This report is preliminary and has not been reviewed for conformity with the U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Figure 1 shows the route of the field trip. Proceed north on Interstate 25 toward Midwest. The river slices through the western end of Casper Mountain at Bessemer Narrows and then flows eastward across the southernmost Powder River Basin to exit over the Hartville Uplift to the southeast.
Basin forms a natural channel for the regional flow of westerly winds from the Great Basin.
The dune field, with the exception of a few blowouts is now mostly stabilized. Deeply pitted and fluted surfaces on ventifacts are rare here. The best-developed ventifacts seem to be cut on dense, hard rock, especially quartzites. Coarse-grained plutonic rocks show little, if any, ventifact development. Ventifacts developed on carbonates and sandstones are rare on the intensely weathered upper surface of the terrace gravel.