Development of Late Jurassic-Early Paleogene and Neogene-Quaternary Rifts Within the Turkana Depression, East Africa From Satellite Gravity Data

The Turkana Depression (TD) is a NW trending topographic corridor within the East African Rift System between the Ethiopia-Yemen plateau in the northeast and the East African plateau to the southwest. The Anza rift within the TD is a NW-SE trending failed arm of a late Jurassic rift-rift-rift triple junction. This rift is correlated with the Sudan and South Sudan rifts. The Anza rift is intersected by the East African Rift System represented by the N-S trending Turkana rifted zone. We image the lithospheric structure beneath the TD using satellite gravity data. We also use these data to model crustal density distribution beneath the Kino Sogo fault belt, part of the Turkana rifted zone. Our results show thinner crust (23-28 km) and lithosphere (140-150 km) beneath the TD. We interpret this as due to extension that resulted in the formation of the Kenya-Sudan and South Sudan rifts. Our results also show that crustal depth between 0 and 4.8 km is dominated by N-S density contrast anomalies and between 4.8 and 14.5 km by E-W anomalies. We interpret the N-S anomalies as due to the presence of Precambrian structure that might have facilitated strain localization during the initiation of the Kino Sogo fault belt. Differently, we interpret the E-W anomalies as due to the presence E-W trending faults that were formed in association with the development of the Anza rift and/or Turkana rifted zone and were later filled with Mesozoic and Cenozoic mafic dikes.