河北涞源祁家峪剖面寒武系层序地层划分

摘要

河北涞源祁家峪剖面寒武系出露连续,层序界面清楚且沉积现象丰富,是进行华北地台寒武系层序划分的较为典型的剖面之一.在新的寒武系年代地层框架下,依据地层的叠置形式、纵向上的沉积相变化及其内部的旋回特征,将该剖面寒武系划分为8个三级层序.结果表明:研究区域从馒头组、毛庄组的“TST +HST”沉积序列转变为“CS+HST”的淹没不整合型层序序列,反映出从混积潮坪沉积序列向缓坡型碳酸盐台地的演化过程,也意味着华北地台寒武系碳酸盐台地从发展阶段向成熟阶段的重大转变;该剖面芙蓉统内部的竹叶状灰岩与长山组顶部、凤山组第1个三级层序顶部发育的均一石生物丘代表了华北地台寒武系末期“贫乏骨骼的风暴海”以及“随着后生动物辐射,微生物碳酸盐岩也在增加”两大特殊沉积现象较为典型的沉积样式.基于层序地层框架内的沉积相叠加方式和地层记录中旋回特征的描述,对河北涞源祁家峪剖面进行层序地层划分,将为探索华北地台在太行山北缘广泛分布的寒武系提供参考实例,也为今后更大区域范围的对比研究提供线索.%Qijiayu section in Hebei Laiyuan,characterized by continuous Cambrian stratigraphic succession,distinct sequence interfaces and rich depositional occurrences,is one of the typical profiles for Cambrian sequence stratigraphic division in North China Platform.Within the framework of new Cambrian strata,according to the stacked patterns of the formation,the changes of the sedimentary facies and characteristics of the inner cycle,8 third-order sequences were subdivided for the Cambrian section.The achievements show that "TST+ HST" sedimentary sequences in Mantou and Maozhuang Formations in the study area change into "CS + HST" drowned unconformity ones,this phenomena indicate that the evolutionary process from the mixed tidal flat sedimentary sequence to the ramp carbonate platform i.e.the pretty big transformation from the developing stage to the mature one for Cambrian carbonate system of North China Platform;the well-developed uniform stony bioherms on the tops of the edgewise conglomerate in Furong series,Changshan Formation and the first third-order sequence of Fengshan Formation represent the more typical depositional patterns of the two special sedimentary phenomena during Late Cambrian in North China Platform i.e."the deposition inside the skeletal-deficient stormy sea" and "the increase in the microbial carbonate abundance with the radiation of the metazoan".Based on the facies superposed models and described cycle characteristics of the stratigraphic record,the sequence stratigraphic division was conducted for Qijiayu section in Hebei Laiyuan,that's to say to provide a reference example for the exploration of Cambrian strata widely distributed at the northern margin of Taihang Mountains in North China Platform,and furthermore also present the clues for the comparative studies and correlation on the larger regional scale.