Enhanced Imaging of an Active Collision Zone: The South Falkland Basin

The South Falkland Basin is an active foreland basin located at the southern end of the Falkland Plateau. The basin was formed by flexure of the lithosphere of the South American Plate under the load of the Burdwood Bank, a continental fragment of the predominately oceanic Scotia Plate. The entire region is submarine, so the basin can be well imaged. It is therefore an ideal place for a detailed analysis of the geological structures comprising an active collision zone.

2D marine seismic reflection data were acquired by Geco-Prakla in 1993 and have been generously provided for this research project. These data have been reprocessed with modern seismic processing and imaging techniques such as radon, source signature deconvolution and pre-stack time and depth migration. Enhanced images of the deeper structures reveal normal faulting ranging from Mesozoic to Recent times within the flexed plate. Further south, convergent thrust faulting and piggy-back structures of Cenozoic age are present.

Previous interpretations based on time-migrated data suggested that the normal faults were listric. On the depth-migrated sections, however, these faults are approximately planar and deeply penetrating (up to 15 km). The depth images also show that the normal faults were active during plate flexure. The presence of these active planar normal faults suggests that the upper crust does not support crustal loads in accordance with simple flexural models.