PRELIMINARY STUDY OF LIMNOCYTHERE (OSTRACODA) BIOGEOGRAPHY IN QUATERNARY WESTERN NORTH AMERICA-A TOOL FOR TRACKING CHANGES IN HYDROCLIMATOLOGY

Non-marine ostracodes are well known proxies for past hydrochemical and temperature conditions in paleolimnologic records. Recent development of the multi-proxy community database Neotoma (www.neotomadb.org) provides new opportunities to test hypotheses about the past hydroclimatic conditions in Pleistocene western North America. Here, we examine the distribution of key paleolimnologic proxies, Limnocythere ceriotuberosa and L. bradburyi, as a first step in understanding their non-analog assemblage occurrence in Pleistocene lake records of the West. We show that the first documented co-occurrence of these species in the fossil record occurs in the early Pleistocene Butte Valley Lake, California (Carter, 1994; Mathias, 2012) and Lake Alamosa, Colorado records ( Rogers et al., 1992). These species also co-occur in assemblages of Owen’s Lake, California at about OIS 12 (Carter, 1997), and late Pleistocene (OIS 2-6) age in Walker Lake, Nevada (Bradbury et al., 1989) and Lake Babicora, Mexico (Chavez-Lara et al., 2012). However, since Late Glacial time these species have not co-occurred (Forester, 1985). We explore the significance of the sporadic occurrence of this non-analog assemblage in early and late Pleistocene time in western North America.