Sigmoidal normal faults and evidence for vertical-axis block rotation in an oblique convergent margin: A 3D seismic example from offshore Colombia

Sigmoidal fold and fault geometries are typical kinematic indicators of strike-slip zones. We document kilometer-scale, normal faults with sigmoidal plan-view within the dextral pull-apart Bahia Basin, at rear obliquely convergent South Caribbean Deformed Belt, offshore Colombia. Using 3D seismic reflection data calibrated to wells, closely spaced, low-displacement, planar mapped Miocene strata. A series horizontal (time) slices computed attributes used interpret configuration these faults. The spaced display an east–west trend a progressive rotation into northwest–southeast trend. In map view, traces curve toward their tips, describing sigmoidal-Z geometry that terminates discrete northeast–southwest-trending structures observed may correspond either tension fractures, which form theoretically 45°, or antithetic shear fractures displacement formed 50°–70° boundaries zone. These scenarios lead clockwise block between 20° 40° This study shows first example vertical-axis rotations in western end margin is important use identify where paleomagnetic studies not available.