Transcontinental Proterozoic provinces
Published:January 01, 1993
J. Lawford Anderson, E. Erik Bender, Raymond R. Anderson, Paul W. Bauer, James M. Robertson, Samuel A. Bowring, Kent C. Condie, Rodger E. Denison, M. Charles Gilbert, Jeffrey A. Grambling, Christopher K. Mawer, C. K. Shearer, William J. Hinze, Karl E. Karlstrom, E. B. Kisvarsanyi, Edward G. Lidiak, John C. Reed, Jr., Paul K. Sims, Odgen Tweto, Leon T. Silver, Samuel B. Treves, Michael L. Williams, Joseph L. Wooden, 1993. "Transcontinental Proterozoic provinces", Precambrian, John C. Reed, Jr., Marion E. Bickford, R. S. Houston, Paul Karl Link, D. W. Rankin, Paul K. Sims, W. Randall Van Schmus
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Research on the Precambrian basement of North America over the past two decades has shown that Archean and earliest Proterozoic evolution culminated in suturing of Archean cratonic elements and pre-1.80-Ga Proterozoic terranes to form the Canadian Shield at about 1.80 Ga (Hoffman, 1988,1989a, b). We will refer to this part of Laurentia as the Hudsonian craton (Fig. 1) because it was fused together about 1.80 to 1.85 Ga during the Trans-Hudson and Penokean orogenies (Hoffman, 1988). The Hudsonian craton, including its extensions into the United States (Chapters 2 and 3, this volume), formed the foreland against which 1.8- to 1.6-Ga continental growth occurred, forming the larger Laurentia (Hoffman, 1989a, b). Geologic and geochronologic studies over the past three decades have shown that most of the Precambrian in the United States south of the Hudsonian craton and west of the Grenville province (Chapter 5) consists of a broad northeast to east-northeast-trending zone of orogenic provinces that formed between 1.8 and 1.6 Ga. This zone, including extensions into eastern Canada, comprises or hosts most rock units of this age in North America as well as extensive suites of 1.35- to 1.50-Ga granite and rhyolite. This addition to the Hudsonian Craton is referred to in this chapter as the Transcontinental Proterozoic provinces (Fig. 1); the plural form is used to denote the composite nature of this broad region.
The Transcontinental Proterozoic provinces consist of many distinct lithotectonic entities that can be defined on the basis of regional lithology, regional structure, U-Pb ages from zircons, Sr-Nd-Pb isotopic signatures, and regional geophysical anomalies.
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This wide-ranging discussion of Precambrian rocks includes contributions from a diverse array of authors actively engaged in investigations of various aspects of U.S. Precambrian geology. Summary discussions by the editors of the five major chapters place these contributions in a logical regional framework. A concluding chapter explores Archean crustal processes from the point of view of lunar and planetary analogies, discusses the significance of Sm crustal provinces, and provides an overview of the development of the southern parts of Laurentia. Accompanying plates include a newly compiled map of the Precambrian rocks of the conterminous U.S., maps showing relationships of the Precambrian geology to magnetic anomalies and to isostatic residual gravity, and a new correlation chart for U.S. Precambrian rocks.