Anisotropy of Magnetic Susceptibility (AMS) Analysis of the Gonjo Basin as an Independent Constraint to Date Tibetan Shortening Pulses

Shihu Li; Douwe J.J. van Hinsbergen; Zhongshan Shen; Yani Najman; Chenglong Deng; Rixiang Zhu

doi:10.1029/2020GL087531

Anisotropy of Magnetic Susceptibility (AMS) Analysis of the Gonjo Basin as an Independent Constraint to Date Tibetan Shortening Pulses

Shihu Li^*
, Douwe J.J. van Hinsbergen
, Zhongshan Shen
, Yani Najman
, Chenglong Deng
, Rixiang Zhu

^*Corresponding author for this work

Chinese Academy of Sciences
University of Chinese Academy of Sciences
Lancaster University

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

The Tibetan Plateau accommodated major upper crustal shortening during Indian Plate oceanic and continental lithosphere subduction. Deciphering whether shortening was continuous or episodic, and how it correlates to major geodynamic changes is challenging. Here we apply anisotropy of magnetic susceptibility (AMS), a sensitive synsedimentary strain indicator, to a ~3 km thick magnetostratigraphically dated sedimentary section (69–41.5 Ma) in eastern Tibet. AMS shows “earliest deformation” fabrics from 69–52 Ma, followed by a sudden change to “pencil structure” fabrics with increasing anisotropy degree at ~52 Ma, dating a sudden increased synsedimentary shortening strain. This change coincides with enhanced sedimentation rates and synsedimentary vertical-axis rotations of the Gonjo Basin, suggesting a causal link to a marked India-Asia convergence rate deceleration. We show that AMS analysis provides a strong tool to distinguish between climatic and tectonic causes of sedimentological change and is an asset in identifying discrete tectonic pulses in intensely deformed terrane.

Original language	English
Article number	e2020GL087531
Number of pages	11
Journal	Geophysical Research Letters
Volume	47
Issue number	8
DOIs	https://doi.org/10.1029/2020GL087531
Publication status	Published - 28 Apr 2020

Funding

This work was funded by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA13010106) and the National Natural Science Foundation (41888101, 41690112, and 41761144065). S.?L. acknowledges the further support from the Royal Society-K.?C. Wong International Fellowship at Lancaster University. D.?J.?J.?v.H. acknowledges NWO Vici Grant 865.17.001. We would like to thank the Editor Dr. Monika Korte and two anonymous reviewers for their constructive comments, which helped us to improve the manuscript. The original AMS data presented in this paper can be accessed through the public domain repository Zenodo (at https://doi.org/10.5281/zenodo.3666760).

Keywords

Anisotropy of magnetic susceptibility
climatic and tectonic
Gonjo Basin
Shortening
Tibetan Plateau

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2020GL087531Final published version, 5.86 MBLicence: Taverne

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title = "Anisotropy of Magnetic Susceptibility (AMS) Analysis of the Gonjo Basin as an Independent Constraint to Date Tibetan Shortening Pulses",

abstract = "The Tibetan Plateau accommodated major upper crustal shortening during Indian Plate oceanic and continental lithosphere subduction. Deciphering whether shortening was continuous or episodic, and how it correlates to major geodynamic changes is challenging. Here we apply anisotropy of magnetic susceptibility (AMS), a sensitive synsedimentary strain indicator, to a \textasciitilde{}3 km thick magnetostratigraphically dated sedimentary section (69–41.5 Ma) in eastern Tibet. AMS shows “earliest deformation” fabrics from 69–52 Ma, followed by a sudden change to “pencil structure” fabrics with increasing anisotropy degree at \textasciitilde{}52 Ma, dating a sudden increased synsedimentary shortening strain. This change coincides with enhanced sedimentation rates and synsedimentary vertical-axis rotations of the Gonjo Basin, suggesting a causal link to a marked India-Asia convergence rate deceleration. We show that AMS analysis provides a strong tool to distinguish between climatic and tectonic causes of sedimentological change and is an asset in identifying discrete tectonic pulses in intensely deformed terrane.",

keywords = "Anisotropy of magnetic susceptibility, climatic and tectonic, Gonjo Basin, Shortening, Tibetan Plateau",

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AU - Li, Shihu

AU - van Hinsbergen, Douwe J.J.

AU - Shen, Zhongshan

AU - Najman, Yani

AU - Deng, Chenglong

AU - Zhu, Rixiang

PY - 2020/4/28

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N2 - The Tibetan Plateau accommodated major upper crustal shortening during Indian Plate oceanic and continental lithosphere subduction. Deciphering whether shortening was continuous or episodic, and how it correlates to major geodynamic changes is challenging. Here we apply anisotropy of magnetic susceptibility (AMS), a sensitive synsedimentary strain indicator, to a ~3 km thick magnetostratigraphically dated sedimentary section (69–41.5 Ma) in eastern Tibet. AMS shows “earliest deformation” fabrics from 69–52 Ma, followed by a sudden change to “pencil structure” fabrics with increasing anisotropy degree at ~52 Ma, dating a sudden increased synsedimentary shortening strain. This change coincides with enhanced sedimentation rates and synsedimentary vertical-axis rotations of the Gonjo Basin, suggesting a causal link to a marked India-Asia convergence rate deceleration. We show that AMS analysis provides a strong tool to distinguish between climatic and tectonic causes of sedimentological change and is an asset in identifying discrete tectonic pulses in intensely deformed terrane.

AB - The Tibetan Plateau accommodated major upper crustal shortening during Indian Plate oceanic and continental lithosphere subduction. Deciphering whether shortening was continuous or episodic, and how it correlates to major geodynamic changes is challenging. Here we apply anisotropy of magnetic susceptibility (AMS), a sensitive synsedimentary strain indicator, to a ~3 km thick magnetostratigraphically dated sedimentary section (69–41.5 Ma) in eastern Tibet. AMS shows “earliest deformation” fabrics from 69–52 Ma, followed by a sudden change to “pencil structure” fabrics with increasing anisotropy degree at ~52 Ma, dating a sudden increased synsedimentary shortening strain. This change coincides with enhanced sedimentation rates and synsedimentary vertical-axis rotations of the Gonjo Basin, suggesting a causal link to a marked India-Asia convergence rate deceleration. We show that AMS analysis provides a strong tool to distinguish between climatic and tectonic causes of sedimentological change and is an asset in identifying discrete tectonic pulses in intensely deformed terrane.

KW - Anisotropy of magnetic susceptibility

KW - climatic and tectonic

KW - Gonjo Basin

KW - Shortening

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Anisotropy of Magnetic Susceptibility (AMS) Analysis of the Gonjo Basin as an Independent Constraint to Date Tibetan Shortening Pulses

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