Abstract
Continental rifting initiates the transition to breakup when the crust is necked and deformation localizes at the rift axis. However, the slow crustal-stretching rates and >20-km deep mantle beneath many active rifts worldwide suggest that present-day breakup may not be imminent. High-resolution seismic data from the Turkana Rift Zone of the East African Rift System (EARS) reveal the rift’s subsurface structure. Here, we show that Turkana’s crystalline crust has thinned to ~13 km along the rift axis, revealing an active rift undergoing crustal necking. Onset of necking is constrained to ~4 Ma and facilitated the accumulation of Turkana’s world-famous fossil record of human evolution. Identification of necking in the EARS indicates that eastern Africa is primed for continental breakup.
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Introduction
Tectonic plate divergence along continental rifts and the resulting breakup of stretching continents play an important role in shaping the Earth’s periodic dispersal cycles, the evolution of biota, landscapes, and climate throughout Earth history1,2. The process of rift maturation involves progressive crustal and lithospheric deformation that cascades through distinct phases3 from the stretching phase, to the necking phase, and oceanization. During the stretching phase, tectonic strain is distributed across rift-bounding (i.e., border) and intra-rift faults with minimal thinning of the crust3. The necking phase occurs when localized deformation along the rift axis enables efficient crustal thinning, reducing the crystalline crust to 15–10 km4,5. Oceanization occurs when extension is accommodated by magmatic accretion and mantle exhumation, marking the onset of seafloor spreading and complete breakup of the continental lithosphere6. Very few continental rifts are undergoing oceanization, among which are the Afar Rift7 and Red Sea8. In most active continental rifts, the modeled total strain rate9 derived from geodetic data is <65 × 10⁻⁹ yr⁻¹, excluding the Corinth Rift (Greece), which lies in the upper plate of a subduction system (Fig. 1a). These slow crustal-stretching rates, along with >20-km deep Mohorovičić discontinuity (Moho) (Fig. 1b, c), may suggest that the present-day active rifts across the world are predominantly in the stretching phase and that breakup may not be imminent.
a 2nd invariant of modeled strain rates for active continental rifts from ref. 9 (Supplementary Table 1). b Locations of boreholes in active and failed intracontinental rifts from ref. 59 used to extract crystalline crustal thickness and Moho depths from ref. 60 in (c, d). c Histogram of Moho depth sampled from boreholes in active intracontinental rifts. d Histogram of crystalline thickness from borehole locations in failed intracontinental rifts. e Map of eastern Africa (data from ref. 62) showing EARS faults (data from ref. 63), failed rifts (data from refs. 37,64,65), and modeled plate velocities (data from ref. 66). f Map of the Turkana Rift Zone (TRZ) showing seismic reflection survey grid used in this study and basins mapped using seismic reflection and gravity data (elevation data from ref. 61) (Supplementary Figs. 1 and 2). The location of (f) is shown as a black box in (e). g, h North-South elevation and Moho depth profiles of the EARS’ Eastern and Western Branches. Elevation data from ref. 62 and Moho data from ref. 34. The TRZ and the Afar Triangle (shaded blue) share similar rift-floor elevations and Moho depths. Profile locations are shown in (e).
The crystalline crust thickness across many failed intracontinental rifts worldwide is estimated to be >20 km (Fig. 1b–d), indicating that most ancient rifts that matured into the necking phase succeeded in breakup. Thus, of the three rift maturation phases, necking is the most significant as it accommodates the critical lithospheric weakening mechanism that initiates the transition to late-stage rifting and oceanization5,6,10. The existence of a necked crust, described as ‘necking domain’, was first identified and extensively studied within rifted margins—or “fossil rifts”11. However, the resolution of geophysical subsurface imaging at the deeply buried syn-rift sections of rifted margins is significantly degraded by signal attenuation, and exhumed outcrop analogs are rare. To date, no active continental rift has been identified as undergoing the necking phase, which has prevented empirical field study of the attendant geodynamics, surface processes, and landscape evolution peculiar to this critical phase of continental extension.
Here, we investigate the Turkana Rift Zone (TRZ) in Kenya, which hosts the shallowest Moho depth12 in the interior of the slowly-stretching East African Rift System (EARS) (Fig. 1e–h). We utilize high-resolution seismic reflection and borehole datasets to produce isopach maps of key horizons (Fig. 2, Supplementary Figs. 2–6). Combining these results with field observations reveals an actively necking continental rift. The rift zone is well-known for its low-elevation rift floor and shallow Moho12, similar to the Afar Triangle, which is in the most mature phase of EARS rifting and is undergoing incipient oceanization7. However, our reconstruction of the TRZ’s shallow crustal structure places constraints on its crystalline crustal thickness, which we demonstrate approaches those of the Afar13.
a Example of a high-quality seismic reflection profile used to map horizons and faults. The orange horizon marks the Gombe Series, which shows variable outcrop thicknesses24 of up to 100 m, whereas the blue horizon marks the top of the basement. The dashed black line in (b–d) indicates the profile location. b Bathymetry of Lake Turkana from ref. 67 and large-offset faults (black) mapped in this study using seismic reflection and gravity datasets. Gray faults mapped from hillshade imagery. c Gombe Series-to-surface regional isopach map in two-way traveltime (TWTT) seconds and surface outcrop locations24. The Gombe Series erupted ~4 Ma24. The inferred subsurface extent of the Gombe Series is based on outcrop stratigraphy20. d Basement-to-surface regional isopach map in TWTT seconds and surface outcrop locations68. Contour spacing is 300 ms and bolded every 5 contours in (c, d). Maps in (b–d) are displayed elevation data from ref. 61.
Results
The TRZ intersects two major rift systems—the NW-SE Mesozoic to early Cenozoic Central African Rift System (CARS) and the N-S Cenozoic EARS (Fig. 1e, Supplementary Fig. 1)—indicating at least two separate episodes of extension14. CARS rifting in the TRZ was largely amagmatic15 and persisted until ~57–45 Ma16. EARS-related faulting initiated in the TRZ at ~45–40 Ma, representing the earliest documented evidence of EARS rifting in eastern Africa17. Volcanism followed at ~37 Ma18, emplacing ~47,000 km³ of Eocene–Oligocene extrusive volcanic rocks19. Compared to CARS, EARS rifting in the TRZ is characterized by episodic, plume-derived volcanism extending through much of the Cenozoic18,20,21. Preceding the establishment of axial volcanism, the Stratoid Phase22 (~4–0.5 Ma) marks a shift to magmatism derived from decompression melting of the mantle23. The phase initiated with the basaltic eruption of the Gombe Stratoid Series22, which persisted for up to 300 thousand years24 (kyr). Our field and subsurface observations reveal previously unrecognized Mesozoic to early Cenozoic depocenters of the CARS, upon which EARS structures began to form in superposition shortly thereafter. We propose that structural and rheological inheritance from CARS rifting, coupled with the weakening effects of late Cenozoic magmatism, has driven premature necking of the TRZ, resulting in a rift development that is decoupled from the overall northward maturation trend of the EARS.
In continental rifted margins, the seismically imaged crustal architecture and associated deformational structures define rift domains in space4,11,25,26. These domains are linked to rift phases in time through the characteristic deformation mechanisms that produce the observed structures within each domain3,4,25,26. For example, the necking domain in rifted margins is primarily defined by a wedge-shaped crustal architecture, defined by the top of the crystalline crust and the Moho, in cross-sectional profile27,28 (Supplementary Fig. 7). In space, the necking domain forms during the necking phase in time as brittle and ductile deformation thins the crystalline crust from more than 15 km to 10 km4,5. In addition to geometry, thinning is quantified using the β factor, the ratio of initial, pre-rift crustal thickness to the current thickness at the rift axis29. In rifted margins, β greater than 1.5 characterizes the necking domain, whereas β values below 1.5 characterize the proximal domain, formed during the stretching phase of rifting26 (Supplementary Fig. 7).
Our depth-converted seismic reflection horizons (Supplementary Figs. 8 and 9) constrain the top of the crystalline basement, which we combined with published Moho depths12 to create a cross-sectional profile that reveals the crustal structure of the TRZ (Fig. 3) (Supplementary Information; Supplementary Data 1). Toward the rift axis, the TRZ’s crustal structure parallels that of the necking domain identified in rifted margins, thinning from over 35 km at the rift flanks to 12.7 ± 2.8 km at the rift axis, with β varying from 1.9 to 3.1 along the rift axis (Fig. 3, Supplementary Fig. 7). High β-values are co-located with modern seismicity30, indicating that present-day deformation is localized to the necked zone. This contrasts with off-axis regions exhibiting little to no present-day seismicity30. High-angle fault-bounded basins and β-values less than 1.5 characterize the crustal structure of the off-axis regions, mirroring the proximal domain of rifted margins25 (Supplementary Fig. 7). Thus, our profile indicates the presence of two distinct crustal architectures: (1) off-axis, low-β regions formed during the stretching phase but now abandoned, and (2) axial, high-β regions that continue to evolve through active necking.
a Map of the Turkana Rift Zone (TRZ) displaying the profile location and present-day seismicity. Earthquake data from ref. 30 and elevation data from ref. 61. CTC Congo-Tanzanian Craton, GB Gatome Basin, LT Lake Turkana, LR Lapur Range, LB Lotikipi Basin, MR Mogila Range, MuR Murua Rith Range, TB Turkana Basin. b Elevation profile from ref. 61 and local geological features. c Cross-sectional profile of the northern TRZ showing depth-converted basement and Gombe horizons from this study (Supplementary Data 1), Moho depths, and present-day earthquake frequency within 25 km of the profile. Moho depths from refs. 12,69 and earthquake data from ref. 30. The crustal structure is characterized by a wedge-shaped geometry formed by the top of the crystalline crust and Moho. Present-day seismicity is highest along the rift axis in the ‘necked zone.’ KRISP: Kenya Rift International Seismic Project69; NFC Necking Fault Complex. d β-factor and crustal thickness along the profile.
