摘要:

A map of the geoid in Australia and surrounding oceanic areas has been produced on a scale of 1:5M. There are two variants, both of which employ Bouguer anomalies for the land areas. For the ocean areas in the first variant, anomalies have been obtained as the difference between the observed and theoretical values of gravity at sea level. In the second variant, a correction has been introduced to reduce the density of the water layer to the average density of the Earth's crust. The height of the geoid in Australia is calculated in the same way. The effect of distant zones has been allowed for in accordance with the data of Kozai (1967) and Köhnlein (1967), and a high precision for the geoid height for Australia has been obtained. Discrepancies between the new data and the observations of Mather (1969) amount to + 2 m for the regions investigated and ± 4 m for the entire continent. Coordinates have also been obtained for the centre of the Australian ellipsoid relative to the centre of the Earth's mass.

ISSN:0016-7614    

DOI:10.1080/00167617108728758

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

A moderately large earthquake (for South Australia) with magnitudeML =4.6 occurred in the mid‐north near Spalding on January 7, 1971 (January 6, G.M.T.). It caused minor damage and was felt up to 80 km from the epicentre. Four aftershocks were located and another four events are inferred to have been associated with this sequence.

ISSN:0016-7614    

DOI:10.1080/00167617108728759

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

A method of using the X‐ray fluorescence spectrometer has been adopted for the analyses of lead phosphates, and eight samples of phosphates from Broken Hill and three from the Flinders Ranges, South Australia, were analysed by this means. Of these, five were found to be mimetite and six pyromorphite, several being rich in calcium. Dividing the sources into geochemical areas we find that the specimens from Broken Hill have no vanadium and a low alkaline metal earth content while those from the Flinders Ranges have a small, but noticeable vanadium content and high alkaline metal earth content. A poorer X‐ray diffraction fit of a calcium‐rich mimetite to the hexagonal structure indicates that the monoclinic structure could be of more importance in the members of this composition.

ISSN:0016-7614    

DOI:10.1080/00167617108728760

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The Ordovician rocks exposed along the N.S.W. coast, near Bermagui, comprise a sequence of alternating greywacke and shale and a less abundant sequence of alternating chert and detrital beds. The only lithological boundary that can be mapped is the contact between the two sequences and it sheds little light on the large scale structure. However, due to continuity of outcrop, well‐defined vergence zones and abundant younging evidence it is possible to interpret the regional structure.

ISSN:0016-7614    

DOI:10.1080/00167617108728761

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

An intense Bouguer anomaly ‘high’ of about 30 milligals amplitude has been delineated to the east of Cootamundra, New South Wales. It is correlated with a north‐trending belt of basic metamorphic rocks of probable Upper Silurian age. The subsurface shape of the belt is deduced by qualitative and quantitative analytical techniques applied to the gravity data; it is inferred that the boundary on the western side is near‐vertical, while that on the eastern side is believed to have been overthrust by the Middle Devonian Young Granite. It appears also that there are no horizontal density variations below a depth of 6–7 km, implying that the base of the Young Granite lies at about this depth.

ISSN:0016-7614    

DOI:10.1080/00167617108728762

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Ischadites lindstroemiHinde 1884 is described from the Ordovician Daylesford Formation (lower part of the Bowan Park Group) of central western New South Wales. The species characterises a distinctive unit in the formation, occurring in bands throughout the unit. From a study of the associated lithofacies and their stratigraphic distribution in the limestones, an interpretation of the environment in which the species lived is presented. The species is considered to have inhabited a shallow‐water, lime‐mud environment, which was off‐shore and marginal to calcarenite shoals.

ISSN:0016-7614    

DOI:10.1080/00167617108728763

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The orthopyroxenes of Gosse Pile, a layered ultramafic sequence within the Giles Complex of central Australia, show unusual exsolution features such as the development of ‘hour‐glass’ shapes by clinopyroxene lamellae, and also the exsolution of spinel and rutile. Both orthopyroxene and clinopyroxene have high R2O3 contents and their distribution coefficients for Mg and Fe are high (average KD = 0.88). Some, if not all, of these features are considered to indicate that the Gosse Pile rocks crystallized under high pressure. This interpretation also explains the predominance of orthopyroxene over olivine as an early cumulus phase. Estimated conditions during crystallization are 10–14 kilobars and between 1,200‐l,400°C.

ISSN:0016-7614    

DOI:10.1080/00167617108728764

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Rubidium‐strontium and strontium isotope data for eight whole‐rock samples of granite varieties from the Encounter Bay area, South Australia, yield an isochron age of 487 ± 37 m.y. Two specimens of albitised granite, formed as a result of late‐stage metasomatic alteration of original megacrystic granite, conform to this isochron. These data support a genetic relation between granites and late‐stage metasomatic alteration as suspected from field, petrographical and geochemical studies. Eight samples from contiguous Kanmantoo Group metasedimentary rocks have an isochron age of 487 ± 60 m.y. Thus this metamorphic event is coincident with emplacement of the Encounter Bay Granite.

ISSN:0016-7614    

DOI:10.1080/00167617108728765

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Aluminous, mafic, felsic, calcareous, and sulphide‐rich rocks have been involved in localized deformation and retrograde metamorphism at Broken Hill, western New South Wales, whereretrograde schist‐zonesintersect high‐grade, regional metamorphic rocks of the lower granulite facies (or the amphibolite‐granulite facies transition). Although technically retrograde, the schists contain mineral assemblages indicative of the lower amphibolite facies. The schist‐zones were formed by local folding, apparently as part of the third stage of deformation in the Broken Hill area.

ISSN:0016-7614    

DOI:10.1080/00167617108728766

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Many fabrics in Corallian (Upper Jurassic) carbonates in England, France and Switzerland are bigenetic, forming by solution/precipitation and recrystallization processes. Early precipitated cements are non‐ferroan, whereas those formed later are decidedly ferroan. Mossbauer spectroscopy has shown that the iron in the carbonates is largely divalent, substituting for calcium in the calcite lattice. The cements may be subdivided into those forming in an oxidizing environment, and those forming in a reducing environment. Fabric evidence indicates that a solution period separates the two cement phases. The diagenetic history is linked with the sedimentation pattern. Thus, under progressive build up of sediments into shallow‐water or supratidal conditions, the first‐phase cement probably precipitated from non‐marine, partially oxygenated vadose water. Subsequent subsidence and sedimentation resulted in the depression of partially cemented sediments into zones within the sedimentary pile conducive first to pyrite precipitation, and then to ferroan calcite precipitation. Fabrics can therefore be used to interpret the diagenetic environment of regressive sedimentary associations.

ISSN:0016-7614    

DOI:10.1080/00167617108728767

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor