Lacustrine storm deposits of Triassic Huangshanjie Formation in northern Tarim Basin

Based on core observation and grain analysis, the lacustrine storm deposits in Huangshanjie Formation in northern Tarim Basin were studied. The results show that they are mainly composed of middle-fine sandstone and siltstone, being short of coarse sandy conglomerate with bounder clay locally developed. Several typical storm sedimentary structures are recognized, including surface of scour, hommocky cross stratification, graded bedding, wave-ripple bedding, wavy bedding, deformation structures, as well as life-escaping structures. Grain-size probability curves show obvious two-section pattern, with saltation population mainly developed. The ideal storm sequence of this area is a Bouma-like sequence, and from bottom to top consists five segments, namely graded bedding (Sa), parallel bedding (Sb), hummocky cross stratification (Sc), wave-ripple or wavy bedding (Sd), mudstone segment (Se), with Sabde, Sace, Scde and Sde sequences commonly developed. There are two provenances for storm deposits in this area, of which one comes from northwestern Kalpin Uplift, and the other comes from northeastern Kuruketage Uplift. Judging from the sedimentary features and its relationship with provenances, the tempestites of this area are transtional or distal tempestite.