Conventional geodynamic models suggest that rift zones located farther from the rotation pole mature earlier due to higher plate velocities31. The TRZ, situated closer to the Nubia–Somalia Euler pole, experiences slower plate velocities than the Main Ethiopian Rift (MER)32. However, we argue that active necking in the TRZ indicates that the rift sector is transitioning to late-stage rifting south of the Afar Triangle (Fig. 1). Although both the Turkana and Main Ethiopian Rift sectors exhibit ongoing strain localization at their axes, estimates of thick crust beneath the latter suggest magmatic underplating33. Thus, we suggest that there is a distinction in the mechanics of crustal necking along-strike of the rift system that is compensated by magmatic underplating33 in the Main Ethiopian Rift sector. While other EARS rifts remain in the stretching phase with crustal thicknesses exceeding 25 km34, the TRZ’s evolution appears to have been accelerated by its unique geological history. We propose that the TRZ highlights how inherited lithospheric structure and past tectonic events can strongly influence rift development, challenging the traditional view of rift maturation governed primarily by plate kinematics.
Previous studies12,35 have dismissed or minimized the role of rift superposition, citing a lack of evidence for CARS-related structures in the TRZ. However, contrary to these interpretations, our outcrop and subsurface data indicate the existence of CARS rifting structures in the TRZ (Fig. 4a–d, Supplementary Figs. 10 and 11). Cretaceous-Paleogene strata of the Lapur Sandstone36, interpreted as CARS-related, are exposed within the uplifted footwall of the Lapur Fault in the Lapur Range northwest of Lake Turkana (Fig. 4c). These sandstones are overlain by EARS-related Eocene–Miocene volcanic flows of the Turkana Volcanics36 (Supplementary Fig. 11). Beneath the Lapur Sandstone, outcrop exposures reveal a previously undocumented unit of clast-supported, basement-derived conglomerates and breccias (Supplementary Figs. 10 and 11). In contrast to the well-rounded quartz-pebble conglomerates of the overlying Lapur Sandstone36, this basal unit comprises angular to sub-rounded basement clasts ranging from cobbles to boulders. The coarse clast size and disorganized bedding indicate deposition in proximal alluvial fan environments, whereas the Lapur Sandstone is interpreted as representing braided stream and distal alluvial fan deposits36. This implies exhumation of the crystalline basement along steep fault-bounded relief prior to emplacement of the Eocene flood basalts. These findings provide direct evidence of Cretaceous-age fault-related topography preserved in outcrop within the TRZ.
a, b Interpreted east-west seismic reflection profiles (locations in c). The deepest, poorly imaged seismic package thickens westward, interpreted as the Lapur Sandstone and conglomerates. This package is overlain by a package of high-amplitude reflectors that show minimal thickness variation in dip-section, interpreted as the Turkana Volcanics. c A simplified geologic map modified from refs. 70,71 of the northern Turkana Basin shows the locations of seismic reflection profiles and the restoration cross-section. Elevation data from ref. 61. d Interpreted south-north seismic reflection profile (location in c). Dashed horizons overlying interpreted faults (solid lines) indicate that the fault cuts the horizon in strike-view. e Restoration cross-section of depth-converted seismic horizons and amount of horizontal extension accounted for by the restoration (Supplementary Methods; Supplementary Figs. 12 and 13) (location in c). Tectonostratigraphic packages shown in (c). Cross-sections are in depth relative to the mean sea level and displayed with no vertical exaggeration. f, g Lapur Fault and Shore Fault System incremental extension and time-averaged extension rates calculated from cross-section restoration in (e) (Supplementary Methods; Supplementary Tables 2–4).
Seismic reflection profiles across the hanging wall of the Lapur Fault image strata varying in thickness beneath a poorly reflective, high-amplitude seismic package (Fig. 4a–d, Supplementary Figs. 4 and 5). We interpret these lower strata as correlatives of the Lapur Sandstone and underlying conglomerate, overlain by interbedded volcanics and sediments of the Turkana Volcanics (Supplementary Fig. 6; Supplementary Information). A basement depth map in two-way traveltime provides further evidence of CARS-related structures and depocenters within the Turkana Basin (Fig. 2), revealing NW-SE-trending basement displacement maxima aligned with previously mapped CARS faults15,37 (Fig. 1f). These basement lows coincide with a continuous low–shear wave velocity anomaly in the upper crust, interpreted by Kounoudis et al.38 as CARS-age sediments extending from the Sudan Rifts to the Anza Graben.
Our basement isopach map and crustal profile indicate that crustal necking is most pronounced where EARS structures overlap CARS depocenters, suggesting that rift maturation is most advanced in areas of pre-existing crustal thinning and weakening (Fig. 2d). We infer that EARS rifting in the TRZ exploited a thin, weakened lithosphere shaped by earlier CARS extension and pre-Cretaceous crustal thinning across northeastern Africa19. The short interval—less than 17 million years (Myr)—between the end of CARS rifting, the onset of EARS extension, and subsequent magmatism likely precluded lithospheric healing39 west of Lake Turkana and along the present-day rift axis. While other EARS segments, such as the Shire Rift40, also exhibit rift superposition, their prolonged hiatus between Mesozoic and Neogene extension contrasts with the rapid overprinting observed in the TRZ (Fig. 1e). Interestingly, the Anza Graben experienced CARS rifting15, yet shows limited EARS-related thermal alteration38. Sparse evidence of Miocene fault reactivation is preserved in well and seismic data in the northwestern Anza Graben15 (Supplementary Fig. 2), but the absence of significant Cenozoic magmatism21,22 may explain the muted EARS imprint relative to the Turkana Basin.
