The lower Colorado River Valley: An Ice-age Desert
Abstract From:
Cole, K. L. 1986. The lower Colorado Valley: A Pleistocene Desert. Quaternary Research 25:392-400.
A chronological sequence of plant macrofossil assemblages 25 packrat middens provides a record of desert scrub vegetation for most of the last 13,380 yr. B.P. from a hyperarid portion of the lower Colorado River valley. At the end of the late Wisconsinan, and probably during much of the Quaternary, the Picacho Peak area, Imperial County, CA, supported a typical Mojave Desert association of Larrea tridentata (creosote bush), Coleogyne ramosissima (blackbrush), Yucca brevifolia (Joshua tree), and Yucca whipplei (Whipple yucca). Recent arrivals of Sonoran Desert plants such as Olneya tesota (ironwood) and Fouquirea splendens (ocotillo) suggest that the area supported relatively modern Sonoran Desert scrub species for relatively short periods during interglaciations.
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