- GeoRef, Copyright 2008, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
In the northeastern Big Horn Basin, a thin lens of spherulitic limestone occurs locally in a red non-marine shale which is both overlain and underlain by limy sandstone. Calcite spherulites form 85 percent of the rock. The interstitial material is a mature detritus composed chiefly of clays and quartz. The spherulitic limestone is considered to have formed in an alkaline flood-plain lake with little detrital contamination.