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Establishing the biogenicity of sedimentary surface textures with unresolved microbial origin is critical to any environmental and geobiological interpretation of clastic settings. Here, some Ediacaran wrinkle structures and associated carbonaceous greywacke samples containing mat fragments rich in 'bacteriomorph acritarchs' are investigated. Their biogenicity was evaluated with transmitted light and scanning electron microscopy, epifluorescence and Raman spectroscopy, and confirmed by the presence of distinct cyanobacterial biomarkers. The comparison of results yielded by these techniques validates the use of Raman spectroscopy on Neoproterozoic kerogen (organic‐walled microfossils and amorphous organic material) under low metamorphic conditions. Raman spectrographs also allowed recognition of associated rare‐earth element‐rich phosphate (monazite) and subsidiary metal sulphide concentrations, and interpreted as a result of biosorption and/or mat trapping under normal oxic conditions. These microbial mat features represent cyanobacterial bloom‐forming Bavlinella acritarchs, which characterise eutrophic episodes in a semi‐enclosed retroarc basin sandwiched between an active Cadomian arc and West Gondwana. [ABSTRACT FROM AUTHOR]

Thalassinoides Ehrenberg, 1944 are relatively common bioturbational structures in carbonate shallow marine successions from the early Paleozoic. Much rarer is the reference to this ichnogenus in siliciclastic formations from the same age. In the Ordovician Lashkerak Formation cropping out at the Central Alborz mountains, Iran, Thalassinoides is a common trace fossil in wave-dominated shoreface complex and prodelta-mouth bar environments of a fluvial-dominated delta. We compare the Middle-to-Upper Ordovician branching networks of the Unit 2 of the Lashkerak Formation with the ichnospecies Thalassinoides horizontalis Myrow, 1995 emphasizing the almost entire beddingparallel orientation, regular branching and lack of constrictions and swellings. The eodiagenetic halos developed from mucus-lining walls, or by change of the original sediment fabric, typical of this and other ichnospecies of Thalassinoides in carbonate settings are not found in sandstones. The almost polygonal mazes from the Lashkerak Formation are also compared with the recently erected Protopaleodictyon aitkeni Morgan, Henderson & Pratt (2019), considered as a giant graphoglyptid in an early evolutionary stage of these forms in shallow marine environments. Both trace fossils are similar in morphology, size, preservation, ichnofacies and interpreted function, thus being P. aitkeni a junior synonym of Thalassinoides horizontalis. [ABSTRACT FROM AUTHOR]

The c. 100 myr extensive fossil record of bee brood nests and cells (calichnia) in siliciclastic sedimentary deposits, or palaeosols, is virtually devoid of the presence of their producers. The absence of a more specific assignment to a producer of the different ichnogenera of the ichnofamily Celliformidae precludes their use in phylogenetic and palaeobiogeographic studies. Omission surfaces developed in incipient carbonate palaeosols during the late Holocene (middle Neoglacial), c. 2975 yr cal BP, on the southwest coast of mainland Portugal show insect calichnia in dense ichnofabrics dominated by shallow discrete cells (Palmiraichnus castellanosi) and cells at the terminus of vertical shafts. At Carreira Brava, one of the studied sites, bees ready to abandon their cells were found in an exceptional state of preservation inside the sealed brood chambers. The chambers also preserve the inner cell hydrophobic polymerized membrane and remains of the monospecific Brassicaceae‐type pollen provision. Although the cause of mass mortality remains a mystery, oxygen depletion due to sudden flooding of the nesting substrate and consequent or overnight temperature drop, just before emergence, are plausible causes. The anaerobic conditions and later rapid carbonate diagenetic lithification are the likely causes of the preservation of the bees and the inner cell organic membrane. The favourable climate conditions for the development of successive, dense ichnofabrics from an omission suite dominated by bee brood cells may be the result of slightly colder and higher‐precipitation winters during the Neoglacial interval. [ABSTRACT FROM AUTHOR]

The stability of slopes and hillsides involving rock or soil masses depends crucially on the occurring geological and geotechnical conditions. The village of Monsanto, municipality of Idanha-a-Nova, is located on a granitic inselberg. The tourist interest of the village lies largely in the fusion of the granitic rock mass with the man-made constructions and in the aesthetics of several granitic boulders scattered throughout the village. In the present work the geological and geotechnical characterization of the rock mass has been carried out, namely by the field survey of the entire intervention area and by a set of laboratory tests on samples collected in the field (ultrasound propagation velocity and the uniaxial compression test). Based on this information, the shear strength of the discontinuities was estimated and a kinematic analysis was performed using the Dips 7.0 commercial software, with the objective of defining the predominant sets of joints and identifying the most probable failure mechanisms in each hillside.

