Middle Triassic sedimentary evolution in the Upper Yangtze region with implications for the collision between the South and North China Blocks

[Display omitted] •Anisian evaporites were deposited in a lagoon setting of forebulge-backbulge zones.•Forebulge and depocenter in Upper Yangtze were coevally migrated northwestward.•Deposits in Upper Yangtze reflect the collision between SCB and NCB in the Anisian. Middle Triassic marine carbonate...

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Bibliographic Details
Published in:	Journal of Asian earth sciences 2021-12, Vol.222, p.104974, Article 104974
Main Authors:	Xu, Qiang, Li, Ling, Tan, Xiucheng, Xin, Yongguang, Yang, Yu, Li, Minglong, Chen, Xi
Format:	Article
Language:	eng
Subjects:	Collision Forebulge depozone Peripheral foreland basin Stratigraphic framework Upper Yangtze Block
Online Access:	Get full text
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Summary:	[Display omitted] •Anisian evaporites were deposited in a lagoon setting of forebulge-backbulge zones.•Forebulge and depocenter in Upper Yangtze were coevally migrated northwestward.•Deposits in Upper Yangtze reflect the collision between SCB and NCB in the Anisian. Middle Triassic marine carbonate successions deposited on the northwestern Yangtze passive continental margin preserve information about the initial collision between the South China Block (SCB) and the North China Block (NCB). We extracted data from 51 boreholes and 23 outcrops of the Middle Triassic Leikoupo Formation to interpret the spatio-temporal stratigraphic framework, depositional transition, and contractional deformation in the Upper Yangtze region. The sedimentological analysis indicates that the Leikoupo Formation may be divided into nine successions, which were overall deposited in restricted-evaporative marine platform and lagoon environments during the Anisian. From the thickness distributions of each sequence, the Upper Yangtze region is shown to have experienced northwest-southeast horizontal compression and vertical uplift, which drove northwestward migration of the coeval depocenters and marine regression. We propose that the marine deposits of the Leikoupo Formation and the contemporary paleo-uplifts can be considered products of the forebulge and backbulge depozones of a peripheral foreland basin. The Early Triassic passive continental margin in the Upper Yangtze region had thus transformed into a peripheral foreland basin in response to the collision between the SCB and NCB by the Anisian. The northwestward retreat of seawater with synchronous growth of the forebulge further supports the oblique suturing between the two rotating blocks. In response to continuous basin-ward thrusting of the Micangshan-Daba Shan and Longmen Shan belts, new transpressional flexural subsidence developed, leading to the formation of terrestrial deposits in the Late Triassic basin.
ISSN:	1367-9120 1878-5786