71 / 2022-01-23 17:30:48

基于录井和岩心分析的古近系交汇三角洲古地理重建

Eocene, deltas, sandbodies, sedimentary facies, Dongying Depression

Rivers, located a few tens of kilometres apart, built simultaneously two deltas during the Eocene in a large lake that existed in the Dongying Depression, a sub-basin of the Bohai Bay Basin in eastern China. Hundreds of wells were drilled in the delta area and surroundings for hydrocarbon exploration. Borehole logs and core analysis, in combination with seismic-reflection data, allow a detailed reconstruction of the development of both deltas. It appears that both deltas prograded, one from the east to the west and one from the north-east to the south-west, so that they eventually met each other. The progradation occurred mainly by mass flows that built lobes in both forward and lateral directions, so that the deltas eventually merged. Because the rivers had different catchment areas, their sediments have different characteristics, so that the merging process can be reconstructed in detail. Nine phases of the merging process can thus be distinguished. This is of great importance, because merging deltas are well known from present-day areas, but they have only rarely been described from ancient deposits.