Preprints
https://doi.org/10.5194/egusphere-2022-1365
https://doi.org/10.5194/egusphere-2022-1365
 
02 Jan 2023
02 Jan 2023
Status: this preprint is open for discussion.

The impact of rotational rifting on the evolution of the East African Rift System: an analogue modelling study

Frank Zwaan1,2 and Guido Schreurs1 Frank Zwaan and Guido Schreurs
  • 1Institute of Geological Sciences, University of Bern, Baltzerstasse 1+3, 3012 Bern, Switzerland
  • 2Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences, Potsdam, Germany

Abstract. The East African Rift System (EARS) represents a major tectonic feature splitting the African continent apart into the Nubian Plate situated to the west, and the Somalian Plate to the east. The EARS comprises various rift segments and two microplates (the Victoria and Rovuma plates) and represents a key location for studying rift evolution. Researchers have proposed various scenarios for the evolution of the EARS, but the impact of continental-scale rotational rifting, caused by the rotation of the Somalian Plate, has received only limited attention. In this study we apply analogue models to explore the dynamic evolution of the EARS within the broader rotational rifting framework. Our models show that rotational rifting leads to the lateral propagation of deformation towards the rotation axis, but we must distinguish between the propagation of distributed deformation, which can move very rapidly, and localized deformation, which can significantly lag behind. The various structural weakness arrangements in our models (representing pre-existing structural heterogeneities) lead to a variety of different structures. Laterally overlapping weaknesses are required for localizing parallel rift basins to create rift pass structures, possibly leading to the rotation and segregation of micro-plates, as is the case for the Victoria Plate in the EARS. Additional model observations concern the development of early pairs of rift-bounding faults flanking the rift basins, followed by the localization of deformation along the axes of the most advanced rift basins. Furthermore, the orientation of rift segments with respect to the regional (rotational) plate divergence affects deformation along these segments: oblique rift segments are less wide due to a strike-slip deformation component. Overall, our model results are a good fit with the large-scale features of the EARS, providing constraints on the timing of rift development and on the segregation and rotation of the Victoria plate within the broader rotational rifting framework of the EARS.

Frank Zwaan and Guido Schreurs

Status: open (until 23 Feb 2023)

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Frank Zwaan and Guido Schreurs

Data sets

Time-lapse imagery, digital image correlation (DIC) and topographic analysis of laboratory experiments simulating the evolution of the East African Rift System Frank Zwaan & Guido Schreurs https://www.dropbox.com/sh/6k34psul6cij4dh/AABpt-cnM1OyIEdolfTszmmya?dl=0

Frank Zwaan and Guido Schreurs

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Short summary
The East African Rift System (EARS) is a major plate tectonic feature splitting the African continent apart. Understanding the tectonic processes involved is of great importance for societal and economic reasons (natural hazards, resources). Laboratory experiments allow us to simulate these large-scale processes, highlighting the impact of rotational plate motion on the overall development of the EARS, an insight relevant to our interpretation of other rift systems around the globe as well.