Simone Fabbi

A new 1:10,000-scale geological mapping of the Fiastrone Gorge (Northern Apennines), provides a revised interpretation of its Jurassic palaeogeographic and tectonic evolution. The Meso-Cenozoic evolution of the Umbria–Marche succession, exposed in the area, was controlled by the complex palaeogeography inherited from Early Jurassic rifting of the Western Tethys. At the eastern margin of the gorge, the Sibillini Mountains Thrust places the Calcare Massiccio over the Scaglia Cinerea, with intervening duplexes of Jurassic–Cretaceous pelagic units. Previous studies interpreted the area as a Jurassic structural high capped by a condensed pelagic succession, but new field data demonstrate that the contact between the Calcare Massiccio and the overlying Jurassic units is a complex unconformity, characterised by pervasive silicification of the Calcare Massiccio, with no evidence of any condensed succession. The upper Bajocian–lower Kimmeridgian Calcari Diasprigni represents the youngest unit burying the structural high, indicating a modest palaeorelief compared to other highs in the Umbria–Marche Domain. The Jurassic high displays a cusp-shaped geometry rather than a flattopped pelagic carbonate platform. Miocene normal faults displaced parts of the high prior to compression. Structural restoration suggests that the thrust may have reactivated a pre-existing Jurassic extensional fault, likely bounding a broader structural high to the east.

In this study we describe two newly identified isolated teeth of hybodontiform shark-like chondrichthyans from the Middle Jurassic deposits of the Umbria-Marche-Sabina (UMS) Domain in the Apennines, Italy. The specimens, identified as Strophodus sp. and Acrodus sp., contribute to the sparse fossil record of marine vertebrates from this region, particularly within the unique Jurassic PCP-basin environments. The Strophodus specimen (MUST NS.169.12) exhibits a robust crushing morphology characterised by a reticulated occlusal surface, indicative of the durophagous feeding adaptation of the genus. The Acrodus specimen (MUST NS.169.13) possesses a transverse crest and radial ridges, with a general morphology compatible to an anterior tooth position. Microfacies analysis of the embedding sediments attributes both specimens to the Aalenian–lower Bajocian interval. These finds mark the first documented occurrence of Acrodus in the Apennines and the first Middle Jurassic record of the genus in Italy. The paleoenvironmental context suggests that these hybodontiform shark-like chondrichthyans inhabited shallow marine settings rich in benthic invertebrates, which aligns well with their durophagous diet. Their presence enhances our understanding of marine vertebrate diversity within the UMS Basin and helps us to improve our knowledge of the ecological dynamics of the peculiar Jurassic Pelagic Carbonate Platform-Basin ecosystems.

