Coal and hydrocarbon source rocks in the Triassic Yanchang Formation in the Ordos Basin were stu-died to identify their sedimentary organic facies by combining the basic organic rock compositions of sedimentary organic facies with the sedimentary faices and the organic geochemical characteristics of enriched or dispersed organic matters in the Yanchang Formation.The result indicates that there are six types of organic facies:the terrestrial forest(bog) organic facies(A)

the swamp forest(bog) organic facies(B)

the swamp-marsh forest(bog) organic facies(C)

the marsh(bog) organic facies(D)

the allochthonous residual(float bog) organic facies(E)

and the open lake algae organic faces(F).Among them

A and B generate coal

F generates hydrocarbons

while C

D and E generate both hydrocarbon and coal.The hydrocarbon generating potential of each organic facies was analyzed through Rock-Eval experiments.It is suggested that the study on sedimentary organic facies is a useful method in evaluating the paragenesis of various types of combustible organic minerals

including coal

oil

gas

and oil shale.A comprehensive evaluation of the hydrocarbon-generation trends and convertion ability of the coal and hydrocarbon source rocks in the Yanchang Formation was also carried out by adopting knowledge concerning the organic sedimentary facies