论文部分内容阅读
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 world-famous Miriam section of Neoproterozoic in Jixian, Tianjin, with a thickness of nearly 10,000 meters and a distribution period of about 100 Ma (180 ~ 60 0 Ma). Based on lithofacies and facies sequences, sedimentary sequences at different levels and their superimposed patterns are the core of the study. Sixty-three third-order sequences were identified in this huge Precambrian stratigraphy and can be further classified as 2 2 second level sequence, 4 first level sequence. The four first-level super-sequences not only represent the depositional cycles of 200 Ma to 400 Ma with periods of 180 Ma to 60 Ma, but also Phallus and two first-order cycles, indicating that the A series of major variations have obvious genetic connection with the Galactic year cycle. Although it is difficult to accurately estimate the absolute deadline of the discontinuities represented by the discontinuities belonging to different depositional sequences in the stratigraphic records, the study of the recurrent stratigraphic records based on lithofacies and facies sequences is complicated Incomplete stratigraphic records find an effective way to find more regularity; especially, the pre-Cambrian strata, which have a low resolution of the biostratigraphy, are even more important.