Remagnetization of Lower Cretaceous Limestones in the Western Tethyan Himalaya and Its Tectonic Implications for the India‐Asia Collision

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Abstract
The drift history of the Tethyan Himalaya provides key constraints on the India‐Asia collision, Himalayan‐Tibetan orogenesis, and associated global climate change. Here we present rock magnetic, petrographic, geochronologic, and paleomagnetic results of the Bolinxiala Formation limestones in the western Tethyan Himalaya. In situ calcite U‐Pb dating and biostratigraphy indicate that the Bolinxiala Formation limestones were formed during the Early Cretaceous (∼125–100 Ma), not Middle Jurassic as previously thought. The site‐mean direction for the 23 sites is D g = 23.3°, I g = +10.0°, k g = 40.1 and α 95 = 4.8° in situ and D s = 20.8°, I s = +19.0°, k s = 67.2 and α 95 = 3.7° after tilt‐correction, yielding a paleomagnetic pole position at 61.6°N, 212.9°E with A 95 = 2.7°, corresponding to a paleolatitude of 10.3° ± 2.7°N. A positive fold test indicates a prefolding origin. When compared with reliable Cretaceous–Eocene paleopoles from the western Tethyan Himalaya, we suggest that the Bolinxiala Formation limestones likely underwent remagnetization during ∼54–49 Ma. Petrologic evidence, including the presence of framboidal oxides derived from sulfides (primarily pyrite) and calcite veins, supports chemical remanent magnetization as the primary mechanism responsible for the remagnetization. Our new results, combined with reliable Cretaceous paleomagnetic data from the western Lhasa terrane, indicate that the western part of the India‐Asia collision occurred no later than ∼54–49 Ma.
Funding Information
  • National Natural Science Foundation of China (92155203)
  • National Natural Science Foundation of China (42474098)
  • National Natural Science Foundation of China (42488201)
  • National Natural Science Foundation of China (42072257)

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