摘要:

Modern nontropical skeletal carbonate sediments are presently forming over 20% of New Zealand's continental shelf within or next to the obliquely convergent Australia-Pacific plate boundary. Their distribution is inversely related to terrigenous sedimentation rates, which steadily increase towards the plate boundary. There is a broad separation of major skeletal types into different associations with distance from the plate boundary, bivalve-foraminiferal assemblages dominating on the forearc shelves and bryozoan or bryozoan-bivalve assemblages in backarc regions.

ISSN:0028-8306    

DOI:10.1080/00288306.1988.10417807

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

At Ohinewai, South Auckland, New Zealand most of the 200 m of overburden on Paleogene coal measures comprises terrestrial sediments of the late Neogene Tauranga Group. A detailed study of 15 continuous cores through these deposits located 16 stratigraphically unconfined lithofacies which, on the basis of preferred associations, have been grouped into 5 major lithofacies assemblages. These assemblages are lithologically correlatable with formations previously established for the group, including the Whangamarino, Puketoka, and Karapiro Formations. Five pollen zones are recognised within the Tauranga Group, ranging in age from Late Miocene to Holocene. The constituent formations at Ohinewai are older and span a longer time period than previously determined. Key spore and pollen types are used to date the sequence, but several anomalies exist suggesting that northern North Island may have formed a late Neogene refuge for many plants that became extinct earlier elsewhere in New Zealand.

ISSN:0028-8306    

DOI:10.1080/00288306.1988.10417808

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Banks Peninsula consists of Late Miocene alkalic to transitional volcanic rocks erupted from two major composite volcanoes (Lyttelton and Akaroa) and a host of minor monogenetic vents. Four volcanic groups are defined in this paper:Lyttelton(11-9.7 Ma),Mt Herbert(9.7-8.0 Ma),Akaroa(9.0-8.0 Ma), andDiamond Harbour(7.0-5.8 Ma). Three further formations, which are petrographically distinct and volumetrically minor, were erupted between 8.1 and 7.3 Ma, marking the transition from Akaroa to Diamond Harbour volcanism.

ISSN:0028-8306    

DOI:10.1080/00288306.1988.10417809

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Radial dikes of Lyttelton Volcano, Banks Peninsula, New Zealand, are mainly hawaiite, with basalt, mugearite, and trachyte next in abundance. Spatial distribution of compositional types is not regular, one interpretation being that the proportion of trachyte increased with time. Analysis of dike numbers suggests there were 2000 near the volcanic centre, and <500 at the level of the eroded crater rim. Dikes have a blade shape with the long axis horizontal. Flow directions are dominantly along that axis with significant deviations up to 90° either side. Dike traces are marked by bends and offsets of as much as 125 m. Most dikes are <1.5 m thick, but they range up to 20 m. Thickness changes slowly horizontally outwards, but quickly vertically; many dikes thicken upwards to the point where they feed flows and domes, or have been cut off by penecontemporaneous erosion. Dikes played a major role in the construction of the volcano, probably a continuous role. A modern analogue is Etna.

ISSN:0028-8306    

DOI:10.1080/00288306.1988.10417810

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Two well-defined virtual geomagnetic poles (VGPs) for East Antarctica were obtained from the Middle Jurassic Ferrar Dolerite, sampled from a thick sill on Mt Schopf in the Ohio Range, and from a horizontal sheet intruding Paleozoic granitic rocks at Mt Cerberus in the Dry Valleys. The VGP from the sill at Mt Schopf lies at lat. 58°.0S, long. 129°.0W (dm=13°, dp=12°), and the VGP from Mt Cerberus lies at lat. 57°.8S, long. 135°.7W (dm=6°, dp=6°). Rocks from both localities have normal polarity magnetisations. These data, together with 15 other acceptable pole positions reported in the literature, define a Middle Jurassic paleomagnetic pole at 52°.7S, 139°.6W (α95=4°.4), which is not significantly different from previously reported mean Middle Jurassic paleomagnetic poles from East Antarctica.

ISSN:0028-8306    

DOI:10.1080/00288306.1988.10417811

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Four months of magnetic records from the Eyrewell Observatory near Christchurch, New Zealand, have been digitised, and analysed to produce Parkinson response arrows. The magnitudes and azimuths of both the real and quadrature arrows are smooth functions of period. Real arrows at three particular periods are similar to arrows published previously for the earlier observatory at Amberley, some 43 km northeast of Eyrewell. Differences between the Eyrewell and Amberley arrows are consistent with effects due to the closer proximity of Amberley to the ocean, the different analysis techniques employed in the various studies, and possibly with some local geological effects.

