Document Type
Article
Department or Administrative Unit
Geological Sciences
Publication Date
3-30-2013
Abstract
Vesicular A (Av) soil horizons form beneath desert pavements from the accretion of aeolian sediment (dust) commonly thought to be derived primarily from desiccating pluvial lakes and playas, with contributions from ephemeral washes and alluvial fans. Particle size distributions of Av horizons are typically bimodal with primary modes of very fine silt and fine sand, suggesting that the horizon matrix is derived from multiple sources. Here we conduct detailed chemical and physical analysis of both Av horizon soil samples and potential sources of aeolian sediment to better constrain the relative contributions of dust associated with the development of Av horizons. Geochemical data from both sand (125–250 µm) and silt (2–32 µm) fractions in Av horizons and potential dust sources in the eastern Mojave Desert and western Sonora Desert, USA, point to large contributions from nearby sources including distal alluvial fans and washes, and comparably lower contributions from regional sources such as playas. The silt mode is derived from suspension transport of dust, and the fine sand mode is derived from saltating sand. The desiccation of pluvial lakes in the Mojave Desert is commonly believed to have driven episodes of aeolian activity, contributing to sand dunes and Av horizon formation. We propose that alluvial fans and washes are underappreciated as desert dust sources and that pulses of dust from late Pleistocene and Holocene alluvial fans dwarfed pulses of dust from desiccating pluvial lakes in the eastern Mojave Desert.
Recommended Citation
Sweeney, M. R., E. V. McDonald, and C. E. Markley (2013), Alluvial sediment or playas: What is the dominant source of sand and silt in desert soil vesicular A horizons, southwest USA, J. Geophys. Res. Earth Surf., 118, 257–275, doi:10.1002/jgrf.20030.
Journal
Journal of Geophysical Research: Earth Surface
Rights
© 2013. American Geophysical Union. All Rights Reserved.
Included in
Geology Commons, Geomorphology Commons, Soil Science Commons, Tectonics and Structure Commons
Comments
This article was originally published in Journal of Geophysical Research: Earth Surface. The full-text article from the publisher can be found here.