Geochemical Integrity, Geochronology, and Paleoclimatology of Late Pleistocene Molluscan Specimens, U.S. Middle and Southeastern Atlantic Coastal Plain

9315052韦米勒评估化石标本的地球化学完整性是解决沿海平原地质年代学中几个长期存在的冲突的关键步骤，这些冲突可能源于现有数据上微妙的成岩蚀变叠加。将采用一种综合方法，除新开发的技术外，还将利用标准方法，以以前无法获得的精度确定和量化可能的变化。先进的定量高效液相色谱和气相色谱技术将被用来筛选用于氨基地层的软体动物样本，以确定贝壳中氨基酸的显著水解和/或损失。用气相色谱-同位素比值质谱仪(GC-IRMS)分析外来氨基酸对本地氨基酸种群的影响。最近发展起来的质谱学方法将用于研究珊瑚样品中的U系列同位素体系。附着在软体动物上的10到20对珊瑚样本将提供U系列和氨基酸年表的直接相互校准。软体动物贝壳的碳和氧同位素组成将用于古环境解释和进一步评估用于氨基地层的软体动物的潜在成岩蚀变。从壳体18O剖面可以计算出季节温度范围，从13C记录可以推断季节碳循环的模式。该项目包括两个用于解释壳牌同位素剖面的模型的实验测试。第一个将开发和改进区分盐度和温度对同位素组成的影响的方法。第二个是现场实验，将海水和沉积物孔隙水碳酸氢盐储集层的13C与贝壳的13C联系起来。这两项测试都解决了使用稳定同位素进行高分辨率古环境重建的基本问题。主要的科学目标是：1)测试大西洋海岸平原地层记录与全球更新世海平面记录之间的相关性；2)记录间冰期大西洋海岸的地理温度梯度。该项目将与美国地质调查局合作，作为研究上一次间冰期大陆和沿海气候记录的新倡议的一部分。

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.