thumbnail

Sedimentologic and stratigraphic framework of the upper part of the Fort Union Formation, western Powder River basin, Wyoming

Miscellaneous Field Studies Map 1929

By:
and

Links

Abstract

The purpose of this study is to describe the stratigraphy and interpret the environments of deposition in the upper part of the Paleocene Fort Union Formation. Of all the lithofacies present within the study area, sandstone is the most dominant and makes up most of the upper part of the Fort Union Formation along the western edge of the Powder River basin, Wyoming. This sandstone lithofacies occurs in three forms: 1) pink conglomeratic sandstone, 2) coarse-grained sandstone, and 3) fine-grained sandstone. The pink conglomeratic sandstone lithofacies forms a series of Stacked channel bodies in which the clasts are as much as 1 3/4 in. in diameter. The coarse-grained sandstone lithofacies is laterally equivalent to the pink conglomeratic sandstone sequence, but contains smaller clasts; it is arranged en echelon (offset) to the north. The fine-grained sandstone lithofacies, limited to the northern part of the study area, is not as laterally continuous as the pink conglomeratic sandstone lithofacies to the south. Basal lag conglomerate underlies both the conglomeratic sandstone and coarse-grained sandstone lithofacies, but not the fine-grained sandstone. The presence of a fine-grained sandstone lithofacies lateral to the conglomeratic sandstone and coarse-grained sandstone lithofacies suggests the presence of a coarse-grained braided and meandering fluvial system coeval with a fine-grained meandering fluvial system.. The meandering fluvial systems drained the alluvial plain flanking the Bighorn Mountains on the west and the Casper arch on the southwest, and flowed north-northeastward within the Powder River basin.

Study Area

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Sedimentologic and stratigraphic framework of the upper part of the Fort Union Formation, western Powder River basin, Wyoming
Series title:
Miscellaneous Field Studies Map
Series number:
1929
Year Published:
1987
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Description:
Plate: 52.19 x 38.51 inches
Country:
United States
State:
Wyoming
Scale:
0
Online Only (Y/N):
N
Additional Online Files (Y/N):
N