1. Introduction
The topography of the African Plate is characterized by a basin-and-swell pattern (Burke, Reference Burke1996), widely interpreted as the surficial expression of Cenozoic mantle dynamics (e.g. Sengör, Reference Sengör2001; Moucha and Forte, Reference Moucha and Forte2011; Paul et al. Reference Paul, Roberts and White2014; Guillocheau et al. Reference Guillocheau, Simon, Baby, Bessin, Robin and Dauteuil2018). Although most of Africa has no mountain ranges as high as the Himalayas, Andes or Alps, a remarkably large portion of the continent stands at moderate elevations due to deep-seated mantle processes. The wavelengths of the topographic swells range from 200 to 2000 km (Figure 1a), and they are responsible for the large plateaus of Africa, such as the East African Plateau, whose mean elevation is ∼1000 m. The development of basin-and-swell structures since the Late Eocene (∼40 Ma) fundamentally modified Africa’s drainage network and drove the establishment of major river systems, including the Nile, Congo and Niger (Figure 1a) (e.g. Flügel et al. Reference Flügel, Eckardt and Cotterill2014; Chardon et al. Reference Chardon, Grimaud, Rouby, Beauvais and Christophoul2016; Sembroni et al. Reference Sembroni, Molin, Pazzaglia, Faccenna and Abebe2016b; Faccenna et al. Reference Faccenna, Glišović, Forte, Becker, Garzanti, Sembroni and Gvirtzman2019). Enhanced sediment flux to large deltas and adjacent deep-marine basins since the Oligocene attests to increased continental denudation and progressive surface uplift (e.g. Anka et al. Reference Anka, Séranne, Lopez, Scheck-Wenderoth and Savoye2009; Steinberg et al. Reference Steinberg, Gvirtzman, Folkman and Garfunkel2011; Macgregor, Reference Macgregor2012; Linol et al. Reference Linol, de Wit, Guillocheau, de Wit, Anka and Colin2015; Grimaud et al. Reference Grimaud, Rouby, Chardon and Beauvais2018; Torfstein and Steinberg, Reference Torfstein and Steinberg2020).
Figure 1. Regional topography, lithologic domains and tectonic framework of Afro-Arabia. (a) Distribution of lateritic cover across Africa, highlighting major Cenozoic domal swells (Afro-Arabian, East African and South African domes) and principal river systems (modified from Chardon (Reference Chardon2023)). (b) Simplified stratigraphic column of the Ethiopian-Yemen Plateau illustrating Oligocene continental flood basalts (∼30 Ma) overlying lateritic profiles and older sedimentary and Neoproterozoic basement units. (c) Major lithologic domains of northeast Africa and Arabia. The dashed outline delineates the extent of the Afro-Arabian dome. Also shown are the Oligocene-Miocene sediment transport pathways toward the Levant Basin: the Nile River system from the south (Fielding et al. Reference Fielding, Najman, Millar, Butterworth, Garzanti, Vezzoli, Barfod and Kneller2018) and the now extinct ‘Hazeva’ fluvial system from the southeast (Zilberman and Calvo, Reference Zilberman and Calvo2013; Morag et al. Reference Morag, Avigad, Gerdes and Abbo2021). Topography is from the GEBCO 2023 Grid DTM (GEBCO Compilation Group, 2023). BZOB, Bitlis-Zagros orogenic belt; DST, Dead Sea Transform.
A striking geomorphic expression of the epeirogeny that shaped Africa is the present undulating architecture of the ‘African Surface’ – a continent-wide etchplain formed under long-lived tropical weathering conditions during the Late Cretaceous to Late Eocene (∼70–40 Ma) and characterized by deep lateritic profiles and low-relief landscapes (Burke and Gunnell, Reference Burke and Gunnell2008 and references therein). This surface was subsequently warped, uplifted and dissected during the Cenozoic epeirogeny and is now found at elevations ranging from sea level to mountain tops exceeding 3000 m (Guillocheau et al. Reference Guillocheau, Simon, Baby, Bessin, Robin and Dauteuil2018).
One of the most prominent topographic swells associated with this evolution is the Afro-Arabian dome, a ∼4000-km-long and up to 1500-km-wide elevated region extending from Ethiopia in the south to the Eastern Mediterranean in the north (Figure 1a, c) (Almond, Reference Almond1986; Coleman, Reference Coleman1993; Burke, Reference Burke1996; Hofmann et al. Reference Hofmann, Courtillot, Feraud, Rochette, Yirgu, Ketefo and Pik1997; Bosworth, Reference Bosworth, Rasul and Stewart2015; Sembroni et al. Reference Sembroni, Faccenna, Becker and Molin2024). Present-day elevations decline from ∼2700 m on the Ethiopian and Yemen plateaux to ∼900 m in northern Arabia, reflecting the major phase of uplift that occurred since the Late Eocene. A hallmark of this swell is the preservation of extensive Oligocene truncation surfaces along its crest, long recognized as indicators of major regional uplift and widespread denudation (Avni et al. Reference Avni, Segev and Ginat2012; Sembroni et al. Reference Sembroni, Faccenna, Becker and Molin2024). Today, the dome is deeply dissected by the Red Sea Rift, whose Oligo-Miocene opening partitioned the swell and created pronounced rift-shoulder uplifts (Figure 1c).
From the Late Eocene onward, the rising Afro-Arabian dome was drained northwards into the Levant Basin of the Eastern Mediterranean by the ancestral Nile River system in NE Africa and by a coeval, smaller drainage network in Arabia (Figure 1c) (e.g. Avni et al. Reference Avni, Segev and Ginat2012). The resulting sediment flux produced an ∼3-km-thick siliciclastic section of Oligocene-Miocene age, which constitutes an exceptional archive of the uplift and denudation in Afro-Arabia (Gardosh et al. Reference Gardosh, Druckman, Buchbinder and Calvo2008; Steinberg et al. Reference Steinberg, Gvirtzman, Folkman and Garfunkel2011; Glazer et al. Reference Glazer, Avigad, Morag and Gerdes2023, Reference Glazer, Avigad and Morag2024).
Here, we utilize weathering geochemistry and clay mineralogy of Oligocene-Miocene siliciclastic sediments from the Levant Basin to reconstruct the uplift and denudation history around the Red Sea. By integrating proxies for chemical weathering intensity, sediment recycling and erosion patterns in both clay (<2 μm) and silt (<63 μm) fractions with independent geological constraints, we identify temporal variations in sediment sourcing and surface processes and link these changes to the spatial evolution of regional topography. This multi-proxy approach provides unique and independent constraints on the uplift history of the Afro-Arabian dome during the Oligocene and Miocene.
2. Geological background
2.a. Growth of the Afro-Arabian dome and Red Sea rifting
A range of geological, geomorphological and geophysical observations indicates that the Afro-Arabian topography is fundamentally linked to mantle dynamics. Seismic tomography reveals broad low-velocity anomalies beneath East Africa and Arabia, and dynamic topography models predict strongly positive residual topography coincident with the present swell (e.g. Chang and Van der Lee, Reference Chang and Van der Lee2011; Hansen et al. Reference Hansen, Nyblade and Benoit2012; Gvirtzman et al. Reference Gvirtzman, Faccenna and Becker2016; Emry et al. Reference Emry, Shen, Nyblade, Flinders and Bao2019). These patterns point to upwelling of the Afar mantle plume as the primary driver of regional doming beginning in the Late Eocene (Sembroni et al. Reference Sembroni, Faccenna, Becker and Molin2024 and references therein). Plume material likely spread laterally northwards during the Oligocene-Miocene, triggering widespread volcanism and promoting a transition from marine to continental conditions across much of the Arabian Plate (Ziegler, Reference Ziegler2001; Sembroni et al. Reference Sembroni, Faccenna, Becker and Molin2024).
