Favorable lithofacies types and genesis of marine-continental transitional black shale: A case study of Permian Shanxi Formation in the eastern margin of Ordos Basin, NW China

WU Jin,WANG Hongyan,SHI Zhensheng,WANG Qi,ZHAO Qun,DONG Dazhong,LI Shuxin,LIU Dexun,SUN Shasha,QIU Zhen

Fig. 4. Thin sections showing the typical shale lithofacies of the Permian Shanxi Formation in the eastern margin of the Ordos Basin. (a) C-L: silt-bearing shale with charcoal metasomatized by siderite, Well Daji51, 2277.55 m; (b) C-L: charcoal and silt bearing shale showing bioturbation, Well Daji51, 2277.65 m; (c) S-L: charcoal-bearing shale with super fine laminae, Well Daji51, 2288.82 m; (d) S-L: silty shale with lenticular laminae, Well Daji51, 2292.12 m; (e) S-L: silt-bearing shale showing bioturbation, Well Daji51, 2292.81 m; (f) S-M: black shale containing dolomite laminae, Well Daji51, 2296.59 m; (g) S-M: black shale containing dolomite laminae, Well Daji51, 2296.75 m; (h) S-M: siderite-bearing black shale, Well Daji3-4, 2142.50 m; (i) M-M: calcareous shale containing rich bioclasts, Well Daji51, 2298.23 m; (j) M-M: silica-rich bioclastic shale, Well Daji51, 2298.23 m; (k) M-M: silica-rich bioclastic shale containing sponge spicules, Well Daji3-4, 2145.57 m; (l) S-H: black shale containing bioclasts with argillized foraminifera that retain their shape, Well Daji3-4, 2143.32 m; (m) S-H: bioclastic dolomitic shale, Well Daji51, 2297.67 m; (n) S-H: bioclastic dolomitic shale, Well Daji51, 2297.25 m; (o) S-H: black shale containing bioclasts, Well Daji51, 2303.57 m; (p) C-H: high-carbon shale containing argillaceous strips, Well Daji51, 2270.87 m.