The Structure of the Crust and Upper Mantle in the Region of Barbados and the Lesser Antilles

Summary The results of marine geophysical surveys across the Lesser Antilles in 1971 and 1972 by Durham University and the Royal Navy as part of the CICAR Project have revealed that the arc front sediment complex is nearly 20 km thick beneath the Barbados Ridge, where the igneous crust of the Atlantic is subducted beneath the Caribbean Plate. It appears that the sediment complex has grown away from the island arc, engulfing any bathymetric trench that was originally present. The Barbados Ridge is underlain by metamorphosed sediments and has been uplifted 4 or 5 km since the Pliocene. The crust beneath the Lesser Antilles island arc is about 35 km thick, and the crustal segments either side of the arc differ from each other in their crustal structure. The whole arc complex shows a change in character along the arc at Lat. 14deg;N. A positive gravity anomaly of 40 mgal computed to be the theoretical anomaly caused by the subducted lithosphere beneath the Lesser Antilles, is compatible with the interpretation of the crustal structure. The Lesser Antilles are an example of a maturely developed island arc complex.