塔中地区上奥陶统层序格架内礁滩体展布及沉积相

为了明确塔中地区上奥陶统层序地层格架下礁滩体的沉积发育规律,通过岩心及铸体薄片观察、钻测井资料解析、单连井剖面解剖等技术方法,对良里塔格组的礁滩体进行了研究。结果表明:控制礁滩体发育的沉积亚相主要为生物骨架礁、灰泥丘、粒屑滩和滩间海;层序地层格架可划分为3个三级层序和8个四级层序,sq1、sq2、sq3层序主要发育灰泥丘和粒屑滩及其复合体,sq4、sq5、sq6层序普遍发育以礁核为主的高能环境礁滩相沉积,sq7、sq8层序主要发育滩间海;在高频层序格架中,微地貌和高频海平面变化旋回控制了可容纳空间的变化;短暂的构造稳定期和适度的海平面上升期是礁的主要生长期,礁滩主要发育在高位体系域中,在纵向演化上由内带向外带迁移;晚期发育的礁滩体具有较明显的前积作用,在四级层序格架控制下由台内缓坡向台缘高处迁移。

DISTRIBUTION AND SEDIMENTARY FACIES OF THE REEF FLATS IN UPPER ORDOVICIAN SEQUENCE FRAMEWORK OF TAZHONG AREA

In order to make clear of the sedimentary development laws of the reef flat complex in Upper-Ordovician sequence stratigraphic framework in Tazhong area,with the help of the core and slice observations,drilling and logging data analyses,single and commingled well profile anatomy and other technical means,the complex in Lianglitage Formation was figured out.The achievements show that the sedimentary subfacieses controlling the complex development are mainly composed of the biological skeleton reef,plaster （ chalky clay) mound,granular beach and inter-beach sea;the sequence stratigraphic framework can be divided into 3 three-order sequences and 8 four-order sequences,Sequence sq1,sq2 and sq3 mainly consist of the chalky clay mounds,granular beaches and their complexes;the high-energy environment reef flat facies sedimentation is developed generally in Sequence sq4,sq5 and sq6 and moreover takes the reef core as the key form;the inter-beach sea is principally developed in Sequence sq7 and sq8.In the high-frequency sequence framework,the micro geomorphology and high-frequency sea level change cycles control the changes of the accommodation space.The development and migration laws of the reef flat complex are:the short period of the structural stabilization and moderate sea-level rise time are the main growth periods of the reefs,the reef flat mainly developed in the high-order system tract migrate from inner zone to outer zone in its vertical evolution.The progradation of the lately developed reef flat complex is pretty more obvious,and furthermore under the control of the four-order sequence framework the complex migrates from the gentle slope within the platform to the high parts of the platform edges.