摘要:

The Cainozoic volcanic rocks of eastern Victoria comprise most of the Older Volcanic Series. K‐Ar ages of volcanic rocks in South Gippsland range from middle Palaeocene to middle Eocene; the older ages are to the east. In the Eastern Highlands the majority of lavas are of late Eocene to middle Oligocene age, with some lavas of late Oligocene to Pliocene age. The Cainozoic volcanic activity in Victoria is thought to have been almost continuous since it started in the early Palaeocene, with peaks of activity from Palaeocene to Eocene and from Pliocene to Pleistocene.

ISSN:0016-7614    

DOI:10.1080/00167617408728858

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Eclogite of high‐pressure low‐temperature origin occurs within the Great Serpentine belt of New South Wales. The presence of glaucophane‐bearing rocks and other medium to high‐pressure assemblages associated with the belt is similar in many respects to the Californian and Oregon occurrences. The chemical composition of the eclogite is characterized by low K2O values comparable to many oceanic tholeiites, although one analysis is nepheline‐normative. Ti‐Zr‐Y ratios also show affinities to ocean‐floor basalts.

ISSN:0016-7614    

DOI:10.1080/00167617408728859

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Stratigraphic, geomorphological, and radiometric evidence shows that the laterite of the high plains and plateau of Kangaroo Island is older than the Middle Jurassic but younger than the Early Permian. Palaeoclimatic and palaeontological considerations suggest the Triassic as the most likely age of both the laterite and the surface on which it is developed. High‐level lateritized surfaces in the adjacent Mount Lofty Ranges and southern Eyre Peninsula are of similar age.

ISSN:0016-7614    

DOI:10.1080/00167617408728860

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Fine‐grained and coarsely oolitic kaolinite clayrocks that closely resemble in composition, texture, and structure those of the Garie Formation in the southern part of the Sydney Basin are described from the Western Blue Mountains of New South Wales. The kaolinite clayrocks form part of a fine‐grained unit, here designated the Docker Head Claystone Member. It is concluded that the kaolinite clayrocks are the equivalent of the Garie Formation and represent fluviatile accumulations of detritus derived from the same highly weathered source rocks that gave rise to the Garie Formation.

ISSN:0016-7614    

DOI:10.1080/00167617408728861

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The Table Hill Volcanics of the Officer Basin were first dated as approximately 1100 m.y. from Rb‐Sr model ages for total‐rock samples of basalt from the Yowalga No. 2 bore. Later regional mapping, however, places the Volcanics as Marinoan (very late Precambrian) or younger, and receives support from discordant K‐Ar ages ranging from 330 m.y. to 445 m.y. New total‐rock analyses confirm the original Rb‐Sr data, but analyses of separated minerals do not confirm the low value for the initial87Sr/86Sr that had been assumed to calculate the 1100 m.y. model age. Instead, apparently‐unaltered primary pyroxenes indicate that the initial87Sr/86Sr could be as high as 0.718. Combined with the total‐rock results, this yields an apparent age for the basalt of 575 ± 40 m.y. It is possible in principle that the high87Sr/86Sr in the pyroxenes could be due to Sr isotope exchange during a Palaeozoic metamorphism, but there is absolutely no field or petrological evidence for such an event. Consequently, and in view of the stratigraphic evidence for their age, the Rb‐Sr data are best interpreted as signifying an original extrusion of the basalts at 575±40 m.y., together with a prehistory of the magma that includes contamination with radiogenic Sr and alkalis from Precambrian crustal material.

ISSN:0016-7614    

DOI:10.1080/00167617408728862

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Three age groups of structures are recognized regionally; the oldest of these can be subdivided into at least two age groups within the NBHC Mine. The oldest structures, which are defined as those which occur in rocks affected by the highest grade regional metamorphism, formed before the final high‐grade equilibration of the rocks. In the last phase of the oldest deformation, and in the second deformation, which was accompanied by amphibolite‐facies retrograde metamorphism, shear‐zone‐like structures formed, whose orientation and character indicate that the rocks were compressed horizontally and extended vertically. Foliation within the ‘shear zones’ is inclined to the attitude of the zone containing it; so folds within ‘shear zones’ are en‐echelon and do not plunge parallel to large folds formed on the boundaries of zones. Most of the lode and associated rocks must have existed as mechanically distinctive units at the time of the youngest phase of the oldest period of deformation, since the style of folds formed in this deformation are related to present differences in the lithology of the folded rock units. However, stratigraphic relations indicate that some of the rocks with a low Pb‐Zn content and at least some garnet quartzite formed by metasomatism which accompanied the regional metamorphism, i.e. by metasomatic interaction between adjacent rocks during metamorphism.

