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GEOPHYSICAL RESEARCH LETTERS,
VOL. 33,
L10201,
doi:10.1029/2005GL025618,
2006
Aspects of alluvial fan shape indicative of formation process: A case study in southwestern California with application to
Mojave Crater fans on Mars
Rebecca M. E. Williams
Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC, USA
James R. Zimbelman
Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC, USA
Andrew K. Johnston
Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC, USA
Abstract
Longitudinal profiles from six alluvial fans surveyed in southwestern California have quantitative attributes that can distinguish
formation processes. The radial slope of fans where debris flow processes dominated is constant while fluvially-fed fans have
a concave-upward shape. We find the power law regression of upstream slope-distance profiles is the preferred approach for
assessing concavity. Concavity index, the exponential determined via power law regression analysis, is an accurate reflection
of the magnitude of the concavity and thus a qualitative measure of the relative influence of fluvial processes on the fan.
Fan length and surface gradient are inversely correlated: debris flow fans are shorter and steeper (>15°) than their fluvial
counterparts. The results of this investigation provide criteria to evaluate hypothesized formation processes and provide
constraints on the amount of fluid and timescales involved in the generation of comparably-sized fans within Mojave Crater,
Mars.
Received 26
December
2005;
accepted 18
April
2006;
published 19
May
2006.
Index Terms: 1824 Hydrology: Geomorphology: general (1625); 1825 Hydrology: Geomorphology: fluvial (1625); 5415 Planetary Sciences: Solid Surface Planets: Erosion and weathering; 5419 Planetary Sciences: Solid Surface Planets: Hydrology and fluvial processes; 6225 Planetary Sciences: Solar System Objects: Mars.
Read Full Article (file size: 324533 bytes) Cited by
Citation: Williams, R. M. E., J. R. Zimbelman, and A. K. Johnston
(2006),
Aspects of alluvial fan shape indicative of formation process: A case study in southwestern California with application to
Mojave Crater fans on Mars,
Geophys. Res. Lett.,
33,
L10201,
doi:10.1029/2005GL025618.
Copyright 2006 by the American Geophysical Union.
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