The timing and magnitude of uplift above the Afar plume head centred in Ethiopia and Yemen (Figure 1a, c) have been constrained by thermochronology and topographic reconstructions (e.g. Pik et al. Reference Pik, Marty, Carignan and Lavé2003; Gani et al. Reference Gani, Gani and Abdel Salam2007; Boone et al. Reference Boone, McMillan, Balestrieri, Kohn, Gleadow, Alimanovic, Hutchinson, Noble, Mackintosh and Seiler2025; Sembroni et al. Reference Sembroni, Faccenna, Becker and Molin2024). Sembroni et al. (Reference Sembroni, Faccenna, Becker, Molin and Abebe2016a) proposed that a small dome first developed above the plume head in the Late Eocene (∼45–35 Ma), followed by substantial arching during or shortly after emplacement of the Ethiopian-Yemen continental flood basalts in the Early Oligocene (∼30 Ma). This domal uplift gave rise to the Ethiopian-Yemen Plateau (Figure 1a, c) and initiated northward drainage by the ancestral Nile River (Fielding et al. Reference Fielding, Najman, Millar, Butterworth, Garzanti, Vezzoli, Barfod and Kneller2018; Faccenna et al. Reference Faccenna, Glišović, Forte, Becker, Garzanti, Sembroni and Gvirtzman2019). Doming and uplift around the Red Sea, north of the Ethiopian-Yemen Plateau, debatably commenced in the Early Oligocene (∼34 Ma) but peaked in the Early Miocene (∼24–20 Ma) after the Red Sea Rift was initiated (Macgregor, Reference Macgregor2012; Boone et al. Reference Boone, McMillan, Balestrieri, Kohn, Gleadow, Alimanovic, Hutchinson, Noble, Mackintosh and Seiler2025; Sembroni et al. Reference Sembroni, Faccenna, Becker and Molin2024).
Superimposed on this plume-related topographic growth is the development of the Red Sea Rift, which initiated in the Late Oligocene (∼25 Ma), separating the African and Arabian plates (Figure 1c) (Bosworth et al. Reference Bosworth, Huchon and McClay2005). Thermochronological data show that rifting produced strong flexural uplift and exhumation along both rift flanks, leading to additional regional denudation and locally high relief (Boone et al. Reference Boone, McMillan, Balestrieri, Kohn, Gleadow, Alimanovic, Hutchinson, Noble, Mackintosh and Seiler2025; Sembroni et al. Reference Sembroni, Faccenna, Becker and Molin2024). The present-day topography of Afro-Arabia therefore reflects the combined effects of plume-driven doming and superimposed Red Sea rift-flank uplift. These combined uplift events created an extensive topographic gradient that routed sediments northwards toward the Eastern Mediterranean.
2.b. Lithologies exposed around the Red Sea
The lithologies exposed around the Red Sea (Figure 1c) (Bouysse, Reference Bouysse2010) exert a first-order control on the composition of sediments delivered to the Levant Basin during the Oligocene-Miocene. These lithologies fall into four main groups that were eroded as domal uplift and rift-flank uplift intensified.
2.b.1. Neoproterozoic Arabian-Nubian Shield basement
The Arabian-Nubian Shield (ANS) consists of juvenile Neoproterozoic crust formed during the assembly of the East African Orogen (∼870–570 Ma) (Stern, Reference Stern1994; Johnson and Woldehaimanot, Reference Johnson and Woldehaimanot2003; Johnson et al. Reference Johnson, Andresen, Collins, Fowler, Fritz, Ghebreab, Kusky and Stern2011). Its basement consists of island-arc metavolcanic and volcaniclastic successions, pelitic metasediments and extensive granodioritic intrusions emplaced at ∼870–740 Ma. These assemblages were subsequently amalgamated and intruded by widespread calc-alkaline syn- to late-collisional granitoids at ∼650–600 Ma, followed by post-collisional alkaline to peralkaline plutons and dike swarms between ∼610 and 570 Ma. Regional shear zones and ophiolitic fragments locally occur along tectonic boundaries. Overall, the ANS preserves a mosaic of juvenile lithologies with relatively uniform intermediate to felsic compositions (e.g. Stern, Reference Stern2002; Morag et al. Reference Morag, Avigad, Gerdes, Belousova and Harlavan2011a, Reference Morag, Avigad, Gerdes and Harlavan2012).
2.b.2. Palaeozoic-Mesozoic quartzose cover sequences
The pre-Red Sea Rift sedimentary cover overlying the ANS consists mainly of mature quartzose sandstones, siltstones and minor shales deposited in fluvial, deltaic and shallow-marine settings. Lower Palaeozoic sandstones (Cambrian-Ordovician) are typically very quartz-rich (Garfunkel, Reference Garfunkel2002; Avigad et al. Reference Avigad, Kolodner, McWilliams, Persing and Weissbrod2003, Reference Avigad, Sandler, Kolodner, Stern, McWilliams, Miller and Beyth2005). Overlying Mesozoic units include Triassic-Jurassic continental to marginal-marine clastics, Cretaceous fluvial-deltaic sandstones and localized carbonate intervals (e.g. Kolodner et al. Reference Kolodner, Avigad, Ireland and Garfunkel2009). These units are commonly horizontally bedded and form a laterally extensive siliciclastic blanket across both Arabia and Africa (e.g. Meinhold et al. Reference Meinhold, Morton and Avigad2013). Their mineralogy is dominated by quartz with subordinate feldspar and lithic fragments, reflecting transcontinental weathering and sediment recycling (Avigad et al. Reference Avigad, Sandler, Kolodner, Stern, McWilliams, Miller and Beyth2005; Kolodner et al. Reference Kolodner, Avigad, McWilliams, Wooden, Weissbrod and Feinstein2006; Morag et al. Reference Morag, Avigad, Gerdes, Belousova and Harlavan2011b; Critelli, Reference Critelli2018; Critelli et al. Reference Critelli, Perri, Arribas and Herrero2018; Meinhold et al. Reference Meinhold, Bassis, Hinderer, Lewin and Berndt2021).
2.b.3. Cenozoic volcanic provinces
Cenozoic volcanic rocks exposed around the Red Sea include the extensive Ethiopian and Yemen flood basalts, emplaced during the Early Oligocene (∼31–29 Ma) (Mohr, Reference Mohr1983; Baker et al. Reference Baker, Snee and Menzies1996; Hofmann et al. Reference Hofmann, Courtillot, Feraud, Rochette, Yirgu, Ketefo and Pik1997). These tholeiitic to transitional basalts form thick (hundreds of metres) plateau sequences, locally intruded by dolerite sills and dikes. Younger alkaline volcanic fields and shield volcanoes (Miocene-Quaternary) occur in both Ethiopia and along the Red Sea in Arabia, comprising basaltic lavas, rhyolites and pyroclastic deposits (e.g. Manetti et al. Reference Manetti, Capaldi, Chiesa, Civetta, Conticelli, Gasparon, La Volpe and Orsi1991). These volcanic provinces collectively record prolonged magmatism associated with Afar plume activity and the evolution of the Red Sea Rift (Bosworth et al. Reference Bosworth, Huchon and McClay2005; Bosworth and Stockli, Reference Bosworth and Stockli2016).
2.a.4 . Mature weathering profiles
Across both Arabia and NE Africa, mature weathering profiles, including developed saprolite and laterite horizons, locally cap the pre-Red Sea Rift succession. The weathering profiles are associated with four distinct planation surfaces of Early Palaeozoic, Mesozoic and Cenozoic age (e.g. Coltorti et al. Reference Coltorti, Dramis and Ollier2007, Reference Coltorti, Firuzabadi, Borri, Fantozzi and Pieruccini2015) and developed predominantly at the expense of Neoproterozoic crystalline basement of the ANS and its Mesozoic-Early Cenozoic sedimentary cover (Figure 1b) (e.g. Zanettin et al. Reference Zanettin, Bellieni and Visentin2006; Deller, Reference Deller2012 and references therein). Radiometric dating indicates that deep lateritic weathering and saprolite formation occurred during the Paleocene-Eocene (∼60–40 Ma), corresponding to the extensive ‘African Surface’ that developed across the continent (Schwarz and Germann, Reference Schwarz and Germann1995; Burke and Gunnell, Reference Burke and Gunnell2008; Deller, Reference Deller2012; Perelló et al. Reference Perelló, Brockway and García2020). This phase of intense chemical alteration was promoted by global greenhouse conditions during the Early Eocene Climatic Optimum (Zachos et al. Reference Zachos, Dickens and Zeebe2008) and by the equatorial to sub-equatorial position of the region at that time (Vrielynck and Bouysse, Reference Vrielynck and Bouysse2003). Wherever these saprolites and laterites were not protected beneath younger rock units, such as the thick Oligocene continental flood basalts of the Afar mantle plume (Figure 1b) (e.g. Overstreet et al. Reference Overstreet, DB, EF and GH1977; Drury et al. Reference Drury, Kelley, Berhe, Collier and Abraha1994; Baker et al. Reference Baker, Snee and Menzies1996), they were subsequently stripped off and now occur only as isolated remnants.
Together, these lithological components, juvenile Neoproterozoic basement, Palaeozoic-Mesozoic quartzose cover, Cenozoic volcanics and etchplain mantles, provide the raw materials that eroded and were redistributed as Afro-Arabia uplifted. Their differing erosion-weathering behaviours underpin the temporal evolution of mineralogical and geochemical signatures documented in this study.
