EPS Seminar Series: Peter Crockford

Peter Crockford

Department of Earth Sciences, Carleton University

Friday, November 3

11- 12pm 

FDA 232

The Geologic History of Earth's Biosphere

Abstract: 

A grand challenge in the study of Earth’s past has been to reconstruct its history of oxygenation. This challenge has arisen as a consequence of a diminution of well-preserved sedimentary rocks back in geologic time. This lack of materials has led to the enduring controversy surrounding the texture of Earth’s oxygenation, and as an outcome, intense debate regarding specific oxygen levels across Earth’s early history. In this proposal I am seeking to understand Earth’s redox history immediately after Earth’s Great Oxidation Event. Here disparate signals have been reported from sediments of ≈2 Ga age, with samples from the Union Island Group deposited on the shores of Great Slave Lake displaying signatures of oxygenation and those from the Kasegalik Formation of the Belcher Islands not. One possible way to reconcile these discrepant records is to determine the degree to which they are recording global seawater or whether they are instead isolated basins recording local signatures. However, it is only until recently that geochemical tools to make such distinctions have been possible. If funded, this proposal seeks to apply new geochemical tools (triple oxygen isotopes of carbonate associated sulfate and barium isotopes in carbonates) to carbonates from both locations to determine their local or global nature.  Specifically, funding will be utilized for one field expedition to Great Slave Lake and the analysis of collected samples along with samples from the Kasegalik Fm. which are currently at Carleton University.