Abstract:

The sedimentary facies and high-resolution sequence stratigraphy of the Lower Jurassic Sangonghe Formation in the southern part of the Junggar Basin are discussed. It is believed that there are typical deposits of braided-river delta in the Sangonghe Formation. The braided-river delta can be divided into three subfacies. They are braided-river deltaic plain subfacies, braided-river deltaic front subfacies and pro-braided-river delta subfacies. Almost all deposits of the braided-river delta are finer clastic rocks including sandstone, silty sandstone and mudstone, except that a few beds of coarse deposits occur in braided-river channel microfacies. The Sangonghe Formation can be divided into 2 middle-term base-level cycles: MSC₁ and MSC₂. The MSC₁ can be subdivided into 4 short-term base-level cycles: SSC₁, SSC₂, SSC₃ and SSC₄; and the MSC₂ develops incompletely.

Key words:  braided-river delta, high-resolution sequence stratigraphy, Lower Jurassic, the Junggar Basin, the Sangonghe Formation, base-level cycle