AN ARCHITECTURAL ANALYSIS AND DEPOSITIONAL INTERPRETATION OF THE DOCKUM GROUP IN THE WEST TEXAS HIGH PLAINS by Grayson Hayworth Lamb Bachelor of Science, 2017 The University of Arkansas Fayetteville, Arkansas Submitted to the Graduate Faculty of the College of Science and Engineering Texas Christian University in partial fulfillment of the requirements for the degree of Master of Science May 2019 ACKNOWLEDGMENTS This work would not have been possible without the guidance and support provided by Dr. John Holbrook. He inspired me to “shake the bag” and see what falls out. I would like to thank my roommates and fellow geologists, Rodney Stieffel and Ben Ryan for their continuous encouragement, and inquisitive spirits. Thank you to Dr. Richard Denne for helping me keep my main goals in sight and pushing me towards them. Thank you to Dr. Walter Manger who has always been one of my biggest fans and my personal geologic hero. Lastly, a special thank you to my ever loving and caring parents, Mike and Desiree Lamb for being my rock in the ups and downs before, during and after this thesis process. ii TABLE OF CONTENTS ACKNOWLEDGMENTS………………………………………….……………………………. ii TABLE OF CONTENTS………………………….…………………………............................. iii LIST OF FIGURES……………………………………………………………………….............v LIST OF TABLES……………………………………………………………….........................vii CHAPTER 1 INTRODUCTION………………………………………………………….............1 1.1 Dockum Group Exposure…………………………………………………………......2 1.2 Previous Works………………………………………………………………………..5 1.3 Tectonic Depositional Setting………………………......……………………………..6 1.4 Triassic Paleoclimate…….....……………………………………………………........8 1.5 Dockum Group Stratigraphy………………………………………………………....12 1.6 Source Parameters………………………………………………………………........16 CHAPTER 2: METHODS………………………………………………………………….........17 2.1 Field Work……………………………………………………………………...........17 2.2 Photogrammetry………………………………………………………………….......18 2.3 Architectural Analysis……………………………………………………………….20 CHAPTER 3: RESULTS………………………………………………………………………...21 3.1 Measured Sections……………………………………………………………….......21 3.2 Lithofacies…………………………………………………………………………....24 3.3 Lithofacies Assemblages……………………………………………………….........33 3.3.1 Upper Flow Regime Channel Assemblage………………………………………...33 3.3.2 Upper Flow Regime Sheets Assemblage....……………………………………......34 iii 3.3.3 Perennial Channel Assemblage……………………………………………….........34 3.3.4 Floodplain Assemblage……………………………………………………….........36 3.3.5 Paleosol Assemblage…………………………………………………………........36 3.3.6 Lacustrine Assemblage………………………………………………………….....37 3.4 Hierarchy of Surfaces………………………………………………………………..39 CHAPTER 4: DISCUSSION…………………………………………………………….............45 4.1 River channel and flow processes……………………………………………............45 4.1.1 Upper Flow Regime Channels………………………………………………..........45 4.1.2 Upper Flow Regime Sheets …………………………………………………….....52 4.1.3 Perennial Channel Belts and Bars …………………………………………............54 4.2 Depositional Context and paleogeography of the Dockum Group………………......57 4.3 Megamonsoon Climate Hypothesis……………………………………………….....66 CHAPTER 5: CONCLUSIONS…………………………………………………………………72 REFERENCES………………………………………………………………………………......73 VITA ABSTRACT iv LIST OF FIGURES Figure 1: Map of Dockum Group subsurface extent and surface exposure……………………….4 Figure 2: Paleozoic structural highs and lows……………………………………………….…....7 Figure 3: Structural, depositional styles of Dockum Group Sediments and climate patterns.......11 Figure 4: Triassic stratigraphic column for Dockum Basin..……………………………….........13 Figure 5: Map of measured section locations……………………………………………………18 Figure 6: Sparse cloud, point cloud, and orthomosaic…………………………………………...19 Figure 7: Measured section along Palo Duro Canyon road cut………………………………….22 Figure 8: Measured sections throughout the study area……………………………………….....23 Figure 9: Images of lithofacies………………………………………………………………......30 Figure 10: Image of five paleosol types and separating horizons………………………………..37 Figure 11: Detailed architectural analysis of the three channel types…………………………...41 Figure 12: Lithofacies Assemblages along Highway 207……………….………………………43 Figure 13: Lithofacies along Highway 207……………………………………………………...44 Figure 14: Antidunes in upper flow regime channels…………………………………………....48 Figure 15: Chute and Pool structure in upper flow regime channels…………………………….49 Figure 16: Cyclic steps in upper flow regime channels….………………………………………50 Figure 17: Perennial dual flow system...........................................................................................56 Figure 18: Santa Rosa Sandston deposition diagram..………….………………………………..58 Figure 19: Upper flow regime sheets within lacustrine assemblage…...………………………...59 Figure 20: Depositional cartoon of the Tecovas Formation……………………………..