摘要:

Palaeogeographic reconstructions and structural analysis of the Late Carboniferous to Triassic of central eastern Australia indicate that sedimentation and deformation were responses to the prolonged application of a dextral rotational force couple to the craton margin and to eustatic sea‐level changes. The force couple distorted the craton margins and adjacent Yarrol‐New England geosyncline and orogen into an incipient coupled orocline. The influence of the couple commenced in the Late Devonian and continued with varying effect until the Late Triassic, when it reversed to a sinistral system, part of a completely different stress regime that controlled sedimentation and structure during the Early Jurassic. Within the craton, deformation mainly took the form of a series ofen echelondepressions, such as the Drummond Basin, Koburra, Denison and Taroom Troughs. A lineament between Longreach and Roma marks the southern boundary of this type of strain, although crust beyond its limit was not so rigid as to be unaffected by the force couple. The Yarrol‐New England region during the Devonian and the Early Carboniferous was the site of geosynclinal deposition where a thick and typically volcanogenic wedge lay along the eastern border of the craton. During the Late Carboniferous and Early Permian comparable wedges were formed farther to the east, in effect building outwards into the geosyncline. The same tensional regime that created the geosyncline is seen as the means for thinning crust below the sediment wedge and thus provided thermal instability, and for the igneous diapirism expressed as both intrusion and extrusion that characterizes the orogen from the Late Carboniferous onwards. The dextral force couple was responsible for most of the deformation and for controlling final emplacement of plutons. Sea‐level rises were marked in the late Early Permian and again in the early Late Permian.

ISSN:0016-7614    

DOI:10.1080/00167617908729100

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The stratigraphic succession of formations in the Myall district comprises in ascending order the Bunyah Beds, Wallanbah Formation, Kataway Mudstone, Boolambayte Formation (new names), Nerong Volcanics (E'ngel, 1962), Booti Booti Sandstone, Yagon Siltstone, Koolanock Sandstone, Muirs Creek Conglomerate (new names) and Alum Mountain Volcanics (Engel, 1962). The units range in age from possibly Devonian to possibly Permian, most being Carboniferous. The Mograni (new name), Tugrabakh (Voisey, 1940) and Mayers Flat Limestones (new name) are members of the Wallanbah Formation. The Violet Hill Volcanics (new name) is a member of the Yagon Siltstone. The Burdekins Gap Basalt Member and Lakes Road Rhyolite are members of the Alum Mountain Volcanics.

ISSN:0016-7614    

DOI:10.1080/00167617908729101

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Complex contact relations between thin sills of the Adelaidean Cooee Dolerite and the enclosing flysch sediments (Burnie Formation) indicate emplacement of the sills into substantially uncompacted quasi‐liquid sediments very shortly after deposition. The sills are consequently coeval with the sediments rather than synchronous with the first phase of folding of the sediments (the Penguin Orogeny).

ISSN:0016-7614    

DOI:10.1080/00167617908729102

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

In Tasmania sedimentary rocks containing shelly fossils at many horizons, some graptolitic horizons and numerous conodont horizons were deposited, apparently continuously, from the Tremadoc Epoch into and after the Llandovery Epoch. Superposition can be demonstrated over this interval so that the position of preserved faunas or biotas relative to one another is clear in most cases. Twenty successive Ordovician faunas are recognized. During the interval represented by this succession the geographical affinities of the faunas were generally with eastern Asian, North American and South American faunas, but in the later part of the Ordovician and in the Silurian the affinities were wider. Because of the clarity of the succession, the duration of deposition and relationships of the faunas, the Tasmanian succession is likely to be a useful link in world correlation, especially for isolated areas such as parts of South America and southeastern Asia.

ISSN:0016-7614    

DOI:10.1080/00167617908729103

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Thin (<10 m), extensive dolostones conformably capping late Precambrian glaciogenic rocks in the Kimberley region and the Adelaide Geosyncline commonly comprise micritic dolomite apparently of ‘primary’ or early diagenetic origin. Their aphanitic texture, the presence of algal and cryptalgal lamination, tepee structures and intraclastic rocks, and the lack of saline evaporites or their pseudomorphs, suggest deposition mainly in supratidal to lagoonal environments under a seasonally evaporitic/humid climate. Less common oolitic or pelletal rocks and a finely laminated shaly dolostone facies also suggest peritidal to marine influences.

