Eastern Sardinia Research Articles

Geohazard features of the Eastern Sardinia

ABSTRACT The MaGIC project (Marine Geohazard along the Italian Coasts) had the aim of mapping the geohazard in the Italian seas and resulted in numerous maps. In this paper, we present the maps: ‘Maps of Geohazard features of the eastern Sardinian Margin’. The Eastern Sardinia margin has mainly a narrow shelf, which reaches a width of 20 km only to the north. At the base-of-slope, a series of intra-slope basins sits in the structural depressions formed during the opening of the Tyrrhenian back-arc system. Submerged, coastal depositional bodies are present in the Olbia area where the continental shelf is large. They most likely represent the remnants of coastal environments formed during the last rise in sea level. They can represent important geo-resources for application in the issue of coastal erosion management. They are also the site of ecosystems hosting a specific biodiversity, which need to be preserved. In the central and southern part of the mapped area, the shelf is very narrow with an average width of about 4 km. Here, many canyon heads are very close to the coastline. They develop through retrogadational processes. Particularly in those canyons, where the canyon heads reach the coast, sediment instability represents an important source of geohazards to the coastal regions.

Introduction of the South American slipper limpet Crepipatella dilatata in Europe: Secondary spread in the Northeast Atlantic and first records for the Mediterranean Sea

The slipper limpet Crepipatella dilatata, native to Chile and Argentina, was introduced in north-western Spain in 2005 and since then has spread to the Galician and Cantabrian coasts. In this work, we provide the first molecularly validated record of an established population of C. dilatata in central Portugal (Aveiro), and of reproductive individuals (i.e. brooding females) of C. dilatata in the Mediterranean Sea, from three Italian mussel farms (in eastern Sardinia and northern Adriatic). DNA barcoding and phylogenetic analyses based on mitochondrial markers indicate that limpets from Italian farms belong to the C. dilatata ‘clade1’, whereas limpets collected in Aveiro cluster within the C. dilatata ‘clade2’. All these limpets share the same COI haplotypes with introduced populations from Galicia. The arrival of C. dilatata to Europe is undoubtedly due to transoceanic live mussel trade from southern Chile to Galicia. Mussel trade and farming are also the most likely drivers for the post-border dispersal of C. dilatata from Spain to Portugal and to Italy. Several countries have a potential role as a hub for the primary and secondary dispersal of slipper limpets towards and within Europe. This calls the attention for future research focused on assessing the current occurrence and ecological impact of established populations of slipper limpets within and nearby mussel farms along the eastern Atlantic and Mediterranean coasts.

Social Organization, Intersections, and Interactions in Bronze Age Sardinia. Reading Settlement Patterns in the Area of Sarrala with the Contribution of Applied Sciences

Abstract Bronze Age sites in the coastal area of Sarrala, in Eastern Sardinia, have been subjected to survey and excavation over the last half-century. The study area, whose social and economic evolution and changing scales of interactions are traced through settlement patterns and building analysis, is interpreted in light of more general trends suggested by stable isotopes, archaeogenetics, and paleoclimatology. The local picture of progressive demographic growth and infilling of the landscape, with a subsequent concentration of population and labor, follows a sequence widely detected in Sardinia. More specific identifiable aspects include a comparatively higher fragmentation/competition (ratio of complex vs simple nuraghes; ratio of tombs vs nuraghes) and a consistent pattern in the distribution of non-local building materials in the latest phase at the sites showing archaic features, taken as a clue of a long-lasting authority at select sites. These elements are compatible with organized pastoral exploitation of the available territory, structured according to patrilocality and closeness to ancestral lineages and residences. The interplay of internal dynamics relative to constraints and opportunities is discussed, such as climate change and long-distance trade connections, with possible implications for interpreting Nuragic society.

The Endangered Sardinian Grass Snake: Distribution Update, Bioclimatic Niche Modelling, Dorsal Pattern Characterisation, and Literature Review.

