Eocene Rotation of the Northeastern Central Tibetan Plateau Indicating Stepwise Compressions and Eastward Extrusions. Issue 17 (7th September 2020)

• Record Type: Journal Article
• Authors: Zhang, Weilin; Fang, Xiaomin; Zhang, Tao; Song, Chunhui; Yan, Maodu
• Is Part Of: Geophysical research letters. Volume 47:Issue 17(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-07
• Subjects: Magnetostratigraphy -- Paleomagnetic rotation -- Nangqian Basin -- northeastern central Tibetan Plateau -- compression and extrusion; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL088989
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: When and how the TP underwent uplift and deformation are still under heated debate. We present paleomagnetic evidence for the NB in the northeastern central TP to help decipher the potential plateau deformation mechanism. Magnetostratigraphy with zircon U‐Pb age of volcanic rock demonstrates that the NB basin deposited during 52.5–35.0 Ma. Paleomagnetic declinations indicate that the basin experienced counterclockwise rotation of 25.9 ± 7.2° during 52–46 Ma and clockwise rotation of 24.4 ± 9.7° during 41–35 Ma, which coexisted with the intrusion and explosion of volcanic rocks at 51–46 and 39–35 Ma. We proposed a stepwise compression and extrusion model to interpret the basin deposition, rotation, and volcanism by northward compression and eastward extrusion of the eastern Lhasa and Qiangtang Blocks (Proto‐TP) in relation to the Sichuan Basin as early response to the India‐Asia collision. Plain Language Summary: How the Tibetan Plateau (TP) adjusted its inner crustal thickening and tectonic deformation during the India‐Asia collision is still in hot debate, for example, through lateral extrusion or continuous distribution. The Nangqian Basin (NB) is located in the bending (transitional) part from an east‐west tectonic area in the central TP to a north‐south tectonic area in the eastern and southeastern TP. It is an ideal location to provide abundant tectonic evidences for the plateau deformation and uplift models. We report a detailed paleomagnetic dating of the Paleogene sedimentary sequence from the NB with a complete paleomagnetic rotation analysis. Radiometric and magnetostratigraphic dating suggested that the NB commenced its deposition at 52.5 Ma and ended at 35.0 Ma. Paleomagnetic declination data reveal a change of rotation sense of the NB, from a counterclockwise rotation of 25.9° at 52–46 Ma to a clockwise rotation of 24.4° at 41–35 Ma. Integrated with other lines of geological evidence, we believe that the Eocene deformation, rotation, and uplift of the south and east central TP in response to the early India‐Asia collision can be explained by stepwise compressions and eastward extrusions. Key Points: Magnetostratigraphic results demonstrate that the Early Cenozoic sedimentary sequence of the Nangqian Basin yields ages of 52.5–35.0 Ma Declination data indicate change of rotation in the Nangqian Basin from counterclockwise during 52–46 Ma to clockwise during 41–35 Ma The Eocene deformation, rotation, and uplift of the east central Tibetan Plateau favor the compression and extrusion model