Rosso Ammonitico Research Articles

Radiation protection and natural building materials in cultural heritage

IntroductionBuildings that constitute cultural heritage and that are the identity of a defined geographical area are increasingly being restored to offer the community historical places to enjoy. Often the restoration preserves the original structure and building materials, which are usually natural stones. In this study, a radioprotection protocol dedicated to this kind of built environment was proposed and validated.MethodsAfter identifying the two predominant types of building material stones (Rosso ammonitico and Pietra Serena), radiometric measurements for natural gamma-emitting radionuclides (Ra-226, Th-232, and K-40) and measurements of the emanation coefficient and calculation of the exhalation rate of radon gas were carried out.ResultsThe two types of stone have a content of natural radionuclides that do not exceed the levels recommended by the regulations. The difference between the two types of stone is of an order of magnitude indicating that the red ammonite has a greater radiological impact than the pietra serena.DiscussionThe results, in addition to ensuring the radioprotection of the population, highlighted the need to increase the number of this kind of investigations to implement scientific knowledge and serve the stakeholders involved.

OF HIS BONES ARE CRINOID MADE: TAPHONOMY AND DEADFALL ECOLOGY OF MARINE REPTILES FROM A PELAGIC SETTING (MIDDLE-UPPER JURASSIC OF NORTHEASTERN ITALY)

Modern cetaceans are considered the best anatomical and ecological analogue for many Mesozoic secondary aquatic reptiles. Such similarities extend also after the death of these phylogenetically distant amniotes, when the sinking and decomposition of large carcasses in marine environments (deadfalls) follow common biostratinomic processes. Most taphonomic studies on Mesozoic deadfalls have been limited to shallow-water settings, often neglecting deeper waters. Here we provide a detailed taphonomic survey of ichthyosaurs, pliosaurs and metriorhynchoids from the pelagic Middle-Upper Jurassic Rosso Ammonitico Veronese (RAV) of northeastern Italy. Our taphonomic revision of the RAV tetrapod record highlights a common poor state of preservation of the bones, often associated with abundant macrofossils, consistent with a prolonged exposure of carcasses on a well-oxygenated seafloor. For the first time we confirm the role of nautiloids as active mobile scavengers by means of tens of beak elements found closely associated with, or even piercing, the bones. Hexanchiform shark teeth are also found associated with the carcasses, supporting a distinctive deep-water mobile scavenging community. Echinoids, sponges and other bioeroders are identified as representative of the enrichment-opportunist stage, and a high concentration of belemnites is believed to be indicative of mass-spawning deaths in the surroundings of the carcasses. Abundant crinoids are recognized as part of the reef stage by colonization of the eroded bones. While some of our data deviate from previous Mesozoic reptile-falls from shallow-waters, they are consistent with findings at Recent whale-falls in bathyal zones, and overall represent a precious window into the complex ecology of Jurassic open seas.

The stone artifacts of the National Archaeological Museum of Adria (Rovigo, Italy): a noteworthy example of heterogeneity

This paper reports on the results of the analyses of 56 stone samples from Roman and pre-Roman artifacts from the ancient town of Atria, currently preserved at the National Archaeological Museum of Adria. The city is located in the eastern Veneto lowlands, close to the Po River delta, and far from the main rock outcrops of the region. The objective of this research is to determine the provenance of the stones used in ancient Atria and their trade networks. The analytical techniques adopted include polarized-light optical microscopy (PLM), X-ray fluorescence (XRF), and quantitative phase analysis by X-ray powder diffraction (QPA-XRPD). The results reveal a widespread use of imported stones from the central-western territories of Veneto, primarily comprising trachyte from the Euganean Hills and the soft limestone Vicenza Stone from the Berici Hills/eastern Lessini Mounts. Rosso Ammonitico, Maiolica (Biancone) and Scaglia Rossa limestones are also documented. From neighbouring regions, the imported stone types include Aurisina limestone from the Trieste Karst and Istrian Stone. Sandstone was uniquely recognized in G. Popillius’s milestone. Moreover, advanced geochemical and mineralogical analyses performed on the Euganean trachytes allow tracking accurately the quarry sites, revealing an extensive exploitation of the main historical quarries of M. Oliveto, Monselice and M. Merlo, although some provenances from outcrops less systematically exploited were also detected. Notably, the use of rhyolite for manufacturing a pre-Roman gravestone provides new insights regarding the exploitation of Euganean stone resources before the Roman era.

