Organic geochemical and petrographic study have been carried out on the Messinian Calcare di Base formation cropping out in northern Calabria and in Sicily. The main aim of this research concerns the deposition causes of this peculiar formation, up to now interpreted as essentially evaporitic limestone. Thin section observations put in evidence that carbonate layers are characterized by a peloidal fabric and the absence of any kind of metazoan skeletons. The prevailing fabric is characterized by dark peloid clusters, cylindrical or subcylindrical in shape, patchily dispersed into a lighter matrix. The shape, mineral composition, dimensions and context suggest that many elongate bodies can be interpreted as fecal pellets of unknown organisms. In addition carbonate layers also show two other facies types: i) a detrital, very finely gradated layer, and ii) a microbioalitic, sometimes more or less stromatolitic fabric. The bright UV-epifluorescence suggests a high content of organic matter in both fecal pellets and stromatolitic fabric. The study of carbonaceous remains emphasized a great variety of the organic input. Geochemical data (Rock-Eval pyrolysis) indicate a mixed (marine and continental) organic input. These data have been confirmed by organic petrographic observations (palynofacies) which revealed the presence of phytoclasts derived from continental plant tissues, amorphous organic matter, and variable proportions of zooclasts, pollens, spores, phytoplanktonic organisms and filaments presumably attributable to cyanobacteria. Preliminary results from organic geochemistry and petrography could suggest that the depositional environment became more and more restricted, allowing the survival of organisms adapted to extreme conditions, only. These enigmatic organisms have not been observed yet, however their biological signatures in the sediments are testified by the geochemistry data and palynofacies observation. Moreover, the presence of well preserved and bright-fluorescent spores and pollens indicate that these elements did not undergo degradation and oxidation, suggesting a sedimentary environment characterized by a stratified water column with bottom anoxic conditions. Such context, combining a good preservation state of organic matter and a typified character (nearly extreme conditions) of the environment, reveals highly favorable for undertaking the biochemical study of organic compounds associated with these sedimentary deposits. The amino-acid analysis of peptide remains may help to understand the influence of soluble macromolecules (mainly derived from microbial EPS) in the formation of authigenic carbonates. We can also expect the GC-MS detection of preserved lipidic biomarkers, providing the molecular signature of microscopically non-identifiable (non-preserved) organisms.
Abstract This paper presents the results of the mineralogical, petrographic and chemical study of different archaeological samples related to terracruda sculptures and other elements that were part of the architectural decoration of the Buddhist sites of Tepe Narenj and Qol‐e‐tut (Kabul, Afghanistan; fifth to 11th centuries CE). The main objective of the study was to characterize the samples using an archaeometric approach. The study helped to better understand the materials involved in the modeling of Afghan sculptures and their processing, such as the different nature of the clay layers and the finishing ‘stucco’ coating. The results further indicate that similarities exist among the manufacturing process of the studied samples and that used today by an ancient caste of clay artists in West Bengal (India), suggesting the existence of a continuous technological tradition that deserves to be further explored in the future.
Abstract. The coralligenous build-ups located in Mediterranean shelf in front of Marzamemi (SE – Sicily, Italy) represent useful natural examples to study the relationship between skeletal organisms and non-skeletal components in marine bioconstructions. Coralligenous build-ups are formed in open marine systems and their comparison with coeval bioconstructions (biostalactites) of confined environments, like submarine caves, allows depicting the complex interactions between metazoans and microbial communities in the formations of recent bioconstructions in different Mediterranean settings. In this study, two coralligenous build-ups were characterized in terms of organisms and sediments involved in their formation. The framework mainly consists of coralline algae and subordinate bryozoans and serpulids. Sponges affect the general morphology of the bioconstructions both interacting with skeletonised organisms and through bioerosion activity. The micrite (microcrystalline calcite) is a minor component of the build-ups and consists of two types: autochthonous (in situ) and allochthonous (detrital). Fine autochthonous micrite mineralized directly inside the framework cavities and shows aphanitic or peloidal fabric, produced by organomineralization processes of soft sponge tissues and microbial metabolic activity, respectively. The detrital micrite occurring inside cavities derives from external sources or erosion processes of the bioconstructions themselves. This component has been classified as organic or inorganic based on the organic matter contents deduced by UV-Epifluorescence. The minor amount of microbialites in the coralligenous compared to cave biostalactites could derive from the abundance of sponges that compete with carbonatogenic bacteria for the same cryptic spaces. The sharing of a similar relationship between sponges and microbial communities by coralligenous concretion and biotic crusts of particular submarine caves suggests that this competition is not habitat-specific. On the contrary, it may develop in a range of environmental settings, from open to cryptic systems, and could be used to clarify the role of metazoans vs microbialites in palaeoecological reconstructions.
Abstract The Atlantic‐Mediterranean polychaete Sabellaria spinulosa (Leuckart, 1849) lives in agglutinated tubes forming discrete reef‐like bioconstructions on shallow‐water bottoms beaten by waves where sediment particles are constantly resuspended. Tubes are built with sand grains glued by a proteinaceous cement. Analyses of a S. spinulosa reef sample of this worm collected off the Casarza coast (central Adriatic Sea) allowed the description of its tube architecture and gluing modality. The tube consists of three layers of agglutinated sand: (a) a thin inner layer with sandy particles arranged side by side with a flat side facing the tube lumen (b) a thick middle layer with larger isodiametric and squat grains with empty pores in between; and (c) a thin discontinuous outer layer of heterometric clasts, prevalently large and flat, diverging towards the opening. This fits the general tube construction known for S. alveolata and in general for tubes of the sabellariidae family, but compared to Sabellaria alveolata , S. spinulosa possesses a smaller tube with a wall about 1/3 thick; the agglutinated sandy elements are finer, and some number of muddy particles participates in the tube construction. Morphological and epifluorescence observations revealed that biocement portions are irregularly and haphazardly distributed compared with those of S. alveolata that consist of drops and strips of glue carefully placed. Adjacent tubes leave empty interspaces in between them only locally filled by loose sand, extremely reduced to absent in S. alveolata .
