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

美国中大西洋和东南大西洋沿海平原晚更新世软体动物标本的地球化学完整性、年代学和古气候学

• 批准号: 9315052
• 负责人: John Wehmiller
• 金额: $ 27.29万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-08-15 至 2000-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9315052&HistoricalAwards=false
• 关键词: Geochemical; Integrity; Geochronology; Paleoclimatology; Late

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.

9315052 WEHMILLER评估化石标本的地球化学完整性是解决沿海普通年代学的几次长期冲突的关键步骤，这可能是由于现有数据对成岩成分的细微覆盖所造成的。 除了新开发的技术外，还将采用一种综合方法，该方法将利用标准方法来识别和量化可能的更改，而先前无法获得的精确性。 先进的定量HPLC和GC技术将用于筛选用于氨基地层学中用于大量水解和/或壳中氨基酸损失的软体动物样品。 气相色谱 - 同位素比率质谱法（GC-Irms）将用于评估外部氨基酸对土著氨基酸种群的影响。 最近开发的质谱方法将用于研究珊瑚样品中的U系列同位素系统。 连接到软体动物的珊瑚的10到20个配对标本将提供U系列和氨基酸年代的直接构图。 软体动物壳的碳和氧同位素组成将用于古环境解释，并进一步评估用于氨基地层学的软体动物的潜在成岩剂改变。 季节性温度范围可以从外壳18O轮廓计算出来，可以从13C记录中推断出季节性碳循环的方式。 项目中包括了两个用于解释壳同位素轮廓的模型的实验测试。 第一个将发展并改善将盐度与温度对同位素组成的影响区分开的方法。 第二个是将海水和沉积物孔隙水碳酸氢盐储层与壳的13C相关的原位实验。 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方面的基本问题。 主要的科学目标是1）测试大西洋沿海平原地层记录与全新世水平的全球记录之间的相关性，以及2）记录冰川间发作期间大西洋沿岸的地理温度梯度。 该项目将涉及与美国地质调查局的合作，这是一项新计划的一部分，该计划在上一次冰川间期间研究了气候的大陆和沿海记录。