冀东燕河营盆地南天门组的重新厘定

近30年来, 燕河营盆地中生代沉积地层一直以1∶20万区域地质调查报告或地质志所厘定的早白垩世九佛堂组为基准。经过1∶5万区域地质调查工作, 从层位、岩性组合、层序、年代及生物组合等方面对该套地层进行了系统研究, 认为该地层与区域上九佛堂组与义县组指状交互关系不符, 而岩石组合和沉积旋回也与区域上九佛堂组难以对比。采集的叶肢介化石属于Yanjiestheria-Orthestheria属组合, 其壳饰特征在叶肢介演化史上属进步类型, 被认为指示早白垩世的时代。本文将义县组之上的这套河湖相沉积地层时代划归早白垩世晚期, 并依据岩性组合和沉积层序等特征将其对比为南天门组。

Redefinition of Nantianmen Formation of Yanheying Basin in eastern Hebei Province

TheMesozoic sedimentary strata of Yanheying Basin have been regarded as the Early Cretaceous Jiufotang Formation by 1 /200 000 regional geological survey report and geological annals in recent thirty years. Through the research on1 /50 000 regional geological investigations of horizon, lithologic association, sequence, chronological ages and biologic assemblage, the authors consider that it is inconsistent with the finger-like interactive relationship between Jiufotang Formation and Yixian Formation regionally. Moreover, its rock association and sedimentary cycle are difficult to correlate the Jiufotang Formation in the studied area. The conchostracan fossils of this sedimentary strata consist of Yanjiestheria and Orthestheria which surface ornament features show a p rogressive types in conchostracan evolution, indicating generally the Earty Cretaceous in age. Consequently, the authors corsider the fluvial-lacustrine facies strata overlying the Yixian Formation are aged in the Early Cretaceous, correlated to the Nantianmen Formation according to its characteristics of lithologic association and sedimentary sequence.