NSERC grants at Laurentian University Subventions du CRSNG `a l ...

85Elizabeth TurnerProterozoic and early Paleozoic carbonate sedimentology:Influence of Earth system evolution on depositional systemsA grant of $25,300 per year.Une subvention de 25 300 $ par année.Discovery Grant – Subvention à la découverteThe fossil and geochemical records contained in carbonate sedimentaryrocks (limestone and dolostone) represent the single most important repositoryof information about biological and chemical evolution of the Earth’ssurface. Earth’s earliest atmosphere was oxygen-free, and accumulated oxygenslowly over about 3 billion years (66% of earth’s total lifespan to date).Significant levels of oxygen in the atmosphere, and the protecting ozonelayer that accompanies it, permitted multicellular and terrestrial life-formsto emerge eventually. Earth’s earliest biota was limited to single-celled organisms,many of which proliferated and produced oxygen by photosynthesis inshallow, tropical water where carbonate sediment accumulated. The initialemergence of more complex organisms (such as plants and animals) is documentedin 1.2 billion year old carbonate rocks, and their population of mostmarine niches was complete by about 475 million years ago. Many significantgaps remain in our collective understanding of this 3-billion-year-long seriesof events. By studying carbonate systems of Proterozoic age (544 to 2500million years old), this project will address two of these salient issues:1. when and how carbonate sedimentary environments changed from settingsthat reflect geochemically challenged conditions of the early Earthto those we consider biologically and sedimentologically ‘modern’; and2. how this affected biotic evolution.In addition to contributing to ongoing research into early earth systems, thisproject will also augment the understanding of Mesoproterozoic sedimenthostedore deposits in the Arctic, information which is needed to supportthe long-term economic development of Canada’s north. Field locations willinclude Proterozoic basins exposed in the Arctic and Paleozoic rocks exposedin Newfoundland and the Canadian Rocky Mountains.