Evolution of the broadly rifted zone in southern Ethiopia through gravitational collapse and extension of dynamic topography

Emishaw, Luelseged; Laó‐Dávila, Daniel A.; Abdelsalam, Mohamed G.; Atekwana, Estella A.; Gao, Stephen S.

doi:10.1016/j.tecto.2016.12.009

Cited by 24 publications

(15 citation statements)

References 46 publications

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“…The numerical model includes only the lithosphere and shallow asthenosphere; hence, it does not account for mantle‐related topographic changes caused by asthenospheric flow [ Emishaw et al , ], small‐scale convection [ van Wijk et al , ], or whole‐mantle convection [ Flament et al , ; Rubey et al , ]. These dynamic topography contributions add to the isostatically compensated topography, especially above regions of focused upwelling.…”

Section: Numerical Modelingmentioning

confidence: 99%

Controls of inherited lithospheric heterogeneity on rift linkage: Numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression

2017

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Inherited rheological structures in the lithosphere are expected to have large impact on the architecture of continental rifts. The Turkana depression in the East African Rift connects the Main Ethiopian Rift to the north with the Kenya rift in the south. This region is characterized by a NW‐SE trending band of thinned crust inherited from a Mesozoic rifting event, which is cutting the present‐day N‐S rift trend at high angle. In striking contrast to the narrow rifts in Ethiopia and Kenya, extension in the Turkana region is accommodated in subparallel deformation domains that are laterally distributed over several hundred kilometers. We present both analog experiments and numerical models that reproduce the along‐axis transition from narrow rifting in Ethiopia and Kenya to a distributed deformation within the Turkana depression. Similarly to natural observations, our models show that the Ethiopian and Kenyan rifts bend away from each other within the Turkana region, thus forming a right‐lateral step over and avoiding a direct link to form a continuous N‐S depression. The models reveal five potential types of rift linkage across the preexisting basin: three types where rifts bend away from the inherited structure connecting via a (1) wide or (2) narrow rift or by (3) forming a rotating microplate, (4) a type where rifts bend towards it, and (5) straight rift linkage. The fact that linkage type 1 is realized in the Turkana region provides new insights on the rheological configuration of the Mesozoic rift system at the onset of the recent rift episode.

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Section: Numerical Modelingmentioning

confidence: 99%

Controls of inherited lithospheric heterogeneity on rift linkage: Numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression

2017

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“…The eastern branch extends from the Afar Depression in the northeast and trends southward for a distance of ~2,200 km through the Main Ethiopian Rift (e.g., Corti, ), the Turkana Rift, and the Kenya Rift, to the North Tanzanian Divergence (Figure a; e.g., Chorowicz, ). The Afar Depression and the Main Ethiopian Rift are associated with the Ethiopia‐Yemen Plateau whereas the eastern branch and western branch are associated with the East African Plateau (Figure ; e.g., Emishaw et al, ). The two plateaus are separated by the Turkana topographic corridor (Figure ; e.g., Emishaw et al, ).…”

Section: Tectonic Settingmentioning

confidence: 99%

“…It also first referred to as the Basin and Range of Ethiopia by Moore and Davidson (1978). The characteristics of this rift zone are recently summarized in Emishaw et al (2017). The other segment is the North Tanzanian Divergence, which represents part of the eastern branch ( Figure 1; Dawson, 1992;Foster et al, 1997;Le Gall et al, 2008;Nonnotte et al, 2008;Albaric et al, 2010Albaric et al, , 2014Plasman et al, 2017).…”

Section: 1029/2018tc005065mentioning

confidence: 99%

Lithospheric Controls on the Rifting of the Tanzanian Craton at the Eyasi Basin, Eastern Branch of the East African Rift System

et al. 2018

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Continental rifts most often nucleate within orogenic belts. However, some studies in the East African rift system have shown that continental rifts can also develop within cratons. This work investigated the ~1.5‐Ma Eyasi basin, which propagates in a WSW direction into the Tanzanian craton. The basin is located where the eastern branch of the East African rift system transitions from a narrow rift (~70 km wide) to the wider (~300 km wide) North Tanzanian Divergence. Unlike the rest of the eastern branch segments, the Eyasi basin does not follow the Mozambique orogenic belt located on the eastern margin of the Tanzanian craton. This work generated lithospheric‐scale sections across the basin using (1) digital elevation model to map surface rift‐related brittle structures; (2) aeromagnetic data to determine the depth to the Precambrian basement; and (3) World Gravity Model 2012 to estimate crustal and lithospheric thickness by applying the two‐dimensional radially averaged power spectral analysis and two‐dimensional forward gravity modeling. These cross sections show that the Eyasi basin nucleates within a previously unidentified suture zone within the Tanzanian craton and that this suture zone is characterized by thinner lithosphere that can be as thin as ~95 km. This zone of thinner lithosphere is offset southeastward from the surface expression of the Eyasi basin and might have facilitated the formation of other basins further south. Furthermore, the lithospheric thickness map indicates that the Tanzanian craton is heterogeneous and possibly composed of multiple smaller cratonic fragments.

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“…The presence of a thicker crust beneath the East Africa plateau can easily be explained as due to a combined effect of the presence of Precambrian cratons and orogenic belts and isostatic compensation due to elevated topography. It is less clear to us why there is a relatively thick crust beneath the southwestern part of the Ethiopia‐Yemen plateau since this region is dominated by the broadly rifted zone of the Main Ethiopian Rift (e.g., Emishaw et al, ). Receiver function passive seismic studies by Dugda et al () and Keranen et al () in the broadly rifted zone immediately north of our study area calculated crustal thickness ranging between 38 and 27 km for 10 of the broadband seismic stations used in these studies.…”

Section: Discussionmentioning

confidence: 99%

“…These rifts will be referred to here as the Kenya-Sudan Rifts (KSR). The N-S to NE-SW trending Neogene-Quaternary rifts are represented by segments of the Eastern Branch of the EARS including the Turkana rifted zone (Figure 1a; e.g., Bonini et al, 2005;Brune et al, 2017;Corti et al, 2019;Dunkelman et al, 1989;Ebinger et al, 2000;Emishaw et al, 2017;Morley, Wescott, et al, 1999;Rosendahl et al, 1992;Vetel et al, 2005;Vetel & Le Gall, 2006).…”

Section: Introductionmentioning

confidence: 99%

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

Emishaw

Abdelsalam

2019

Tectonics

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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.

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Evolution of the broadly rifted zone in southern Ethiopia through gravitational collapse and extension of dynamic topography

Cited by 24 publications

References 46 publications

Controls of inherited lithospheric heterogeneity on rift linkage: Numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression

Controls of inherited lithospheric heterogeneity on rift linkage: Numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression

Lithospheric Controls on the Rifting of the Tanzanian Craton at the Eyasi Basin, Eastern Branch of the East African Rift System

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

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