Paleomagnetic results from the Early Cretaceous Lakang Formation lavas: Constraints on the paleolatitude of the Tethyan Himalaya and the India-Asia collision

To better constrain the Early Cretaceous paleogeographic position of the Tethyan Himalaya and the India-Asia collision process, a paleomagnetic study was performed on the Lakang Formation lava flows in the Cuona area in the southeastern Tethyan Himalaya. Stepwise thermal and alternating field demagnetizations successfully isolated reliable characteristic remanent magnetization (ChRM) directions that include antipodal dual polarities and pass positive fold tests at the 99% confidence level and reversal tests at 95% confidence level, indicating prefolding primary magnetizations. The distribution patterns of ChRM directions from the Lakang Formation lava flows are consistent with young lava flows at similar latitudes, suggesting that secular variation has likely been averaged out. The tilt-corrected site-mean direction for 31 sites is D = 261.6 degrees, I = -68.5 degrees with alpha(95) = 3.6 degrees, which provides a paleopole at 26.8 degrees S, 315.2 degrees E (A(95) = 5.7 degrees), corresponding to a paleolatitude of 52.2 degrees +/- 5.7 degrees S for the study area. Comparison of the paleolatitude observed from the Lakang Formation lava flows with that expected from the apparent polar wander paths of India at 130 Ma show a paleolatitude difference of similar to 2.1 degrees (similar to 230 km), indicating that neither a great north-south continental crustal shortening occurred between the Indian craton and the Tethyan Himalaya after 130 Ma, nor that a wide ocean separated them at that time. Comparison with reliable Cretaceous-Paleocene paleomagnetic results observed from the Tethyan Himalaya and the Lhasa terrane indicates that the latitudinal width of the Neo-Tethyan Ocean could have been up to similar to 7000 km at 134-130 Ma and an extension should have existed between the Indian craton and the Tethyan Himalaya during the Late Cretaceous and Paleocene. Furthermore, reliable paleomagnetic results suggest that the India-Asia collision was a dual-collision process, consisting of a first collision of the Tethyan Himalaya with the Lhasa terrane (Asia) at 54.9 +/- 2.3 Ma and a final continent-continent collision of the Indian craton with the Tethyan Himalaya at 40.0 +/- 3.3 Ma. (c) 2015 Elsevier B.V. All rights reserved.