Introduction

1. A geologic and paleontologic resource inventory for two selected outcrops adjacent to each other in the region of the White Clay Fault on the Pine Ridge Indian Reservation, South Dakota, was begun in the summer of 2012. The selected outcrops are both on the upside of the fault. The southern outcrop is Late Cretaceous Niobrara Formation while the northern outcrop is Eocene-Oligocene White River Group ; a difference of about 50 million years. This resource inventoryrepresents one of a series of steps being taken by students and faculty at Oglala Lakota College to catalogue and preserve the resources of the Pine Ridge Indian Reservation. Per the Sensitivity Criteria developed by LaGarry and Hunt (1992) the Niobrara chalk section should be considered both sensitive and rare as it contains frequent fossils from more than two taxa and grouped fossils. Faulting at the site has exposed fossils from the Cretaceous through the Pleistocene. This is rather unusual and increases the rarity of this location. Even more intriguing, the presence of small Mosasaur, mammoth, Xiphactinus, Brontothereand shark fossils indicates that there may be larger remains buried at these sites that should be salvaged and placed in repository due to their rarity and our responsibility to protect sensitive resources. Most of the fossils are lying on the surface where anyone might pick them up. We might also expect this site to change from year to year and possibly even from season to season due to the extreme weather and frequency of fires in the area. It would be in the best interests of the Oglala Lakota tribe to allow the materials here to be collected and placed in the resource repository at Oglala Lakota College. These fossils tell the story from the time when this area was a vast, shallow, inland sea and the numbers and types of fossils here represent nearly a complete fauna of the Cretaceous Western Interior Seaway. Introduction Geologic Setting The Niobrara Chalk The White River Group is an accumulation of sediments consisting of tuffaceous mudstones and siltstones with lesser amounts of fluvial sandstone, lacustrine limestones and gypsum that formed over parts of South Dakota, Nebraska, and Wyoming. (Darton 1899; Schultz and Stout 1955; Clark and others 1967; Harksen and Macdonald 1969; Swinehart and others,1985). The White River Group consists of the Chamberlain Pass, Chadron and Brule Formations. The Chadron Formation was formed by a fluvial depositional system and consists of overbank sequences topped by pedogenically-modified paleosols. The Chadron Formation contains poorly consolidated conglomerates at its base. The White River Group outcrop selected for this inventory consists of two members of the Chadron Formation: the Peanut Peak Member overlain by the Big Cottonwood Creek Member. A calcrete horizon separates these two members as shown in the photographs below. Tufa and large tufa tubes were found at this site as indicated in the photograph at the bottom left. These may indicate the presence of a hot spring and are often associated with faults. Interestingly, the Eocene-Oligocene White River Group is lower in the landscape than the adjacent Cretaceous Niobrara outcrop. The lowest part of the landscape consists of quaternary alluvial residuum. The White River Group Recommendations for Management Clark, J., J.R. Beerbower, and K.K. Kietzke. "Oligocene Sedimentation, Stratigraphy, Paleoecology, and Paleoclimatology in the Big Badlands of South Dakota." Fieldiana Geology Memoirs 5 (1967). Print. Darton, N.H. “Prelimanary Report on the geology and water resources of Nebraska west of the one hundred and third meridian.” United States Geological Survey Nineteenth Annual Report. (1899): pt 4 719-814. Print. Everhart, M. J., 2001. Revisions to the biostratigraphy of the Mosasauridae (Squamata) in the Smoky Hill Chalk Member of the Niobrara Chalk (Late Cretaceous) of Kansas. Kansas Acad. Sci. Trans 104(1-2):56-75. Harksen, J.C. and MacDonald, J.R. “Type Sections for the Chadron and Brule Formations of the White River Oligocene in the Big Badlands of South Dakota.” South Dakota Geological Survey Report of Investigations 99. (1969). Print. Hattin, Donald E. “Stratigraphy and depositional environment of Smoky Hill Chalk Member, Niobrara Chalk (Upper Cretaceous) of the type area, western Kansas.” Kansas Geological Survey, University of Kansas. (1982). Print LaGarry,H.E. and Hunt, R.M. Jr.. “1992 Paleontological resource survey