Burial history of Late Neogene sedimentary basins on part of the New Zealand convergent plate margin

Abstract

Burial histories of Late Neogene sedimentary basins on the Wairarapa fold and thrust belt of the Hikurangi convergent plate margin (New Zealand) have been deduced from decompacted sedimentary columns and palaeo‐waterdepths. These indicate that at least two major cycles of basement subsidence and uplift have occurred since 15 Ma. The older (15‐10 Ma) cycle affected outer areas of the forearc. Subsidence, at a minimum rate of 0.5‐0.6 mm/yr, was followed by rapid uplift. The subsequent (10 Ma to present) cycle affected a broad area of the inner forearc. Subsidence, at an average rate 0.33 mm/yr, was followed by uplift at an average rate of 0.5‐1.5 mm/yr. Vertical movement is continuing, with uplift of the axial greywacke ranges and development of the Wairarapa Depression. Palinspastic reconstructions of the inner forearc region indicate that basin development was characterized by a see‐saw oscillation in basin orientation, with the axis of the basin and direction of basin tilt switching back and forth from east to west through time. A large‐scale change in basin orientation took place around 2 Ma when the westernmost part of Wairarapa began to rise on the flanks of the rising Tararua Range, associated with the ramping of the Australian Plate up and over the subducted Pacific Plate. Loading of the forearc is unlikely to have been a significant cause of basement subsidence before this event. Earlier phases of basin development associated with basement subsidence and uplift may be related to a complex interplay of tectonic factors, including the westward migration of the subducted Pacific Plate as it passed beneath southern North Island during Miocene time, episodes of locking and unlocking of parts of the plate interface, and growth of the accretionary prism.

Deformation style and history of the Eketahuna region, Hikurangi forearc, New Zealand, from shallow seismic reflection data

“…The Eketahuna Group (Te) sediments are fine-grained sandstone, siltstone, mudstone, and turbidite units, and the Makuri Group (Tmk) comprises shallow water shelly sandstones interbedded with limestones. Stratigraphy of the Eketahuna Basin is similar to that of the Dannevirke and Wairarapa Basins to the north and south along the Hikurangi forearc (Wells 1989;Cape et al 1990;Melhuish 1990), with the exception that Miocene strata are less widespread and Pliocene-Pleistocene strata are thicker in the Dannevirke Basin.…”

“…has been deduced from stratigraphic, sedimentological, and paleontological evidence (Neef 1984;Wells 1989;Kelsey et al in press). From 10 Ma to c. 3 Ma the region occupied a subsiding forearc basin with water depths increasing throughout most of this time.…”

“…Wells (1989) considered ramping of the crust of the Australian plate up and over the subducted Pacific plate a plausible mechanism for uplift of the weste rn margin of the Wairarapa Basin since 2 Ma, but this mechsinism would not account for the long wavelength uplift of the Hikurangi forearc.…”

Sedimentary architecture of a Plio-Pleistocene proto-back-arc basin: Wanganui Basin, New Zealand

“…Earlier studies of the WB have concentrated on its geodynamic evolution (e.g. Garrick and Gibowicz, 1983;Wells, 1989;Stern et al, 1992;Ogilvie, 1993;Wilson and McGuire, 1995), its broad-scale seismic stratigraphy (Anderton, 1981;Ogilvie, 1993) and its petroleum potential (Katz and Leask, 1990;Thompson et al, 1994). However, the geodynamic and structural setting of the WB, together with the wealth of geological and geophysical data, provide an excellent opportunity to: (1) constrain the basin origin and history during the Pleistocene, (2) investigate the evolution of the margin-parallel sedimentary basins and (3) determine the contemporaneous processes of faulting, subsidence and sedimentation in a back-arc basin related to the active Hikurangi subduction margin.…”

Neogene development of the onland part of the forearc in northern Wairarapa, North Island, New Zealand: A synthesis

“…Studies useful in this synthesis are: structural divisions of the onland part of the forearc (Moore 1988); geology of the Mauriceville District (Orbell 1962); depth of deposition and burial history of Neogene strata in Wairarapa (Wells 1989); pioneering studies in late Quaternary faulting and sedimentation in northern Wairarapa (Vella 1962a(Vella ,b, 1963b; and seismic studies in southern and northern Wairarapa (Cape et al 1990;Lamarche et al 1995).…”