摘要
本文首次报道了峡东地区埃迪卡拉系灯影组石板滩段地层中的风暴岩。通过详细的剖面观察、测制和室内研究,识别出石板滩段典型的风暴沉积标志,包括各种丘状交错层理、粒序层理、冲刷-充填构造、平行层理及变形层理等。结合各类风暴沉积标志在剖面上的组合关系将研究区风暴岩划分出4个风暴沉积序列类型:其中类型Ⅰ为风暴流成因的滞留沉积与底面的冲刷面、丘状层理、波状层理、水平层理的组合,属形成于正常浪基面附近的近原地风暴岩;类型Ⅱ为具颗粒流性质的块状内碎屑灰岩与丘状交错层理的组合,常见变形层理,形成于斜坡上部;类型Ⅲ为以渠模、丘状交错层理与水平层理的频繁叠加为特征,出现在风暴浪基面与正常浪基面之间;类型Ⅳ为具粒序层理的砂-砾屑浊积灰岩,形成于风暴浪基面以下,划归为风暴成因的远源浊流沉积。研究区风暴岩的特征表明:风暴层蕴含了强烈的气候信息,风暴频发是灯影期气候转型的重要响应;该时期构造相对活跃、海底地形复杂化是风暴沉积形成的原因之一;研究风暴岩的特征对等时地层对比研究也具有重要意义。
Tempestite of the Ediacaran Dengying Formation has been discovered for the first time in the Eastern Yangtze Gorges area. The outcrop sections and our observation helped recognize many depositional characteristics of storm deposits, such as hummocky cross stratifications, scouring-filling structures, graded bedding and convolute bedding. Four types of storm deposits have been recognized. Type I is characterized by stranded gravel deposition, hummocky cross stratifications, and scouring base, which was formed in the vicinity of the fair weather wave base. Type ]~ is characterized by the intraclastic limestones, hummocky cross stratifications and convolute bedding, which was formed in the upper ramp environment. Type HI is characterized by the limestones with gutter cast and hummocky cross stratifications, which were deposited at the places between storm and fine weather wave base. Type IV is represented by the thin bedded silty micrites formed by distal storm turbidity currents below storm wave base. Study of the storm deposits indicates that the tempestites carry important paleoclimate information and frequent occurrences of storms responded to climate changes during the Dengying Period, in which relatively strong tectonic activity and complicated submarine topography was responsible for the formation of tempestites. Therefore, the characteristics of tempestites are of great significance in understanding of stratigraphic comparison study.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2013年第12期1901-1912,共12页
Acta Geologica Sinica
基金
中国地调局华南中都震旦纪-志留纪地层格架
岩相古地理与成矿关系(编号1212011121103)
中上扬子海相含油气盆地油气地质综合调查-桑植-石门及邻区油气地质综合调查评价及地层对比研究(编号121201120968)资助的成果