2.c. Drainage reorganization and sediment transport into the Eastern Mediterranean
Uplift across Afro-Arabia reorganized regional drainage systems and established new sediment transport pathways that delivered large volumes of detritus to the Eastern Mediterranean (Figure 1c). The Levant Basin, a deep-marine basin approximately 300 × 175 km in size, with most of its area lying at water depths greater than 1000 m (Figure 2a), became the principal depocenter for sediments eroded from the rising dome. Although the basin originated during Early Mesozoic rifting associated with the opening of the southern Neotethys (Garfunkel, Reference Garfunkel2004 and references therein), its role as a major siliciclastic sediment sink intensified from the Late Eocene onward, when northward-flowing drainage systems began transporting voluminous detritus into the basin.
Figure 2. Location map and borehole stratigraphy of the study area. (a) Tectonic framework of the Levant region showing the Levant Basin and positions of the Myra, Dolphin, Leviathan and Karish North boreholes. (b) Simplified lithostratigraphic columns for the three boreholes (after Glazer et al. Reference Glazer, Avigad and Morag2024), showing the investigated Oligocene-Miocene siliciclastic section. Symbols denote sampling intervals, colour-coded by age. S.B., seabed; T.D., total depth.
The ∼3-km-thick Oligocene-Miocene siliciclastic section in the Levant Basin is composed of thick, clay-rich intervals with several discrete sandstone intercalations (Figure 2b). Provenance analyses of this stratigraphy, based on detrital zircon U-Pb-Hf isotopes, heavy mineral assemblages and Sr-Nd isotope compositions of the clay fraction, were recently carried out on four deep-sea boreholes: Myra, Dolphin, Leviathan and Karish North (Glazer et al. Reference Glazer, Avigad, Morag and Gerdes2023, Reference Glazer, Avigad and Morag2024). These studies show that the sand fraction was largely recycled from the quartz-rich Palaeozoic-Mesozoic siliciclastic cover sequences of NE Africa and Arabia. Sandstone intervals of the Lower Oligocene (34–28 Ma) and Lower Miocene (23–16 Ma) show a predominantly Arabian provenance, whereas NE Africa supplied most detritus during the Upper Oligocene (28–23 Ma), the base Miocene (∼23 Ma) and the Middle-Upper Miocene (16–7 Ma) (Glazer et al. Reference Glazer, Avigad, Morag and Gerdes2023). The fine-grained fraction, which volumetrically dominates the section, is sourced primarily from NE Africa. Sr-Nd isotopic compositions indicate derivation mainly from juvenile Neoproterozoic basement of the ANS, with a smaller contribution from Ethiopian flood basalts and recycled siliciclastic sediments (Glazer et al. Reference Glazer, Avigad and Morag2024). These studies also revealed that sedimentation patterns in the basin closely mirror the timing and magnitude of uplift across Afro-Arabia.
Collectively, these findings demonstrate that the Oligocene-Miocene fill of the Levant Basin records a dynamic interplay between NE African and Arabian sediment sources, modulated by plume-driven domal uplift, rift-flank uplift and evolving drainage networks across Afro-Arabia.
3. Materials and methods
3.a. Sampling
Samples for this study come from the National Rock Archive stored at the Geological Survey of Israel (GSI), with the approval of the Israel Ministry of Energy and the current right holders: Israel Ministry of Energy (Myra), NewMed Energy, Ratio Energies, and Chevron Mediterranean Limited (Leviathan) and Energean PLC (Karish North). Ten intervals were sampled from each borehole (Figure 2b, Table 1). Samples were created as composites by combining drill cuttings across 30 m intervals. Additionally, we studied one core sample of quartz-rich sandstone. The stratigraphic age of the different intervals is based on biostratigraphy and palynology performed independently by the operator of each well and given to us upon NDA. Ages for Leviathan samples were refined after Torfstein and Steinberg (Reference Torfstein and Steinberg2020). The complete sampling data are given in Supplementary Data 1. Drill cuttings were washed and sieved, leaving only >1 mm fragments for further clay separation. To evaluate and exclude possible contamination by drilling-mud constituents, we analysed the clay fraction (<2 μm) separated from the drilling mud used in the Leviathan borehole. The mud-derived clay fraction is dominated by barite and exhibits a distinctive geochemical fingerprint that is markedly different from the composition of our sediment samples (Supplementary Data 2). This uniqueness is further supported by its Sr-Nd isotope composition, which is unlike that of the studied sediments (Glazer et al. Reference Glazer, Avigad and Morag2024). Together, these observations demonstrate that drilling-mud components did not contribute measurably to the geochemical signatures of our samples.
Table 1. Mineralogy and geochemistry of Oligocene-Miocene clay fractions (<2 μm) from the Levant Basin
Kln, kaolinite; I/S, randomly interstratified illite-smectite mixed layers; Ill, illite; Chl, chlorite. Weathering indices CIA, CIX, WIP and αAl are defined in the methods section. *Stratigraphic ages are based on biostratigraphy and palynology performed independently by the operator of each well and given to us upon NDA. Ages for Leviathan samples were refined after Torfstein and Steinberg (Reference Torfstein and Steinberg2020). †‘recycled-sediment endmember’.
3.b. Clay fraction XRD analysis
The mineralogical composition of the clay (<2 μm) fraction in our samples was determined using XRD in the GSI XRD laboratory. Pristine rock fragments were gently disaggregated using a mortar and pestle, and the clay fraction was collected from suspensions settled according to Stokes Law after 1) carbonate minerals and salts dissolution by buffered acetic acid, and 2) disaggregation by a low-intensity ultrasonic treatment. Clay suspensions were concentrated and pipetted onto glass slides, then analysed after air-drying, glycolation, and heating to 550 °C for two hours. XRD patterns were acquired in Bragg-Brentano geometry with CuKα radiation using a PANalytical X’Pert3 diffractometer operated at 45 kV and 40 mA. Samples were scanned from 2 to 30° 2θ with a step size of 0.013° 2θ, using a Ni β-filter, ⅛° divergent slit, ¼° incident beam anti-scatter slit, ⅛° diffracted beam anti-scatter slit, and PIXcel detector in continuous scanning line (1D) mode with an active length of 1.01°. Clay mineral abundances were approximated semi-quantitatively from the glycolated samples relative peak areas of randomly interstratified illite-smectite (∼17 Å), illite (9.9 Å), and kaolinite and chlorite (7.1–7.2 Å, multiplied by the relative 3.57 and 3.52 Å peak area ratio for each mineral, respectively) (Biscaye, Reference Biscaye1965).
3.c. Clay fraction geochemistry
For geochemical analysis, about 100 mg of clay fraction from each sample was dissolved in a mixture of 10 ml Superpure© HF and 2 ml Superpure© concentrated HNO3 and evaporated at 190 °C in a designated Teflon beaker. Upon completion of evaporation, the remains were treated with 2 ml of Superpure© concentrated HCl and evaporated to dryness. Finally, 5 ml of Superpure© HNO3 was added and evaporated to dryness, and the remains were ultimately dissolved in 1N HNO3. Procedures were carried out in a laminated fume hood at the GSI. Major elements were determined using Perkin Elmer OPTIMA 3300 ICP-AES, and trace elements were determined by Perkin Elmer NexION 300D ICP-MS. The standard JSd-1 (Govindaraju, Reference Govindaraju1994) was used to control the accuracy of major and trace element concentrations. The analytical precision, as calculated from replicate analyses, is <3% RSD for major elements and <6% for trace elements.
Major and trace element composition is discussed with reference to the element concentration in the upper continental crust (UCC) following Rudnick et al. (Reference Rudnick, Gao, Holland and Turekian2003). REE data were normalized to chondritic meteorites following (Taylor and McLennan, Reference Taylor and McLennan1985). Eu anomalies (Eu*) are based on the geometric means of the adjacent elements [Eu* = Eu/(Sm*Gd)0.5].
3.d. Chemical indices of weathering
Chemical indices commonly used to estimate weathering patterns in sediments include the Chemical Index of Alteration [CIA = 100*Al2O3/(Al2O3 + (CaO − 3.33*P2O5) + Na2O + K2O)] (Nesbitt and Young, Reference Nesbitt and Young1982) and the Weathering Index of Parker [WIP = 100*((CaO − 3.33*P2O5)/0.7 + 2Na2O/0.35 + 2K2O/0.25 + MgO/0.9)] (Parker, Reference Parker1970), both calculated using molecular proportions of mobile alkali and alkaline-earth elements corrected for CaO in carbonates and phosphates. Rather than correcting the CIA for CaO, an approach that may introduce substantial error when mineralogical constraints are uncertain, the CIX index provides a simpler alternative by excluding CaO entirely [CIX = 100*Al2O3/(Al2O3 + Na2O + K2O] (Garzanti et al. Reference Garzanti, Padoan, Setti, López-Galindo and Villa2014a, Reference Garzanti, Vermeesch, Padoan, Resentini, Vezzoli and Andò2014b). The analysed clay fractions contain no carbonates or phosphates, so no Ca correction was required. For the silt-size geochemical data of Torfstein and Steinberg (Reference Torfstein and Steinberg2020), however, we corrected CaO using the Ca* = min(Ca, Na) approach following McLennan (Reference McLennan1993). In both datasets, CIA and CIX yield virtually identical results (R 2 = 0.91–0.99), yet we preferred the CIX for the silt fraction. Whereas the CIA and CIX measure the depletion in mobile alkali and alkaline-earth metals relative to immobile aluminium and are true indicators of weathering, the WIP measures the absolute concentration of these mobile elements and is strongly influenced by quartz dilution. We therefore use the CIA/WIP and CIX/WIP ratios to evaluate the importance of sediment recycling versus true weathering trends (Garzanti et al. Reference Garzanti, Padoan, Setti, Najman, Peruta and Villa2013b, Reference Garzanti, Padoan, Andò, Resentini, Vezzoli and Lustrino2013a). A more reliable way to quantify chemical weathering is to evaluate each mobile element separately by comparing its ratio to immobile Al in the sample with that of the UCC, expressed as αAlE = (Al/E)sample/(Al/E)UCC (Garzanti et al. Reference Garzanti, Padoan, Setti, Najman, Peruta and Villa2013b, Reference Garzanti, Padoan, Andò, Resentini, Vezzoli and Lustrino2013a). This approach modifies the original formulation of (Gaillardet et al. Reference Gaillardet, Dupré and Allègre1999) to eliminate biases introduced by hydraulic concentration of heavy minerals that host Ti, REE and Th.
4. Results
4.a. Clay mineralogy
All samples contain kaolinite, illite and randomly interstratified (R0-type) illite-smectite mixed layers in varying proportions (Figure 3a, Table 1). Chlorite is present but only in trace amounts. The clay mineralogy systematically varies with age in the investigated borehole sections. Oligocene sediments (34–23 Ma) at the bases of the Leviathan and Myra sections are dominated by kaolinite-rich assemblages, with kaolinite accounting for 74–86% (relative peak area). Illite-smectite mixed layers occur as minor to moderate components (5–21%), and illite as a trace to minor phase (4–13%). Kaolinite continues to predominate in the Lower Miocene (23–16 Ma) across all sections, reaching up to 77%, while illite becomes more abundant (5–49%). Toward the top of the Lower Miocene, illite-smectite mixed layers increase markedly at the expense of kaolinite, comprising up to 64% in Burdigalian-age samples. By the Middle to Upper Miocene (16–6 Ma), clay assemblages are dominated by illite-smectite mixed layers (up to 84%), whereas kaolinite declines substantially, averaging ∼25%, and illite stabilizes at ∼10%.
Figure 3. Clay and silt fractions mineralogical and geochemical ternary plots. (a) Clay fraction plotted in the illite-smectite – illite+chlorite – kaolinite ternary system. (b) Clay fraction plotted in the A-CN-K ternary system. (c) Silt fraction plotted in the A-CN-K ternary system (data from Torfstein and Steinberg (Reference Torfstein and Steinberg2020). Together, these plots illustrate a progressive shift from kaolinite-rich, high-CIA end-members toward illite-smectite-rich, low-CIA compositions, reflecting decreasing chemical weathering intensity during the Oligocene-Miocene. Lower Miocene samples show an increase in illite content, consistent with enhanced sediment recycling. Comparative data from Krom et al. (Reference Krom, Cliff, Eijsink, Herut and Chester1999); Sandler and Herut (Reference Sandler and Herut2000); Deller (Reference Deller2012); Garzanti et al. (Reference Garzanti, Andò, Padoan, Vezzoli and El Kammar2015).
4.b. Clay fraction geochemistry
4.b.1. Major, trace and rare earth elements
Major and trace element patterns of our samples are generally comparable (Figure 4a). They are mildly enriched with Th, U, Ti, Cr, Zn, Al and Pb, with respect to the average continental crust, and depleted in Na, K, Rb, Mg, Ca, Sr, Ba and Co. Rare earth element patterns of our samples are also comparable and are enriched with light rare earth elements with respect to chondrite (Figure 4b). Their La/Gd average at 5.2, Tb/Lu at 1.6 and Eu anomaly (Eu*) at 0.65. The complete geochemical data are given in Supplementary Data 2.
Figure 4. Major, trace and rare earth element compositions of clay-fraction samples from the Myra, Leviathan and Karish North boreholes. (a) Major and trace element content normalized according to the average upper continental crust composition of Rudnick et al. (Reference Rudnick, Gao, Holland and Turekian2003). (b) Rare earth elements content normalized according to the chondritic composition of Taylor and McLennan (Reference Taylor and McLennan1985). Together, these signatures indicate derivation from a predominantly felsic upper-crustal source, likely the Neoproterozoic Arabian-Nubian Shield. Comparative data from Kessel et al. (Reference Kessel, Stein and Navon1998); Moghazi et al. (Reference Moghazi, Andersen, Oweiss and El Bouseily1998); Pik et al. (Reference Pik, Deniel, Coulon, Yirgu and Marty1999); Eyal et al. (Reference Eyal, Litvinovsky, Katzir and Zanvilevich2004); Padoan et al. (Reference Padoan, Garzanti, Harlavan and Villa2011);Garzanti et al. (Reference Garzanti, Andò, Padoan, Vezzoli and El Kammar2015); El-Bialy and Omar (Reference El-Bialy and Omar2015); Fielding et al. (Reference Fielding, Najman, Millar, Butterworth, Ando, Padoan, Barfod and Kneller2017). ANS, Arabian-Nubian Shield; UCC, upper continental crust.
4.b.2. Sediment mobility sequence
The sediment mobility sequence consistently observed for clay fractions is: αAlCa (15–228) > αAlNa (3–51) > αAlSr (0.9–7) ≈ αAlMg (0.9–7) ≈ αAlK (0.9–5) ≈ αAlBa (0.5–5) ≈ αAlRb (1–7) (Table 1). The oldest sediments in the dataset (Oligocene; 31–24 Ma) display the highest degrees of mobile-element depletion relative to the UCC (Figure 5a). αAlNa values reach their maximum in this interval (∼26–51), indicating extreme Na mobility. Calcium is likewise strongly depleted, with αAlCa consistently high (∼110–220). Sr and Mg also show enhanced depletion in these oldest samples, with αAlSr up to ∼6.5 and αAlMg reaching ∼6–7. K and Ba exhibit moderate depletion (αAlK ∼2–5; αAlBa ∼1.6–5.4), while Rb becomes increasingly enriched relative to Al, with αAlRb values up to ∼7.4. During the Early to Middle Miocene (23–16 Ma), αAl values remain elevated but are generally lower and more variable than in the Oligocene (Figure 5a). Na depletion stays pronounced (αAlNa ∼9–20), whereas Ca continues to show strong but fluctuating depletion (αAlCa ∼90–170). Sr and Mg exhibit moderate depletion (αAlSr ∼1.3–5.8; αAlMg ∼2–5), and K maintains values of ∼2.4–3.8. Ba and Rb show considerable scatter but tend to remain within the range of ∼1–5 and ∼1–6, respectively. The youngest sediments (Middle to Upper Miocene; 16–5 Ma) show the lowest degrees of depletion overall (Figure 5a). αAlNa values decrease markedly to ∼3–9, and Ca becomes less variable, though still depleted (αAlCa ∼15–70). Sr and Mg display mild depletion (αAlSr ∼1–3; αAlMg ∼1–2), while K remains consistently low to moderate (αAlK ∼1.5–3). Ba is mostly near or below unity in this interval, and Rb shows modest values (αAlRb ∼1.7–3).
Figure 5. αAl-normalized element ratios for the clay (a) and silt (b) fractions plotted against sample age, showing differential depletion in alkali and alkaline-earth metals (silt-fraction data calculated after Torfstein and Steinberg (Reference Torfstein and Steinberg2020). Oligocene sediments exhibit a strong depletion in mobile elements, indicating intense weathering of the source rocks. A shift toward less depleted compositions during the Miocene indicates a reduction in chemical weathering intensity and an increasing contribution from less-altered source material.
