The Principal Investigator will investigate the absence of deformation on the Magdelena fan, located on the northern Colombian convergent margin, using GLORIA images and single-channel seismic data collected in the summer of 1989 on the RRS Charles Darwin. Two competing models have been proposed to explain the lack of shortening on the fan. One proposes that the low surface slope of the fan suppresses deformation; thus sedimentation rates would alter the geometry of compressional deformation. In the other model, block tectonics in northern South America creates different amounts of convergence along the various blocks. If the block-boundary faults continue offshore across the active accretinary wedge then the amount of convergence should change across block boundaries. These models will be tested by determining the geometry, and rates and timing of the deformation near the edges of the fan.
