Dimension of Greater India in the early Mesozoic: Paleomagnetic constraints from Triassic sediments in the Tethyan Himalaya

The northern dimension of Greater India, defined as the continental part of India from which the Himalayan fold-thrust belt was derived, is difficult to determine due to major tectonic deformations of the Himalaya during the Tertiary caused by the India-Eurasian collision. Paleomagnetic data from the Tethyan Himalaya can potentially help determine this dimension. However, the tectonic deformations also led to widespread remagnetization of rocks there and thus previously published paleomagnetic poles from the lower Mesozoic Himalayan rocks may not accurately reflect their original paleomagnetic directions. To better understand the Triassic history of India in a Gondwana configuration, we report new paleomagnetic data (after tilt correction D = 345.5 degrees, I = -43.0 degrees, alpha 95 = 12.0 degrees, k = 17.3, N = 10 sites and the corresponding paleopole at 34.5 degrees N, 282.2 degrees E with A(95) = 11.7 degrees) of Triassic limestone and sandstone from the Tulong Group in the Tethyan Himalaya. The primary features of the magnetization are supported by the positive fold test. Our new Triassic paleomagnetic pole overlaps with 230-250 Ma poles from India, suggesting the close affinity between the Tethyan Himalaya and cratonic India since the Triassic. Assuming that the Tethyan Himalaya was a part of the Great India since Triassic, the differences between the Tethyan Himalaya paleolatitude obtained by this study and those previously reported for the cratonic India imply similar to 1300 km dimension of the Tethyan Himalaya has been absorbed after the Eurasia-India collision. (C) 2011 Elsevier Ltd. All rights reserved.