The EARS-related stretching phase of the TRZ began in the Eocene17 and persisted into the Miocene, with deformation distributed across a 200-km-wide zone along our crustal profile. Significant strain was accommodated by faults such as the Lokichar Fault (Fig. 2). Integrated with earlier subsurface interpretations (i.e., ref. 15) (Supplementary Fig. 2) and outcrop investigations20 east of Lake Turkana, our results show that rift-related sedimentation extended ~350 km, from the Lotikipi and Lokichar Basins to the northwestern Anza Graben15,41,42. Subsurface mapping reveals substantial displacement of the Gombe Series along the rift axis, with basalts absent in the Lokichar Basin43 but exposed east of Lake Turkana (Figs. 2 and 3). These observations indicate that strain localized shortly after the eruption of the Gombe Series, consistent with crustal-scale models showing strain migration toward the rift axis in the early Pliocene44,45. Based on this timing and the lithospheric thinning required for magma generation23, we infer that the TRZ transitioned from stretching to necking at ~4 Ma, shortly after the Miocene–Pliocene boundary (Fig. 5).
a Temporal range of the stretching and necking phase in the Turkana Rift Zone (TRZ) and Neogene magmatic pulses from refs. 21,22,23. The proposed onset of crustal necking corresponds to a change in melts derived from decompression melting23, strain localization along the rift axis (Fig. 2c), and higher sediment accumulation rates. b Schematic diagram of crustal structure evolution in the TRZ. Black-colored faults represent active faults; Gray-colored faults represent inactive faults; Yellow-colored basins represent active deposition; Gray-colored basins represent inactive basins. c Changes in sedimentary accumulation rates as proxied by outcrop sedimentary thickness (data from ref. 18), with black arrows showing change in slope and the red dashed line and shading showing the 4.58 Ma breakpoint and 95% CI (4.81–4.35 Ma). d Temporal distribution of the primary fossil-bearing strata for East Turkana, West Turkana, and the Omo. e Changes in large mammal community species richness. f Fossil records of apes and hominins, and archeological records from the TRZ. Data in (d–f) are available in Supplementary Table 5 and Supplementary Data 2.
Initiation of necking increased time-averaged extension rates along the Lapur and Shore Fault System (Fig. 4f, g), which defines the TRZ’s necking fault complex. This system of large-offset, low-angle faults accommodates several kilometers of extension and crustal thinning during active necking. The Lapur Fault, which exposes the basement in its footwall, maintains a relatively low dip of ~30° throughout the crust, into which the higher-angle Shore Fault System (45–60°) detaches as the faults link in the subsurface (Supplementary Fig. 12). Mechanical thinning along this complex resembles the recently proposed model of crustal thinning in necking domains driven by high-angle normal and detachment faults4. The TRZ’s necking fault complex also shares key characteristics with breakaway fault complexes imaged in rifted margin necking domains, which are composed of low-angle, oceanward-dipping, high-offset faults that facilitate substantial extension and expand both horizontal and vertical accommodation space, thereby increasing bulk accommodation5,26,46. Numerical models suggest such structures form via crustal-scale faults rooted in shear zones that penetrate the mantle, developing as strain localizes along the rift axis5,47.
Our restored profile yields a total of 15.4 km of upper-crustal extension based on fault-heave estimates (Supplementary Information; Supplementary Figs. 12 and 13), of which 7.1 km (46%) occurred since 4 Ma (Supplementary Information). Brittle faulting accounts for ~50% of the extension required to produce the deflection of the Moho, indicating that upper-crustal faulting cannot fully explain the inferred crustal thinning. Multiple episodes of basin inversion in the TRZ19,48 may have limited the preservation of fault heaves, leading to an underestimation of extension. Alternatively, lower-crustal flow and/or regional pre-Cenozoic thinning19 related to crustal delamination may account for a significant fraction of the Moho thinning. Strain localization on the necking fault complex nearly doubled rift-axis extension rates since ~4 Ma, with higher time-averaged rates along the Shore Fault System (1.2 mm/yr) than the Lapur Fault (0.55 mm/yr) (Fig. 4g). The Shore Fault System accommodated most of this Pliocene–Recent extension. However, the Lapur Fault shows increased activity on the youngest horizon, suggesting spatiotemporal strain partitioning within the necking fault complex. The substantial extension over the past 4 Myr increased bulk accommodation and drove deposition of the TRZ’s thick Plio–Pleistocene stratigraphy.
The Plio–Pleistocene strata of the TRZ preserve thousands of well-preserved fossil hominin and archeological remains, providing an unparalleled window for reconstructing human evolution49. The bulk of this record is concentrated in the Omo Group deposits50—comprised of three sequences in the northern (Shungura Formation), western (Nachukui Formation), and eastern (Koobi Fora Formation) segments of the TRZ—that provide an exceptionally rich, temporally continuous record of fossil hominins and their environmental context from ~4 to 1 Ma (Fig. 5d–f)51. However, the TRZ fossil record prior to 4 Ma is comparatively sparse and discontinuous, often intercalated with thick volcanic units, found in a few isolated outcrops (Fig. 5d)18,20 (Supplementary Data 2). Large mammal species richness (i.e., the number of species identified) is strongly correlated with how fossiliferous sedimentary deposits are52,53 and shows a marked shift towards higher values after ~4 Ma (Fig. 5e).