4.b.3 . Weathering indices
Oligocene sediments (31–24 Ma) show the strongest chemical alteration in the dataset (Figures 3b, 6a, Table 1). CIA values range from ∼91 to 95, with CIX values closely matching them. WIP values are consistently low (∼17–25), including the minimum values observed in the entire sequence. Lower Miocene sediments (23–16 Ma) display a modest reduction in weathering intensity relative to the Oligocene (Figures 3b, 6a, Table 1). CIA and CIX values range from ∼86–93, while WIP increases to ∼22–32. In contrast, Middle to Upper Miocene sediments (16–5 Ma) show the lowest CIA and CIX values of the entire record (∼85–90), coincident with relatively high WIP values (∼26–38). The highest WIP values occur in the youngest samples (6–5 Ma), where CIA/CIX simultaneously reach their minimum (Figures 3b, 6a, Table 1).
Figure 6. Temporal evolution of sedimentary, geochemical and isotopic indicators for the clay (a) and silt (b) fractions, including weathering indices and sediment-recycling proxies (silt-fraction data calculated after Torfstein and Steinberg (Reference Torfstein and Steinberg2020). Oligocene sediments record intense chemical weathering, expressed by high CIA/CIX values, low WIP and low CaO+Na2O/Al2O3 ratios. Through the Miocene, the record shows a gradual shift toward less-weathered compositions. The Early Miocene is marked by elevated recycling indicators, reflecting increased incorporation of quartz-rich material. Shaded intervals highlight the period of enhanced sediment recycling. ϵNd data from Glazer et al. (Reference Glazer, Avigad and Morag2024).
4.c. Silt fraction geochemistry
Geochemical data for the silt fraction (<63 µm) are based on the major-element compositions reported by Torfstein and Steinberg (Reference Torfstein and Steinberg2020). From these data, we calculated αAl element-mobility ratios and weathering indices, allowing direct comparison with our clay-fraction results and evaluation of chemical alteration trends versus recycling across grain-size populations.
4.c.1 . Sediment mobility sequence
The bulk-sediment mobility sequence consistently observed for silt fractions is: αAlNa (3-18) > αAlK (2–5) > αAlMg (0.5–3) (Table 2). Oligocene sediments (33–24 Ma) display the highest degrees of Na depletion and moderately elevated Mg and K depletion relative to the UCC reference (Figure 5b, Table 2). αAlNa values are extremely high in this interval (∼9–18). αAlMg shows moderate depletion (∼1.7–2.5), while αAlK ranges from ∼2.5 to 3.8, with the highest K depletion also occurring in the oldest samples. Lower Miocene sediments (23–16 Ma) continue to show substantial chemical depletion, but with different mobility signatures compared to the Oligocene (Figure 5b, Table 2). αAlNa values remain high but more variable (∼5.6–13.4). αAlMg increases relative to the Oligocene (∼1.7–2.5). αAlK values range from ∼2.6 to 3.8, similar to the Oligocene but with fewer extremely depleted samples. In contrast, Middle to Upper Miocene sediments (16–6 Ma) record substantially lower depletion of Na, Mg and K (Figure 5b, Table 2). αAlNa decreases to ∼3–10, with the lowest values (∼2.8–4.1) found in the youngest samples (9–6 Ma). αAlMg shows the weakest depletion of the entire record (∼0.5–1.3), while αAlK likewise declines to ∼1.6–3.1.
Table 2. Geochemistry of Oligocene-Miocene silt fractions (<63 μm) from the Leviathan borehole
Weathering indices CIA, CIX, WIP and αAl are defined in the methods section and were calculated based on the geochemical analysis of Torfstein and Steinberg (Reference Torfstein and Steinberg2020). Stratigraphic ages were likewise adopted from Torfstein and Steinberg (Reference Torfstein and Steinberg2020).
4.c.2. Weathering indices
Oligocene sediments (33–24 Ma) display the highest overall weathering intensities in the silt-size fraction (Figures 3c, 6b, Table 2). CIA values are consistently elevated (∼88–91) with CIX values closely matching them. WIP values, in contrast, are relatively low (∼10–15). Lower Miocene sediments (23–16 Ma) exhibit moderately high CIA and CIX values but show a noticeable decline compared to the Oligocene (Figures 3c, 6b, Table 2). CIA ranges from ∼82–92, while CIX spans ∼86–94. WIP values during this interval increase slightly relative to the Oligocene (∼13–18). By contrast, Middle to Upper Miocene sediments (16–6 Ma) record the lowest chemical alteration in the silt fraction (Figures 3c, 6b, Table 2). CIA values decrease to ∼77–87, and CIX ranges from ∼83–90. WIP values are substantially higher than in older sediments, ranging from ∼13–24, with the highest values (∼20–24) occurring in the youngest samples (∼9–6 Ma).
5. Discussion of geochemical and mineralogical results
5.a. Geochemical perspective on the provenance of the Oligocene-Miocene clay
The major-, trace- and rare earth element characteristics of the Oligocene-Miocene clay assemblages provide robust constraints on their provenance. Previous Sr-Nd isotope analyses (Glazer et al. Reference Glazer, Avigad and Morag2024) indicated that the clay was derived largely from juvenile Neoproterozoic ANS basement, with a possible but uncertain contribution from Tertiary continental flood basalts of the Ethiopian Plateau. The isotopic data also show that Lower Miocene sediments contain a detectable component of recycled older material; however, this contribution was limited and did not substantially modify the dominant ANS signature.
In the multi-element diagrams (Figure 4a), the clay samples plot along the trend defined by sediments derived from ANS basement rocks (red field) and diverge markedly from the pattern characteristic of continental flood basalts (grey field). Notably, the clays do not show the strong enrichments in Ti, Cr, Fe, Co, Ni and Cu that typify basalt-derived sediments (Padoan et al. Reference Padoan, Garzanti, Harlavan and Villa2011; Garzanti et al. Reference Garzanti, Andò, Padoan, Vezzoli and El Kammar2015). Instead, their elemental distributions are relatively flat, consistent with derivation from felsic basement lithologies rather than mafic volcanic sources. The REE pattern (Figure 4b) further reinforces this interpretation. The clay fractions display REE patterns with La/Gd ≈ 5.2, Tb/Lu ≈ 1.6, and a distinct negative Eu anomaly (Eu* ≈ 0.65), a combination that closely matches the REE characteristics of ANS basement. In contrast, Ethiopian Plateau flood basalts show much lower La/Gd (∼2.7), higher Tb/Lu (∼2.3), and no Eu anomaly (Eu* ≈ 1) (Pik et al. Reference Pik, Deniel, Coulon, Yirgu and Marty1999). The close correspondence between the clay REE profiles and the ANS basement reference, together with their clear divergence from the basalt signature, demonstrates that the basaltic contribution must have been minor. Taken together, the Sr-Nd isotope evidence and the major-, trace- and REE-element data converge on the same conclusion: the Oligocene-Miocene clays of the Levant Basin were sourced predominantly from Neoproterozoic ANS basement, with only a limited input from Ethiopian Plateau flood basalts and recycled siliciclastic sediments. This interpretation is consistent with earlier provenance estimates from the Nile Delta, where the basaltic component in coeval sediments is likewise inferred to be modest (∼10–45%; Fielding et al. Reference Fielding, Najman, Millar, Butterworth, Garzanti, Vezzoli, Barfod and Kneller2018).
At the Ethiopian Plateau, the headwaters of the Nile, Neoproterozoic basement rocks are largely overlain by Mesozoic sediments and extensive continental flood basalts (Figure 1b–c) (Ismail and Abdelsalam, Reference Ismail and Abdelsalam2012). Although incision of the Blue Nile and Tekeze canyons (Figure 1c) began in the Early Oligocene (Pik et al. Reference Pik, Marty, Carignan and Lavé2003) and a fluvial connection with the Eastern Mediterranean was established at approximately the same time (Fielding et al. Reference Fielding, Najman, Millar, Butterworth, Garzanti, Vezzoli, Barfod and Kneller2018; Faccenna et al. Reference Faccenna, Glišović, Forte, Becker, Garzanti, Sembroni and Gvirtzman2019), the Ethiopian Plateau was unlikely to have supplied significant volumes of siliciclastic sediment to the Eastern Mediterranean during most of the Oligocene-Miocene. Instead, the Red Sea margins north of the Ethiopian Plateau are inferred to have been the dominant sediment source to the Eastern Mediterranean, including the Levant Basin, consistent with the model of Macgregor (Reference Macgregor2012). The Ethiopian Plateau likely became a major contributor to Eastern Mediterranean sedimentation only in the Late Miocene, following rapid uplift and deep fluvial incision by the Blue Nile and Tekeze drainage systems (Gani et al. Reference Gani, Gani and Abdel Salam2007; Gani, Reference Gani2015; Bowden et al. Reference Bowden, Gani, Furman, Gani, Vansoest, Abebe, Alemu, Sullivan and Tadesse2022).
