. St/Gt --0. o". supermature chert bearing subiStiaren'te '. 9V --0. -T-'o. b.-' •. • o; • ' 0- - -"o- 8 • ._• 'c- St 8. Lens: Brown medium sandstone: Kaolinite ' . 'O' cemented supermature chert bearing sublitharenite 7a •^-^^• 7a. Gray medium sandstone: Kaolinite cemented supermature chert bearing sublitharenite -'O. •--^-k- •fo. '• c. • o- St/Gt O- .0. -O- -O -O- -O' c - oV=-^o .o^-=-b . d~-=t-fo a 7. Gray sandy pebble conglomerate: Kaolinite 7 C-O.O.O-C-O-O O-O-O-O'O o'-^--b • - o'-=r'o o'~-^-^c . o^-^ cemeried submature chert bearing sublitharenite 0-0. •••-O-O-O -O O-0-O-O-O' 6a o . o V^o - o ^•—^ . &~^o .o St 6a. Tan fine sandstone: Kaolinite cemented supermature meta Augment sublitharenite St 6. Gray fine sandstone: Kaolinite cemented supermature meta fragment sublitharenite 5. Brown granular coarse sandstone: Calcite 5 St cemented submature chert bearing sublitharenfte • C_' -O- . • .0-. •- o." 4a • o _-'o' . ° • 4a. Lens: Brown sandy granule conglomerate: >M>'. •Q- -'o. • Calcite cemented submature chert bearing •lb r-fo. .. O'^ -'o. • sublitharenite • 'b •b- . oV •>?r6-. •'c- '6. • 'ir^. ;^, r-b.. St 4. Brown pebbly medium sandstone: Calcite o:' ^-<' . oV • 'o. ' • 'b • o- • - • cemented submature chert bearing sublitharenite . •'-?^. • o." •o- - • • ' . O • O • O O ' O • O - D„ O.o O O-o 0-0.0 3. Tan pebbly coarse sandstone: Calcite cemented o o-o. o-o o o- Gp/Sp .P'O'O'O-O'O-O' submature chert bearing subl'itharen'ite c • P • o - o o ' r- • p 2. Gray fine sandstone: Kaolinite cemented supennature chert m^a fragment sublitharenite Gm 1. Gray sandy pebble conglomerate: Cateite cemented submature c^ert bearing sublitharenite Permian: Reddish siltstone wnth light gray mottled texture and contorted horizontal stratification Figure A.8. Illustration of measured section Tr-4. 110 Section Tr-5 Gm 11. Gravel Float: Triassic indicated by presence of coarse pebbles in float. 10. Yellowish tan fine sandstone: Kaolinite St cemented supermature micaceous sublitharenite 9. Tan Sandy pebble conglomerate: Calcite Gh cemented submature chert bearing sublitharenite St 8. Reddish brown fine sandstone: Kaolinite cemented supermature chert tiearing sublitharenite 7. Tan sandy granule conglomerate: Calcite Gt cemented submature sed fragment sublitharenite St 6. Tan fine sandstone: Kaolinite cemented mature meta fragment sublitharenite 5. Caliche St 4. Tan medium sandstone: Kaolinite cemented mature quartzarenite 3. Yellowish brown sandy granule conglomerate: Gt Calcite cemented submature chert bearing sublitharenite St 2 Yellowish brown slightly granular fine sandstone: Kaolinite cemented supennature quartzarenite o - O . P.'o • 1. Gray sandy pebble conglomerate: Calcite O 0 'o o. :•%.^-^ •--.Q: •<-• .Q L2- ^ o • b -o • o - o -o -o - c. o. -Ji.:©. ^ Gh cemented submature chertarenite oTo -P-o-.^-o.-o • . r; -o. o .0 -c • ° Figure A.9. Illustration of measured section Tr-5. 111 Section Tr-6 Gm Gm St Gh St Gm Figure A. 10. Illustration of measured section Tr-6. 