摘要:

The spatial distribution of earthquakes is described for the Papua New Guinea and Solomon Islands region, using data for the period 1931 to 1970. Most of the seismic activity is concentrated in a belt which follows through northern New Guinea, New Britain, Bougainville, and the Solomon Islands. Within this belt, the activity is highest from the Huon Peninsula to the southern end of Bougainville. Here, there is evidence that the earthquake foci lie in zones which dip away from the Solomon Sea, with a series of deep earthquakes occurring on the northern side of the main seismic axis. This section also marks the region of greatest apparent energy and strain release. In northern New Guinea the activity generally increases from west to east, as do the focal depths of the deepest earthquakes. Although the pattern is not clear, the earthquakes appear to lie within a zone which dips towards the northeast, although, in parts, there is also evidence that some reside in another zone which dips less steeply towards the west-southwest. Several minor belts of activity flank the major earthquake zone, the earthquakes within them being predominantly shallow in focal depth.

ISSN:0016-7614    

DOI:10.1080/14400957308527891

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

The focal mechanism solutions for a number of earthquakes in the New Guinea region are presented. These solutions, together with the results of a previously reported spatial seismicity study, are used to deduce the tectonic nature of the region in terms of plate tectonics, using the geological features of the region as constraints. The region is basically a zone of interaction of the Australian and South Pacific plates. Within this zone are several minor sub-plates referred to as the Solomon Sea, New Britain, and Manus plates. A consistent system of relative velocity vectors has been deduced for these plates. A zone of subduction is apparent under New Britain and the Solomon Islands, a zone of sinistral transcurrent movement operates between the New Britain and Manus plates, sea-floor spreading seems certain in the Woodlark Basin region, and a continent/island arc collision zone exists in northern New Guinea. An interpretation of the Cainozoic history of the New Guinea region is presented.

ISSN:0016-7614    

DOI:10.1080/14400957308527892

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

Seismic interpretations along lines of shots and stations in the New Britain/New Ireland region have revealed structural detail in this tectonically complex region. When correlated with marine and land gravity measurements, they indicate a comparatively uniform crust 18 km thick in the eastern Bismarck Sea, thickening to between 30 and 40 km approximately under New Britain and New Ireland. The interpretations indicate crustal thinning of the order of 8 km under the gravity high of central New Britain, and it is suggested that this is upwarping due to northsouth compressional forces. The gravity data indicate that a similar structure could apply to other islands in the Solomon chain. Shear forces seem to dominate the geological structure in the region of the Gazelle Peninsula and southern New Ireland, and the 30 km thick crust there contrasts sharply with an 18 km Bismarck Sea crust along the west coast of the Peninsula. The crustal thickness under New Ireland is the same as that under the islands to the east. The seismicity of the region indicates a multiple junction of crustal plates in the Rabaul area, and the structural characteristics are predominantly a result of a lithospheric subduction zone under New Britain and a multiple shear zone extending across the Bismarck Sea.

ISSN:0016-7614    

DOI:10.1080/14400957308527893

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

A study of the stratigraphic units within the southern Sydney Basin has led to the recognition of Upper Carboniferous and Lower Permian sediments. Terrestrial valley-fill sediments up to 228 m thick define a palaeodrainage system active during the Upper Carboniferous. These sediments belong to the proposed Talaterang Group and comprise the Yadboro Conglomerate, Tallong Conglomerate, Burrawang Conglomerate, Yagers Conglomerate, Pigeon House Creek Siltstone, and Badgerys Breccia. Palynological data indicate that at least the lower part of the Talaterang Group can be correlated with the Seaham Formation of the Hunter Valley.

ISSN:0016-7614    

DOI:10.1080/14400957308527894

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

Strontium isotope analyses have been carried out on four fresh samples from the Strangways Range carbonatite. The results indicate values of87Sr/86Sr which, when corrected to give emplacement values assumed to be 2000 m.y. ago, strongly support the suggestion that these rocks are true carbonatites. The87Sr/86Sr values are all less than 0.7040 (initial ratio at 2000 m.y. ago) and the present day ratios range between 0.7089 (plagioclase-rich sample) and 0.7036.

ISSN:0016-7614    

DOI:10.1080/14400957308527895

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

An assumed glacial pavement at the base of a Late Proterozoic glacigene sequence in the Wooltana district is explained as a tectonic feature. Similar surfaces, not associated with glacigene sediments, occur in the same district.

ISSN:0016-7614    

DOI:10.1080/14400957308527896

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

A halysitid coral specimen, doubtfully referred toQuepora, was found in a forsterite-phlogopite marble from near Walang, east of Bathurst. The rocks are probably of hornblende hornfels facies. Some recent reports of fossils in metamorphic rocks are noted.

ISSN:0016-7614    

DOI:10.1080/14400957308527897

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

K/Ar age determinations (23.6-21.8 m.y.) date the Great Lake basalts as latest Oligocene/earliest Miocene, a significantly older age than was previously assigned to them on physiographic grounds. Slight differences in the ages are consistent with the established field succession. Palaeomagnetic data determined on some of the dated rocks are consistent with such ages.

ISSN:0016-7614    

DOI:10.1080/14400957308527898

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

The Allandale quartz tube strainmeter, sited near Melbourne, Victoria, is now operational. The situation and construction of the installation are discussed and initial long-period data are presented. From the Fourier amplitude spectrum of the data the principal earth tide components are identified. It is thought that thermoelastic and barometric effects are the major contributors to the noise in the signal and work is now proceeding on methods of eliminating these effects.

ISSN:0016-7614    

DOI:10.1080/14400957308527899

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

A possible new astrobleme has been found 5 km northwest of Kelly West trigonometrical station, which is about 40 km south-southwest of Tennant Creek, N.T. It consists of an approximately circular outcrop of sandstone of the Lower Proterozoic Hatches Creek Group about 2 km in diameter. Shatter cones, found over most of the outcrop, provide the main evidence for the postulation of an astrobleme. The sandstone is very fractured and jointed in parts of the structure. Cambrian sediments that are not shatter-coned infill the structure, thereby dating the impact event as some time between the Lower Proterozoic and the Early Cambrian.

ISSN:0016-7614    

DOI:10.1080/14400957308527900

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor