Structure and evolution of the Cayman Trough oriental margin : Legacy seismic data and samples

The Northern boundary of the Caribbean plate, and more specifically the Gonâve microplate, is the locus of intense tectonic activity partly accommodated by two strike-slip fault systems (the Enriquillo-Plantain Garden Fault Zone (EPGFZ) to the south and the Septentrional-Oriente Fault Zone (SOFZ) to the North) and by the opening of the Cayman Trough to the west and the Haitian fold-and-thrust belt in the east. This region has been extensively studied for several years since the earthquake of 12 January 2010; however, the deformation in the Gonâve Gulf to the west of Hispaniola island has not yet been well characterised. Multibeam bathymetric and seismic reflection data from multiple oceanographic campaigns in the study area have enabled us to identify tilted blocks from the eastern Cayman Through continental margin with low-angle normal faults. Seismic horizons allow us to identify the roof of syn-rift units in the Gonâve Gulf with an initiation of the rifting between 49 and 56 My.

New Ar/Ar dating of granodiorites recovered during submersible dives (CAYVIC cruise) on tilted blocks in the distal part of the margin, together with the interpretation of newly processed seismic profiles from the CASIS oceanographic campaign crossing the Ocean Continent transition, provide the timing and geometry of the tectonic structures of the eastern continental margin. Extending from north of Jamaica to at least the eastern part of the Gonâve Gulf, with a length of 450 km, the continental margin appears relatively classical, with a beta factor of 2.7.

NE-SW compression in the Gonâve Gulf, linked to the collision with the North American plate, reactivates the extensive structures and creates new compressive structures. We propose a spatio-temporal evolution of tectonic structures from the formation of the Eastern Cayman trough margin to the west to its reactivation in the Haitian fold-and-thrust belt to the east.