Grant: Discovery Grants Program - Individual

The Ordovician and Silurian periods (ca. 500-420 million years ago) were*times of dramatically changing climate, sea level, and biodiversity. One of the*biggest mass extinction events in Earth history occurred near the end of the*Ordovician Period. The most important group of animals preserved in the marine*plankton during these time periods was the graptolites, a group of mostly*extinct hemichordates. They were abundant, geographically widespread and*evolved rapidly, which makes them excellent fossils for identifying short*intervals of geologic time and correlation of those intervals around the globe.*A thorough understanding of these organisms and their distribution in*sedimentary strata maximizes our potential to use them to solve a wide range of*Earth science problems in areas such as tectonics, sedimentary basin history,*climate change, and long-term evolution of the world's oceans. My research*program has several major and ongoing objectives: 1) reconstruction of the*evolutionary history of graptolites; 2) understanding the history of change of*graptolite biodiversity as a result of changing rates of species origination*and extinction, particularly through the cycles of climatic and oceanic changes*that characterized the Ordovician and Silurian periods; and 3) studying the*physical and chemical record preserved in rock strata to better understand the*environmental cycles and their causes, particularly to gain insights into the*factors responsible for the Late Ordovician Mass Extinction. For the last objective,*I am particularly interested in the history of anoxia in the oceans times*when large areas of the ocean became depleted in oxygen. I propose to examine*oceanic anoxia using sedimentary, paleontological and geochemical signals, and*investigate the formation and changing distribution of anoxia in terms of its*relationship to changes in climate, ocean circulation and biological*productivity. I will also integrate data from graptolite occurrences with the*geochemical record in sedimentary strata from several different parts of the*world to improve the precision with which we can define and subdivide*geological time. By improving the precision with which we can resolve*geological time, we can gain clearer insights into the timing and rates of*evolutionary, paleoenvironmental and geological processes. This research into*the long-term links among climate change, ocean circulation and biodiversity*will provide insights that will help us better understand the modern world of*changing climate and biodiversity.* p.p1