黄骅坳陷中北区沙河街组四段上亚段地层的确认

以往黄骅坳陷仅在南区的王官屯地区发现过确切的古近系沙河街组四段地层。上世纪 90年代初 ,地层古生物工作者曾根据个别单井孢粉化石资料 ,怀疑黄骅坳陷北区的北塘凹陷局部分布有沙四段。但由于当时的勘探程度较低 ,化石证据不足 ,因而没有得到广泛认可。中区板桥和歧口凹陷过去从未发现沙四段。通过对板桥凹陷地层的系统古生物分析 ,发现中北区沙三段下伏原来部分归属中生界的地层中含大量的藻类、介形虫、腹足类及轮藻化石 ,依据它们的生物群特征 ,这套地层应属于沙河街组四段 ,且为沙四段上亚段。

DISCOVERY OF THE FOURTH MEMBER OF SHAHEJIE FORMATION IN HUANGHUA DEPRESSION

The Member 4 of the Eocene Shahejie Formation was only discovered in the areas around Wangguantun in the southern Huanghua Depression in the past. In the early 1990s some paleontologists considered that there was a Member 4 of the Shahejie Formation in the Beitang Sag in the northern Huanghua Depression according to some fossil spore-pollen data from several wells, but owing to insufficient fossil evidence and poor skill in exploration it was not widely accepted. Based on the systematic analysis of the fossils from the Banqiao Depression, a large number of algae, ostracodes, gastropods, and charophytes were found in the strata underlying the Member 3 of the Shahejie Formation and previously with a part attrubited to the Mesozoic. Thus, on the basic of the biotaic features, these strata should belong to the Member 4 of the Shahejie Formation, being the Upper Submember of Member 4.