Precollisional Latitude of the Northern Tethyan Himalaya From the Paleocene Redbeds and Its Implication for Greater India and the India‐Asia collision
2019
Yang, Tianshui | Jin, Jingjie | Bian, Weiwei | Ma, Yiming | Gao, Feng | Peng, Wenxiao | Ding, Jikai | Wang, Suo | Zhang, Shihong | Wu, Huaichun | Li, Haiyan | Yang, Zhenyu
The precollisional paleolatitude of the Tethyan Himalaya is essential to constrain the India‐Asia collision, the size of Greater India, and the Neotethyan paleogeography. However, reliable Late Cretaceous‐Paleocene paleomagnetic datasets are still scarce because of serious remagnetization. Here we report the first redbed‐based paleomagnetic results from the Paleocene (60‐58 Ma) redbeds in the Saga area of the northern Tethyan Himalaya. The tilt‐corrected site‐mean direction obtained from 36 paleomagnetic sites is D=178.7°, I=9.5° with ɑ₉₅=5.4°, corresponding to a paleopole at 55.9°N, 267.6°E with dp/dm=2.8°/5.5° and a paleolatitude of 4.8°±2.8°S for the study area (29.3°N, 85.3°E). The site‐mean inclination increased from 9.5 to 14.9° after the anisotropy‐based inclination shallowing correction, leading to corresponding paleolatitudes increasing from 4.8 to 7.6°S. This reliable paleomagnetic dataset passes positive fold tests and supports that the northern Tethyan Himalaya was located at 6.3±4.3°S during 60‐58 Ma. Comparison with the coeval paleolatitudes expected from the Indian craton indicates that a north‐south crustal shortening of 3.1±5.5° (340±610 km) occurred between the Indian craton and the northern Tethyan Himalaya after 59 Ma, and no wide ocean extended between them after the Latest Jurassic. Our new Paleocene results together with reliable Cretaceous paleomagnetic results from the Lhasa terrane show that the India‐Asia collision occurred at 47.1±4.5 Ma.
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