Region: Northern Midcontinent Sioux Arch Province This description of the Sioux Arch Province is from the U. S. Geological Survey 1995 National Assessment of United States Oil and Gas Resources (available on CD-ROM from the U.S.G.S. as Digital Data Series DDS-30, Release 2).

Sioux Arch Province

Introduction

The Sioux Arch Province is located in southeastern South Dakota adjoining the Williston Basin on the north and west, and the Denver and Salina Basins on the south in Colorado and Nebraska

Paleozoic sedimentary rocks, which contain important reservoir and source rock facies in the Williston Basin, are truncated by the sub- Cretaceous unconformity in the western part of the Sioux Arch Province. Cretaceous rocks rest on Precambrian in the eastern part of the province. Two tectonic subdivisions are recognized, from east to west: The Sioux Arch proper or Sioux Ridge, and the Kennedy Basin. Each subdivision is characterized by different structural styles and by different Precambrian basement rocks. The Sioux Ridge is a broadly positive feature underlain by the Proterozoic Sioux Quartzite; the Kennedy Basin is a slight downwarp lying west of the main arch and probably underlain by granite and gneiss. A northwesterly-projecting tectonic trend, the Pierre Arch, more or less separates the Kennedy Basin from the main uplift to the east. Two hypothetical plays are recognized in the province. The one, Truncated Paleozoic Play, is a hypothetical conventional play in truncated Paleozoic rocks that thin eastward and pinch out around the Sioux Ridge and Pierre Arch paleotectonic trends. The other, the unconventional continuous-type Southern Williston Basin Margin-Niobrara Shallow Biogenic Play is described under the Williston Basin Province and defined by the potential for shallow biogenic gas in Cretaceous rocks present in the Williston Basin, the Sioux Ridge area, the Pierre Arch, and the Kennedy Basin.

Acknowledgments

G.W. Shurr of St. Cloud State University, St. Cloud, Minn., provided helpful information and discussions for this study. Scientists affiliated with the American Association of Petroleum Geologists and from various State geological surveys contributed significantly to play concepts and definitions. Their contributions are gratefully acknowledged.

References

Downey, J.S., 1984, Geohydrology of the Madison and associated aquifers in parts of Montana, North Dakota, South Dakota, and Wyoming: U.S. Geological Survey Professional Paper 1273-G, p. G1-G47.

MacCary, L.M., 1981, Apparent water resistivity, porosity and ground- water temperature of the Madison Limestone and underlying rocks in parts of Montana, Nebraska, North Dakota, South Dakota, and Wyoming: U.S. Geological Survey Open-File Report 81-629, 36 p.

Peterson, J.A., 1987, Subsurface stratigraphy and depositional history of type Madison Group (Mississippian), U.S. portion of Williston basin and adjacent area, in Peterson, J.A., Longman, M.W., Anderson, S.B., Pilatzke, R.H., and Kent, D.M., eds., Williston basin--Anatomy of a cratonic oil province: Rocky Mountain Association of Geologists, p. 171-191.

Peterson, J.A., 1987, Geologic summary and hydrocarbon plays, Williston basin, Montana, North and South Dakota, and Sioux Arch, South Dakota and Nebraska, U.S.: U.S. Geological Survey, Open-File Report 87-450-N, 43p.