112 APPENDIX B POINT COUNT DATA AND CLASSIFICATION Table B.1. Point count data Sam# QTZ Feld Lith Pore Cement M.St. Qtz IVl Un Qtz Tr 1A-1A 188 1 221 6 84 61 36 1A-2A 297 16 60 67 60 162 85 1A-2B 237 10 178 15 60 82 78 1A-2C 332 17 55 55 41 143 162 1A-3A 263 25 104 45 63 130 50 1A-3B 320 23 40 79 38 175 93 1A-3C 130 11 265 5 89 78 34 1A-4A 277 26 85 98 14 134 88 1A-4B 258 32 73 60 77 137 55 Tr1B-1 108 3 299 17 73 23 40 1B-2 122 0 292 58 28 18 65 1B-3 315 17 40 95 33 122 125 1B-4 178 0 258 37 27 20 10 1B-5 317 18 30 83 52 97 180 1B-6 175 2 207 26 90 25 50 1B-7 372 5 40 78 5 90 245 1B-8 148 0 285 25 42 10 8 1B-9 155 0 297 20 28 2 7 Tr2-1 147 10 238 15 90 60 57 2-2 278 25 53 57 87 80 152 2-3 315 22 60 57 46 78 178 2-4 280 20 72 5 123 87 142 2-5 257 26 82 65 70 75 124 2-6a 269 21 37 3 170 77 155 2-7 265 25 80 68 62 58 162 2-7a 245 25 68 23 139 87 122 2-7b 303 8 47 7 135 67 175 2-7c 302 35 30 55 78 42 202 2-8 297 23 53 71 56 47 213 2-8a 257 13 93 5 132 25 178 2-9 298 8 74 13 107 37 171 Tr3-1 293 0 140 7 60 15 142 3-2 353 7 33 78 29 63 218 3-3 330 16 34 12 108 90 192 3-4 302 18 87 48 45 47 195 3-5 325 18 62 68 27 43 198 3-6a 148 0 290 22 40 18 62 3-6b 158 0 267 13 62 8 42 Tr4-1 328 3 77 14 78 32 131 113 Table B.1. Continued Sam# QTZ Feld Lith Pore Cement M.St. Qtz M Un Qtz 4-2 358 7 48 67 20 83 242 4-3 263 0 144 8 85 45 132 4-4 340 3 87 3 67 52 243 4-4a 298 3 150 1 48 47 193 4-5 267 0 150 15 68 50 107 4-6 356 10 41 78 15 57 247 4-6a 353 18 39 55 35 62 221 4-7 326 5 121 37 11 40 98 4-7a 391 4 42 58 5 66 285 4-8 358 12 65 47 18 58 232 4-8a 361 6 47 74 12 77 236 4-9 324 3 112 13 48 60 154 Tr5-1 92 4 326 22 56 10 48 5-2 388 15 20 67 10 10 270 5-3 231 4 213 48 4 0 64 5-4 407 12 16 57 8 7 304 5-6 350 13 35 89 13 14 225 5-7 215 2 150 4 129 51 83 5-8 376 3 30 79 12 63 156 5-9 186 5 207 3 99 39 80 5-10 331 16 56 72 25 47 181 114 Table B.1 Continued Sam# Poly Qtz K-spar Plag Chert MRF SRF Acc Total Tr 1A-1A 91 0 1 138 0 82 1 410 1A-2A 50 13 3 38 6 2 14 373 1A-2B 77 10 0 127 3 42 6 425 1A-2C 27 15 2 3 32 0 20 404 1A-3A 83 20 5 32 9 60 3 392 1A-3B 52 18 5 22 0 7 11 383 1A-3C 18 8 3 118 0 135 12 406 1A-4A 55 21 5 27 35 13 10 388 1A-4B 66 15 17 2 41 7 23 363 Tr1B-1 45 3 0 249 0 50 0 410 1B-2 39 0 0 292 0 0 0 414 1B-3 68 12 5 13 14 0 13 372 1B-4 148 0 0 258 0 0 0 436 1B-5 40 8 10 12 7 3 8 365 1B-6 100 2 0 85 2 117 3 384 1B-7 37 4 1 33 2 5 0 417 1B-8 130 0 0 230 0 55 0 433 1B-9 146 0 0 282 0 15 0 452 Tr2-1 30 3 7 103 3 112 20 395 2-2 46 18 7 0 38 0 15 356 2-3 59 22 0 12 38 0 10 397 2-4 51 18 2 2 47 0 23 372 2-5 58 26 0 5 64 0 13 365 2-6a 37 20 1 0 30 0 7 327 2-7 45 23 2 5 47 8 20 370 2-7a 36 12 13 7 27 10 24 338 2-7b 61 5 3 7 30 5 5 358 2-7c 58 32 3 2 23 2 3 367 2-8 37 18 5 6 27 12 8 373 2-8a 53 13 0 8 57 7 22 363 2-9 90 8 0 0 66 0 8 380 Tr3-1 136 0 0 132 2 3 3 433 5 393 3-2 72 5 2 28 0 0 29 3 0 2 380 3-3 48 16 0 63 17 0 7 407 3-4 60 18 0 35 20 5 2 405 3-5 84 18 0 283 2 5 0 438 3-6a 68 0 0 265 0 0 2 425 3-6b 108 0 0 32 0 43 2 408 Tr4-1 165 3 0 33 15 0 0 413 4-2 33 7 0 70 0 74 0 407 4-3 86 0 0 53 0 34 0 430 4-4 45 3 0 100 0 48 2 451 4-4a 58 3 0 140 0 10 0 417 4-5 110 0 0 21 