Late Ordovician Epeiric Sea Circulation, Environmental Change, and Biotic Turnover: Model and Data Synthesis

晚奥陶世陆表海环流、环境变化和生物更替：模型和数据综合当今地球科学界面临的最困难的问题之一是确定生命历史上灭绝和迁移的最终原因。 在沉积记录中，生物的变化，如灭绝，往往与环境变化的证据，但环境变化的过程往往是复杂的，知之甚少。 根据沉积记录测试的物理系统的数值模型提供了一种手段，通过这种手段可以调查生物事件的最终原因。 我们建议使用海洋环流的数值模式来确定北美晚奥陶世灭绝事件的最终原因。 在第一个组成部分中，我们假设，在环境条件的快速变化与灭绝在晚奥陶世的北美是由水深的变化，古地理，和降水与造山运动。 我们将模拟海洋环流的两个时间间隔，跨越环境条件的突变和相关的灭绝事件。 我们将根据海洋条件的沉积指标分布来检验模型结果的有效性。 在研究的第二部分中，我们将研究单个变量的相对重要性，如海平面，古地理，水深和降水的变化，在产生快速的海洋学变化，可能导致物种的重大灭绝。 在调查灭绝的最终原因时，建模的优点是可以隔离单个变量，并评估它们对系统的影响。 我们将通过确定模型结果与空间和时间动物群变化的匹配程度来确定灭绝事件的可能原因。 通过深入了解这些陆表海快速海洋学变化的原因，这项研究具有广泛的影响，了解环境变化和灭绝在地球历史上的任何时候，陆表海的海洋生态系统的重要组成部分。

ABSTRACTLate Ordovician Epeiric Sea Circulation, Environmental Change, and Biotic Turnover: Model and Data SynthesisOne of the most difficult problems facing the earth science community today is identifying the ultimate causes of extinction and migration in the history of life. In the sedimentary record, biotic change such as extinction is often linked to evidence of environmental change, however the processes underlying environmental change are often complex and poorly understood. Numerical models of physical systems that are tested against the sedimentary record provide a means by which the ultimate causes for bioevents can be investigated. We propose to use a numerical model of ocean circulation to determine the ultimate causes for an extinction event in the Late Ordovician of North America.This study has two main components. In the first component we hypothesize that rapid shifts in environmental conditions linked to extinction during the Late Ordovician of North America were caused by changes in bathymetry, paleogeography, and precipitation associated with mountain building. We will model ocean circulation for two time intervals that span the abrupt shift in environmental conditions and related extinction event. We will test the validity of the model results against the distribution of sedimentary indicators of oceanographic conditions. In the second component of the study we will investigate the relative importance of single variables like changes in sea level, paleogeography, bathymetry, and precipitation in producing rapid oceanographic shifts in the epeiric seas that may have caused significant extinction of species. In investigating the ultimate causes of extinction, modeling has the advantage that single variables can be isolated and their effects on the system evaluated. We will identify plausible causes of the extinction event by determining how well the model results match the spatial and temporal faunal changes. By gaining insight into the causes of rapid oceanographic changes in these epeiric seas, this study has broad implications for understanding environmental change and extinction during any time in Earth's history when epeiric seas were important components of marine ecosystems.