松辽盆地海侵地层的分子地球化学特征

通过对松辽盆地源岩的地化特征研究，发现在青山口组一段和嫩江组一段及二段源岩中广泛分布的甲藻甾烷，指示了松辽盆地的两次海侵作用。青山口组一段源岩中甲藻甾烷的含量较嫩江组一段及二段相对较高，并且具有相对较高丰度的C₃₁甾烷。嫩江组一段及二段源岩的C₃₁甾烷的含量普遍较低，这不仅说明了青山口组一段源岩与嫩江组一段及二段源岩的藻类分布有一定的差别，而且指示了松辽盆地青山口组一段沉积时期水体的盐度更高，海侵的程度更大。根据松辽盆地甲藻甾烷的含量，确定的嫩江组一段源岩和青山口组一段沉积时期的海侵方向主要为岔6井和三1井方向。

THE CHARACTERISTICS OF MOLECULAR GEOCHEMISTRY OF MARINE TRANSGRESSION STRATA IN SONGLIAO BASIN

The relative high abundance of dinosterances has been found in the member No.l of Qingshankou Formation and the members No.1 and No.2 of Nenjiang Formation based on the geochemical studies of source rocks in Songliao Basin.The widely distributed dinosterance in source rocks indicates that there were two periods of marine transgression in geological history.The relative content of dinosterane in source rocks in the member No.1 of Qingshankou Formation is higher than that in the members No,l and No.2 of Nenjiang Formation.In addition,C 31 steranes have been identified only in the source rocks of member No.1 of Qingshankou Formation.This is not only attributed to differente algae in these formations,but also related to the differences between ancient sedimentary environment and the salinity in source rocks.The molecular fossil assemblage shows the relatively high salinity in source rocks of the member No.1 of Qingshankou Formation.It may indicate wide marine transgression in the period of the member No.1 of Qingshankou Formation sedimentation.The content of dinosterane has been tentatively used to determine the direction of marine transgression.