Characteristics and geological significance of oil shale biological marker compound in Dalianhe Formation of the Yilan coal basin in Heilongjiang Province

Organic matter is abundant in oil shale of coal seam in Dalianhe Formation. Low maturity form of aquatic organism contributes significantly to organic matter. Organic matter is mainly of type Ⅰand Ⅱ1, indicating pristine dominance and deposition in a fresh water, lake-swamp, lower oxygen and anoxic environment. The organic matters of oil shale member are mainly composed of type Ⅱ1 and Ⅱ2, reflecting pristine dominance and deposition in a fresh water and salty water environment.