The development of multiple phases of superposed rifting in the Turkana Depression, East Africa: Evidence from receiver functions

Ogden, C. S.; Bastow, I. D.; Ebinger, C. J.; Ayele, Atalay; Kounoudis, R.; Musila, M.; Bendick, Rebecca; Mariita, Nicholas; Kianji, G.; Rooney, Tyrone O.; Sullivan, G.; Kibret, Birhanu A.

doi:10.1016/j.epsl.2023.118088

Cited by 11 publications

(32 citation statements)

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“…Thus, we agree with the conclusions of Kounoudis et al (2021) that there is no evidence for a break in dynamic mantle support below the Turkana Depression. Recent crustal RF analysis of the Turkana Depression crust (Ogden et al, 2023), and associated isostatic mass balance calculations (assuming Airy isostasy) are also consistent with this hypothesis. Ogden et al (2023) reveal that Moho depths of 20-30 km across the Depression explain the region's low-lying nature compared to the adjacent plateaus to the north and south, with 550-645 m of mantle dynamic support required below the Depression.…”

Section: Mantle Transition Zone Discontinuity Structure Across East A...supporting

confidence: 53%

“…Ogden et al. (2023) reveal that Moho depths of 20–30 km across the Depression explain the region's low‐lying nature compared to the adjacent plateaus to the north and south, with 550–645 m of mantle dynamic support required below the Depression.…”

Section: Discussionmentioning

confidence: 99%

“…We also apply a crustal (Moho depth) correction using Crust1.0 (Laske et al, 2013), supplemented wherever possible by RF and wide-angle seismic constraints (Figures S13 and S14 in Supporting Information S1). To the earlier crustal model compiled by , we add data from numerous authors (Braile et al, 1994;Heit et al, 2015;Mechie et al, 1994;Ogden et al, 2023;Prodehl et al, 1994). Correcting a sign error in the implementation of the topographic and ellipticity travel-time corrections in renders delay times slightly earlier in this study, but also improves imaging of shallow mantle features beneath East Africa.…”

Section: New Absolute Arrival-time Datamentioning

confidence: 99%

“…Unfortunately, a historical paucity of seismograph stations has rendered it impossible to confidently resolve whole mantle wavespeed and mantle transition zone topography below this critical region, meaning plume‐flood basalt province correlations are difficult to substantiate. The Turkana Depression itself represents a geodynamical puzzle too: specifically whether it owes its low‐lying nature (∼500 m) to crustal thinning (e.g., Benoit, Nyblade, & Pasyanos, 2006; Ogden et al., 2023), or a lack of mantle dynamic support (e.g., Rogers et al., 2000). The extent to which the location of the failed, NW–SE‐trending Mesozoic‐age Anza rift was influenced by lithospheric heterogeneity and its connection to the Central African rift system in Sudan are also poorly constrained.…”

Section: Introductionmentioning

confidence: 99%

“…Their images show low wavespeeds throughout the Turkana Depression's upper mantle, implying there is no evidence for a break in dynamic support between the uplifted Ethiopia‐Yemen and East African plateaus. Instead, crustal RF analysis (Ogden et al., 2023) shows a 20–30 km‐deep Moho below the TRAILS network, implying that the region's low elevations can be explained adequately by crustal thinning alone. Shallower than 150 km depth, Kounoudis et al.…”

Section: Introductionmentioning

confidence: 99%

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Mantle Wavespeed and Discontinuity Structure Below East Africa: Implications for Cenozoic Hotspot Tectonism and the Development of the Turkana Depression

Boyce

Kounoudis

Bastow

et al. 2023

Geochem Geophys Geosyst

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Ethiopia's Cenozoic flood basalt magmatism, uplift, and rifting have been attributed to one or more mantle plumes. The Nubian plate, however, has drifted 500–1,000 km north since initial magmatism at ∼45 Ma, having developed above mantle that now underlies the northern Tanzania craton and the low‐lying Turkana Depression. Unfortunately, our knowledge of mantle wavespeed structure and mantle transition zone (MTZ) topography below these regions is poorest, due to a historical lack of seismograph stations. The same data gap means we lack constraints on lithospheric structure in and around the NW–SE trending Mesozoic Anza rift. We exploit data from new seismograph networks in the Turkana Depression and neighboring northern Uganda to develop AFRP22, a new African absolute P‐wavespeed tomographic model that resolves whole mantle structure along the entire East African rift system. We also map MTZ thickness using Ps receiver functions. East Africa's thinnest MTZ (∼25 km thinning) underlies the northwest Turkana Depression. AFRP22 reveals a co‐located, previously unrecognized, slow wavespeed plume tail, extending from the MTZ, deep into the lower mantle. This plume may thus have contributed, along with the African Superplume, to the development of the 45–30 Ma flood basalt province that preceded extension. Pervasive sub‐lithospheric slow wavespeeds imply that Turkana's present‐day low elevation is explained best by Mesozoic and Cenozoic‐age crustal thinning. At ∼100 km depth, AFRP22 illuminates a fast wavespeed SE Ethiopian plateau. In addition to governing the northernmost limit of Mesozoic Anza rifting, the refractory nature of this lithospheric block likely minimized Cenozoic flood basalt magmatism there.

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Section: Mantle Transition Zone Discontinuity Structure Across East A...supporting

confidence: 53%

Section: Discussionmentioning

confidence: 99%