东海盆地西湖凹陷古近系包括花港组﹑平湖组和宝石组，是西湖凹陷比较重要的地层，也是烃源岩较发育的层位。因此，前人对西湖凹陷古近系的沉积环境作过大量的研究，但是对于平湖组不同的人持有不同的观点。文中通过对西湖凹陷BS-1，CHX-1，TWT-1，DQ-1，PH-1，NB2-1-1 等井的微体古生物化石资料（孢粉﹑钙质超微化石﹑介形虫﹑有孔虫﹑盘星藻﹑海相沟鞭藻等）进行研究认为：花港组为陆相沉积，有争议的平湖组上部为陆相沉积，中下部为海相沉积，宝石组为陆相沉积，并推断古近系为亚热带气候。

The group of Paleogene in Xihu Sag in Donghai Basin contains Huagang Formation，Pinghu Formation and Baoshi Formation，which not only are the important layers but also the layers where hydrocarbon source rocks developed well. Predecessors made a great deal of studies on sedimentary environment in Xihu Sag， but different people have different view-point to Pinghu Formation. Through the study on themicrofossil data （spore and pollen，calcareous nannofossils， ostracods，oraminifera， pediastrum，marine dinoflagellates etc.） in BS- 1，CHX- 1，TWT- 1， DQ- 1，PH- 1 and NB2- 1- 1 well in Xihu Sag, it is believed that Huagang Formation should be terrestrial deposit, with marine deposit in middle and lower part and terrestrial deposit in the upper part, and Baoshi Formation should be terrestrial deposit. It is deduced that Paleogene should be the subtropical climate.