Middle Jurassic syn-sedimentary tectonics and palaeoenvironmental evolution in the eastern part of the Alborz Mountains (N Iran)

The facies variations in the Middle Jurassic deposits of northern Iran (northeastern Neotethys) were studied in two stratigraphic sections (Tapal and Kalariz) in the eastern part of the Alborz Basin to reconstruct the palaeoenvironmental evolution in this region. Six different palaeoenvironments were recognized based on alternation of sedimentary facies in the four formations of the studied sections (upper part of the Fillzamin, Dansirit, Dalichai and lower part of the Lar formations). The upper Fillzamin Formation (lower Bajocian) records a gradual shallowing-upward sequence from seaward to landward margin of a prodelta environment in the study area. This shallowing trend terminated with the Mid-Cimmerian tectonic event and unconformity, which is characterized by a thin limonite layer at the base of the Dansirit Formation in the Tapal section. The Dansirit Formation (lower upper Bajocian) represents heterolithic marginal marine, sand and gravel bars and terrestrial environments. The subsequent deposits of the Dalichai Formation (upper Bajocian–Callovian) represent a deepening sequence, which is associated with the appearance of pelagic strata and ammonitico rosso facies in the upper part of the formation. The ammonitico rosso facies, which is related to the development of pelagic swells in the rift basin, gives direct evidence of an extension phase and presence of a swell/trough system in the region. The rifting and subsidence are attributed to the opening of the South Caspian Basin (north of the Alborz region). The lack of correlation between the sea-level changes recorded by the upper Bajocian strata of the sections and the long-term eustatic sea-level changes suggest tectonic influence on the facies variations and sea-level fluctuations in the Alborz region. From the upper Bajocian upwards, a deepening trend in the studied sections can be correlated with the global sea-level changes, while tectonic (rifting and subsidence) overprinted the eustatic sea-level rise.

STRATIGRAFIA DEL GIURASSICO DEI DINTORNI DI FOZA (ALTOPIANO DI ASIAGO)

The Middle and Upper Jurassic sequence near Foza (Asiago plateau; Venetian Alps) is characterized by important hiatuses. The relevant deposits are furthermore often found as sedimentary dikes, filling up fractures in the underlying carbonatic platform of the Calcari Grigi, Middle Liassic in age in the uppermost levels. The normal Middle and Upper Jurassic sequence includes, aver the Calcari Grigi the following formations: Lower Rosso Ammonitico Veronese and "Lumachella a Posidonia alpina", both Middle Ju­rassic in age; "Scisti ad Aptici", Upper Rosso Ammonitico Veronese and the basal part of the "Biancone", Upper Jurassic in age. In the Foza area the stratigraphic sequence changes quite rapidly in very short distances, with hiatuses involving one or more of the above mentioned formations. The presence of these hiatuses and of sedimentary dikes is in agreement with the location of the studied area near the edge of the "Trento plateau" during the Jurassic. A fossil assemblage was collected from a sedimentary dike near Lazzaretti of Foza. It consists of Brachiopods, Belemnites, Bivalves and Crinoid remains. Brachiopods are prevailing both in specimens and species number; among them 6 species, even if generally poorly preserved have been determined and described.

Palynological evidence for the Middle Jurassic environmental evolution in the eastern part of the Alborz Mountains (northern Iran)

The palynological assemblages of the Dalichai Formation were studied to reconstruct the paleoenvironmental evolution of the Middle Jurassic interval in the eastern part of the Alborz Mountains (N Iran). Dinoflagellate cyst biozones, planktonic foraminifera, and ammonites suggest a Bajocian-Callovian age for the Dalichai Formation. The palynodebris, mostly of terrestrial origin, are dominated by black opaque phytoclasts. Dinocysts, spores, pollen grains, and amorphous organic matters (AOM) are minor components in most samples. Terrestrial palynoflora are mainly represented by coastal gymnosperms (Araucariaceae, Cheirolepidiaceae), lowland simple monosulcate pollen producers (Cycadales/Bennettitales), ferns, upland seed ferns and conifers (Corystospermales and other bisaccate pollen producers). These assemblages indicate a warm climate with seasonally-dry conditions. However, an increase in Cheirolepidiaceae (Classopollis) in Bathonian assemblages reflects higher temperature during this interval. The dominance of the land-derived phytoclasts and presence of brackish water Botryococcus colonies with cells arranged irregularly suggest a proximal setting with high terrestrial and freshwater input during the Bajocian. The palynofacies analysis suggests a sea-level rise during the Bathonian, reflected by higher abundance and diversity of dinocysts as well as the presence of degraded small phytoclasts. This transgression phase is related to the increased subsidence of the Alborz region due to ongoing Neotethys subduction and creation of a large extensional back arc basin in the Eurasian margin. The syn-rift deposits are characterized by ammonitico rosso facies as well as hemipelagic carbonates containing planktonic foraminifera and pelagic bivalves.

Dead, discovered, copied and forgotten: history and description of the first discovered ichthyosaur from the Upper Jurassic of Italy

In 2017 attention was brought back to the specimen V7158 from the Verona Natural History Museum. The fossil is a small fragment of an ichthyosaur rostrum discovered in the XIX century in the Verona territory (northeastern Italy) representing one of the first findings of Ichthyosauria in Italy. The specimen, after long oblivion, was re- discovered in the 1990s but until now was never officially described. In this paper we provide morphological analysis, taxonomic attribution, taphonomic analysis and age determination to V7158 as well as a detailed reconstruction of the peculiar history of this discovery. From our re-description, V7158 can be doubtfully attributed to Ophthalmosauridae and firmly assigned to the Tithonian. Age determination and the recognition of the source formation (Rosso Ammonitico Veronese, RAV) were achieved by means of calcareous nannofossils associated with the matrix of V7158 and through fieldwork activity in the area of discovery. Though fragmentary, the specimen is histologically very well preserved, a feature unusual for the taphonomic regime of the RAV and most likely restricted to its upper unit.

The “Belemnitico rosso” facies in the East Balkan – a proposal of lithostratigraphic formalization

Lower Jurassic fossil-bearing red limestone with abundant belemnite rostra is exposed in the form of olistoliths included in the Middle Jurassic Kotel Olistostrome Formation in the surroundings of the town of Kotel in the East Balkan. Following the widely recognized Tethyan “ammonitico rosso” facies, we propose to formalize this distinctive red fossiliferous level as a lithostratigraphic marker under the name “belemnitico rosso”. This will contribute to the creation of attractive geosites of scientific and educational value with great interpretive potential for public understanding of science, as well as “ex situ” geodiversity elements used as building stones in construction. The creation of original geotourism products under the brand name of the future “East Balkan” Geopark seeks to make geology accessible to all. It is quite possible that someday, the new term will gain widespread popularity and will bring awareness to the geopark where it was first defined.

Tough to digest: first record of Teleosauroidea (Thalattosuchia) in a regurgitalite from the Upper Jurassic of north‐eastern Italy

AbstractPostcranial remains of a small teleosauroid from the Upper Jurassic of north‐eastern Italy are described in detail. The specimen, discovered in 1980 on a slab of Rosso Ammonitico Veronese (RAV Fm.; Bajocian–Tithonian), is represented by partially articulated thoracic, sacral and anterior caudal vertebrae, fractured and displaced osteoderms and pelvic girdle elements. Additional bone elements overlap one another in a densely packed cluster. The peculiar arrangement of this specimen is here interpreted as the result of regurgitation of the animal carcass from a pelagic predator or scavenger. Microstructural and geochemical evidence from bone and surrounding matrix support this hypothesis. A dearth of phosphorus in the matrix near the bone mass corroborates the interpretation of the specimen as a regurgitalite rather than a coprolite. Calcareous nannofossil and stratigraphic data allow us to assign the fossil to the latest Kimmeridgian or earliest Tithonian. The specimen is here tentatively referred to the teleosauroid subfamily Aeolodontinae based on the alternating pattern of the osteoderm ornamentation; this attribution is supported by stratigraphical and palaeoenvironmental evidence. If confirmed, this represents the first occurrence of Aeolodontinae in Italian outcrops of the western Tethys margin and represents the first marine crocodylomorph described as a bromalite.

