徐州地区新元古界贾园组臼齿构造沉积环境分析及成因探讨

Sedimentary environments and genesis of the molar-tooth structures in the Neoproterozoic Jiayuan Formation in the Xuzhou region,Jiangsu

臼齿构造是一种发育于中、新元古代碳酸盐岩中的具有特殊结构和时限性的沉积构造,其成因有多种解释。徐州地区新元古界贾园组风暴沉积及臼齿构造发育。本文通过野外和室内观察研究,对研究区贾园组臼齿构造形态特征及沉积环境进行分析,并探讨其形成过程。贾园组臼齿构造集中发育于古纬度20°N^34°N的潮下碳酸盐岩缓坡地带,古海洋基底在地震波作用下产生裂隙系统,元古代特殊大气成分背景下的海水中的远源风暴流渗透进入温暖的碳酸盐缓坡地带碳酸盐沉积区的裂隙系统,并在裂隙的愈合作用下与孔隙水产生化学反应产生方解石快速结晶作用,并接受后期沉积作用改造。元古代大地构造背景、古海洋、古大气的物理化学条件是控制研究区臼齿构造时空分布的主要因素。

The molar-tooth structures,a special kind of sedimentary structures with special textures and restricted time duration only developed in the Meso-to Neoproterozoic carbonate rocks are observed in the storm deposits from the Neoproterozoic Jiayuan Formation in the Xuzhou region,Jiangsu. The morphology,sedimentary environment and genesis of molar-tooth structures are treated in this study in terms of field observation and laboratory study. The molar-tooth structures in the Jiayuan Formation appear in the ramp zones of the subtidal carbonate rocks at the latitudes of 20°N to 34°N. The distal storm currents penetrated into the fissure systems produced by the earthquakes on the ancient marine basement,led to the chemical reactions with the pore-space water,and finally led to the rapid crystallization of calcite. The physical and chemical conditions of the Proterozoic oceans and atmospheres and tectonic settings are interpreted as the main factors controlling the spatio-temperal distribution of the molar-tooth structures.