A review of tectonic models for the rifted margin of Afar: Implications for continental break-up and passive margin formation

Abstract

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Structural Analysis of the Western Afar Margin, East Africa: Evidence for Multiphase Rotational Rifting

“…Furthermore, in various places current fault activity occurs on or along the plateau, as well as along the antithetic faults (Figure 9a). Also, earthquake and well data from the Abala and Kobo area, respectively, clearly indicate recent antithetic fault activity (Figures 6c, 6d, and 8), which fits very well with the concept of ongoing marginal flexure (Abbate & Sagri, 1969; Kazmin et al, 1980; Wolfenden et al, 2005; Zwaan, Corti, Keir, & Sani, 2020). Well data also show marginal graben infill to be thin (<250 m, Figures 6c and 6d) and in spite of their impact on the landscape, marginal grabens and antithetic faults seem to form relatively small structures with respect to the large‐scale (synthetic) escarpment faults that clearly must have accommodated large amounts of displacement over time.…”

“…Terminology and toponymy in the area are often confusing since authors regularly use different names and spelling, due to changing political realities and the difficulties in translating local names in Latin script (Gouin, 1979; Williams, 2016). In this work, we follow and refine the marginal graben nomenclature established by Zwaan, Corti, Keir, & Sani (2020) (Figure 3b, see also the supplementary material: Zwaan, Corti, Sani, et al, 2020).…”

“…This is likely due to the basins being underfilled as confirmed by our borehole data from the Kobo graben, which forms the largest sedimentary basin along the WAM, revealing marginal graben infill of not more than a couple of hundred meters thick (Figures 6c and 6d, Zwaan, Corti, Sani, et al, 2020). The Buia graben with up to 500 m of sediments forms an exception, but is not a marginal graben sensu stricto since it forms continuation of the Danakil rift axis (Sani et al, 2017; Zwaan, Corti, Keir, & Sani, 2020, Figure 5a). Indeed, we observe various rivers that cross‐cut the margin, draining the marginal grabens and even eroding their limited sedimentary infill (Billi, 2015), so that instead of filling available accommodation space, material is directly transported to the main depocenter in Afar proper.…”

“…GoA: Gulf of Aden, MER: Main Ethiopian Rift, MS: Magmatic segments. Modified after Zwaan, Corti, Keir, & Sani (2020).…”

“…Historical accounts describe devastating earthquakes along the margin and as recent as 1961 a series of earthquakes with magnitudes up to 6.4 struck Korakore, causing significant damage in the area (Gouin, 1979, Figure 2a). The ongoing activity shows that WAM is not a true passive margin yet (Corti et al, 2015; Zwaan, Corti, Keir, & Sani, 2020).…”