Jurassic and Cretaceous Tectonic Evolution of the Demerara Plateau – Implications for South Atlantic Opening

The Demerara Plateau is located on the northeast South America continental margin between 5° and 10° North, marking the northwest corner of the equatorial segment of the Atlantic Ocean. It is conjugate to the Guinea Plateau on the African margin which rifted from the Demerara during the Early Cretaceous opening of the Central Atlantic. Published studies of the Demerara Plateau are focused on its Cretaceous history, when the northern edge of the platform was formed by trans-tensional deformation along Atlantic transform faults, and its eastern edge by extensional deformation during rifting. The platform itself is commonly interpreted as a continental block left behind following South Atlantic rifting. Seismic data across the plateau reveal significant compressional deformation beneath an Albian unconformity. We suggest that this deformation is the result of early opening of the South Atlantic, with a rotation pole located close to the present-day Amazon delta. Allowing for this compression in plate reconstructions of the South Atlantic results in restorations which do not require large amounts of intra-continental deformation in South America, and consequently in a relatively simple plate model for the South Atlantic