RIASSUNTO - Il Calcare di Base costituisce la formazione carbonatica che prelude ai sedimenti evaporitici depositati nell’area mediterranea durante il Messiniano. Non sono ancora chiare le cause che hanno determinato questo significati vo evento. Lo scopo del presente lavoro e quello di riconoscere le principali microfacies che caratterizzano questi depositi nell’Italia meridionale e fornire modelli deposizionali coerenti con i dati sperimentali. Sono state studiate le microfacies del Calcare di Base affiorante in alcune localita della Calabria (Cropalati, San Donato di Ninea, Lattarico e Mendicino) e della Sicilia (Serra Pirciata e Marianopoli). La ricerca e stata sviluppata tramite osservazioni in microscopia ottica ed elettronica (SEM), per la definizione delle micromorfologie, ed analisi alla microsonda EDS, per la caratterizzazione mineralogica e l’individuazione degli elementi minori. Sono state effettuate anche osservazioni in epifluorescenza per l’individuazione di resti di materia organica. La microfacies dominante e costituita da micrite peloidale, con peloidi di dimensioni variabili che formano grumi a tessitura antigravitativa. I peloidi di dimensioni maggiori (50 µm - 500 µm) hanno forma cilindrica/subcilindrica e appaiono piu scuri. La forma, la composizione mineralogica, le dimensioni e il contesto sedimentario permettono di interpretare tali peloidi come fecal pellets. Le osservazioni al SEM ad alto ingrandimento hanno messo in e videnza due tipi di fecal pellets: quelli costituiti prev alentemente da particelle silicoclastiche e quelli contenenti modelli esterni di coccolitoforidi ed una piccola componente terrigena. L’origine biotica della microfacies peloidale e confermata dalle osservazioni in epifluorescenza che indicano un alto contenuto in materia organica. Sono state individuate due ulteriori microfacies molto meno frequenti: 1) detritica e 2) microbialitica/stromatolitica. Nel Calcare di Base del Bacino di Rossano l’evidenza dell’attivita biologica, le microstrutture primarie, l’assenza di tracce di minerali evaporitici e la presenza di coccolitoforidi nell’ambiente deposizionale, farebbero escludere sia una deposizione evaporitica sia un’origine diagenetica su solfati di calcio. Infine la notevole uniformita della biofacies trombolitica in tutti gli affioramenti studiati indicherebbe un evento paleoecologico, forse non sincrono, preludio in tutta l’Italia meridionale della Crisi di Salinita Messiniana. PAROLE CHIAVE: microfacies trombolitica; peloidi; coproliti; Calcare di Base; Messiniano; Italia meridionale.
The Late Miocene successions of the Capo Vaticano-Monte Poro (Southern Italy) area, well exposed at Cessaniti – Cava Gentile, preserve a palaeontological record particularly relevant for phylogenetic studies and paleogeographic reconstructions as well as for the popular scientific divulgation and museology. The rich record of Sirenians highly contributed to the knowledge of phylogeny and intraspecific variability of Metaxytherium serresii. The exclusive terrestrial mammal association, having African and Greco-Iranian affinities, allows intriguing suggestions in the paleogeography of the Central Mediterranean. New taphonomic analyses on invertebrates and vertebrates, here presented, suggest that the good fossil preservation is due to the rapid burial of skeletons in a semipermeable mixture of sandy/muddy sediments which were quickly cemented. Late partial dissolution of the carbonate cement among particles made the fossils easy to extract from the sediment. The collaboration among palaeontology researchers, fossil collectors, and local administrators, under the direction of Superintendence and the control of Carabinieri Command for the Protection of Cultural Heritage, allowed the recovery, study, and promotion of this precious paleontological record. The area has a good flow of tourists for the pleasant seaside, and fossiliferous sites could attract cultural tourism, through educational trails and a museum network which valorize the palaeontological and archaeological heritage of the hinterland.
Alla base di un complesso di scogliera del Messiniano affiorante nella Penisola Salentina e stata rilevata la presenza di una particolare associazione a vermetidi e microbialiti.Le osservazioni in affioramento hanno permesso di distinguere due facies: una inferiore, rappresentata da sottili colonizzazioni a vermetidi in posizione di vita, ed una superiore costituita da depositi clinostratificati con gusci di vermetidi isoorientati.L'analisi delle microfacies (SEM, EDS ed epifluorescenza) hanno messo in evidenza due tipi di micrite: una microbialitica, la cui deposizione in situ e stata indotta dal degrado della materia organica (che prevale nei depositi isoorientati), e l'altra detritica (che prevale nelle colonizzazioni in situ).Questi dati hanno permesso di riconoscere due fasi deposizionali: in un primo momento si avrebbe la colonizzazione del substrato da parte della comunita a vermetidi, accompagnata dalla deposizione di micrite di origine detritica. In un secondo tempo, fenomeni di risedimentazione porterebbero alla morte dei vermetidi e alla isoorientazione dei relativi gusci, accompagnate dalla deposizione di micrite di origine microbica.
