摘要:

The Mullions Range Volcanics in the Mullion Creek‐Kerrs Creek area consist of Middle to Late Silurian rhyolite and dacite lavas‐and intraformational clastic rocks, lying on the eastern flank of the Molong Rise. They are the products of a shallow water (maximum depth c.500 m) volcanic pile that separated the broad Narragal Lagoon on the Molong Rise from the Hill End Trough to the E. Facies and thickness changes within the Mullions Range Volcanics suggest a major volcanic centre to the S or SE of the area studied, where the pile may have become emergent. Facies changes in the overlying Bay and Cunningham Formations support the existence of a volcanic pile, which had a topographic influence on subsequent deposition. The Mullions Range Volcanics probably represent the silicic phase of volcanism associated with the initiation of rifting to form the Hill End Trough.

ISSN:0016-7614    

DOI:10.1080/00167618108729164

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The Coffs Harbour Association, New England Orogen, consists of thick, monotonous units of Late Palaeozoic greywacke, laminated siltstone and mudstone, and massive argillite. The rocks of the association have a common provenance, being derived predominantly from a volcanic arc source consisting of mainly dacite, with minor andesite and rhyolite. The Coramba beds in the Coffs Harbour Block are divided into four petrofacies based on QFL data and the occurrence of detrital hornblende. Upwards, the petrofacies are: A—volcanolithic, B—feldspathic, C—horn‐blende‐feldspathic, D—hornblende‐volcanolithic. The petrofacies and vertical variation in non‐volcanic detritus indicate minor erosion and exposure of a non‐volcanic source, followed first by recommencement of volcanism, penecontemporaneously with sedimentation, then further erosion of the non‐volcanic source area. There was little temporal change in the character of volcanic detritus shed from the source area. Equivalents of the four petrofacies are recognised in other blocks of the association, although because of structural complexity, a complete A‐D sequence has not been found. The Coffs Harbour sandstones are similar to sands in modern ocean basins derived from an arc system of either continental margin or island arc type. The sandstones are not similar to recycled orogenic provenances, such as found in accretionary prisms or trench‐slope basins; the compositions suggest that the sandstones were deposited in either a forearc or backarc setting.

ISSN:0016-7614    

DOI:10.1080/00167618108729165

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The Lower to ?Middle Devonian Kowmung Volcaniclastics form the upper part of a succession of Upper Siluran to mid‐Devonian flyschoid rocks in the Yerranderie area of N.S.W., and contain two major facies associations. (1) A mudstone facies association represents the ambient, background sedimentation, comprising predominantly buff mudstone that is host to an assemblage of coarser‐grained sediments, including graded‐bedded to massive siltstone, sandstone, conglomerate, allodapic limestone, and large allochthonous limestone blocks and associated limestone breccia. Bouma sequences are common, sole structures occur and maximum bed thickness is about 3 m. (2) A volcaniclastic facies association intrudes and interrupts the accumulation of the ambient mudstone facies association, and contains massive to partly graded, quartzofeldspathic siltstone, sandstone, breccia and conglomerate. Sedimentation units in the volcaniclastic facies association are up to 120 m thick. The two facies associations interfinger. Stratigraphically, the base of the Kowmung Volcaniclastics is taken as the first sedimentation unit of the volcaniclastic facies association. The mudstone facies association below this level is part of the Siluro‐Devonian Taralga Group.

ISSN:0016-7614    

DOI:10.1080/00167618108729166

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

ISSN:0016-7614    

DOI:10.1080/00167618108729167

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The 162 m high Talbingo dam was the last of a number of dams to be completed as part of the extensive Snowy Mountains Hydro‐electric scheme in southeastern New South Wales. During a thirteen year monitoring period prior to the filling of the reservoir in May 1971, no seismic activity had been detected in the immediate area. Three weeks after impounding commenced, the first of a long series of events was recorded. The earthquake activity was not distinguished by one main shock, but rather by several sequences, all of which included events up to magnitude 3.5. The first activity occurred in the region of the reservoir, but over a period of three years, the events migrated to a region about 5 km downstream of the damsite. Subsequent activity, whch has been sporadic to the present day, has encompassed both regions. Fault‐plane solutions indicate normal dip‐slip faulting along the line of the reservoir, and indicate that the activity could have been triggered either by the reservoir load or by an increase in pore pressure.

