Late Miocene-Early Pliocene succession in Manutahi-1 (Wanganui Basin) : wireline log attributes of shelf sequences and systems tracts

Apatite and zircon fission track ages have been established for a suite of andstone beds within the Matemateaonga-Tangahoe succession in Manutahi-1 (Wanganui Basin, New Zealand). Individual samples exhibit a wide range of ages, but a young mode of Late Cenozoic ages consistently occur within most samples. In many cases this mode is one to a few million years older that the stratigraphic age of the horizons sampled. The young mode cannot originate from North Island basement, and a volcanic source can be discounted. The FT data unequivocally indicate a Southern Alps source for the bulk of the Late Miocene-Pliocene deposits in Wanganui and Taranaki basins. Moreover, the FT ages in relation to the stratigraphic ages highlight the high rates of exhumation in the Southern Alps 4-6 m.y. ago. (author)