Deformation of Asian continent

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Collision of India and Asia is one of the most prominent tectonic events in Cenozoic time. The Indian continent collided to Asia at about 52 Ma and continued to penetrate into the Asian continent. The northward penetration of the India gave rise to tectonic deformation in the Asian continent.The present program of investigation aims to detect tectonic defonriation on eastern part of Asian continent from paleomagnetic view points. We chose the Yunnan and Sichuan in China areas as possible areas which was subjected to deformation due to collision of Indian continent. Inner Mongolia of China and Sikhote Alim area in Russia are regarded as areas without any deformation.We carried out our paleomagnetic study in these four areas. We focused the Jurassic welded tuffs, the Jurassic red sandstones, the Upper Cretaceous red sandstones and the Paleocene wefded tuffs, because late Mesozoic formation preserves evidence of deformation later than 52 Ma when India collided. More than 750 samples were collected from these four areas. Three to ten hand samples, oriented with a magnetic compass, were distributed over a distance ranging up to 15m in a site. Localities of sites were determined by a portable navigational instrument. The present declination value at the sampling point was estimated from the calculation using the International Geomagnetic Reference Field of 1994.In the laboratory, individual specimens, 25mm in diameter and 23mm long, were prepared from samples. Natural remanent magnetizations were measured with a 2G cryogenic magnetometer. One specimen from each sample was subjected to stcpwise thermal demagnetization up to 690* 710*. Measurement data are now analyzed.