Uppermost Triassic Halstätt-like cephalopod limestone (Lilu Facies) and Foraminifera, Timor-Leste

Ammonoid-rich wackestone beds forming a ca 2 m section between shallow-marine limestones of the Bandeira Group (Norian to possibly Rhaetian) and a wackestone–calcareous mudstone succession belonging to the Lower Jurassic Wailuli Group are recorded from the western part of Timor Leste. They are included in the Halstätt-like Lilu Facies of the Bandeira Group. Age-diagnostic involutinid foraminiferal species, not previously recorded from Timor, include Involutina liassica, Trocholina sp. ex. gr. Trocholina turris and Lamelliconus permodiscoides, which collectively indicate a Rhaetian age, possibly ranging down to the Sevatian. The conodont Norigondolella steinbergensis, recorded low in the section, is consistent with this age determination. The Lilu Facies was deposited at a water depth of a few tens of metres, as suggested by the presence of extensive cyanobacterial borings into shell fragments and the presence of microbial laminations including the presence of stromatolites and bacinellid-like fabrics. Among macrofossils, common ammonoids are present in the section, and marine reptile bones are conspicuous in the lower beds. Other biogenic components of the rock observed in acetate peels and thin sections are abundant echinoderm debris (including pentacrinoid columnal plates), bivalve fragments and micro-gastropods, rare siliceous sponge spicules, solitary corals, and brachiopod debris. In the studied region, a major drowning of a shallow-marine carbonate platform took place probably in the Rhaetian or possibly latest Norian. Similar ‘ammonitico rosso limestone’ interbedded with thick-bedded limestones of a shallow-marine carbonate platform is present in the uppermost Triassic of Seram. More detailed biostratigraphical comparisons and correlations of similar units in Timor and other nearby islands may indicate a general marine drowning of Late Triassic carbonate platforms, at least in the northern part of the East Gondwana Interior Rift system, during the Rhaetian or possibly latest Norian.

The chemostratigraphy and environmental significance of the Marlstone and Junction Bed (Beacon Limestone, Toarcian, Lower Jurassic, Dorset, UK)

AbstractTwo fallen blocks of the Marlstone and stratigraphically overlying Junction Bed sampled on the beach below Doghouse Cliff in Dorset, UK (Wessex Basin) have been examined for carbon and oxygen isotopes of bulk carbonate as well as for strontium, carbon and oxygen isotopes and Mg:Ca ratios in the contained belemnites. The sequence, which contains most of the Toarcian zones and subzones within a metre or less of grey to yellow to pink, red and brown fossil-rich nodular limestone, is extremely condensed and lithologically similar to pelagic red limestones of the Tethyan Jurassic that are locally mineralized with Fe-Mn oxyhydroxides (e.g., Rosso Ammonitico). Strontium-isotope ratios of the contained belemnites are compatible with existing reference curves and both blocks show a rise to more radiogenic values post-dating the Pliensbachian–Toarcian boundary. The high degree of correlation between the relatively negative carbon and oxygen isotopes of the bulk carbonate is compatible with significant diagenetic overprint, and contrasts with higher carbon-isotope values in coeval condensed coccolith-rich limestones elsewhere. Evidence for the characteristic signature of the Toarcian Oceanic Anoxic Event, as represented by organic-rich sediment, is absent, possibly owing to a stratigraphic gap. Both blocks exhibit abrupt carbon-isotope shifts to lower values, one of which could represent the limbs of an incompletely recorded negative excursion associated with the Toarcian Oceanic Anoxic Event. That the Toarcian Oceanic Anoxic Event was also a significant hyperthermal is illustrated in both blocks by a drop in oxygen-isotope values and rise in Mg:Ca ratios of belemnites close to the base of the Junction Bed in the lowest part of theserpentinumzone.

