在前寒武纪北美大陆至少可明显地划分出三个构造层,即下、中和上前寒武系,反映了三个巨大的发展阶段。每一个阶段在大地构造、物质组成的性质、褶皱作用、侵入活动和变质作用等方面都有它自己的特点。下前寒武系构造层实际上又包括两层:阿尔丹层35—33亿年;基瓦丁层33—25亿年。这种划分目前在北美大陆的大部分地区还不可能做到。对阿尔丹层的构造特点,目前资料还很少,仅仅可以证实这层在北美大陆是存在的,它经受了复杂的、普遍的、高强度的沉积变质作用,经受了剧烈的不止一次的构造 In the Precambrian North American continent, at least three tectonic strata can be clearly divided, that is, lower, middle and upper Precambrian, reflecting three huge stages of development. Each stage has its own characteristics in the tectonics, the nature of the material composition, the fold, the intrusion and the metamorphism. The Lower Precambrian structural layer actually consists of two layers: 35-33 billion years in the Ardan layer and 3.3-25 billion years in the basal layer. This division is currently impossible in most parts of North America. For the tectonic features of the Althian layer, at present, there is still very little data to prove that this layer exists in the North American continent. It has undergone complex, widespread and intensive depositional metamorphism and has undergone severe and more than once tectonics