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The generally accepted foreland interpretation of the Nanpanjiang basin has been regarded as providing support for the hypothesized Indosinian collision between the South China and Indochina blocks, and it has led to the long‐standing view that crustal shortening dominated the Triassic intracontinental development of South China. Here, we examine the stratigraphic architecture, magmatism and gross structural features of the Nanpanjiang basin. Outcrop studies indicate that a north‐stepping axial turbidite system was confined by intrabasinal faults, the active development of which is indicated by mass‐transport complexes. Field mapping combined with U–Pb dating of baddeleyite and zircon reveals that magmatism in the southern part of the basin coincides with a distinct episode of bimodal volcanism from ca. 244 to 242 Ma, and is unrelated to the middle Permian Emeishan plume. Differences in tectonic subsidence between hanging‐wall and footwall blocks, as that has been quantified by the backstripping of composite sections, show that synsedimentary dip slip along intrabasinal faults was of normal sense. Meanwhile, a role for strike‐slip deformation is registered by the left‐lateral offset of middle Permian and Middle Triassic piercing points and the exceptional preservation in outcrop of syndepositional negative flower structures. For these reasons, therefore, the pre‐Norian Triassic Nanpanjiang basin is thought to represent a transtensional back‐arc setting, a result that leads to an unresolved paradox: in adjacent parts of South China to the east, coeval development involves crustal thickening, nonmarine sedimentation and granitic plutonism. A new lateral decoupling model consistent with palaeomagnetic evidence for large‐scale block rotation is tentatively proposed here as a working hypothesis to explain the observed intracontinental evolution of South China during the Triassic assembly of eastern Asia. We propose that such decoupling may relate in part to the configuration of inherited crustal weaknesses. [ABSTRACT FROM AUTHOR]

The Hailar Basin is located in the northern portion of NE China and preserves relatively complete Middle Jurassic to Cretaceous volcanic and clastic successions. The understanding of the basin's Mesozoic stratigraphic development can help reveal Mesozoic tectonic complexity in NE China. This study focuses on Mesozoic sequences of the Hailar Basin based mainly on interpretations of seismic profiles and logging data. Three tectono‐stratigraphic sequences are dividable, the pre‐Mesozoic, the Middle Jurassic to Lower Cretaceous, and the Upper Cretaceous successions, respectively. Two angular unconformities separate the three sequences, with one below the Middle Jurassic and the other atop the Lower Cretaceous. Noticeable is the absence of the two angular unconformities in the Jurassic to Lower Cretaceous sequence, which are usually observed in the northern North China Block. Instead, a disconformity occurs between the Jurassic and Lower Cretaceous. The absence of angular unconformities in the Hailar Basin implies that this region had not been affected by crustal shortening or the Yanshanian Orogeny that had strongly influenced the northern North China Block in the late Mesozoic. It is concluded that the closure of the Mongol–Okhotsk Ocean exerted little impact on the continent on the south, and flat subducting of the Palaeo‐Pacific Plate might have been responsible for the occurrence of the Yanshan Orogeny. [ABSTRACT FROM AUTHOR]