The sedimentation of fine- grained gravity flows is an important sedimentation style. It can transport fine- grained clasts and organic matter from shallow water to deep lake to form “sweet spots” of shale oil and good source rocks. Research on sedimentary features of fine- grained gravity flows has great significance for evaluation of shale oil in lacustrine basins. During the Fengcheng Formation period（P1f）, a sub- lacustrine fan system was deposited in the salinized deep lake sub- environment of the Mahu depression. Eight kinds of lithofacies associations （LA） are identified in fan fringe sub- environment based on core observations. LA1: the LA of fine- grained concentrated density flow, fine- grained transitional flow, and fine- grained debris flow deposits; LA2: the LA of fine- grained hyperpycnal flow deposits; LA3: the LA of fine- grained concentrated density flow and fine- grained debris flow deposits; LA4: the LA of fine- grained concentrated density flow, mud flow and fallout deposits in quiet water; LA5: the LA of fine- grained transitional flows and fine- grained debris flow deposits; LA6: the LA of fine- grained debris flow and mud flow deposits; LA7: the LA of fine- grained debris flow and turbidity wake flow deposits; LA8: LA of fine- grained lower transitional plug flow, fine- grained upper transitional plug flow, and quasi- laminar plug flow deposits. The LA of coarse- grained concentrated density flow and fine/coarse- grained debris flow deposits are in proximal sub- lacustrine fan sub- environment. These LAs are the result of transformation of sediment gravity flows. They belong to incomplete hybrid event beds and can constitute a complete hybrid event bed. The salinized lacustrine basin and addition of deep hot liquid and tuffaceous made the sub- lacustrine fan system with dolomite, shortite, sodalite and searlesite. The dolomite is penecontemporaneous, generated by chemically precipitated calcite during the penecontemporaneous and shallow burial stages. Shortite, sodalite and searlesite may come from deep hot brines. The coarse- grained gravity flow deposits in proximal sublacustrine fan are in tight oil zone, while the fine- grained gravity flow deposits in fan fringe are shale oil zone. The fine- grained gravity flow deposition and the development of the organic- rich layer in the lake basins are affected by lake level changes. The rise of lake level is favorable for the development of organic- rich mudstone, while the fall of lake level is more conducive to the development of fine- grained gravity flow deposits. Fine- grained gravity flow deposits can form “sweet spots” for shale oil.