Evolution, distribution, and characteristics of rifting in southern Ethiopia

Abstract

Southern Ethiopia is a key region to understand the evolution of the East African rift system, since it is the area of interaction between the main Ethiopian rift (MER) and the Kenyan rift. However, geological data constraining rift evolution in this remote area are still relatively sparse. In this study the timing, distribution, and style of rifting in southern Ethiopia are constrained by new structural, geochronological, and geomorphological data. The border faults in the area are roughly parallel to preexisting basement fabrics and are progressively more oblique with respect to the regional Nubia-Somalia motion proceeding southward. Kinematic indicators along these faults are mainly dip slip, pointing to a progressive rotation of the computed direction of extension toward the south. Radiocarbon data indicate post 30 ka faulting at both western and eastern margins of the MER with limited axial deformation. Similarly, geomorphological data suggest recent fault activity along the western margins of the basins composing the Gofa Province and in the Chew Bahir basin. This supports that interaction between the MER and the Kenyan rift in southern Ethiopia occurs in a 200 km wide zone of ongoing deformation. Fault-related exhumation at~10-12 Ma in the Gofa Province, as constrained by new apatite fission track data, occurred later than the~20 Ma basement exhumation of the Chew Bahir basin, thus pointing to a northward propagation of the Kenyan rift-related extension in the area.

Geothermal potential and origin of natural thermal fluids in the northern Lake Abaya area, Main Ethiopian Rift, East Africa

“…1). Similar to other places along the EARS, the area shows significant recent and ongoing volcano-tectonic activity (Chernet, 2011;Corti et al, 2013;Philippon et al, 2014) and thermal emissions at the surface as springs and fumaroles (U.N. D.P., 1973;Craig et al, 1977;Chernet, 2011). The aim of the present study was to review the chemical and isotopic data of the thermal springs available in the literature, coupled with new data from field-work conducted in February 2015, during which freegas discharges and fumaroles, not previously analysed, were collected.…”

Control of Pre‐rift Lithospheric Structure on the Architecture and Evolution of Continental Rifts: Insights From the Main Ethiopian Rift, East Africa

“…The WFB volcano‐tectonic activity is developed close to the rift axis, and well expressed by the O'a caldera, now occupied by Lake Shala. Both the rift margins and the WFB are active in this rift sector and accommodate the recent‐current deformation in the area (e.g., Agostini, Bonini, Corti, Sani, & Manetti, ; Keir et al, ; Molin & Corti, ). Profile 5 illustrates the SMER north of Lake Abaya, which is an asymmetric structure characterized by a major fault escarpment on the eastern side (Agere Selam escarpment) and a faulted, riftward dipping monocline at the Soddo margin on the western side (e.g., Corti et al, ; Philippon et al, ). This latter margin is affected by numerous, closely spaced, small normal faults with associated widespread Pleistocene‐Holocene volcanism (Figure ).…”

Controls of inherited lithospheric heterogeneity on rift linkage: Numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression

“…[], and Philippon et al . []. AH: Amaro Horst; CB: Chew Bahir basin; HH: Hurri Hills; KS: Kino Sogo belt; LA: Lake Abaya; LT: Lake Turkana; LV: Lake Victoria; MV: Marsabit volcano; RR: Ririba Rift; SV: Suguta Valley; TE: Turkwell Escarpment.…”