摘要:

Three stages, Payntonian, Datsonian and Warendian in ascending order, are proposed for sequences of trilobite and conodont faunas occurring about the Cambrian‐Ordovician boundary in the Burke River Structural Belt, western Queensland. They are defined with reference to the base of a measured section at Black Mountain, 59 miles (95 km) northeast of Boulia. The base of the Payntonian Stage is marked by the incoming of tsinaniid and saukiid trilobite faunas; that of the Datsonian by incoming conodonts of theCordylodus proavusAssemblage‐Zone, together with leiostegiid trilobites; and that of the Warendian by conodonts of theC. prion‐ScolopodusAssemblage‐Zone, with rare asaphid and dikelokephalinid trilobites. The top of the Warendian is marked by strata containing multicostate scolopodids.

ISSN:0016-7614    

DOI:10.1080/00167617108728740

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Various unmixing phenomena are observed in feldspars from solvsbergites and trachytes. The response to heat treatment of these feldspars is predetermined by the original unmixing processes. The cooling history of some solvsbergites is interpreted on the basis of the feldspar study and additional observations made on xenoliths, and evaluation of time intervals between the eruption of several trachytic flows is offered.

ISSN:0016-7614    

DOI:10.1080/00167617108728741

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The Blue Tier Batholith in northeastern Tasmania is a composite, magmatic intrusion of Upper Devonian age, that intruded a folded, essentially unmeta‐morphosed Siluro‐Devonian sedimentary sequence at a rather high level in the crust. Aureoles of contact metamorphism in the sedimentary sequence are narrow. The batholith consists of several petrologically and structurally distinct components that intruded in an evolutionary sequence, with the younger units generally being more felsic. The regional stress environment appears to have been one of dilation across pre‐existing structures, and regional tension is envisaged.

ISSN:0016-7614    

DOI:10.1080/00167617108728742

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Natural hydrous silicas may be subdivided into three well‐defined structural groups—opal‐C (well‐ordered α‐cristobalite), opal‐CT (disordered a‐cristobalite, a‐tridymite) and opal‐A (highly disordered, near amorphous). Lussatite from the original locality is identical with opal‐CT and thus appears to be a legitimate term for this class of opal. Although the prime criterion used is the nature of the X‐ray diffraction pattern, supplementary information from infra‐red absorption, dilatometer and thermal techniques supports the three‐fold classification.

ISSN:0016-7614    

DOI:10.1080/00167617108728743

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Mapping has shown Gosse Pile, a near‐vertical uitramafic part of the Giles Complex, to be a multiple intrusion. The first rocks form a layered sequence of cumulates, dominated by orthopyroxenite, in which cyclic units can be recognised. Following deformation, which has removed most of the more felsic units of the layered sequence, there have been intrusions of noritic rocks, including mafic pegmatites, picrites and several generations of dolerite.

ISSN:0016-7614    

DOI:10.1080/00167617108728744

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Mineralogically complex shale horizons interbedded with, and underlying, the Brockman Iron Formation at Mt Tom Price, Western Australia, are compared with equivalent sections at Wittenoom and Yampire Gorge. Despite the alteration by fairly intense post‐depositional folding, faulting and weathering, very limited evidence favouring a primary pyroclastic source is indicated. By acting as effective seepage horizons for percolating meteoric waters, the upturned shale bands, which are part of the truncated synclinal folds in the Brockman Formation, have actively promoted supergene enrichment of the iron ore during lateritization and have themselves undergone considerable mineralogical reconstitution. By means of semi‐quantitative mineralogical data from samples in a reconstructed weathering profile, it is postulated that the formation at Mount Tom Price was subjected to two periods of lateritization separated by a period of diagenesis. Of these cycles the first was probably the most intense and hence responsible for most of the supergene iron ore enrichment in the region. The deposits at Wittenoom and Yampire Gorge were also affected by a period of intense diagenesis. However, they formed in an essentially anaerobic environment with little tectonic disturbance, conditions which differed markedly from those at Mt Tom Price.

ISSN:0016-7614    

DOI:10.1080/00167617108728745

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

ISSN:0016-7614    

DOI:10.1080/00167617108728739

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor