A series of regional
cross sections review the Paleocene Fort Union coal stratigraphy in the southern
The Wyodak coal mined at North Antelope in T41N-R70W reaches its
depositional limit to the south in T39N-R71W. In this area, a 30 foot thick coal lies
approximately 1000 feet below the Wyodak coal zone. Moving southwest from T41N-R70W, the
Wyodak ceases to be a single thick coal and becomes a series of thin, laterally
continuous coals.
On the west side of
the project area in T40N-R75W, a series of thin coals between 500 and 700 feet
below the surface correlate northward to the thick Big George coal
interval. They extend southward to
T36N-R75W, where referred to as the School and Badger seams at the Dave Johnson
mine near Glenrock.
The area of T40N-R72W
exhibits an abundance of thin, discontinuous sands. This sand-rich environment correlates
with a Paleocene fluvial system mapped to the north and separates the Big George
to the west from the Wyodak to the east.
Directly to the north of the study detailed cross section work shows that
the Big George lies stratigraphically above the Wyodak.
In the project area
the coal stratigraphy can be summarized from youngest to oldest as follows: Big George (Badger and School) being the
youngest, Wyodak (both 80 ft. single seam in T41N-R70W and equivalent thin coals
southwest of T41N-R70W) of intermediate age, and the 30 ft. seam lying 1000 ft.
below the Wyodak in T39N-R71W being the oldest coal
studied.