Burma Terrane collision and northward indentation in the Eastern Himalayas recorded in the Eocene ‐ Miocene Chindwin Basin (Myanmar)

Jan Westerweel (1) , Alexis Licht (2) , Nathan Cogné (1) , Pierrick Roperch (1) , Guillaume Dupont-Nivet (1, 3) , Myat Kay Thi (4) , Hnin Hnin Swe (4) , Huasheng Huang (5) , Zaw Win (6) , Day Wa Aung

1 GR - Géosciences Rennes
2 University of Washington [Seattle]
3 University of Potsdam = Universität Potsdam
4 University of Yangon
5 UvA - University of Amsterdam [Amsterdam] = Universiteit van Amsterdam
6 University of Shwebo

The Burma Terrane (Myanmar) played an important role in the India-Asia collision and moved over 2000 km northward on the Indian Plate during the Cenozoic, before colliding with the Asian margin. However, the timing of this collision and its correlation to regional uplift phases, sedimentary provenance and basin development, remain poorly constrained. We report sedimentological, paleomagnetic and geochronological data from the late Eocene to early Miocene strata of the Chindwin Basin in the Burmese forearc, constraining the paleogeographic evolution of the Burma Terrane and the Eastern Himalayan orogen. Our results highlight two unconformities of late Eocene-middle Oligocene and latest Oligocene-early Miocene age, revealing a two stage interaction of the Burma Terrane with the Asian margin during its northward translation. The first unconformity follows rapid ~0.6 m/k.y. subsidence in the Burmese forearc, as shown by magnetostratigraphy. The transition to a fluvial depositional environment and the occurrence of reworked sediments at this first unconformity likely records the commencing collision of India and the northern extent of the Burma Terrane with the Asian margin. The second unconformity shows drastic changes in magnetic properties, mineralogy and provenance, with high-grade metamorphic grains and early Miocene apatite U-Pb and fission track ages indicating that it is coeval to a major deformation phase in Myanmar and the Eastern Himalayan orogen. It likely records the indentation of the Burma Terrane into the Eastern Himalayan collision zone, forming the modern Eastern Himalayan Syntaxis.

Mots clés: Sedimentology; Paleomagnetism; Geochronology; Chindwin Basin; Myanmar; Eastern Himalayan Orogen

Domaines: Tectonique

Jan Westerweel, Alexis Licht, Nathan Cogné, Pierrick Roperch, Guillaume Dupont-Nivet, et al.. Burma Terrane collision and northward indentation in the Eastern Himalayas recorded in the Eocene ‐ Miocene Chindwin Basin (Myanmar). Tectonics, 2020, 39 (10), pp.e2020TC006413. ⟨10.1029/2020TC006413⟩. ⟨insu-02968719⟩