Continental Alaska has been the site of widespread magmatism throughout much of the late Mesozoic and Cenozoic, but until recently, most of this magmatism was unrecognized due to the lack of modern geologic maps or isotopic age data for large tracts of Alaska. Although parts remain unmapped, progress in reconnaissance mapping and dating have enabled workers to identify major late Mesozoic and Cenozoic magmatic provinces outside the well-known Aleutian arc and to speculate as to their tectonic implications and origin (Wallace and Engebretson, 1984).
This chapter defines major Late Cretaceous and Cenozoic magmatic provinces in Alaska outside the Aleutian arc (Kay and Kay, this volume; Vallier and others, this volume; Miller and Richer, this volume) and southeast Alaska (Brew, this volume), and discusses their distribution, age, petrology, and tectonic implications. The available data suggest that Late Cretaceous and Cenozoic magmatism in continental Alaska can be roughly divided into three periods: (1) latest Cretaceous and early Tertiary (76 to 50 Ma), (2) middle Tertiary (43 to 37 Ma), and (3) late Tertiary and Quaternary (6 Ma to the present). Late Cretaceous and early Tertiary calc-alkalic volcanism and plutonism were widespread over much of western, central, and southern Alaska and on the Bering Sea shelf. Middle Tertiary magmatism was characterized by the eruption of small volumes of calcalkalic rocks in interior Alaska, contemporaneous with the inception of a major pulse of magmatism in the Aleutian arc. Late Tertiary and Quaternary volcanism has been characterized by the eruption of voluminous basaltic magma at
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The Geology of Alaska
You get a comprehensive overview of the geology, tectonic evolution, and mineral resources of Alaska and adjacent areas of the continental margin. Plates include state-wide maps showing geology, physiography, lithotectonic terranes, metamorphic rocks, igneous rocks, sedimentary basins, isotopic age data, neotectonics, isostatic gravity, magnetics, and metallic mineral deposits. Summaries of bedrock geology and geologic history are given for eleven large regions of Alaska and adjacent offshore areas. Twenty topical chapters synthesize data on metamorphic and igneous rocks; major onshore and offshore sedimentary basins; the paleomagnetics evidence for latitudinal displacements and rotations, glacial history and periglacial phenomena; and the occurrence, evolution, and potential of Alaska's vast resources of petroleum, coal, and metallic minerals. A summary chapter provides an overview and presents a possible model for Alaska's Phanerozoic evolution. The Geology of Alaska is the largest publication produced in the Decade of North American Geology program, a fitting tribute to this magnificent area.