Subduction erosion of the Jurassic Talkeetna-Bonanza Arc and the Mesozoic accretionary tectonics of western North America

The Jurassic Talkeetna volcanic arc of south-central Alaska is an oceanic island arc that formed far from the North American margin. Geochronological, geochemical, and structural data indicate that the arc formed above a north-dipping subduction zone after ca. 201 Ma. Magmatism migrated northward in...

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Bibliographic Details
Published in:Geology (Boulder) 2005-11, Vol.33 (11), p.881-884
Main Authors: Clift, Peter D, Pavlis, Terry, DeBari, Susan M, Draut, Amy E, Rioux, Matthew, Kelemen, Peter B
Format: Article
Language:English
Subjects:
accretion
active margins
Alaska
Bonanza Group
British Columbia
Canada
Chugach Terrane
erosion
exhumation
Geology
Geophysics
island arcs
Islands
Jurassic
magmatism
Mesozoic
Naknek Formation
North America
plate collision
Plate tectonics
Sediments
Soil erosion
solid Earth (tectonophysics)
Southeastern Alaska
Southern Alaska
Stratigraphy
subduction
Talkeetna Mountains
Talkeetna-Bonanza Arc
terranes
trenches
United States
Upper Jurassic
Vancouver Island
Volcanoes
Western Canada
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Summary:The Jurassic Talkeetna volcanic arc of south-central Alaska is an oceanic island arc that formed far from the North American margin. Geochronological, geochemical, and structural data indicate that the arc formed above a north-dipping subduction zone after ca. 201 Ma. Magmatism migrated northward into the region of the Talkeetna Mountains ca. 180 Ma. We interpret this magmatism as the product of removal of the original forearc while the arc was active, mainly by tectonic erosion. Rapid exhumation of the arc after ca. 160 Ma coincided with the sedimentation of the coarse clastic Naknek Formation. This exhumation event is interpreted to reflect collision of the Talkeetna arc with either the active margin of North America or the Wrangellia composite terrane to the north along a second north-dipping subduction zone. The juxtaposition of accreted trench sedimentary rocks (Chugach terrane) against the base of the Talkeetna arc sequence requires a change from a state of tectonic erosion to accretion, probably during the Late Jurassic (before 150 Ma), and definitely before the Early Cretaceous (ca. 125 Ma). The change from erosion to accretion probably reflects increasing sediment flux to the trench due to collision ca. 160 Ma.
ISSN:0091-7613
1943-2682
DOI:10.1130/G21822.1