Geomorphic and hydrologic implications of the rapid incision of Afton Canyon, Mojave Desert, California

Abstract

Afton Canyon is a >150-m-deep canyon that formed as a result of overflow and drainage of Lake Manix, an ∼215 km2 late Wisconsin pluvial lake in the central Mojave Desert. Because the canyon age is within the range of conventional radiocarbon dating, it is possible to provide a time-based chronology of events and resultant landscape changes due to a >120 m base-level drop. Analysis of erosion volumes upstream of Afton Canyon and a review of public and private well logs downstream of the canyon mouth indicate that late Wisconsin surfaces are deeply buried downstream of Afton Canyon. Burial depths are ∼55 m at the mouth of Afton Canyon, 27 m in the Cronese basin, and 18 m at Crucero. The well logs also indicate that Soda Lake was far more areally extensive prior to late Wisconsin time. Stratigraphic and geomorphic evidence suggests that Afton Canyon was cut rapidly sometime after 14,230 ±1325 yr B.P. The rapid draining of Lake Manix and subsequent basin dissection have important implications for late Quaternary lake fluctuations in Death Valley, base-level changes and resultant alluvial-fan adjustments in the Cronese basin, the sand source for the Kelso Dunes, and the absence of old artifacts in the Cronese basin and the Mojave River wash region.