四川广元地区上三叠统小塘子组、须家河组层序地层研究

根据层序地层理论和研究方法，对四川北部广元地区上三叠统小塘子组和须家河组沉积地层露头剖面的详细研究，划分出2个二级层序和6个三级层序。平均每个三级层序的时限为2．9Ma。研究区上三叠统沉积地层从下到上由滨海相、三角洲相、辫状河相、冲积扇相组成，为印支期扬子地台西缘前陆盆地形成演化及其北西侧龙门山推覆造山作用的沉积响应。根据区域不整合面和其它层序界面特征，结合沉积盆地充填序列、沉积相和沉积体系域的时空配置，建立了该区晚三叠世地层格架和4个等时界面。

Sequence stratigraphy of the Late Triassic strata in the Guangyuan region, Sichuan

The exposure sections of the Upper Triassic Xiaotangzi and Xujiahe Formations sedimentary strata in the Guangyuan region, Sichuan are examined in detail with the aid of theory and method of sequence stratigraphy. Two second-order and six third-order sequences have been distinguished. Each of the third-order sequences is age-dated with an average time duration of about 2.9 Ma. The sedimentary facies of the Upper Triassic sedimentary strata in the study area consist of littoral facies, delta facies, facies, braided stream facies, alluvial fan facies. The Triassic strata are considered to be the responses to the formation and evolution of the foreland basins on the Indosinian western Yangtze platform and thrusting of the Longmen mountain area. The Late Triassic sequence stratigraphic framework and four isochronous boundaries are constructed on the basis of the unconformity and other sequence boundaries in combination with the spatio-temporal arrangement of the filling sequences, sedimentary facies and sedimentary systems tracts.