17 0 3 407 4-6 52 10 0 115 Table B.1 Continued Sam# Poly Qtz K-spar Plag Chert MRF SRF Acc Total 4-6a 70 17 1 16 16 0 7 410 4-7 188 5 0 111 9 0 1 452 4-7a 40 4 0 26 16 0 0 437 4-8 68 12 0 52 13 0 0 435 4-8a 48 6 0 39 5 2 1 414 4-9 110 3 0 84 7 17 4 439 Tr5-1 34 1 3 322 0 1 3 422 5-2 107 13 2 10 4 2 5 423 5-3 167 4 0 209 0 3 1 448 5-4 96 10 2 7 4 1 4 435 5-6 111 2 11 3 26 5 1 398 5-7 81 0 2 57 9 83 1 367 5-8 157 0 3 7 20 0 3 409 5-9 67 3 2 193 4 9 1 398 5-10 103 9 7 1 40 0 15 403 116 Table B.1 Continued Sam# %QTZ %Feld %Lith Tr 1A-1A 0.46 0.00 0.54 1A-2A 0.80 0.04 0.16 1A-2B 0.56 0.02 0.42 1A-2C 0.82 0.04 0.14 1A-3A 0.67 0.06 0.27 1A-3B 0.84 0.06 0.10 1A-3C 0.32 0.03 0.65 1A-4A 0.71 0.07 0.22 1A-4B 0.71 0.09 0.20 Tr1B-1 0.26 0.01 0.73 1B-2 0.29 0.00 0.71 1B-3 0.85 0.05 0.11 1B-4 0.41 0.00 0.59 1B-5 0.87 0.05 0.08 1B-6 0.46 0.01 0.54 1B-7 0.89 0.01 0.10 1B-8 0.34 0.00 0.66 1B-9 0.34 0.00 0.66 Tr2-1 0.37 0.03 0.60 2-2 0.78 0.07 0.15 2-3 0.79 0.06 0.15 2-4 0.75 0.05 0.19 2-5 0.70 0.07 0.22 2-6a 0.82 0.06 0.11 2-7 0.72 0.07 0.22 2-7a 0.72 0.07 0.20 2-7b 0.85 0.02 0.13 2-70 0.82 0.10 0.08 2-8 0.80 0.06 0.14 2-8a 0.71 0.04 0.26 2-9 0.78 0.02 0.19 Tr3-1 0.68 0.00 0.32 3-2 0.90 0.02 0.08 3-3 0.87 0.04 0.09 3-4 0.74 0.04 0.21 3-5 0.80 0.04 0.15 3-6a 0.34 0.00 0.66 3-6b 0.37 0.00 0.63 Tr4-1 0.80 0.01 0.19 4-2 0.87 0.02 0.12 4-3 0.65 0.00 0.35 4-4 0.79 0.01 0.20 4-4a 0.66 0.01 0.33 4-5 0.64 0.00 0.36 4-6 0.87 0.02 0.10 117 Table B.1 Continued Sam# % QTZ % Feld % Lith 4-6a 0.86 0.04 0.10 4-7 0.72 0.01 0.27 4-7a 0.89 0.01 0.10 4-8 0.82 0.03 0.15 4-8a 0.87 0.01 0.11 4-9 0.74 0.01 0.26 Tr5-1 0.22 0.01 0.77 5-2 0.92 0.04 0.05 5-3 0.52 0.01 0.48 5-4 0.94 0.03 0.04 5-6 0.88 0.03 0.09 5-7 0.59 0.01 0.41 5-8 0.92 0.01 0.07 5-9 0.47 0.01 0.52 5-10 0.82 0.04 0.14 118 Table B.2. Sample classification using Folk's (1968) classification of sandstones. Sam# Classification ^ Tr 1A-1A Sandy Pebble Conglomerate: carbonate cemented submature chertarenite 1A-2A Fine Sandstone: Hematitic submature micaceous sublitharenite 1A-2B Sandy Granule Conglomerate: Carbonate cemented submature, caliche, chert, sublitharenite. 1A-2C Very Fine Sandstone: Carbonate cemented mature micaceous sublitharenite 1A-3A Sandy Pebble Conglomerate: carbonate cemented submature limestone fragment sublitharenite. 1A-3B Fine Sandstone: Carbonate cemented mature micaceous sublitharenite. 1A-3C Sandy Gravel Conglomerate: Carbonate cemented submature limestone fragment, chert sedarenite. 1A-4A Medium Sandstone: Kaolinite cemented, supermature, metamorphic fragment, sublitharenite. 1A-4B Very Fine Sandstone: Kaolinite cemented supermature metamorphic fragment sublitharenite Tr 1B-1 Pebble Conglomerate: Gypsum cemented, submature, chertarenite. 1B-2 Pebble Conglomerate: Hematite cemented, submature, chertarenite. 1B-3 Fine Sandstone: Kaolinite cemented, supermature, micaceous, sublitharenite. 1B-4 Pebble Conglomerate: iron-oxide cemented, submature, chertarenite. 1B-5 Fine Sandstone: Kaolinite/Hematite cemented, supermature, metamorphic fragment, sublitharenite. 