Role of Surface Processes and Mantle Plumes in the Formation of Microcontinents: Insights from Numerical Modeling and the Seychelles Microcontinent Case Study

Abstract

Mantle plumes and surface erosion and sediment deposition affect the modes of continental lithospheric rupturing in extensional tectonic settings, modulating the evolution of rifting margins. However, their relative contributions to the overall evolution of rifting margins and possible roles in the formation of microcontinent are still elusive. Here, we use coupled geodynamic and surface processes numerical modeling to assess the extent to which surface processes may determine the formation of microcontinent during lithospheric stretching in presence or absence of a mantle plume underneath. Our modeling results indicate that fast extension rates and hillslope (i.e., diffusion) erosion promote ridge jump events and therefore the formation of microcontinents. On the contrary, efficient fluvial erosion and far-reaching sediment transport (i. e., stream power erosion) inhibits ridge jump events and the formation of microcontinents. The ridge jump event and overall evolution in our numerical models is consistent with the shift from the Mascarene Ridge to the Carlsberg Ridge that determined the formation of the Seychelles microcontinent. We therefore speculate that hillslope erosion, rather than fluvial erosion, was predominant during the formation of the Seychelles, a possible indication of overall dry local climate conditions.

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