New Zealand Journal of Geology and Geophysics abstracts
Torlesse greywacke and Haast Schist source for Pliocene conglomerates near
Reefton, New Zealand
NICK MORTIMER
Institute of Geological & Nuclear Sciences
Private Bag 1930
Dunedin, New Zealand
RUPERT SUTHERLAND
SIMON NATHAN
Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
Abstract Late Miocene-Quaternary conglomerates in the
Inangahua valley record provenance changes which can be related to tectonic
activity in the northern South Island. Conglomerate clasts within the early
Miocene Rotokohu Coal Measures comprise mainly metamorphosed quartzose
greywacke with subordinate granitoids, consistent with an essentially local
clastic source from west of the Alpine Fault. In contrast, conglomerates of the
late Pliocene Old Man Group (Larry Schist and Cronadun Conglomerates) are
dominated by Rakaia Terrane (Older Torlesse) greywacke and Haast Schist clasts
from east of the Alpine Fault, which is c. 50 km southeast of the study area. A
complete range of textural and metamorphic grades is present, confirming that
oligoclase zone Alpine Schist was being exhumed during Pliocene time. The
50-70¡-dipping Pliocene beds are unconformably overlain by subhorizontally
dipping late Quaternary gravels (Tophouse and Speargrass Formations), which,
like the Miocene conglomerates, are composed of quartzose greywacke and
granitoid rock types. Significant Quaternary deformation isolated the Inangahua
valley area from the Southern Alps and resulted in a return to a local clastic
provenance.
Keywords Old Man Group; Buller; Alpine Fault; Pliocene;
provenance; petrology
New Zealand Journal of Geology & Geophysics, 2001, Vol. 44:
105-111
0028-8306/01/4401-0105 $7.00/0 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (682K); (scanned from paper original: notes about this process)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
