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Spores and pollen in oils as indicators of lacustrine source rocks

Summary More than 200 species of fossil spores and pollen extracted from 68 crude oil samples collected from the lacustrine sedimentary basins of China, including the Talimu Basin, the Zhungeer Basin, the Jiuquan Basin, the Chaidamu Basin, the Eerduosi Basin, the Xialiaohe Depression, etc., have been investigated. The spores and pollen found in the crude oil are interpreted as a kind of ‘trace element’ indicating the pathway of the petroleum migration from the source rock to the reservoir. The principle of why some of the spores and pollen found in the crude oil can act as a kind of indicator of source rock, and the methods used to find and recognize this kind of indicator, are explained in this paper. Based on the investigations of the spores and pollen from the crude oils, the spore and pollen indicators of lacustrine petroleum source rocks of the continental sedimentary basins are proposed. The spores and pollen acting as the indicators of the lacustrine petroleum source rocks usually indicate a tropical or subtropical wet depositional climate. It is therefore, concluded that a wet and hot climate is favourable for the deposition of lacustrine petroleum source rocks.