安徽宿松上石炭统碳酸盐岩台地沉积物定量分析与海平面变化

安徽宿松地区上石炭统碳酸盐岩发育,厚约100m,化石丰富,属于比较典型的浅海碳酸盐岩台地沉积。定量分析显示,研究区岩石类型主要为颗粒灰岩和泥粒灰岩,颗粒平均含量分别为81.2％和69.6％,以浅海生物碎屑为主;其次为粒泥灰岩和泥晶灰岩,颗粒平均含量分别为26.4％和4.1％。依据岩石学特征,研究区主要发育开阔台地相和潮坪相,并可进一步划分出5种沉积亚相,分别是台内滩、台内盆、台内坪、潮间坪和潮上坪。在研究区上石炭统中共识别出3个长期的海进—海退旋回,其表现出在海平面变化总体呈下降趋势的背景之上叠加了短期的高频海平面波动的特征。这3个旋回与扬子板块其他地区及欧美板块同时代地层中的长期海进—海退旋回相当,表明海平面的变化可能受到晚古生代冈瓦纳大陆冰川的冰期和间冰期交替活动的影响。

Quantitative analysis of carbonate platform sediments and sea-level changes of the Upper Carboniferous in Susong area,Anhui Province

The Upper Carboniferous carbonate rocks,with 100meters thickness and abundant fossils,were well developed in Susong area of Anhui Province. These rocks belonged to the typical shallow carbonate platform deposits. The grains quantitative analysis showed that the lithofacies mainly included grainstones and packstones with the content of 81.2％ and 69.6％ respectively; and shallow marine bioclasts predominated. Moreover,there were wackstones and lime mudstones with the grains content of 26.4％ and 4.1％ respectively. The open-marine platform facies and tidal flat facies were mainly developed in study area,which could be divided into five types of subfacies including intra-platform shoal,intra-platform basin,intra-platform flat and inter-tidal flat and supra-tidal flat. Combining the above characteristics,three long-term transgressive-regressive cycles could be recognized from the Upper Carboniferous. The sea-level changes were characterized by the high frequency short-term sea-level fluctuations superimposing on a long-term sea-level fall. These three cycles were roughly corresponding to the long-term transgressive-regressive cycles in other areas of Yangtze Plate and the same-time strata in Euramerican Plate. It also indicated that the sea-level changes were influenced by alternation of the glacial period and non-glacial period in Gondwana.