Petrographic and geochemical characterization of the Middle\u2012Upper Jurassic Fe\u2013Mn crusts and mineralizations from Monte Inici (north-western Sicily): genetic implications

Fe–Mn concretions and mineralizations, associated with condensed horizons and hardground, are significant archives in ancient carbonate rocks. Their petro-chemical study allows an assessment of the palaeoenvironmental context in which they were formed also connected to their biotic or abiotic origin. At the western side of the Monte Inici (Fornazzo section, north-western Sicily) a well exposed outcrop of condensed pelagic limestones (Rosso Ammonitico facies: Middle‒Upper Jurassic) is well-known and thoroughly studied. In this section, the base of the Rosso Ammonitico facies consists of a very condensed level rich in fossils with a variable thickness deposited from the early Bathonian to the early/middle Callovian. It is characterized, at the top, by the noticeable presence of Fe–Mn concretions, typical of the Tethyan Jurassic and related to very low sedimentation rates. For this study, Fe–Mn crusts and mineralizations from the Fornazzo section were investigated using X-ray diffraction, scanning electron microscopy, X-ray fluorescence, ICP and stable-isotope mass spectrometry. The collected samples, deposited in submarine conditions (as testified by stable oxygen and carbon isotopes), have been subdivided in two typologies with different macroscopic and mineralogical features. The Fe–Mn crusts consist of hematite, todorokite and birnessite and are characterized by a relatively low Mn/Fe ratio. Their content in trace elements, rare earths and yttrium (REY) is compatible with a hydrogenetic origin involving the oxy-hydroxides colloids precipitation directly from seawater. Microbially mediated processes are here testified by the recognition of filamentous and coccoid-shaped microstructures referable to coexistence of chemosynthetic fungi and photosynthetic cyanobacteria and accounting for a deposition in the deep euphotic zone. An average growth rate of ~ 8.5 mm/Myr for the Fe–Mn crusts, estimated by cobalt concentrations, suggests a time elapsed for deposition of ~ 3.5 ± 1 Myr. This value is compatible with the stratigraphic gap embracing the time span from the early/middle Callovian to the middle Oxfordian. In the neighbouring pelagic limestones, Fe–Mn deposits are present in the form of micro-dendrites mainly consisting of pyrolusite, sometimes associated with carbonato-fluorapatite. The geochemical composition gives evidence of a prevalent early diagenetic origin with precipitation, at the sediment/water interface or in the first centimeters of sediments, of metals diffused from the crusts as consequence of fluctuating redox conditions. Although the well-preserved Frutexites texture is commonly related to a microbial activity, other bacterial microstructures have not been recognized, having probably been obliterated during the growth of the dendrites. Nevertheless, it is possible to suppose a deepening in the bathymetry consistent with the involvement of chemosynthetic microorganisms in the formation of Frutexites structures.

Late Triassic to Early Jurassic radiolarian, conodont and ammonite assemblages from the Tavuscayiri block, Mersin Mélange, southern Turkey: Time constraints for the T/J boundary and sedimentary evolution of the southern margin of the northern Neotethys

The Mersin Mélange (northwest of Mersin city) includes a variety of large sedimentary blocks/tectonic slices of Palaeozoic and Mesozoic origins. Of these, the latter represents facial and tectonostratigraphic counterparts of the Beysehir-Hoyran Nappes (remnants of the northern Neotethys). The Tavuscayiri Block, located at the center of the mélange and close to the Orbuklukeli hill, is one of such Mesozoic occurrences, with a continuous pelagic sequence from the Upper Triassic to Lower Jurassic. At the Orbuklukeli hill, a succession of middle Norian to Toarcian age has been precisely dated, which starts with conodont assemblages for the Norian and Rhaetian and includes radiolarians for the upper Rhaetian. An acidic tuff layer corresponds to the T-J boundary, which passes above to an increasingly dominating chert-bearing limestone series, marking a gradually deepening-upward of the sequence. The early Hettangian radiolarians are poorly represented, but diverse and well-preserved radiolarians have been retrieved from the middle Hettangian to the Pliensbachian. A total of eighty-five taxa, including fourteen new species, have been determined. In addition to these, one new genus (Praeudalia Tekin, n. gen.) has been described from the Rhaetian part of the section. The top of the section is represented by nodular limestones in Ammonitico rosso facies, including a diverse Toarcian ammonite fauna. All lithologies of the Orbuklukeli section along the Tavuscayiri Block can be correlated with the previously described lithologies of the Kayabasi Group/Formation in the Bozkir Unit, and Gülbahar/Gümüslü units in the Lycian Nappes.