of the Oglala National Grassland (Sherrill Hills, Story, Story NE, Montrose, Orella, Wolf Butte, Five Points, Roundtop, and Horn 7.5’Quadrangles)”. Larson, Edwin E., and Emmett Evanoff. "Tephrostratigraphy and Source of the Tuffs of the White River Sequence." Geological Society of America Special Paper 325 (1998). Print. Schultz, C.B. and Stout, T.M.”Classification of Oligocene sediments of Nebraska.” Bulletin of the Nebraska State Museum. (1955): v 4 17-52. Print. Swinehart, J.B. , Souders, V.L., Deraw, H.M., and Diffendal, R.F., Jr. “Cenozoic paleography of western Nebraska.” Cenozoic Paleogeography of West-Central United States: Rocky Mountain Paleogeography Symposium 3, Rocky Mountain Section, Society of Economic Paleontologist and Mineralogists. (1985): 209-229. Print. Terry, Jr., Dennis O., and James E. Evans. "Pedogenesis and Paleoclimatic Implications of the Chamberlain Pass Formation, Basal White River Group, Badlands of South Dakota." Palaeogeography, Palaeoclimatology, Palaeoecology 110 (1994): 197-215. Print. Terry, Jr., Dennis O., Hannan E. LaGarry, and W. Brantly Wells. "The White River Group Revisited: Vertebrate Trackways/ Ecosystems, and Lithostratigraphic Revision, Redefinition and Redescription." Geologic Field Trips in Nebraska and Adjacent Parts of Kansas and South Dakota 10th ser. (1995): 43-58. Print. Terry, Jr., Dennis O. "Lithostratigraphic Revision and Correlation of the Lower Part of the White River Group: South Dakota to Nebraska." Geological Society of America Special Paper 325 (1998). Print. Terry, Jr., Dennis O., John A. Chamberlain, Philip W. Stoffer, Paula Messina, and Patricia A. Jannett. "Marine Cretaceous-Tertiary Boundary Section in Southwestern South Dakota." Geology 29.11 (2001): 1055. Print. Acknowledgements I would like to thank the South Dakota Space Grant Consortium, the Louis Stokes All-Nations Minority Participation program, Oglala Lakota College, the Oglala Lakota Tribe, NSF-TCUP and NSF-OSPEEC for making this project possible. Fauna List The Niobrara Chalk formed over the study area 87-82 million years ago when this region was covered by the Western Interior Seaway (Hattin, 1982; Everhart, 2001). Two structural units are recognized: the Fort Hays Limestone Member and the Smoky Hill Chalk Member. The type locality is located in Knox County, Nebraska. The Niobrara Formation underlies the marine Pierre Shale. (Hattin, 1982). The outcrop at the study site consists of the Smoky Hill Member of the Niobrara Chalk unconformably underlying Peanut Peak Member of the Chadron Formation of the White River Group. An erosional unconformity is indicated by the lack of approximately 2200 feet (670 m) of Pierre Shale and Chamberlain Pass Formation of the White River Group. There is evidence of thrust faulting in a portion of the outcrop where approximately one meter of breccia lies between adjacent layers of Niobrara chalk. Numerous fossils were found, particularly in the faulted portion of the outcrop, where non-articulated remains ranging in age from the Cretaceous through the Pleistocene can be found lying together on the surface in talus piles along the base of the outcrop. Lilly Jones, James Sanovia, Hannan LaGarry Department of Math and Science, Oglala Lakota College A Resource Inventory of Selected Sites Adjacent to the White Clay Fault in Southwest South Dakota Works Cited This map is a work in progress of the study area. Areas outlined in orange are Niobrara Formation outcrops. Areas outlined in red are White River Group outcrops. The image area is 12 mi. Cretaceous: Cretoxyrhinamantelli Platyceramusplatinus Volviceramusgrandis Ammonites Enigmatic tubular structures Marine reptile remains (likely Mosasaur or Tylosaurus) Scattered fish remains (scales, vertebrae),including Xiphactinus. Eocene-Oligocene: Brontothere Turtle remains Insect burrows Pleistocene: Mammoth tusks Coprolites with bone fragments Volviceramusgrandis Volviceramusgrandis Xiphactinus Peanut Peak member overlying Niobrara chalk Niobrara chalk outcrop Peanut Peak member, Niobrara chalk, breccia Calcrete horizon Cretoxyrhinamantelli Platyceramusplatinus Erosional pattern of Niobrara chalk Thrust fault in foreground; erosional unconformity in background Ammonite Mosasaur White River Group outcrop Brontothere Fragments of mammoth tusk Talus pile of non-articulated fossils Tufa tubes Exploded skull Talus pile at base of faulted section of Niobrara outcrop Thrust fault consisting of approximately 1 m of breccia