Sedimentary characteristics of the deep fault depression period of the lacustrine basin in northern Gaosheng, western Liaohe depression

Abstract：The lacustrine basin deep fault depression period in the northern area of the western sag of Liaohe depression can be divided into five stages, namely, initial fault depression stage, fast subsiding stage, stable subsiding stage, hard subsiding stage and short time returning stage. During the initial fault depression stage, the alluvial fan, turbidite fan and lacustrine deposit were developed in northern and central parts of the study area. When the fast subsiding stage came, the sedimentary area expanded southward, with the main sedimentary facies being turbidite fan and lacustrine deposit. When the evolution entered into the stable subsiding stage, the whole study area was covered by water, and fan delta, turbidite fan and lacustrine deposit constituted the main deposition forms. The braided stream delta, turbidite fan and lacustrine deposit were the main types at the hard subsiding stage. At last the short time returning stage came, during which the northern part was outcropped and experienced denudation, whereas braided stream delta, fan delta and lacustrine deposit controlled the southern part. It is concluded that the subsiding center, deposition center, deposition styles, sedimentary facies types and their space overlying were all affected by the evolution of the lacustrine basin. At the same time, the development of the sand reservoir and the oil and gas traps were all influenced by the evolution of the lacustrine basin. In general, the structural traps, lithologic traps and combination traps lay in the abrupt slope, while the stratigraphic traps main lay in the slight grade of the lacustrine basin.