1B-6 Pebble Conglomerate: Gypsum cemented, submature, shale fragment, chert, sedarenite. 1B-7 Medium Sandstone: Limonite cemented, supermature, chert, sublitharenite. 1B-8 Pebble Conglomerate: Hematite cemented, submature, chertarenite. 1B-9 Pebble Conglomerate: Hematite cemented, submature, chertarenite. Tr 2-1 Pebbly Fine Sandstone: Carbonate cemented, submature, chert, limestone fragment, sedarenite. 119 Table B.2. Continued -Saml Classification 2-2 Fine Sandstone: Kaolinite/Hematite cemented, mature, metamorphic fragment, sublitharenite. 2-3 Very Fine Sandstone: Kaolinite cemented, mature, metamorphic fragment, sublitharenite. 2-4 Very Fine Sandstone: Carbonate cemented, supermature, metamorphic fragment, sublitharenite. 2-5 Very Fine Sandstone: Kaolinite cemented, supermature, metamorphic fragment, sublitharenite. 2-6a Very Fine Sandstone: Carbonate cemented, supermature, metamorphic fragment, sublitharenite. 2-7 Very Fine Sandstone: Kaolinite/Hematite cemented, mature, metamorphic fragment, sublitharenite. 2-7a Very Fine Sandstone: Carbonate cemented, mature, micaceous, metamorphic fragment, sublitharenite. 2-7b Very Fine Sandstone: Carbonate cemented, mature, micaceous, metamorphic fragment, sublitharenite. 2-7c Very Fine Sandstone: Kaolinite cemented, supermature, metamorphic fragment, subarkose. 2-8 Fine Sandstone: Kaolinite/Hematite cemented, submature, metamorphic fragment, sublitharenite. 2-8a Very Fine Sandstone: Carbonate cemented, supermature, metamorphic fragment, sublitharenite. 2-9 Fine Sandstone: Kaolinite/Hematite cemented, submature, metamorphic fragment, sublitharenite. Tr 3-1 Sandy Pebble Conglomerate: Carbonate cemented submature chert sublitharenite 3-2 Medium Sandstone: Kaolinite/Hematite cemented, supermature, quartzarenite 3-3 Fine Sandstone: Calcite cemented, supermature, chert sublitharenite. 3-4 Pebbly Fine Sandstone: Kaolinite cemented, submature, chert sublitharenite. 3-5 Fine Sandstone: Kaolinite cemented, mature, chert, metamorphic fragment sublitharenite. 3-6a Pebble Conglomerate: Silica cemented, submature, chertarenite. 3-6b Sandy Pebble Conglomerate: Silica cemented, submature, chertarenite. 120 Table B.2. Continued Sam # Classification Tr 4-1 Pebbly Fine Sandstone: Carbonate cemented, submature, chert sublitharenite. 4-2 Fine Sandstone: Kaolinite cemented, supermature, chert, metamorphic fragment, sublitharenite. 4-3 Pebbly Coarse Sandstone: Carbonate cemented, submature, chert, sublitharenite. 4-4 Gravelly Medium Sandstone: Carbonate cemented, submature, chert, sublitharenite. 4-4a Granular Medium to Coarse Sandstone: Carbonate cemented, submature, chert, sublitharenite. 4-5 Granular Coarse Sandstone: Carbonate cemented, submature, chert, sublitharenite. 4-6 Fine Sandstone: Kaolinite cemented, supermature, metamorphic fragment, sublitharenite. 4-6a Fine Sandstone: Kaolinite cemented, supermature, metamorphic fragment, sublitharenite. 4-7 Sandy Pebble Conglomerate: Kaolinite cemented, submature, chert, sublitharenite. 4-7a Medium Sandstone: Kaolinite cemented, supermature, chert, sublitharenite. 