The research team, working at outcrops between 2021 and 2024, photographed, analysed and measured the specimens directly in the field, because the lithology and consistency of the host rock made collecting them impracticable. The traces are preserved in concave and convex epirelief, hyporelief and full relief within marly limestones of Eifelian and Givetian age, roughly 393 to 383 million years old. Two distinct ichnoassemblages emerged from the analysis. The Eifelian strata yielded Arenicolites isp., Crescentichnus antarcticus, Selenichnites hundalensis and Osculichnus cf. labialis, while the Givetian layers contain Arenicolites isp., Diplocraterion isp., Sinusichnus sinuosus and Thalassinoides paradoxicus.

The most eye-catching of these fossils are the crescentic and horseshoe-shaped impressions attributed to xiphosurans, the group of arthropods that includes modern horseshoe crabs. Remarkably, no xiphosuran body fossils have ever been found in Devonian deposits anywhere in Africa, yet the traces at Hamar Laghdad show exactly the kind of morphology that living limulids produce when they dig into the sea floor. Selenichnites hundalensis from the lower Eifelian consists of suboval depressions with paired crescentic lobes, faint segmentation, occasional scratch traces and, in some specimens, an elongate telson impression trailing behind. The new Moroccan material represents the oldest occurrence of Selenichnites in Gondwana and one of the oldest in the world, previously known only from Late Triassic strata.

Crescentichnus antarcticus, preserved as elongated crescentic depressions measuring 5 to 8 centimetres long and 7 to 11 centimetres wide, is interpreted as a prod trace made when a horseshoe crab’s prosoma touched the sediment at an angle, perhaps as the animal swam up from the sea floor or made rapid contact to catch prey. The study draws on decades of work on modern limulid burrowing, including Eldredge’s classic four-stage description of burial by downward flexion of the prosoma and promotor-remotor swings of the prosomal legs. Intriguingly, the co-occurrence of Crescentichnus, Selenichnites and the fish-jaw trace Osculichnus with dwelling burrows of Arenicolites on the same surfaces hints at a hunting and feeding relationship between the tracemakers and the burrow-dwelling worms or crustaceans below.

Osculichnus cf. labialis itself is a curiosity: a hypichnial bilobate mound whose two lip-like lobes reflect the outline of upper and lower jaws. Such traces are usually attributed to jawed fish that plunged vertically or obliquely into the sediment to seize prey. The Hamar Laghdad specimen, with a larger lobe 20 millimetres wide and a smaller one 10 millimetres wide, separated by an undulate furrow with a small central knob, is the first record of this poorly known ichnogenus from the Middle Devonian of Africa, adding a predatory fish to the cast of characters roaming the Devonian shelf.

The Givetian assemblage tells a different story, one of complex engineering. Sinusichnus sinuosus consists of regular to slightly irregular sinusoidal tunnel systems with smooth, unlined walls, predominantly horizontal, and branching at triple junctions in Y-shaped and occasionally T-shaped patterns, with branch angles between 112 and 125 degrees. Tunnel diameters range from 1 to 2 centimetres, meander amplitudes from 4 to 8 centimetres and wavelengths from 10 to 20 centimetres, with individual systems locally exceeding 60 centimetres in length. The new Moroccan material is currently the oldest known occurrence of this ichnospecies in Gondwana, and the first evidence of the ichnogenus in Africa.

Even more striking are the burrow networks of Thalassinoides paradoxicus, which in the upper Givetian carbonates surround and converge upon the shells of dead cephalopods, including oncocerids, orthocerids and multilobate pharciceratid and beloceratid ammonoids. The burrow fill, a brown, very fine-grained clayey to marly carbonate, contrasts sharply with the grey to black host rock. The researchers propose an exceptional feeding strategy: after the cephalopods died and their soft parts decayed, the carcasses became nutrient sources, microbes colonised the organic compounds, and the Thalassinoides tracemakers exploited the biofilm inside the body chambers and around the conchs through conveyor-belt feeding. To the authors’ knowledge, no similar association of body fossils surrounded by such complex burrow systems has been reported before.

Because Palaeozoic burrow systems assigned to Thalassinoides predate the callianassid shrimps that construct similar burrows today, the Devonian tracemakers must have been non-callianassid crustacean arthropods or trilobites. Likewise, the Sinusichnus producers are proposed to be eumalacostracan crustaceans, whose segmented abdomens would have permitted the sinuous movements recorded in the burrows. The study observes gradual transitions between Sinusichnus and Thalassinoides in the same strata, suggesting that the tracemakers shifted between feeding strategies, from fodinichnia to domichnia. Taken together, these traces suggest that the complex burrowing, navigational and scavenging behaviours of modern arthropods have far more ancient roots than previously thought.

