New Zealand Journal of Geology and Geophysics abstracts
Late Miocene to early Pliocene stratigraphic record in northern
Taranaki Basin: condensed sedimentation ahead of Northern Graben
extension and progradation of the modern continental margin
Rochelle J. Hansen
Peter J. J. Kamp
Department of Earth Sciences
The University of Waikato
Private Bag 3105
Hamilton 2001, New Zealand
Abstract The middle Pliocene–Pleistocene
progradation of the Giant Foresets Formation in Taranaki Basin built up
the modern continental margin offshore from western North Island. The
late Miocene to early Pliocene interval preceding this progradation was
characterised in northern Taranaki Basin by the accumulation of
hemipelagic mudstone (Manganui Formation), volcaniclastic sediments
(Mohakatino Formation), and marl (Ariki Formation), all at bathyal
depths. The Manganui Formation has generally featureless wireline log
signatures and moderate to low amplitude seismic reflection
characteristics. Mohakatino Formation is characterised by a sharp
decrease in the GR log value at its base, a blocky GR log motif
reflecting sandstone packets, and erratic resistivity logs. Seismic
profiles show bold laterally continuous reflectors. The Ariki Formation
has a distinctive barrel-shaped to blocky GR log motif. This signature
is mirrored by the SP log and often by an increase in resistivity
values through this interval. The Ariki Formation comprises
(calcareous) marl made up of abundant planktic foraminifera, is
109 m thick in Ariki-1, and accumulated over parts of the Western
Stable Platform and beneath the fill of the Northern Graben. It
indicates condensed sedimentation reflecting the distance of the
northern region from the contemporary continental margin to the south.
Keywords Taranaki Basin; Northern Graben; Manganui
Formation; Mohakatino Formation; Ariki Formation; Mangaa Formation;
Giant Foresets Formation; Whangamomona Group; Rangitikei Supergroup;
condensed sedimentation
G03044; Received 30 April 2003; accepted 27 January 2004; Online
publication date 1 December 2004
New Zealand Journal of Geology & Geophysics, 2004, Vol. 47:
645-662
0028-8306/04/4704-0645© The Royal Society of New Zealand 2004
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