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一、分布和地层划分(一)分布北美地台和周围造山带是世界前寒武纪地层主要分布区之一(图Ⅲ-1)。由巨大的加拿大地盾,包括北极区、大平原区、东落基山和中部大陆区在内的北美台坪,以及周围的科迪勒拉褶皱带、因奴特褶皱带、东格陵兰褶皱带和阿巴拉契亚褶皱带组成(表Ⅲ-1)。前寒武系在本大陆的所有构造单元中均广泛发育,尤其广泛分布于加拿大—格陵兰地盾中,据知它是世界上最广阔而又连续的前寒武岩层,只有哈得孙湾区为水域或古生界所覆。地盾东部出露较差,巴芬和拉布拉多海隐伏着北美大陆和格陵兰的前寒武基底之间的密切构造联系,格陵兰除一条狭窄的海岸外,全部为冰雪掩没。
I. DISTRIBUTION AND STRATIGRAPHY (A) DISTRIBUTION The North American platform and surrounding orogenic belts are one of the main distributions of Precambrian stratigraphy in the world (Figure III-1). The huge Canadian shield, North American terraces, including the Arctic, Great Plains, East Rockies and the Central Region, and the surrounding Cordillera fold belt, Inuit fold belt, East Greenland fold belt and Appalachian fold belt composition (Table III-1). Precambrian widespread in all tectonic units in the continent, especially in the Canada-Greenland shield, which is known to be the most extensive and continuous Precambrian in the world. Only the Hudson Bay For the water or Paleozoic covered. Poor exposure to the eastern shield, Baffin and the Labrador Sea hide the close contact between the North American continent and the Precambrian base in Greenland, Greenland, with the exception of a narrow coast, all covered with snow and ice.