The first epoch of the Quaternary period (the most recent geologic time period) that lasted from 2,588,000 to 11,700 years ago. It is the period of time before the Holocene
U.S. Geological Survey, U.S. Department of the Interior, Volcano Hazards Program, Glossary, Washington, DC, USA 2011. http://volcanoes.usgs.gov/vsc/glossary/alluvium.ht ml, (ND/ Volc Emr - Amer) {795}