Preliminary paleomagnetic results from the Upper Carboniferous of Uliastai Block, Inner Mongolia, China



Paleomagnetic samples from five sites from the Upper Carboniferous Baoligemiao Formation of the Uliastai block (117°10′E, 45°30′N) preserve stable normal and reversed magnetizations, with mean D=138.3°, I=−47.8°, a95=9.7°, k=9.9. IRM acquisition and thermal demagnetization of IRM indicate that the magnetization in these pyroclastic sediments is predominantly carried by magnetite, however, higher coercivity minerals contribute to the remnant magnetization as well. The pole position (53.4°N, 14.8°E) derived from these results is near those of Sino-Korea and central Mongolia but significantly different from that of Siberia, suggesting that the Uliastai was not a Siberian-related fragment as traditionally proposed. Instead the block, along with the Mongolia and Sonid blocks, may have moved as a series of north-facing arc terranes (frontal and remnant arcs) of the Sino-Korean continent during the Late Paleozoic, possibly an ancient analogue of the Southeast Asian archipelago today.