摘要:

A Rb‐Sr analysis of granitic rocks in the Corryong District reveals that the regional aureole granites of that area (Corryong Batholith) are 430 ± 8 m.y. old. This age is some 15 m.y. older than the regional aureole Cooma Granite and if both granites are the ultimate products of the metamorphism, then the locus of this metamorphism progressed eastwards. Unlike other continents (e.g.S. America) the migratory nature of this trend of metamorphism and granite emplacement is not readily explainable in terms of possible Palaeozoic plate‐tectonic mechanisms.

ISSN:0016-7614    

DOI:10.1080/00167617208728787

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

A review is presented of all solutions for the geoid in the Australian region, culminating in the 1971 determination, based on a combination of astro‐geodetic and gravimetric techniques. It is shown how the principles underlying this combined solution can be used to establish a World Geodetic System which would provide an alternate method for studying the secular variations in position, of points at the surface of the Earth.

ISSN:0016-7614    

DOI:10.1080/00167617208728788

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

Detailed petrographic and chemical studies of silcretes collected from Beda Valley near the southern extremity of Lake Torrens, South Australia, have shown that there are at least two distinct types. One type, often found attached to quartzite, has very angular grains of quartz in a matrix very high in titanium. Electron probe studies clearly show that the areas between the quartz grains are mostly titania containing very little silica. These skins, besides containing 2–10% Ti, contain .05 to .25% Zr with a very high correlation between ratio of the amount of these elements in the skin to that in the quartzite and it is suggested they have been produced by the loss of silica. The other type of silcrete has subrounded grains of quartz in a matrix of chalcedonic silica. It is also low in titanium (<1%) and low in zirconium (<.04%). It is suggested this type, which in this area is massive with columnar structure, is formed by the addition of silica.

ISSN:0016-7614    

DOI:10.1080/00167617208728789

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

The first comprehensive focal mechanism study of South Australian earthquakes has yielded information on the tectonic stresses operating within the upper crust. A model has been derived for tectonism in the Flinders‐Mt Lofty Ranges which appears to explain some of the major geological features and observed patterns of seismicity. Results support the hypothesis that Australia consists of at least two large quasi‐stable plates, with relative dextral strike‐slip motion in the region of the Adelaide Geosyncline and gulf graben system, which appear to be associated with the plate boundaries. On the basis of present tectonism, an attempt has been made to interpret the past in terms of plate tectonics.

ISSN:0016-7614    

DOI:10.1080/00167617208728790

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

The structural relationships between the Soldiers Cap Formation and the unconformably overlying and brecciated Corella Formation along a part of the eastern flank of the Cloncurry‐Mount Isa Proterozoic terrain are considered. Isoclinal to open folding of the Soldiers Cap Formation was accompanied by regional metamorphism, the grade ranging from lower greenschist facies in the synclines to amphibolite facies (up to the sillimanite isograd) in the anticlines. Subsequent emergence and denudation are represented by a major unconformity, on which carbonate sediments of the Corella Formation and sandstones of the Roxmere Quartzite were deposited. This was followed by strong flexuring of the Soldiers Cap Formation on steeply plunging cross‐fold axes, whereby the axes of the earlier isoclinal folds were rotated laterally in an anticlockwise sense at angles of up to 220° Because of the lack of a decollement horizon at the base of the carbonates, these rocks reacted to stresses induced during the cross‐folding movements by severe brecciation and block movements on a large scale. Both the cross‐folding and the brecciation are confined mainly to a broad aureole bordering the Naraku granitic batholith, the emplacement of which is considered to have caused the cross‐folding.

ISSN:0016-7614    

DOI:10.1080/00167617208728791

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

An analysis of variance of the available heavy mineral data from the Triassic Hawkesbury Sandstone and Narrabeen Group of the Sydney Basin shows that there is a highly significant (P < .01) difference between the two units in the average proportion of zircon and rutile where the proportion of each heavy mineral is expressed as zircon + rutile + tourmaline = 100. The analysis for the proportion of each mineral type is based on 94 samples. In addition a highly significant difference (P < .01) was observed between thetwoformations for size of zircon and rutile grains where grain size was recorded on 78 zircon samples, 44 rutile samples and 76 tourmaline samples. No differences could be detected for tourmaline. No other detrital heavy minerals were present in other than one or two samples and thus were of no use in differentiating the two units. The rutile in the Hawkesbury Sandstone is red and light honey brown while that in the Narrabeen Group is more commonly dark brown to almost opaque. The difference in frequency, size and morphology of these heavy minerals cannot be explained by winnowing in differing hydrologic regimes but rather by differences in provenance. The Narrabeen Group sediments represent a fluvial‐deltaic complex derived mainly from the northern New England and the western Lachlan geosynclinal rocks while the Hawkesbury Sandstone represents a tidal‐delta‐estuarine sand complex that may have been derived from a source in southern New South Wales and northeastern Victoria, and possibly also southeast from New Zealand when these islands broke awav from eastern Australia.

ISSN:0016-7614    

DOI:10.1080/00167617208728792

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

ISSN:0016-7614    

DOI:10.1080/00167617208728793

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

ISSN:0016-7614    

DOI:10.1080/00167617208728794

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

The principal Lower Devonian depositional belts of the Lachlan Geosyncline were a western, predominantly non‐volcanic belt, including the Cobar Basin and the Melbourne Trough with its southerly extension into Tasmania, and an eastern, volcanic belt, including the Parkes Platform, Cowra Trough, Molong Rise, Hill End Trough and Capertee Rise. These were separated by a more or less continuous median stabilized block comprising the Girilambone Arch, Wagga Arch and Snowy Mountains Block, which acted as a mildly positive structure during Early Devonian time. The sea regressed from the Cobar Basin and Melbourne Trough in about late Emsian times. Succeeding Devonian deposits in the western belt were entirely of non‐marine type. The Middle Devonian Tabberabberan Orogeny was responsible for the virtual stabilization of the entire geosynclinal tract, for the main uplift, folding and faulting of the Hill End Trough and adjacent rises, and folding in the Melbourne Trough. Non‐marine basin and platform deposits predominated in the Upper Devonian. A short‐lived marine transgression extended on to the eastern flank of the Snowy Mountains Block and across part of the former eastern volcanic belt in Frasnian times. In Central Victoria acid volcanic activity in the Late Devonian was associated with cauldron subsidences.

ISSN:0016-7614    

DOI:10.1080/00167617208728795

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

Devonian rocks occur in northeastern Australia within the ‘Tasman Geosyncline’ in three major tectonic divisions—(a) a very broad mobile platform related to the last stages of stabilisation of the Lachlan Geosyncline, marginal to which is found, (b) the volcanic‐rich New England Geosyncline, and (c) a contrasting region in northern Queensland where complex marine to continental sedimentation occurred on cratonic blocks while non‐volcanic flysch‐like sedimentation occurred in the marginal Hodgkinson Basin.

ISSN:0016-7614    

DOI:10.1080/00167617208728796

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor