Paleomagnetic Results From Early Cretaceous Basalts and Sediments of the Trans-Baikal Region, Southeastern Siberia

The Cretaceous was a time of tectonic reorganization of the globe. This study focuses on Early Cretaceous volcano-sedimentary sections of Thikhoi-Khilok, Borgoi, and Uda basins of the Trans-Baikal Region, Southeastern Siberia. We wonder what it can tell us about tectonic displacements and rotations of the region and intraplate motions within central Asia. New paleomagnetic results have been obtained from 12 dated Cretaceous basaltic lava flows and one sandstone site exposed in these basins. Progressive thermal and AF demagnetization removed a secondary magnetization, after which the characteristic component (ChRM) is isolated and decays toward the origin. The mean ChRM directions pass reversal, conglomerate, and fold tests. The corresponding paleomagnetic pole is not statistically different from the 95-130 Ma reference pole of Besse and Courtillot (2002) in terms of paleolatitude. About 10 degrees clockwise rotation in declination, only marginal statistically significant, is indicated by the data. Our data thus suggest that the southeastern margin of the Siberian Platform appears not to have rotated significantly relative to the platform itself and the Eurasian reference poles for the Cretaceous period are appropriate for Siberia. The new paleomagnetic evidence supports our Russian colleague~{!/~}s belief that sinistrial-strike slip motion may have existed in the Transbaikalia region during Late Mesozoic, which may lead to the interplate magmatic activities.