9315052 Wehmiller Assessing the geochemical integrity of fossil specimens is a critical step in resolving several long-standing conflicts in Coastal Plain geochronology that may stem from the subtle overprint of diagenetic alteration on the existing data. An integrated approach will be adopted that will utilize standard methods in addition to newly developed techniques to identify and quantify possible alteration with a precision previously unobtainable. Advanced quantitative HPLC and GC techniques will be used to screen mollusk samples used in aminostratigraphy for significant hydrolysis and/or loss of amino acids from the shells. Gas chromatography-isotope ratio mass spectrometry (GC-IRMS) will be used to assess the influence of extraneous amino acids on the indigenous amino acid population. Recently developed mass spectrometric methods will be used for study of the U-series isotopic system in coral samples. Between 10 and 20 paired specimens of corals attached to mollusks will provide a direct intercalibration of U-series and amino acid chronologies. The carbon and oxygen isotopic composition of the mollusk shells will be used for paleoenvironmental interpretation and further assessment of potential diagenetic alteration of mollusks used for aminostratigraphy. Seasonal temperature ranges can be calculated from shell 18O profiles and the mode of seasonal carbon cycling may be inferred from the 13C records. Two experimental tests of models used to interpret shell isotope profiles are included in the project. The first will develop and improve means of distinguishing salinity from temperature effects on the isotopic composition. The second is an in situ experiment relating the 13C of the seawater and sediment porewater bicarbonate reservoir to the 13C of the shell. Both tests address fundamental problems in using stable isotopes for high-resolution paleoenvironmental reconstruction. The major scientific goals are 1) to test correla tions between the Atlantic Coastal Plain stratigraphic record and global records of Pleistocene sea levels, and 2) to document the geographic temperature gradient along the Atlantic Coast during interglacial episodes. The project will involve collaboration with the US Geological Survey as part of a new initiative to study continental and coastal records of climate during the last interglacial.
