New Zealand Journal of Geology and Geophysics abstracts
Parapara Group: Permian-Triassic rocks in the Western Province,
New Zealand
H. J. CAMPBELL1
D. SMALE2
R. GRAPES3
L. HOKE1,3
G. M. GIBSON4
C. A. LANDIS5
1Institute of Geological & Nuclear Sciences
P.O. Box 31 312
Lower Hutt, New Zealand
228 Bronte Street
Nelson, New Zealand
3Research School of Earth Sciences
Victoria University of Wellington
P.O. Box 600
Wellington, New Zealand
4Australian Geological Survey Organisation
G.P.O. Box 378
ACT 2601, Canberra, Australia
5Department of Geology
University of Otago
P.O. Box 56
Dunedin, New Zealand
Abstract The Parapara Group of northwest Nelson is a faulted
sequence of folded and metamorphosed Permian-Triassic sedimentary rocks.
Stratigraphically, from bottom to top, the sequence consists of: massive black
Draco Slate (new term), at least 200 m thick; Flowers Formation,
which consists of the Pupu Conglomerate Member (20 m thick), Cross
Member (new term; 35 m thick), Tarn Sandstone Member (new term;
35 m thick), and Pariwhakaoho Slate Member (30 m thick); and Walker
Formation (>200 m thick).
Fossils in the Cross Member indicate a Middle Permian (Ufimian-Kazanian) age
and have long been recognised as having affinities with similar faunas in
Tasmania and eastern Australia. Dropstones within the Draco Slate and Flowers
Formation indicate glacial influence. The geochemical composition of sandstones
suggests a dominant continental arc source for the Parapara Group sediments.
Thin (<5 m) porphyry sills (mainly trachyandesite) of the Parapara
Peak Intrusives (new term) intrude the Draco Slate and Flowers Formation
and are correlated with the Separation Point Suite.
The whole sequence has been deformed by Mesozoic regional recumbent folding
(D1) with development of a penetrative axial planar cleavage (S1) at low grade
greenschist facies (M1) metamorphic conditions. The intrusion of sills during
the Early Cretaceous is concomitant with a more regional upper greenschist to
amphibolite facies prograde metamorphism with M2 porphyroblasts of garnet,
biotite, chloritoid, chlorite, +/- green hornblende, +/- epidote and ilmenite
overgrowing the S1 foliation. Post-M2 deformation (D2) produced kilometre-scale
synclinal folds. The M2 minerals were deformed within the fold axial planar
crenulation cleavage (S2) developed best in the nose of D2 folds. The grade of
metamorphism increases progressively down-section (i.e., eastwards), from
high-grade greenschist facies (Walker Formation) to amphibolite facies (Draco
Slate).
Keywords Gondwanaland; New Zealand, Western Province;
Austrazean; Parapara Group; stratigraphy; Draco Slate; Flowers Formation;
Walker Formation; Parapara Peak Intrusives; geochemistry; metamorphism;
structure; Middle Permian; Triassic; fossils; new stratigraphic names
New Zealand Journal of Geology and Geophysics, 1998, Vol. 41: 281-296
0028-8306/98/4103-0281 $7.00/0 (c) The Royal Society of New Zealand
1998
PDF file of entire paper: medium quality (3352K); (scanned from paper original: notes about this process)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
