Structural and geochronologic relations along the western flank of the Coast Mountains Batholith; Stikine River to Cape Fanshaw, central southeastern Alaska

W. C McClelland; G. E Gehrels; S. D Samson; P. J Patchett

doi:10.1016/0191-8141(92)90107-8

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Structural and geochronologic relations along the western flank of the Coast Mountains Batholith; Stikine River to Cape Fanshaw, central southeastern Alaska

Journal article

Peer reviewed

Structural and geochronologic relations along the western flank of the Coast Mountains Batholith; Stikine River to Cape Fanshaw, central southeastern Alaska

W. C McClelland, G. E Gehrels, S. D Samson and P. J Patchett

Journal of structural geology, Vol.14(4), pp.475-489

04/1992

DOI: 10.1016/0191-8141(92)90107-8

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Abstract

Geological and U-Pb geochronological studies in central SE Alaska provide constraints on the mid-Cretaceous to mid-Tertiary deformation W of the Coast Mountains batholith. The NE-dipping Sumdum and Fanshaw faults record the W-directed emplacement of the Ruth assemblage (Yukon-Tanana terrain) and Taku terrain over the subjacent Gravina belt and Alexander terrain. Ductile fabrics of the Sumdum-Fanshaw fault system truncate early formed foliation and thrust faults in Albian and older Gravina belt strata. U-Pb age data from syn- and post-tectonic plutons suggest that deformation was ongoing at 92.9 +- 3.0 m.y. but had mostly ceased by 90 m.y. The Sumdum-Fanshaw fault system marks the tectonic boundary between the Alexander-Wrangellia terrain and inboard Yukon-Tanana and Stikine terrains and lies within a thrust belt that extends from S Alaska to N Washington. Mid-Cretaceous structures are truncated to the east by NE-dipping ductile fabrics of the Coast shear zone. Sheet-like Palaeocene tonalites were emplaced into and deformed within the shear zone. Undeformed mid- Eocene dykes cross-cut the tonalites. Kinematic relations in the Coast shear zone suggest a complex displacement history that includes both east-side up (reverse) and west-side up (normal) shear. The shear zone probably accommodated the collapse of overthickened crust developed during mid-Cretaceous shortening. [Authors' abstract]

absolute age

Alaska

Alexander Terrane

batholiths

Cape Fanshaw

Cenozoic

Coast Mountains

Cretaceous

dates

deformation

diorites

ductile deformation

Geochronology

Gravina Belt

igneous rocks

intrusions

Mesozoic

North America

plutonic rocks

plutons

shear zones

southeastern Alaska

Stikine River

Structural geology

tectonics

terranes

Tertiary

tonalite

U/Pb

United States

Yukon-Tanana Terrane

Details

Title: Subtitle: Structural and geochronologic relations along the western flank of the Coast Mountains Batholith; Stikine River to Cape Fanshaw, central southeastern Alaska
Creators: W. C McClelland - University of Arizona
G. E Gehrels - University of Arizona
S. D Samson - University of Arizona
P. J Patchett - University of Arizona
Resource Type: Journal article
Publication Details: Journal of structural geology, Vol.14(4), pp.475-489
Publisher: Pergamon
DOI: 10.1016/0191-8141(92)90107-8
ISSN: 0191-8141
eISSN: 1873-1201
Language: English
Date published: 04/1992
Academic Unit: Earth and Environmental Sciences
Record Identifier: 9984229292702771

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