We propose that key differences in the TRZ’s fossil record before and after ~4 Ma reflect changes in depocenter characteristics driven by rift-phase processes (Fig. 5). Prior to 4 Ma, during the TRZ’s stretching phase, fossil-bearing deposits were stratigraphically discontinuous and geographically isolated (Fig. 5d). This reflects a rift dominated by distributed deformation and slip on isolated faults (Fig. 5b), which produced fragmented depocenters with accommodation space controlled by incremental slip on propagating faults54. While some faults eventually linked to form larger depocenters, these remained relatively small and accumulated sediment at lower rates than those of the later Omo Group sequence (Fig. 5c). By the early Pliocene (~4 Ma), outcrop stratigraphy reveals a marked increase in accumulation rates (Fig. 5c) and a transition to sedimentation within a large, integrated basin system20. This shift—driven by fault abandonment and localization of deformation toward the rift axis—marks the TRZ’s transition from the stretching to the necking phase (Fig. 5). The temporal coincidence between this tectonic transition and the onset of continuous, thick fossil-bearing strata suggests that the necking phase provided critical conditions for fossil preservation, including elevated accumulation rates and increased, localized accommodation space. We propose that these tectonic changes played a fundamental role in shaping the TRZ’s exceptional paleoanthropological record.
Our identification of the TRZ as an actively necking rift positions it as a natural laboratory for testing geodynamic models and refining interpretations of rifted margins. We show that its decoupled evolution from other EARS segments reflects inherited crustal structure and rheology, further amplified by magmatic weakening. These conditions have accelerated rift maturation, highlighting how pre-existing lithospheric properties and magmatism influence the timing and location of breakup. These findings constrain models of rift evolution, inform plate reconstructions, and have broad implications for understanding the dynamics of continental breakup.
Necking and oceanization domains exist in abandoned rift sectors of many rifted margins that underwent successful breakup11 but are absent in most intracontinental failed rifts (Fig. 1d). This suggests that once rifts enter the necking phase, they may progress toward breakup because necking both accelerates extension and weakens the crust5,55,56. In addition to early oceanization in Afar, this study documents active necking in the TRZ, suggesting that, despite slow extension rates, two segments of the EARS’ eastern branch have reached rift phases typically linked to successful breakup. Their emergence signals that the EARS has crossed a critical threshold, initiating geodynamic feedbacks that promote progression toward breakup6,56,57. We conclude that these observations indicate the EARS is now primed for continental breakup and provides a key setting for investigating rifting and breakup dynamics in magma-rich systems.
Data availability
The seismic reflection and borehole data that support the findings of this study are the property of the Kenyan Joint Venture (Tullow Oil, Meren Energy [formerly Africa Oil], and TotalEnergies), which were used under license for the current study. Depth-converted seismic horizons in Fig. 3 are available in Supplementary File 1. Isopach data files are available upon request. Fossil data and references compiled by this study are available in Supplementary File 2. The NOW—New and Old Worlds: Database of fossil mammals is publicly available for download from Zenodo58 (https://doi.org/10.5281/zenodo.4268068). The borehole locations in Fig. 1 are available for download from Zenodo59 (https://doi.org/10.5281/zenodo.11258453). Sedimentary thickness and Moho depths in Fig. 1b–d are available for download from Crust1.060 (https://igppweb.ucsd.edu/~gabi/crust1.html). Shuttle Radar Topography Mission data are available for download from Opentopography61 (https://doi.org/10.5069/G9445JDF). Elevation data in Fig. 1e and g are available for download from GEBCO62 (https://doi.org/10.5285/37c52e96-24ea-67ce-e063-7086abc05f29). Moho depths for eastern Africa34 are available at https://doi.org/10.1016/j.gr.2023.06.019. Moho depths for the Turkana Rift Zone12 are available at https://doi.org/10.1016/j.epsl.2023.118088. Earthquake data30 for the Turkana Rift Zone is available https://doi.org/10.1029/2023GC010982.
References
Smiley, T. M., Bahadori, A., Rasbury, E. T., Holt, W. E. & Badgley, C. Tectonic extension and paleoelevation influence mammalian diversity dynamics in the Basin and Range Province of western North America. Sci. Adv. https://doi.org/10.1126/sciadv.adn6842 (2024).
Brune, S., Williams, S. E. & Müller, R. D. Potential links between continental rifting, CO2 degassing and climate change through time. Nat. Geosci. 10, 941–946 (2017).
Lavier, L. L. & Manatschal, G. A mechanism to thin the continental lithosphere at magma-poor margins. Nature 440, 324–328 (2006).
Chenin, P. & Manatschal, G. Fingerprints of necking domains at rifted margins: A review of the best-documented examples worldwide. Earth Sci. Rev. https://doi.org/10.1016/j.earscirev.2025.105110 (2025).
Chenin, P., Schmalholz, S. M., Manatschal, G. & Karner, G. D. Necking of the lithosphere: a reappraisal of basic concepts with thermo-mechanical numerical modeling. J. Geophys. Res. Solid Earth 123, 5279–5299 (2018).
Brune, S. et al. Geodynamics of continental rift initiation and evolution. Nat. Rev. Earth Environ. 4, 235–253 (2023).
Bastow, I. D. & Keir, D. The protracted development of the continent–ocean transition in Afar. Nat. Geosci. 4, 248–250 (2011).
