Tectonic link between the Neoproterozoic dextral shear fabrics and Cenozoic extension structures of the Mekelle basin, Northern Ethiopia

Mekelle basin, with an area of ~5500 km2, is located at the immediate western margin of the Afar Depression that has experienced immense collision, subsidence, uplifting, magmatism and rifting. The evolution of such small to medium size basins in a complicated geodynamic set-up is still a debatable issue, because most of the mechanisms of basin formation could apply. To address the possible scenarios of the basin evolution, we combine structural and dynamic analyses of northern Ethiopia with great emphasis on the basin and basin bounding basement rocks. The north bounding block of the basin is uplifted by about 1500 m from the western and south-western basin-bounding blocks. Superposition of a great orthogonal brittle shear fabrics and development of young, parallel to sub-parallel extensional fractures, domino faulting, in the basin produce a total of ~2350 m vertical displacement. These observations, coupled with the absence of gradual rolling down of the crustal material (i.e., bending/folding by elastic beam that has been supported at the ends), imply that Mekelle basin is not an IntraCONtinental Sags (ICONS) or plate interior basin, as previously described, but is instead a multy-tectonic triggered basin. Integrated satellite imageries using ground-controlled measurement data and deep borehole data, deciphered the entire evolution of the basin starting from the late-tectonic deformation through the regional up-doming to the sills/dikes injection and basin formation.