T76 Geomorphology and Climate Change in Hot Deserts

Monday, 23 September 2019
8:00 AM - 12:00 PM
Room 221AB, North Building

THE ROLE OF EOLIAN-FLUVIAL INTERACTIONS AND DUNE DAMS IN ALLUVIAL FAN AND EPHEMERAL WASH DYNAMICS, LATE PLEISTOCENE-HOLOCENE, MOJAVE DESERT, USA

Paper number: T76-11
Program: Technical Sessions
Time: 10:45 AM – 11:00 AM

Authors

Abstract

Pleistocene-Holocene eolian-fluvial interactions associated with the formation of the Kelso Dunes in the eastern Mojave Desert resulted in significant aggradation of alluvium followed by incision. The incision of Afton Canyon along the Mojave River ca. 25 ka greatly increased eolian sediment supply. Available sediment and ample winds resulted in the east-southeast migration of sand dunes along an eolian transport corridor. Dunes temporarily dammed Kelso Wash as well as washes draining alluvial fans, resulting in >10 m aggradation of eolian and fluvial-alluvial sediments. Stratigraphic exposures reveal numerous fining-up sequences with interbedded eolian sand. Some fining-up sequences may represent individual flood events, and clay-rich caps represent temporary standing water. Luminescence ages reveal that dune blocking and aggradation correspond to a regional pulse of alluvial fan sedimentation that occurred about 14 to 9 ka. Breaching of the dune dams and incision occurred with a subsequent pulse of alluvial fan sedimentation ca. 6 to 3 ka. Meanwhile, relative landscape stability occurred downstream of dune dams, resulting in the formation of a moderately developed soil on abandoned fluvial deposits. This soil is not present in areas where the dune dams fostered rapid sediment accumulation or in areas that were mantled by dunes. The cut-and-fill histories of washes in this system appear to be strongly controlled by climate change in combination with complex response associated with the formation of dune dams that changed local base level. These eolian-fluvial interactions are closely tied to the Mojave River-Lake Mojave system that feeds sediment to the dunes that impounded massive amounts of sediment derived from alluvial fans deposited during the Pleistocene-Holocene transition. This profound impact on the regional geomorphology highlights the critical importance of eolian-fluvial interactions in desert environments.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-337211

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