The pliocene - Pleistocene Seismic stratigraphy of part of the offshore South Taranaki and South Wanganui Basins

Abstract

Petroleum industry seismic reflection data in the South Taranaki and South Wanganui Basins has been tied to petroleum wells in the area, giving a sequence stratigraphic model of the geology of the area. Subsidence rates have been calculated for nine sites in the area, paleogeographic models of the area have been developed, and seismic reflectors have been correlated with the eustatic sea level curve of Haq et al (1988). The Pliocene - Pleistocene history of the South Taranaki and South Wanganui Basins has been dominated by highly active tectonism. Frequent eustatic change through this period resulted in widespread unconformities which can be traced through the area, and correlated with existing eustatic sea level curves. High subsidence rates through the Pliocene caused the sedimentary response to eustatic change to be quite different to those expected in areas with less subsidence. During the Pleistocene the area was dominated by the rapid formation of two depocentres, one in the southern South Wanganui Basin, the other in the South Taranaki Graben, adjacent to the Maui-2 well. Between these depocentres gentle uplift has resulted in erosion, preventing Pleistocene seismic reflectors being tied to wells.