Tephrostratigraphy and chronology of late quaternary eruptives from the Tongariro Volcanic Centre, New Zealand

Abstract

The Tongariro Sub-group is defined to include all andesitic tephras of Aranuian age erupted within the Tongariro Volcanic Centre from 13 800 years B.P. (NZ1559) to the present day. The source vents include Mounts Ruapehu and Ngauruhoe, Tama Lakes, Blue Lake, Red Crater, North Crater, and upper and lower Te Mari Craters. Two previously named tephras, Ngauruhoe Tephra and Mangatawai Tephra, are given formation status. The units have accumulated intermittently over the period 0—1819 years B.P. and c. 1819—2500 years B.P. respectively. A further four formations are defined: Papakai Tephra has accumulated intermittently between c. 3400—9700 years B.P.; Mangamate Tephra, with six named members, was erupted mainly from the Tama Lakes-Ngauruhoe area between c. 9700—9780 years B.P.; Okupapa Tephra was erupted from Mount Ruapehu over 9790 years B.P.; and Rotoaira Lapilli, which marks the base of the Tongariro Sub-group, was probably erupted from lower Te Mari Crater 13 800 years B.P. Volumes are calculated and isopach maps are presented for four of the formations and three of the members.