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Morphodynamics of meandering streams devoid of plant life; Amargosa River, Death Valley, California

Alessandro Ielpi
Morphodynamics of meandering streams devoid of plant life; Amargosa River, Death Valley, California
Geological Society of America Bulletin (November 2018) 131 (5-6): 782-802

Abstract

Vegetation-free fluvial meanders are exceptional on modern Earth, and their abundance in pre-Silurian rock records is debated. Whether or not landscapes devoid of plant life could sustain sinuous planforms is nonetheless a fundamental concept that could disclose parallels with extraterrestrial sedimentary realms. The sedimentology and morphometry of an extensive ( approximately 200 km (super 2) ) unvegetated meander plain in the lower Amargosa River (Death Valley, California, USA) is investigated through remote sensing and ground checking. Results reveal sinuous bends generated by channels <2 m deep and <35 m wide that migrated laterally for as much as 200 m at rates of <1.5 m/year. The Amargosa River's ephemeral regime excludes the proposal that discharge modulation directly aids meandering. Likewise, 97.7% of ground-checked meanders are devoid of plant life, ruling out direct control by vegetation on bank stability. Cohesion offered by mud-rich banks is predominant and aided by salt cementation, which also hinders wind erosion of fines. Overall, the meanders' morphometry is in overlap with that of other sinuous (vegetated) channels, pointing to shared scalar properties. Meanders span over a continuum of a few large channels with lower aspect (width:depth) ratios and abundant smaller channels with higher aspect ratios. The migration of larger meandering channels generates distinctive scrolls and inclined accretionary packages; the migration of smaller widespread meanders only generate sub-tabular sets, producing an undistinctive depositional record. These results make the Amargosa River topical for the analogue modeling of pre-vegetation rivers, and suggest that unvegetated meanders might have been overlooked in the rock record.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 131
Serial Issue: 5-6
Title: Morphodynamics of meandering streams devoid of plant life; Amargosa River, Death Valley, California
Author(s): Ielpi, Alessandro
Affiliation: Laurentian University, Harquail School of Earth Sciences, Sudbury, ON, Canada
Pages: 782-802
Published: 20181128
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Accession Number: 2019-007058
Categories: GeomorphologyApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch maps
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201906
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