University of Arkansas, Fayetteville ScholarWorks@UARK Theses and Dissertations 5-2019 Stratigraphy and Depositional Characterization of the Moorefield hS ale (Middle-Late Mississippian) in its Type Area, Northeastern Arkansas (Eastern Arkoma Basin) Griffina W rner Follow this and additional works at: https://scholarworks.uark.edu/etd Part of the Geology Commons, Sedimentology Commons, and the Stratigraphy Commons Stratigraphy and Depositional Characterization of the Moorefield Shale (Middle-Late Mississippian) in its Type Area, Northeastern Arkansas (Eastern Arkoma Basin) A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology by Griffin Warner University of Arkansas Bachelor of Science in Geology, 2017 May 2019 University of Arkansas This thesis is approved for recommendation to the Graduate Council Walter L. Manger, Ph.D. Thesis Advisor T.A. “Mac” McGilvery, Ph.D. Committee Member Glenn Sharman, Ph.D. Committee Member Abstract The Moorefield Shale represents the Meramecian Series in the Eastern Arkoma Basin in northern Arkansas. Lying on the margin of the Mississippi Embayment and Reelfoot Rift, sequence stratigraphic interpretations have labelled the Moorefield Shale a lowstand wedge succeeding the Early Mississippian (Osagean) Boone Limestone conformably and overlain conformably by the Hindsville Limestone/Batesville Sandstone. The unit contains a basal brown- black limestone and succeeding brown-black phosphatic shale. The Moorefield Shale was deposited along the broad, stable cratonic platform on the southern flank of Laurasia, before it’s collision with Gondwanaland to form the supercontinent Pangea at the end of the Paleozoic. During this time, the midcontinent region was covered by shallow seas and carbonates covered most of the region. A shallowly dipping carbonate ramp developed in the region providing a foundation for clastic sediment deposition. The Boone Limestone underlies the Moorefield Shale throughout the eastern Arkoma Region however, the Boone carbonate sediment was transported from its origin on the Burlington Shelf in the northwestern part of Arkansas, and thicknesses of the Boone Limestone significantly decrease to the south and east. Thinning of the Boone Limestone has allowed greater accommodation space for succeeding formations in the eastern Arkoma Basin, and has allowed the Moorefield Shale to be considerably thicker in the east. Thicknesses of the Moorefield Shale measure to approximately 100 feet in outcrop, and 350 feet or greater in the subsurface. Due to the lack of research, the Moorefield Shale offers a unique perspective into the stratigraphy and deposition of Mississippian units of the eastern Arkoma Basin. Acknowledgements Since the Fall of 2013, I have called Fayetteville home, and while I am sad to be leaving, it has been a great starting place for my geological career. I am glad to have spent the last six years here on the hill, and I would not have made it without all of the support and help from friends, professors, and family. To Walt Manger, you have been the war-horse of this study and one hell of an advisor. I was a lost little pup when I first started my masters, but you gave me inspiration and showed enthusiasm throughout this thesis that drove me to get it done. From the first time we sat down together to discuss the Moorefield, I recognized the wealth of knowledge that you bring to the table in almost every geological question that is proposed. It is truly amazing the amount of work that you put in to making sure that all of your students succeed, and a lot can be said about someone who strives daily to inspire young geologic minds. My understanding about geology in general was greatly expanded over the last two years, and I am thankful every day that I had the opportunity to learn from one of the best this department has seen. A great thank you is owed to my committee, Dr. Mac McGilvery and Dr. Glenn Sharman. Mac, you have molded a young geological mind and continually pushed my boundaries in understanding the processes and impacts that geology has on our everyday lives. I have learned a great deal about applying my education to the real world, and I am forever grateful for that. Dr. Sharman, I am truly amazed by the work that you do and your expertise on problems that I have struggled to wrap my mind around. Spending a few weeks in Montana together was the highlight of getting to learn from you and seeing how you take on and solve problems gave me tons of new perspectives on how to go about solving geological problems down the road. To Jamie Woolsey, I cannot thank you enough in helping me get through the grueling process of Petra. My numerous questions about logs and correlations would not have been solved without your help. I loved getting to learn from you and have someone that I could turn to when I hit a wall. To Philip Shelby, the man behind the Boone Shale and early work of the Moorefield Shale. Thank you for sitting down and responding to my countless emails about these units, when I had absolutely no idea what I was getting myself into. Your expertise over these units was a major help in my understanding of this project, and I am thankful to have had you around. My parents, Bob and Betsy, for constantly supporting me through my trials and tribulations of my educational process. Without your love and support all of these years I would not be here today. It has not been a smooth ride to get to this point, but we did it! I will look back on this process for years to come and will always remember the phone calls and texts telling me to keep going, when I thought I wouldn’t make it. A special thank you to my aunt and uncle, Rip and Nancy, for financially helping me get to the point where I am today. In addition to all of the advice given, I owe you guys a great deal in encouraging and supporting me through this process. I could not have done it without you guys. To all the friends that I have made over the years, I am proud to say that I would not be the man I am without you guys. We have been through the thick and thin together, and you guys have always been by my side when I needed it the most. The Beatles said it best, “Oh, I get by with a little help from my friends”. Table of Contents Chapter Page Number Introduction............................................................................................................................ 1 Geologic Setting..................................................................................................................... 4 Previous Investigations.......................................................................................................... 11 Methods................................................................................................................................. 17 Observations.......................................................................................................................... 24 Interpretations........................................................................................................................ 33 Conclusions……………………………………………………………………………........ 57 Future Work…………………………………………………………………………........... 58 References………………………………………………………………………………….. 86 INTRODUCTION The Moorefield Shale is regarded as an understudied stratigraphic formation in the northern Arkansas area. Lying in the far eastern portion of the Arkoma Basin and directly west of the Reelfoot Rift, the Moorefield Shale was deposited as a lowstand wedge conformably on the Boone Shale in the east and grades into the Osagean Boone Limestone further west. The Moorefield Shale is overlain conformably by the Batesville Sandstone/Hindsville Limestone. Only appearing in outcrop and subsurface data in the eastern half of the state, the Moorefield offers an interesting view into the depositional environment and stratigraphic sequence of the eastern Arkoma Basin. The Moorefield Formation is largely calcareous shale, consisting of a brown, almost yellow color, when examining in the field. It is well exposed around Moorefield, Independence County, and in that locality it has a thickness of 50-75 feet (Adams, 1904). Adams (1904) continues to state that the Moorefield Shales arenaceous layers pass gradually into the Batesville Sandstone, and that there appears to be no break in deposition, just a change lithologically in kind of material deposited. The Moorefield Shale represents the transitional interval following the Boone Limestone 3 rd order forced regressive cycle, and the onset of the Upper Mississippian transgressive systems tract. Comprising both a shale and limestone member, the Moorefield reflects an everchanging depositional environment during the Middle-Late Mississippian. Statement of the Problem The Moorefield Shale was originally regarded by early Arkansas geologists as a unit that was associated with the northern Arkansas lead and zinc industrial mineral deposits (Adams, 1904). Simple lithostratigraphic interpretations of the unit were made, but have been changed throughout the years, creating a lack of consistency in the stratigraphic nomenclature. Work done by recent geologists has also created confusion of age assignments for the Meramecian Series, 1 based on ammonoid and conodont fossil assemblages related to the Middle Mississippian time period. Using the Moorefield Shale as an equivalent of the Warsaw Shale in Missouri, Lane and Brenckle (2005), restricted the fossil assemblages of the Moorefield Shale to only two conodont