摘要:

The Cainozoic basalt chronology of the SE Highlands of Australia correlates with depositional cycles in the flanking basins, in particular the Murray and Gippsland Basins, and gives rise to the hypothesis that periods of more intense volcanism correspond with uplift of the Highlands and concomitant subsidence of the flanking basins. Conversely, periods of less intense volcanism correspond with settling of the Highlands and concomitant rising of the flanking basins. In terms of current extent, the SE Highlands came into existence between 60 and 50 Ma ago with the inception and rapid alluviation of the Murray Basin. Within the Cainozoic, the Highlands have undergone at least three episodes of uplift with concurrent basalt volcanism, linked with episodes of marine transgression followed by regression in the flanking basins.

ISSN:0016-7614    

DOI:10.1080/00167618208729189

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The Great Escarpment is a single escarpment that runs east of the Great Divide almost the length of eastern Australia and attains a height of several hundred metres. It separates two regions of vastly different geomorphology: the tablelands with many palaeoforms, low relief and slow process rates; and the coastal zone with few palaeoforms, moderate relief and rapid process rates.

ISSN:0016-7614    

DOI:10.1080/00167618208729190

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

F1macroscopic folds in the Late Palaeozoic Coffs Harbour Beds in the SE portion of the New England Fold Belt are commonly transected by cleavage. These macroscopic folds are tight to isoclinal structures, with a consistent vergence to the NE. Axial surfaces are either steeply dipping to the SW or vertical, and are typically faulted. Anomalous bedding‐cleavage relations occur where the steeply dipping cleavage intersects overturned limbs of F1macroscopic and some F1mesoscopic folds. Elsewhere F1mesoscopic folds have a well developed, axial‐surface cleavage and are rarely downward facing. Cleavage is commonly strike‐divergent from axial surfaces of F1macroscopic folds, except adjacent to the Demon Fault System, where they are parallel. These anomalous cleavage‐folds relations possibly developed during the one deformation. D1structures are refolded by kink‐like folds that are steeply plunging. The structural style of the D1deformation indicates that it possibly resulted from accretionary processes at a consuming plate margin.

ISSN:0016-7614    

DOI:10.1080/00167618208729191

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

New data for the Wologorong Batholith, northwest of Goulburn, New South Wales, indicate that it is S‐type and probably similar in age to the major batholith in the southern part of the Lachlan Fold Belt. Its component rocks are predominantly biotite and biotite‐muscovite adamellite, and have a strong N‐S metamorphic foliation. An isochron, defined by fourteen rocks, gives a Rb/Sr age of 405 ±11 Ma and an initial87Sr/86Sr ratio of 0.7110 ± 0.0012. Five Rb/Sr biotite ages range between 339 and 381 Ma, the older ages being obtained from the least deformed parts of the Batholith. Whereas uncertainties inherent in dating a deformed S‐type batholith make 405 Ma a reconnaissance value only, the minimum emplacement age for the Batholith, as determined from two biotites, is around 381 Ma. The younger biotite ages, around 339 to 348 Ma, are considered to date a major period of regional metamorphism in the northeastern part of the Lachlan Fold Belt, similar to that recorded from K/Ar ages of metamorphic biotite in the Hill End region 100 km to the north.

ISSN:0016-7614    

DOI:10.1080/00167618208729192

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Palaeomagnetic dates for two sites on the Southern Tablelands of New South Wales, at Bunyan and Bredbo, indicate that basal lake sediments and underlying bedrock were ferruginised during the late Tertiary. The dates provide further evidence of a regional episode of intense weathering and ferruginisation in the late Tertiary.

ISSN:0016-7614    

DOI:10.1080/00167618208729193

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Late Permian and Triassic successions of the Sydney Basin, exposed in cliffs of the north coast, south coast and Blue Mountains, include sandstones in which quartz content increases up‐sequence and palaeocurrents swing from southwesterly through southeasterly to northeasterly. These basin‐wide phenomena are interpreted to have resulted from the northeasterly migration of a drainage net, in which northeasterly‐flowing tributaries bearing quartz sand from the craton met southwesterly‐flowing tributaries bearing labile sediment from an arcuate rim‐orogen, and blended in a southeasterly‐flowing trunk stream down the axis of a foredeep. Migration of the drainage net records the retreat of an arc‐derived clastic wedge in the latter part of a megacycle which extends from the top of the mid‐Permian Nowra Sandstone to the top of the mid‐Triassic Hawkesbury Sandstone. The same megacycle occurs in the Bowen Basin, and may also occur in the Nilsen‐Mackay Basin of Antarctica.

