安徽巢北地区五通组沉积环境分析

The Analysis on the Depositional Environment of Wutong Formation in Northern Chaohu Area,Anhui

下扬子地区广泛发育泥盆系五通组地层,因为处于海侵初期,地层中陆相和海相特征共存,导致对该组沉积环境认识上的分歧;安徽巢北地区泥盆系五通组为一套厚层砂岩夹泥岩组合,其沉积环境和沉积特征一直不清。为此,在前人研究成果和野外剖面实测基础上,采用沉积学、地层学等方法,结合室内磨片和粒度分析方法,对其厚层砂岩段进行了详细分析,研究发现巢湖地区五通组形成于海相沉积环境,即具滚动组分和跳跃组分组成的多段式的后滨—前滨,跳跃组分和悬浮组分组成的两段式的前滨—上临滨,有跳跃组分和悬浮组分组成的两段式的沙泥混合坪,结合沉积序列特点和沉积特征,最终确定五通组的观山段下部为滨岸相的后滨—前滨的砾石海滩沉积,观山段上部为滨岸相的前滨—上临滨的砂质海滩沉积,擂鼓台段下部为滨岸相的混合坪粉砂岩泥岩沉积,擂鼓台段中部为滨岸相的泥坪、海湾、滨岸沼泽沉积间有前滨的砂质海滩沉积,擂鼓台段上部为滨岸相的含铁质的混合坪沉积。该文不仅具有理论价值,也具有一定的教学示范作用。

The stratum of Wutong Formation of Devonian is developed widely in Lower Yangtze area. Because it is at the early stage of transgression,there coexists,the continental and marine features which causes the difference in understanding sedimentary environment of this formation. The stratum of Wutong Formation of Devonian in northern Chaohu area of Anhui is a combination of thick sandstone with mudstone,and the depositional characteristics and depositional environment are unclear all the time. So,based on the research results of predecessors and analysis of outcrops,associated with the means of sedimentology,stratigraphy and grain size analysis under the microscope,we analyze the thick sandstone section in detail and find that Wutong Formation is developed in marine environment,that is it has backshore-foreshore of multi-segment pattern that is composed of rolling component and jumping component,foreshore-upper shoreface of bi-segment pattern that is composed of jumping component and suspending component,and mixed flat of siltstone and mudstone of bi-segment pattern that is composed of jumping component and suspending component. Combining with the characteristics of sedimentary sequences and sedimentary characteristics,we can draw a conclusion that the lower part of Guanshan Member in Wutong Formation is gravel beach deposition of backshoreforeshore subfacies,the upper part is sand beach deposition of foreshore-upper shoreface subfacies. The lower part of Leigutai Member in Wutong Formation is siltstone-mudstone deposition of mixed flat subfacies; the middle part is mudstone of bay mudflat subfacies and coastal marsh subfacies with sand beach deposition of foreshore subfacies; the upper part is chalybeate mixed flat deposition of littoral facies. This paper not only has theoretical value,but also has a certain teaching significance.