ISSN:0016-7614    

DOI:10.1080/00167617908729104

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Isotopic dating of 32 whole rock samples from seven of the Papua New Guinea highlands volcanoes shows a wide spread of ages ranging from 1.6 m.y., or possibly 1.9 m.y., to around 200 000 years B.P. These dates, with evidence of recent activity on two volcanoes, suggest that the highlands volcanic province has been active for at least the last 1.6 million years and that early volcanism was contemporaneous with intrusive igneous activity in the Star Mountains. Major eruptions of lavas, however, ceased at about 200 000 years B.P. and there is evidence from some of the volcanoes of apparent long breaks in activity.

ISSN:0016-7614    

DOI:10.1080/00167617908729105

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The Mount Black Pb‐Zn deposit is a quartz‐galena‐sphalerite replacement body in the Silurian Cooleman Limestone. Fluid inclusion homogenisation temperatures range from 120° to 170°C for paragenetically early sphalerite, to 210° to 315°C for late quartz, and 245° to 320°C for calcite from contiguous recrystallised limestone. Fluid salinities increased with rising temperature, during deposition of the minerals, and the fluid composition changed from NaCl‐rich to possibly CaCl2‐NaCl (‐?MgCl2)‐rich brines.

ISSN:0016-7614    

DOI:10.1080/00167617908729106

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A unit composed of sheeted dykes and an associated unit of sodic felsic rocks have been found within the Coolac Ophiolite, about 5 km east of Coolac township, southeastern N.S.W. The dyke complex consists of small multiple dykes intruding gabbro screens. About half the dykes are basaltic in composition and half are ande‐sitic. Felsic differentiates occur as minor intrusions within the dyke complex, and also constitute the sodic felsic unit. It is suggested that the dyke complex and associated felsic rocks be included in the Honeysuckle Beds, and that the absence of a mappable dyke unit further south within the Honeysuckle Beds is caused by tectonic dismembering of the ophiolite. The dyke complex bears considerable resemblance to the sheeted dyke members of other ophiolite sequences. However, the scale of development is roughly 10 times smaller than at Troodos or Newfoundland, and one‐way chilling is not well developed. The mechanism of intrusion in the Coolac dyke complex therefore is probably not symmetrical spreading about a well defined axis, but a diffuse injection of small multiple dykes within a relatively broad extensional zone. The environment in which such a mechanism might develop, and which is suggested by geochemical evidence, including the high proportion of intermediate and felsic rocks, is that of a small basin adjacent to or within an island‐arc system.

ISSN:0016-7614    

DOI:10.1080/00167617908729107

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Rocks formerly mapped as Lower Proterozoic Argylla Formation near Mary Kathleen in northwest Queensland consist of parallel lenses of very deformed schist, quartzite and various types of metaporphyry. Completely intermingled with these are bands of amphibolite and lenses of the adjacent Wonga Granite. Finite ductile strains of 65–80% maximum shortening have been measured; these have produced transposition on both a mesoscopic and macroscopic scale. It is shown that the major stratigraphic boundaries are much shallower than the steeply dipping, constantly oriented unit boundaries. Intrusive relationships and structural criteria indicate that all the lithologies found within the mapped boundaries of the Argylla Formation are chronologically separate. This is confirmed by mapping in the much less deformed area near Winston Churchill Mine to the north. It is concluded that an original sedimentary pile was intruded first by dolerite dyke swarms and then by acid porphyry sills followed by granitic sill‐like instrusions of the Wonga Granite. Subsequent deformation and macroscopic transposition produced the present parallel‐layered structure.

ISSN:0016-7614    

DOI:10.1080/00167617908729108

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

ISSN:0016-7614    

DOI:10.1080/00167617908729109

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor