Racemization kinetics of amino acids, determined for the commonly occurring fossil gastropod Succinea, facilitates the ability to construct an accurate and precise paleothermometer to estimate paleotemperatures over specific time intervals during the last 150,000 years in parts of Central Europe. Racemization within the carbonate shell of Succcinea is induced at high temperatures over increasing intervals of time in the laboratory and measured for aspartic acid (asp), glutamic acid (glu), valine (val), and phenylalanine (phe), by reverse-phase liquid chromatography. The activation energy (Ea), frequency factor (A), and forward rate constant (k1) of the Arrhenius equation are determined from the racemization of specific amino acids over time. The Arrhenius parameters, combined with racemization data and independent age estimates of fossil Succinea shells, are used to solve for temperature in geologic samples. Succinea recovered from a loess sequence in western Germany, located around the town of Nussloch, has been chosen for amino acid paleothermometry calculations. Samples were collected from the Nussloch loess -- paleosol sequence in the summer of 2001. The sequence spans from greater than 130,000 years to the present, is dated by luminescence and radiocarbon methods, and has abundant published proxy paleoclimate data for comparison. Temperatures calculated for the bracketed time interval representing the last glacial maximum (25 - 20ka) averaged -5.3°C± 6.8°C using aspartic acid racemization data. Arrhenius parameters for aspartic acid racemization were the best constrained and provide temperature estimates consistent with previously published data. Paleotemperatures calculated for other bracketed intervals of time within the Succinea shells from Nussloch dated within the last 150,000 years exhibited values similar to previously published data with acceptable error.

A recently discovered Bison-bearing fossil locality at Térapa, Sonora, Mexico, had previously been dated to 440 ± 130 ka using whole rock 40Ar/39Ar on a basalt flow that impounds the deposit. This age is considerably older than the accepted age of about 240-160 ka for the migration of Bison into greater North America. The Térapa deposit also contains a mixture of fossils from extralimital or extinct tropical animals and temperate animals. Constraining the age of the deposit is critical to interpret the paleontologic and paleoclimatologic implications of this unique Sonoran fossil locality. Three additional geochronological methods have been applied to this deposit (infrared stimulated luminescence (IRSL), amino acid racemization (AAR), and radiocarbon) and the data from the original 40Ar/39Ar age were revisited. The IRSL data suggest that the impounding basalt flow and the sediments that abut it were emplaced 43 ka ago and that the oldest sediments were deposited shortly after. Two radiocarbon ages suggest the fossiliferous sediments were emplaced by 42 ka. Effective diagenetic temperatures inferred from the AAR results, combined with AAR data from a similar-age deposit in southern Arizona, are in accordance with the 40-43 ka age estimates. For the AAR results to corroborate the 40Ar/39Ar age, the effective diagenetic temperature for the area would need to be approximately 3 °C, which is unrealistically low for northern Mexico. The new geochronological results suggest the Térapa deposit and fossils are 40-43 ka old. The anomalously old 40Ar/39Ar age for the impounding basalt is probably the result of low 40Ar* concentrations and inherited 40Ar.