4-8 Medium Sandstone: Kaolinite cemented, supermature, chert, sublitharenite. 4-8a Medium Sandstone: Kaolinite cemented, supermature, chert, sublitharenite. 4-9 Sandy Pebble Conglomerate: Carbonate cemented, submature, chert, sublitharenite. Tr 5-1 Sandy Pebble Conglomerate: Calcite cemented, submature, chertarenite. 5-2 Slightly Granular Fine Sandstone: Kaolinite cemented, supermature, quartzarenite. 5-3 Sandy Granule Conglomerate: Calcite cemented, submature, chert, sublitharenite. 5-4 Medium Sandstone: Kaolinite cemented, mature, quartzarenite. ^ . . 5-6 Fine Sandstone: Kaolinite cemented, mature, metamorphic fragment sublitharenite. 5-7 Sandy Granule Conglomerate: Calcite cemented, submature, sedimentary fragment, sublitharenite. 121 Table B.2. Continued. Sam # Classification 5-8 Fine Sandstone: Kaolinite cemented, supermature, metamorphic fragment, quartzarenite. 5-9 Sandy Pebble Conglomerate: Calcite cemented, submature, chert, sublitharenite. 5-10 Fine Sandstone: Kaolinite cemented, supermature, micaceous, sublitharenite. 122 APPENDIX C TERNARY DIAGRAMS Folk's Classification Section Tr 1A Qtz Quartzarenite Subarkosfiv - Sublitharenite • \ i^ / \ ' Lithic Feldspathic \ Litharenite \ ri Arkose Litharenite Feldspar Lithic Figure C.I. Ternary diagram illustrating classification of section Tr-IA sediments using Folk's (1968) classification. 123 Folk's Classification Section Tr 1B Qtz 'Quartzarenite Subarkosi Sublitharenite Feldspar Lithic Figure C.2. Ternary diagram illustrating classification of section Tr-IB sediments using Folk's (1968) classification. 124 Folk's Classification Section Tr2 Qtz Quartzarenite Subarkose. Sublitharenite Feldspar Lithic Figure C.3. Ternary diagram illustrating classification of section Tr-2 sediments using Folk's (1968) classification. 125 Folk's Classification Section Tr 3 Subarkose Sublitharenite Feldspar Lithic Figure C.4. Ternary diagram illustrating classification of section Tr-3 sediments using Folk's (1968) classification. 126 Folk's Classification Section Tr 4 Qtz - Quartzarenite Subarkosi Sublitharenite Feldspar Lithic Figure C.5. Ternary diagram illustrating classification of section Tr-4 sediments using Folk's (1968) classification. 127 Folk's Classification Section Tr 5 Qtz -Quartzarenite Subarkose Sublitharenite Feldspar Lithic Figure C.6. Ternary diagram illustrating classification of section Tr-5 sediments using Folk's (1968) classification. 128 APPENDIX D PALEOCURRENT DATA Table D. 1. Paleocurrent calculations for section Tr-1. Paleocurrent data for Section Tr-1 Readings taken from trough and planar erossbeds (Planar values in bold text) Degrees=Paleocurrent Reading Radians=Paleocurrent Reading in Radians (Degrees/57.3) Vmean=Vector Mean Vmean={ARCTAN[SUM(SIN)/SUM(COS)]}*57.3 R=Vector Magnitude R=[SUM(SIN)^2+SUM(COS)'^2]'^0.5 L=Consistency Ratio L=(R/No. of Readings)*100 Degrees Radians SIN COS Vmean 140 2.443281 0.642925 -0.765929 -9.701531 38.1068 92.94343 165 2.879581 0.259024 -0.965871 -9.701531 158 2.757417 0.374795 -0.927108 -9.701531 165 2.879581 0.259024 -0.965871 -9.701531 195 3.403141 -0.258577 -0.965991 -9.701531 162 2.827225 0.309215 -0.950992 -9.701531 175 3.054101 0.087380 -0.996175 -9.701531 200 3.490401 -0.341779 -0.939781 -9.701531 148 2.582897 0.530081 -0.847947 -9.701531 203 3.542757 -0.390491 -0.920607 -9.701531 183 3.193717 -0.052101 -0.998642 -9.701531 158 2.757417 0.374795 -0.927108 -9.701531 178 3.106457 0.035128 -0.999383 -9.701531 177 3.089005 0.052563 -0.998618 -9.701531 166 2.897033 0.242129 -0.970244 -9.701531 182 3.176265 -0.034666 -0.999399 -9.701531 169 2.949389 0.191022 -0.981586 -9.701531 152 2.652705 0.469644 -0.882856 -9.701531 137 2.390925 0.682127 -0.731234 -9.701531 154 2.687609 0.438549 -0.898707 -9.701531 184 3.211169 -0.069521 -0.997581 -9.701531 133 2.321117 0.731470 -0.681873 -9.701531 144 2.513089 0.587935 -0.808908 -9.701531 159 2.774869 0.358559 -0.933507 -9.701531 170 2.966841 0.173863 -0.984770 -9.701531 173 3.019197 0.122090 -0.992519 -9.701531 160 2.792321 0.342213 -0.939622 -9.701531 183 3.193717 -0.052101 -0.998642 -9.701531 185 3.228621 -0.086919 -0.996215 -9.701531 187 3.263525 -0.121631 -0.992575 -9.701531 129 Table D.I. Continued Degrees Radians SIN COS Vmean 201 3.507853 •0.358127 -0.933673 -9.701531 140 2.443281 0.642925 -0.765929 -9.701531 165 2.879581 0.259024 •0.965871 -9.701531 158 2.757417 0.374795 -0.927108 -9.701531 165 2.879581 0.259024 -0.965871 -9.701531 195 3.403141 •0.258577 -0.965991 -9.701531 162 2.827225 0.309215 -0.950992 -9.701531 175 3.054101 0.087380 -0.996175 -9.701531 200 3.490401 •0.341779 -0.939781 -9.701531 148 2.582897 0.530081 -0.847947 -9.701531 250 4.363002 -0.939583 -0.342322 -9.701531 SUM 6.421127 •37.561918 130 Section Tr-1 Vector Mean=169" Circular Variance^O.O? Circular Std. Dev.=22° N=41 Figure D. 1. Paleocun-ent rose diagram for section Tr-1. 131 Table D.2. Paleocurrent calculations for section Tr-2. Paleocurrent Data for Section Tr-2 Degrees=Paleocurrent Reading Radians=Paleocurrent Reading in Radians (Degrees/57.3) Vmean=Vector Mean Vmean={ARCTAN[SUM(SIN)/SUM(COS)]}*57.3 R=Vector Magnitude R=[SUM(SIN)'^2-^SUM(COS)^2]'^0.5 L=Consistency Ratio L=(R/No. of Readings)*100 Degrees Radians SIN cos Vmean 216 3.769634 -0.587561 -0.809180 42.88422 24.98295 96.08826 232 4.048866 -0.787827 -0.615896 42.88422 216 3.769634 -0.587561 -0.809180 42.88422 250 4.363002 -0.939583 -0.342322 42.88422 213 3.717277 -0.544409 -0.838820 42.88422 233 4.066318 -0.798455 -0.602054 42.88422 224 3.90925 -0.694451 -0.719540 42.88422 216 3.769634 -0.587561 -0.809180 42.88422 220 3.839442 -0.642571 -0.766226 42.88422 190 3.315881 -0.173408 -0.984850 42.88422 195 3.403141 -0.258577 -0.965991 42.88422 233 4.066318 -0.798455 -0.602054 42.88422 217 3.787086 -0.601592 -0.798803 42.88422 233 4.066318 -0.798455 -0.602054 42.88422 206 3.595113 -0.438133 -0.898910 42.88422 213 3.717277 -0.544409 -0.838820 42.88422 245 4.275742 -0.906175 -0.422904 42.88422 218 3.804538 -0.615441 -0.788183 42.88422 220 3.839442 -0.642571 -0.766226 42.88422 208 3.630017 -0.469235 -0.883073 42.88422 255 4.450262 -0.965841 -0.259136 42.88422 -0.906175 -0.422904 245 4.275742 42.88422 -0.865871 -0.500267 240 4.188482 42.88422 -0.544409 -0.838820 213 3.717277 42.88422 -0.453753 -0.891127 207 3.612565 42.88422 -0.847886 -0.530179 238 4.153578 42.88422 -17.000365 -18.306700 SUM 132 Section Tr-2 :jtn , yn , ]f\ in . yn . :jin % % Vector Mean=223° Circular \^riance=0.04 Circular Std. Dev.