V036-02
Improving the Resolution of Rates and Dates by Integrating Paleomagnetic and High-precision Geochronological Techniques
Monday, 14 December 2020: 08:34
Virtual
Courtney Jean Sprain, University of Florida, Department of Geological Sciences, Ft Walton Beach, FL, United States, Tushar Mittal, Massachusetts Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences, Cambridge, MA, United States, Isabel Fendley, University of California Berkeley, Earth and Planetary Science, Berkeley, CA, United States, Marissa M Tremblay, Purdue University, Department of Earth, Atmospheric, and Planetary Sciences, West Lafayette, IN, United States, Paul R. Renne, Berkeley Geochronology Center, Berkeley, CA, United States and Darren F Mark, Scottish Universities Environmental Research Center at the University of Glasgow, East Kilbride, United Kingdom
Abstract:
In the past few decades, the field of high-precision geochronology has achieved a large increase in the precision of dates (with achievable precision levels ~0.1 - 0.01%). This enhanced precision has allowed us to more closely investigate many geologic processes, such as the causes of mass extinction events. Despite this enhanced precision, there are still many processes that occur on timescales not resolvable by high-precision geochronologic techniques. Outside of absolute geochronologic methods, there are other indirect methods that can help resolve timescales finer than those achievable by high-precision geochronology. One such method is paleomagnetism, whereby short- (1 - 10,000 yr) and long-term (100,000 - 1,000,000 yr) variations in Earth’s magnetic field are recorded in rocks. By utilizing independent constraints on the rates and timing of magnetic changes (e.g. field reversals and secular variation) in combination with high-precision geochronology, we can start to resolve shorter timescales than that achieved by high-precision geochronology alone.
In this presentation, I will show results from three studies which integrate paleomagnetic and geochronologic techniques: the age of the Rajahmundry Traps, duration of eruptive pulses in the Deccan Traps, and timing of vitrified fort formation in Scotland. In the first case study, I will illustrate how we significantly improved constraints on the timing of the Rajahmundry Traps eruptions (the longest known Deccan Traps lava flows) by incorporating high-precision magnetochron boundary ages with direct dates (e.g. 40Ar/39Ar) on lava flows. In the second example, I will show how we obtained 1-10 kyr resolution constraints on the eruptive tempo of the Deccan Traps (comparable to paleoclimate proxies) by using flow-by-flow paleomagnetic directions in combination with long records of paleosecular variation and absolute geochronologic constraints. In the third case, I will discuss how we better resolved the age of Scottish vitrified fort by integrating 40Ar/39Ar geochronology with archaeomagnetic dating.
