Detection of Miocene saucer-shaped sills (offshore Senegal) via integrated interpretation of seismic, magnetic and gravity data

The Atlantic margin offshore Senegal has been explored by seismic reflection and GRAV-MAG surveys. High-amplitude, laterally transgressive seismic reflectors are found to coincide with gravimetric and magnetic highs. Once seismic data are integrated with potential fields modelling, these reflectors can be safely interpreted as saucer-shaped igneous sills, up to some hundreds of metres thick, some km wide. The occurrence of hydrothermal vent complexes and forced folds in the strati-graphic sequence above the sills constrain the intrusion age to the Miocene. Field observations and in-situ magnetic susceptibility measurements of Oligocene-Miocene and Quaternary igneous rocks emplaced in coastal Senegal support this interpretation.