The Geology of the Mellish Rise Region Off Northeast Australia: a Key Piece in a Tectonic Puzzle - Southern Surveyor Cruise SS02/2005 - Geoscience Australia Survey 274

The Mellish Rise lies off northeast Australia, trends northeast overall, and is about 700 km long and 300 km wide. Much of it lies in Australian territory. In the southwest, near Mellish Reef, a large area is shallower than 2500 m, but further northeast there are only occasional comparably shallow highs. To the northwest the Coral Sea Basin and the Louisiade Trough, and to the southeast the narrow South Rennell Trough and the west D'Entrecasteaux Basin are all deeper than 3500 m. The rise also lies to the north of another fragment of continental crust, the Kenn Plateau.

The Mellish Rise and Kenn Plateau have been the subject of recent geoscience surveys of R.V. Southern Surveyor, undertaken by Geoscience Australia, to determine their composition. The emphasis in this report is on the Mellish Rise survey (SS02/2005), during which 1189 km of multichannel seismic data were acquired using a 24 channel, 600 m long streamer and two GI airguns. In addition, multibeam and single beam bathymetry, and magnetic data were recorded. Forty-four dredge sites and five core stations were occupied to investigate the geology, and the great bulk of these deployments were successful. Dredge sites were concentrated on the Mellish Rise and Kenn Plateau, but are also included the Louisiade Plateau. Foraminiferal, nannofossil and petrological studies have been carried out on suitable rocks and sediments.