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

Abstract

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.

Rift Transfer Zones and the Stages of Rift Linkage in Active Segmented Continental Rift Systems

“…For example, in paired rift transfer zones, depending on the stress field orientation and inherited basement structures, with continued extension, unfaulted underlapping transfer zones can evolve into an overlapping geometry or faulted underlapping geometry. Also, stress rotation between rifting episodes in multiphase rifts can lead to the transformation of a paired rift transfer zone geometry into a compound transfer zone geometry (e.g., Turkana Depression, Fairhead, 1988;Emishaw et al, 2019;Morley, 2020).…”

Recent volcano-tectonic activity of the Ririba rift and the evolution of rifting in South Ethiopia

“…In the Turkana depression the MER and Kenyan rift overlap, giving rise to a complex region where extensional deformation is accommodated along a ~300 km-wide system of mainly extensional structures (Morley et al, 1992(Morley et al, , 1999Ebinger et al, 2000;Emishaw et al, 2019). The unusual breadth of the Turkana depression and its anomalous low topography are believed to be a consequence of the interplay between the terminations of the two main rift systems (MER, Kenyan rift) and the transversal (roughly NW-SE-trending) pre-existing Mesozoic basin of the Anza graben (Foster and Gleadow, 1996;Morley et al, 1992Morley et al, , 1999Ebinger et al 2000;Brune et al, 2017).…”

Initial Cenozoic magmatic activity in East Africa: new geochemical constraints on magma distribution within the Eocene continental flood basalt province

“…Fission track data suggest a protracted period of uplift and erosion from ~54 Ma, with clear indications of footwall uplift by ~30 Ma (Boone et al, 2019). The amount of lithospheric stretching in Palaeogene time predicted by subsidence modelling is small (~10%, Emishaw and Abdelsalam, 2019;Hendrie et al, 1994)). The pre-rift lithospheric structure as well as minor stretching within and adjacent to the Mesozoic rift system, therefore, may have served to enhance melting across a much broader region where some minor additional extension occurred (e.g.…”