RECENT TECTONIC ACTIVITY IN THE SOUTH BARBADOS PRISM DEEP-TOWED SIDE-SCAN SONAR IMAGERY

Data collected during the DIAPISAR Cruise (Nov. 1990) using the French deep-towed side-scan-sonar (S.A.R.) are presented. These data provide clear evidence of recent tectonic activity in the southern part of th e Barbados accretionary prism. Many markers as linear lineaments or 's igmoidal features' which are observed on diagenetically indurated sea- floor are the surficial traces of faults or folds and networks of conj ugate fractures where fluids are released through the structures and p rovide very active venting. These markers can serve as a basis for det ailed mapping of some of the tectonic structures and for an analysis o f their kinematic evolution. Their geometry suggests the occurrence of reworked folds and shear zones. This domain is affected by abundant c lay-diapiric tectonics due to the interaction between: (1) the sedimen tological context characterized by the important terrigenous supplies coming from the Orinoco River and building a wide prodelta in which le vels of clay supersaturated in water can act as decollement layers, an d (2) the geodynamic context of the area situated in the connection zo ne of three different types of margins. The data presented show that, on the eastern end of the South Caribbean wrench fault system, shear s tresses can rework either 'en echelon' folds associated with this syst em or compressional structures due to subduction. The most recent stru ctures seem largely due to the influence of shearing and correspond to transpressive or transtensive deformations rather than pure compressi onal structures. (C) 1998 Elsevier Science B.V. All rights reserved.