The crustal structure of the Maurice Ewing Bank

Abstract

The Maurice Ewing Bank is a bathymetric high at the eastern termination of the Falkland Plateau in the South Atlantic Ocean. During the Jurassic, the Falkland Plateau was situated between the South American, Antarctic and African plates and therefore its crustal composition is of interest for plate kinematic reconstructions of the Southern Ocean. On the basis of recently acquired wide-angle seismic and potential field data, a crustal model is established for the Maurice Ewing Bank, the adjacent eastern Falkland Plateau Basin and the western Georgia Basin. According to the model, the Falkland Plateau Basin is floored by thick oceanic crust. An 80km wide continent-ocean transition zone is located towards the Maurice Ewing Bank. The data indicate that the Maurice Ewing Bank is composed of continental crust of up to 29km thickness. Its western part shows fast crustal velocities (>7.0km/s) and strong intracrustal reflections. The wide-angle data provide no evidence for strong tectonic or magmatic overprinting of the bank's central portion. The continental crust thins eastwards to 11km. The oceanic crust of the Georgia Basin is of average thickness (∼7km) for its type. Here, ship and airborne magnetic data confirm previously identified Mesozoic spreading anomalies and the onset of oceanic crust formation at M10n (∼133Ma) time.