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During the Tertiary evolution of the Western Mediterranean subduction system, the orogenic accretion at the Maghrebian margin let the stacking of three main tectonic zones of the Rif fold-and-thrust belt: 1) the Internal Zone; 2) the “Maghrebian Flysch” Nappes; and 3) the External Zone. In this context, a migrating foreland basin system developed between the Maghrebian orogenic belt and the adjacent African Craton. A comprehensive reconstruction of the foreland basin system of the Rif Chain for each phase of its accretional history is still missing. In this work, by integrating field observations with quantitative biostratigraphic data from calcareous nannofossils assemblages, sandstone composition, and detrital zircon U-Pb geochronology from selected stratigraphic successions, we reconstruct the foreland basin system that in the early Miocene developed in front of the growing Rif orogen. The analyzed successions are representative of (1) the “Beliounis Facies”, made of quartz-arenites and litharenites (Numidian-like “mixed succession”), from the Predorsalian Unit; (2) the “Mérinides Facies”, made of a Numidian-like “mixed succession”, from the “Maghrebian Flysch Basin”; and (3) the classical “Numidian Facies”, exclusively made of quartzarenites, from the Intrarifian Tanger Unit.The petrographic analyses and the detrital zircon U-Pb ages show the provenance of the quartzarenites of the “Numidian Facies” from the African Craton, whereas the sublitharenites and feldspathic litharenites, of both the “Mérinides Facies” and “Beliounis Facies”, show provenance from a cratonic area and the growing and unroofing Rif Chain, respectively. The Alpine signature of the detrital grains sedimented into the foredeep deposits of the early Miocene orogenic system of the Rif Chain is from the feldspathic litharenites of both the Mérinides Facies and the Beni Ider Flysch. Both show Mesozoic and Cenozoic U-Pb zircon populations, with a large population of zircons centered at ca. 32 Ma. The U and Th concentration, the Th/U ratio, and the REE pattern of this population of zircons suggest a possible source area from Oligocene doleritic rock intrusions, similar to the magmatic dyke swarms (diorite) cropping out in the Malaga region ( SE Spain).The biostratigraphic analyses pinpoint the same age for the arrival of the quartz grains in the Numidian, Mérinides, and Beliounis deposits, indicating about 1 Myr for their sedimentation (ca. 20-19 Ma, early Burdigalian). Together with field evidence, the biostratigraphic results point to an autochthonous deposition of the Numidian Sandstones on top of the Tanger Unit, allowing to delineate the early Burdigalian foreland basin system of the Rif Chain. The foreland depozone involved the Tanger Unit and received the “Numidian Facies” deposits ; the foredeep depozone hosted about 2000 m of the “Mérinides Facies” and the Beni Ider Flysch, and developed on the so-called “Flysch Basin Domain”; and, finally, the wedge-top depozone, characterized by the “Beliounis Facies”, developed on top of the Predorsalian Unit.The Numidian Sandstones and the Numidian-like deposits analyzed in Morocco show the same age of similar deposits from Algeria, Tunisia, and Sicily, suggesting a comparable early Burdigalian tectono-sedimentary evolution along the southern branch of the Western Mediterranean subduction-related orogen.

Since the 50s of the last century, several authors have investigated the nature of Tubotomaculum: enigmatic Mn-Fe mineralizations occurring in the latest Oligocene – Early Miocene varicoloured clays of the western Mediterranean area. Some authors regarded these structures as fossil traces[1], as fossil corals covered by Fe-oxides and manganite[2], or as inorganic Mn-Fe nodules with rhodocrosite, siderite, and non-crystalline Mn-oxides[3]. Due to the lack of mineralogical and geochemical data the processes of crystallization and growth are still unclear and questionable. Mn-oxides are significant environmental indicators for composition, pH, Eh, and biological activities. However, since they occur typically as cryptocrystalline and fine-grained mixtures of different Mn-phases and additional minerals, like Fe-oxides, carbonates and silicates, their characterization is a real challenge that requires a multimethodological approach. The Tubotomaculum samples analyzed in this work are from the western Rif in northern Morocco. The samples come from the pre-Numidian varicoloured clays of a section sampled close to the dam of the Reservoir Lake 9th April. This work is a first contribution aimed at providing a proper characterization of these mineralizations and to define the processes that led to their crystallization and growth. The final aim of this work is to provide evidence of the paleo-environmental conditions affecting the late Oligocene-early Miocene pre-Numidian sedimentary basin of northern Morocco. Crossing SEM-EDS, XRPD, TEM, 3D ED and FT-IR and Raman spectroscopy data, a proper characterization of the samples was achieved. Tubotomaculum consists of a very fine mixture of birnessite [(Ca,Na)(Mn4+,Mn3+)O4·1.5HO] and todorokite [(Ca,Na,K)(Mn4+,Mn3+)6O12·nHO], Mn-phases commonly recognized in oceanic nodules[4]. In particular, todorokite could be related to biological processes[5]. Goethite, hematite, kaolinite, and quartz were also found. All these minerals have a clear spatial distribution in the samples: millimetric Mn-Fe rich layers grow around central nuclei of clay minerals, quartz and/or bone fragments. In these layers 3-5 μm Mn-rich spheroidal structures occur in a Fe-rich matrix. SEM analyses reveal the presence of rounded structures suggesting microbial colonies. Their occurrence points to a biofilm formed by a single species of bacteria. These features allow to exclude the secondary diffusion of Mn and Fe from the surrounding sediment, suggesting a primary deposition of these mineralizations, possibly mediated by bacterial activity. According to these evidence, Tubotomaculum cannot be considered as a fossil trace or fragments of fossil coral. They are polymetallic nodules made up of a very fine-grained mixture Mn-Fe oxides, whose growth was biologically mediated by bacterial activity. Allegedly, such activity played a key role in catalyzing the oxidation of Mn2+ on the late Oligocene-early Miocene sea floor of northern Morocco.

We report on new sedimentological and biostratigraphical data concerning the “Numidian sandstones” outcropping in the Western Rif Belt. The analyzed sections are located south of Tangier city, close to the 9th April dam and pertain to the Intrarif Sub-domain, which, in turn, is part of the External Rif domain. In the western peri-Mediterranean chains, the “Numidian sandstones” display constant lithological features. We analysed six well-exposed lithostratigraphic sections, which are organized in three portions: (1) the “sub-Numidian”, mainly dominated by varicolored clays, (2) the “Numidian sandstones”, which includes predominantly massive quartzarenitic sandstones, sometimes interbedded with mudstones, and, finally, (3) the “supra-Numidian”, characterized by alternation of light green marls and thin-bedded siltstones. Stratigraphic sections of the “Numidian sandstones” were measured and described to provide detailed sedimentological characterization and facies analysis. The “sub-Numidian”, thick more than 100 meters, is commonly made of varicoloured clays, which in all the studied sections shows a horizon rich in Tubotomaculum. In the study area, the “Numidian sandstones” are about 1100 m thick; their facies analysis have been performed by using Pickering et al. (1995) classification scheme. The basal part of the examined sections shows similar characteristics: proximal channels filled by very thickbedded disorganised pebbly sandstones and amalgamated structureless sandstones (Facies A1.4 and B1.1). The base of the beds is scoured and sometimes shows decimetresized mud clasts torn away from the substratum. Paleocurrents measurements, mainly indicated by flute casts, are from southeast to northwest. Upward, coarse-grained quartzarenitic sandstones mainly characterize the middle part of all the sections. They are organized in massive and thick-bedded pebbly-sandstones, micro-conglomerates (Facies A2.4 and A2.5), and disorganised thick sandstones strata, often marked by fluid escape structures (Facies B1.1), revealing flows processes controlled by high-density turbidity currents and debris flows. These deposits evolve to plurimeter- to decimetre-thick mediumgrained sandstone and mud couplets (Facies C2.3) with a mainly fining-and thinning-upward trend, which we consider to be attributable to lobe and fringe lobe deposition. Commonly, the uppermost part of the sections shows a restoration of disorganised pebbly sandstones facies (Facies A1.4). The “supra-Numidian” caps the thick “Numidian sandstones” and is made up by about 200 m of bioturbated marls rich in planktonic foraminifera and fine-grained silty/muddy deposits. These latter show sedimentary structures related to unidirectional flows, probably owed to deep contourites currents. References Pickering K.T., Hiscott R.N., Kenyon N.H., Ricci Lucchi F. & Smith R. (editors) 1995. Atlas of architectural styles in turbidite systems. London: Chapman & Hall