RELATIVE INFLUENCE OF CLIMATIC AND BASE-LEVEL CHANGE ON THE LATE QUATERNARY EVOLUTION OF ALLUVIAL FANS IN THE NORTHERN GREAT BASIN, NEVADA, USA

Mountain-front alluvial fans in the northern Great Basin were affected by late Quaternary climatic changes, and by climatically-induced base-level changes through fluctuations in pluvial lake levels. Several fan groups studied on the margins of and near pluvial Lake Lahontan were all affected by climatically-led variations in sediment supply, but only those on steep mountain fronts adjacent to deep lakes were affected by base-level changes during lake desiccation.

Major periods of fan aggradation occurred prior to the last glacial maximum and during the Holocene, with little or no fan deposition occurring during and after the last glacial maximum, at the time of high lake levels. The differential effects between fans with and without base-level influence are expressed in differences in fan geometry and fan morphometry.

The fans of the northern Great Basin contrast with fans adjacent to pluvial Lake Mojave further south within the Mojave Desert, where there there was less effective base-level control and where the effects of Late Quaternary climatic change were more pronounced. These differences are expressed in fan geometry and fan morphometry.