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D. S. Collins

Publications and source records attributed to D. S. Collins.

14 recordsLinked to original sources
USGS1988

Seismic-reflection technique used to verify shallow rebound fracture zones in the Pierre Shale of South Dakota

Shallow seismic-reflection data are presented to demonstrate their usefulness for locating and showing the continuity and lateral extent of rebound fracture zones in the Pierre Shale. Rebound fracture zones, identified in boreholes near Hayes, South Dakota, have variable depth, thickness, and character, thus making questionable the correlation of these zones between holes. Thus, the subsequent determination of dip and of continuity of the zones is somewhat tenuous, especially if the fracture characteristics change significantly between holes. Once rebound fracture zones have been identified and located by borehole geotechnical and geologic data, seismic profiles can reveal the extent and geometry of fractures in these zones, thus providing valuable preconstruction information without the cost of additional drilling.-Authors

South Dakota↗
USGS1987

A preliminary report on the bentonite beds of the lower Virgin Creek Member of the Pierre Shale, Stanley County, South Dakota ( USA).

The Virgin Creek Member of the Pierre Shales has been divided by earlier workers into lower and upper zones based on weathering and shale differences. Of the 49 bentonite beds of the lower Virgin Creek, the Government Draw Bentonite Beds, and bentonite bed 20 are the best markers for correlation from stream valley to stream valley. The variation of number and thickness of shale and bentonite beds is due to bioturbation, current activity, differential compaction, basin subsidence, and merging and splitting of bentonite beds. Three distinctive concretion horizons have the potential of also being used as stratigraphic markers within the study area. They include a nodule zone between two bentonite beds, barite(?) concretions that locally mark the lower contact of the Virgin Crrek, and a set of concretions at the contact between the upper and lower Virgin Creek. -from Author

Mountain Geologist↗
USGS1987

Comparing geotechnical to geologic estimates for past overburden in the Pierre-Hayes, South Dakota area: an argument for in-situ pressuremeter determination ( USA).

A knowledge of past overburden thickness is useful for designing underground structures such as waste repositories. This study attempts to determine if a correlation can be made between a geologic estimate and two types of geotechnical calculations of past overburden thickness. In the Pierre-Hayes area, Late Cretaceous Pierre Shales is the only bedrock present, but clasts of the Miocene Ogallala Formation were found in the Pleistocene deposits, suggesting that rocks of the Ogallala Formation once covered this area. Based on the geologic estimate, the Ogallala surface was 1100 ft higher than the present surface. Of the two types of geotechnical data acquired for the Hayes site, the laboratory overconsolidation ratios indicate a past overburden thickness value of 2300 ft, whereas the in situ pressuremeter overconsolidation ratios indicate 1318 ft. We, therefore, believe that in situ determination is a better indicator of past overburden that the laboratory results. However, why the two test results differ to this degree is unknown at present.-from Authors

Mountain Geologist↗
USGS1987

Government Draw Bentonite Beds: a newly identified stratigraphic marker in the Virgin Creek Member of the Pierre Shale, central South Dakota ( USA).

A grouping of four bentonite beds, herein named the Government Draw Bentonite Beds, is identified as a stratigraphic marker within the Virgin Creek Member of the Pierre Shale. The beds are found west of Pierre, South Dakota, over an area of at least 130 mi2 (210 km2) where no other markers within the Virgin Creek Member have been identified. In this area, the Government Draw is a potential tool needed to determine the stratigraphic and structural relationships within the upper part of the Pierre Shale, heretofore little known. A better understanding of structural elements found in the Pierre Shale is needed to unravel the Late Cretaceous and younger geologic history of the area. -Authors

Mountain Geologist↗
USGS1982

Diamond collecting in northern Colorado.

The discovery of numerous diamond-bearing kimberlite diatremes in the N Front Range of Colorado and Wyoming is of both scientific and economic interest. Species recovered from heavy-mineral concentrates include Cr-diopside, spinel, Mg-ilmenite, pyrope and diamond. A nodule tentatively identified as a graphite-diamond eclogite was also found. -G.W.R.

Mineralogical Record↗