Paleomagnetism of Neoproterozoic to Lower Paleozoic Rocks on Microcontinents of Central Asia: Implications for the Precambrian Glacial Paradox and Amalgamation of Eurasia

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The microcontinents that make up Eurasia were amalgamated over a protracted period beginning in the Cambrian Period (~520 million years ago). The rocks that lie on these microcontinents contain older (Precambrian-age) igneous and sedimentary rocks that formed, at least in part, during a period of time thought to be characterized by extreme swings in global climate. These episodes of severe climate change are dubbed the "Snowball Earth" epochs. Both the location of these microcontinents prior to their incorporation into Eurasia and the exact age of the glacial events preserved on the microcontinents are poorly known. This work focuses on obtaining paleomagnetic and geochronologic data from various microcontinents now located in Mongolia, Khazakhstan and Kyrgystan. The data collected in this study allow the investigators to better constrain the position of these microcontinents prior to their amalgamation into Eurasia. The data also supply researchers with important paleolatitudinal and geochronologic constraints on the glacial sediments preserved on the microcontinents. Since the Snowball Earth hypothesis posits near global synchroneity of glaciation across the planet, these data provide a critical test of the Snowball Earth hypothesis as well as a test of other competing explanations for this ancient ice age. Lastly, the data obtained in the study impose strong constraints on the general style of tectonic evolution for the Ural-Mongol fold belt that developed as a result of collisions between the microcontinental blocks and the closure of an ancient ocean.Support for the project is provide by the Tectonics Program and by the Russia and Eurasia Group of the Office of International Science and Engineering.