Abstract
The Barreirinhas deepwater fold-thrust belt is located at the landward termination of the Romanche Fracture Zone (RFZ) offshore NE Brazil. 2-D and 3-D seismic-reflection analysis integrated with borehole data shows folding and thrusting in the uppermost 10 km of basin fill in an area of >1200 km2. Thrust-hanging-wall anticlines are curved, up to 5 km wide and 500 m high, extending laterally >40 km. Associated thrust faults dip SW to S showing complex roots. Deformation is kilometer-scale upward and mainly backstepping.The Barreirinhas fold-thrust belt differs from other deepwater fold-thrust belts in that it developed primarily out-of-sequence, consists of imbricated thrust-sheets bound by multi-segment faults, contains numerous backthrusts, and lacks up-dip extension and a common basal décollement. Thrust-belt shortening was >12 km in the Late Cretaceous, and <2 km in the Cenozoic. We interpret the Barreirinhas break-back fold-thrust system to result from variations in far-field stresses (Mid-Atlantic ridge-push) and strain partitioning along the RFZ.