摘要:

Averages and concentration ranges for 32 elements are reported for 4 gneissic granites, 20 granodiorites and adamellites and 8 leucogranites from the Snowy Mountains, New South Wales.

ISSN:0016-7614    

DOI:10.1080/00167616608728603

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

Studies of the Murray River have revealed that its ancestral river system is the result of three separate phases of river activity, each consisting of a degradational and aggradational sub‐phase. To illustrate the relations, certain sections of the rivers were mapped in detail revealing characteristic terrace levels for the various phases. The regional pattern shows that immediately upstream from the Cadell Fault, and for a distance of 100 miles (160 km.) downstream, tectonically induced topographical changes have separated the individual ancestral rivers representative of each phase. Elsewhere, the three rivers are superimposed and follow the same general course. This pattern of separation by diversion also applies to the present rivers so that, in the diverted sector of the river system, old floodplains occur which were deserted by the present river. Initial water logging and salting problems were restricted to these deserted floodplains where they occur in the Irrigation Districts. A relative chronology of Quaternary events has been drawn up.

ISSN:0016-7614    

DOI:10.1080/00167616608728604

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

A thick superficial cover of weathered dacitic ash that mantles the flatter ridge crests on hills and mountains for up to 30 miles (48 km.) from Mount Lamington was derived from this strato‐volcano and thins with distance from it, being about 40 ft (12m.) thick 20 miles (32 km.) away. Its mineralogy is similar to that of the oldest lavas exposed in Mount Lamington crater and to the ash and pumice erupted in 1951. Size distributions of the ash show very good sorting. Inman's coefficientσø,0–8 to 1–2, and median diameters have a small range, 0.25±0.10 mm. The sorting, mineralogy, and accordance of the layers with the present topography, indicate an ash‐fall origin.

ISSN:0016-7614    

DOI:10.1080/00167616608728605

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

Isotope dilution Pb‐U ages have been measured on zircons from three areas in the Australian Precambrian. Three samples, from the Rum Jungle Complex, basement to the Pine Creek Geosyncline, yield an extrapolated age of 2,550 m.y. This result, in conjunction with published evidence concerning the age of intrusive granites, enables preliminary time‐limits, 2,550 m.y. to about 1,700 m.y., to be assigned to the period of sedimentation in this Geosyncline. Results from the Mount Isa area support geological deductions that the oldest phases of the Sybella Granite are remnants of basement rocks, approximating in age to the Ewen Granite at around 1,780 m.y.; that the Wonga Granite may well be derived from sediments older than the tectonic event reflected in the 1,300–1,450 m.y. K‐Ar ages observed in this region; and that the Wimberu Granite may belong to a later event, but older than that indicated by the biotite ages. Zircon from metasedimentary gneiss underlying the Ravens‐thorpe System in Western Australia yields an age, 2,800 m.y., equivalent to that of the intrusive pegmatite at Cattlin Creek. This suggests that the metamorphism dated at 2,800 m.y. caused complete loss of all previously‐accumulated lead from this older material.

ISSN:0016-7614    

DOI:10.1080/00167616608728606

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

Quantitative and qualitative studies of the shape characteristics of both natural and artificially prepared particles combine with evidence from diverse other sources to suggest strongly that the quartz of granitic rocks and gneisses is repeatedly fractured and healed in an intricate manner before being presented at the Earth's surface and that, in the zone of weathering, this quartz is parted along some of the resulting incipient fractures. The quartz fractures are thought to originate when granitic rocks pass through a state wherein their quartz is brittle while the surrounding feldspar is still ductile. Experimental evidence supports the view that the pattern of fractures affecting granitic quartz is characteristic of the breakage of particles of a brittle solid embedded in a ductile, deforming matrix. This process produces particles that are often remarkably equant and rounded for breakage products.

ISSN:0016-7614    

DOI:10.1080/00167616608728607

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The mountains of western and northwestern Burma consist chiefly of colossal accumulations of Palaeocene to Eocene (Arakan and Chin Hills) or Senonian to Eocene (Naga Hills) Flysch of varying, including “exotic”, facies.

ISSN:0016-7614    

DOI:10.1080/00167616608728608

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

Two approaches to the time‐stratigraphic subdivision of the Australian Pre‐cambrian are possible. In one, bodies of rock are referred, by means of radio‐metric dates, to periods defined by chosen points on the absolute time‐scale. In the second, the boundaries of time‐rock units are defined at selected reference points on the ground, and these reference points are dated as accurately as possible by radiometric means. Geographically distant bodies of rock are correlated with “type” time‐rock units by radiometric dates.

ISSN:0016-7614    

DOI:10.1080/00167616608728609

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The stratigraphical problem of defining the lower boundary of the Adelaide System is discussed in relation to the geology of several critical areas in the Adelaide Geosyncline and adjacent shelf‐platform.

ISSN:0016-7614    

DOI:10.1080/00167616608728610

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The Adelaide System forms the uppermost Precambrian sequence in South Australia and the Wooltana Volcanics lie near its base. Though affected by Palaeozoic metamorphism, the least‐altered samples give a minimum age of 850 ± 50 m.y., so that the base of the System is about 900 m.y. old or more. The unmetamorphbsed Roopena Volcanics of northeastern Eyre Peninsula are 1,345 ± 30 m.y. old and if correlated with the Wooltana Volcanics the base of the system becomes about 1,400 m.y. old. The data for the Wooltana Volcanics are consistent with this, provided that even the least‐altered total‐rock samples were open systems during the later metamorphism. Ages of basement in the Mount Painter and Olary districts (1,600 m.y.) and data for Willouran shales overlying the Wooltana Volcanics can fit both minimum and maximum estimates for the Volcanics.

ISSN:0016-7614    

DOI:10.1080/00167616608728611

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

During the Silurian Period, tectonism was fairly marked in the Chinese region, and extensive shallow‐water marine transgressions occurred, with the accompanying development of eugeosynclinal and miogeosynclinal regimes. In the Late Silurian, a Caledonian (Kwangsian) orogenic movement affected several regions of China and regression was marked.

ISSN:0016-7614    

DOI:10.1080/00167616608728612

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor