Tephrostratigraphy of the marine sediments in the Wanganui Basin, New Zealand

Abstract

Abstract Twelve tephras, which range in age from earliest Marahauan (late Early Pleistocene) to latest Putikian (late Middle Pleistocene), have been identified in the marine Pleistocene sediments of the Wanganui Basin. Most occur in the early Okehuan (early Middle Pleistocene) part of the sequence and represent the initiation of the major rhyolitic volcanic activity of central North Island. Where there is no stratigraphic control, some of the tephras can be distinguished on the basis of fission-track dates, ferromagnesian mineral assemblage, and sometimes, on the partial chemical analysis of titanomagnetites. Only the Makirikiri Tuff Formation can be traced across the entire basin; other formations and tephra beds have not been preserved everywhere, or have not been located because of insufficient exposure.