Thrust faulting near oamaru from seismic reflection profiles

Abstract

DSIR Geology & Geophysics (Geophysics Division) acquired 18 km of high‐resolution multichannel seismic reflection data near Oamaru, in the east‐central South Island, in February 1988. The grid of seven Mini‐Sosie™ seismic profiles delineates Late Cretaceous normal faults and Miocene thrust faults in Cretaceous and Tertiary sediments. The thrusts offset shallow basaltic sills intruded into the Eocene sedimentary section. The minimal offset of older Cretaceous sediments indicates that the thrusts are reactivated Late Cretaceous normal faults. These data display the effect of tectonic events in the east‐central South Island since the Cretaceous, that could not be inferred from relatively flat‐lying surface outcrops. In particular, these profiles display structures related to the regional Late Cretaceous extension in the Canterbury area, and the pervasive compressional event that started with the propagation of the Pacific/Australian plate boundary across New Zealand during the mid‐late Miocene. © 1992 Taylor & Francis Group, LLC.