………60 Figure 21: Depositional cartoon of the Trujillo Formation……………………………...………62 Figure 22: Cartoon of Cooper Canyon Formation deposition……………………………...……63 v Figure 23: Glacio-fluvial delta depositional process………………………………………….....65 Figure 24: Monsoon circulation diagram…...……………………………………………………67 Figure 25: Megamonsoon circulation pattern……………………………………………………69 vi LIST OF TABLES Table 1: Table of lithofacies and descriptions...............................................................................29 vii CHAPTER 1: INTRODUCTION The Dockum Group of the western Texas High Plains is a relatively understudied basin that has not received an in-depth systematic sedimentological investigation. A comprehensive study of the northern portion of the Dockum Group exposure in the west Texas Panhandle is undertaken in order to better understand its fluvial architecture and depositional environments through time. While the Dockum Group is not a productive petroleum target, its deposition into the Midland Basin drove much of the strata into the oil window (Brown, 2016). Additionally, the basal Dockum has become a target of water resources used in secondary and tertiary petroleum recovery methods. Understanding the depositional styles of the Dockum Group is quintessential to a complete burial history interpretation of the Midland Basin. Furthermore, in terms of producing from the Dockum aquifer, the depositional trends directly relate to porosity, permeability, and water confinement. Accurate interpretations will aid in determining effective reservoir connectivity and drainage methods. Previous studies addressed the Dockum Group from paleontological and stratigraphic perspectives. Paleontology of the Dockum Group and time equivalent Chinle Formation are studied extensively because they are a rich source of Upper Triassic fossil vertebrates (Green, 1954; Chatterjee 1983, 1984, 1985, 1986a, 1991, 1993; Small, 1985, 1989a, b, 1997, 2002; Davidow-Henry, 1987, 1989; Long and Murry, 1995; Simpson, 1998; McQuilkin, 1998; Edler, 1999; Bolt and Chatterjee, 2000; Atanassov 2002; Martz 2002, 2008; Weinbaum, 2002, 2007; Hungerbuhler et al. 2003; Houle and Mueller, 2004; Lehman and Chatterjee, 2005; Lehane, 2006; Mueller and Parker, 2006). However, little has been done recently in terms of the Dockum Group depositional system, and what has been done lacks the details 1 that this study provides. Three depositional models currently attempt to explain the depositional styles of the Dockum Group. McGowen et al. (1983) suggest a large Dockum Lake dominated the depocenter within a complex fluvial, deltaic and lacustrine system. Lehman and Chatterjee (2005) suggest only small ephemeral floodplain lakes existed while prominent deposition was in braided and meandering fluvial systems. Brown (2016) presented a model that combined both theories, suggesting lacustrine systems were understated by Lehman and Chatterjee (2005) and overstated by McGowen et al. (1983). Collectively, these works have interpreted the fluvial systems only as lower flow regime and provided few details as to the climatic mechanisms that would drive the fluvial and lacustrine systems. This study offers a new interpretation for the fluvial lithofacies and a more encompassing paleoclimatic model for the deposition of the Dockum Group fluvial and lacustrine systems. This study does this using detailed outcrop analyses to identify and interpret the individual lithofacies that make up lithofacies assemblages. Depositional patterns unique to lithofacies assemblages in the Dockum Group were used to predict depositional extent of the identified assemblages, and provide paleoclimate interpretations related to the lithofacies assemblages. 1.1 Dockum Group Exposure In both subsurface and outcrop the Dockum Group approximately extends 246,050 km2 (96,000 mi2) into Texas, New Mexico, Colorado, Kansas, and Oklahoma. Its thickness ranges from tens of meters to more than 610 meters (2,000 feet) (McGowen et al., 1983). It crops out nearly continuously around the Caprock Escarpment of the southern High Plains in 2 Texas, along the Canadian River in Texas and New Mexico, and along the Pecos River valley in New Mexico and Texas (Lehman and Chatterjee, 2005). This study focuses on outcrops along the eastern Caprock Escarpment, specifically in Palo Duro Canyon State Park, north and south-facing exposures along the highway TX 207 road cut, and the road cut in Tule Canyon (Figure 1). 3 Figure 1: Regional extent of the Dockum Group across west Texas and eastern New Mexico. The counties outlined in pink are the study area. Generalized locations where the Santa Rosa, Tecovas, Trujillo and Cooper Canyon formations crop out. Blue: Santa Rosa, Red: Tecovas, Yellow: Trujillo, Purple: Cooper Canyon, Green: Dockum