Inversion by Intrusion: Magma‐Driven Shortening in the Turkana Rift (East Africa)

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Abstract Late Pliocene to Pleistocene inversion in the Turkana Rift, observed on seismic reflection data and in outcrop, presents a tectonic paradox by indicating local shortening in an overall extensional setting. Previous studies attributed this inversion either to the reactivation of obliquely oriented structural weaknesses or to reorientation of the far‐field stress field. While both of these mechanisms would operate in a broad region, inversion in Turkana is confined to a narrow ∼50 km zone. Strikingly this zone appears to be bordered by two N‐S oriented zones of voluminous dike intrusion within the Northern and Southern segments of Lake Turkana. Here, we propose a causal relationship between inversion and localized dike intrusion. We first revisit the timing of inversion structures and magmatism in Turkana and second conduct geodynamic forward modeling that explicitly accounts for dike injection. The results demonstrate that dike emplacement at two parallel locations can generate sufficient shortening to trigger tectonic inversion in the intervening region, offering a mechanistic explanation for this enigmatic phase of deformation. Furthermore, the models suggest that faults actively respond to magmatic forcing, providing new insights into the interplay between magmatism and structural evolution in rift settings.

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