Geochemical Investigations of Major Environmental and Tectonic Changes in the Permian and Triassic

点击翻译按钮获取中文摘要

The record the chemical and isotopic composition of seawater through time contains a wealth of information about climate, tectonics, hydrothermal activity on the sea floor, and perhaps even about the details of sea level change, ocean circulation and atmospheric composition. The problem is to unravel the various signals recorded in sediments in terms of these processes. Here we will examine the time period spanning the Permian and early Triassic, a time of global environmental change. Our study will concentrate on the SR and Nd isotopic record, but will also include various other, probably related, geochemical indicators. Through collaborators, we have acquired a suite of samples for this work from geographically widespread, stratigraphically controlled, overlapping sections. Much of our work will be done on conodonts, which provide stratigraphic information as well as having conveniently high concentrations of most of the elements of interest, so that analyses can be made on single individuals or fragments in most cases. We will carefully investigate possible diagenetic effects, and attempt to delineate much more precisely than has been done previously the timing and magnitude of the observed large changes in Sr and Nd isotopic ratios in seawater during this time period. The data will be examined in terms of current knowledge of paleotectonics, paleoclimate and paleogeography. In addition, we will explore the feasibility of U-Th dating of conodonts in this time interval, in order to refine the temporal framework for our isotopic studies and to aid in section-to-section correlation.