Jurassic – Cretaceous boundary record in Carpathian sedimentary sequences

An integrated study of micro- and nannoplankton distribution, O and C isotopes and palaeomagnetic record of nine Carpathian sections provided a key interpretation tool to characterize the Jurassic–Cretaceous (J/K) boundary transition. Biostratigraphy supported by saccocomids, radiolarians, calpionellids, dinoflagellates and nannofossils helped to distinguish biostratigraphic zones which could have been correlated both with stable isotopes and with magnetostratigraphy. The Alpina Event (lorica size change) accompanied by Nannoconus wintereri and N. steinmannii minor FO's designates the J/K boundary.Sedimentary model in N Mediterranean Tethys margin consists of elevated blocks with slow (1–2 mm/ka) Rosso Ammonitico carbonate sedimentation separated by dysoxic depressions. Tectonic instability has been indicated by Upper Jurassic fluxoturbidites.Late early Tithonian (M21n to M20r) saccocomid abundance increases with positive δ18O isotope ratios, similar excursion between M20n and M19r accompanied late Tithonian crassicollarian boom. The δ13C variation (>0.2‰) confronted with microplankton quantity variations: positive excursion occurred both during early Tithonian Saccocoma sp., and during late Tithonian calpionellid and nannoconid blooms. Higher up in the Berriasian “Maiolica” sequence, lighter δ13C values prevailed.During late Tithonian (Praetintinnopsella-to earliest Crassicollaria zones; M20n1n to M19r), Saccocoma microfacies has been substituted by a calpionellid one. Reorganization of Tethyan oceanic currents during opening of the Hispanic corridor started planktonic carbonate particle „rain“ resulting in the Maiolica facies dominance. Sedimentary rate raised ten times. Calpionella alpina lorica size change event was synchronneous with FO's of Nannoconus wintereri and N. steinmannii minor and with negative δ18O trend of latest Tithonian (Colomi Subzone) warming. Expressiveness of eccentricity and obliquity cycles indicates climatic optimum conditions.

Geodiversity in Urban Cultural Spaces of Rio de Janeiro City: Revealing the Geoscientific Knowledge with Emphasis on the Fossil Content

Urban geotourism itineraries have increased in recent years, since a large number of people are living in major cities and the building stones of the historical and architectural monuments can be used for scientific dissemination. These routes also include information such as geology, palaeontology, architecture, history, tourism and environment. This work presents geoscientific information through a multidisciplinary approach, with emphasis on the fossil content in the building stones. The cultural spaces in the historical centre of Rio de Janeiro City studied are (1) Real Gabinete Portugues de Leitura, (2) Guitarra de Prata store, (3) Confeitaria Colombo, (4) Paco Imperial and (5) Centro Cultural Banco do Brasil (CCBB). This choice was based mainly on the presence of fossiliferous stones, the historical and cultural importance of this heritage and the easy access to the public. The fossils were found in Lioz limestone [Rudistas (Radiolites and Caprinula) (Sites 1, 3, 4 and 5), Gastropods (Sogdianella, Turritella, Pchelinsevia and Neoptyxis) and the ichnogenus Thalassinoides (Site 4)], in the Rosso Ammonitico limestone [Ammonoid Hildoceras and a small undetermined gastropod (site 2)] and in the stromatolitic metalimestone (Site 3). Both Lioz limestone and Rosso Ammonitico are originated from Portugal and Italy, respectively, so the only Brazilian fossil content recorded here is the stromatolites in metalimestone used in CCBB. The dissemination of geodiversity, especially the fossil content, present in these spaces can promote the geoscientific education and the urban geotourism with paleontological approach, attracting a wide public.

