Systematic variation of Late Pleistocene fault scarp height in the Teton Range, Wyoming, USA: Variable fault slip rates or variable landform ages?

Fault scarps of strongly varying height cut glacial and alluvial sequences mantling the faulted front of the Teton Range (western USA). Scarp heights vary from 11.2 to 37.6 m and are systematically higher on geomorphically older landforms. Fault scarps cutting a deglacial surface, known from cosmogenic radionuclide exposure dating to immediately postdate 14.7 ± 1.1 ka, average 12.0 m in height, and yield an average postglacial offset rate of 0.82 ± 0.13 m/k.y. using simple scarp height (average 11.2 m, offset rate 0.76 ± 0.11 m/k.y. using vertical separation). We apply the offset rate to higher fault scarps to develop preliminary age estimates for the geomorphically older landforms, with an initial assumption of constant offset rate through time. The landform age estimates of 16.2 ± 3.9 ka to 45.9 ± 11.0 ka imply that glaciation and alluviation influenced the range front during marine isotope stages 2 and 3. However, fault offset rate variability, suggested by previous work to be attributable to Yellowstone ice cap deglacial processes, suggests that the fault scarp height pattern might also be interpreted as a reflection of strongly variable offset rates in landforms of only slightly contrasting age. These results demonstrate the need for detailed geochronology of isochronous landforms and sediments of multiple ages, in order to understand both faulting and glaciation on faulted range fronts.