湘西北上震旦统碳酸盐层序地层

碳酸盐层序地层应考虑碳酸盐＂加工厂＂、气候条件、构造背景、沉降速率、与陆地连接情况和底质类型等多种因素。碳酸盐层序地层模式在大多数情况下有别于Ｖａｉｌ的碎屑岩层序地层模式，并且气候条件是一个值得多加考虑的因素。通过不同相区碳酸盐层序地层的划分，笔者建立了研究区上震旦统碳酸盐层序地层模式，即陵山沱期为缓坡背景碳酸盐层序地层模式，灯影期为碳酸盐台地（初始）背景层序地层模式。在高水位体系域中识别出早期高水位体系域和晚期高水位体系域。已识别出浅潮下和环潮坪两种不同类型的副层序旋回。通过层序地层分析，笔者认为陡山沱底部的白云岩属于低水位楔。

ON THE CARBONATE SEQUENCE STRATIGRAPHY IN UPPER SINIAN IN NORTHWEST HUNAN, SOUTH CHINA

The model of carbonate sequence stratigraphy is dissimilar to siliciclastic rocks of Exxon company) so many controlling factors which are unique to carbonate sequence, such as "carbonate factory", climate ) tectonic background, rate of subsidence and link with land should be taken into account. It was proposed that there were two models of carbonate sequence stratigraphy during upper Sinian, which are carbonate ramp during Doushantou stage and carbonate platform during Denyin stage respectively. The early high stand system tracts and late high stand system tracts are identifiend and two types of carbonate high frequency cycles, shallow subtidal and peritidal meter-scale cycles, are distinguished within inner ramp and platform on outcrops. Based on analysis of sequence stratigraphy, it is suggested that the dolomite on the lowest bottom of Nantou Formation is sediments of lower stand system tracts and that the extensive dlolomitization and evaporate are relative to dry climate in this area.