38 D3. Quaternary Geology, Geomorphology, Paleoclimate, and Limnogeology (Posters)

Wednesday, 27 March 2019
8:30 AM - 11:45 AM
Big Basin/Kaw Nation Rooms

GEOLOGIC CHANGES IN THE WHITE RIVER BADLANDS, SOUTH DAKOTA, AS RECORDED BY THE HISTORICAL PHOTOGRAPHS OF HAROLD ROLLIN WANLESS

Paper number: 38-3
Program: Technical Sessions
Time: 8:30 AM – 11:45 AM

Authors

Abstract

Historical photographs that were taken a century or more ago can be valuable data sources to see erosional, depositional, and vegetation changes in actively eroding landscapes. Harold Rollin Wanless (the father of the second author) took a number of photographs of the White River Badlands of South Dakota while working on his doctoral research between 1920 and 1922. Using these photographs we have relocated many of the sites that Wanless visited and have reimaged the photographs to see what changes have occurred in the landscapes. In many cases the changes have been minor, typically involving only the erosion of ridge-line spires and crests, which is surprising given the active erosion of badland topography. In some cases major changes have occurred in the Badlands involving major collapses of high ridges, major reductions in large isolated peaks, and the growth of active landslides. Some landslides active in the 1920’s are now stabilized on the surface as indicated by the vegetation changes. Canyons photographed by Wanless show deepening of the stream beds, erosion of isolated spires on the sides of the canyon, but relatively little change in the canyon slopes.

Wanless’ photographs indicate that the flat pediment surfaces at the base of the Badlands and drainages were actively eroding a century ago. Now these flats are being buried by sediment coming off the badland slopes. Many drainages at the base of the Badlands that were incised in the Wanless photos are now filled with sediment. Vegetation at the base of the badland slopes has also changed, being dominated by thick grass and scattered shrubs, possibly from the lack of livestock grazing since Badlands National Monument was founded in 1939. The increased vegetation acts as traps for sediment coming off the badlands slopes. Aggradation may also be occurring from episodic droughts in the Twentieth and Twenty-First centuries. These dry conditions may have not allowed sediment to be transported across and though the flats at the base of the badland slopes.

Geological Society of America Abstracts with Programs. Vol. 51, No. 2

doi: 10.1130/abs/2019SC-326838

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