Deposition of Crow Creek Member (Pierre Shale, Campanian), southeast South Dakota, and supposed relations to Iowa's Manson Structure
- Iowa Dept. of Natural Resources, Iowa City, IA (United States). Geological Survey Bureau
- South Dakota Geological Survey, Vermillion, SD (United States)
Previous dates from the Manson Impact Structure (MIS) indicated an age near the K-T boundary (65 Ma), but a date of 73.8 Ma was recently reported for a single breccia clast at Manson. The discovery of shock metamorphosed grains in roughly coeval Pierre Shale strata in S. Dak. led Izett et al. to propose that the Crow Creek Mbr contains Manson's distal impact ejecta. They indicated that Manson was covered by a seaway at that time, and postulated effects from an impact-triggered tsunami in the Western Interior. A study of Crow Creek strata from four sites in Yankton Co., S. Dak. was undertaken to evaluate the sedimentary context of the contained impact-derived grains. The sub-Crow Creek unconformity truncates lower Pierre strata eastward across S. Dak. and locally overlies the Niobrara Fm on the sioux Ridge. Probable leaf fossils are seen along this surface at one site. Basal Crow Creek strata reveal evidence of condensed sedimentation coincident with the onset of Bearpaw transgression, particularly occurrences of glauconite, abundant phosphate (pellets, phosphatized matrix, fish bone apatite), and foam-rich lithologies. Basal strata contain detrital grains (15--25% volume) derived from eastern source areas, including quartz, feldspar, and heavy minerals and small clasts of siltstone, mudstone, shale, dolomite, limestone, and quartzite. Floating silt and sand-sized detrital grains persist in the overlying Crow Creek marls, indicating continuing detrital influx. Shock metamorphic planar deformation features (PDFs) are seen in many quartz grains (10-30% in basal unit) and some quartzite and siltstone grains; these are definitive for an impact-derived source. Was the MIS the source of these grains, and does the Crow Creek show evidence of a Manson-triggered tsunami Several obstacles remain and are discussed.
- OSTI ID:
- 6906195
- Report Number(s):
- CONF-9404217-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 26:5; Conference: 27. annual conference of the North-Central Section of the Geological Society of America (GSA), Kalamazoo, MI (United States), 28-29 Apr 1994; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Judith River Formation beneath Fort Peck Indian Reservation - proven high plains gas frontier in northeastern Montana
Petrology and porosity of Devonian Misener formation, West Kremlin field, Garfield County, north-central Oklahoma