天津蓟县雾迷山旋回层基本模式及其马尔柯夫链分析  

The Basic Model of Wumishan Cyclothems and Their Markov Chain Analysis, Jixian Section of Tianjin

作　　者：梅冥相[1] 马永生[2] 郭庆银[1] 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国石化集团,北京100029

出　　处：《高校地质学报》2001年第3期288-299,共12页Geological Journal of China Universities

基　　金：国家自然科学基金项目 (4 980 2 0 12 );九五攀登专项 (SSER)成果之一

摘　　要：天津蓟县剖面的中元古界雾迷山组 ,是一套碳酸盐岩地层 ,具近似对称相序组构的环潮坪型碳酸盐米级旋回层序特别以育。其近似对称的相序组构及普遍的 1∶4叠加形态 ,表明它们与短偏心率旋回具有成因关联 ,被命名为雾迷山旋回层来代表真正的碳酸盐沉积旋回。雾迷山旋回层是与高频率海平面变化相关的环境加深及环境变浅过程的产物。马尔柯夫链分析的结果表明了雾迷山旋回层的基本相序模式是客观存在的 ,由于它们以瞬时暴露间断面为界 ,因而与Vail等(1977)的层序地层概念体系中所定义的“准层序”存在明显的差异。尽管难以断定前寒武纪地球轨道效应旋回的周期完全与显生宙一致 ,但是 ,七级韵律层、六级旋回层及五级准层序组之间的垂直叠置形态 ,以及由它们所指示的周期时限 。The Mesoproterozoic Wumishan Formation in Jixian section of Tianjin is composed of 3300m thick carbonate strata with a duration of about 100Ma (1310±20Ma-1207±10Ma). In this set of strata, particularly carbonate meter scale cyclic sequences belonging to peritidal type with approxirately symmetrical lithofacies succession fabric are developed very well. The widespread development of superimposed patterns of 1∶4 shows that these meter scale cyclic sequences are genetically related to the short eccentricity cycles, which are called figuratively Wumishan cyclothems and could represent true sedimentary cycles. Generally, massive and thick bedded limedolostones and dolomitic limestones of stromatolite biostromes and thrombolte bioherms constitute the central part of Wumishan cyclothems, the bottom and upper part are consisted of tidal flat dolostones, the top part is composed of lagoon facies dolomitic shales with a cap of paleosol layers. Therefore, the approximately symmetrical lithofacies succession fabric is formed. Many features such as the clear deepening and shoaling vectors of cyclothems, and all kinds of fresh water diagenesis marks suggest that the Wumisham cyclothems are the products of autocyclic sedimentation governed by allocyclic high frequency sea level changes. The results of Markov chain analysis reaffirmed the objective existence of lithofacies succession fabric of Wumishan cyclothems. The boundaries of Wumishan cyclothems are marked by instantaneous exposed punctuated surface, which lead to the discrepancy between the cyclothem and the parasequerce of sequence stratigraphy terminology system defined by Vail et al. (1977). It is difficult to judge that the time span of Milankovitch cycles in Precambrian is certainly equal to those of the Phanerozoic, but the regularly vertical stacking patterns of seventh order rhythms, sixth order cyclothems and fifth order partasequence sets still indicate their consistence with the period duration of Milankovitch cycles in the Phanerozoic

关 键 词：雾迷山旋回层 马尔柯夫链分析 中元古界 天津蓟县 迷山组 碳酸盐岩地层 

分 类 号：P534.3[天文地球—古生物学与地层学]