The source rocks and crude oil of the Hongze sag, North Jiangsu basin, and the Dezhou depression, Bohai Gulf basin, have been systematically studied. The relatively high abundance of dinostrance isomers and 24-n-propylcholestane have been identified in the Tertiary deposits of these regions. Based on their geological-geochemical significance, distribution and micro-fossil data, the authors tentatively postulate that the dinosteranes and 24-n-propylcholestane may be the product of transgression. They were derived from marine algae and can be regarded as the marker of transgression.