Abstract:

The long-term base level of the rifted basin is controlled by tectonic movements and associated with the evolution of the basin. The rise and fall of the base level influence the depth，area and sedimentary rate of lacustrine. It is recorded in strata and identified by sequence architectures，lacustrine hydrogeologic features and source rocks. The fourth member to the lower second member of the Shahejie Formation comprises one second-order sequence which consists of lowstand system tract (lower-middle Es₄)，transgressive system tract(upper Es₄)，early highstand system tract(lower Es₃)，late highstand system tract(middle and upper Es₃) and regressive system tract(lower Es₂)．Consequently，the lacustrine hydrogeologic features of Dongying palaeolake show five stages which include intermittent lake at the beginning of rift，permanent closed lake through the acceleration of subsidence，deep closed lake during the maximum subsidence，open lake after the slowdown of the subsidence and open lake through the acceleration of the fall of the base level.Additionally，the resource rocks formed in different stages have different characteristics that are shown by the richness and type of organic matter.

Key words: Dongying depression, palaeo-lake, source rock, sequence stratigraphy