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Latest Mesozoic and Cenozoic magmatism in southeastern Alaska

By
David A. Brew
David A. Brew
U.S. Geological Survey
,
345 Middlefield Road, Menlo Park, California 94025
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Published:
January 01, 1994

Abstract

The most important latest Mesozoic and Cenozoic, postaccretionary geologic features of southeastern Alaska are those related to the magmatic activity that affected a large part of the region and to the resultant metamorphism and deformation. The metamorphic history is discussed elsewhere in this volume (Dusel-Bacon, this volume), and the magmatic activity is a continuation of the late Mesozoic activity discussed by Miller (this volume). Postaccretionary geologic history starts with the accumulation of the Gravina belt overlap assemblage of rocks in Late Jurassic and Early Cretaceous time (Berg and others, 1972). The locally voluminous volcanic rocks within that assemblage are probably the extrusive equivalents of island-arc intrusive rocks, which are preserved west of the Gravina belt over a large area in northern southeastern Alaska (Brew and Morrell, 1983). Neither the volcanics nor the granitoids are discussed in this chapter.

Previous syntheses concerned with the magmatic rocks of southeastern Alaska comprise a summary of post-Carboniferous volcanic activity (Brew, 1968), summaries of the distribution and general characteristics of the plutonic rocks (Brew and Morrell, 1980, 1983), a summary of the geochronologic data available (Wilson and Shew, 1982), and two reports concerned with the tectonic significance of major- and trace-element chemical data (Barker and Arth, 1984; Barker and others, 1986). Karl and Brew (1984) discussed migmatitic rocks associated with some of the intrusive rocks; that topic is not considered in this report.

In this chapter, the latest Mesozoic and Cenozoic magmatic rocks are grouped chronometrically (Table 1); the same time divisions are used elsewhere

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Contents

DNAG, Geology of North America

The Geology of Alaska

George Plafker
George Plafker
U.S. Geological Survey MS 904, 345 Middlefield Road Menlo Park, California 94025
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Henry C. Berg
Henry C. Berg
115 Malvern Avenue Fullerton, California 92632
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Geological Society of America
Volume
G-1
ISBN electronic:
9780813754536
Publication date:
January 01, 1994

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