Ash-Flow Tuffs of the Galiuro Volcanics in the Northern Galiuro Mountains, Pinal County, Arizona: Usgs Professional Paper 1104 (Paperback) (ISBN-13: 9781287001683)

The upper Oligocene and lower Miocene Galiuro Volcanics in the northern part of the Galiuro Mountains contains two distinctive major ash-flow tuff sheets, the Holy Joe and Aravaipa Members. These major ash-flows illustrate many features of ash-flow geology not generally exposed so completely. The Holy Joe Member, composed of a series of densely welded flows of quartz latite composition that make up a simple cooling unit. is a rare example of a cooling unit that has a vitrophyre at the top as well as at the base. The upper vitrophyre does not represent a cooling break. The Aravaipa Member. a rhyolite, is completely exposed in Aravaipa and other canyons and on Table Mountain. Remarkable exposures along Whitewash Canyon exhibit the complete change from a typical stacked-up interior zonation of an ash flow to a non welded distal margin. Vertical and horizontal changes in welding, crystallization, specific gravity, and lithology are exposed. The ash flow can be divided into six lithologic zones. The Holy Joe and Aravaipa Members of the Galiuro Volcanics are so well exposed and so clearly show characteristic features of ash-flow tuffs that they could be a valuable teaching aid and a source of theses for geology students.

Author: Medora Louise Hooper Krieger
ISBN-10: 1287001688
ISBN-13: 9781287001683
Publisher: Bibliogov
Language: English
Published: 03/26/2013
Pages: 40
Format: Paperback
Weight: 0.20lbs
Size: 9.69h x 7.44w x 0.08d