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In the transitional period between the Middle and the Late Triassic, the Indochina orogeny caused two tectonic events in South China: (1) the formation and uplift of the Qinling‐Dabie orogenic belt along the northern margin of the South China Plate, due to its collision with the North China Plate; and 2) the development of a 1300‐km‐wide intra‐continental orogen in the southeastern part of the South China Plate, which led to a northwestward movement of the foreland thrust‐fold zone. These tectonic events resulted in the ending of the Yangtze Platform, and were a stable paleogeographic factor from the Eidacaran to the end of the Middle Triassic. This platform was characterized by the widespread development of shallow‐water carbonates. After the end of the Yangtze Platform, the upper Yangtze foreland basin (or Sichuan foreland basin) was formed during the Late Triassic and became a accumulation site of fluvial deposits that are composed of related strata of the Xujiahe Formation. In western Sichuan Province, the Xujiahe Formation overlies the Maantang Formation shallow‐water carbonate rocks of the Xiaotangzi Formation siliciclastic rocks (from shelf shales to littoral facies). The sequence‐stratigraphic framework of the Upper Triassic in the upper Yangtze foreland basin indicates a particular alluvial architecture, characterized by sequences composed of (1) successions of low‐energy fluvial deposits of high‐accommodation phases, including coal seams, and (2) high‐energy fluvial deposits of low‐accommodation phases, including amalgamated river‐channel sandstones. The spatial distribution of these fluvial deposits belonging to the Xujiahe Formation and its relative strata is characterized by gradual thinning‐out, overlapping, and pinching‐out toward both the east and south. This sedimentary record therefore expresses a particular sequence‐stratigraphic succession of fluvial deposits within the filling succession of the foreland basin. The sequence‐stratigraphic framework for the Upper Triassic in the Upper Yangtze region provides a record of the end of the Yangtze Platform and the formation of the upper Yangtze foreland basin.

The Permian Lopingian in the Dianqiangui Basin and its adjacent areas is marked by the coal measures of the Wuchiapingian and the carbonate strata of the Changhsingian stages. For the Lopingian of the Dianqiangui Basin and its adjacent areas, the diversity of sedimentary facies and the obviousness of facies change provide an advantaged condition on a study of sequence stratigraphy. Approximately, the Wuchiapingian stage constitutes a third-order sequence and the Changhsingian stage forms another. For the Wuchiapingian stage in the study area, coal-measures were developed on the attached platform and, in addition, a special coal-measure that is composed of both limestone beds and coal beds was also developed in the central part of some isolated platforms. Grain-bank grainstones and packstones were formed on the margin of the attached platform as well as in the windward part of isolated platforms. For the Changhsingian stage in the study area, open-platform limestones were formed on the attached platform, while sponge-reef limestones were developed both on the margin of the attached platform and on the isolated platforms. The Lopingian Series is a set of basin-facies muddy shales with interbeds of silicalites in the inter-platform basin, which appears a set of the large-thick coarse clastic strata of molasses covering direct the deep-water strata from the Devonian to the Permian Yangsingian in the Qinzhou-Fangcheng region in the southern part of the study area. All of these features indicate the complexity of temporal-spatial facies-changes. Sequence-stratigraphic frameworks could be established, which would illustrate two types of facies-changing surfaces and diachronisms in the stratigraphic records, based on the combination of both biostratigraphic and chronostratigraphic materials and the regularity reflected by temporal evolutionary succession of sediments as well as spatial distributional patterns of sedimentary facies. Ultimately, features of sedimentary succession and palaeogeographical evolution of the Permian Lopingian in the study area are revealed clearly in a series of the panel diagrams of sequence-stratigraphic frameworks and the outline maps showing the sedimentary-facies and palaeogeography. The Permian Lopingian formed by two third-order sequences differs from the stratigraphy of the same era characterized by the constant regression along Euramerica. Most specially, if the end-Guadalupian mass-extinction event is genetically related to a regressive event represented by the unconformity of the first episode of the Dongwu movement in the study area, the mass-extinction event at the turn from the Permian to the Triassic is genetically related to a rapid transgressive event reflected by the drowning unconformity in the study area. These phenomena might reveal a complex relationship between mass-extinction events and transgressive-regressive events.

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