Mixed Sedimentary Characteristics and Pattern of the Fan Delta in the Middle Permian Taerlanggou Profile,Xinjiang Province
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摘要: 在精细测量和详细观察新疆塔尔朗沟剖面二叠系露头的基础上，系统研究了中二叠统大河沿组与塔尔朗组扇三角洲相内陆源碎屑与碳酸盐组分的混合沉积特征。结果表明：大河沿组以扇三角洲平原分流河道沉积为主，其下部主要发育棕红色含粗砾中砾岩，碳酸盐组分不发育；上部主要发育棕红色含中砾细砾岩，夹若干层条带状分布的砾质泥晶灰岩。塔尔朗组底部自下而上发育扇三角洲前缘水下分流河道与水下分流间湾。水下分流河道为底凸顶平的砂砾岩体，下部发育灰绿色含中砾细砾岩夹含砾泥晶灰岩，灰岩呈断续条带状分布，横向延伸距离较小；上部发育灰绿色细砾岩夹含砾泥晶灰岩，灰岩在横向上的延伸距离较大。水下分流间湾以灰绿色泥岩和层状含砂泥晶灰岩为主，灰岩在横向上分布较稳定。结合前人在研究区中二叠世古气候、沉积环境等方面的认识，进一步建立了扇三角洲混合沉积模式。Abstract: Based on careful measurement and detailed observation of the Permian outcrop of the Taerlanggou profile in Xinjiang province,the mixed sedimentary characteristics of the land debris and carbonate components in the delta facies of Permian Daheyan Formation and Taerlang Formation were systematically studied. Daheyan Formation consists mainly of fan delta plain distributary channel sediments. At its base it is mainly brownish-red medium conglomerate with coarse gravel,and carbonate components are rarely found. At the top it is mainly brownish-red fine conglomerate and medium gravel,mixed with many gravelly micrite bands. The Taerlang Formation was a fan delta front underwater distributary channel and underwater bay between the channels from the base bottom upwards. The underwater distributary channel,a glutenite convex at the bottom and flat-topped,developed a grayish-green fine conglomerate with medium gravel and gravelly micrite in discontinuous bands of short extent at the bottom,but extending a long distance horizontally at the top. The underwater bay between the distributary channels mainly developed a grayishgreen mudstone and layered sandy micrite distributed evenly in all horizontal directions. In combination with previous studies of the Middle Permian paleoclimate,sedimentary environment and other aspects of the study area,the mixed sedimentary model of the fan delta was established.
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