New Zealand Journal of Geology and Geophysics abstracts
The Cambrian arc complex of the Takaka Terrane, New Zealand: an integrated
stratigraphical, paleontological and geochemical approach
CARSTEN MüNKER
Institut für Geologie und Dynamik der Lithosphäre
and Geochemisches Institut
Goldschmidtstr. 3
37077 Göttingen, Germany
Present address: Zentrallabor für Geochronologie, Mineralogisches
Institut, Universität Münster, Corrensstr. 24, 48149 Münster,
Germany.
ROGER COOPER
Institute of Geological & Nuclear Sciences
P.O. Box 30368
Lower Hutt, New Zealand
Abstract The Cambrian succession of the Takaka Terrane
represents a volcano-sedimentary arc complex, which was once part of the
Pacific margin of Gondwana. The succession has been folded and disrupted by
faulting during at least four tectonic events, bringing together at least 12
fault slices with dissimilar stratigraphy. A revised stratigraphy and regional
models for lithofacies relationships, magmatic history, and tectonic setting
are proposed. They are based on analysis of the lithostratigraphy,
biostratigraphy, petrology, geochemistry, geochronology, and field
relationships. Volcanic rock formations recognised are Benson Volcanics (arc),
Mataki Volcanics (back-arc), and Cobb Igneous Complex (boninites), which are
all grouped in the Devil River Volcanics Group. Petrography and trace element
geochemistry enable discrimination of the volcanic units of the Devil River
Volcanics. Rocks of the Benson Volcanics are by far the most voluminous and are
subdivided into nine (informal) volcanic suites. Arc activity lasted from
middle Mid Cambrian (Undillan) to Late Cambrian (Mindyallan or younger), about
20 m.y., constrained by ages based on trilobites, brachiopods, and conodonts in
interbedded sediments and U-Pb and Ar-Ar dates. This period of arc activity is
different from those in Tasmania and southeast Australia, where
post-collisional volcanism commenced in the late Mid Cambrian. A separate
igneous unit in the Takaka Terrane is the rift-related Gendarme Dolerite of
latest Cambrian to early Ordovician age. Sedimentary formations recognised are
Tasman Formation, Mount Benson Sandstone (new), Ruby Saddle Formation
(new), Lake Peel Formation (new), Lockett Conglomerate, Christmas
Conglomerate, Salisbury Conglomerate, and Heath Creek beds, all comprising the
Haupiri Group, and the Junction Formation (group unassigned). Rocks of the
Haupiri Group were deposited in a back-arc or intra-arc setting.
Keywords Cambrian; volcanic arc; geochemistry; stratigraphy;
Takaka Terrane; back arc; boninites; ultramafics; provenance; melange; Mount
Benson Sandstone; Salisbury Conglomerate Formation, Christmas Conglomerate
Formation, Ruby Saddle Formation; Lake Peel Formation; Benson Volcanics,
Gendarme Dolerite; new stratigraphic names
New Zealand Journal of Geology & Geophysics, 1999, Vol. 42:
415-445
0028-8306/99/4203-0415 $7.00/0 (c) The Royal Society of New Zealand
1999
PDF file of entire paper: medium quality (9120K); (scanned from paper original: notes about this process)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
