BASAL BEDS OF THE NEOGENE GUANTAO FORMATION IN YUEDONG OILFIELD,BEACH AREA OF THE LIAOHE DEPRESSION
Cui Xiangdong1, Wang Renhou2, Shi Dunjiu2, Yuan Qingqiu2, Ma Hongbin2
1. Department of Earth Sciences, Nanjing University, Nanjing 210093; 2. Exploration & Development Research Institute of Liaohe Oilfield Branch Company, China National Petroleum Corp., Panjin, Liaoning 124010
Three kinds of contact between the Neogene Guantao Formation and the Paleogene Dong-ying Formation could be recognized in the Liaohe Depression:the eruptive,gradual and “sandwiched” types.The latter was discovered in southern part of the Central Rise and its both sides,where the lower sandstone-conglomerate and upper siltstone-mudstone,with thickness being about 50～100 m,sandwiched in between the typical Guantao Formation and the Dongying Formation.Since lack of evidence,there was different opinions on age of the strata for a long time.The authors found in the argumentative strata from the Well Yuedong 603,for the first time,the sporopollen fossil assemblage in age of Neogene as well as redeposited alga fossils from the Paleogene Shahejie Formation and middle-lower Dongying Formation,which was obviously different from that in the underlying Donying Formation.The discovery confirmed that the argumentative strata should be basal beds of the Neogene Guantao Formation.Furthermore,the features of the unconformity between the Paleogene and the Neogene and the exploration implications of the strata were discussed.