Sites for Leg 183 were selected on the basis of multichannel seismic (MCS), bathymetric, satellite-derived gravity, sonobuoy, coring, and dredge data collected during several surveys on board Australian, French, and U.S. ships (Fig. F2). The type and quality of seismic site survey data vary (see Table T1 for a summary of seismic parameters). Some surveys were undertaken before the availability of Global Positioning System (GPS) coverage, and these have less reliable navigation data.
Australian Geological Survey Organisation (AGSO) scientists on board the Rig Seismic acquired 5600 km of MCS, bathymetric, gravity, and magnetic data over the Kerguelen Plateau between 50°S and 60°S in 1985 (Ramsay et al., 1986). Segments of the Rig Seismic Survey 47 (RS47) MCS data were used to locate proposed drill sites KIP-7C (central plateau), 10C (Enderby Basin), and 14C (Labuan Basin).
The 1986 Marion Dufresne survey (MD47) examined the plateau between 55°S and 63°S, collecting 4450 km of coincident MCS, bathymetric, gravity, and magnetic data (Schlich et al., 1988). Proposed drill site KIP-13A (southern plateau) is located at the intersection of the MD47 and the Rig Seismic survey 180 (RS180) MCS lines, and KIP-13C (Site 1136) lies nearby on the plateau's eastern flank.
As part of ODP site surveys for Leg 121 in 1986, scientists on board the Robert D. Conrad acquired 4400 km of single-channel seismic reflection, bathymetry, gravity, and magnetic data on Broken Ridge, including some data in the vicinity of proposed drill sites KIP-9B and KIP-9C (Peirce, Weissel, et al., 1989). In addition, more than 50 sonobuoys were deployed to investigate the velocity structure of the sedimentary section. The site survey was conducted by Lamont-Doherty Earth Observatory (LDEO) scientists (Chief Scientist Jeffrey K. Weissel) and supported by the U.S. National Science Foundation.
During two 6-week marine surveys over the southern Kerguelen Plateau in 1997, AGSO and University of Texas Institute for Geophysics scientists acquired ~3500 km of high-quality MCS and other geophysical data. Survey 179 concentrated on Elan Bank, a prominent salient extending westward from the main Kerguelen Plateau (see Fig. F2). Two short lines were recorded specifically to support ODP drilling on the central Kerguelen Plateau (proposed drill sites KIP-7B [Site 1138] and KIP-7C) and Elan Bank (KIP-6C [Site 1137] and KIP-6D). Approximately 2000 km of MCS data was collected together with bathymetric, gravity, and magnetic data. Survey 180 focused on the plateau's eastern margin, including a short ODP site survey on the southern Kerguelen Plateau (KIP-13A and KIP-13B [Site 1135]). MCS data from survey 180 total ~1500 line-km with coincident bathymetric, gravity, and magnetic data.
Australia's site surveys on board the Rig Seismic were funded and conducted by AGSO (Project Leader Phil Symonds; cruise leaders Doug Ramsay and George Bernadel), in collaboration with the Institute for Geophysics, The University of Texas at Austin (MCS data processing), and the Department of Geology, University of Oslo, Norway, with financial support for U.S. scientist involvement provided by the U.S. Science Support Program of Joint Oceanographic Institutions, Inc.
The KERIMIS (Kerguelen, Imagerie Multifasceau et Imagerie Sismique) campaign, in February and March of 1998, acquired ~2000 km of MCS data and dredged >1000 kg of rocks from the northern Kerguelen Plateau to investigate the feature's structure and geodynamics and to conduct site surveys for ODP Leg 183. Two major transects across the entire northern plateau from the Enderby Basin to the Australia-Antarctic Basin were completed, and three dedicated site surveys were undertaken for proposed drill sites KIP-1D (Site 1139) and KIP-1E (Skiff Bank/Leclaire Rise), KIP-2C and KIP-2E (Site 1140) (northern plateau), and KIP-3C and KIP-3F (central plateau).
France's site survey on board the Marion Dufresne was conducted by the Ecole et Observatoire des Sciences de la Terre of the Université Louis Pasteur (Strasbourg 1) (Chief Scientist Roland Schlich), in collaboration with the Département des Sciences de la Terre et de l'Environnement de l'Université Libre de Bruxelles, with the assistance of the Institut Français de la Recherche et de l'Exploitation de la Mer with MCS, and the logistical and financial support of the Institut Français pour la Recherche et al Technologie Polaires.