ISSN:0016-7614    

DOI:10.1080/00167618208729194

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The Cambrian Nildottie and Erudina Siltstone Members together comprise a thick (up to 460 m) and laterally extensive (over 5000 km2) sequence of predominantly silty redbeds in the Flinders Ranges of South Australia. The occurrence of desiccation cracks, halite imprints and arthropod markings throughout the sequence indicates extensive and persistent shallow‐water marine conditions and, together with its epicontinental setting, classifies the sequence as an epeiric‐sea deposit. The virtual absence of large‐scale cross‐stratification and lack of significant facies variation in the sequence pose a major problem for detailed palaeogeographic, sedimentologic and hydraulic study. This difficulty is largely overcome by detailed analysis of ripple marks. Oscillation‐ripple data suggest that the strandline trended approximately NNE‐SSW during deposition of the Nildottie and Erudina siltstone Members, with slightly deeper water occuring in the eastern outcrops, as interpreted from the orientation of near‐symmetrical oscillation ripples. Throughout most of the area, water depth was probably only a few meters at most, with locally‐generated, low amplitude, short‐period waves being the main mechanism for sediment dispersal. A weak tidal influence is indicated by the minor presence of catenary ripples, which show a tendency to display the quadrimodal, bipolar‐dominated palaeocurrent pattern that is a feature of many tidal deposits. Current lineations are rare, and reflect a minor longshore component of transport in the slightly deeper eastern areas. Sedimentological, palaeocurrent and hdydrological parameters derived from the ripple‐mark study contribute to the understanding of the Nildottie and Erudina Siltstone Members in particular, and shallow epeiric sea deposits in general. The technique of ripple‐mark analysis used herein may be a guide to other workers in this field.

ISSN:0016-7614    

DOI:10.1080/00167618208729195

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Granite, adamellite, granodiorite, quartz monzodiorite and quartz diorite clasts, together with much more abundant basic and intermediate volcanic detritus, occur in Devonian conglomerates in the New England Fold Belt, N.S.W. The plutonic material is of calc‐alkaline type, characterised overall by high Fe/Mg ratios and low LIL abundances, and is geochemically more closely allied to plutonic rocks from island arcs than to those emplaced in continental crust. Small intrusive bodies emplaced within the volcanic chain to the west, which supplied most of the Devonian sedimentary material, are inferred to be the source of the plutonic debris. Geo‐chemical characters and palaeogeographic relationships indicate that the clasts were not derived from Late Silurian gabbro‐diorite‐granodiorite intrusions in the northern part of the Lachlan Fold Belt. The absence of accompanying metasedimentary hornfels or metamorphic basement detritus also argues against a Lachlan source and a source in a basement terrain to the west of the New England Fold Belt.

ISSN:0016-7614    

DOI:10.1080/00167618208729196

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Two major deformation phases involving low grade metamorphism affect the Ordovician turbidite sequence known as the Mallacoota Beds. First‐generation F1folds are the dominant structures, generally occurring as tight, upright, gentle SSW‐plunging folds. These folds have been followed by Do‐deformation movements that generated folds (F2), kink bands and localised zones of S2crenulation cleavage. F2folds are locally present as open and upright folds that fold the F1structures into major SSE‐plunging warps. The resulting refolded F1structures are recumbent or inclined and in places reclined. All F1folds are parasitic and lie on a steep western limb of a major anticlinal structure, in which the stratigraphic sequences young in a westward direction. F1folds are produced during a single phase of regional deformation involving layer shortening of a partly lithified sequence, whereas the Do‐deformation involved localised shearing of a consolidated sequence.

ISSN:0016-7614    

DOI:10.1080/00167618208729197

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The Mallacoota Beds of Ordovician age in eastern Victoria include: (1) a succession of greywackes, sandstones, siltstones and shales that show a variety of sedimentary structures and bedding features, including graded bedding, lateral continuity of beds, convolute lamination, slumps, flute casts, load structures and all divisions of the Bouma sequence; (2) radiolarian cherts and black shales, representing pelagic and hemipelagic deposition. These former radiolarian‐rich oozes, which occur between turbidites, have been diagenetically converted to bedded and nodular chert, whereas thick (>100 m) ribbon‐chert sequences probably accumulated in areas such as topographic highs, away from dilution by turbidite deposits. Six separate lithofacies can be defined, and bed thickness analysis indicates the presence of thinning and/or fining‐upward facies sequences and thickening and/or coarsening‐upward facies sequences, suggesting the variable proximity of channel axes with time. Palaeocurrent measurements indicate that the turbidity currents flowed in a northerly direction at the moment of deposition. The source‐rocks for the sequence are thought by the authors to be the Cambrian and Precambrian sediments of the Ross Orogen of eastern Antarctica.

ISSN:0016-7614    

DOI:10.1080/00167618208729198

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor