New Zealand Journal of Geology and Geophysics abstracts
K-Ar ages of early Miocene arc-type volcanoes in northern New Zealand
BRUCE W. HAYWARD
PHILIPPA M. BLACK
IAN E. M. SMITH
PETER F. BALLANCE
Department of Geology
University of Auckland
Private Bag 92019
Auckland, New Zealand
TETSUMARU ITAYA
MASAKO DOI
MIKI TAKAGI
Research Institute of Natural Sciences
Okayama University of Science
1-1 Ridai-cho
Okayama, 700-0005, Japan
STEVE BERGMAN
ARCO
Dallas
Texas, USA
CHRIS J. ADAMS
RICHARD H. HERZER
Institute of Geological & Nuclear Research
P.O. Box 30 368
Lower Hutt, New Zealand
DAVID J. ROBERTSON
Department of Physics
University of Namibia
Private Bag 13301
Windhoek, Namibia
Abstract Understanding the temporal and spatial development
of the early Miocene Northland Volcanic Arc is critical to interpreting the
patterns of volcanic activity in northern New Zealand through the late
Cenozoic. The northwesterly trending arc is considered to have developed
above a southwest-dipping subduction system. The distribution of its
constituent eruptive centres is described in terms of an eastern belt that
extends along the eastern side of Northland and a complementary broad western
belt which includes subaerial and submarine volcanic edifices. Critical
examination of all 216 K-Ar ages available, including 180 previously
unpublished ages, and their assessment against tectonic, lithostratigraphic,
seismic stratigraphic, and biostratigraphic constraints, leads us to deduce a
detailed chronology of periods of activity for the various early (and middle)
Miocene arc-type volcanic complexes and centres of northern New Zealand:
Waipoua Shield Volcano Complex (19-18 Ma, Altonian); Kaipara Volcanic Complex
(23-16 Ma, Waitakian-Altonian); Manukau Volcanic Complex (c. 23-15.5 Ma,
Waitakian-Clifdenian); North Cape Volcanic Centre (23-18 Ma,
Waitakian-Altonian); Whangaroa Volcanic Complex (22.5-17.5 Ma,
Waitakian-Altonian); Taurikura Volcanic Complex (22-15.5 Ma,
Otaian-Clifdenian); Parahaki Dacites (22.5-18 Ma, Waitakian-Altonian); Kuaotunu
Volcanic Complex (18.5-11 Ma, Altonian-Waiauan). In general, volcanic activity
does not show geographic migration with time, and the western (25-15.5 Ma) and
eastern (23-11 Ma) belts appear to have developed concurrently.
Keywords K-Ar ages; volcanic arc; geochronology; New Zealand;
Northland; Auckland; Waitakere Group; Coromandel Group; Parahaki Dacite; North
Cape; Karikari; Whangaroa; Waipoua; Kaipara; Tokatoka; Hukatere; Whangarei
Heads; Hen and Chickens Islands; Waitakere Ranges; Miocene
New Zealand Journal of Geology & Geophysics, 2001, Vol. 44:
285-311
0028-8306/01/4402-0285 $7.00/0 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (5659K); (scanned from paper original: notes about this process)
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