Neoproterozoic extensional basins and its control on the distribution of hydrocarbon source rocks in the Yangtze Craton, South China

Hydrocarbon exploration in the Neoproterozoic extensional basins in the Yangtze Craton of South China has made prominent progresses in the past decades. However, the spatial distribution of source rocks across the craton still remains unclear. Here, we use outcrop observations, borehole data, and reflective seismic profiles to investigate the prototype, distribution and sediment infilling of these basins in the Yangtze Craton during the periods of source rock deposition. The basin prototype is categorized based on its tectonic origin and structural-sedimentary feature as follows. (1) During the deposition of the Datangpo Formation, rift basins extensively developed, band are characterized by a series of graben or half graben structures that consist of basin-controlling normal faults. The source rocks in the Datangpo Formation were deposited as the inner shelf basin or deep shelf facies, obtaining high thickness (i.e., 200 m) in the Wuling rift basin. (2) During the deposition of the Doushantuo Formation, the intracratonic rift basin and passive continental margin basin formed. These basins were controlled by syn-depositional faults that inherited the existing rift fault structures. The source rocks of the Doushantuo Formation were deposited as shelf lagoon, slope to deep-water basin facies. (3) During the deposition of the Dengying Formation, the intraplatform rift basin and passive continental margin basin developed with influence of regional tectonic extension. Not only are these basins affected by the preexisting faults, but also by the newly developed syn-depositional faults. The argillaceous source rocks of the Dengying Formation deposited as slope and deep-water basin facies. Further in-depth analyses revealed that a range of mechanisms may have contributed to the formation and distribution of source rocks in the Yangtze Craton, such as the break-up of the Rodinia Supercontinent, paleaolatitudes, glacial-interglacial geological events, basin extension and sedimentary environments. By integrating the distribution of the source rocks and the late tectonic reworking, this study predicts several targets for the source rock distribution in the Yangtze Craton, including in the central Sichuan, northeastern Sichuan, southern Shanxi, western Hubei, northeastern Guizhou-western Hunan, and the northeastern Guangxi-central Hunan areas.