Meng Jun, Gilder Stuart A, Tan Xiaodong, Li Xin, Li Yalin, Luo Hui, Suzuki Noritoshi, Wang Zihao, Chi Yuchen, Zhang Chunyang, Wang Chengshan
State Key Laboratory of Biogeology and Environmental Geology, School of Earth Sciences and Resources, China University of Geosciences Beijing, Beijing 100083, China.
Department of Earth and Environmental Sciences, Ludwig Maximilians University, 80333 Munich, Germany.
Proc Natl Acad Sci U S A. 2023 Aug 15;120(33):e2305928120. doi: 10.1073/pnas.2305928120. Epub 2023 Aug 8.
The Sangdanlin section in southern Tibet represents a geologic Rosetta stone to constrain the initiation of the India-Asia collision from its sedimentary and paleomagnetic records. However, geoscientists have arrived at fundamentally divergent interpretations surrounding the age of the strata and its paleomagnetic record. Here, we report paleontologic, petrographic, and paleomagnetic data from the Sangdanlin section that recognize the sequence as a thrust complex containing interlaced Barremian-Albian (Early Cretaceous) and Paleocene strata, each separated by thrust faults. Recognizing two complexly interwoven formations of distinctly different ages contradicts a continuous stratigraphic superposition. Assigning an Early Cretaceous, instead of Paleocene, age to the units collected for paleomagnetic data revises paleogeographic models thereby supporting a large (2,000 to 3,000 km) extent of Greater India, with collision initiating at 55 ± 5 Ma in the western Himalayas. A contiguous plate in the Neotethys Ocean precludes that Asia's southern margin was built through a succession of accreted terrains.
西藏南部的桑丹林剖面是一块地质“罗塞塔石碑”，可根据其沉积和古地磁记录来确定印度-亚洲碰撞的起始时间。然而，地球科学家们对该地层的年龄及其古地磁记录得出了截然不同的解释。在此，我们报告了桑丹林剖面的古生物学、岩石学和古地磁数据，这些数据将该层序识别为一个逆冲杂岩，其中包含交错的巴列姆阶-阿尔比阶（早白垩世）和古新世地层，每层均由逆冲断层分隔。识别出两个年龄明显不同且复杂交织的地层与连续的地层叠加相矛盾。将用于古地磁数据采集的单元的年龄确定为早白垩世而非古新世，从而修正了古地理模型，进而支持了大印度（2000至3000公里）的广阔范围，碰撞始于55±5百万年前的喜马拉雅西部。新特提斯洋中的一个连续板块排除了亚洲南缘是由一系列增生地块构成的可能性。