The trace fossils also encode a detailed record of environmental change. During the Eifelian, the Tafilalt Platform was a pelagic submarine high with very slow carbonate sedimentation, producing condensed nodular limestones and marls rich in ammonoids such as Fidelites, Foordites and Pinacites. The ichnofauna of that interval, combining fodinichnial traces like Crescentichnus and Selenichnites with vertical dwelling burrows of Arenicolites, belongs to the Skolithos-Cruziana ichnofacies and points to a moderately shallow inner shelf with high hydrodynamic energy, well-oxygenated water and abundant organic matter. By the Givetian, deposition took place in somewhat deeper settings, still on the shelf, with alternating calm and energetic conditions recorded by the co-occurrence of horizontal and vertical burrows.

This sea-level rise on the inner shelf of an epicontinental sea at the northwestern margin of Gondwana was shaped by peculiar local conditions. The more than 40 conical Kess-Kess mud-mounds of late Emsian age, distributed over 7 kilometres, created a palaeotopography that controlled sedimentation and ecosystem conditions long after the mounds stopped growing, generating diverse microenvironments with varying water depth, energy, sediment accumulation and light availability. The region’s famous palaeobiodiversity, it turns out, includes not only the skeletal record of ammonites, bivalves and brachiopods but also this hidden archive of behaviour. The abundance and variety of both trace and body fossils strongly encourage further systematic prospecting at Hamar Laghdad, where the Devonian sea floor may yet surrender more stories written not in bone but in burrow.

Subject of Research: Middle Devonian ichnofossils from Hamar Laghdad (eastern Anti-Atlas, Morocco)

Article Title: Middle Devonian ichnofossils from Hamar Laghdad (eastern Anti-Atlas, Morocco)

Article References: Bel Haouz, W., Lagnaoui, A., Klug, C., Baidder, L., & Maanan, M. (2026). Middle Devonian ichnofossils from Hamar Laghdad (eastern Anti-Atlas, Morocco). Swiss Journal of Palaeontology, 145, 403-431. https://doi.org/10.3897/sjp.145.188799

Image Credits: AI Generated

DOI: 10.3897/sjp.145.188799

Keywords: Devonian, ichnology, trace fossils, Morocco, Anti-Atlas, paleontology, xiphosurans, horseshoe crabs, arthropods, Hamar Laghdad, Middle, ichnofossils

The West African Craton is one of Earth’s great stable blocks of continental crust, and its northern margin has long been a battleground for geologists trying to understand how it was assembled into Gondwana. The Anti-Atlas belt preserves two major orogenic cycles: the roughly 2.2-billion-year-old Eburnean Orogeny in the west, and the Neoproterozoic Pan-African Orogeny, which culminated around 650 million years ago with the accretion of oceanic arc and ophiolite complexes such as those at Bou Azzer and Sirwa. A major structure called the Anti-Atlas Major Fault has traditionally been drawn as the boundary between the ancient Eburnean basement and the younger Pan-African terranes. Whether Paleoproterozoic crust extends north of that fault, however, has remained one of the most contested questions in the region, and it is precisely here that the new detrital zircon data deliver their most striking result.

The team analyzed a fine- to medium-grained greenish sandstone collected near the entrance of the Zgounder silver mine, part of the Imghi Formation of the Saghro Group. This unit consists of thick-bedded greywackes and graded turbidites, the classic deposits of deep-water sediment gravity flows. Of 138 laser-ablation analyses on 93 zircon grains, 90 were concordant, and the age spectrum turned out to be remarkably narrow. The youngest coherent cluster of grains yielded a maximum depositional age of 2025 million years, while the overall distribution is dominated by a single sharp peak at about 2100 million years, with one lone grain as old as 3700 million years. Crucially, not a single zircon younger than 1600 million years was found, despite the fact that Pan-African igneous rocks between 883 and 640 million years old are abundant in the surrounding Sirwa inlier and are commonly reported in Saghro Group sediments elsewhere.

That absence is the key. The narrow gap between the 2100-million-year peak and the 2025-million-year maximum depositional age suggests that the sediments were dumped into a basin flanked by an uplifted, pristine block of Eburnean basement that acted as the exclusive sediment source. The basin received no volcanic ash or erosional debris from the Ediacaran magmatism that was raging elsewhere in the belt. In other words, the Saghro Group basin in the Sirwa area was walled by 2.1-billion-year-old continental crust. Because the number of grains analyzed is well above the thresholds normally considered adequate for provenance work, the authors argue the result is robust rather than a sampling artifact. The implication is that Paleoproterozoic crust of the West African Craton extends beneath the Sirwa massif and continues northward beyond the Anti-Atlas Major Fault, possibly as far as the South Atlas Fault, which would shift the location of the definitive craton-margin suture zone significantly to the north.

The magmatic rocks tell an equally compelling story, in two acts. The first act belongs to the Saghro Group, whose mafic volcanic and intrusive rocks, basalts, basaltic andesites, dolerites, and a gabbro from the Tittalt Formation, define a calc-alkaline suite with a within-plate geochemical signature. On normalized multi-element diagrams they show enrichment in large-ion lithophile elements such as cesium, rubidium, barium, and potassium relative to high-field-strength elements, together with the negative niobium-tantalum and titanium anomalies that are the classic fingerprint of subduction-zone influence. Yet tectonic discrimination diagrams place them in the fields of continental tholeiites adjacent to back-arc basin basalts. The combination points to an early Ediacaran extensional phase in which advanced lithospheric thinning allowed asthenospheric decompression melting of a sub-continental lithospheric mantle that had been chemically fertilized, or metasomatized, by an earlier Cryogenian subduction event.

Isotopes reinforce this picture of a young, mantle-dominated magma system. The Saghro Group samples yield strongly positive initial epsilon-neodymium values of +3.2 to +4.6, calculated at a reference age of 620 million years, with depleted-mantle model ages of 1.02 to 0.91 billion years. A binary mixing model, using a metasomatized mantle end-member and a Paleoproterozoic crustal end-member with an epsilon-neodymium of about -16, indicates that the Saghro magmas contain 88 to 92 percent mantle-derived material and only 8 to 12 percent crustal input. These are among the most juvenile signatures known from the Ediacaran of the Anti-Atlas, and they suggest the back-arc basin was opening above a mantle source that had been only lightly contaminated by older crust, consistent with the thinning lithosphere of a maturing basin behind the Cadomian subduction zone that fringed the Gondwanan margin.

The second act is the Ouarzazate Group, and it could hardly be more different. New U-Pb zircon ages of 575 plus or minus 3 million years for a rhyolitic dike and 564 plus or minus 2 million years for a granite intersected in a drill hole at 555 to 568 meters depth bracket roughly 11 million years of post-collisional magmatism. These ages match, within uncertainty, a suite of previously dated intrusions in the Sirwa massif, including the Askaoun granodiorite, the Tikhfist rhyolite, and the Imourkhssen granite, indicating a rapid succession of intrusive events. Geochemically, the Ouarzazate rocks form a high-K calc-alkaline to shoshonitic, felsic-to-intermediate series with silica contents reaching nearly 80 weight percent, pronounced negative europium anomalies, and strong depletion in strontium, phosphorus, niobium, tantalum, and titanium, the hallmarks of extensive plagioclase and accessory-mineral fractionation combined with a strongly crustal source.

The isotopic contrast between the two groups is stark. Ouarzazate Group rocks cluster near or below the chondritic reference line, with initial epsilon-neodymium values between -0.8 and +1.1 and model ages of 1.30 to 1.15 billion years, far older than their crystallization ages. The mixing model quantifies the shift: crustal contributions rise from about 15 percent in a granodiorite to 25 percent in a rhyolite. Without such contamination, a purely mantle-derived magma at 570 million years ago would be expected to show epsilon-neodymium values of +7 to +8, so the near-zero values represent a major isotopic pull from ancient basement. A single inherited zircon grain of 2156 plus or minus 54 million years in the granite provides direct physical evidence of that reworking, matching widespread Paleoproterozoic inheritance reported in Ouarzazate ignimbrites and granites across the Anti-Atlas.

