INTRODUCTION

In the South Atlantic (Fig.1) the Antarctica, South America and Africa Plates meet at the Bouvet Triple Junction (Fig.2), a key place for the understanding of structure and composition of ocean ridges. In the framework of Italian and Russian cooperative project with the main goal of depicting the structural, morphological and compositional elements of accretionary plate boundaries in the region, a first PNRA expedition in the area with R/V Strakhov in 1994 [] was performed. The areas West of the Bouvet I. and around the Triple Junction were investigated, including the terminal portion of the axial valley of Mid Atlantic Ridge (MAR) south of 54 15'S. Other than multibeam, multichannel and single channel reflection seismic, gravimetric and magnetometric investigations, several stations were occupied and sampled in the two areas. Our survey time was over when we were just in the proximity of the Bouvet Triple junction, leaving open several questions regarding its structural expression, that is broadly depicted by the intersection of MAR with the Conrad and Bouvet fracture zones.

**Figure 1:** Geographical setting of the study area. Topographic and bathymetric data by Sandwell and Smith [Sandwell and Smith(2001)].
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A second cruise was proposed to PNRA by IGM and planned in the area, focusing on swath-bathymetry investigations, magnetometry, gravimetry and sampling. We took the opportunity of the availability of R/V Gelendzhikof Central Geological Geophysical Expedition (CGGE, Russia), that was going to install a state-of-the-art multibeam system (EM-12-120S, SIMRAD, 3.3 times coverage of sea bottom). After some months of negotiations, at the end of 1995 PNRA and CGGE signed the contract. This second expedition started in Ravenna 9-feb-1996. Test and calibration of the multibeam system was done in two areas of Southern Adriatic Sea and of Ionian Sea (Taranto Canyon). After transit to Durban (South Africa), where ship embarked Italian and some russian scientists and technicians, we left 7-Mar-1996, and reached Abidjian (Ivory Coast) 8-may-1996, after 39 days of scientific operations in the Bouvet Area.

Hereafter, a description of the ship, equipment and their usage is given, along with details of the general settings, performances and some scientific and technical results.