Numerous valley fault lines identified, examined in new study

JACKSON HOLE, WYO – Even weekend geologists have probably heard of the Teton fault. It’s the most notable fault line in the valley, running along the eastern base of the mountain range of the same name. But there are more places where the earth has buckled before and could again. Many more.

A new report titled, “Preliminary Investigation of Quaternary Faults in Eastern Jackson Hole, Wyoming,” was released early this month by the Wyoming State Geological Survey (WSGS). The paper’s author, Seth J. Wittke, identified three fault systems in addition to the Teton Fault.

Fault lines were analyzed at Antelope Flats, south of Blacktail Butte, and near town in an area called the Flat Creek Fan. Light detecting and ranging (LiDAR) data was used, along with photogrammetric analysis of aerial photography, to better refine prior mapping of these faults. In total, 36 elevation profiles across scarp sections were analyzed.

The primary goal of the study was to evaluate the system of predominately westward-dipping late-Quaternary faults that form a series of short, unconnected segments along the eastern edge of the valley. They are thought to be independent of each other and the Teton Fault, but the study could not make such a claim. In fact, Wittke specifically writes, “they are not confirmed to be independently seismogenic.”

The Antelope Flats section of faults consists of six discontinuous fault sections west of Shadow Mountain. Just south of Blacktail Butte, two more fault lines were examined. The Flat Creek Fan contains a dozen more faults in its system.

In conclusion, the study found faults at Antelope Flats (early-Pinedale-aged alluvial fan) and south of Blacktail Butte (late-Pleistocene to early Holocene) to be in the “hanging wall” of the Teton fault. The Flat Creek faults postdate a fan surface that is possibly late Pleistocene to early Holocene in age. Those faults are potentially in the hanging wall of the East Gros Ventre fault instead of the Teton fault.


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