The Sardinian grass snake, Natrix helvetica cetti, is an endangered endemic snake subspecies with a restricted and highly fragmented geographic distribution. Information on its ecology and detailed geographic distribution are scarce and may negatively impact on its conservation status. Therefore, a literature review on its taxonomy, morphology, ecology, and conservation is presented here. Moreover, field records from the authors, citizen science and the existing literature provide an updated geographic distribution highlighting its presence within 13 new and 7 historic 10 × 10 km cells. Bioclimatic niche modelling was then applied to explore patterns of habitat suitability and phenotypic variation within N. h. cetti. The geographic distribution of the species was found to be positively correlated with altitude and precipitation values, whereas temperature showed a negative correlation. Taken together, these outcomes may explain the snake's presence, particularly in eastern Sardinia. In addition, analysis of distribution overlap with the competing viperine snake (N. maura) and the urodeles as possible overlooked trophic resources (Speleomantes spp. and Euproctus platycephalus) showed overlaps of 66% and 79%, respectively. Finally, geographical or bioclimatic correlations did not explain phenotypic variation patterns observed in this highly polymorphic taxon. Perspectives on future research to investigate N. h. cetti's decline and support effective conservation measures are discussed.

The Big Five: Species Distribution Models from Citizen Science Data as Tool for Preserving the Largest Protected Saproxylic Beetles in Italy

Background. Volunteers’ participation in scientific research has increased in recent decades. Citizen science (CS) data have been used in quantitative ecology to analyse species ranges by means of species distribution models. We investigated the Italian distribution of five large saproxylic beetles (big five), to describe their niche space, paramount areas for their conservation, and conservation gaps. Methods. CS data from two projects, climate and environmental variables were used to produce Habitat suitability (HS) maps for each species and averaged HS maps. The big five’s conservation status was assessed interpolating HS maps with the distribution of protected areas, concomitantly identifying conservation gaps. Results. The pre-alpine and Apennines arcs, north-eastern Sicily and eastern Sardinia, were identified as conservation’s hotspots. Ranking HS levels from minimum to optimal, the extent of conservation gaps decreases as environmental suitability for the big five increases. Conclusions. For the first time in Italy, CS data have been used to investigate niche space of the largest protected saproxylic beetles and analyse the distribution of their suitable habitat. The resulting HS raster maps and vector layers, reporting HS value in all Italian protected areas (n° 3771), were provided and discussed, reporting an application example for conservation purposes.

Isola Rossa (Iscra Ruja) of Capo Comino (eastern Sardinia): botanical notes after a short visit in late spring

Isola Rossa (Iscra Ruja) of Capo Comino (eastern Sardinia): botanical notes after a short visit in late spring

Assessing the effects of alternative fuel treatments to reduce wildfire exposure

Effective landscape-scale fuel management strategies are essential for reducing wildfire risk in Mediterranean fire-prone areas. In this study, the minimum travel time (MTT) fire-spread algorithm as implemented in FlamMap was applied to assess the potential of alternative fuel treatments for lowering wildfire losses in a 5,740-ha study area in eastern Sardinia, Italy. Twenty-seven wildfires at 10-m resolution were simulated considering three wind speeds (15, 18, and 21 km h−1) to compare fuel treatments: no treatment (NT), irrigated agroforestry areas with shrub clearing (T1), prescribed fire in eucalyptus stands (T2), and irrigated grasslands (T3). The simulations replicated a recent large wildfire that occurred in the study area (Orrì wildfire, 2019) and considered the weather and fuel moisture conditions associated with this event. The average wildfire exposure outputs (burned area, probability of burning, conditional flame length, potential crown fire occurrence, and surfaces withflame lengths above 2.5 m) decreased after fuel treatments, compared to no treatment. T1 was the most effective strategy in mitigating wildfire hazards and provided the most significant performance for several wildfire exposure indicators. Treating only 0.5% of the study area (~ 30 ha) resulted in a decrease in all wildfire exposure metrics to ~ 10% within the study area. In addition, the total surface characterized by high flame length (average > 2.5 m) was the lowest in the T1 treatment. This study can help land and fire managers optimize fuel treatment opportunities and wildfire risk mitigation strategies in Mediterranean areas.

