EVOLUTION OF THE KHOVSGOL PALEOBASIN: NEW GEOLOGICAL MAPPING, CHEMOSTRATIGRAPHY, AND GEOCHRONOLOGY FROM THE KHOVSGOL GROUP, MONGOLIA

With abundant stratigraphic exposure spanning late Tonian through Cambrian time, the Khovsgol Group of northern Mongolia provides a window into the critical changes in environment and biota that occurred in the late Neoproterozoic and early Cambrian. In addition to well-preserved Cryogenian carbonate sequences situated between the Ongoluk and Khesen diamictites (associated with the Sturtian and Marinoan snowball earth glaciations, respectively), massive phosphorite deposits thought to be of latest Ediacaran to early Cambrian age are exposed throughout the region. A thick (>1.5km) succession of Cambrian carbonates, including reported occurrences of trilobites and archaeocyathids, overlies the phosphorites. However, the complex regional tectonic history of northern Mongolia necessitates detailed mapping, structural analysis, and stratigraphic measurements in order to reconstruct the environment into which the Khovsgol Group was deposited. Paired with new geochronological and chemostratigraphic constraints from multiple measured sections throughout the region, new geologic mapping of the Khovsgol Group from several localities in northern Mongolia provides insight into the development and evolution of the Khovsgol Paleobasin. In addition to developing structural and stratigraphic constraints on the tectonic setting and basinal evolution of the Khovsgol Group, this work provides paleoenvironmental context for the emplacement of some of the largest phosphate ore deposits in the world.