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位于扬子地块西缘的龙门山区,是著名的中生代冲断带,其中泥盆系发育,沉积类型多样,厚度巨大,既包括未经变质的稳定型,也包括浅变质的过渡型和活动型地层。根据推覆构造特点和不同类型泥盆系之间的关系,确认前山带、中山带和后山带,分别包含了泥盆纪沉积的边缘带、过渡带和活动带的地层纪录。泥盆纪的沉积盆地则是一个NE向不对称的裂谷盆地,它的东南边缘,早期由于同生断裂的影响造成宽阔而复杂的古地理面貌和岩相、厚度变化。晚期由于海平面上升,沉积区扩大,边缘带成为宽阔平坦的碳酸盐台地,北段仍保留平行岸线的深水槽地,盆地西侧为较深水的浊积岩分布区,而后过渡为边缘浅水区。本区泥盆系的层序地层结构特点,是由多级不对称层序组成,沉降曲线则由两个下凹的曲线组成阶梯状。这些特点说明,该盆地具有伸展成因的裂谷性质,盆地的形成可能与沿着有根的叠瓦式低角度剪切断裂系发育的地壳伸展作用有关。
The Longmenshan area, located in the western margin of the Yangtze block, is a well-known Mesozoic thrust belt in which the Devonian developed with various sedimentary types and thicknesses, including both the unaltered and stable metamorphic transitional and active types Strata. According to the characteristics of nappe structure and the relationship between different types of Devonian, the anterior, middle and rear mountain belts are confirmed, which contain the stratigraphic records of Devonian sedimentary marginal zone, transition zone and active zone respectively. The Devonian sedimentary basin is an NE-asymmetric rift basin. Its southeastern margin caused a wide and complex palaeogeomorphology and lithofacies and thickness changes due to syngenetic fractures in the early stage. Late stage of the sea level rise, the deposition area expanded, the edge zone to become a wide and flat carbonate platform, the northern section of the deep parallel to retain the shoreline deep basin on the west side of the deep water turbidite distribution, and then transition to the edge Shallow water. The sequence stratigraphic features of the Devonian in this area are composed of multi-level asymmetric sequences, while the subsidence curves consist of two concave curves that form a staircase. These characteristics indicate that the basin has extensional causative rifting, and the formation of the basin may be related to the crustal extension developed along the rooted sub-wedge low-angle shear faulting.