Sedimentary characteristics of shallow-water braided delta of the Jurassic, Junggar basin, Western China

Abstract

The shallow-water braided deltas are hot topic in global sedimentology. In China, this depositional environment forms an important reservoir and exploration target within the basins. Therefore, geological and sedimentologic settings of the Jurassic shallow-water braided deltas in the Junggar basin of western China have attracted much attention in recent years based on the comprehensive analysis of geological and geophysical data acquired. These braided deltas deposited in the shallow Junggar lacustrine basins with gentle slope gradients and prograded towards to the central basin from northeast to southwest (more than 10km). This kind of Jurassic delta was characterized by coarse grain-size (sand to pebble), large cross-beddings, discontinuous fining-upward successions vertically, high percentage of sandstone ratios (up to 70%), very unique distributary channels with few distributary mouth bars, and seismic facies of shingled with a progradational reflections. Based on the detailed research on basin evolution and sedimentary characteristics of deltaic sub-facies, this paper presents the relationship between the shallow-water braided deltaic deposition and lithologic traps predicted to be the favorable and explorable lithological traps in the Junggar Basin.