Relationship between River-Mouth Depositional Processes and Delta Architectures, Huangqihai Lake, Inner Mongolia, North China

Shunli, Li; Xinghe, Yu; Li, Shengli; Steel, Ronald J.; Olariu, Cornel

Huangqihai Lake, a modern lacustrine rift basin located in the south of Inner Mongolia, Northern China. The lake has an area of 110 km2 and variable depth between 2 m to 15 m in the past, and dries out in present. Three small (4-8 km2) deltas (Bawanghe, Luzimiao and Dahewan) on the margins of Huangqihai Lake were surveyed to investigate differences in delta architectures produced by different river-mouth regimes using aerial photographs, field trenches and sediment samples. Sedimentary logs and cores were collected from 37 trenches (grid spacing approximately 300 m on the top of the three deltas), allowing detailed mapping of sedimentary facies. Three dimension delta architecture models were generated utilizing Petrel software.

Sediment dispersal and accumulation patterns from the three deltas were governed by three basic river effluent regimes and by wave processes which have been recognized based on the delta morphologies. Dahewan delta, is friction-dominated, has a very shallow (2-3 m) front with 3 delta lobes and 6 distributary channels. Luzimiao delta front which is inertia-dominated has one elongated lobe, and exhibits limited lateral spreading resulting in narrow (100 m) river-mouth bars. Bawanghe delta front, is buoyancy-dominated, has 3 major lobes with a few elongate distributaries with parallel banks, and few bifurcations. Trenches on the top of the deltas and the 3-D models reveal common features such as small (1 m thick) channels with dm thick cross-strata, alternation of cm to dm thick sand and mud beds. However, there are also significant differences with the Dahewan (friction dominated) having the sandiest delta front and the Luzimiao (inertia dominated) the muddiest delta front. The morphology and facies differences between the three delta types coming in the same lake is most likely controlled by the river discharge characteristics and the sediment load type. The 3-D models of the lacustrine deltas despite being relative small in dimensions are at the scale of some of the lacustrine reservoirs and provide insights into the complexities if the deltaic reservoirs formed within the same basin.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013