坳陷湖盆三角洲前缘沉积微相构成及其分带性——以鄂尔多斯盆地上三叠统延长组为例

THE MICROFACIES ARCHITECTURE AND ZONING OF DELTA FRONT IN DEPRESSED-TYPE LACUSTRINE BASIN——TAKING THE YANCHANG FORMATION OF TRIASSIC IN ORDOS BASIN AS AN EXAMPLE

以鄂尔多斯盆地上三叠统延长组为例,研究了坳陷湖盆三角洲前缘沉积微相构成和微相组合,共识别出截削式和完整式水下分流河道、河口坝、远砂坝、席状砂、分流间湾等5种沉积微相和水下分流河道叠加组合、河口坝叠加组合、水下分流河道与河口坝叠加组合、河口坝与远砂坝、席状砂的叠加组合等4类微相组合,在此基础上,重点论述了三角洲前缘沉积微相组合的时空分布规律,并以三角洲前缘坡折带为界,将三角洲前缘分为“台型前缘”、“坡型前缘”和“盆型前缘”3部分,各部分有独特的沉积微相组合形式。

Taking the Yanchang formation of Triassic in Ordos basin as an example, this paper research in detail the microfacies architecture and association types of depressed type lacustrine deha fronts. The microfacies of delta fronts include truncated distributary channels and integrated distributary channels, river mouth bars. distal bars, front sheet sandstones and interdistributary bay. According to association type the microfacies may be divided four types of sandstones that consist of nine subtypes including superimposed distributary channel, superimposed channel mouth bars, subaqueous distributary channels anti channel mouth bar associations and channel mouth bar, distal bar and front sheet association. The authors discusses in detail distribution microfacies association of delta fronts. The depressed-type lacustrine deha fronts can be divided into three parts： platform delia front, sloping delta front anti basin delta front by the bounds of slope break. Every part has unique microfacies association type.