Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Shelf Edge Architecture and Source-to-Sink Dynamics in the Northern Taranaki Basin, New Zealand
(1) The University of Texas at Austin, Austin, TX.
(2) Bureau of Economic Geology, The University of Texas at Austin, Austin, TX.
A detailed understanding of the architecture and depositional evolution of the shelf-edge region offshore northern Taranaki Basin, New Zealand, was developed through the study of 1600 sq. km. of seismic reflection data and its integration with well information. The study was focused in the Northern Graben, whose origin is attributed to the subduction of the Pacific plate under the Australian plate since early Oligocene and the subsequent back-arc rifting in the Plio-Pleistocene. A detailed seismic study of the Early Miocene to recent foreland phase of the graben’s history was performed for the purposes of addressing how the morphology and architecture of shelf edge reservoir types vary spatially and temporally, and to investigate the influence of tectonics in sedimentation. The interval is characterized by an overall regressive succession associated with generation of accommodation space due to tectonic subsidence and increase in sediment supply due to uplift.
Attribute extractions guided by key surfaces allowed the interpretation of stratigraphic patterns and guide the understanding of the basin’s sedimentary and tectonic evolution. Changes in seismic character and reflector configurations indicate two stratigraphic stages within the foreland phase related to variations in tectonics. The stratigraphically deeper section (stage one) is characterized by low angle seismic reflectors, high amplitude packages, and basin floor fan to channelized geomorphic elements. The shallower section (stage two; Giant Foresets Formation) is characterized by progradational to sigmoidal clinoforming reflectors with variously preserved or truncated topsets, channelized foresets and chaotic toesets. Large, deeply incised canyon systems of differing ages characterize stage two.
The analysis of isopach maps suggests that the reactivation of rifting faults during the back-arc phase played an important role in the deposition of the Giant Foreset Formation, initially confining sediments to the fault system. The extension of these faults to deeper intervals could have influenced the movement of volcanics during the Pleistocene that also played an important role funneling canyons and focusing deeper water deposition.