摘要:

Choiseul, 100 × 20 miles, is one of the larger islands of the British Solomon Islands Protectorate, a double chain of islands bordering the Pacific Ocean and separated from the north-east coast of Australia by the Coral Sea. It is an elongated island shaped by faulting and possesses a prominent fracture pattern. Structurally the island is a mass of fault blocks. Movement of these blocks began in early Miocene time and continues at present; reef growth and other coastal features are fault controlled. Stratigraphically the island is an autochthonous system. The geological succession is: basement amphibolite schists; a lava pile over 2,000 feet thick, made up of continental andesites, basalts and basaltic pillow lavas, with minor intrusives; a slab-like body of serpentinous ultrabasics; Lower Miocene grits and biostromal calcarenties about 300 feet thick resting on the lavas; at least 1,000 feet of subgreywackes and volcanic sandstones; Pliocene calcarenites and calcilutites of organic origin, about 2,000 feet thick; Quaternary volcanics given off by two extant volcanic cones, and slabs of uplifted limestone reef masses. Geologically, Choiseul resembles other islands in the group.

ISSN:0016-7614    

DOI:10.1080/14400956208527870

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

Present knowledge of the occurrence of characteristic echinoids in the Tertiary of Western Australia is summarised.

ISSN:0016-7614    

DOI:10.1080/14400956208527871

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

The paper presents a summary of the stratigraphy and structure of Western Tasmania and presents new information regarding these aspects in South-West Tasmania. This summary is essentially background information to the main topic which is the discussion of a regional meridional structure known as the West Coast Range Anticlinorium, and the influence of major east-west fault structures on this and other regional meridional structures of Western Tasmania.

ISSN:0016-7614    

DOI:10.1080/14400956208527872

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

Certain igneous rocks have been fractured into columnar prisms by thermal stresses produced during cooling. In some flows a threefold structural division is recognized with a lower colonnade, central entablature and upper colonnade. The entablature contains various patterns of curved columns. Joints in many flows form in a definite sequence with master joints first, mega-columns next, then normal columns and finally cross-fractures. In the simplest cases columns form perpendicularly to the isotherms but in the more complex examples, the column direction is controlled by the orientation of surfaces of equal tensile stress and these may not be parallel to the isotherms.

ISSN:0016-7614    

DOI:10.1080/14400956208527873

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

In this reef area lithification has resulted in the formation of beach rock at the surface and reef rock in the subsurface. The process of lithification which leads to the formation of beach rock is an unusual and interesting one, but does not play a major rôle in the consolidation of reef sediments. Beach rock results largely from the protective action of encrusting algae and to a less degree from carbonate precipitation from sea water. Because of the general lack of “fines” in reef flat and beach sands, matrix recrystallisation plays no part in beach rock formation. By contrast, the reef rock from the subsurface generally contains a higher percentage of fines and, below 100 feet, this material has been largely recrystallised to form a strong binding medium. The process of recrystallisation is apparently selective, those sediments with high matrix, high coral/algal ratio and low MgCO3content showing the highest degree of recrystallisation. Depth of burial shows no direct relationship to this process. Thus, of the two lithifying processes operative in the reef province, the less spectacular one of compaction and recrystallisation is the more important. Beach rock formation is significant in its influence on the present distribution of carbonate sands, but it makes little or no contribution to the total rock mass underlying the present reef.

ISSN:0016-7614    

DOI:10.1080/14400956208527874

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

Hatchericeras lakefieldensesp. nov. is described from Lower Cretaceous (Neocomian) deposits from near Lakefield, on the Normanby River, North Queensland. The genus has previously been recorded only from Lower Hauterivian? sediments of Patagonia.

ISSN:0016-7614    

DOI:10.1080/14400956208527875

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

The mineralogy of seven weathered profiles derived from Triassic shales in the Sydney area has been examined by X-ray and chemical techniques. The illite of the parent shales is converted, through the loss of potassium ions, to montmorillonite-illite inter-layered minerals in the leached shale and mottled zones; but in the soil zone, where maximum leaching occurs, these inter-layered minerals tend to form kaolinite and a 14Å mineral with properties similar to vermiculite. It is considered that the oxidation of adsorbed ferrous ions has been responsible for the development of the vermiculite-like mineral. Though quartz is lost from the profiles, the kaolinite content increases surfacewards at the expense of illite and related degraded products.

ISSN:0016-7614    

DOI:10.1080/14400956208527876

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

摘要:

This paper describes a palaeomagnetic study of the Cygnet syenite boss, associated dykes, hybrid rocks, and baked sediments, giving new information relevant to the age of the intrusion. All these groups have parallel directions with a steep negative inclination, except those somewhat affected by a commponent induced by the earth's present field. The latter component has been minimized by treatment in alternating magnetic fields and the resulting directions, which are parallel to those in the Tasmanian dolerite, are interpreted as being the direction of the earth's field at the time of cooling. This suggests that the Cygnet intrusions are probably closely related in time to the Tasmanian dolerites, as Carey (1958) has argued from structural considerations.

ISSN:0016-7614    

DOI:10.1080/14400956208527877

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor

ISSN:0016-7614    

DOI:10.1080/14400956208527869

出版商:Taylor & Francis Group    

年代:1962

数据来源: Taylor