The Geology of Glaciated Sedimentary Basins

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The time interval from c. 750 to 600 million years ago (the Neoproterozoic) was dominated by the disintegration of the large supercontinent Rodinia. One unusual characteristic of the many extensional sedimentary basins that formed during continental rifting and breakup are exceptionally thick (~1 km) successions of diamictites that are poorly-sorted mixtures of particles ranging from mud to boulders. Despite decades of research their origin remains enigmatic. They are interpreted by some geologists as ancient glacial tills (`tillites') left by extensive ice sheets during world-wide ice ages (c. 770-735 Ma Kaigas, c. 715-680 Ma Sturtian, c. 660-635 Ma Marinoan, and c. 585-582 Ma Gaskiers events) with extremely low global temperatures (-50 °C) and frozen oceans. Other geologists argue that diamictites are glacially-influenced submarine debris flows deposited in open oceans akin to Pleistocene and modern glacially-influenced environments, or are entirely non-glacial and therefore lack climatic significance. The lack of agreement over the origin of diamictites is a fundamental data gap in understanding the history of Earth's climate and the evolution of the biosphere. It is also of direct economic importance. Exploration for stratiform copper hosted within thick (1.25 km) Neoproterozoic diamictites of the Katanga Basin in the Democratic Republic of Congo (DRC) by a Canadian mining company (Ivanplats) and for unconventional oil in such rocks in Brazil by Petra Energia SA has generated exceptional (and hitherto unavailable) basin-wide databases of drill core through Neoproterozoic diamictites and related facies, together with downhole geophysical and regional seismic and aeromagnetic data. This project identifies a plan to exploit these new databases by analyzing drill core and geophysical data in conjunction with the description and sampling of targeted surface outcrop exposures across DRC and Brazil. This will allow a clear methodology for the description and interpretation of diamictite facies and resolution of their origin and their tectonic significance within evolving Neoproterozoic basins. The project will provide key insights into the nature of Neoproterozoic hydrological cycles and the cryosphere and climate system at a time of rapid biological diversification linked by some to global ice ages. Substantial progress can be made in five years and results will be communicated in first class journals during the course of the project. This timely and ambitious research project will enhance Canadian expertise in mineral exploration and glacial sedimentology, accelerate resource exploration and investment in developing economies and promote opportunities for advanced student training and employment of Canadian geologists.**