IL ROSSO AMMONITICO INFERIORE (BAIOCIANO - CALLOVIANO) NEI MONTI LESSINI SETTENTRIONALI (VERONA)

The aim of this paper is the description, from both the biostratigraphical and sedimen• tological point of view, Of the lower member of the Rosso Ammonitico Veronese, one of the most known red, nodular, pelagic limestones of the mediterranean Jurassic.
 The R.A.V. is a condensed sequence Of red, mostly nodular, limestones, Often rich in internal molds Of ammonites, which is areally restricted to the "Trento Ridge", a structural high isolated in the early Jurassic by the rifting Of a Triassic, large epicontinental carbonate—platform. It spans in age from late Bajocian to Tithonian and is separated from the underlying shallow—water carbonates Of Liassic and Aalenian age by a sharp break in sedimentation, underlined by a mineralized hard ground, which lasted for all early and middle Bajocian.
 Two members may bc recognized in the R.A.V.: a lower (Rosso Ammonitico Inferiore) and an upper one (Rosso Ammonitico Superiore) separated by a stratigraphic gap. The lower member, ranging in age from late Bajocian to middle Callovian, is well developed only in the southern part of the 'Trento Ridge" (i. e. in the Lessini Veronesi area) and has a variable thickness which reaches a maximum of 8 meters.

Mass-transport deposits from the Toarcian of the Umbria-Marche-Sabina Basin (Central Italy)

Mass-transport deposits (MTDs) intercalated in slope/basinal successions, produced by submarine collapses and mass flows, are generally constituted of allochthonous elements sourced from platform margins. Here we present a noticeable exception where Toarcian calciclastic deposits made of pelagic carbonate elements are embedded in other pelagic carbonates. Selected outcrops pertaining to the Rosso Ammonitico Fm of three different pelagic carbonate platform (PCP)-basin systems were studied. The pelagic successions of the study areas onlap Early Jurassic structural highs. These clastic bodies partially replace the typical Toarcian reddish marls and shales of the Umbria-Marche-Sabina palaeogeographic Domain at different stratigraphic levels. The clasts range from blocks to megablocks; extraclasts of Corniola facies (Pliensbachian) and, sporadically, of Calcare Massiccio peritidal carbonates (Hettangian) are associated with Rosso Ammonitico intraclasts.The internal architecture of the MTDs and their emplacement processes, as well as their source and accumulation areas, were identified. Three distinct lithofacies characterise the clastic bodies, each one corresponding to a different emplacement process or to a different portion of the flow. The occurrence of lithified megablocks (>20 m across) of Corniola Fm suggests the exhumation of the buried portion of the unit. Synsedimentary extensional tectonics is the most likely triggering mechanism.Sedimentological analysis, coupled with geological mapping of the study areas, reveals the key role played by PCPs in the genesis of these MTDs. The early Toarcian reactivation of Hettangian palaeofaults bounding the structural highs is inferred. These faults, characterised by moderate offsets, crosscut the onlap wedges of the hangingwall successions, exhuming the older and lithified portion of Corniola Fm. Once become inactive, the fault planes were then eroded producing palaeoescarpments. Their backstepping, coupled with seismic shocks, produced the accumulation of the study clastic bodies.

A revision of the diagnosis and affinities of the metriorhynchoids (Crocodylomorpha, Thalattosuchia) from the Rosso Ammonitico Veronese Formation (Jurassic of Italy) using specimen-level analyses.

Neptunidraco ammoniticus is a thalattosuchian crocodylomorph from the Rosso Ammonitico Veronese Formation (RAVF, Middle Jurassic) of northern Italy. Erected from one partial specimen, Neptunidraco is pivotal in reconstructing thalattosuchian evolution, being it the oldest known member of Metriorhynchidae. Two additional RAVF thalattosuchians have been referred to Neptunidraco. A revised diagnosis of N. ammoniticus is provided here. Using a well-sampled phylogenetic data set of Crocodylomorpha, the affinities of all three RAVF thalattosuchian specimens are investigated simultaneously for the first time using parsimony tree-search strategies and Bayesian inference using the Fossilized Birth-Death with Sampled Ancestor (FBDSA) model. The results of the alternative analyses are not consistent in the placement of the RAVF specimens. The holotype of N. ammoniticus is consequently referred to Metriorhynchidae incertae sedis. The first referred specimen is recovered in various alternative placements among Metriorhynchoidea. The third and most fragmentary specimen is recovered as a crocodylomorph of uncertain affinities in the parsimony analysis and in the undated Bayesian analysis, and a metriorhynchoid sister taxon of the second RAVF specimen in the tip-dated Bayesian analysis. Only a subset of the results in the parsimony-based analyses supports the referral of the latter two specimens to Neptunidraco. The unusually high rate of morphological divergence for the Neptunidraco branch, inferred in previous iterations of the Bayesian inference analyses but not recovered in the novel analysis, was likely an artifact of the a priori constraint of all RAVF thalattosuchians into a single taxonomic unit, and of the arbitrarily fixed tip-age priors for the terminal taxa. These results confirm the utility of specimen-level morphological analysis and of combined tree-search strategies for inferring the affinities and the inclusiveness of fragmentary but significant fossil taxa, and reinforce the importance of incorporating stratigraphic uncertainty as prior in tip-dated Bayesian inference analyses.

