Applied Geology, Curtin University

The Neoproterozoic record of Rodinia break-up and biospheric evolution in Northwestern Canada

Abstract

Northwestern Canada preserves an exceptional stratigraphic record that spans from the time of the purported assembly of Rodinia ca. 1.0 Ga to Laurentia’s definitive break-out from the supercontinent sometime close to the Precambrian–Cambrian boundary. It has long bean appreciated that western Laurentia’s Neoproterozoic history involved more than a simple Wilson cycle, but details of its tectonostratigraphic evolution have remained obscure. The Neoproterozoic succession in Yukon reveals a complex history of basin development, punctuated by Cryogenian snowball glaciation. Multiple phases of continental extension occurred in the early Neoproterozoic, prior to regional uplift and tilting associated with emplacement of the c. 779 Gunbarrel large igneous province (LIP). Subsequent extrusion of the c. 720 Ma Franklin LIP in northern Laurentia was temporally closely associated with mafic volcanism in western Yukon, transtension, which generated thick pull-apart basins filled by Rapitan glacial deposits, and transpression, which resulted in the localized Corn Creek orogeny in eastern Yukon. Snowball glaciation subsequently stripped northwestern Canada of its abundant basalt carapace. Final opening of a passive margin in northwestern Laurentia did not occur until the late Ediacaran–early Cambrian. This convoluted history is reflected in the Nd isotope record preserved in fine-grained clastic sediments. This isotopic record, which reveals a prominent peak in εNd prior to the Rapitan glaciation, can addtionally be applied to testing palaeogeographic models of Laurentia’s place within a Rodinian supercontinent and its possible role in the initiation of snowball glaciation. The global seawater Sr isotope record also reflects the interplay of continental break-up, extensive early–mid Neoproterozoic flood basalt magmatism, and the profound influence of snowball glaciation on continental weathering. A new calibration of the Neoproterozoic stratigraphic record based in part on new ages from northwestern Canada can be used to apply approximate ages to key horizons in other age equivalent successions, including those of the Centralian Superbasin in Australia.
Biographical Details

Dr. Galen Halverson, an Associate Professor from McGill University of Canada (http://www.mcgill.ca/eps/halverson). He is visit Curtin as a CCFS-sponsored visitor between 4–15 November, 2013.

Galen’s research integrates sedimentology, stratigraphy, and isotope geochemistry to reconstruct ancient environments within the context of secular and progressive tectonic, biospheric, and climatic evolution of the earth. The underlying theme of his research is to reconstruct paleoenvironmental change spanning from the late Proterozoic to the early Phanerozoic (~ 1200 to 500 ma) and to understand the interconnections between tectonics (i.e., super continental break-up and assembly), seawater chemistry and ocean redox, severe climatic fluctuations (including snowball Earth), and the origin and diversification of animals. This research is fundamentally field-based and geared around detailed geological studies of sedimentary basins that formed during this time.