Formation process and internal architecture of wave dominated beach-bar along the lake shore: insights from a flume experiment

Beach-bar is a common kind of lacustrine sedimentation distributed in the shallow water area. To date, a large amount of oil and gas resource was explored within beach-bar reservoir. However, the depositional mechanism and internal architecture of the beach-bar system are still to be discovered. In this paper, to reveal the formation of a beach-bar system, an experimental beach-bar system was produced through a flume experiment controlled by a simulation plan with three stages. To reproduce a beach-bar system along the lake shore, a bedform with a pre-existing delta was utilized. Based on the morphology data set scanned during the experiment, the sedimentary process and internal architecture of the experimental beach-bar system was discovered. According to the experiment, artificial wave is the key driver force to reform the pre-existing sediments along the lakeshore. A higher water level associated with stronger wave strength, which produced the main deposit, can accelerate the formation process of beach-bar system and create larger scale beach-bars. In contrast, the lower water level and weaker wave can only slightly modify the initial bedform. In the first stage of the experiment, the pre-existing delta was gradually abandoned; sediment of the pre-existing delta was eroded and transported to sides of the pre-existing delta. In the second stage, the pre-existing delta was totally abandoned. The water level and wave intensity kept the same as the first stage; the limited wave intensity slightly reformed the bedform and failed to produce beach-bar system. In the third stage, higher water level and associated stronger wave intensity produced an ideal experimental beach-bar system. In the experiment, the sediment was overall transported to the lake shore. The experimental beach-bar system can be divided into three parts which have different sedimentary characteristics. The largest scale bar with aggraded thick accretions deposited in the proximal part of the beach-bar system. In the middle part of the system, thin and widely distributed beach deposited. The distal part of the system was characterized by arc-shaped and parallelly arranged ridge-like bars.