川东南庙高寺—二里场地区嘉陵江组层序地层与沉积相

下三叠统嘉陵江组可划分为2个三级层序,对应嘉一—嘉二、嘉三—嘉五两大地质时期。根据岩心和测井解释进一步识别出了6个四级层序和15个五级层序。这两个三级层序都由海侵体系域和高位体系域构成,沉积相都经历了由开阔环境向局限环境的转变。因此嘉陵江组含开阔台地和半局限—局限台地两大沉积相,同时可识别出6种亚相及20种微相。四级、五级层序在广大的台地区具有可比性,纵向上滩体位置变化不明显。嘉二1和嘉四1这两个时期处于特殊的海平面升降旋回阶段,台内滩相较发育;嘉一到嘉二期和嘉三、嘉四到嘉五期,经历了由开阔台地相的石灰岩沉积到局限台地相的膏岩、白云岩沉积两次大的相变,构成两轮沉积旋回。

Sequence Stratigraphy and Sedimentary Facies of Lower Triassic Jialingjiang Formation in Miaogaosi-Erlichang Area,Sichuan Basin

Two 3rd-order sequences can be divided in the Lower Triassic Jialingjiang Formation(T1j) in the eastern part of Sichuan Basin,which correspond to two geologic chrons,Jialingjiang 1 to 2 Members(T1j 1-2) and 3 to 5 Members(T1j3-5).Based on the comprehensive study of rock cores and loggings,six 4th-order and forteen 5th-order sequences are further recognized and both of 3rd-order sequences are attributed to TST and HST.The sedimentary facies went through a transition from open platform to restricted platform so that Jiangling Formation includes the two sedimentary facies,the open platform facies and the half-restricted to restricted platform facies,from which six subfacies and twenty microfacies can be recognized.The 4th-order and 5th-order sequences are comparative in wide region of platform but the bank has not significant migration in vertical.Bank facies developed in the platform during T121 and T141 chrons which were just in a special stage of eustracy cycles.Limestone of the open platform facies is transformed into gyprock and dolostone of the restricted platform facies during T1j 1-2 and T1j 3-5,which constitute two sedimentary cycles.