A major division of Pleistocene deposits and time in North America, named for deposits in Yarmouth, Iowa, and equivalent to the Mindel-Riss Interglacial Stage of Alpine Europe. In some places, fossil vertebrates are well represented. It was at least as warm as modern times and, in some regions, the deposits indicate that Yarmouth climates may have been semiarid. The dates are c 300,000-200,000 BP; the British equivalent is the Hoxnian and the Holsteinian Interglacial in northern Europe.