新元古代十三里台期叠层石组合的地层对比意义

新元古代十三里台期辽南徐淮地区的叠层石组合以 Conophyton ocularoides与 Baicalia共生为特色 ,Inze-ria、Gymnosolen、Tungussia、Jurusania、L inella等的相继集中出现为代表 ,叠层石的丰度和分异度极高 ,达到叠层石演化史上的鼎盛时期。类似的叠层石组合在世界各地晚里菲期中频有发现。至马家屯期 ,叠层石进入逐步衰退阶段 ,叠层石多组成半球状生物岩礁 ,柱体细小、相互密集丛生、分叉复杂、大多具壁或鞘 ,柱间充填大量叠层石砾屑和陆源石英碎屑 ,同时叠层石微结构发生明显变化 ,出现特征的半球形放射纤维状组构。十三里台期叠层石组合特征明显、组分相对稳定 ,不仅在区域间 ,甚至在洲际间具有地层对比的潜力。

NEOPROTEROZOIC STROMATOLITE ASSEMBLAGES FROM THE SHISANLITAI STAGE AND ITS SIGNIFICANCE IN THE REGIONAL AND CONTINENTAL CORRELATION

Well developed in stratigraphic sequences, clear in boundaries, and rich in fossils, the northern Anhui-Jiangsu and southern Liaoning districts are the ideal regions for the study of the correlation and syntaxis of the Neoproterozoic in North China and Yangtze Platforms. Though the dating and correlation of the Upper Precambrian in the districts have long been a heated dispute, more and more researches are ready to ascribed it to the Sinian System in the Yangtze Platform owing to the finding of vermiform and cyclomedusa-like fossils, while, the study of stromatolites in the Shisanlitai and Weiji as well as Majiatun and Shijia Formations may greatly changes the view:1. The Shisanlitai Formation in southern Liaoning can be well correlated with the Weiji Formation in northern Anhui-Jiangsu, and both of them own the same stromatolitic assemblage characteriz by the paragenesis of Conophyton ocularoides and Baicalia and the occurrence of Inzeria, Gymnosolen, Tungussia, jurusania and Linella. Similar stromatolitic assemblage has frequently been found in the Upper Riphean worldwide, and its abundance and diversity reached a maximum in the time span, representing a most flourish period in the evolutionary history of stromatolite. 2. A gradual decline of stromatolites started at the Majiatun Stage, with a sharp reduce in both the diversity and abundance. Mainly forming hemispheric domed bioherms, the stromatolites are generally thin in columns, complex in branches, and common in wall or guard, with the filling of stromatolitic and quartz clasts in between, meanwhile, accompanied with an event occurrence of the tussocky microstructure on a basinal scale.