Putting the pieces together, the authors propose a coherent geodynamic sequence. Around 630 to 600 million years ago, the Saghro Group sediments and their associated calc-alkaline mafic magmas accumulated in a back-arc basin whose shoulders were built of uplifted 2.1-billion-year-old Eburnean crust. As the basin matured, magmas progressively tapped deeper, less contaminated asthenospheric reservoirs, a transition mirrored by the rift-tholeiite, ocean-island-basalt, and mid-ocean-ridge-basalt signatures seen in basalts higher in the Saghro stratigraphy at Sidi Flah and Boumalne. Then, in the late Ediacaran, the tectonic regime flipped. Lithospheric delamination and possible slab break-off injected a thermal pulse into the lower continental crust, triggering widespread melting of both the crust and a subduction-modified lithospheric mantle. The result was a massive flare-up of silicic volcanism and plutonism, part of a Silicic Large Igneous Province recognized across the Anti-Atlas, whose A2-type granites and shoshonitic ignimbrites record post-collisional crustal collapse on the fractured, metacratonic margin of the craton.

Beyond rewriting the tectonic map of northwest Gondwana, the study has practical resonance. The Zgounder deposit, one of Morocco’s most important silver mines, sits within exactly this Ediacaran magmatic framework, and the same extensional structures that channeled deep-sourced magmas upward also focused mineralizing fluids. More broadly, the work demonstrates how a single handful of detrital zircons, when read carefully, can relocate a continental suture by hundreds of kilometers and reveal that the craton beneath modern Morocco is far more extensive than its surface outcrops suggest. As similar isotopic and geochronological toolkits are applied to other contested craton margins around the world, hidden blocks of ancient crust may well continue to surface from the sedimentary record itself.

Subject of Research: Petrogenesis and geodynamic setting of Ediacaran sedimentary and magmatic rocks in the Sirwa massif, Central Anti-Atlas, Morocco

Article Title: Petrogenesis and geodynamic setting of Ediacaran rocks from the Sirwa massif, Central Anti-Atlas of Morocco

Article References: Ben-Tami, A., Belkacim, S., El Kabouri, J., Baidada, B., Davies, J. H. F. L., Perrot, M. G., Bhilisse, M., Assalmi, M., Ferraq, M., & Bouabdellah, M. (2026). Petrogenesis and geodynamic setting of Ediacaran rocks from the Sirwa massif, Central Anti-Atlas of Morocco. Solid Earth, 17(9), 1063-1086. https://doi.org/10.5194/se-17-1063-2026

Image Credits: AI Generated

DOI: 10.5194/se-17-1063-2026

Keywords: Anti-Atlas, Morocco, Ediacaran, detrital zircons, U-Pb geochronology, West African Craton, Pan-African Orogeny, back-arc basin, post-collisional magmatism, Sm-Nd isotopes, Saghro Group, Ouarzazate Group

The Bou Azzer–El Graara inlier occupies a special place in the geology of North Africa. It lies within the Pan-African suture zone, the scar left behind when an ancient ocean closed during the assembly of the West African Craton more than half a billion years ago. The inlier preserves one of the most representative Neoproterozoic ophiolite successions known, a fragment of oceanic crust and mantle rocks thrust onto continental margins during arc–continent collision. These same serpentinite bodies later became the host of the famous cobalt–nickel arsenide ores that have been mined at Bou Azzer for nearly a century, making the district a globally significant source of cobalt and a natural laboratory for studying how ancient plate boundaries control the distribution of metals.

Despite decades of geological mapping, structural analysis and geophysical surveying in the region, no previous study had combined quantitative machine learning classification of magnetic edges with three-dimensional magnetic inversion inside a single multiscale structural framework. That gap is what motivated Ayoub Soulaimani of Morocco’s Directorate of Geology, Mines and Hydrocarbons, Saâd Soulaimani of the Rabat School of Mines, and Abdelhalim Miftah of Hassan First University of Settat to design a four-stage workflow built around high-resolution aeromagnetic data acquired under the Moroccan national airborne survey program. The result is a methodology that turns raw magnetic measurements into a ranked, probability-based map of where hidden structures, and potentially hidden ores, are most likely to lie.

The first stage of the workflow involved computing a suite of potential-field derivatives from the total magnetic intensity data. These included the horizontal gradient, the analytic signal, three orthogonal first-order directional gradients, the tilt derivative, the horizontal gradient of the tilt angle, and a residual map reduced to the pole. Each of these filters emphasizes different aspects of the magnetic field. The horizontal gradient and analytic signal highlight the edges of magnetized bodies, the directional gradients accentuate lineaments oriented in specific azimuths, and the tilt derivative balances the responses of shallow and deep sources so that weak signals from deeply buried contacts remain visible. Together they form a multidimensional description of where the magnetic fabric of the region changes abruptly, which in turn corresponds to lithological boundaries and faults.

