PAST CLIMATE CHANGE RESPONSIBLE FOR ROCK UPLIFT RATE VARIATION ON THE WASATCH FAULT

The Wasatch fault on the eastern edge of the Basin and Range has been the subject of extensive study, owing to it’s variable rock uplift rate history. Both climatic and tectonic mechanisms have been suggested to drive this variation, which has contributed to the wider debate as to the control of climate on tectonics globally. Thermochronology of the Wasatch records variation on the 1-10 Ma timescale, associated with changes to large tectonic structures such as the movement of the structural hinge of the fault, or fault segmentation and linkage. The influence of climate has been inferred on shorter timescales, with changes in slip rate on the Wasatch fault suggested to be caused by glacial loading. To investigate rock uplift rate variation on the Wasatch fault, we examined the river profiles that cross-cut it. Profiles from separate networks along the Wasatch fault that incise different lithologies exhibit sections of alternating low and high channel steepness, which could be explained by changes to rock uplift rate, erodibility or sediment supply. To explain these series of knickpoints, we recovered the rock uplift rate history of the Wasatch fault from the river profiles, calibrated using Apatite (U-Th-Sm)/He data. Results oscillate with the same frequency as the glacial-interglacial cycles of the Pleistocene. We therefore suggest that tectonic variation on the Wasatch is coupled to past climate change.