Ten detailed sections have been logged and studied from the "Infra-Cenomanian" to the Cenomanian–Turonian deposits in the Errachidia–Boudnib–Erfoud Basin between Tazzouguerte and Anounizme(SE Morocco). They show variations in their lithology and microfacies that reflect changes in the depositional environment from the base to the top of the sedimentary record. Indeed, depositional setting grades from a fluvial environment marked by sandstone deposits of the Ifezouane Formation to an alluvial plain and coastal lagoon environment comprising an alternation of red clay, gypsum, and green marl beds of the Aoufous Formation and, finally, towards shallow to moderately deep marine environments with the deposition of the carbonates of the Akrabou Formation. Correlations between the studied sections show variations in the thickness of strata throughout the basin. The variations recorded in the so-called "Infra-Cenomanian" series may be related to the structuration of the basement. The Cenomanian–Turonian carbonate platform shows deeper marine and thicker sediments towards the east, while it thins towards the west until its disappearance in Anounizme. This reflects the global Cenomanian–Turonian transgression in the Errachidia–Boudnib–Erfoud Basin from the eastern Tethyan realm towards the west. The regional correlation of the Errachidia–Boudnib–Erfoud Basin with the Ouarzazate and Agadir basins shows an eastward thinning of the Cenomanian–Turonian marine deposits of Agadir. This suggests the presence of a paleorelief at the Anounizme locality. This could be the boundary between the Errachidia–Boudnib–Erfoud Basin, with Tethyan influence, to the east and those of Ouarzazate and Agadir, with Atlantic affinity, to the west. [ABSTRACT FROM AUTHOR]

Ichnofossils, the fossilized products of life-substrate interactions, are among the most abundant biosignatures on Earth and therefore they may provide scientific evidence of potential life that may have existed on Mars. Ichnofossils offer unique advantages in the search for extraterrestrial life, including the fact that they are resilient to processes that obliterate other evidence for past life, such as body fossils, as well as chemical and isotopic biosignatures. The goal of this paper is evaluating the suitability of the Mars 2020 Landing Site for ichnofossils. To this goal, we apply palaeontological predictive modelling, a technique used to forecast the location of fossil sites in uninvestigated areas on Earth. Accordingly, a geographic information system (GIS) of the landing site is developed. Each layer of the GIS maps the suitability for one or more ichnofossil types (bioturbation, bioerosion, biostratification structures) based on an assessment of a single attribute (suitability factor) of the Martian environment. Suitability criteria have been selected among the environmental attributes that control ichnofossil abundance and preservation in 18 reference sites on Earth. The goal of this research is delivered through three predictive maps showing which areas of the Mars 2020 Landing Site are more likely to preserve potential ichnofossils. On the basis of these maps, an ichnological strategy for the Perseverance rover is identified, indicating (1) 10 sites on Mars with high suitability for bioturbation, bioerosion and biostratification ichnofossils, (2) the ichnofossil types, if any, that are more likely to be present at each site, (3) the most efficient observation strategy for detecting eventual ichnofossils. The predictive maps and the ichnological strategy can be easily integrated in the existing plans for the exploration of the Jezero crater, realizing benefits in life-search efficiency and costreduction. [ABSTRACT FROM AUTHOR]

The Middle-Late Ordovician Ghelli Formation in the Kopet Dagh region northeastern Alborz range of Iran is composed of siliciclastic rocks deposited in a variety of turbidite to marginal marine environments (deep marine clastic fan and related environments and prodelta, distal delta front, proximal delta front and distributary channels). The ichnology of the middle member of the Ghelli Formation is here reported. Combined sedimentological and ichnological analysis allows recognition of a tide-influenced deltaic succession in the middle member of the Ghelli Formation consisting of three main facies associations: lower distributary channels, delta front and prodelta facies. Twenty-two ichnogenera have been identified in this marginal marine succession: Arenicolites, Arthrophycus, Bergaueria, Chondrites, Conichnus, Cruziana, Cylindrichnus, Didymaulichnus, Diplichnites, Diplocraterion, Helminthopsis, Gyrochorte, Lockeia, Macaronichnus, Monomorphichnus, Palaeophycus, Planolites, Rosselia, Rusophcus, Skolithos, Teichichnus and ?Scolicia. Their distribution is clearly linked with lithofacies and depositional palaeoenvironments. The ichnological analysis reveals that the trace fossil suites developed in these environments indicate low diversity and low to moderate abundance of burrows, poor development of tiering and sporadic distribution. Low ichnodiversity and low bioturbation intensities with higher bioturbation clusters consist of facies-crossing ichnogenera, and the impoverishment of suspension-feeding trophic types indicates 'stressed', non-archetypal expression of the Cruziana ichnofacies. The periodic higher intensities of bioturbation due to variations in hydrodynamic regimes of tidal currents reflect the archetypal of the Cruziana ichnofacies (and rare Skolithos ichnofacies). [ABSTRACT FROM AUTHOR]