Teton Fault - New Data
Glenn Thackray, Idaho State University
While there has been no historically recorded earthquake on the Teton Fault, movement on the fault has created Jackson Hole and the Teton Range we see today. But Jackson Hole history is little more than 100 years of time, and geologists know that the Teton Fault is a very active fault. So how might we study its history and predict its future?
Recently acquired radar imagery (LiDAR) shows dramatic fault offsets along the front of the Teton Range as well as the land forms created by multiple episodes of glaciation (e.g. lateral and terminal moraines). Study of the varying fault offsets through these glacial features show that the front of the Teton range has evolved through interactions of Quaternary faulting and glaciation. LiDAR data analysis and improved understanding of regional deglaciation timing allow for accurate determination of fault-offset rates and age estimation for older glacial landforms. Fault scarps that cut approximately 14 thousand year (ka) old deglacial surfaces at the mouths of several canyons average 11.5 m height, yielding a vertical offset rate of 0.82 m/ka. Application of that rate to scarps up to 49 m high, cutting older lateral moraines and alluvial fans, yields landform age estimates of 19 ka (marine isotope stage or MIS 2) to 60 ka (within MIS 4). This study allows us to conclude that thick ice exited the Teton Range canyons and entered the Jackson Hole basin repeatedly during MIS 3 (29-57 ka) and MIS 4 (57-71 ka) and likely extended beyond MIS 2 ice limits. Climatic conditions thus appear to have been more favorable for glacier growth during MIS 3 and 4 than during MIS 2.
Study therefore of the LiDAR data along the front of the Teton Range enables us to quantify movement on the Teton Fault as well as understand better the recent glacial history of the Tetons & this valley.