ISSN:0016-7614    

DOI:10.1080/00167618108729168

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

In the fracture pattern of the Sydney Basin, various fracture and stress domains that are spatially related can be recognised. At least for the western region of the Basin, periodic, relatively narrow domains (termed fault and joint swarms) that have a submeridional trend are believed to be similar to the Lapstone Monocline‐Kurrajong Fault structures, and may extend into the Lower Palaeozoic basement. An overall, horizontal N‐S and NE‐SW oriented principal compressive stress (σ1) measured in collieries and inferred from earthquake events at depths of 10–20 km is a regional phenomenon (possibly Basin‐wide), which can be expected to be locally modified close to geological structures, especially in and close to fault and joint swarms, near major normal faults, and near minor thrust and strike‐slip faults. The interaction of colliery roadway drivage, local structures (faults and/or cleat) and the stress field permits inferences to be made about virgin stresses in coal seams. Some earthquakes coincide with fault and joint swarms, and others tend to have occurred close to or at swarm endpoints. It is concluded that the overall fracture pattern resulted from the cumulative development of fault and joint systems from mid‐Permian to Recent time. The comprehensive analysis of this pattern and its relationship to stress fields and seismic activity will require much more information.

ISSN:0016-7614    

DOI:10.1080/00167618108729169

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

First order geodetic measurements show that strain rates in southeastern New South Wales are about 50 × 10‐8y‐1. These strain rates are much greater than those suggested by seismicity. The direction of the principal axis of compression varies with position, but it is consistent with compression axis directions of the earthquake focal mechanisms in the Bowning area, and with the pattern of late Cainozoic vertical displacements suggested by geomorphology. In southwestern Western Australia strain identified from geodetic measurements is patchy in distribution, and is irregular in magnitude and direction. It is found close to areas of historic faulting, in areas of high measured stress, and across the Darling Fault line of weakness separating the Perth Basin from the Yilgarn Craton.

ISSN:0016-7614    

DOI:10.1080/00167618108729170

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Earthquakes in SE Australia are usually caused by compressive stresses acting in the crust, and are associated with steeply dipping faults. Sometimes the faulting is predominantly strike‐slip, as for the Bowning earthquakes of 1977 and some of the Dalton/Gunning earthquakes; and sometimes it is high‐angle thrust faulting, as for the 1961 Robertson and 1973 Picton earthquakes. No surface expression of the faults associated with any recent earthquakes in SE Australia has been reported.

ISSN:0016-7614    

DOI:10.1080/00167618108729171

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

An interpretation of the origins of folds and joints, which affect the Tertiary Brown Coal Measures of the Latrobe Valley, leads to the proposal that the geological structures have been formed under a regional Late Tertiary NNW‐SSE compressive stress. Considerations of the pattern of measuredin situstresses and of interpreted stresses, derived from earth movements around open cuts and from earthquakes, indicate that a regional NNW‐SSE compressive stress is still in existence in the SE part of Australia at the present time.

ISSN:0016-7614    

DOI:10.1080/00167618108729172

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Since 1976 a number of analogue and digital seismographs, which record high frequency seismic waves in the range 4 to 20 Hz, have been installed in Victoria. These enable the detection and location of microearthquakes with Richter magnitude Ml down to less than zero. Because there are many more smaller than larger earthquakes, about 250 events are now being located in Victoria each year, compared with about 25 per year between 1960 and 1975, and an average of two per year between 1840 and 1959. Despite an uneven statewide seismograph coverage, the new instruments and new lithospheric models have led to substantial improvements in earthquake location accuracy. All Victorian earthquakes with reliable depth determinations have been found to lie within the crust, most at a depth of less than 18 km. Some very small but shallow microearthquakes have been felt or heard. The isoseismal map for such an event (of magnitude Ml 1.3) which occurred at Preston during July 1976, is given.

ISSN:0016-7614    

DOI:10.1080/00167618108729173

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor