Lithostratigraphy and depositional environment of the LincolnLimestone Member of the Greenhorn Limestone (UpperCretaceous) in Russell County, Kansas, with special reference tothe basal beds

摘要

The Lincoln Limestone Member of the Greenhorn Limestone is an Upper Cretaceoussedimentary rock unit formed during a transgressive phase of the North AmericanWestern Interior Seaway. Here, we present the lithologic description of 15 LincolnLimestone localities in Russell County, Kansas, with a special emphasis on the basalbeds which are locally abundant with fish remains. Based on the lithologic data, threesets of lithostratigraphic correlations, that are oriented at different angles from eachother, were constructed by using the top of the "X-bentonite" of the underlying GranerosShale as the stratigraphic datum. Based on the data, we recognize one distinct rock unitand four clusters of lithostratigraphically distinct and consistent units referred to as"marker zones" in the Lincoln Limestone that are observed widely in Russell County.They are (in ascending order from the base of the member): (1) the calcarenite markerzone, (2) lower bentonitic marker zone, (3) limestone marker bed, (4) upper bentoniticmarker zone, and (5) upper limestone marker zone. Whereas the basal calcarenite of theLincoln Limestone reflects calcarenite wedging, this lithologic sequence indicates thatthe Lincoln Limestone in the region is represented successively by shoreface deposits,transition slope deposits, and offshore deposits, indicating a continuous shift in theenvironmental setting through its depositional history in the area.