Lithostratigraphy and depositional environment of the Lincoln Limestone Member of the Greenhorn Limestone (Upper Cretaceous) in Russell County, Kansas, with special reference to the basal beds

Abstract

The Lincoln Limestone Member of the Greenhorn Limestone is an Upper Cretaceous sedimentary rock unit formed during a transgressive phase of the North American Western Interior Seaway. Here, we present the lithologic description of 15 Lincoln Limestone localities in Russell County, Kansas, with a special emphasis on the basal beds which are locally abundant with fish remains. Based on the lithologic data, three sets of lithostratigraphic correlations, that are oriented at different angles from each other, were constructed by using the top of the “X-bentonite” of the underlying Graneros Shale as the stratigraphic datum. Based on the data, we recognize one distinct rock unit and 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 marker zone, (2) lower bentonitic marker zone, (3) limestone marker bed, (4) upper bentonitic marker zone, and (5) upper limestone marker zone. Whereas the basal calcarenite of the Lincoln Limestone reflects calcarenite wedging, this lithologic sequence indicates that the Lincoln Limestone in the region is represented successively by shoreface deposits, transition slope deposits, and offshore deposits, indicating a continuous shift in the environmental setting through its depositional history in the area.