New Zealand Journal of Geology and Geophysics abstracts
NB: This paper has been republished in a corrected version in the September
issue
Thermal history of the early Miocene Waitemata Basin and adjacent Waipapa
Group, North Island, New Zealand
ASAF RAZA1
RODERICK W. BROWN1
PETER F. BALLANCE2
KEVIN C. HILL1
PETER J. J. KAMP3
1Department of Earth Sciences
La Trobe University
Bundoora, Victoria, Australia
2Department of Geology
The University of Auckland
Private Bag 92019
Auckland, New Zealand
3Department of Earth Sciences
The University of Waikato
Private Bag 3105
Hamilton, New Zealand
Abstract Apatite fission track (AFT) and vitrinite
reflectance (VR) data for early Miocene outcrops from the Waitemata Basin
reveal that the basin sequence was subjected to shallow burial before
denudation. AFT results suggest that the total sediment thickness within the
basin was <=1 km and maximum paleotemperatures during burial never
exceeded c. 60deg.C. Statistical analyses of the detrital AFT ages
distinguish four dominant sources of sediment supply: contemporaneous
volcanism; metagreywacke rocks of the Waipapa Group; the Northland Allochthon;
and an unidentified source south of the basin.
The apatite and zircon fission track results from the Waipapa Group rocks
(Gondwana Terrane) adjacent to the basin suggest two discrete phases of
accelerated cooling: the first during the early Cretaceous
(c. 117 Ma) and the second during the mid Cretaceous
(c. 84 Ma). These events probably reflect key stages in the tectonic
development of the New Zealand microcontinent during the Cretaceous period, the
earlier event being related to the climax of compressional deformation
(Rangitata Orogeny) and the latter to extensional tectonism associated with the
opening of the Tasman Sea. Waipapa Group rocks now exposed at the surface
cooled from maximum paleotemperatures of c. 250deg.C at an estimated rate
of c. 180-36deg.C/m.y., involving substantial denudation.
Keywords Waitemata Basin; fission track analysis;
geochronology; vitrinite reflectance; provenance; Waipapa Group; Miocene; mid
Cretaceous; continental extension
New Zealand Journal of Geology and Geophysics, 1999, Vol. 42: 169-188
0028-8306/99/4202-0169 $7.00/0 (c) The Royal Society of New Zealand
1999
PDF file of entire paper: medium quality (2104K); (scanned from paper original: notes about this process)
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