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The Jiyang Sag was a near-sea basin in Oligocene time of mild and wet climate, The flou-rishing living things in this basin and the continuous depressions created a favorable environ-ment for oil generation. Occasional transgressions resulted in special water-medium conditions,giving rise to a unique biological group of abundan terrestrial and fresh-water biota and orga-nisms characteristic of semi-saline environments as well as small amounts of marine biota. Discussions are also made of the evolution of organic matter on the basis of changes ofgeochemical indexes for oil-generating locks at different depths in the Dongying Depression.
The Jiyang Sag was a near-sea basin in Oligocene time of mild and wet climate, The flou-rishing living things in this basin and the continuous depressions created a favorable environ-ment for oil generation. Occasional transgressions resulted in special water-medium conditions , giving rise to a unique biological group of abundan terrestrial and fresh-water biota and orga-nisms characteristic of semi-saline environments as well as small as of marine biota. Discussions are also made of the evolution of organic matter on the basis of changes ofgeochemical indexes for oil-generating locks at different depths in the Dongying Depression.