UPDATED FULL-GLACIAL PALEOENVIRONMENTAL RECONSTRUCTIONS AT TWO SITES AT ABOUT 38.5° N BASED ON MODERN ANALOGS OF OSTRACODES FROM NACODE (NORTH AMERICAN COMBINED OSTRACODE DATABASE)

Bellefontaine Quarry, near Alton, Illinois (38.840°N, -90.242°W) yielded an ostracode record spanning from about 23.3 to 20.3 ka. Modern analogs (using species assemblage comparisons) provided data that suggested, for example, mean July temperatures ranged from about 16.8 to 18.1°C. The dataset that was used in those calculations was based on an extensive dataset that was collected and managed by L. Denis Delorme (Curry and Delorme, 2003). The dataset, however, did not include information from the United States; because most the southern limit of most species used in those estimates extended into the United States, temperature reconstructions were possibly too cold. Moreover, the influence of some species was not realized in this initial examination because two species common in the record are known to be alive in the United States, but not in Canada (Candona crogmaniana and Limnocythere ornata wabashensis). NACODe represents the recent merging of the Canadian and NANODe datasets (Curry et al., 2012) providing an opportunity to obtain robust modern analog analysis. The dataset includes environmental and hydrochemical data from 7,328 sites (609 of which are from NANODe), and of the presence/absence of more than 108 ostracode species. An unpublished ostracode record from Petersburg, Indiana (34.481°N, -87.287°W) has a similar assemblages and sediment age (23.7 to 20.5 ka) compared to the Bellefontaine record. I will discuss results of paleoclimatic reconstructions using the analog methods that use the ranges of either species or assemblages. In terms of LGM mean July temperature, the methods yield results that are about 1.5° C warmer than previously published.

Curry, B. B., Delorme, L. D., et al., 2012, The biogeography and physicochemical characteristics of aquatic habitats of freshwater ostracodes in Canada and the United States, In: Horne, D.J., Holmes, J.A., Rodriguez-Lazaro, J. & Viehberg, F. (Eds.), Ostracoda as proxies for Quaternary Climate Change. Developments in Quaternary Science, Elsevier, Amsterdam, The Netherlands, pp. 85-115.

Curry, B.B. and Delorme, L. D., 2003. Ostracode-based reconstruction from 23,300 to about 20,250 cal yr BP of climate, and paleohydrology of a groundwater-fed pond near St. Louis, Missouri, Journal of Paleolimnology: 29: 199-207.