ISSN:0028-8306    

DOI:10.1080/00288306.1988.10417812

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The Waiho Loop terminal moraine lies c. 10 km in front of the 10 km long Franz Josef Glacier in Westland, New Zealand. In 1978 an age of 11450 ± 200 years B. P. (NZ4234A) was reported forin situwood embedded in silt and overlain by glacial sediments 1.6 km behind the moraine. In late 1983 two more wood specimens were collected at the latter site and five radiocarbon ages were obtained. Four samples from the same log were dated, two at the New Zealand Institute of Nuclear Sciences, DSIR, at 11 500 ± 200 and 11 700 ± 200 years B. P. (NZ6573A and NZ6923A), and two at separate laboratories in the United States at 12 100 ± 275 (GX10053) and 12 510 ± 120 years B. P. (Beta 12 607). The second wood specimen was also dated in a U.S. laboratory at 12 120 ± 400 years B. P. (GX9981). The three New Zealand dates suggest an age of 11 550 years for the wood specimens while the three U. S. dates suggest an age of c. 12 420 years. Differences in sample pretreatment may account for the disparity between the New Zealand and U. S. age determinations. All these results indicate that the Waiho Loop was formed before the cold Younger Dryas Chron (11000–10 000 years B. P.) in Europe. Similarly situated moraines in Canterbury and southern Argentina are possible correlatives of the Waiho Loop. The Younger Dryas climatic oscillation cannot be shown to be represented by moraines in the middle latitudes of the Southern Hemisphere.

ISSN:0028-8306    

DOI:10.1080/00288306.1988.10417813

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In the upper drainage basin of Mata River, a tributary of the Waiapu River, hilltop height accordances at two levels, 500–580 m and 560–640 m above sea level, are observed. Both hilltop height accordances are inferred to represent erosion surfaces developed over folded Neogene rocks. The lower erosion surface is estimated from geomorphological position relative to the Mangamaunu Upland and tephrochronology to have been formed during a period of 25 000–30 000 years from prior to c. 35 000 years ago to c. 12 400 years ago (late Otiran). This lower erosion surface is not an elevated peneplain but was originally formed at a high level similar to its present altitude. The lower erosion surface was probably formed by cryoplanation under cooler and slightly drier climatic conditions than present with a sparse vegetation cover. The age of the higher erosion surface is not known but it must be much older than c. 35 000 years.

ISSN:0028-8306    

DOI:10.1080/00288306.1988.10417814

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The δ13C signal from calcareous nannofossils in marine sediments may provide a valuable new tool for measuring the13C content of ocean surface waters in the past. Measurements of Quaternary nannofossils from Deep Sea Drilling Project Site 593 on Challenger Plateau, off western New Zealand, indicate that the difference in the δ13C of nannofossils and benthic foraminifers, defined as Δ13C, is strongly correlated (r = +0.78) with the δ18O climatic signal, and has promise as an indicator of local paleoproductivity. The isotopic data suggest that, compared with interglacial episodes, there was a general increase in the productivity of surface waters in the southern Tasman Sea during glacial episodes, possibly as a result of intensification of ocean circulation patterns and upwelling currents in the region.

ISSN:0028-8306    

DOI:10.1080/00288306.1988.10417815

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A newly discovered outcrop of the Alpine Fault at Kaka Creek, central Westland, New Zealand, shows successive overthrusting of green mylonite and schist over alluvial and talus/scree gravels. From the southwestern bank, two rare wood fragments from the underlying gravels yield radiocarbon ages of 2600 ± 60 and 3350 ± 100 years B. P., and date two movements of the Alpine Fault. A minimum of 5.0 ± 0.1 m movement perpendicular to the Alpine Fault trend over 750 years corresponds to an average convergence rate of 6.7 ± 1.5 mm/year, the rate determination limited primarily by the small amount of outcrop remaining. On the northeastern bank, similar gravels have been overthrust a distance of 70 m by a 60 m thickness of schist, and the calculated thrusting rate and average convergence rate are likely to be considerably higher. The young ages of the underlying gravels confirm very recent, rapid movement of the Alpine Fault, possibly associated with frequent large seismic events in central Westland.

ISSN:0028-8306    

DOI:10.1080/00288306.1988.10417816

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor