Organic geochemistry and elements distribution in Dahuangshan oil shale, southern Junggar Basin: Origin of organic matter and depositional environment

In addition, Dahuangshan oil shale samples are characterized by short- to middle-chain n-alkanes, low carbon preference index (CPI) values (0.93-1.24), single peak composed of nC20 or nC22, low Pr/Ph (0.41-0.91), relatively high Homohop index (0.061-0.99), and high concentrations of C27 sterane, indicating reducing, deep-water, and moderate saline environment with prevalent contribution of algae and microorganisms to organic matter accumulation.