克拉通边缘盆地碳酸盐层序地层学分析——以华北板块东部早古生代沉积为例

首次对华北板块东部早古生代克拉通边缘盆地的碳酸盐地层进行层序地层学剖析,认为从寒武纪至早奥陶世加积、侧积的碳酸盐层序主要受海平面升降所制约,为历时约110 Ma的一个海进—海退旋回,是与全球海平面升降同步的超周期(二级旋回,P.R.Vail,1978)。而且海面升高与海侵同步,其间被Ⅰ、Ⅱ型层序界面不整合分隔为四个层序。海面升降模式是缓慢的海进,快速的海退,在主体海退过程中层序界面及海面降低控制着蒸发岩(石膏)矿床的形成。对长期争议的“三山子”白云岩的成因问题提出了新认识:“三山子”白云岩系海面区际性下降过程中,淡水渗流作用下形成的准同生交代白云岩,并随海面向北退却而使白云岩化向北推移且层位升高,是穿时性的“淡水透镜体”的向盆迁移,是区际性层序界面不整合的重要标志。

SEQUENCE ANALYSIS ON CRATON MARGIN CARBONATE:AN EXAMPLE FROM THE EARLY PALAEOZOIC SEDIMENTS IN EASTERNAL NORTH CHINA PLATE

This paper for the first time made the sequence stratigraphic analysis on craton margin carbonate deposited in early Palaeozoic on the eastern North China plate. It has been recognized that the aggredational and lateral accretional carbonate sequence of Cambrian - early Ordovician were controlled by eustatic movement, representing a transgressive - regressive cycle, a superpariod (2nd order cycle, P. R.,Vail, 1978), synchronous to the global eustasy. The transgressive series during the rising of sea level is separated by I and II types of unconformities into four sequences. The mode of the eustatic movements was represented by slow transgression and rapid regression. It was the sequence boundary and the downing of sea level that controlled the appearence of evaporites(gypsum deposits) in the major period of regression.As to the long disputed problem on the origination of the " sanshanzi Dolomite", the writers have proposed a new view: the "sanshanzi Dolomite" was produced by syngenetic replacement incorporated with fresh water infiltration during the regional downing of sea -level. Following the northward retreat of the sea, the dolomitization process migrated northward and developed into higher horizon resulted in basinward shifting diachnonic fresh water dolomite lense-an important indication of the regional unconformity between sequence bounderies.