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GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 76-9
Presentation Time: 10:45 AM

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


SWEENEY, Mark R., Sustainability & Environment, University of South Dakota, 414 E. Clark Street, University of South Dakota, Vermillion, SD 57069, MCDONALD, Eric V., Division of Earth & Ecosystem Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, CHABELA, Lucas P., Terracon, 9856 South 57th St, Franklin, WI 53132 and HANSON, Paul, School of Natural Resources, University of Nebraska-Lincoln, 612 Hardin Hall, Lincoln, NE 68583

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.

Session No. 76

T2. Geomorphology and Climate Change in Hot Deserts
Monday, 23 September 2019: 8:00 AM-12:00 PM
Room 221AB, North Building (Phoenix Convention Center)
Geological Society of America Abstracts with Programs. Vol. 51, No. 5
doi: 10.1130/abs/2019AM-337211
© Copyright 2019 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.
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