Large-to Local-Scale Control of Pre-Existing Structures on Continental Rifting: Examples From the Main Ethiopian Rift, East Africa

Giacomo Corti,Daniele Maestrelli,Federico Sani

doi:10.3389/feart.2022.808503

Giacomo Corti, Daniele Maestrelli + Show 1 more

Open Access

https://doi.org/10.3389/feart.2022.808503

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Abstract

In the Main Ethiopian Rift (East Africa) a complex tectonic history preceded Tertiary rifting creating pre-existing discontinuities that influenced extension-related deformation. Therefore, this area offers the opportunity to analyze the control exerted by pre-existing structures on continental rifting at different scales. In this paper we present an overview of such an influence. We show that at a large scale (up to ∼800–1,000 km) rift localization has been controlled by a lithospheric-scale inherited heterogeneity corresponding to a Precambrian suture zone, separating two different lithospheric domains beneath the plateaus surrounding the rift. The inherited rheological differences between these two lithospheric domains, as well as the presence of pre-existing lithospheric-scale transversal structures, largely controlled the along-axis segmentation and symmetry/asymmetry of different, ∼80–100 km-long rift segments. Inherited transversal structures also controlled the development of off-axis volcano tectonic activity in the plateaus surrounding the rift. At a more local scale (&lt;80 km), inherited fabrics controlled the geometry of normal faults and the distribution and characteristics of rift-related volcanism. These observations document a strong control exerted by pre-existing structures on continental rifting at all different scales.

Highlights

Continental rift systems normally develop within a previously deformed lithosphere in which the distribution, architecture and evolution of deformation may be strongly influenced by pre-existing structures
This long tectonic history created pre-existing structures that controlled the development of the Ethiopian sector of the East African Rift System (EARS) from a regional to a local scale; the control of these mechanical heterogeneities is the focus of this review paper
The Goba Bonga lineament is characterised by lower values of the elastic thickness of the lithosphere (Te; PérezGussinyé et al, 2009), which shows a decrease from values of up to 40 km beneath the Ethiopian plateau to values of 10–15 km (Pérez-Gussinyé et al, 2009) in a narrow E-W domain corresponding to the transversal structure

Summary

INTRODUCTION

Continental rift systems normally develop within a previously deformed lithosphere in which the distribution, architecture and evolution of deformation may be strongly influenced by pre-existing structures. The main structures correspond to the roughly E-W to WNW-ESE-trending YererTullu Wellel and Goba Bonga volcano-tectonic lineaments (Figure 1, Figure 3), causing deformation and volcanic activity to extend for hundreds of kilometres into the southern portion of the Ethiopian plateau and marking the transition between the different MER sectors. The Goba Bonga lineament is characterised by lower values of the elastic thickness of the lithosphere (Te; PérezGussinyé et al, 2009), which shows a decrease from values of up to 40 km beneath the Ethiopian plateau to values of 10–15 km (Pérez-Gussinyé et al, 2009) in a narrow E-W domain corresponding to the transversal structure (see Figure 3) These zones of thinned crust or lithosphere beneath the YererTullu Wellel and Goba Bonga lineaments were possibly caused by either inherited lithospheric thinned regions or by syn-rift extension exploiting pre-rift weakness zones. This indicates a pre-rift, structural control on the current structure of the lithosphere (Corti et al, 2018a)

Rift Interaction and Linkage

CONCLUDING REMARKS