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Basin growth strata and its structural control in the region of Zhangjiakou, North Hebei, China

Science China Press

The timing, tectonic setting, and deforming kinematics of the "Yanshanian Movement" are still matters of controversy. They are the key issues related to destruction of North China craton, and dynamic linkage of tectonism of Northeast Asian continental margin to West Pacific plate subduction. A recently-published paper, taking the region of Zhangjiakou in Yanshan Mountains as an example, identifies five types of growth strata developed in different growth structures, and suggests the "pair" of basement-involved fold-thrust belt and flexure basin might have been controlled by flat subduction of the western Paleo-Pacific slab from the Jurassic to the Early Cretaceous.

the majority of China geologists have accepted the concept of "Yanshanian movement" as a proxy for tectonism in the Mesozoic. The first stage started in the Middle and Late Jurassic (approximately 174-154 Ma), followed by the second stage in the Late Jurassic to Early Cretaceous (approximately 161-136 Ma), and the third stage in the Cretaceous. However, the main processes of the Yanshanian movement, including structural processes, deformation mechanisms and tectonic properties from the Jurassic to Cretaceous are unclear. Sediments that filled the intramontane basins in the Yanshan belt perfectly record the history of "Yanshanian Movement" and the tectonic background of these basins. Recognizing syn-tectonic sedimentation, clarifying its relationship with structures, and accurately defining strata ages to build up a correct chronostratigraphic framework are the key points to further reveal the timing and kinematics of tectonic deformation in the Yanshan belt from the Jurassic to the Early Cretaceous.

The researchers applies both tectonic and sedimentary methods on the fold-and-thrust belt and intramontane basins in the Zhangjiakou area, which is located at the intersection between the western Yanshan and northern Taihangshan. The research results suggests that the five types of growth strata developed in different growth structures: fold-belt foredeep type, thrust-belt foredeep type, fault-propagation fold-thrust structure type, fault-bend fold-thrust structure type, and fault-bend foldthrust plus fault-propagation fold composite type. The reconstructed "source-to-sink" systems of Late Triassic to Early Jurassic, Middle Jurassic and Late Jurassic to early Early Cretaceous times, which are composed of a fold-and-thrust belt and flexure basins, imply that the "Yanshanian Movement" in the study area started in the Middle Jurassic. During Middle Jurassic to early Early Cretaceous times, there have been at least three stages of fold-thrust events that developed "Laramide-type" basement involved fold-thrust structures and small-scale intramontane broken "axial basins". The "pair" of basement-involved fold-thrust belt and flexure basin might have been controlled by foreward and flat subduction of the western Paleo-Pacific slab from the Jurassic to the Early Cretaceous.

This research not only has an important significance for our revealing the destruction process and mechanism of the North China Craton, but also provides important and basic geological evidence for determining the tectonic property of Northeast continental margin, which includes the Yanshan-Taihangshan Mountains, and its dynamic linkage to the western Pacific plate subduction.

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This research was funded by National Natural Science Foundation of China (Nos. 41572189 & 91114203), National Key R&D Plan (No. 2017YFC0601405), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (No. XDB18000000).

See the article: Liu S, Lin C, Liu X, Zhuang Q. 2018. Syn-tectonic sedimentation and its linkage to fold-thrusting in the region of Zhangjiakou, North Hebei, China. Science China Earth Sciences, 61, https://doi.org/10.1007/s11430-017-9175-3

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