New Zealand Journal of Geology and Geophysics abstracts
Palinspastic reconstructions of southeastern Marlborough, New Zealand,
for mid-Cretaceous-Eocene times
James Crampton1
Malcolm Laird2
Andrew Nicol1
Dougal Townsend1
Russell Van Dissen1
1Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
email: j.crampton@gns.cri.nz
2Department of Geological Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
Abstract Southeastern Marlborough, New Zealand, preserves
many complete sections through the Cretaceous/Tertiary (K/T) boundary. Attempts
to understand the paleogeography of these sections are hampered by the pervasive,
Neogene deformation of the area associated with the propagation of the modern
Pacific/Australian plate boundary through New Zealand. In this paper, we produce
palinspastic maps of southeastern Marlborough for five intervals of Cretaceous
and Paleogene time, based on a retro-deformed, pre-Neogene geographic model.
Retro-deformation takes account of: displacements on five major faults; distributed,
between-fault shortening; and a uniform, vertical axis, clockwise rotation
of 100°. The mapped intervals are: (1) part of the Urutawan-Motuan (middle-late
Albian, c. 105-102 Ma); (2) the Piripauan (latest Coniacian to late Santonian,
86.5-84.5 Ma); (3) the Early to early Late Haumurian (late Santonian-Campanian,
84.5-72 Ma); (4) the late Late Haumurian to late Teurian (late Maastrichtian
to late Paleocene, 68-58 Ma); and (5) the Waipawan-Mangaorapan (early Eocene,
55-51 Ma). During the Cretaceous and Paleogene, southeastern Marlborough
lay on the generally north-facing, Pacific margin of proto-New Zealand. The
palinspastic maps record the progressive drowning of what we infer to be
a faulted platform, the “Marlborough paleo-platform”, that formed the eastern
boundary of a large embayment, the “Marlborough paleo-embayment”. In the
late Early and early Late Cretaceous, terrigenous clastic sediments were
deposited on the platform at mostly shelf to upper bathyal depths. Ngaterian
(late Albian-Cenomanian) and Piripauan (latest Coniacian to late Santonian)
paleoshorelines lay within the study area and were oriented northeast-southwest.
Subsequently, regional, passive subsidence of the continental margin resulted
in transgression towards the south and southeast and a switch from terrigenous
clastic to biogenic sedimentation. By the end of the Cretaceous, much of the
Marlborough paleo-platform was at outer shelf to bathyal depths; by the early
Eocene, it lay entirely at bathyal depths. During the latest Cretaceous and
Paleogene, the position of the Marlborough paleo-embayment coincided approximately
with a significant boundary in sedimentary regime, separating dominantly
biogenic sediments in the east from mixed biogenic-siliciclastic sediments
to the west. The palinspastic maps show internal consistencies that give
us some confidence in the new analysis. Differences from previous maps are
attributed both to the retro-deformation and also to variations in the locations,
values, and number of data points used to construct isopachs. Locally restoring
paleogeography by retro-deforming structures is likely to be of most use
where the amount of deformation is high (e.g., >20% shortening and/or
some tens of kilometres of fault displacements), where the isopachs are well
constrained by robust data points, and where regional or global controls
on sedimentary and biological patterns are significant and of interest.
Keywords Amuri Limestone; Cretaceous; Eocene; Herring
Formation; Marlborough; Mead Hill Formation; New Zealand; Paleocene; paleogeography;
palinspastic maps; Paton Formation; Split Rock Formation
G02025 Received 15 May 2002; accepted 23 December 2002; published 30 June
2003
New Zealand Journal of Geology & Geophysics, 2003, Vol. 46: 153-175
0028-8306/03/4602-0153 $7.00/0 © The Royal Society of New Zealand
2003
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