Geochemical characteristics of the Triassic Chang 7 lacustrine source rocks, Ordos Basin, China: Implications for paleoenvironment, petroleum potential and tight oil occurrence

•Paleoenvironments were sub-reducing to sub-oxidizing with a water depth of 150 m.•Organic matter origins are mainly plankton, algae and bacteria.•Peak oil generation of source rocks occurred during 115–95 Ma.•Hydrocarbon expulsion thresholds are 2560 m for shale and 2080 m for mudstone.•Transition areas between high value centers of source rocks are enrichment zones.