陆相沟鞭藻的起源和演化及其生油意义

ORIGIN AND EVOLUTION OF TERRESTRIAL DINOFLAGELLATES AND THEIR SIGNIFICANCE IN SOURCE POTENTIAL FOR PETROLEUM

The origin and evolution of terrestrial fresh water dinoflagellates have been discussed in this paper, based on the new discoveries of the authors in the latest ten years integrated with new information from home and abroad. The new world-wide discoveries indicate that dinoflagellates invading freshwaters can be traced as early as the Late Jurassic rather than the early Tertiary stated by previous studies. Probably both marine and non-marine dinoflagellates evolved contemporaneously since the marine and inland waters existed on the earth surface. In freshwaters the Ceratioid cysts flourished in the Early Cretaceous while the Peridinioid cysts did from the Late Cretaceous to the Early Tertiary. It seems that the evolutionary tendency of dinoflagellates in both marine and freshwaters is similar to following the plate reduction model, but freshwater dinoflagellates never flourished as well as their marine counterparts. The freshwater dinocyst assemblages are characterised by the features as follows: low diversity, cysts smaller in size with thin wall, mostly autophragm; rare skolochorate commonly proximate cysts ;cysts lack of distinct indications of tabulation and archeopyle.but with archeopyle type of sutural openings, which differ them from marine dinocyst assemblages obviously. In other words, dinoflagellates are still microfossils of facies-indicators. Freshwater dinoflagellates are as important as the marine ones in source potential for petroleum.