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祁连山北缘旱峡地区发育完整的下白垩统下沟组—中沟组沉积序列;以陆源碎屑岩为主,发育砾岩、砂岩、钙质粉砂岩和页岩等;其中砾石分选差、磨圆一般、成分以灰白色砂岩为主,砂岩成分、结构成熟度中等—差。岩石组合、沉积序列和综合沉积特征研究表明,下沟组和中沟组主要由湖泊、扇三角洲、河流等3种类型沉积相、亚相与微相类型组成,发育了一系列重力流成因的沉积类型;湖泊沉积主要发育在下沟组底部和中沟组,扇三角洲沉积分布在下沟组中—上部,中沟组发育河流沉积。研究区早白垩世中期古流向以EN向为主,早白垩世晚期以W向为主,表明沉积沉降中心也由早期的旱峡西移至研究区西南侧。在综合分析的基础上,建立了研究区下白垩统下沟组—中沟组沉积相模式。
The Lower Cretaceous Xiagou-Zhonggou Formation sedimentary sequence is developed in the arid Gorge area in the northern margin of the Qilian Mountains. The main source rocks are conglomerate, sandstone, calcareous siltstone and shale. Among them, gravel separation , Rounding general composition of grayish white sandstone, sandstone composition, structural maturity medium - poor. The study on rock assemblage, sedimentary sequence and comprehensive sedimentary characteristics shows that the Xiagou Formation and Zhonggou Formation are mainly composed of three types of sedimentary facies, sub-facies and microfacies types, such as lakes, fan deltaic and rivers, and developed a series of gravity flow genesis Sedimentary types. Lake sediments are mainly developed at the bottom of Xiaoshogou Formation and Zhonggou Formation. Fan delta sediments are distributed in the middle-upper part of Xiagou Formation and in Zhonggou Formation. The paleocurrent in the mid-Early Cretaceous of the study area was dominated by EN, and was mainly dominated by W in the late Early Cretaceous, indicating that the sedimentation center moved westwards from the early drought gorge to the southwest of the study area. Based on the comprehensive analysis, the sedimentary facies model of Xiagou-Zhonggou Formation in Lower Cretaceous was established.