Ligi, M., Bonatti, E., Bosworth, W. & Ronca, S. Oceanization Starts at Depth During Continental Rupturing in the Northern Red Sea. In Geological Setting, Palaeoenvironment and Archaeology of the Red Sea (eds Rasul, N. M. A. & Stewart, I. C. F.) 131–157 (Springer International Publishing, 2019).
Kreemer, C., Blewitt, G. & Klein, E. C. A geodetic plate motion and Global Strain Rate Model. Geochem. Geophys. Geosyst. 15, 3849–3889 (2014).
Pérez-Gussinyé, M. et al. Towards a process-based understanding of rifted continental margins. Nat. Rev. Earth Environ. 4, 166–184 (2023).
Sapin, F., Ringenbach, J. C. & Clerc, C. Rifted margins classification and forcing parameters. Sci. Rep. 11, 8199 (2021).
Ogden, C. S. et al. The development of multiple phases of superposed rifting in the Turkana Depression, East Africa: Evidence from receiver functions. Earth Planet. Sci. Lett. 609, 118088 (2023).
Hammond, J. O. S. et al. The nature of the crust beneath the Afar triple junction: Evidence from receiver functions. Geochem. Geophys. Geosyst. https://doi.org/10.1029/2011gc003738 (2011).
Ebinger, C. J. & Ibrahim, A. Multiple episodes of rifting in Central and East Africa: a re-evaluation of gravity data. Geolog. Rundsch. https://doi.org/10.1007/bf00251068 (1994).
Morley, C. K. et al. Geology and geophysics of the Anza Graben. In Geoscience of Rift Systems—Evolution of East Africa Vol. 44 (ed. Morley, C. K.) 67–90 (American Association of Petroleum Geologists, 1999).
Agyemang, P. C. O., Roberts, E. M., Downie, B. & Sertich, J. J. W. Sedimentary provenance and maximum depositional age analysis of the Cretaceous? Lapur and Muruanachok sandstones (Turkana Grits), Turkana Basin, Kenya. Geol. Mag. 156, 1334–1356 (2019).
Boone, S. C. et al. Birth of the East African Rift System: nucleation of magmatism and strain in the Turkana Depression. Geology 47, 886–890 (2019).
Brown, F. H. & McDougall, I. Geochronology of the Turkana Depression of Northern Kenya and Southern Ethiopia. Evolut. Anthropol. Issues, N. Rev. 20, 217–227 (2011).
Morley, C. K. & Boone, S. C. Inception and evolution of the Turkana Depression: A review from the perspective of the longest-lived sector of the East African Rift. J. Afr. Earth Sci. 227, 105625 (2025).
Feibel, C. S. A geological history of the Turkana Basin. Evolut. Anthropol. Issues, N., Rev. 20, 206–216 (2011).
Rooney, T. O. The Cenozoic magmatism of East-Africa: Part I — flood basalts and pulsed magmatism. Lithos 286-287, 264–301 (2017).
Rooney, T. O. The Cenozoic magmatism of East Africa: Part II – rifting of the mobile belt. Lithos 360-361, 105291 (2020).
Cancel Vazquez, S. M. et al. Basaltic pulses and lithospheric thinning—Pliocene-Pleistocene magmatism and rifting in the Turkana Depression (East African Rift System). J. Geophys. Res. Solid Earth https://doi.org/10.1029/2024jb029166 (2024).
Haileab, B., Brown, F. H., McDougall, I. & Gathogo, P. N. Gombe Group basalts and initiation of Pliocene deposition in the Turkana depression, northern Kenya and southern Ethiopia. Geol. Mag. 141, 41–53 (2004).
Sutra, E., Manatschal, G., Mohn, G. & Unternehr, P. Quantification and restoration of extensional deformation along the Western Iberia and Newfoundland rifted margins. Geochem. Geophys. Geosyst. 14, 2575–2597 (2013).
Chenin, P., Manatschal, G., Ghienne, J. F. & Chao, P. The syn-rift tectono-stratigraphic record of rifted margins (Part II): a new model to break through the proximal/distal interpretation frontier. Basin Res. 34, 489–532 (2022).
Mohn, G., Manatschal, G., Müntener, O., Beltrando, M. & Masini, E. Unravelling the interaction between tectonic and sedimentary processes during lithospheric thinning in the Alpine Tethys margins. Int. J. Earth Sci. 99, 75–101 (2010).
Osmundsen, P. T. & Redfield, T. F. Crustal taper and topography at passive continental margins. Terra Nova 23, 349–361 (2011).
McKenzie, D. Some remarks on the development of sedimentary basins. Earth Planet. Sci. Lett. 40, 25–32 (1978).
Musila, M. et al. Active deformation constraints on the Nubia-Somalia Plate boundary through heterogenous lithosphere of the Turkana Depression. Geochem. Geophys. Geosyst. https://doi.org/10.1029/2023gc010982 (2023).
Martin, A. K. Propagating rifts: crustal extension during continental rifting. Tectonics 3, 611–617 (1984).
Calais, E., Ebinger, C., Hartnady, C. & Nocquet, J. M. Kinematics of the East African Rift from GPS and earthquake slip vector data. Geol. Soc. Lond. Spec. Publ. 259, 9–22 (2006).