ISSN:0016-7614    

DOI:10.1080/00167617408728863

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Palaeomagnetic results from 40 dykes sampled on Eyre Peninsula and Yorke Peninsula, South Australia, are inconsistent with the clockwise rotation of the ‘foot’ of Yorke Peninsula by fault‐drag during the Early Ordovician. A reinterpretation of earlier data from Tasmania also indicates that the east‐west structural trends in the Mount Reed volcanic arc and Dundas Trough are primary. The effects of shearing were probably restricted to linear displacements without causing rotation of adjacent structural elements. Late Precambrian and Cambrian palaeomagnetic data from Fleurieu Peninsula and Kangaroo Island have also been analysed. They do not clarify the pattern of structural evolution in the southern part of the Adelaide Orogen because the magnetic remanence was probably acquired syntectonically.

ISSN:0016-7614    

DOI:10.1080/00167617408728864

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The results of the seismic surveys recorded during 1963 and 1968 for Marathon Petroleum and Crusader Oil in the Laura Basin, north Queensland, have been reinterpreted. Seismic reflections which dip almost continuously from 0.6 to 4.0 seconds reflection time may come from the base of and within an 8000 m sequence of Permo‐Carboniferous sediments, which may underlie the flat‐lying Mesozoic Laura Basin sediments and overlie the heavily folded Carboniferous‐Devonian sediments in the Hodgkinson Basin. Further seismic investigation of this area is recommended since a thick Permo‐Carboniferous sedimentary section here could be prospective for hydrocarbons.

ISSN:0016-7614    

DOI:10.1080/00167617408728865

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The recordings made during 1972 from large explosions at Kunanalling (W.A.), Mount Fitton (S.A.). and Bass Strait have added considerably to seismic refraction data measured over distances of 1000 km in continental Australia. Taken together with data from the 1956 Maralinga atomic bomb and 1970–71 Ord Dam explosions they show the existence of a refractor with apparent P‐wave velocity in the range 8.26–8.29 km/s, which is interpreted as the Moho under shield regions, at a depth of 34 km under Kalgoorlie and deepening eastward to 39 km under Maralinga. In northern South Australia and farther north and east this refractor is evident as a sub‐Moho refractor at a depth of about 60 km; the Moho refractor is also evident, with an apparent P velocity of 8.04 ± 0.04 km/s at a depth of 40 km. Two computer models (TASS‐1a and 2a) match the observed data. The subsequent arrivals recorded are consistent with the velocity of 8.53 km/s in a refractor at 165 km depth interpreted from the Ord Dam; there is little conclusive evidence for a low‐velocity zone above this depth.

ISSN:0016-7614    

DOI:10.1080/00167617408728866

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

During a marine geophysical survey of the Bismarck Sea by the Australian Bureau of Mineral Resources in 1970, magnetic, gravity, and seismic reflection recordings were made along north‐south traverses with a spacing of 30 to 40 km. The magnetic data have been interpreted, first by visual inspection of magnetic and topographic trends and then by two‐dimensional computer modelling along typical profiles. The interpretation indicates that the Bismarck Sea is divided into two main tectonic provinces separated by a boundary which roughly coincides with a line joining Manus Island and the Willaumez Peninsula of New Britain. An area of apparently nonmagnetic basement about 10 km wide coincides with a well defined band of shallow earthquakes which runs east‐west across the centre of the Sea. A major boundary is present at the eastern end of the Sea along the west coast of the Gazelle Peninsula of New Britain; it continues along an offset in the band of earthquakes to New Hanover.

ISSN:0016-7614    

DOI:10.1080/00167617408728867

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor