Report and preliminary results of Meteor Cruise 29/2, Montevideo-Rio de Janeiro, 15.7.-8.8.1994.

Abstract

The three legs of METEOR Cruise 29 (Expedition Geo Bremen South Atlantic 1994) continued a long-term geoscientific study aimed at reconstructing the mass budget and current systems of the South Atlantic during the late Quaternary. This program is financially supported as a Special Research Project (Sonderforschungsbereich 261) by the German Science Foundation (Deutsche Forschungsgemeinschaft) since 1989.The main objective of the second leg of the 29th METEOR Cruise was to sample sedimentary deposits along transects across the continental margin off Uruguay and on the flanks of the Rio Grande Rise and Santos Plateau east and west of the Vema Channel. To systematically supplement the core material recovered during the 1993 METEOR Cruise M23/2 and the preceding Leg M29/1, the gravity corer, large box corer and multicorer were employed. Detailed analyses of this sample collection with geochemical, geophysical, micropaleontological and isotopic methods will determine the regional sedimentation patterns and their mostly climatically controlled late Quaternary variations. In the actual working areas these are predominantly influenced by water masses from high northern and southern latitudes and gravitational processes on the South American continental slope.During the entire leg continuous geoacoustic recordings were performed using the ship's systems PARASOUND and HYDROSWEEP. To determine the specific characteristics of a depositional regime which to a large extent is dominated by intensive bottom water currents, a high resolution survey with a series of echographic and bathymetric profiles combined with additional sediment sampling was planned for selected regions of apparently migrating mud waves in the central Argentine Basin. At a number of stations separate sediment core material was retrieved for geochemical analyses. Sampling of the water column with a multinet and a multiple water sampler complete the scientific program of the cruise.