塔中及相邻地区早奥陶世沉积格局新论

New Evidence on the Sedimentary Framework of the Early Ordovician in Central Tarim and Adjacent Area

前人的观点认为,早奥陶世的塔里木盆地是一个统一的"大碳酸盐岩台地",斜坡相呈马蹄形发育在古城—轮南一线。通过对塔中地区满加1井—塔中29井一线及相邻地区下—中奥陶统的岩石学、沉积学和地震地层学等方面的研究,发现这一线的下奥陶统主要由一套较深水的斜坡及海槽沉积构成,其地层厚度和地震反射特征也明显与周边地区不同,认为塔中及相邻地区在早奥陶世期间已经从早期的塔里木"大碳酸盐台地"中分化独立出来,分裂成塔中—巴楚台地、古城台地、塘南台地三块孤立台地,以塔北隔海相望。各孤立台地周缘发育台地边缘高能礁滩沉积体,呈条带状展布,主要由中高能粒屑滩组成;向内相变为台地相,发育台内滩、台内洼地、滩间海等亚相;向外进入较深水的斜坡—海槽沉积区,从而确立了塔中及相邻地区早奥陶世新的区域沉积格局。新沉积格局的确立,对于确立下奥陶统新的有利勘探区带具有重要的理论和现实意义,大大提升了研究区下奥陶统的油气勘探战略地位。

The previous viewpoint considered that,the early Tarim basin was an ＂unified carbonate platform＂,its slope was developed along the Gucheng-Lunnan area.Based on sedimentologic and seismic stratigraphic data from the lower-middle Ordovician,deep-water slope and basinal facies were recognized along the MJ1-TZ29 section,so that the Tazhong and its adjacent areas could have already been isolated from the ＂unified carbonate platform＂and seprated into three platforms of Tazhong-Bachu,Gucheng and Tangnan,which was also faced with TaBei area across a trough.The high-energy reef-shore bodies bandingly developed among the edge of each isolated platform as a band,which were mainly composed of mid-high energy grain banks.Inwards,it becomes the deposition of platform,developing the subphases of intraplatform banks,intraplatform depression and interabeach seas and soon.Outwards it becomes deeper-water deposition area of slope-trough.Under this circumstance,the new regional depositional pattern of the Tazhong and adjacent areas has been established.This new pattern has great theoretical and realistic significance for the establishment of new favourable exploration zones.It also greatly increases the strategic position for the petroleum exploration in lower Ordovician of research area.