ISSN:0812-0099    

DOI:10.1080/08120098708729422

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The Hianana Volcanics consist of bedded tuff and dacitic lava that form a locally mappable unit within the extensive, Late Permian silicic volcanic sequence of northeastern New South Wales. Principal components of the bedded tuff are crystal and volcanic lithic fragments ranging from coarse ash to lapilli, accompanied by variable amounts of fine ash matrix. Well denned plane parallel thin bedding is characteristic. Sandwave bed forms, including low‐angle cross‐beds and wavy beds, are confined to an area of 2–3 km2coinciding with the thickest sections (70 m) of bedded tuff. A high‐aspect ratio flow of porphyritic dacitic lava overlies the bedded tuff in the same area. The setting, lithofacies, extent and geometry of the bedded tuffs of the Hianana Volcanics are comparable with modern tuff rings which are composed of the deposits from base surges generated by explosive phreatomagmatic eruptions at primary volcanic vents. Many of these have also discharged lava late in their activity. Proximal parts of the Hianana tuff ring were buried by the porphyritic lava after the phreatomagmatic eruptions had ceased. In more distal sections, the bedded tuff is less than 10 m thick and dominantly comprises fine grained, plane parallel, very thin beds and laminae; these features suggest an origin by fallout from ash clouds that accompanied the phreatomagmatic eruptions. The distal ash was covered and preserved from erosion by a layer of welded ignimbrite, the source of which is unknown.

ISSN:0812-0099    

DOI:10.1080/08120098708729423

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098708729424

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098708729425

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098708729426

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098708729427

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098708729428

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098708729429

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098708729430

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0812-0099    

DOI:10.1080/08120098708729431

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor