Early Paleozoic Extension-Compression Transition and Formation of a Paleo-Oil Reservoir System in the NW Sichuan Basin: Implications for Deeply Buried Hydrocarbon Accumulation

Figure 3

Lithofacies photos of source rocks in the Longmenshan-Michangshan area. (a) Paraconformity of the Doushantuo Fm and Dengying Fm, Qingping, Hanwang. The top of the Doushantuo Fm has interbedded black mudstones and phosphorite. (b) QP–6 is the Lower Cambrian Maidiping Fm with diabase dyke intrusion, at Qingping, Hanwang. (c) GY–7 is the nodular limestone interbedded with thin black shale, which has oil intrusion, at Changjianggou, Shangsi. (d) Paraconformity between the Lower-Middle Silurian gray shale and the Lower Devonian Pingyipu Fm, at Yanmenba, Jiangyou. (e) HY–GYCJG/CJG–11, P/T Boundary, and paraconformity between the Upper Permian Dalong Fm and the Lower Triassic Feixianguan Fm, at Changjianggou, Shangsi. (f) Suspected paraconformity between the Doushantuo and Dengying formations, which has bitumen infill at the boundary, at Guanzhuan, Qingchuan. (g) E/C Boundary and paraconformity between the Dengying and Qingzhusi formations, at Daba, Guangwushan. (h) Conformable contact of the third (clasolite) and second (dolomite) members of the Dengying Fm, at Hujiaba, Ningqiang. (i) Black shale of the Doushantuo Fm, at Nanping and Da’an, Ningqiang.

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