Erosion and deposition on a tilting continental shelf during quaternary oscillations of sea level

Abstract

Abstract Continuous seismic profiles of high resolution were obtained of the continental shelf and upper slope between Napier and Castlepoint, New Zealand. They illustrate the topographic and stratigraphic effects of sea level changes on a tectonically active continental shelf. The profiles show a maximum of four, seaward-tilted unconformities which are used to define four named formations and “basement”. The formations onlap onto a relatively steeply dipping “basement” of middle Quaternary age and are, therefore, late Quaternary in age. They are constructed of prisms of sediment that parallel the coast. The prisms built the continental shelf upwards during (interglacial) periods of high sea level and outwards during (glacial) periods of low sea level. Waves and currents erode rock platforms near the present shore during periods of high sea level and cut planar surfaces in soft sediments on the middle and outer continental shelf during periods of low sea level. The rock platforms have been elevated to for...