New Zealand Journal of Geology and Geophysics abstracts
Structural and lithological continuity and discontinuity in the
Otago Schist, Central Otago, New Zealand
D. J. MacKenzie
D. Craw
Geology Department
University of Otago
P.O. Box 56
Dunedin, New Zealand
Abstract The Otago Schist in Central Otago has
undergone complex late metamorphic and post-metamorphic deformation
during uplift and exhumation. Two late metamorphic structural
generations can be recognised and these may be genetically related. The
earlier Manorburn Generation has been widely recognised and described
previously. This generation has fold axes subparallel to a prominent
syn-metamorphic quartz rodding lineation. A later generation, herein
named Poolburn Generation, has folds which superficially
resemble Manorburn Generation, but has fold axes that are at a high
angle to the quartz rodding lineation. Both generations occur in
mappable fold zones (kilometre-scale) that are generally not vergence
boundaries, and some minor relative displacement may occur across fold
zones. Fold zones occur within structurally and lithologically uniform
schist domains. Abrupt changes in lithological sequences and
orientations of structural elements such as Manorburn and Poolburn
Generation fold axes and quartz rodding lineations occur at
post-metamorphic faults which separate different schist domains.
Central Otago schist can be subdivided on the regional scale (tens of
kilometres) into at least nine schist domains whose structural and
lithologic continuity is disrupted by fault discontinuities. The
domains and bounding discontinuities developed during Late Jurassic and
Early Cretaceous uplift. Syn-metamorphic compressive ductile
deformation evolved to localised fold zones in the early stages of this
uplift. Subsequently, regional extension caused juxtaposition of
domains with different textural zones, and schists from slightly
different structural levels. The Caples/Torlesse Terrane boundary is a
composite feature, and different segments formed at different stages
through the transition from ductile compression to brittle extensional
deformation.
Keywords Otago Schist; structure; folds; faults;
lineations; lithology; domains
G04013; Received 15 March 2004; accepted 3 November 2004; Online
publication date 25 May 2005
New Zealand Journal of Geology & Geophysics, 2005, Vol. 48:
279–293
0028–8306/05/4802–0279© The Royal Society of New Zealand 2005
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