Natural Resources, School of

 

Date of this Version

January 1985

Comments

Published by Institute for Tertiary-Quaternary Studies-TER-QUA Symposium Series, 1 : 185-191. Published by the Nebraska Academy of Sciences, 1985. Copyright 1985 R. F. Diffendal, Jr.Used by permission.

Abstract

A series of geologic maps of counties in western Nebraska was prepared for the Nebraska Geological Survey during the mid-1 930s. These maps showed the distribution of rock units of Tertiary age including a formation designated as the “Sidney.” The Sidney Gravel was described as a widespread sheetlike complex of channel deposits, but with small areas where it is not developed. In southern Banner County, Nebraska, there are several channels filled with sand and gravel that were mapped as Sidney in this series. Recently one of these channel fills has been observed to cut across the other. The fills are separated from one another by an opaline silcrete bed. In places these deposits directly overlie beds mapped previously as parts of the younger Kimball formation.

While the local Ogallala lithostratigraphic relationships can be worked out, the exact relationship between the fills in Banner County and the type Sidney could not be precisely determined in the 1930s and cannot be worked out today. The concept of a gravel sheet does not apply to the study area in Banner County.