Transition to magma-driven rifting in the South Turkana basin: Part I

Characterizing the role of magma in driving rift basin evolution is fundamental for understanding how extensional plate boundaries develop. Here, we examine patterns of normal faulting, volcanism, and magmatism in the South Turkana basin, Kenya, to test how magmatism has impacted the Quaternary evolution of this system. Utilizing high-resolution, single-channel reflection seismic data, and radiocarbon-dated cores, we estimate that shallow Holocene normal faulting accounts for 3.5-5.8 mm/yr of extension, consistent with estimates farther south in the Suguta Basin. Spatial fault patterns show that extension in the Holocene is concentrated along a ∼20 km-wide intra-rift fault network, aligning with the axial volcano, South Island. We suggest that up to 85% of Late Quaternary regional extension is accommodated within an axial magmatic segment, rather than on the border fault system responsible for the original basin architecture. Axial extension increases towards South Island, highlighting magmatism as critical for driving recent shallow upper crustal faulting in the South Turkana basin. Below this zone of extensional faulting, geochemical evidence supports a developed magma plumbing system that broadly parallels equivalent axial magmatic systems within the Main Ethiopian Rift. In all, our data support a recent (Middle-Late Pleistocene) transition to magma-driven axial extension in the Lake Turkana rift. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6026624