Aaron Bufe, UCSB graduate student, will give a talk at Speakers Club entitled Erosion of an Active Uplift by Antecedent Rivers.

ABSTRACT:

The formation of strath surfaces (fluvially created, sub-horizontal erosion surfaces) requires that the rate of lateral erosion outpaces the rate of incision of a river. In the foreland of the Tian Shan in northwest China, weakly consolidated Pliocene sand and siltstones are being actively uplifted at rates of 1 – 3 mm/y by a series of detachment anticlines. A number of elevated, several-kilometer-wide planation surfaces bear witness to a history of multiple strath cutting events by braided streams. In contrast, modern rivers incise into the uplifting folds creating 10 – 200 m deep canyons while the up- and downstream alluvial fans remain unincised. What controls whether rivers incise canyons into an uplift or cut wide horizontal platforms? I will share results from a field study and an analogue experiment to 1) test whether existing theories for strath terrace formation can explain the observations in the foreland of the Tian Shan and 2) explore the influence of varying sediment flux and uplift rates on the extent of the beveled area.