PALEOMAGNETIC CONSTRAINTS FROM NEOPROTEROZOIC TO EARLY-CAMBRIAN ROCKS IN MONGOLIA: IMPLICATIONS FOR STURTIAN GLACIATIONS AND MICROCONTINENT EVOLUTION

Worldwide glaciations in the Late Neoproterozoic to early Cambrian are currently under considerable debate and as of yet lack undisputable support. A comprehensive paleomagnetic database from this time period that includes reliable studies taken from widespread localities is necessary. The Ural-Mongol mobile belt in central Asia is a valuable site for paleomagnetic study as it includes microcontinents of Neoproterozoic and Cambrian age. Thus, we have sampled volcanic and sedimentary sequences in the Zavkhan Basin, Mongolia in order to determine the ancient location of this microcontinent and progression of tectonic events that culminate in the formation of the Eurasian continent.

We will present paleomagnetic data from the Tsagaan Oloom and Bayan Gol formations, both of which are sedimentary sequences accumulated in a back-arc basin related to microcontinent accretion. The Neoproterozoic glaciations are represented at the base of the Tsagaan Oloom formation and overly the 850-700 Ma (Khomentovsky and Gibsher, 1996) Dzabkhan volcanic sequence. Previous studies from the area have yet to agree on a single conclusion and show possible remagnetization and overprints. However we will report more precise paleomagnetic data on a greater number of samples in order to determine paleolocation of glacial deposits and the ancient tectonic evolution of the area.