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Cenozoic deep-sea sedimentation in the southwest Pacific area was controlled by large changes in the patterns of bottom-water circulation and erosion. The circulation patterns were largely controlled by

The Reinga Basin northwest of the North Island of New Zealand was initially formed by crustal extension in Cretaceous time. Gravity models suggest up to 35-40% crustal thinning. The seismic stratigraphy of the basin is continuous with that of the offshore western North Island, where reflectors are well constrained by oil exploration data. In the Reinga Basin, there are two Cretaceous sequences above an older Mesozoic basement. The lower sequence is apparently terrestrial and may include both pre-rift and synrift subsequences; the upper is a rift-filling marine sequence. These are overlain by Paleocene and Eocene blanket sequences that were laid down during a period of relative tectonic quiescence consistent with cooling subsidence, continued submergence, a northeast-facing continental shelf, and absence of a significant active plate boundary. A strong regional reflector, caused by a combined unconformity and G97011Received 13 February 1997; accepted 14 August 1997 Oligocene condensed sequence, separates the Paleogene and Neogene sequences.The Neogene sequences record sedimentary infill from several source directions, not only from the New Zealand landmass, but from the north and west as well. Near the Northland coast, sediment accumulated in clastic wedges and ponded sub-basins from the Miocene to the present day. Along the flanking ridges to the northwest, similar deposition occurred in the Early and Middle Miocene but changed in the Late Miocene to sedimentation in drifts flanked by scours. This change reflects the end of tectonism, a diminishing clastic sediment supply, and the establishment of a throughgoing oceanic current regime as the marginal ridges submerged. This pattern of sedimentation persists today.Post-Cretaceous volcanism occurred in two parts of the basin. In the central southeastern part, volcanic bodies in the ?Oligocene to Early Miocene sequences could be a northwestern extension of the Northland volcanic arc. In the western part, small intrusive and extrusive bodies appear to be of Pliocene intraplate origin.Compression (or transpression) had an important role in developing the basin's present form. Miocene compressional structures-asymmetric anticlines, reverse faults, everted basins, and pop-ups-are present everywhere but at the southeastern end. The present marginal ridges have structurally complex origins. The Reinga Ridge which forms the northeastern margin is a transform boundary with the Norfolk backarc basin. Deformation thought to be caused by the action of the transform is recorded in folded and faulted Cretaceous-Paleogene sequences and syntectonic Early and Middle Miocene sequences along its length. The southwestern margin of the basin is a double ridge comprising the Wanganella Ridge, an early Middle to early Late Miocene, compressional uplift, and the older, eroded West Norfolk Ridge, which contains Cretaceous halfgrabens. The northern half of the Wanganella Ridge is an everted ?Oligocene to Early Miocene aulacogen in which slivers of basement rock were thrust up alo...

New mapping on the Chatham Islands, coupled with many new fossil determinations, has significantly refined our understanding of stratigraphic relationships of the Cretaceous-Cenozoic rocks exposed there. The following units are recognisable: Waihere Bay Group (emended), Tupuangi Formation (redefined; 240-400 m; Late Albian-Santonian), Pitt Island Group (emended), Kahuitara Tuff « 225 m; Campanian-Maastrichtian), Southern Volcanics (>300 m; Campanian-Maastrichtian), unnamed Cretaceous sandstone (>0.3 m; Late (?) Cretaceous), unnamed Haumurian limestone (fissure fills; Late Maastrichtian), Tioriori Group (emended), Takatika Grit (c. 6 m;