塔里木盆地古隆1井中上奥陶统牙形石生物地层界线研究

Research of the biostratigraphy boundary on the Middle and Upper Ordovocoan in well GLl of Tarim Basin

塔中地区古隆1井中晚奥陶世处于台缘斜坡带,地层发育齐全,奥陶系划分为3统5组,自上而下为却尔却克组、恰尔巴克组、一间房组、鹰山组与蓬莱坝组。在恰尔巴克组及一间房组分别获得了Pygouds anserinus与P.serra牙形石带,依此将中上奥陶统界线划在5875 m,两统之间不存在任何地层缺失或不整合面。认为碳酸盐岩台地上的良里塔格组在古隆1井相变为191 m厚的泥岩夹灰质泥岩,在地震剖面显示为一套空白反射,横向较好追踪与对比;指出了恰尔巴克组与一间房组在平面展布上具有同步性,卡塔克隆起主体上缺失,仅分布在台地边缘低洼处或在斜坡带。

The Gulong-1 well lies in the platform margin slope in Middle and Late Ordovician, the sequence of strata of the Ordovician growth completely. They are divided into three series and six formations. The Upper Ordovician includes Queerqueke Formation and Qaerbake Formation, from top to bottom, the middle is consist of Yijianfang Formation and the upper of Yinshan Formation,the lower comprise the lower of Yinshan Formation and Penglaiba Formation. The sequence of strata is unique, the Middle and Lower Ordovician is identical with that of the Tazhang low uplift,the Upper Ordovician is similar to that of the Tadong region. There are a lot of conodont in the Qaerbake Formation and Yijianfang Formation, they belong to three fossil zone：Pygouds anserinus, P. serrus and Eoplacognathus suecicus. The boundary of Upper and Middle Ordocivian is place in 5 875 m. There is not any lacuna or unconformity. The Lianglitag Formation in the carbonate platform had a phase transformation to the mudstone and calcareous mudstone of 191 m in Gulong-1 well,It display a blank space reflection in the seismic section and is easily followed the trail in the landscape. There are synchronization on the distribution of Qaerbake Formation and Yijianfang Formation,they are hiatus in the main port of Tazheng low uplift and has a distribution in the low-lying of the platform margin or slope.