Stable sulfur isotope composition of organic matter: Cambrian to Recent

摘要稳定碳同位素已被证明是研究显生宙地壳演化与生物圈复杂相互作用的有力工具。然而，从全球进化变化的角度来看，对构成有机质的其他轻元素（N， O， S， H）的相互关系的详细研究还很缺乏。以前的研究主要集中在矿物（硫酸盐、硫化物）和贝壳碳酸盐中的无机硫。因此，海洋生物有机硫含量如何随时间变化及其与无机硫同位素记录的关系和影响主要基于无机硫记录提供的间接证据，而不是直接探测。在显生宙期间，一个关于记录有机物稳定硫同位素组成变化的假设将被检验。远洋生物化石壳中蛋白质氨基酸（蛋氨酸和半胱氨酸）的稳定硫同位素组成可以作为重建海洋硫同位素组成长期变化的新指标。更广泛的影响：稳定碳同位素地球化学在提高我们对生物圈、水圈和岩石圈随时间演变的复杂相互作用的理解方面发挥了重要作用。对有机质稳定硫同位素组成的详细研究将为评价这种相互作用提供新的途径。迄今为止，这些信息只是通过研究被认为反映生物过程的矿物间接获得的。在保存完好的化石中，壳蛋白含硫氨基酸组分的稳定硫同位素组成很可能反映了原始海水的化学性质，与蒸发岩相比，受成岩作用改变的可能性较小。这种方法将为显生宙提出的无机硫同位素曲线的有效性提供第一个独立的测试。申请的资金将用于支持我们项目的新研究生路易丝·托滕的研究。路易斯有化学学士学位，因此非常适合这类项目。恩格尔的地质学和海洋学本科课程的学生经常参加他的稳定同位素和氨基酸实验室正在进行的研究项目。预计将有两名或两名以上的本科生在其科学教育专业的毕业论文中参与该项目。

ABSTRACTStable carbon isotopes have proven to be a powerful probe for investigations of the complex interplay between the evolution of the Earth's crust and biosphere throughout the Phanerozoic. However, detailed studies of this interrelationship for other light elements that comprise organic matter (N, O, S, H) in terms of global evolutionary change are lacking. Previous studies have focused on inorganic sulfur in minerals (sulfates, sulfides) and in shell carbonate. Thus, how the organic sulfur content of marine organisms varied through time and its relationship to and impact on the inorganic sulfur isotope record is based largely on circumstantial evidence provided by this inorganic sulfur record rather than by a direct probe. A hypothesis will be tested with respect to documenting changes in the stable sulfur isotope composition of organic matter during the Phanerozoic. The stable sulfur isotope composition of protein amino acids (methionine and cysteine) in fossil shells of pelagic organisms can be used as a new proxy for reconstructing secular changes in the sulfur isotope composition of the oceans. Broader Impacts: Stable carbon isotope geochemistry has played an essential role in improving our understanding of the complex interplay of the biosphere, hydrosphere and lithosphere as they have evolved through time. The proposed detailed study of the stable sulfur isotope composition of organic matter will provide a new approach for assessment of this interplay. To date, this information has only been acquired indirectly by the study of minerals thought to reflect biological processes. The stable sulfur isotope compositions of sulfur-containing amino acid constituents of shell protein in well-preserved fossils is likely to reflect original sea water chemistry and is less likely to have been altered by diagenetic processes than evaporites. This approach will provide the first independent test of the validity of the inorganic sulfur isotope curves that have been proposed for the Phanerozoic. The requested funds will be used to support the research of Louise Totten, a new graduate student in our program. Louise has an undergraduate degree in chemistry and is thus well suited for this type of project. Students from Engel's undergraduate courses in Geology and Oceanography are regular participants in on going research projects in his stable isotope and amino acid laboratories. It is anticipated that two or more undergraduates will be involved in this project for their senior theses in science education.