5.b. Weathering patterns reflected in the Oligocene-Miocene sediments
Deposition of the Oligocene-Miocene siliciclastic section in the Levant Basin is closely linked to the growth of the Afro-Arabian dome and the associated topographic evolution of Afro-Arabia (Glazer et al. Reference Glazer, Avigad, Morag and Gerdes2023, Reference Glazer, Avigad and Morag2024). The clay mineralogy and geochemistry, together with the silt-fraction geochemical data, illuminate the weathering and erosional regimes that prevailed across Afro-Arabia before and during this major phase of uplift and sediment delivery to the basin.
Oligocene sediments (33–24 Ma) record the strongest chemical weathering signals in both clay and silt fractions. Clay assemblages are overwhelmingly kaolinite-rich (up to ∼85%), indicating deeply weathered source terrains. The clay CIA and CIX values exceed 90, WIP reaches its absolute minimum (∼17–25), and αAl values show the greatest depletions of Na, Ca, Sr and Mg (Figures 5a–6a). The silt fraction also mirrors this trend: CIA and CIX are similarly high (∼88–91; 90–93), WIP is low (∼10–15) and αAlNa, αAlMg and αAlK record the most pronounced alkali and alkaline-earth loss (αAlNa commonly >10 and up to ∼18) (Figures 5b–6b). A-CN-K and clay mineralogy ternary diagrams further support this interpretation: Oligocene samples cluster close to the Al2O3 and kaolinite poles (Figure 3a–c), demonstrating a mature mineralogical and geochemical signature, typical of intensely weathered profiles. These parallel trends in both grain-size fractions indicate intensively weathered source rocks for the Oligocene sediments.
Lower Miocene sediments (23–16 Ma) reflect more moderate, but still significant chemical weathering, with a clear reduction relative to the Oligocene. Kaolinite remains abundant in the clays (up to ∼77%), but the proportions of illite and illite-smectite increase, suggesting either diminished chemical weathering intensity or enhanced stripping of less deeply weathered rocks. Geochemical indices support this transitional character: clay CIA/CIX remain high but begin to decline (∼86–93), while WIP increases to ∼22–32 (Figure 6a). αAl depletion becomes less extreme across most elements (Figure 5a). The silt fraction shows the same pattern: CIA and CIX remain elevated but lower than the Oligocene (∼82–92; 86–94), and WIP rises to ∼13–18 (Figure 6b). αAlNa and αAlMg are still indicative of substantial chemical mobility but show clear decreases compared to older silt (Figure 5b). The ternary diagrams show a corresponding shift: in the clay mineralogy ternary diagram (Figure 3a), Lower Miocene clays move away from the kaolinite apex toward the illite-smectite side of the triangle, indicating a reduction in weathering intensity. In the A-CN-K ternary diagrams (Figure 3b–c), Lower Miocene samples move along the ideal weathering trend toward Ca- and Na-rich UCC values. This combined record points to persistent but weakening source-rock weathering. Moreover, Lower Miocene sediments show several signs of enhanced sediment recycling, most notably higher illite and K2O contents and sharply increasing CIA/WIP ratios, which are examined in detail in Section 5.c.
Middle to Upper Miocene sediments (16–5 Ma) exhibit the weakest weathering signatures in both clay and silt fractions, marking a shift toward physically dominated erosion. Clay assemblages are dominated by illite-smectite (up to 84%), while kaolinite drops markedly, indicating erosion of fresher, less weathered bedrock. Clay CIA/CIX values reach their lowest range (∼85–90), and WIP reaches its highest (∼26–38) (Figure 6a). Clay αAl patterns confirm this trend, with minimal depletion of Na, Mg, K and Sr, signalling more direct erosion of unweathered bedrock (Figure 5a). The silt fraction behaves similarly: CIA and CIX fall to ∼77–87 and ∼83–90, respectively, while WIP increases to ∼20–24, the highest values in the entire record (Figure 6b). αAlNa, αAlMg and αAlK reach their minimum depletions, showing only weak chemical modification of source material (Figure 5b). The ternary diagrams highlight this transition clearly: Middle to Upper Miocene clays shift strongly toward the illite-smectite apex (Figure 3a), and in the A-CN-K ternary diagram (Figure 3b), samples move opposite to the ideal weathering trend toward the CaO+Na2O pole, indicating higher contributions of less weathered detritus. For the silt fraction, the A-CN-K ternary diagram (Figure 3c) shows an even more pronounced pull toward the CaO+Na2O pole, reflecting plagioclase-rich and less altered detritus, indicating increased physical erosion. These patterns reflect a major shift from intensely weathered source rocks to more abundant physical erosion of fresh bedrock.
5.c. Sediment recycling reflected in the Oligocene-Miocene sediments
Sediment recycling refers to the reworking and redeposition of previously lithified sediments, widespread as quartz-rich sandstones across NE Africa and Arabia, into younger clastic sequences. This process introduces quartz-rich material that formed during earlier weathering-erosion cycles, including a clay fraction characterized by evolved Nd isotopic compositions (Ben Dor et al. Reference Ben Dor, Harlavan and Avigad2018). To identify sediment recycling within the studied clay fraction, we analysed clay extracted directly from the core of a quartz-rich sandstone, which we treat as a ‘recycled-sediment endmember’. In addition to its evolved Nd isotopic signature (ϵNd ≈ −12; Glazer et al. Reference Glazer, Avigad and Morag2024), this material is characterized by elevated K2O contents, abundant illite and lower CIA values (∼75; Figure 6a, Table 1).
Lower Miocene clay fractions show a slight shift toward the composition of the recycled-sediment end-member, indicating a modest but detectable contribution from reworked material (Figures 3a–b, 6a). However, their overall compositions remain far removed from that end-member, demonstrating that primary chemical weathering of ANS basement rocks still dominated the clay signal during this interval. A parallel shift toward the K2O apex is observed in the silt fraction as well (Figure 3c). Taken together, these trends are fully consistent with sandstone petrography, detrital zircon U-Pb geochronology and Sr-Nd isotopes, which independently indicate enhanced sediment recycling during the Early Miocene (Glazer et al. Reference Glazer, Avigad, Morag and Gerdes2023, Reference Glazer, Avigad and Morag2024).
Evaluating the relative importance of sediment recycling versus chemical weathering is best achieved by examining temporal changes in the CIA/WIP and CIX/WIP ratios. Because these ratios increase much more rapidly through quartz dilution than through genuine weathering, they provide an effective means of distinguishing the influence of sediment recycling in sediments of mixed provenance (Garzanti et al. Reference Garzanti, Padoan, Setti, Najman, Peruta and Villa2013b, Reference Garzanti, Padoan, Andò, Resentini, Vezzoli and Lustrino2013a).
On the CIA/CIX-WIP diagram (Figure 7a), clay fractions follow a typical UCC-like weathering trajectory: Oligocene samples occupy the most weathered field, whereas Upper Miocene samples plot in the least weathered position. Importantly, none of the clay fractions approaches the CIA/WIP values of the ‘recycled-sediment endmember’, indicating minimal recycling influence in the clay-sized material. In contrast, silt-size sediments display the same overall temporal trend but with a notable deviation during the Lower Miocene, where samples shift away from the weathering line toward a quartz-enriched composition (Figure 7b). The differing response of the two size fractions is clearly demonstrated by comparing CIA/CIX-WIP ratios from coeval clay and silt samples from the Leviathan section (Figure 8). Although both fractions show an overall decrease in ratios from the Oligocene to the Upper Miocene, reflecting progressively weaker source-rock weathering, Lower Miocene silt fractions exhibit markedly elevated ratios, consistent with significant quartz enrichment and sediment recycling. This interpretation is further supported by the increasing quartz content in the silt fraction, as indicated by lower Al2O3/SiO2 ratios (Figure 6b). The temporal shift in the silt fraction aligns with alternating patterns in αAl during the same interval (Figure 5b), which further supports significant recycling.
Figure 7. CIA/CIX-WIP relationships for (a) clay and (b) silt fractions (silt-fraction data calculated after Torfstein and Steinberg (Reference Torfstein and Steinberg2020). Arrows indicate compositional trajectories associated with increasing chemical weathering of UCC rocks and quartz enrichment. Both clay and silt fractions show a negative correlation between CIA/CIX and WIP, reflecting decreasing chemical weathering from the Oligocene to the Late Miocene. Early Miocene silt samples deviate toward lower WIP and greater quartz enrichment, consistent with enhanced sediment recycling.
