During the 4 days cruise (of a total of 7 days including transits) around we obtained:
3500 km
from 4500 to 10 m water depth).
1300 km of SBP lines
Previously collected multichannel seismic profiles together with altimetry and multibeam data acquired during this cruise provide the basis to define the structural setting of the southern tip of South America. The overall geometry of the continental margin shows a regional eastward curvature that follows the counter-clockwise tectonic rotation of Tierra del Fuego. Two re-entrant zones are present at about 54S and 55:30S, and these are separated by a lobe, or promontory, that corresponds to a prominent basement-involved structural high imaged in lines IT95-168 and 181 [Polonia et al.(2007)]. The forearc basin is undeformed only where the shelf break is shifted towards the continent (regions with narrow shelf), suggesting a regional structural control on margin lobes and basin development. Satellite altimetry data clearly show along strike variations in free-air gravity anomaly associated with these structures. North of 52S, the continental margin is linear and the trench is a continuous feature without major discontinuities; subduction processes are mainly related to sediment consumption and tectonic erosion, the dècollement is shallow and the wedge is narrow. The multibeam data collected at about 53S have shown that the transition between the linear trench to the north and the terraced and segmented forearc to the south, is located on a major NE/SW trending tectonic feature, that offsets right laterally the outer deformation front and contributes to producing a structural high that may act as a barrier for the continent derived sediments and prevent their distribution along the continental margin. As a result, most of the sediments are trapped in the forearc basin that develops to the south. This oblique right-lateral fault probably develops to accommodate differential motion along the plate boundary. The lack of multibeam data along the entire margin does not allow to reconstruct the detailed geometry and lateral continuity of these features. However, we can propose that they may be related to zones of weakness in the oceanic and/or continental plates and may be driven by strain partitioning.
Nothing at the moment can be said about the morphology and tectonics in the Magellan Strait. However, the multibeam and SBP data that were collected will allow us to have an insight into this important fault.