EGU21-3685
https://doi.org/10.5194/egusphere-egu21-3685
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Paleomagnetism of the Upper Cretaceous oceanic red beds in southern Tibet, China: Implications for the extent of Greater India at ~75 Ma

Jie Yuan1, Zhenyu Yang2, and Chenglong Deng1
Jie Yuan et al.
  • 1Institute of Geology and Geophysics, Chinese Academy of Sciences, State Key Laboratory of Lithospheric Evolution, China (jieyuan@mail.iggcas.ac.cn, cldeng@mail.iggcas.ac.cn)
  • 2College of Resources, Environment and Tourism, Capital Normal University, Beijing 100048, China (zhenyu.yang@cnu.edu.cn)

The extent of Greater India with precise and accurate chronological control is a key issue that concerns the spatio-temporal pattern and tectonic models of the India-Asia collision. Here we carried out a detailed magnetostratigraphic and paleomagnetic study on the Upper Cretaceous oceanic red beds (CORBs) (Chuangde Formation) exposed in the Tethyan Himalaya terrane. The high temperature (650‒690°C) magnetic components are isolated from two separated sections at Cailangba and display both normal and reverse polarities, which were used to construct magnetic polarity sequences of the sections that can be subsequently correlated to the geomagnetic polarity time scale (GPTS) to better estimate the age of the rocks. With the aid of previously published biostratigraphy by Chen et al. (2011, Sedimentary Geology), the polarity magnetozones of the Cailangba B section are correlated to chron C32r.2r (74.3–74.0 Ma) and the upper part of chron C33n (79.9–74.3 Ma), and the single normal polarity magnetozone of the Cailangba A section is correlated to the upper part of chron C33n (79.9–74.3 Ma). As a result, the CORBs in the Cailangba A and B sections represent the time interval of 76.2–74.0 Ma by magnetobiostratigraphy. Two independent methods of inclination shallowing correction were tested, which all indicate a bias inclination of ~70%. After inclination shallowing correction, the mean inclination increased to ‒35.0°, giving what we propose to be a high-quality Late Cretaceous paleopole of 40.8°N/256.3°E, A95 =1.8°. Our findings indicate that the Indian passive continental margin was situated at a paleolatitude of 19.4° ± 1.8°S at ~75 Ma. These data suggest that Greater India extended about 715 ± 374 km farther north from the present northern margin of India in the Late Cretaceous, implying a latitudinal width of 3641 ± 308 km for the Neo-Tethys Ocean that still separated the Lhasa terrane of southern part of the Asian plate and the Greater India.

How to cite: Yuan, J., Yang, Z., and Deng, C.: Paleomagnetism of the Upper Cretaceous oceanic red beds in southern Tibet, China: Implications for the extent of Greater India at ~75 Ma, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3685, https://doi.org/10.5194/egusphere-egu21-3685, 2021.

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