1998/05/01 by Phil Shane, P. C. Froggatt, Ian E.M. Smith +1 · 3 citations
Earth and Planetary Sciences · Social Sciences · #Geology and Paleoclimatology Research #Pacific and Southeast Asian Studies #Pleistocene-Era Hominins and Archaeology #Pumice #Geology #Silicic #Volcano #Rhyolite #Island arc #Mafic #Geochemistry #Volcanic rock #Paleontology #Subduction
paper · doi:10.1006/qres.1998.1968
openalex publication_date 1998/05/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
Sea-rafted Loisels Pumice is one of the few stratigraphic markers used to correlate late Holocene coastal deposits in New Zealand. Along with underlying sea-rafted products of the local Taupo eruption of ca. 1800 yr B.P., these events have been used to bracket the first arrival of humans at New Zealand. Loisels Pumice is dacitic to rhyolitic (SiO 2 63–78 wt%) in composition, but individual clasts are homogeneous (SiO 2 range ± 1 wt%). Characteristics include very low K 2 O (0.5–1.75 wt%) and Rb (<25 ppm) and a mineralogy dominated by calcic and mafic xenocrysts. Similar features are shared by pumices of the Tonga–Kermadec arc, suggesting a common tholeiitic oceanic source. Interclast diversity of Loisels Pumice suggests that it is the product of several eruptive events from different volcanoes. The differences in glass and mineral compositions found at various sites can be explained if the deposits are from different events. A multisource origin can also partially explain the discrepancy in reported 14 C ages (ca. 1500–600 yr B.P.) from different localities. Therefore, the value of Loisels Pumice as a stratigraphic marker is questionable, and it does not constrain the arrival of humans. The predominant westward drift of historic Tonga–Kermadec arc pumices and prevailing ocean currents suggest a long anticlockwise semicircular transport route into the Tasman Sea before sea-rafted pumice arrival in New Zealand. The diversity of the pumices indicates that silicic eruptions frequently occur from the predominantly basic oceanic volcanoes.