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首页> 外文期刊>Journal of Asian earth sciences >Linked sequence stratigraphy and tectonics in the Sichuan continental foreland basin, Upper Triassic Xujiahe Formation, southwest China
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Linked sequence stratigraphy and tectonics in the Sichuan continental foreland basin, Upper Triassic Xujiahe Formation, southwest China

机译：中国西南地区上三叠统须家河组四川陆前陆盆地连带层序地层与构造

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摘要

Intracontinental subduction of the South China Block below the North China Block in the Late Triassic resulted in formation of the transpressional Sichuan foreland basin on the South China Block. The Upper Triassic Xujiahe Formation was deposited in this basin and consists of an eastward-tapering wedge of predominantly continental siliciclastic sedimentary rocks that are up to 3.5 km thick in the western fore-deep depocenter and thin onto the forebulge and into backbulge depocenters. Five facies associations (A-E) make up the Xujiahe Formation and these are interpreted, respectively, as alluvial fan, transverse and longitudinal braided river, meandering river, overbank or shallow lacustrine, and deltaic deposits. This study establishes a sequence stratigraphic framework for the Xujiahe Formation which is subdivided into four sequences (SQ1, 2, 3 and 4). Sequence boundaries are recognized on the basis of facies-tract dislocations and associated fluvial rejuvenation and incision, and systems tracts are identified based on their constituent facies associations and changes in architectural style and sediment body geometries. Typical sequences consist of early to late transgressive systems tract deposits related to a progressive increase in accommodation and represented by Facies Associations A, B and C that grade upwards into Facies Association D. Regionally extensive and vertically stacked coal seams define maximum accommodation and are overlain by early highstand systems tract deposits represented by Facies Associations D, E and C. Late highstand systems tract deposits are rare because of erosion below sequence boundaries. Sequence development in the Xujiahe Formation is attributed to active and quiescent phases of thrust-loading events and is closely related to the tectonic evolution of the basin. The Sichuan Basin experienced three periods of thrust loading and lithospheric flexure (SQ1, lower SQ2 and SQ3), two periods of stress relaxation and basin widening (upper SQ 2 and SQ3) and one phase of isostatic rebound (SQ4). Paleogeographic reconstruction of the Sichuan Basin in the Late Triassic indicates that the Longmen Mountains to the west, consisting of metamorphic. sedimentary and pre-Neoproterozoic basement granitoid rocks, was the major source of sediment to the foredeep depocenter. Subordinate sediment sources were the Xuefeng Mountains to the east to backbulge depocenters, and the Micang Mountains to the northwest during the late history of the basin. This study has demonstrated the viability of sequence stratigraphic analysis in continental successions in a foreland basin, and the influence of thrust loading on sequence development.
机译：在三叠纪晚期，华南地块在华北地块以下的陆内俯冲作用导致在华南地块上形成了川前压变盆地。上三叠世须家河组沉积在该盆地中，由主要为大陆性硅质碎屑沉积岩的向东逐渐变细的楔形物组成，在西部的前深沉积中心厚达3.5 km，在前隆起和后隆起沉积中心上变薄。须家河组由五个相组成（A-E），分别解释为冲积扇，横向和纵向辫状河，曲折河，河床或浅湖相以及三角洲沉积。这项研究为徐家河组建立了一个层序地层学框架，该层分为四个层序（SQ1、2、3和4）。序列边界是根据相道错位以及相关的河流回春和切开来识别的，而系统道则根据它们的组成相联系以及建筑风格和沉积体几何形状的变化来确定。典型的序列包括与适应性的逐步增加有关的早期到晚期的海侵体系道沉积物，并由相协会A，B和C代表，并逐渐升级为相协会D。区域广泛且垂直堆叠的煤层定义了最大的适应性，并被上覆由相协会D，E和C代表的早期高位系统道沉积物。由于序列边界以下的侵蚀，晚期高位系统道沉积物很少见。徐家河组的层序发育归因于逆冲推力活动的活跃期和静止期，与盆地的构造演化密切相关。四川盆地经历了三个时期的推力载荷和岩石圈弯曲（SQ1，下部SQ2和SQ3），两个应力松弛和盆地扩张时期（上部SQ 2和SQ3）和一个等静回弹阶段（SQ4）。三叠纪晚期四川盆地的古地理重建表明，西部的龙门山由变质组成。沉积和新元古代前的基底花岗岩岩石是前深沉积中心的主要沉积物来源。从属沉积物来源为盆地晚期历史时期以东的雪峰山脉至隆起沉积中心，以西北的米仓山脉。这项研究证明了前陆盆地陆相演替中层序地层分析的可行性，以及推力载荷对层序发育的影响。

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