Journal article
Cretaceous-Tertiary evolution of the western Coast Mountains, central Southeastern Alaska
Special papers (Geological Society of America), Vol.343, pp.159-182
2000
DOI: 10.1130/0-8137-2343-4.159
Abstract
The Coast Mountains orogen in central southeastern Alaska records intra-arc mid-Cretaceous underthrusting of the Alexander terrane and Gravina belt beneath metamorphic rocks correlative with the Yukon-Tanana terrane followed by evolution of the Late Cretaceous and early Tertiary Coast shear zone. U-Pb geochronologic data from the Bradfield Canal and Stikine River regions demonstrate that arc-related plutonism continued from mid-Cretaceous to Eocene time, synchronous with deformational evolution of the orogen. The southwest-vergent mid-Cretaceous Sumdum fault separates the Gravina belt from the Yukon-Tanana terrane, which in this region is dominated by a Middle to Late Devonian arc assemblage. Mid-Cretaceous plutons that crosscut this structure suggest that juxtaposition of the Yukon-Tanana terrane and Gravina belt occurred prior to ca. 90 Ma. Structures related to mid-Cretaceous contraction and pluton emplacement are truncated and overprinted by the Coast shear zone along the western flank of the Coast Mountains. Complex domainal kinematic relationships associated with ductile fabrics of the shear zone indicate a complex and protracted west-and east-side-up and possible dextral strike-slip displacement history. Simple geometric considerations and kinematic observations support a model in which this structure accommodated buoyancy-driven Late Cretaceous exhumation of the underthrust Alexander terrane followed by Paleocene-Eocene exhumation of rocks within the Coast Mountains. This younger exhumation was synchronous with tonalite and granodiorite pluton emplacement within and east of the shear zone. Limited kinematic data support a strike-slip origin for the shear zone. The shear zone likely evolved between 80 and 85 Ma and deformation continued at least through 57 Ma but ceased prior to 50 Ma.
Details
- Title: Subtitle
- Cretaceous-Tertiary evolution of the western Coast Mountains, central Southeastern Alaska
- Creators
- William C McClelland - University of California at Santa Barbara, Department of Geological Sciences Santa Barbara, CA USA United StatesJames M Mattinson
- Contributors
- Harold H Stowell (Editor) - University of Alabama, Department of Geology Tuscaloosa, AL USA United StatesWilliam C McClelland (Editor)
- Resource Type
- Journal article
- Publication Details
- Special papers (Geological Society of America), Vol.343, pp.159-182
- Publisher
- Geological Society of America (GSA)
- DOI
- 10.1130/0-8137-2343-4.159
- ISSN
- 0072-1077
- eISSN
- 2331-219X
- Alternative title
- Tectonics of the Coast Mountains, Southeastern Alaska and British Columbia
- Language
- English
- Date published
- 2000
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229293502771
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