Integrating high-precision U-Pb geochronologic data with dynamic models of earth processes

Abstract

Radioisotopic dating can provide critical constraints for understanding the rates of tectonic, dynamic and biologic processes operating on our planet. Improving the interpretation and implementation of geochronologic data by coupling it with numerical modeling studies is the central theme of this thesis. Each chapter works to address a variety of problems in the Earth sciences. In each study, the interpretation of geochronologic data is aided with a numerical model that simulates the long-term behavior and/or initial conditions of the U-Pb system and provides an effective means of exploring the parameters that influence a calculated date. The record provided by geochronologic data is then coupled with models to quantitatively determine rates of geologic process on Earth. This approach permits geochronologic data to move beyond just establishing a relative time line of events. Using this dual modeling approach, Chapters 2-5 work to measure the long-term cooling and erosion rate of the lithosphere, specifically constraining the time scales and rate of transition between the stages of mountain belt formation and stability. Chapter six works to constrain the timing and duration of Central Atlantic Magmatic Province flood basalt volcanism and its relationship to the end Triassic mass extinction. The seventh and final chapter uses high precision U-Pb geochronology to evaluate the reliability of an Ar-Ar standard often used as a fluence monitor. The overall focus of this thesis has been to push the envelope of geochronologic precision and accuracy while coupling the data with modeling studies to yield new insight into Earth systems.