Seismic analysis and models from a rifted submarine plateau of continental origin: Great South Basin and Bounty Trough

• Main Authors: Grobys, Jan, Gohl, Karsten, Uenzelmann-Neben, Gabriele, Davy, B., Barker, D., Deen, T.
• Format: Conference Object
• Language: unknown
• Published: 2004
• Subjects: Bounty Trough; Campbell Plateau; New Zealand; Pacific; Southern Ocean
• Online Access: https://epic.awi.de/id/eprint/12146/; https://hdl.handle.net/10013/epic.22579

The Campbell Plateau and Chatham Rise are large submarine plateaux of continental origin forming part of the submarine New Zealand continent. Bounty Trough lies parallel to the former Gondwana subduction zone along the northern margin of Chatham Rise. At its western end, Bounty Trough (BT) connects with the Great South Basin (GSB). The whole region formed part of Gondwana until extension and subsequent seafloor spreading formed the Southern Ocean in the Late Cretaceous. Prior to the break-up of Gondwana, New Zealand was situated at the proto-Pacific plate boundary of Gondwana. Although the timing of break-up is relatively well defined, processes of break-up and the development of the continental fragments forming Campbell Plateau and Chatham Rise are not yet understood. It is expected that these processes played a key role in the development of Gondwanas plate boundary from a convergent margin to continental rifting. One model suggests that the Cretaceous rift evolved from an already existing back-arc basin, a proto-Bounty Trough. It may also be possible that the trough first developed as a rift system of the Southern Pacifics early opening as plate-kinematic reconstructions of the South Pacific region suggest.To investigate the evolution processes of these submarine plateaux, a geophysical and geolo-gical survey was conducted across the Campbell Plateau and Bounty Trough in 2003. The survey carried out two deep seismic transects with an ocean-bottom seismograph (OBS) spacing of 10-20 km in combination with a series of crustal multichannel seismic (MCS) reflection lines across the GSB and BT. The OBS records were bandpass-filtered and deconvolved. Magnetic and gravity data provide further constraints on the crustal models.The MCS profiles across the Bounty Trough show about 1.2 s (TWT) thick layered sediments with an incised valley. In most parts, basement can be identified in the reflection data, how-ever, in places only the OBS model allows discrimination of basement from older sediments. Internal basement ...