Desert pavements and associated rock varnish in the Mojave Desert: How oldcan they be?

Authors
Citation
J. Quade, Desert pavements and associated rock varnish in the Mojave Desert: How oldcan they be?, GEOLOGY, 29(9), 2001, pp. 855-858
Citations number
33
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
GEOLOGY
ISSN journal
0091-7613 → ACNP
Volume
29
Issue
9
Year of publication
2001
Pages
855 - 858
Database
ISI
SICI code
0091-7613(200109)29:9<855:DPAARV>2.0.ZU;2-L
Abstract
Desert pavements are common features of and landscapes and have been widely used as a relative age indicator of the geomorphic surfaces upon which the y are developed. In this study I examined the patterns of pavement developm ent as a function of elevation in the Mojave Desert as well as the causes f or the gradual disappearance of pavement at high elevations. Pavement densi ty, as measured by percentage of pebble coverage, decreases systematically with elevation gain by similar to3% per 100 m, from 95% coverage below 500 m to less than 60% at 1700 in. Plants appear to be the main agent of paveme nt disruption; plant density decreases as pavement density increases. Burro wing by rodents and crusting by cryptobiota. also disrupt pavement developm ent at higher elevation. During the last glacial maximum, plant communities were displaced 1000-1400 m downward in the Mojave Desert. Pavements today generally do not survive above the blackbush (Coleogyne ramossisma)-sagebru sh (Artemisia tridentata) zone. Evidence from packrat middens shows that th ese and other plants typical of high elevations today grew as low as 300-40 0 m during the last glacial maximum. I suggest that during the last glacial maximum, desert pavements were confined to the lowest alluvial fans of Dea th Valley and adjoining low valleys. No alluvial desert pavements above sim ilar to 400 m in the region are older than the latest Pleistocene. By the s ame reasoning, desert varnish on desert pavements above 400 m may all be Ho locene in age, except where developed on stable boulders.