首页   按字顺浏览 期刊浏览 卷期浏览 A petrological study of a vertical section of the Narrabeen Group at Helensburgh, N.S.W.
A petrological study of a vertical section of the Narrabeen Group at Helensburgh, N.S.W.

 

作者: F. C. Loughnan,  

 

期刊: Journal of the Geological Society of Australia  (Taylor Available online 1963)
卷期: Volume 10, issue 1  

页码: 177-192

 

ISSN:0016-7614

 

年代: 1963

 

DOI:10.1080/00167616308728539

 

出版商: Taylor & Francis Group

 

数据来源: Taylor

 

摘要:

A detailed petrological study has been made of a complete section of the Narrabeen Group exposed in a bore near Helensburgh. The Clifton Sub‐Group is characterised by two major cycles in which thick units of predominantly arenaceous sediments are interspersed with red‐brown claystones. Rock fragments are abundant in the sandstones, particularly near the base of the sub‐group, while siderite is common as a minor constituent. The red‐brown claystones show a marked contrast in composition with the shaly members of the thicker units in that quartz and siderite are absent or sparse and hematite is prevalent. However, the clay mineral contents of the two claystone formations differ. The upper or Bald Hill Claystone contains only kaolinite, whereas inter‐layered clay minerals and illite are present in addition to kaolinite in the lower or Stanwell Park Claystone. Hematite is absent from the upper few feet of the Bald Hill Claystone and kaolinite, partly in the form of vermicular crystals, may comprise the whole sample but elsewhere boehmite or siderite is prevalent. The texture varies from pisolitic to brecciated. The Gosford Formation overlying the Clifton Sub‐Group is composed predominantly of shales which resemble in texture and composition those of the later Wianamatta Group. A brief discussion of the origin of the Narrabeen Group is given.

 

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