Figure 8. Temporal variation in CIA/WIP for clay and silt fractions from the Leviathan borehole. Both fractions show a gradual decrease in CIA/WIP through time, reflecting a shift toward less-weathered source compositions. Elevated CIA/WIP values in the silt fraction between ∼24-20 Ma record a phase of pronounced sediment recycling and increased incorporation of quartz-rich material.
Overall, the Lower Miocene represents an interval of pronounced sediment recycling, an effect that is most clearly expressed in the silt fraction. Recycling of clay-sized material was also enhanced at this time, as reflected by lower ϵNd values (Figure 6a) (Glazer et al. Reference Glazer, Avigad and Morag2024) and increased abundances of illite and K2O (Figure 3a–b). Still, its magnitude remained modest compared to that observed in the silt fraction.
6. Implications for Oligocene-Miocene uplift and denudation of Afro-Arabia
The combined weathering and recycling patterns documented above provide a coherent record of evolving topography and denudation regime during Oligocene-Miocene development of the Afro-Arabian dome.
6.a. Oligocene early-stage doming (34–25 Ma)
Sediments of Oligocene age at the base of the siliciclastic section in the Levant Basin are characterized by exceptionally strong chemical weathering. Such highly leached assemblages form through intense and prolonged weathering under warm, humid equatorial (tropical) conditions (Garzanti et al. Reference Garzanti, Padoan, Setti, Najman, Peruta and Villa2013b, Reference Garzanti, Andò, Padoan, Vezzoli and El Kammar2015; Clift et al. Reference Clift, Wan and Blusztajn2014, Reference Clift, Du, Mohtadi, Pahnke, Sutorius and Böning2024) and typify mature lateritic profiles (e.g. Matheis and Pearson, Reference Matheis and Pearson1982; Zeese et al. Reference Zeese, Schwertmann, Tietz and Jux1994; Giorgis et al. Reference Giorgis, Bonetto, Giustetto, Lawane, Pantet, Rossetti, Thomassin and Vinai2014). Modern analogues occur offshore equatorial West Africa, where kaolinite-rich sediments derive from the erosion of deeply weathered continental surfaces (Petschick et al. Reference Petschick, Kuhn and Gingele1996; Garzanti et al. Reference Garzanti, Bayon, Barbarano, Resentini, Vezzoli, Pastore, Levacher and Adeaga2024). The properties of detrital Oligocene sediments from the Levant Basin closely match those of recent sediments sourced from equatorial central Africa, regions blanketed by lateritic soils (Figure 3) (Garzanti et al. Reference Garzanti, Padoan, Setti, Najman, Peruta and Villa2013b), and are geochemically similar to Paleocene-Eocene laterites of NE Africa (Figure 3) (Deller, Reference Deller2012). Across Africa, laterites record extensive planation surfaces and etchplains formed by prolonged Phanerozoic weathering, most notably the Late Cretaceous-Late Eocene ‘African Surface’ (Bohannon, Reference Bohannon1986; Marker and McFarlane, Reference Marker and McFarlane1997; Chardon et al. Reference Chardon, Chevillotte, Beauvais, Grandin and Boulangé2006; Burke and Gunnell, Reference Burke and Gunnell2008).
Studies of lateritic paleosols in NE Africa demonstrate that intense lateritic weathering was largely restricted to the Paleocene-Eocene, when globally warm and humid conditions (Zachos et al. Reference Zachos, Pagani, Sloan, Thomas and Billups2001, Reference Zachos, Dickens and Zeebe2008; Rae et al. Reference Rae, Zhang, Liu, Foster, Stoll and Whiteford2021) favoured the development of thick weathering profiles. Radiometric dating of lateritic soils, together with their stratigraphic position beneath Early Oligocene volcanic rocks and Late Eocene-Oligocene siliciclastic sediments, indicates that lateritization in Afro-Arabia had effectively ceased by the Early Oligocene (Deller, Reference Deller2012; Perelló et al. Reference Perelló, Brockway and García2020 and references therein). Importantly, this termination predates major Neogene increases in seasonality and aridity in the region (Said, Reference Said1981; Privé-Gill et al. Reference Privé-Gill, Thomas and Lebret1999; Griffin, Reference Griffin2002; Senut et al. Reference Senut, Pickford and Ségalen2009; El-Saadawi et al. Reference El-Saadawi, Kamal-El-Din, Wheeler, Osman, El-Faramawi and El-Noamani2014) and therefore cannot be attributed solely to climatic change. The timing of lateritization, together with the preservation of laterites beneath Early Oligocene volcanic rocks along parts of the southern Red Sea region, in contrast to their removal in other uplifted areas, underscores the primary role of tectonics in terminating intense chemical weathering. Although climatic conditions during the Oligocene and Early Miocene may have remained favourable for laterite formation in parts of Afro-Arabia (e.g. Privé-Gill et al. Reference Privé-Gill, Thomas and Lebret1999; El-Saadawi et al. Reference El-Saadawi, Kamal-El-Din, Wheeler, Osman, El-Faramawi and El-Noamani2014), post-Eocene uplift fundamentally altered surface processes and inhibited the re-establishment of deep weathering profiles.
As the Afar plume head began impinging upon the base of the Afro-Arabian lithosphere in the Late Eocene (Ebinger and Sleep, Reference Ebinger and Sleep1998; Sembroni et al. Reference Sembroni, Faccenna, Becker and Molin2024), the long-standing carapace of deeply weathered rocks flexed, uplifted and began to erode (Figure 9a–b). Weathered detritus was mobilized by the emerging fluvial systems, most prominently the ancestral Nile River system, and transported toward the Eastern Mediterranean, where it accumulated in the Levant Basin (Figures 1–2a). Sedimentation rates in the Levant Basin during the Oligocene were relatively low (Figure 10a), consistent with the gradual onset of domal uplift and the slow initial stripping of the thick weathering profile.
Figure 9. Conceptual model for the evolution of topography, weathering, erosion and sediment supply from the Afro-Arabian dome to the Levant Basin. (a) Late Cretaceous-Late Eocene warm, humid conditions produced a thick weathering mantle. (b) Late Eocene-Oligocene domal uplift initiated stripping of this mantle, delivering intensely weathered sediment to the Levant Basin. (c) Early Miocene uplift of the Red Sea Rift flanks enhanced erosion and sediment recycling. Thereafter, erosion penetrated into the Neoproterozoic basement, supplying less-weathered sediment and marking the development of a rugged, high-relief landscape. Present-day elevations along the African Red Sea Rift flank range from ∼400 to ∼2000 m, whereas the main Nile flows at ∼30 to 350 m above sea level.
Figure 10. Representative sedimentary indicators from the Levant Basin (present study) compared with thermochronological data from around the Red Sea (Boone et al. Reference Boone, McMillan, Balestrieri, Kohn, Gleadow, Alimanovic, Hutchinson, Noble, Mackintosh and Seiler2025). The Oligocene interval exhibits the most intensely weathered compositions, reflecting the stripping of a weathering mantle that developed from the Late Cretaceous to the Late Eocene, before the onset of domal uplift. The Early Miocene is characterized by a pronounced peak in recycling indicators (high CIX/WIP) and elevated sedimentation rates, marking a phase of vigorous erosion associated with uplift of the Red Sea Rift flanks. Following this interval, weathering intensity significantly declines, indicating that erosion had penetrated through the weathering mantle into the underlying Neoproterozoic basement, signalling the development of a rugged, high-relief topography.
Regionally, continental ‘red beds’ of Oligocene to Lower Miocene age, rich in kaolinite, quartz and iron oxides, are widely documented around the Red Sea, Sinai and the Dead Sea basin (Montenat et al. Reference Montenat, D’Estevou, Purser, Burollet, Jarrige, Orszag-Sperber, Philobbos, Plaziat, Prat and Richert1988; Bohannon et al. Reference Bohannon, Naeser, Schmidt and Zimmermann1989; Refaat and Imam, Reference Refaat and Imam1999; Calvo and Bartov, Reference Calvo and Bartov2001; Bosworth, Reference Bosworth, Rasul and Stewart2015; Kedem, Reference Kedem2018; AlTammar, Reference AlTammar2021) and are commonly interpreted as laterite-derived deposits formed in response to early domal uplift (e.g. Burke and Gunnell, Reference Burke and Gunnell2008). Comparable Cenozoic etchplain dismantling associated with epeirogenic uplift is also well documented in West Africa, producing widespread Eocene-Pliocene ‘Continental Terminal’ units dominated by quartz, kaolinite and iron oxides (Lang et al. Reference Lang, Kogbe, Alidou, Alzouma, Bellion, Dubois, Durand, Guiraud, Houessou and De Klasz1990). Older Palaeozoic-Mesozoic laterite-derived sediments, abundant across Afro-Arabia (Germann et al. Reference Germann, Schwarz and Wipki1994; Schwarz and Germann, Reference Schwarz and Germann1995), may likewise have been recycled during the Oligocene.
