DEVELOPING THE PALEOENVIRONMENTAL RECORD FROM BIG BONE LICK, KY: MINERALOGICAL, GEOCHEMICAL, AND ISOTOPIC CONSTRAINTS

The clay-rich, organic-poor lacustrine sediments preserved at Big Bone Lick (Boone County, northern KY) provide a unique opportunity to understand paleohydrological conditions within the middle Ohio River Valley during the latest Pleistocene. Continuous sediment cores from five locations at Big Bone Lick were recovered during July of 2004 using a truck-mounted split-spoon auger rig. Analysis of cores revealed a lower, blue-gray, lacustrine clay with a maximum thickness of ~3 meters, overlain by a ~4-meter thick package of oxidized clays, initially interpreted to represent post-glacial alluvial deposition.

A more complete understanding of paleoenvironmental conditions is being developed using clay mineralogy, bulk geochemical (metals; %C_org, %N), and stable isotopic (d ¹³C, d ¹⁵N of bulk organic matter) techniques. Preliminary results from x-ray diffraction studies indicate a predominance of expandable clays, including mixed-layer assemblages, together with illite and possibly vermiculite. With the exception of the uppermost soil zone, the sediments show a range in %N and %C_org from 0.04%–0.11% and 0.2%–1.0%, respectively, with higher concentrations within the lower blue-gray clay. Preliminary C/N and d¹³C_org results indicate distinct differences in either the type or level of degradation of organic matter preserved in the sediments. Future work will focus on further defining the paleoenvironmental significance of down-core changes in the organic signatures. The above results, coupled with studies of bulk-core analysis (natural gamma, magnetic susceptibility, bulk density), palynology, and sediment grain analysis will provide a more complete view of glacial-age paleoenvironmental conditions within a small catchment proximal to an important hydrological and sedimentological transport pathway.