2007 GSA Denver Annual Meeting (2831 October 2007)
Paper No. 144-35
Presentation Time: 8:00 AM-12:00 PM

PALEOECOLOGY OF PLEISTOCENE MEGAFAUNA IN SOUTHERN NEVADA: ISOTOPIC EVIDENCE FOR BROWSING ON HALOPHYTIC PLANTS

VETTER, Lael1, LACHNIET, Matthew S.2, and ROWLAND, Stephen M.2, (1) Department of Geology, University of California Davis, One Shields Avenue, Davis, CA 95616, lael.vetter@gmail.com, (2) Department of Geoscience, University of Nevada Las Vegas, Box 454010, Las Vegas, NV 89154-4010

Stable isotopic techniques are emergent as a powerful tool for paleoecological reconstructions of Neogene terrestrial mammals. Reconstructions of herbivore diet may be augmented by correlation with paleofloral analyses. The Las Vegas Valley in southern Nevada contains a diverse Late Pleistocene fossil assemblage. Pleistocene packrat midden and pollen data for the Mojave Desert provide an independent, site-specific record of vegetation during pluvial climate. This study investigates the diets of four megafaunal genera (Mammuthus, Equus, Bison, and Camelops) using d13C signatures preserved in tooth enamel. These fossils were recovered from a Late Pleistocene spring mound in the northwestern Las Vegas Valley; radiocarbon tests constrain the age of these fossils to the Last Glacial Maximum (LGM). The d13C values from the three grazing genera (Mammuthus, Equus, and Bison) indicate that these animals consumed C3 and C4 grasses in the naturally occurring proportion, which locally consisted primarily of C3 grasses. The d13C values from Camelops indicate the highest proportion of C4 plants consumed. Independent vegetation records, paired with paleoclimatological reconstructions, indicate a low abundance of C4 grasses during the LGM, but a moderate abundance of the halophytic C4 shrub Atriplex, a substantial component of modern Mojave Desert vegetation. Modern camelids prefer halophytic plants, including Atriplex. Data from this study indicate that fossil camelids in North America also demonstrated this preference for salty plants, and consumed browse material with a high proportion of C4 halophytic shrubs. Results from serial sampling are also presented as a subannual record of dietary variation and seasonality. Intratooth d13C variation is approximately 1-2 in grazing taxa and 3-4 in the browser. Some d13C variation exhibits an inverse relationship with intratooth d18O values. This study provides new insight into isotopic reconstructions of paleoecology in arid environments.

2007 GSA Denver Annual Meeting (2831 October 2007)
General Information for this Meeting
Session No. 144--Booth# 118
Paleontology (Posters) II: Environments, Ecosystems, and Interactions
Colorado Convention Center: Exhibit Hall E/F
8:00 AM-12:00 PM, Tuesday, 30 October 2007

Geological Society of America Abstracts with Programs, Vol. 39, No. 6, p. 402

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