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Mid-Cretaceous ductile deformation on the Eastern palmer land shear zone, Antarctica, and implications for timing of mesozoic terrane collision

By: Vaughan, Alan P. M.
Contributor(s): Kelley, Simon P | Storey, Bryan C.
Material type: ArticleArticleDescription: 465-471p.Subject(s): Mid cretaceous ductile deformation - Eastern palmer land shear zone - Antarctica | Implication - Mesozoic terrane collision - Antarctica | Structural geology - Antarctica | Tectonic boundary - Eastern palmer land shear zone - Antarctica peninsula In: Geological magazine : Vol. 139 Iss. 1-6 Year. 2002Summary: Abstract Ar–Ar dating of high-strain ductile mylonites of the Eastern Palmer Land Shear Zone in the southern Antarctic Peninsula indicates that reverse movement on the shear zone occurred in late Early Cretaceous times (Albian), and not latest Jurassic times as previously supposed. The Eastern Palmer Land Shear Zone forms a major tectonic boundary, separating suspect arc terranes from rocks of Gondwana continental affinity. The dated mylonites are developed in Lower Jurassic plutonic rocks at Mount Sullivan, eastern Palmer Land, and form part of a zone of ductile reverse deformation up to 25 km wide. Biotite from a fine-grained mafic mylonite yields an Ar–Ar cooling age of 102.8±3.3 Ma. Movement of this age on the Eastern Palmer Land Shear Zone is coeval with circum-Pacific deformation, possibly related to a mantle superplume event, and provides support for allochthonous-terrane models for the Antarctic Peninsula with accretion in post-Early Cretaceous times.
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Article Article Library and Information Centre
Periodical Section
Bound Journal Collection Not for loan 002519_62
Serials/Scientific Journal Serials/Scientific Journal Library and Information Centre
Periodical Section
Bound Journal Collection 550 GEO (Browse shelf) Available 002519

Abstract
Ar–Ar dating of high-strain ductile mylonites of the Eastern Palmer Land Shear Zone in the southern Antarctic Peninsula indicates that reverse movement on the shear zone occurred in late Early Cretaceous times (Albian), and not latest Jurassic times as previously supposed. The Eastern Palmer Land Shear Zone forms a major tectonic boundary, separating suspect arc terranes from rocks of Gondwana continental affinity. The dated mylonites are developed in Lower Jurassic plutonic rocks at Mount Sullivan, eastern Palmer Land, and form part of a zone of ductile reverse deformation up to 25 km wide. Biotite from a fine-grained mafic mylonite yields an Ar–Ar cooling age of 102.8±3.3 Ma. Movement of this age on the Eastern Palmer Land Shear Zone is coeval with circum-Pacific deformation, possibly related to a mantle superplume event, and provides support for allochthonous-terrane models for the Antarctic Peninsula with accretion in post-Early Cretaceous times.

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