Upper Triassic-Jurassic Foreland Sequences of the Ordos Basin in China
Li Sitian, Yang Shigong, Tom Jerzykiewicz, 1995. "Upper Triassic-Jurassic Foreland Sequences of the Ordos Basin in China", Stratigraphic Evolution of Foreland Basins, Steven L. Dorobek, Gerald M. Ross
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The Ordos basin is one of the most important coal and hydrocarbon-bearing sedimentary basins in China. The sedimentary cover, which overlies crystalline basement, is subdivided into seven unconformity-bounded stratigraphic sequences. The Upper Triassic to Upper Jurassic sequences are interpreted to be of foreland basin deposits. Development of a rapidly subsiding foredeep, adjacent to the rising western and southern flanks of the Ordos basin, commenced in late Triassic time during the late phases of the Indosinian Orogeny. A lake which developed in the axial part of the foredeep was a site of sedimentation of organic-rich mudstones which are the major hydrocarbon source in the basin. The main, late Triassic phase of foreland deposition is represented by over 3,000 m of proximal, coarse-grained sediments interfingering with the lacustrine facies. Lacustrine fan deltas and steep-sloped deltas were the main sites of foreland deposition. The depositional history of the Ordos foreland basin includes an overfilled phase in early Jurassic time and changes of source area in late Jurassic time. Unlike the Mesozoic retroarc basins of North America, which developed under a generally unidirectional, west-east compressional regime, the Ordos foreland basin was developed under the influence of transpression related to collision in the Tethys tectonic domain of southwest China and the collision of North China and Yangtze blocks.
Foreland sedimentation was terminated in early Cretaceous time due to a continent-wide shift to an extensional tectonic regime.
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Stratigraphic Evolution of Foreland Basins - A strong case can be made that foreland basins are where the casual links between sedimentation and tectonic events were first recognized, as evidenced by the interpretations of geologists working in classic foreland areas. This Special Publication was derived from a Research Symposium entitled ?Stratigraphic Sequences in Foreland Basins ?held at the AAPG-SEPM joint annual meeting on June, 1992, in Calgary, Alberta, Canada. This volume provides a well-balanced perspective of current research on foreland basin stratigraphy and also serves as another element in the evolving framework that comprises our understanding of foreland basins. Given that so many of earth?s resources are found in foreland basins and that foreland basin strata often provide the only preserved record of the tectonic events that led to basin development, the impetus for continued studies of foreland basin strata should remain for many generations of geologists to come.