天津蓟县中新元古代沉积层序的初步研究——前寒武纪(1800～600Ma)一级层序划分及其与显生宙的一致性

Meso-and Neoproterozoic sedimentary sequences in Jixian, Tianjin, northern China: division of the first-order sequences of the Cambrian strata (1800-600 Ma)and their correlation with the Phanerozoic strata

举世闻名的天津蓟县中新元古界剖面 ,地层厚度近万米 ,分布时限为 1 0 0Ma左右 (1 80 0～60 0Ma)。以岩相及相序为基础 ,不同级别沉积层序及其有序叠加形式为研究核心 ,在这套厚度巨大的前寒武纪地层中识别出 63个三级层序 ,可进一步划归为 2 2个二级大层序 ,4个一级超层序。4个一级超层序 ,不但代表了 1 80 0Ma到 60 0Ma的周期为 2 0 0Ma至 40 0Ma的沉积旋回 ,加上显生宙和两个一级旋回 ,表明了全球系统各圈层的一系列重大变异与银河年旋回存在明显的成因联系。尽管对地层记录中隶属不同级别沉积层序的间断面所代表的间断时限的绝对年限还难以精确估价 ,而建立在岩相及相序基础之上的旋回性地层记录的研究 ,是从复杂而不完整的地层记录中寻找出更多规律性的有效途径 ;特别是对生物地层分辨率不高的前寒武纪地层 ,尤其显得更加重要。

The strata in the famous Meso and Neoproterozoic Jixian section, Tianjin, northern China range in age between 1800-600 Ma, with the thickness less than ten thousand metres. These Cambrian strata have been grouped, on the basis of sedimentary facies sequences and stacking patterns of depositional sequences, into 63 third order sequences, or 22 second order megasequences and 4 first order supersequences, of which the latest ones represent the depositional cycles with the periods of 200-400 Ma during 1800-600 Ma. These cycles plus two first order cycles in the Phanerozoic successions have disclosed that a genetic link may be postulated for individual Earth shells and galactic precessional cycles.The stratigraphic records of the above mentioned cycles are significant especially for the division of the Precambrian strata with lower stratigraphic resolutions.