The Tectonic Evolution of the Pegasus Basin and Implications for the Transition From a Subductive to Transform Plate Boundary, Offshore New Zealand
The Pegasus Basin overlies part of the transitional zone between oblique southwest subduction of the Pacific Plate below the East Coast of the North Island of New Zealand, and transform strike slip faulting through the South Island along the Alpine Fault, where plate motion becomes more margin-parallel. A 2D seismic dataset from Pegasus Basin across the Hikurangi-Kermadec trench, and associated accretionary prism provide an opportunity to investigate the tectonic evolution of this transpressive margin through interpretation and restoration of tectonically balanced sections. Seismic profiles oriented perpendicular to the margin, demonstrate a change in strain accommodation along the margin. These seismic profiles are structurally interpreted and reconstructed to identify changes in accommodation and shortening throughout the evolution of the margin. Tectonostratigraphic packages are utilized to reconstruct the various components within the basin, as their timing is associated with activation or suspension of motion along the compressional thrusts. Values for compression and strain accommodation along these thrusts are evaluated through structural reconstructions, and compared to known shortening values from onshore data and previous studies. Currently there are no wells that test for the petroleum potential of the basin, though the basin contains various petroleum indicators including bright-spots, flat-spots, and an almost universal bottom simulating reflector (BSR). Most of these seismic anomalies are associated with potential trapping structures. Identifying the timing of the structures, generation, and migration of petroleum along this previously unexplored margin creates further confidence in the petroleum accumulations within the Pegasus Basin.
AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017