Methods

Navigation was tracked with a Global Positioning System (GPS) Navstar satellite navigation system, with an uncertainty of $\sim$ 50m. Morphobathymetry was obtained during the 1994 cruise with a 15-beams Finnyard Echos 625 multibeam, covering an area of sea floor roughly equal to 2/3 of water depth. During the 1996 cruise we employed a Simrad EM12S, 81-beams system, with a swath approximately 3 to 4 times water depth. Processing of the multibeam data was carried out with the NEPTUNE-IRAP software by SIMRAD, The data underwent several cleaning and filtering steps before production of final grids and maps. In addition, we used the GMT WESSEL1998 and PLOTMAP LIGI1989 programs to produce other grids and maps.

Gravity was measured by a set of 4 quartz thermally stabilized MOD GMN-K gravimeters assembled by Vniigeofizika in Gelendzhik, Russia, mounted on gyroscopic platforms close to the ship's center of gravity, 0.7 m above sea level. Resolution was of 0.04 mGal. The instruments were calibrated on known reference points with a portable Lacoste and Romberg G-327 gravimeter. Two sets of magnetic data were recorded continously by two towed magnetometers, one a Mod GSM-19MD of GEM, Ontario, the other a Proton Precession model MPM-7 built by NIPI Okeangeofizika.

Multichannel seismic reflection profiles were obtained during the 1994 cruise, em- ploying two Sodera GI guns as sound source and a 24 channel streamer, with a group interval of 25 m. The near-offset was 150 m and shot interval was 50 m, allowing sixfold coverage. Digital acquisition was carried out with a Geometrics 2420, with a sampling rate of 1 ms, a record length of 11 s and an antialias filter of 180 Hz. This system operated at speed of between 4 and 5 knots. A single channel, 50 meters-long streamer was operated during multibeam surveys at 10 knots. Multichannel seismic data were processed at the Istituto di Geologia Marina, CNR Bologna, using an industry-standard package (DISCO by Cogniseis).

Heat flow measurements were performed by core sampling with the system GRUNT, designed and assembled at the Thermal Exploration Laboratory (NIPI Okeangeofizika), Gelendzhik, Russia. The sea-going part (KADR-1M) incorporates: a) a corer that ensures the recovery of undisturbed sediments, b) a self-recording thermogradiometer (ACTM-1), c) deepwater camera and bathometer for nearbottom water sampling. The shipboard module consists of a programmable control and recording unit ensuring programming of self recording instruments, readout, visualization, processing, and storage of measurements results. An automated geotechnical module (NGM-1) was also available for engineering and physical parameter measurements on the cores.

Rock sampling was carried out by conventional dredging.

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