Taken together, we interpret the Oligocene, chemically leached sediments of the Levant Basin as erosion products of mature, deeply weathered profiles that developed prior to uplift in Afro-Arabia. The chemically leached material at the base of the Levant Basin siliciclastic section marks the earliest phase of Afro-Arabian domal uplift and the large-scale dismantling of its weathering mantle. This interpretation is further supported by the widespread Oligocene truncation surfaces preserved along the crest of the Afro-Arabian dome, which record extensive denudation during the earliest stages of domal uplift (Avni et al. Reference Avni, Segev and Ginat2012; Sembroni et al. Reference Sembroni, Faccenna, Becker and Molin2024).
6.b. Late Oligocene-Early Miocene high-relief development and shifting erosion regimes (25–20 Ma)
During the Late Oligocene to Early Miocene, several independent sedimentary signals point to the transition from a low-relief, slowly rising dome to a more dynamic, high-relief landscape across Afro-Arabia. Sedimentation rates in the Levant Basin increase sharply (Figure 10a), indicating enhanced sediment supply as uplift accelerated. At the same time, the detrital assemblages become less intensely weathered than their older Oligocene counterparts, yet still chemically leached, reflecting erosion that began to penetrate below the mature weathered profile into less weathered horizons. This interval also records a marked rise in sediment recycling and quartz enrichment (Figure 10a). Together, these trends signify increasing topographic gradients and a shift from stable-etchplain stripping to more vigorous and spatially variable erosion associated with Late Oligocene to Early Miocene relief growth. The abrupt and intense increase in sediment recycling and transport to the Levant Basin in the Early Miocene indicates rapid source-area reorganization and enhanced erosion driven by tectonic uplift, which inhibited the re-establishment of deep chemical weathering even where climatic conditions were favourable (e.g. Privé-Gill et al. Reference Privé-Gill, Thomas and Lebret1999; El-Saadawi et al. Reference El-Saadawi, Kamal-El-Din, Wheeler, Osman, El-Faramawi and El-Noamani2014).
This phase coincides with the initiation of Red Sea rifting in the latest Oligocene (∼25 Ma). Thermochronology data from the Red Sea region independently indicate mild Oligocene uplift followed by significant Late Oligocene to Early Miocene uplift around the rift margins, interpreted as a flexural response to rift initiation (Figure 10b) (Lanari et al. Reference Lanari, Boutoux, Faccenna, Herman, Willett and Ballato2023; Boone et al. Reference Boone, McMillan, Balestrieri, Kohn, Gleadow, Alimanovic, Hutchinson, Noble, Mackintosh and Seiler2025). Consistently, topographic reconstructions document the establishment of high topography in the region at approximately the same time (e.g. Wilson et al. Reference Wilson, Roberts, Hoggard and White2014).
6.c. Middle-Late Miocene formation of rugged high topography (20–5 Ma)
Following the significant uplift around the Red Sea in the Early Miocene, erosion progressively breached the etchplain mantle and began incising into pristine Neoproterozoic basement rocks of the ANS, supplying increasingly fresh and less weathered detritus to the Levant Basin (Figure 10a). This deeper incision, driven by the combined effects of regional domal uplift and flexural uplift along the Red Sea Rift margins, steadily increased the delivery of newly exposed source material to the basin (Figure 9c).
Modern analogues highlight the geomorphic and climatic significance of this shift. Smectite and randomly interstratified illite-smectite mixed layers, which dominate the shallower Miocene intervals of the Levant Basin, form through mild weathering of igneous rocks under conditions of limited water circulation or pronounced seasonality (Weaver, Reference Weaver1989; Clift et al. Reference Clift, Wan and Blusztajn2014, Reference Clift, Du, Mohtadi, Pahnke, Sutorius and Böning2024). Such conditions are typical of semi-arid tropical belts such as the headwaters of the Nile (Figure 1a) (Garzanti et al. Reference Garzanti, Andò, Padoan, Vezzoli and El Kammar2015). Consequently, Quaternary Nile-derived clays entering the Mediterranean are dominated by smectite and illite-smectite mixed layers (Figure 3) (Stanley and Liyanage, Reference Stanley and Liyanage1986; Wahab and Stanley, Reference Wahab and Stanley1991; Stanley and Wingerath, Reference Stanley and Wingerath1996; Sandler and Herut, Reference Sandler and Herut2000), reflecting mild weathering and rapid erosion at the Ethiopian Plateau (Garzanti et al. Reference Garzanti, Andò, Padoan, Vezzoli and El Kammar2015). These same assemblages also dominate the modern Levant Basin (Figure 3) (Krom et al. Reference Krom, Cliff, Eijsink, Herut and Chester1999; Sandler and Herut, Reference Sandler and Herut2000), which currently receives nearly all its detritus from the Nile (Be’eri-Shlevin et al. Reference Be’eri-Shlevin, Avigad, Gerdes and Zlatkin2014; Sagy et al. Reference Sagy, Dror, Gardosh and Reshef2020).
Upper Miocene sediments of the Levant Basin closely resemble this modern signature in their illite-smectite-dominated clay mineralogy and mild-weathering geochemical fingerprints (Figure 3), which together point to rapid erosion under seasonal or semi-arid climatic conditions. This similarity indicates that by ∼10–5 Ma, both the climatic conditions and the geomorphic processes controlling erosion, chemical alteration and rapid sediment transport from uplands had already shifted toward a regime comparable to the present-day Nile-Levant source-to-sink system. This implies that a landscape experiencing fast incision and efficient routing of minimally weathered detritus was established by this time.
7. Conclusions
The Oligocene-Miocene siliciclastic section of the Levant Basin provides an archive of the evolving topography and drainage systems of Afro-Arabia during the development of the Afro-Arabian dome and the opening of the Red Sea Rift. By integrating clay mineralogy, major-trace element geochemistry, and weathering indices from both clay and silt fractions, we show that the sedimentary record tracks the progressive denudation of the continental interior and its response to mantle-driven uplift and rifting.
Deeply weathered Oligocene sediments, marked by extreme chemical alteration (high CIA, low WIP, high αAl) and kaolinite-rich clay assemblages, reflect intense continental weathering under warm-humid conditions and low-relief landscapes prior to regional uplift. These chemically mature rocks were progressively eroded as uplift commenced. The transition to less weathered Miocene deposits, characterized by lower CIA, higher WIP, lower αAl, greater compositional variability and illite-smectite-rich clay assemblages, signals a fundamental reorganization of surface processes and sediment routing as uplift accelerated across Afro-Arabia.
The geochemical signatures preserved in the Levant Basin independently constrain both the timing and style of regional uplift. The appearance of strongly weathered Oligocene detritus sets a minimum age of ∼33 Ma for the onset of regional-scale domal upwarping, landscape rejuvenation and the establishment of new large drainage systems. Declining weathering intensities, increased sediment recycling, and extremely high sedimentation rates between ∼25 and 20 Ma correspond to the rise of high-relief topography along the nascent Red Sea Rift shoulders. Continued reduction in weathering intensity during the Miocene, together with the emergence of a geochemical and mineralogical fingerprint akin to that of the modern Nile, indicates the establishment of rugged topography around the Red Sea and the development of a near-modern geomorphic and climatic regime across the Nile-Levant source-to-sink system.
Taken together, the Oligocene-Miocene sedimentary record of the deep Levant Basin captures the continent-scale response of Afro-Arabia to mantle dynamics and rifting. It documents the initiation, growth and geomorphic expression of one of Africa’s largest Cenozoic swells, providing a critical link between topographic evolution, weathering-erosion and sediment routing into the Eastern Mediterranean.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/S0016756826100594.
Acknowledgements
We thank the Israel Ministry of Energy for supporting this project and allowing access to the National Rock Archive stored at the Geological Survey of Israel. Karish North borehole data and samples are courtesy of Energean Israel Limited. Leviathan borehole data and samples were generously provided by NewMed Energy, Ratio Energies, and Chevron Mediterranean Limited. The helpful guidance and assistance of Y. Harlavan, K. Wiess, and O. Berlin (GSI) in carrying out geochemical analyses are greatly appreciated. The manuscript benefited from the careful and constructive reviews of S. Critelli and G. Calves.
Financial support
The research was funded by the Israel Ministry of Energy (D.A. and N.M., contract number 220-17-006) and by the Israel Science Foundation (D.A., ISF grant numbers 512/17, 3608/21).
Data availability
The authors declare that the data supporting the findings of this study are available within the article and its supplementary data files.
Declaration of interest
The authors declare none.
Open access