=16° N=26 Figure D.2. Paleocun-ent rose diagram for section Tr-2. 133 Table D.3. Paleocurrent calculations for section Tr-4. Paleocurrent Data for Section Tr-4 Degrees=Paleocurrent Reading Radians=Paleocurrent Reading in Radians (Degrees/57.3) Vmean=Vector Mean Vmean={ARCTAN[SUM(SlN)/SUM(C0S)]}*57.3 R=Vector Magnitude R=[SUM(SIN)'^2•^SUM(COS)'^2^0.5 L=Consistency Ratio L=(R/No. of Readings)*100 Degrees Radians SIN COS Vmean R 35 0.61082 0.573540 0.819178 19.10471 47.3691 89.37567 42 0.732984 0.669090 0.743181 19.10471 20 0.34904 0.341996 0.939701 19.10471 30 0.52356 0.499967 0.866045 19.10471 33 0.575916 0.544603 0.838694 19.10471 32 0.558464 0.529884 0.848070 19.10471 41 0.715532 0.656019 0.754744 19.10471 21 0.366492 0.358343 0.933590 19.10471 38 0.663176 0.615623 0.788041 19.10471 30 0.52356 0.499967 0.866045 19.10471 353 6.160558 -0.122320 0.992491 19.10471 350 6.108202 -0.174091 0.984730 19.10471 27 0.471204 0.453960 0.891022 19.10471 20 0.34904 0.341996 0.939701 19.10471 22 0.383944 0.374580 0.927194 19.10471 28 0.488656 0.469440 0.882964 19.10471 25 0.4363 0.422589 0.906321 19.10471 50 0.8726 0.766003 0.642837 19.10471 24 0.418848 0.406708 0.913558 19.10471 42 0.732984 0.669090 0.743181 19.10471 0.000000 0 0 1.000000 19.10471 0.087149 5 0.08726 0.996195 19.10471 0.499967 30 0.52356 0.866045 19.10471 0.087149 5 0.08726 0.996195 19.10471 0.358343 21 0.366492 0.933590 19.10471 0.438341 26 0.453752 0.898809 19.10471 0.374580 22 0.383944 0.927194 19.10471 0.087149 5 0.08726 0.996195 19.10471 0.766003 0.8726 0.642837 19.10471 50 0.573540 0.61082 0.819178 19.10471 35 -0.087610 0.996155 19.10471 355 6.195462 0.544603 0.838694 19.10471 33 0.575916 0.358343 0.933590 19.10471 21 0.366492 -0.191249 0.981541 19.10471 349 6.09075 -0.070213 0.997532 19.10471 356 6.212914 -0.052794 0.998605 19.10471 357 6.230366 -0.139621 352 6.143106 0.990205 19.10471 134 Table D.3. Continued Degrees Radians SIN cos Vmean 23 0.401396 0.390704 0.920516 19.10471 10 0.17452 0.173636 0.984810 19.10471 40 0.69808 0.642748 0.766077 19.10471 357 6.230366 -0.052794 0.998605 19.10471 20 0.34904 0.341996 0.939701 19.10471 3 0.052356 0.052332 0.998630 19.10471 356 6.212914 -0.070213 0.997532 19.10471 4 0.069808 0.069751 0.997564 19.10471 7 0.122164 0.121860 0.992547 19.10471 18 0.314136 0.308995 0.951064 19.10471 355 6.195462 -0.087610 0.996155 19.10471 27 0.471204 0.453960 0.891022 19.10471 350 6.108202 -0.174091 0.984730 19.10471 340 5.933682 -0.342431 0.939543 19.10471 150 2.617801 0.500167 -0.865929 19.10471 140 2.443281 0.642925 -0.765929 19.10471 SUM 15.502602 44.760489 135 Section Tr-4 Vector Mean=16** Circular \^riance=0.06 Circular Std. Dev.