Sequence stratigraphy, depositional systems, and petroliferous plays within a low-accommodation setting: A case study from the Lower Jurassic Sangonghe Formation, Xiayan Rise, Junggar Basin, Northwestern China

The Xiayan Rise (Junggar Basin, NW China) preserves a record of fluvial-deltaic-lacustrine, low-accommodation deposits of the Lower Jurassic Sangonghe Formation. Sequence stratigraphy, depositional systems, and petroliferous plays are investigated with seismic sections, wireline logs, and cores. The results indicate that two third-order sequences and eight fourth-order sequences are recognized. The sequence architecture is controlled by episodic tectonic movement, sediment supply, and climate. In addition, several sedimentary microfacies are identified including braided delta deposits and shore-shallow lacustrine deposits. During the depositional period of J(1)s(2)(2), basin tectonics result in a decrease in water depth and accommodation space. Subaqueous distributary channels are wide and flat which superimpose and connect with each other. During the depositional period of J(1)s(2)(1-2), tectonic movement results in increasing water depth and accommodation space during a phase of warm and humid climate. During the depositional period of J(1)s(2)(1-1), the accommodation space was limited but sediment supply continued which is easy to form forced regression. Low rates of tectonic subsidence and low accommodation space results in the distribution of isolated subaqueous distributary channels which resulted from lacustrine depth. Petroliferous plays comprising source rocks, reservoirs, and seals can be found in LST1 and LST2.