Abstract: Forty-five species of fossil spores and pollen referred to 27 genera extracted from the crude oil samples collected from the Jurassic reservoirs of the Qaidam Basin in Qinghai Province of China were recorded. Based on the investigations of the palynomorphs in crude oil and the comparisons with those in potential source rocks, the petroleum source rocks of the petroliferous region were determined. On the basis of the palleoecological characteristics reflected by the original plants producing the spores and pollen, the sedimentary environment of the petroleum source rocks was discussed. The main species of spores and pollen found from crude oil of the Jurassic reservoirs of the Qaidam Basin are as follows: Cyathidites minor, Gleicheniidites confiexus, Dictyophyllidites harrisii, Osmundacidites wellmanii, 0. elegans, Apiculatisporis variabilis, Acanthotriletes midwayensis, Neoraistrickia truncatus, Lycopodiacidites rugulatus, Contignisporites cooksonii, Duplexisporites gyratus, D. amplectiformis, D. scanicus, Densoisporites perinatus, Protopinus scanicus, Protopicea exilioides, Protopodocarpus mollis, Piceites expositus, Piceaepollenites omoriciformis, Cedripites minor, Podocarpidites multesimus, P. paulus, Quadraeculina limbata, Q. enigmata, Q. minor, Chasmatosporites major, Cycadopites nitidus, C. typicus, C. subgranulosus, etc. The results indicated that the Lower Jurassic Xiaomeigou Formation and the Middle Jurassic Dameigou Formation should be the petroleum source rock series of the petroliferous region. The petroleum source rocks might have been evolved in the limnetic environment under wann and wet climatic conditions.

Key words: pore and pollen, Petroleum source, Environment, Jurassic