安徽巢北早石炭世和州组沉积特征及旋回地层

Early Carboniferous Hezhou Formation Sedimentary Characteristics and Cyclic Strata in North of Chaohu Lake Area,Anhui

巢湖北部地区位于下扬子板块北部边缘部分,下石炭统发育良好,分布广泛,其中和州组发育特征明显。在进行详细的野外测量和描述基础上,对和州组剖面进行岩石学沉积环境沉旋回性分析,确定了该组的沉积构造并探讨了旋回地层的成因。和州组剖面由5个水体向上变浅的旋回组成,Ⅰ、Ⅱ、Ⅲ旋回下部为灰岩,上部为泥岩,构成下厚上薄的的结构单元,反映水体周期性向上变浅,属于开阔台地沉积环境;旋回Ⅳ、旋回Ⅴ,达到最大海侵,为台地边缘浅滩相沉积环境。石炭纪扬子板块的海平面变化受冈瓦纳大陆冰川消长影响显著,沉积层序具有等时性,冈瓦纳大陆冰川型全球海平面变化是控制沉积旋回的主要因素。

The north of Chaohu Lake area is situated at the north margin of lower Yangtze plate,where Lower Carboniferous Series is well developed and vastly distributed,in which,the Hezhou Formation has distinct developing characteristics.Based on detailed field survey and description,analyzed petrology and sedimentary cyclicity of the formation section,determined sedimentary tectonics and discussed the genesis of cyclic strata.The section is composed of 5 cycles showing the water body shoaling upwards.The lower part of cycles I,II and III is limestone,upper part mudstone,constitutes thick lower part and thin upper part constitutional units reflecting periodically shoaling of water body upwards and belonged to open platform environment.Cycles IV and V have reflected maximum marine transgression and belonged to the marginal platform shoal facies sedimentary environment.Eustatic fluctuation of the Yangtze plate during Carboniferous Period was obviously impacted by ebb and flow of the Gondwanan glacial events;sedimentary sequences have isochroneity,thus the Gondwanan glacial type global eustasy is the primary controlling factor of sedimentary cycles.