While the effects of OAEs are well known for the pelagic successions of the Tethys Ocean, little is known about their impact on the Peri-Tethyan shallow water carbonate systems. Here we present the preliminary results of a study related to the geological mapping of the sheet 390 – Frosinone of the Geological Map of Italy (CARG Project), focussed on the identification and description of the perturbation induced in the Lower Cretaceous shallow water carbonate succession of the Latium-Abruzzi Carbonate Platform by the well-known Early Cretaceous Oceanic Anoxic Events (OAEs).In the Ernici Mts. (central Apennines, Italy), an Upper Triassic to Upper Cretaceous shallow-water carbonate succession is exposed (Cosentino et al., 2010; Fabbi et al., 2023). This study specifically examines the Lower Cretaceous "calcari ciclotemici a gasteropodi" fm. (CCG - Berriasian p.p. - lower Aptian p.p.), which mainly consists of whitish limestones with intercalations of light grey dolostones. Within this succession, a layer of black dolostone, about ten centimetres thick, has been observed in several outcrops of the dolomitic lithofacies (CCGa) of CCG, at the same stratigraphic position.Two stratigraphic sections were measured to characterise the microfacies and compositional variations observed between the light-coloured (whitish to light grey) and black layers. SEM images, along with Energy-Dispersive X-ray Spectroscopy (EDS) and Wavelength-Dispersive X-ray Spectroscopy (WDS) analysis indicated the presence of siderite and pyrite aggregates (Meng et al. 2024). These aggregates appear in high concentration starting from the basal part of the blackish dolostone layer and gently decrease towards the upper part of the study interval. TOC and sulphates show similar trends.Changes in chemical composition between the whitish and blackish dolostones (CCGa) were investigated in situ using the laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) facility at Roma Tre University. The results show a significant increase in elemental concentration of P, Fe, Zn, As, Ba, Pb, and U, as well as in the Fe/Al ratio in the blackish dolostones. These elements are generally considered as redox-sensitive proxies associated with anoxic paleoenvironments (Bodin et al., 2007; Craigie, 2018).Biostratigraphic calibration performed on the collected samples has established a Hauterivian p.p. age for the investigated CCGa levels. A preliminary attempt for U-Pb dating of the CCGa black dolostone was carried out through LA-ICP-MS investigations at Roma Tre and ETH facilities. In the Tera-Wasserburg diagram, the U-Pb measurements on CCGa black dolostone yielded a lower intercept age of 125.7± 1.8 Ma (MSWD=1.6; N=19). These promising results suggest that the changes in the elemental concentration of the redox-sensitive proxies observed in the CCGa black dolostone were induced by the late Hauterivian Faraoni Oceanic Anoxic Event.

This study investigates seven stratigraphic sections within the Umbria-Marche and Longobucco Basins, with a primary focus on the biostratigraphy and sedimentology of the Toarcian stage. Biostratigraphic correlation was conducted using the standard Tethyan and Mediterranean ammonite biozonations, revealing fully comparable faunal assemblages across the analyzed stratigraphic sections. In the Umbria Marche Domain, the Emaciatum Zone of the upper Pliensbachian occurs within pelagic limestone of the Corniola, and occasionally into the marly/clayey facies of the Marne di Monte Serrone. Conversely, the Emaciatum Zone at Caloveto is in a shallow-water carbonate facies. The passage from the Emaciatum to the Polymorphum Zone falls within a transitional formation boundary when it occurs between the Corniola and Marne di Monte Serrone, while it is abrupt and often marked by a hard-ground between the Corniola and Rosso Ammonitico. At Caloveto, the Pliensbachian-Toarcian boundary is marked by a hiatus extending to at least the Polymorphum Zone, while the Serpentinum Zone, is documented in the literature. Above the Polymorphum Zone, the T-OAE occurs as a black shale horizon or, in its absence, is distinguished by a marked faunal turnover passing in the Serpentinum Zone. The Bifrons Zone occurs within nodular marly limestones, exhibiting an upward increase in CaCO3 content. Notably, the Marne di Monte Serrone are often heteropic with the Rosso Ammonitico in the lower Toarcian. Sedimentation becomes increasingly calcareous at the Toarcian/Aalenian boundary, coinciding with the first appearance of chert.

Submarine palaeo-escarpment tracts at the basin margins commonly border isolated drowned carbonate platforms in the Jurassic rifted margins of the Western Tethys and bear fundamental structural and palaeogeographic significance. These tectonically generated escarpments, rooted in late Hettangian-early Sinemurian master faults, provide key information on the regional architecture of the rift, and on the nature and timespan of activity of the faults which define them. An isolated drowned carbonate platform (the Sabina Plateau) in the Northern Apennines of Central Italy exhibits a wealth of peculiar details on the Jurassic submarine topography. The deposits covering this escarpment host multiple unconformities related to a margin-failure episode, documented by breccias resting on a submarine-scar surface, perched with respect to the basin bottom and draped discontinuously by condensed ammonite-rich pelagites. Thin lenses of graded and laminated oolitic limestones in the condensed pelagic succession of the Sabina Plateau are interpreted as likely produced by the overbanking of turbidity currents, which were shed into the basin by a neighbouring productive carbonate platform. The final leveling of the submarine rift bathymetry occurred in the earliest Cretaceous, as documented by the onlap of the aggrading basinal succession against the palaeo-escarpment, and the burial of the plateau-top condensed succession. This complex onlap surface exhibits a distinctive overprint, such as diffuse silicification driven by the transit of silica-rich diagenetic fluids sourced by the radiolarian-rich basinal units.

During the sampling of a stratigraphic section along the shore of the Fiastra Lake (Carg Project - Sheet 313 “Camerino” of the Geological Map of Italy at 1:50 000 scale), a small rock boulder with partially exposed bony material was discovered at the base of a small cliff at the northern termination of the Sibillini Mts. In this area, the classical facies of Umbria-Marche stratigraphic succession are well exposed. The Oligocene-Miocene portion of the succession is represented by the ~200 m-thick Scaglia Cinerea Formation, passing upwards to the ~100 m-thick Bisciaro Formation. The microfossil assemblage has allowed the specimen to be constrained to the lower Burdigalian. The skeletal remains were examined using a CT-SCAN, a non-invasive method that has proven to be highly performing. The analysis revealed some articulated vertebrae, deformed by lithostatic compaction, which are attributed to a shark of the Order Lamniformes. Subsequently, the vertebrae were digitally isolated, extracted from the surrounding matrix, and rendered into three-dimensional prints. Through digital retro-deformation, the body length of the lamniform shark was estimated to be approximately 4 metres. Further considerations on the vertebrae allowed us to infer that the studied shark had similarities to either Isurus oxyrinchus Rafinesque, 1810 or Carcharodon carcharias Linnaeus, 1758. The development of a dead-fall microbial community likely facilitated the preservation of the vertebrae. The studied specimen represents the first occurrence of a lamniform shark in the Lower Miocene of the Umbria-Marche Domain and represents one of the very rare recorded occurrences of lamniforms from the Lower Miocene of Italy.

The San Potito area in central Apennines (Italy), enclosed within the Latium‐Abruzzi carbonate platform, exposes anomalously pelagic carbonates filling an intraplatform basin formed during Jurassic rifting. Oriented obliquely to the regional NW‐SE trend of Cenozoic thrusts and extensional faults, the basin's eastern boundary fault system, striking N‐S, played a pivotal role in structuring orogenic and post‐orogenic features. Large tracts of the fault experienced double reactivation: positive inversion during Miocene shortening, and negative during post‐orogenic extension. Double reactivation is evidenced by older‐on‐younger extensional contacts, and by the change in orientation of thrusts and recent extensional faults from NW‐SE to NNW‐SSE, the latter being consistent with the trend of Jurassic rift‐related structures of the area. This structural interplay highlights the importance of Jurassic faults and their ability in forcing the structural trends, by surviving across multiple deformation stages, even controlling active extensional seismicity.

The geological map of the Bagnoli-Agnano reclamation area was produced by Bonaventura Montani in 1856 with the purpose to assist in the reclamation project of the Agnano Lake area, which was plagued by unhealthy conditions and endemic malaria. The Phlegraean Fields are a volcanic region renowned for its susceptibility to cataclysmic events and high population density, which major eruptions took place approximately 39,000 and 14,500 years ago. Montani provided information about the nature of the volcanic rocks and the previous existence of marine deposits in the Bagnoli plain, excluding the presence of peat deposits in the underground, also through the drilling of seven geognostic boreholes. Based on geological observation, Montani proposed an optimal route for the drainage channel of Agnano Lake, thereby avoiding the challenging task of perforating the trachitic lava bodies of Accademia and Monte Olibano. He demonstrated that the diffuse gas emissions in the region had a volcanic origin and were not the primary cause of illnesses among the local peasants, which he related to the fermentation of plants processed on the shores of Agnano Lake. The reclamation of the Agnano Lake area was subsequently completed in 1870 after the Unification of Italy.