New Zealand Journal of Geology and Geophysics abstracts
The early Pliocene Titiokura Formation: stratigraphy of a thick,
mixed carbonate-siliciclastic shelf succession in Hawke’s Bay Basin,
New Zealand
Kyle J. Bland
Peter J. J. Kamp
Arne Pallentin
Rhys Graafhuis
Campbell S. Nelson
Vincent Caron
Department of Earth Sciences
The University of Waikato
Private Bag 3105
Hamilton 2001, New Zealand
Abstract This paper presents a systematic
stratigraphic description of the architecture of the early Pliocene Titiokura
Formation (emended) in the Te Waka and Maungaharuru Ranges of
western Hawke’s Bay, and presents a facies, sequence stratigraphic, and
paleoenvironmental analysis of the sedimentary succession. The
Titiokura Formation is of early Pliocene (Opoitian–Waipipian) age, and
unconformably overlies Mokonui Formation, which is a regressive late
Miocene and early Pliocene (Kapitean to early Opoitian) succession. In
the Te Waka Range and the southern parts of the Maungaharuru Range, the
Titiokura Formation comprises a single limestone sheet 20–50 m
thick, with calcareous sandstone parts. In the vicinity of Taraponui
Trig, and to the northeast, the results of 1:50 000 mapping show
that the limestone gradually partitions into five members, which
thicken markedly to the northeast to total thicknesses of c.
730 m, and concomitantly become dominated by siliciclastic
sandstone. The members (all new) from lower to upper are: Naumai
Member, Te Rangi Member, Taraponui Member,
Bellbird Bush Member, and Opouahi Member. The lower four
members are inferred to each comprise an obliquity-controlled
41 000 yr 6th order sequence, and the Opouahi Member at least two
such sequences. The sequences typically have the following
architectural elements from bottom to top: disconformable sequence
boundary that formed as a transgressive surface of erosion; thin
transgressive systems tracts (TSTs) with onlap and backlap shellbeds,
or alternatively, a single compound shellbed; downlap surface; and very
thick (70–200 m) highstand (HST) and regressive systems tracts
(RST) composed of fine sandstone. The sequences in the Opouahi Member
have cryptic TSTs, sandy siltstone to silty sandstone HSTs, and
cross-bedded, differentially cemented, fine sandstone RSTs; a separate
variant is an 11 m thick bioclastic limestone (grainstone and
packstone) at the top of the member that crops out in the vicinity of
Lake Opouahi. Lithostratigraphic correlations along the crest of the
ranges suggest that the Titiokura Formation, and its correlatives to
the south around Puketitiri, represent a shoreline-to-shelf linked
depositional system. Carbonate production was focused around a rocky
seascape as the system onlapped basement in the south, with dispersal
and deposition of the comminuted carbonate on an inner shelf to the
north, which was devoid of siliciclastic sediment input. The rates of
both subsidence and siliciclastic sediment flux increased rapidly to
the northeast of the carbonate “platform”, with active progradation and
offlap of the depositional system into more axial parts of Hawke’s Bay
Basin.
Keywords Pliocene; Opoitian; Waipipian; Hawke’s
Bay Basin; Te Aute limestone lithofacies; sequence stratigraphy;
Titiokura Formation; Naumai Member; Te Rangi Member; Taraponui Member;
Bellbird Bush Member; Opouahi Member; new stratigraphic names
G03062; Received 25 August 2003; accepted 19 May 2004; Online
publication date 1 December 2004
New Zealand Journal of Geology & Geophysics, 2004, Vol. 47:
675–695
0028–8306/04/4704–0675© The Royal Society of New Zealand 2004
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