长江下游南京到当涂一段,有一个由侏罗纪象山层所组成的向北东方向延长约50公里、宽约20公里的纺缍形构造向斜(宁芜大向斜)凹陷,在此凹陷内普遍堆积了白垩纪建德系火山杂岩。笔者暂把这个地区称为“马鞍山火山岩区”,本文主要论述该区南部(即北纬31°45′以南这片地区)的地质情况(见图1)。 Nanjing to Dangtu in the lower reaches of the Yangtze River has a spur-shaped tectonic syncline (Ningwu major syncline) depression extending about 50 km north-eastward and about 20 km wide in the Jurassic age. Cretaceous Jiande volcanic complex is generally accumulated in the depression. The author tentatively refers to this area as the “Ma’anshan Volcanic Rock Area”. This article mainly discusses the geological conditions in the southern part of the area, that is, the area south of 31 ° 45’N. (See Figure 1).