Marine seismic measurements in the New Zealand region

Abstract

Seismic profiler data recorded by USNS Eitanin in the vicinity of New Zealand are used to delineate the major features of the sediment distribution in the region, particularly on the marginal plateaus. Sonobuoy data have given basement depths in some areas where the sediment cover is too thick to be profiled and also information on sediment velocities, enabling estimates to be made of sediment thicknesses. A strong reflector, probably Late Cretaceous-Early Tertiary in age, occurs over a large portion of the survey area. Flat-lying sediments of Tertiary age, thicker than 2 km, occur in the morphological depressions of New Caledonia Basin, southern Hikurangi Trench, and Solander Trough. Bounty Trough however has a relatively thin sediment cover. Deep sedimentary troughs, also containing at least 2 km of sediments, exist at the south-west of Campbell Plateau, along the southern margin of Pukaki Rise, and along the eastern margin of South Island from south of Banks Peninsula to Snares Depression.

Extensional and magmatic nature of the Campbell Plateau and Great South Basin from deep crustal studies

“…Velocities derived from data of one sonobuoy (Davey, 1977) northeast of the Pukaki Rise are 6.6 km/s for the basement. This value seems to be too high and may be due to the sonobuoy's unreversed nature.…”

“…The Campbell Plateau (Fig. 1) is a continental plateau (Davey, 1977) that lies mostly at less than 1000 m beneath sea level, rising up to 500 m at the Pukaki Rise and emerges at the Auckland and Campbell Islands.…”

An Eocene to early Oligocene unconformity‐bounded sequence in the Punakaiki‐Westport area, West Coast, South Island, New Zealand

“…The fault is found in seismic lines north of Westport (Davey 1977). Movement on the fault in the Eocene is not well constrained.…”

“…Eocene sediment thicknesses on the western side of the fault determined from seismic lines and drilling (Haku 1, see Laird 1970Laird ,1988Fig. 1) are very small or nonexistent, suggesting that the western side of the fault was upthrown and was exposed for much of the Eocene (Laird 1970;German 1976;Davey 1977;Anderson 1984;Nathan et al 1986;Laird 1988;Lever 1999).…”

Seismic stratigraphy and structural history of the Reinga Basin and its margins, southern Norfolk Ridge system

“…Tectonic deformation of the Reinga Basin was noted by Davey (1977) and discussed by Eade (1988) who attributed compressional structures in the Reinga and New Caledonia Basins and uplift of the West Norfolk and Wanganella Ridges to the Eocene compression that led finally to obduction of the New Caledonia ophiolite in the Early Oligocene, In Eade's model the Wanganella Ridge is portrayed as a large southwest-directed thrust. Although the case for Eocene compression in New Caledonia is well documented (e g., Parrot & Dugas 1980;Regnier 1988;Aitchison et al 1995), there is no evidence of contemporaneous compression in nearby northern New Zealand (Isaac et al 1994).…”