Keir, D., Bastow, I. D., Corti, G., Mazzarini, F. & Rooney, T. O. The origin of along-rift variations in faulting and magmatism in the Ethiopian Rift. Tectonics 34, 464–477 (2015).
Baranov, A., Tenzer, R. & Eitel Kemgang Ghomsi, F. A new Moho map of the African continent from seismic, topographic, and tectonic data. Gondwana Res. 124, 218–245 (2023).
Boone, S. C. et al. Influence of rift superposition on lithospheric response to East African Rift system extension: Lapur Range, Turkana, Kenya. Tectonics 37, 182–207 (2018).
Tiercelin, J.-J. et al. Stratigraphy, sedimentology and diagenetic evolution of the Lapur Sandstone in northern Kenya: Implications for oil exploration of the Meso-Cenozoic Turkana depression. J. Afr. Earth Sci. 71-72, 43–79 (2012).
Morley, C. K., Ngenoh, D. K. & Ego, J. K. Introduction to the East African Rift System. In Geoscience of Rift Systems—Evolution of East Africa Vol. 44 (ed. Morley, C. K.) 1–18 (American Association of Petroleum Geologists, 1999).
Kounoudis, R. et al. The development of rifting and magmatism in the multiply rifted Turkana Depression, East Africa: evidence from surface-wave analysis of crustal and uppermost mantle structure. Earth Planet. Sci. Lett. 621, 118386 (2023).
Vanderhaeghe, O., Guergouz, C., Fabre, C., Duchêne, S. & Baratoux, D. Secular cooling and crystallization of partially molten Archaean continental crust over 1 Ga. C. R. Geosci. 351, 562–573 (2019).
Castaing, C. Post-Pan-African tectonic evolution of South Malawi in relation to the Karroo and recent East African rift systems. Tectonophysics 191, 55–73 (1991).
Wescott, W. A., Wigger, S. T., Stone, D. M. & Morley, C. K. Geology and geophysics of the Lotikipi Plain. In Geoscience of Rift Systems—Evolution of East Africa Vol. 44 (ed. Morley, C. K.) 55–65 (American Association of Petroleum Geologists, 1999).
Morley, C. K. et al. Geology and geophysics of the Western Turkana Basins, Kenya. In Geoscience of Rift Systems—Evolution of East Africa Vol. 44 (ed. Morley, C. K.) 19–54 (American Association of Petroleum Geologists, 1999).
Schofield, N. et al. Linking surface and subsurface volcanic stratigraphy in the Turkana Depression of the East African Rift system. J. Geol. Soc. 178, jgs2020–2110 (2021).
Corti, G. et al. Aborted propagation of the Ethiopian rift caused by linkage with the Kenyan rift. Nat. Commun. 10, 1309 (2019).
Brune, S., Corti, G. & Ranalli, G. Controls of inherited lithospheric heterogeneity on rift linkage: numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression. Tectonics 36, 1767–1786 (2017).
Osmundsen, P. T. & Péron-Pinvidic, G. Crustal-scale fault interaction at rifted margins and the formation of domain-bounding breakaway complexes: insights from offshore Norway. Tectonics 37, 935–964 (2018).
Naliboff, J. B., Buiter, S. J. H., Péron-Pinvidic, G., Osmundsen, P. T. & Tetreault, J. Complex fault interaction controls continental rifting. Nat. Commun. 8, 1179 (2017).
Morley, C. K., Harper, R. M. & Wigger, S. T. Tectonic inversion in East Africa. In Geoscience of Rift Systems—Evolution of East Africa Vol. 44 (ed C. K. Morley) 193–210 (American Association of Petroleum Geologists, 1999).
Wood, B. & Leakey, M. The Omo-Turkana Basin fossil hominins and their contribution to our understanding of human evolution in Africa. Evol. Anthropol. Issues N. Rev. 20, 264–292 (2011).
De Heinzelin, J. The Omo group: archives of the international Omo Research Expedition (Musee royal de l’Afrique centrale, 1983).
Harris, J. M., Brown, F. H., Leakey, M. G., Walker, A. C. & Leakey, R. E. Pliocene and Pleistocene hominid-bearing sites from west of Lake Turkana, Kenya. Science 239, 27–33 (1988).
Maxwell, S. J., Hopley, P. J., Upchurch, P. & Soligo, C. Sporadic sampling, not climatic forcing, drives observed early hominin diversity. Proc. Natl. Acad. Sci. USA. 115, 4891–4896 (2018).
Faith, J. T., Du, A. & Rowan, J. Addressing the effects of sampling on ecometric-based paleoenvironmental reconstructions. Palaeogeogr. Palaeoclimatol. Palaeoecol. 528, 175–185 (2019).
Withjack, M. O., Schlische, R. W. & Olsen, P. E. Rift-basin structure and its influence on sedimentary systems. In Sedimentation in Continental Rifts Vol. 73 (eds Renaut, R. W. & Ashley, G. M.) 57–81 (SEPM Society for Sedimentary Geology, 2002).
Brune, S., Popov, A. A. & Sobolev, S. V. Modeling suggests that oblique extension facilitates rifting and continental break-up. J. Geophys. Res. Solid Earth https://doi.org/10.1029/2011jb008860 (2012).
