关键词: Sunda盆地, 裂陷晚期, 浅水三角洲, 沉积特征, 分布规律

Abstract: Plenty of geological and geophysical data show that shallow-water deltas were developed during the late Oilgocene rifting stage in the Sunda Basin, Indonesia, of which deltaic plains were dominant, but deltaic fronts and prodeltas were less developed. Controlled by shallow basin, gentle slope and rapid current, primary hydrodynamics influencing the shallow-water deltas are surface divergent runoff and vein traction flow dominated by seasonal meandering rivers and braided rivers. Distributary channel and natural levee are main depositional microfacies with abundant sandstone. The former acts as an unloading terminal and a passing channel. The latter gradually accumulates and replaces the inter-river sand bar while transporting. Marsh and coal seam strata are more developed, but they are difficult to shape during gravity deposition. The climate is an important factor affecting the shape of the shallow water delta sand bodies in the late rifting stage. Under the action of thermal diffusion and condensation, the periodic exposure alternating with the rising of the water in the lake basin caused frequent bifurcation, diversion and superposition of the river channels, and developed typical patterns of delta sand bodies, such as leave, teeth, branch, strip.

Key words: Sunda Basin, late rifting stage, shallow-water delta, depositional characteristics, distribution law