--> The tectonic paleogeography of the Tarim Basin (NW China) and its constrains to the hydrocarbon accumulation during the Middle and Late Caledonian

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The tectonic paleogeography of the Tarim Basin (NW China) and its constrains to the hydrocarbon accumulation during the Middle and Late Caledonian


Tarim Basin is the large, very complex, oil-bearing basin in China, surrounded by the Tianshan-Beishan, West Kunlun and Altyn Tagh mountain belts to the north, south, and southeast, respectively. The effects of tectonic movement during a single tectonic phase in this superimposed basin have still been desired to know and can constrain the large scale hydrocarbon accumulation. In this study, we focused on the ternary, basin-scale structural architecture and the properties of two regional unconformities that occur within the basin and its adjacent areas. Here, we outline the structural deformations underlying the unconformity, the distributions and the structural architecture styles of the unconformity, and the stratigraphic sequence and nature of the sedimentary rocks immediately overlying the unconformity. During Middle and Late Caledonian movements, disconformities developed mainly in the northern and the central parts of the basin, and angular unconformities which the beneath layers were monocline and faulted-fold deformations developed in the southern, or the southern and northern parts of the basin, respectively. Before the Silurian, the Low Hotian Uplift, the NE-trending faulted-folded belts of the Tangguzibas Depression and the southern Tazhong Uplift underwent intense deformation related to SE-NW-directed tectonic compression. The SE-NW shortening was twice as much as the N-S shortening. The structural deformation, as well as the depositional facies, formed in response to the subduction and closure of the South Altun Ocean and West Kunlun - Kudi Ocean, and the resulting collisional orogeny. Prior to deposition of Upper Devonian sediments, structural deformation and erosion occurred in two marginal parts of the basin. The extent and intensity of deformation on the NE-trending faults in the Tangguzibas Depression were also reduced but the more NE-trending folds developed in the Manjiaer Depression. The Tabei Uplift experienced uplift and deformation. The closure of the North Altun Ocean and the eastern part of the South Tianshan Ocean were the main driving forces for the tectonic activity. Extensive areas in the northern and southern margins of the basin were uplifted and denudated by orogenic activity as a prelude to the molasse basin that developed in the early Late Devonian in the northeastern and southeastern parts of the basin. We further analyze the sedimentary setting, and reconstruct the tectonic paleogeography during middle and late Caledonian. The results illustrate that the tectonic paleogeography constrain the first and second stage of hydrocarbon accumulation of the Tarim basin.