History of the development of the East African Rift System: A series of interpreted maps through time

• ‘EARS’ Cenozoic rifting can be broadly split into two cycles.
• Southwards younging trend of the initiation of EARS 2 rifting in both branches.
• Other regions where the initiation of rifting seems to have propagated northwards.
• Peak rifting, subsidence and sedimentation in the majority of basins is Plio-Pleistocene.
• Many of the most significant events such as rift shoulder uplift not taking place until the last 1–2 My.

This review paper presents a series of time reconstruction maps of the ‘East African Rift System’ (‘EARS’), illustrating the progressive development of fault trends, subsidence, volcanism and topography. These maps build on previous basin specific interpretations and integrate released data from recent petroleum drilling. N–S trending EARS rifting commenced in the petroliferous South Lokichar Basin of northern Kenya in the Late Eocene to Oligocene, though there seem to be few further deep rifts of this age other than those immediately adjoining it. At various times during the Mid-Late Miocene, a series of small rifts and depressions formed between Ethiopia and Malawi, heralding the main regional rift subsidence phase and further rift propagation in the Plio-Pleistocene. A wide variation is thus seen in the ages of initiation of EARS basins, though the majority of fault activity, structural growth, subsidence, and associated uplift of East Africa seem to have occurred in the last 5–9 Ma, and particularly in the last 1–2 Ma. These perceptions are key to our understanding of the influence of the diverse tectonic histories on the petroleum prospectivity of undrilled basins.