2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 45-2
Presentation Time: 9:15 AM


HARDY, Fabian, Geoscience, University of Nevada Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV 89154 and ROWLAND, Stephen, History of Geo Div, GSA & History of Earth Sci Soc, Dept of Geosc, Univ of Nevada, Box 454010, Las Vegas, NV 89154

The paleoecology of North America may be studied through a combination of climate proxies and paleontology. Identification of megafaunal distribution is useful in determining the character of a region, and isotopic analysis of a single taxon leads to a higher resolution study.

Bison latifrons was a Late Pleistocene megaherbivore which inhabited the Great Basin and Great Plains regions of North America, with a temporal range between the Illinoian and Wisconsin glacial periods (130 – 85 ka). The taxon was previously assumed to have been adapted to forested environments, where it would have competed for resources with Mammut americanum. An alternate hypothesis suggests the bison inhabited the open areas of the Great Plains, and primarily competed with Bison antiquus. The data gathered in this study strengthen the understanding of the paleoecology and interactions of these species.

The assemblages sampled in this study are located in California, Colorado, Idaho, and Nevada. The use of carbon and oxygen stable isotopes determines whether there is a migration pattern visible in the populations studied. Oxygen data positively correlate with the locality of the sampled animals, while significantly offset δ18O values are characteristic of a herd with different origins. A large shift in δ13C value throughout the same site suggests a change in diet, possibly attributed to seasonal migration.

Data from Snowmass, Colorado were unexpectedly positive, and suggest a diet of exclusively C4grass, or diagenesis has occurred. A positive covariance between oxygen and carbon values suggests the same degree of diagenesis in both isotopic systems.

Data from American Falls, Idaho had averages of δ13C -7.72 and δ18O -9.22 ‰ VPDB. Carbon data indicate mixed feeding with a preference for C4 grass, suggesting the animals spent more time in open fields than previously thought. Seasonality is a possible cause for the covariation in several teeth sampled. δ13C values increase as the amount of C4 plants consumed increases, while δ18O values become more negative as a function of decreasing temperature.

Further data from the Diamond Valley Lake assemblage in Hemet, California are placed into context with our previous findings. Based on multiple assemblages, B. latifrons is characterized as an opportunistic browser which preferred open habitats.