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Book Chapter

Precambrian geology and tectonic history of North America

By
Paul F. Hoffman
Paul F. Hoffman
Geological Survey of Canada, Ottawa, Ontario K1A 0E4, Canada
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Published:
January 01, 1989

Abstract

North America is an old continent. Whereas South America and Africa were not assembled until 0.7 Ga, and the assembly of Eurasia began at 0.3 Ga, most of the North American craton has been coherent since 1.7 Ga. This craton, known as Laurentia, included Greenland and northwest Scotland until their partial separation in the Late Cretaceous. This chapter describes the constituents of Laurentia, their aggregation in the Early Proterozoic (Table 1), and subsequent adventures of the craton until the rifting events at the end of the Proterozoic, which gave the continent approximately its present shape.

Radiogenic isotopic data from the Precambrian shield, and from inliers and subsurface samples on the platform indicate that about 55 percent of the area of the craton separated from the mantle in the Archean and about 45 percent in the Proterozoic (Fig. 1). In this regard, the shield is not representative of the craton as a whole, being strongly biased in favor of Archean crust (Fig. 2). Conversely, most of the Proterozoic crust underlies the Phanerozoic sedimentary veneer of the southern interior platform.

The Archean protocraton of Laurentia is an aggregate of seven former microcontinents (Fig. 1): the familiar Superior, Wyoming, Slave, and Nain (North Atlantic) provinces, and the newly recognized Hearne, Rae, and Burwell provinces (formerly parts of the composite Churchill province). The Rae province includes northern, southwestern, and southeastern prongs. Each province is a Late Archean crustal aggregate and contains variable proportions of Early and/or Middle Archean crust. Early Proterozoic rifting and subsequent collisional deformation govern the dimensions of the provinces.

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Figures & Tables

Contents

DNAG, Geology of North America

The Geology of North America—An Overview

Albert W. Bally
Albert W. Bally
Department of GeologyP.O. Box 1892Houston, Texas 77251
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Allison R. Palmer
Allison R. Palmer
Geological Society of America3300 Penrose Place, P.O. Box 9140Boulder, Colorado 80301
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Geological Society of America
Volume
A
ISBN electronic:
9780813754451
Publication date:
January 01, 1989

GeoRef

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