摘要:

The regional schistosity at Broken Hill, previously regarded as a single fabric element, has been separated into three overprinting elements—one of high meta‐morphic grade (S1), one of variable grade (S2), and one consistently retrograde (S3). S1and S2make up by far the majority of occurrences mapped to date. A new descriptive terminology is introduced to take account of this complexity. Extensive metamorphic crystallization has taken place during the first two periods of schistosity formation (F1, F2), and the distribution of metamorphic assemblages is thus partly controlled by the extent to which F1assemblages have been modified by F2, and the variable grade of F2. A regional retrograde schistosity can locally be shown to be S2, although it is sometimes superposed on F2structures and is then classified as S3.

ISSN:0016-7614    

DOI:10.1080/00167617508728896

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Bedding characteristics of the fluvial Hawkesbury Sandstone (Triassic) of the Sydney Basin are most readily explained in terms of a model of flood‐ and falling‐stage vertical accretion derived from Coleman's study of the Brahmaputra. This model suggests inadequacies in present concepts of ‘braided stream’ deposits based on observations made at low stage. A Brahmaputra model may be widely applicable to continental sheet sandstones.

ISSN:0016-7614    

DOI:10.1080/00167617508728897

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

K‐Ar and Rb‐Sr isotopic measurements have been made on the north‐south belt of igneous and metamorphic rocks from the Peninsula Ridge and Yambo Inlier of Cape York Peninsula. Four periods of Palaeozoic igneous activity appear to have been denned. These are (87’Rbλ= 1.39 X 10–11y–1) about 415 m.y., about 400 m.y., 385–390 m.y., and 255–280 m.y., with the youngest dates to the north and northeast. The largest volume of magma, the Kintore Adamellite was emplaced during the 285–390 m.y. period. Initial87Sr/86Sr ratios range from 0.715 (a granodiorite) through 0.72–0.74 (muscovite adamellite) to 0.76 (leuco‐adamellite), which suggests a high component of old crustal material in the latter types.

ISSN:0016-7614    

DOI:10.1080/00167617508728898

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

In contrast to recent interpretations it is here argued that the 2400+ m Lower‐Middle Devonian Tamworth Group accumulated primarily in a slowly subsiding, open marine sublittoral (shelf) environment, near the western margin of the New England Geosyncline.

ISSN:0016-7614    

DOI:10.1080/00167617508728899

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The ply structure of the Bulli seam in the Southern Coalfield of the Sydney Basin persists over the main part of the coalfield. Lateral variations were investigated using both petrographic profiles and swelling index profile sections. The results indicated that the thickness pattern of the whole Bulli seam was affected by three independent factors: (1) post‐depositional loss of the top portion of the seam; (2) pre‐depositional topography; and (3) differential subsidence during deposition. The lack of definite correlation between seam thickness and present geological structure suggests that no local tectonic movement took place during deposition of the seam. Tectonic movement cannot, therefore, be the main cause of variation in seam thickness. Subsidence during deposition of the Bulli seam in the northeastern margin of the coalfield appears to have been too rapid, and near the western margin too slow, to form a thick coal seam. However, in the main part of the coalfield, the rate of subsidence was suitable for peat accumulation and a thick seam was deposited under stable conditions, as indicated by the persistent ply structure.

ISSN:0016-7614    

DOI:10.1080/00167617508728900

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Continuous seismic profiles have been obtained over 3000 km of traverse across the continental shelf and upper slope of southeast Australia between Sugarloaf Point and Gabo Island. Acoustic basement consists of Lower Palaeozoic or Permo‐Triassic rocks underlying relatively unconsolidated sediments of Tertiary to Holocene age. The profiles show the basement surface sloping eastwards from the coast to the middle or inner part of the shelf where there is either a ridge (offshore Sydney Basin) or a step (offshore from the Lachlan fold belt). This basement ridge or step separates thin or non‐existent sedimentary cover to the west from a sequence to the east thickening seawards. Much larger basement ridges cross the shelf in the Sugar‐loaf Point and Shoalhaven areas. The former strikes southeast, the latter southwest. Major basement depressions occur southeast of Newcastle and off Disaster Bay.

ISSN:0016-7614    

DOI:10.1080/00167617508728901

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The Murray Basin is geologically featureless, has been sparsely covered by geophysics, and is penetrated by a few scattered wells. Only drilling and reflection seismic work have provided consistently reliable depth information. They have indicated the presence of narrow troughs, which contain more than 3 km of Palaeozoic sediment, covered by basement highs with less than 300 m of Mesozoic and Cainozoic cover.

ISSN:0016-7614    

DOI:10.1080/00167617508728902

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Sub‐basaltic silcretes are widespread in the Monaro, New South Wales, and their origin has been hitherto linked with eruption of the overlying basalt. Investigation of silcretes from three localities in the Monaro at granite‐basalt, shale‐basalt, and basalt‐basalt contacts, has revealed a complex history of depositional events in these rocks, which cannot be related to a single event such as eruption of the overlying basalt lava flow. Major and trace element abundances suggest that the silcretes are formed from quartz sand with little admixture of feldspar and/or clays and that the overlying basalt has contributed nothing to their chemical composition. The evidence is consistent with low‐temperature precipitation of quartz. The significance of the silcrete‐basalt association is considered to be that the basalt acts as a cap rock, providing a confined aquifer within the sand deposit and a favourable environment for SiO2deposition.

ISSN:0016-7614    

DOI:10.1080/00167617508728903

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

ISSN:0016-7614    

DOI:10.1080/00167617508728895

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor