A teleseismic study of the West African craton margin in Senegal: P‐wave slowness and azimuth anomalies

Summary Slowness‐azimuth anomalies for P ‐arrivals at the Kedougou temporary teleseismic array on the West African craton, near its western margin, are small except for westerly azimuths, implying uniform structure beneath the array itself and the existence of a steeply dipping refracting interface in the mantle to the west. At the Missira array, located on the Mauritanide orogenic belt west of the craton margin, the pattern of slowness anomalies can be explained by north‐dipping upper crustal structure, plus a single transition east of this array, across which the velocity contrast reverses with depth. A single transition could explain the data from both arrays and could be the downward extension of the craton margin into the upper mantle. That boundary demarcates lower velocity sub‐orogenic structure from higher velocity (˜ 8 per cent) sub‐cratonic structure between ˜ 80 and ˜ 220 km, while at greater depths the sub‐cratonic structure has ˜ 3 per cent lower velocity. This model agrees with models previously derived from P‐wave delay‐time anomalies and is qualitatively consistent with the pattern of late P‐ arrivals which are interpreted as multipathed refractions across the boundary.