Brune, S., Williams, S. E., Butterworth, N. P. & Müller, R. D. Abrupt plate accelerations shape rifted continental margins. Nature 536, 201–204 (2016).
Ulvrova, M. M., Brune, S. & Williams, S. Breakup without borders: how continents speed up and slow down during rifting. Geophys. Res. Lett. 46, 1338–1347 (2019).
The NOW Community. NOW—new and old worlds database of fossil mammals. Zenodo https://doi.org/10.5281/zenodo.4268068 (2020).
Kolawole, F. & Jonathan, C. E. Data supporting global distribution of geothermal gradients in sedimentary basins [Data set]. In Geoscience Frontiers (Vol. 14, p. 101685). Zenodo. https://doi.org/10.5281/zenodo.11258453 (2024).
Laske, G., Masters, G., Ma, Z., & Pasyanos, M. Update on CRUST1.0—A 1-Degree Global Model of Earth's Crust. Geophys. Res. Abstr. 15, EGU2013-2658 (2013).
NASA Shuttle Radar Topography Mission (SRTM). Shuttle Radar Topography Mission (SRTM) Global. OpenTopography https://doi.org/10.5069/G9445JDF (2013).
GEBCO Bathymetric Compilation Group 2025. The GEBCO_2025 Grid - a continuous terrain model for oceansand land at 15 arc-second intervals. NERC EDS British Oceanographic Data Centre NOC. https://doi.org/10.5285/37c52e96-24ea-67ce-e063-7086abc05f29 (2025).
Macgregor, D. History of the development of the East African Rift System: a series of interpreted maps through time. J. Afr. Earth Sci. 101, 232–252 (2015).
Bosworth, W. Mesozoic and early Tertiary rift tectonics in East Africa. Tectonophysics 209, 115–137 (1992).
Daly, M. C., Chorowicz, J. & Fairhead, J. D. Rift basin evolution in Africa: the influence of reactivated steep basement shear zones. Geol. Soc. Lond. Spec. Publ. 44, 309–334 (1989).
Saria, E., Calais, E., Stamps, D. S., Delvaux, D. & Hartnady, C. J. H. Present-day kinematics of the East African Rift. J. Geophys. Res. Solid Earth 119, 3584–3600 (2014).
Johnson, T. C., Halfman, J. D., Rosendahl, B. R. & Lister, G. S. Climatic and tectonic effects on sedimentation in a rift-valley lake: evidence from high-resolution seismic profiles, Lake Turkana, Kenya. Geol. Soc. Am. Bull. 98, 439–447 (1987).
Institut français du pétrole. Bureau d'études industrielles et de coopération (Beicip). Geological map of Kenya with Bouguer Gravity Contours, Ministry of Energy and Regional Development of Kenya. https://sanweb.lib.msu.edu/maps/Scans/Kenya_Bouguer_1987_200.pdf (1987).
Mechie, J., Keller, G. R., Prodehl, C., Khan, M. A. & Gaciri, S. J. A model for the structure, composition and evolution of the Kenya rift. Tectonophysics 278, 95–119 (1997).
Key, R. & Watkins, R. Geology of the Sabarei area 793–834 https://cdn.prod.website-files.com/5cc7bd30669af234434d1dca/5d27a0b5cec96f521da885db_Key%20and%20Watkins.pdf (Republic of Kenya Ministry of Environment and Natural Resources, Mines and Geological Department Report, 1988).
Walsh, J. & Dodson, R. Geology of northern Turkana https://cdn.prod.website-files.com/5cc7bd30669af234434d1dca/5d27a14ccec96fb60ea8878e_Walsh_Dodson.pdf (Ministry of Natural Resources, Geological Survey of Kenya, Republic of Kenya, 1969).
Acknowledgements
We thank Tullow Oil, the Kenyan Joint Venture (Tullow Oil, Meren Energy [formerly Africa Oil], and TotalEnergies), and Kenya’s Ministry of Energy and Petroleum for granting access to data and permitting publication of this research. The views expressed are those of the authors and do not necessarily reflect those of the Kenyan Joint Venture. This work was supported by Meren Energy. We thank Craig Feibel for compiling and sharing outcrop sediment thicknesses and ages, and for valuable discussions. We are grateful to the Turkana Miocene Project for helpful discussions. We also thank Martha Withjack and Bob Raynolds for constructive comments. Tanner Acquisto is acknowledged for providing the MATLAB script used to convert seismic horizons to depth. We are deeply indebted to the late Richard Leakey and Isaiah Nengo (Turkana Basin Institute) for their support in securing funding and access to key datasets. We also thank Keith Hill and Paul Martinez for their support and instrumental role in facilitating access to geophysical data.
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C.M.R., F.K., and A.B. conceived the study. C.M.R. conducted the investigation, designed the figures, and wrote the original draft. F.K. and A.B. supervised the research. P.B. performed the cross-section reconstructions. J.R. assembled the fossil database and conducted the fossil analysis. C.M.R. and A.B. acquired funding. All authors reviewed and edited the manuscript.
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Rowan, C.M., Kolawole, F., Bécel, A. et al. Necking of the active Turkana Rift Zone and the priming of eastern Africa for continental breakup. Nat Commun 17, 3585 (2026). https://doi.org/10.1038/s41467-026-71663-x
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DOI: https://doi.org/10.1038/s41467-026-71663-x