Those derivative maps then served as the input features for training a feed-forward artificial neural network, optimized through the Levenberg–Marquardt backpropagation algorithm, a classical and computationally efficient training method for small to medium networks. The researchers tested two weighting schemes for the input data: one in which all derivatives contributed equally, and another in which derivatives known to be especially sensitive to lithological contacts received selective weighting. Both configurations reached an accuracy of roughly 86 percent, and the very similar area-under-the-curve values obtained in the two cases suggested to the authors that the solution is robust rather than an artifact of any particular parameterization. In other words, the network was genuinely learning the structural signature of the region, not merely fitting noise.

The output of the trained network is a set of weighted probability surfaces that quantify, pixel by pixel, the likelihood that a structural discontinuity exists at that location. When compared against existing geological maps, these surfaces reproduced all of the major structural corridors already documented in the Bou Azzer region, providing an independent validation of the approach. More intriguingly, they also revealed zones of structural complexity that had never been mapped before, places where the magnetic fabric implies intersecting fault sets and rotated blocks that surface geology alone had not resolved. It is precisely such corridors of intersecting structures that tend to channel hydrothermal fluids and localize mineralization, which makes the newly identified zones prime candidates for future exploration.

In parallel with the machine learning analysis, the team performed a three-dimensional inversion of the magnetic data over the Foum Zguid dyke zone, one of the most striking magmatic features of the Anti-Atlas. The inversion reconstructed the volume distribution of magnetic susceptibility and allowed the researchers to recover the geometry of the dyke structure down to a depth of about two kilometers. This kind of quantitative depth constraint is rare in regional structural studies and demonstrates how modern inversion algorithms, originally developed for mineral deposit scale problems, can be scaled up to interrogate the deep architecture of entire tectonic corridors.

The final synthesis combined gradient analysis, Euler deconvolution for estimating source depths, the neural network prospectivity results, and the three-dimensional susceptibility model into a single high-resolution structural interpretation. The dominant fault orientations that emerged are north–south and WNW–ESE, a pattern that carries direct geodynamic significance. The north–south set is consistent with structures related to the Pan-African collision and its later reactivation, while the WNW–ESE set aligns with the major shear zones that dissect the Anti-Atlas belt. The study thus links the fine-scale magnetic fabric of the inlier to the broad tectonic evolution of the northern margin of the West African Craton, from Neoproterozoic ocean closure through Paleozoic deformation.

The economic implications are immediate. Bou Azzer remains one of the few operating cobalt arsenide districts in the world, and cobalt has become a strategically critical metal for battery technologies. The cobalt–nickel–arsenic ores at Bou Azzer are hosted in serpentinites along fault-controlled hydrothermal veins, so the identification of previously unrecognized structural corridors directly translates into new underexplored target zones for cobalt, copper, silver and gold. Rather than drilling blindly, exploration geologists can now prioritize the areas where the neural network’s probability surfaces intersect favorable host rocks and where Euler deconvolution indicates structures extending to mineable depths.

Beyond Morocco, the study offers a template that other exploration geologists and structural mappers can adapt. The workflow requires nothing more exotic than a standard aeromagnetic dataset, a set of well-established potential-field filters, and a modest feed-forward neural network, yet it delivers validated structural probability maps and quantitative three-dimensional models in a single coherent framework. As airborne magnetic surveys become cheaper and machine learning tools become more accessible, the approach demonstrated in the Central Anti-Atlas suggests that many of the world’s poorly mapped Precambrian terranes could be re-examined at high resolution, revealing both the deep tectonic history recorded in their magnetic fabrics and the mineral deposits that history has left behind.

Subject of Research: Machine learning analysis of aeromagnetic data for structural mapping and mineral prospectivity in the Moroccan Anti-Atlas

Article Title: Structural and tectonic analysis of the Moroccan Central anti-atlas using predictive targeting with machine learning and inversion of aeromagnetic data: geodynamic and mining implications

Article References: Soulaimani, A., Soulaimani, S., & Miftah, A. (2026). Structural and tectonic analysis of the Moroccan Central anti-atlas using predictive targeting with machine learning and inversion of aeromagnetic data: geodynamic and mining implications. Earth Science Informatics, 19(11), Article 203. https://doi.org/10.1007/s12145-026-02257-w

Image Credits: AI Generated

DOI: 10.1007/s12145-026-02257-w

Keywords: aeromagnetic data, machine learning, artificial neural network, Bou Azzer, Anti-Atlas, Morocco, cobalt mineralization, magnetic inversion, structural geology, Pan-African suture, mineral prospectivity, geophysics