南秦岭镇安盆地泥盆纪沉积体系与古地理演化

通过对南秦岭镇安盆地泥盆系露头剖面的详细研究，将该区泥盆系划分为海岸、陆棚、斜坡-盆地及碳酸盐岩四种沉积体系，沉积体系及岩相组合具有南北向分异、东西向展布的特点。从地层由南向北超覆，相类型由北部的近源相至南部的远源相，以及碎屑搬运方向总体从北向南的变化趋势，更加确定了以前认为北部存在一个消失的古陆的认识。根据沉积体系及岩相组合的演化，把研究区的沉积盆地演化归纳为初始坳陷、拗陷和强裂断陷三个发展阶段，在不同的发展阶段具不同的环境格局，由北向南表现为：D2吉微特期古陆-海岸-陆棚；D2弗拉斯期古陆-碳酸盐台地-陆棚；D3法门期块断隆起-海岸-陆棚-斜坡-盆地-台地。

DEPOSITIONAL SYSTEMS AND PALAEOGEOGRAPHIC EVOLUTION OF THE DEVONIAN IN ZHEN''''AN BASIN OF SOUTH QINLING

Based on the detailed research on outcrop sections of the Devonian in the Zhen'an Basin, South Qinling, the Devonian can be divided into four depositional systems, i.e. coast system,shelf system, carbanate platform system and slope-basin system, with the depositional systems and lithofacies assemblages being different from north to south, and extending west to east in spatial. In terms of the strata overlaping from south to north, the trend of facies types from distal facies in the south to proximal facies in the north, and terrigenous sediments transported from north to south, there disappeared old land in the north. According to the evolution of the depositional systems and lithofacies assemblages, the history of the Devonian depositional basin can be divided into three main evolutionary stages: initial depretion period, depressional period and strong rift faulting period. their palaeogeographic patterns were varying with the different stages. From north to south displayed the patterns: oldland -coast-shelf in Givetian in Middle Devonian, oldland-carbonate platform shelf in Frasnian, and uplift-coast-shelf-slope-basin-platform in Famennian in Late Devonian.