Figure 2. Composite map showing continental structural features (Nicholas et. al., 2007), with offshore residual gravity (Oliveira, 2007). The NW-SE anomalies seems to cut the N-S structures, and at least one of them is clearly related to the Aswa Lineament or Aswa Transfer Zone (ATZ), as it can be observed from residual gravity results. This is a Precambrian structural feature, more than 1500km long, extending through Tanzania Craton from the end of Albert Rift Valley in Congo, passing through Kenya Rift and extending at least to the Dar es Salaam onshore area.