THE LOWER BAJOCIAN GAETANI LEVEL: LITHOSTRATIGRAPHIC MARKER OF A POTENTIAL OCEANIC ANOXIC EVENT

In this paper we document in detail the transition from the Rosso Ammonitico Lombardo to the Radiolarites outcropping at Alpe Turati (Albavilla, Como) in the Lombardy Basin of the Southern Alps. At this location, the Jurassic succession was deposited on a flank of the Corni di Canzo paleohigh: as found on other structural shallow areas, the upper Pliensbachian–Toarcian–Aalenian interval is represented by pseudonodular to nodular marly limestones of the Morbio Limestone and Rosso Ammonitico Lombardo units. In the early Bajocian deposition of biosiliceous sediments is ubiquitously testified by the Radiolarites (Bajocian–Callovian). At Alpe Turati, the interval immediately below the basal green member of the latter unit, consists of a 10 cm thick black shale, pointing to oxygen-depleted bottom waters. Dysoxia persisted during the Bajocian–Callovian as evidenced by dark green stratified cherts. Calcareous nannofossil biostratigraphy indicate an early Bajocian age for the black shale that correlates with the core of a distinct C isotopic negative anomaly also known in various basins outside the Southern Alps. Very dark grey to black lithologies of early Bajocian age have been documented in a few sections from Poland, Corsica and Morocco. We name Gaetani Level the black shale interval in recognition of Maurizio Gaetani’s pioneering and extensive work on Jurassic sedimentary successions of the Lombardy Basin. The association of the Gaetani black shale with a C isotopic anomaly suggests that it could be the sedimentary record of an Oceanic Anoxic Event whose regional to global extension must be ascertained.

Carbon-isotope stratigraphy and pelagic biofacies of the Middle–Upper Jurassic transition in the Tethys–Central Atlantic connection

A bulk carbon-isotope stratigraphy, based on high-resolution sampling of five stratigraphic ammonite-dated sections from pelagic swells of the Subbetic basin (External Zones of the Betic Cordillera, southern Spain) is presented. The studied sections are characterized by Callovian–Oxfordian stratigraphic successions located in the South Iberian palaeomargin, a key area connecting the Central Atlantic to the Tethys oceans. The rocks are mainly nodular limestones with common extreme condensation (rosso ammonitico facies). Discontinuities with hiatuses of variable duration, submarine “hardgrounds”, Fe-Mn ooids, limonite crusts, and neptunian dykes are observed around the Callovian/Oxfordian boundary. The stratigraphic record, although very time-averaged, allows for a consistent and accurate ammonite chronostratigraphy. The carbon isotopes of marine carbonates show a marked trend towards high δ13C values from Lower Oxfordian to the Middle Oxfordian (~4.3‰, near the Plicatilis/Transversarium boundary). The isotopic values stand between 2.7 and 3.0‰ at the Upper Oxfordian (Bifurcatus and Hypselum Zones) and lowermost Kimmeridgian (Bimammatum Zone); afterward δ13C values decrease and reach a relative minimum (~2.3–2.5‰) in the Lower Kimmeridgian (Bimammatum/Planula boundary). Finally, isotopic values increase again (~2.6–2.7‰) in the lower Kimmeridgian (mid part of the Planula Zone). Comparison of carbon-isotope stratigraphy between Subbetic and other Tethyan areas shows similar trends. The replacement of thin-shelled bivalves by planktonic foraminifers and radiolarians that took place in the Callovian/Oxfordian boundary can be associated to the widening of the trans-Pangaean seaway. This, in turn, triggered the global warming which increased nutrients concentration in upper water column due to intensified nutrient input by river plumes. These phenomena are concomitant with the major Oxfordian δ13C positive excursion and with a transgressive cycle.