ISSN:0028-8306    

DOI:10.1080/00288306.1967.10423217

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Earthquake activity in the southern seismic region of New Zealand extends to intermediate depths. This has hitherto been suggested on the evidence of isoseismal patterns and seismogram characteristics, and is now confirmed by computation for the Lake Te Anau earthquake of 20 May 1965, for which 45 readings of P. supported by readings of p′, pP, sP, and PP, indicate a depth of 103 ± 5 km. This result adds to the reasons for classifying the region as an active margin between the New Zealand continental mass and the Tasman Sea.

ISSN:0028-8306    

DOI:10.1080/00288306.1967.10423218

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Recent magnetic and gravity surveys in the Nelson region permit a fuller discussion of the nature of the long major magnetic anomaly associated with the trend of the Nelson Syncline. The previous view that the anomaly is due to buried Upper Paleozoic igneous rocks such as the Brook Street Volcanics and Rotoroa Igneous Complex is held to be incompatible in some ways with the relationships between gravity and magnetic force values and with the physical properties of these rocks. It is suggested that a buried serpentinised ultramafic system might be the most appropriate geological model to explain the anomalies; and that the Dun Mountain Ultramafics may either have been emplaced directly from this system, or may be the surface expression of these anomalies displaced to the east as part of a sheet-type movement.

ISSN:0028-8306    

DOI:10.1080/00288306.1967.10423219

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

An eruption of mud and steam at Raoul Island on 1964 November 20, was preceded by a swarm of earthquakes, which started on November 10. Within four hours of the start of the swarm, the frequency of shocks recorded on the island's seismograph had risen to a maximum of over 80 an hour. Volcanic tremor soon appeared, and became continuous by November 12, masking all but the largest earthquakes. Thereafter, both the level of tremor and the frequency of earthquakes declined until by the time of the eruption only 10–15 shocks an hour were being recorded. Following the eruption, the island was evacuated for two weeks. For four days after the reoccupation on December 6, three additional seismographs were installed and during this time the earthquakes occurred to the west and south-west of the crater, at distances of 4–8 km from it, and at depths of up to 8 km.

ISSN:0028-8306    

DOI:10.1080/00288306.1967.10423220

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A high content of radioactivity in sediments, when sea water is the source of the radioactive elements, depends on the slow rate of sedimentary deposition. The radioactive content of the Niuean soils is comparable with that found in deep-sea sediments, but the rate of sedimentation in deep-sea areas is unlikely to have been as rapid as in the now dry lagoon at Niue. Hence a sea-water origin for the abnormally high radioactivity at Niue is unlikely.

ISSN:0028-8306    

DOI:10.1080/00288306.1967.10423221

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Manganese nodules from the Campbell Plateau and Macquarie Ridge have been chemically analysed and their compositions compared with other Pacific nodules. No significant differences in composition are apparent. Foraminifera from nodule nucleii are late Tertiary or Quaternary, indicating the late geological formation of manganese nodules in this region. Nodule formation may be related to late Tertiary or Quaternary submarine volcanism.

ISSN:0028-8306    

DOI:10.1080/00288306.1967.10423222

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Palmerston, Aitutaki, Manuae, Atiu, Takutea, Mitiaro and Mauke, and Eclipse Seamount, within the Southern Cook Island Group, form a linear volcanic chain with WNW trend. Rarotonga and Mangaia belong to a separate linear system composed dominantly of seamounts. Concave slopes around the islands are geologically complex, consisting of the original volcanic slopes, reef talus deposits, and fans of slumped debris. Around the base of each volcano are archipelagic aprons, probably of sedimentary origin. Parasitic cones and laccolith intrusions occur along fractures ringing the bases of the volcanoes. Crustal warping due to subsidence of the Aitutaki-Mauke group of volcanoes has resulted in formation of “moat and arch” structures. The fissured crest of the arch surrounding the group is diversified by clusters of small volcanoes and the larger cones of Rarotonga and Mangaia.

ISSN:0028-8306    

DOI:10.1080/00288306.1967.10423223

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Lavas and dikes in Rarotonga were sampled at 12 sites and are all found to be of reversed polarity. The mean directions of remanence are found to be 223°, + 59°, for samples from the Avatiu Valley and 180°, + 48°, for samples from the Tuoro quarry; the average circular standard deviations are 47° and 20° respectively. Insufficient sampling prevents interpretation in terms of secular variation.

ISSN:0028-8306    

DOI:10.1080/00288306.1967.10423224

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

An interpretation is given of a total force aeromagnetic survey of an oceanic area limited by lat. 22° N and lat. 25° N and by long. 162° Wand long. 167° 30′ W. The bathymetry is described and is used to infer the geological history. Magnetic anomalies trend east over the Hawaiian Ridge and trend north-east over the surrounding sea floor. The larger anomalies are caused by normal, or more rarely by reverse, magnetisation of the bathymetric features, the smaller anomalies by magnetically anomalous bodies in the earth's crust. Anomalous bodies in the Hawaiian Ridge are probably serpentinised ultrabasic rocks that lie beneath the volcanic vents, and those away from the Hawaiian Ridge are probably north-east trending intrusions.

ISSN:0028-8306    

DOI:10.1080/00288306.1967.10423225

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The Tongan Islands lie along the north-east trending Tunga Ridge that separates the Tonga Trench in the east from the Lau Basin to the west. They consist of active andesitic volcanoes along the north-west margin, whereas in the east they consist of older tuffaceous sediments together with rhyolites of Eocene age, and also limestones of Eocene to Quaternary age. Tilted terraces extend up to 750 ft above sea level. Geophysical evidence and metamorphic minerals within the pyroclastics suggests that the Tonga Ridge consists of a continental type crust.

ISSN:0028-8306    

DOI:10.1080/00288306.1967.10423226

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor