Quaternary 6 : Period of geologic time from about 1.8 million years ago until the present. It contains the Pleistocene and Holocene epochs. (GSA 1999 Geologic Timescale)
U.S. Department of the Interior, U.S. Geological Survey, US Geological Society (USGS), Glossary of Volcano and Related Terminology, USGS/Cascades Volcano Observatory, Vancouver, Washington, USA 2006. http://vulcan.wr.usgs.gov/Glossary/volcano_termino logy.html, (ND/ Volc Sci - Amer) {493}