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古代冰期的确定完全依赖于正确地认识冰川沉积作用和刻蚀现象,这是一项很细致的工作,下面对通常使用的标志作一次讨论。1.无分选的岩性—晚期前寒武纪“冰碛岩”常常是厚度巨大的卵石建造。这种没有分选的岩性与上、下非卵石层形成明显的对照。卵石岩层象冰碛而不像砾岩,其中或多或少夹有砂质泥岩(包括钙质含量较高的类型),并含有不同比例的分散状卵石、中砾和漂砾。这种岩石类型十分引人注目,也很易鉴别,甚至从奔驰火车的窗口也能判
The determination of ancient glaciers is entirely dependent on a correct understanding of glacial sedimentation and etching. This is a very detailed work. The commonly used symbols are discussed below. 1. Unselected Lithology - Late Precambrian “moraine rocks” are often thick pebbles. This unselected lithology forms a clear contrast with the upper and lower non-pebble layers. Pebble beds resemble moraines rather than conglomerates, with more or less sandstone shale (including those with a higher calcium content) and different proportions of scattered pebbles, gravel and boulders. This rock type is very compelling and easy to identify, even from the Mercedes Benz window