Correlation chart for Precambrian rocks of the Eastern United States

Abstract

In the Eastern United States, Precambrian rocks are exposed in the Adirondack massif and in the Appalachian orogen. Rocks dated at 1,300-1,000 m.y. occur as outliers of the Grenville province of Canada. These rocks constitute a western basement to the Appalachian orogen and appear in the Adirondack massif, in anticlinoria along the Blue-Green-Long axis, and in gneiss domes farther east. The Chain Lakes massif in Maine, about 1,500 m.y. old, may represent a different block of continental crust. Rifting of the Grenville continental mass, accompanied by anorogenic igneous activity, began about 820 m.y. ago.