THE ALLUVIAL DEPOSITS OF LOWER WAHWEAP CREEK: LINKING CLIMATE AND INCISION RECORDS IN THE CENTRAL COLORADO PLATEAU
Field mapping and stratigraphic descriptions have identified five alluvial terraces (Qat1-Qat5) deposited in the last ~0.5 Mya. Major periods of aggradation occurred at >250 ka (age control to be determined), 160-130 ka, ~100 ka, 60- 40 ka, and 20-10 ka. The megafauna-bearing fine-grained alluvial facies of the fourth-highest terrace on-laps and fills paleo-bedrock channels and topography, suggesting at least 30-50m of aggradation during MIS 6. The terrace chronology along Wahweap Creek is similar to the terrace record of the Paria and Colorado Rivers downstream at Lee’s Ferry. Linkages to regional fluvial records and spring deposits of the Las Vegas Formation suggest the Wahweap alluvial deposits coincide with regionally wetter periods and rates of incision are linked to base-level fall along the Colorado River.