Stratigraphic sequence features in lower part of the third member of Shahejie formation in the middle part of Shulu sag

Based on stratigraphic correlation, core observation, thin section identifying, geochemistry analyzing and seismic horizon calibrating and tracing, and in combination with the analysis of regional tectonic and sedimentary evo- lution characteristics, an entire third- sequence is considered to be existed in lower part of the third member of Shahejie Formation in the Middle part of Shulu Sag of the middle Depression of Hebei Province. Indicators of sequence boundary, especially the top boundary were identified by using the data of lithologic character, well logging, seism, geochemistry analyzing and so on. These indicators are: the content of carbonate rock is high and steady: the exhibition of the resistivity curves is massive and high value, the natural gamma value is very low; the seismic reflection is very good and the top surface is a good toplap surface and the abundance of organic material is very different.