| Geomorphic studies rarely focus on how the interplay of erosive and constructive
processes can change the evolution of a landscape. Reynolds Creek, a 239 km2 watershed, is
used to study the interactions between constructive and erosive processes. The study was
conducted using geomorphic mapping using LiDAR and field observations, geochronology,
and topographic modelling. A lacustrine deposit, the Sedimentary Basin Fill of the Reynolds
Basin area, reveals much of the topographic history of Reynolds Creek. The sediment was
deposited after a rhyolitic flow dammed the watershed 11 Mya, filling the lower basin up with
150 meters of lacustrine and tuffaceous sediment. Dam incision followed fault motions related
to the subsidence and formation of the western Snake River Plain. Breaching of the dam
enabled incision of the basin fill, generating numerous river terraces. Reynolds Creek
topographic evolution shares similarities to other volcanically dammed landscapes, but on a
much larger scale. The disturbance still impacts the channel morphology 11 mya after the
damming.
Keywords: Basins, Geomorphology, Surficial Geology, Topographic Evolution, Volcanic
Damming |