Geochemical and Isotopic Constraints on Mesoproterozoic Ocean Chemistry

Regions: Sahtu Settlement Area

Tags: biology, atmospheric sciences, paleoclimatology

Principal Investigator: Kah, Linda (3)
Licence Number: 12975
Organization: University of Missouri
Licensed Year(s): 1998
Issued: Jun 15, 1998
Project Team: Dr. Timothy W. Lyons, Dr. Tracy D. Frank, Dr. Julie K. Bartley, Micael Formolo, Burt Thomas

Objective(s): The Mesoproterozoic Eon (1600 - 1000 Ma) represents a critical period in Earth history from the standpoint of global tectonic reorganization, biological evolution, and the rise in oxygen in the Earth's early atmosphere. Yet despite this obvious significance, the Mesoproterozoic remains one of the most poorly understood and poorly documented intervals in Earth history. Recently, a global record of marine carbon isotopic compositions has been compiled that suggests a fundamental change in biogeochemical cycling during this interval. The timing of this observed transition in marine carbon isotopic compositions is particularly intriguing in that it occurs in conjunction with known tectonic activity and a rise in the concentration of atmospheric oxygen. The goal of the proposed research is to generate C-Sr-S isotopic data for this interval and, thereby begin to address the mechanisms behind geochemical changes in the Mesoproterozoic ocean. By integrating several different isotopic systems we can address specific questions, including the causes and consequences of biogeochemical change in the early biosphere.

Project Description: Our goals will be achieved through a multidisciplinary study integrating depositional, diagenetic, and geochemical information into a single comprehensive framework. Over a single field season we will measure stratigraphic thickness of outcrops in the Dismal Lakes Group, Coppermine homocline, NWT and collect small (hand sized) samples from a wide range of different rock types that represent different depositional environments. This succession has been chosen on the basis of accessibility and exposure of stratigraphic units, the presence of a wide variety of facies from different depositional environments. In the lab, these samples will be examined petrographically for signs of alteration that would otherwise hamper the interpretation of geochemical and isotopic data.