=20° N=53 Figure D.3. Paleocun-ent rose diagram for section Tr-4. 136 Table D.4. Paleocurrent calculations for section Tr-5. Paleocurrent data for Section Tr-5 Degrees=Paleocurrent Reading Radians=Paleocurrent Reading in Radians (Degrees/57.3) Vmean=Vector Mean Vmean={ARCTAN[SUM(SIN)/SUM(COS)]}*57.3 R=Vector Magnitude R=[SUM(S1N)^2•^SUM(COS)''2^0.5 L=Consistency Ratio L=(R/No. of Readings)*100 Degrees Radians SIN COS Vmean 285 4.973822 -0.966021 0.258465 -28.04529 42.92489 91.32955 300 5.235602 -0.866218 0.499666 -28.04529 290 5.061082 -0.939820 0.341670 -28.04529 355 6.195462 -0.087610 0.996155 -28.04529 340 5.933682 -0.342431 0.939543 -28.04529 325 5.671902 -0.573919 0.818912 -28.04529 355 6.195462 -0.087610 0.996155 -28.04529 345 6.020942 -0.259247 0.965811 -28.04529 330 5.759162 -0.500367 0.865813 -28.04529 345 6.020942 -0.259247 0.965811 -28.04529 320 5.584642 -0.643103 0.765780 -28.04529 350 6.108202 -0.174091 0.984730 -28.04529 340 5.933682 -0.342431 0.939543 -28.04529 325 5.671902 -0.573919 0.818912 -28.04529 325 5.671902 -0.573919 0.818912 -28.04529 355 6.195462 -0.087610 0.996155 -28.04529 315 5.497382 -0.707393 0.706820 -28.04529 350 6.108202 -0.174091 0.984730 -28.04529 5 0.08726 0.087149 0.996195 -28.04529 330 5.759162 -0.500367 0.865813 -28.04529 310 5.410122 -0.766301 0.642482 -28.04529 325 5.671902 -0.573919 0.818912 -28.04529 330 5.759162 -0.500367 0.865813 -28.04529 5 0.08726 0.087149 0.996195 -28.04529 -28.04529 355 6.195462 -0.087610 0.996155 -28.04529 300 5.235602 -0.866218 0.499666 -28.04529 330 5.759162 -0.500367 0.865813 -28.04529 325 5.671902 -0.573919 0.818912 -28.04529 300 5.235602 -0.866218 0.499666 -28.04529 345 6.020942 -0.259247 0.965811 -28.04529 345 6.020942 -0.259247 0.965811 -28.04529 330 5.759162 -0.500367 0.865813 315 5.497382 -0.707393 0.706820 -28.04529 355 6.195462 -0.087610 0.996155 -28.04529 10 0.17452 0.173636 0.984810 -28.04529 350 6.108202 -0.174091 0.984730 -28.04529 330 5.759162 -0.500367 0.865813 -28.04529 137 Table D.4. Continued Degrees Radians SIN COS Vmean 310 5.410122 -0.766301 0.642482 -28.04529 340 5.933682 -0.342431 0.939543 -28.04529 322 5.619546 -0.615988 0.787756 -28.04529 5 0.08726 0.087149 0.996195 -28.04529 334 5.82897 -0.438757 0.898606 -28.04529 326 5.689354 -0.559540 0.828803 -28.04529 309 5.39267 -0.777396 0.629012 -28.04529 290 5.061082 -0.939820 0.341670 -28.04529 343 5.986038 -0.292793 0.956176 -28.04529 SUM -20.180601 37.885212 138 Section Tr-5 \ Vector Mean=333'' Circular Variance=0.07 Circular Std. Dev.=2r N=47 Figure D.4. Paleocurrent rose diagram for section Tr-5. 139 PERMISSION TO COPY In presenting this thesis in partial ftilfillmento f the requirements for a master's degree at Texas Tech University or Texas Tech University Health Sciences Center, I agree that the Library and my major department shall make it freelyavailabl e for research purposes. Permission to copy this thesis for scholarly purposes may be granted by the Director of the Library or my major professor. 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