Reintroductions of the Corsican Red Deer (Cervus elaphus corsicanus): Conservation Projects and Sanitary Risk

Simple SummaryReintroductions are important tools to achieve the long-term conservation of endangered species; however, these projects are dangerous for translocated animals. Reintroduced animals face novel habitats where food availability and secure resting sites are unknown, and in this context, such animals likely engage in long exploratory movements. Furthermore, reintroductions can be dangerous for domestic and wild animals inhabiting the reintroduction site due to the potential risk of catching diseases carried by reintroduced animals. Our study aimed to evaluate the spatial behavior of reintroduced Corsican red deer in central-eastern Sardinia and, on the basis of the obtained results, build a species distribution model to forecast the expansion of reintroduced deer and plan future reintroduction projects. Furthermore, we evaluated the sanitary risk for domestic animals (sheep) linked to Bluetongue virus potentially carried by deer. Our results highlighted the great habitat suitability of central–eastern Sardinia for Corsican red deer. However, deer are healthy carriers of Bluetongue virus, as confirmed by health analyses we performed on captured animals in the source areas. Particular attention in reintroduction planning is needed to avoid any negative impacts on domestic or wild animals of conservation measures.The Corsican red deer is an endangered subspecies that needs artificial translocation projects to gain its complete recovery with the formation of viable, interconnected populations. Between 2007 and 2017, we performed two reintroduction projects in four sites in central–eastern Sardinia via tracking 32 deer by means of GPS/GSM radiotelemetry. On the basis of the obtained results, we built a species distribution model (SDM) using MaxEnt software, selecting 200 random points from the merged deer core areas as presence data. Furthermore, to evaluate the sanitary risk linked to artificial translocations, we analyzed deer positivity to Bluetongue virus (BTV) in the founder populations. The SDM showed a high deer capability to colonize central–eastern Sardinia, but it also showed the possibility of spreading BTV to domestic sheep because sanitary analyses confirmed the virus’ presence in the founder populations. Our main conclusion was that reintroductions are effective tools for the long-term conservation of the Corsican red deer, as long as sanitary risks are minimized by means of sanitary monitoring of translocated deer.

Evolution of Deep-Seated Gravitational Slope Deformations in Relation with Uplift and Fluvial Capture Processes in Central Eastern Sardinia (Italy)

Connections between Plio-Pleistocenic tectonic activity and geomorphological evolution were studied in the Pardu Valley and Quirra Valley (Ogliastra, East Sardinia). The intensive Quaternary tectonic activity in Sardinia linked to the opening of the Tyrrhenian Basin is known. In Eastern Sardinia, it manifests with an uplift that is recorded by geomorphological indicators, such as deep-seated gravitational slope deformation, fluvial captures, engraved valleys, waterfalls, and heterogeneous water drainage. The Pardu River flows from the NW toward the SE and then abruptly changes direction toward the NE. At this point, a capture elbow adjacent to the current head of the Quirra River is well developed. The Quirra River, in its upstream part, flows at altitudes approximately 200 m higher than the Pardu River. It also shows an oversized and over-flooded valley with respect to the catchment area upstream. This setting indicates that the Pardu River, which previously flowed south along the Quirra River, was captured by the Pelau River. We analyzed long-term landslides with lateral spreading and sackung characteristics, which involve giant carbonate blocks and underlying foliated metamorphites in both valleys. The use of LiDAR, high-resolution uncrewed aerial vehicle digital photogrammetry (UAV-DP), and geological, structural, and geomorphological surveys enabled a depth morphometric analysis and the creation of interpretative 3D models of DGSDs. Space-borne interferometric synthetic aperture radar (InSAR) data using ERS and Sentinel-1 satellites identified downslope movement of up to 20 mm per year in both Pardu Valley flanks. Multi-source and multi-scale data showed that the state of activity of the DGSDs is closely linked to the geomorphological evolution of the catchment areas of the Rio Pardu and Rio Quirra. The intense post-capture erosion acted in the Rio Pardu Valley, giving it morphometric characteristics that were favorable to the current evolution of the DGSDs, while the Rio Quirra Valley presents paleo-DGSDs that have been fossilized by pre-capture terraced alluvial deposits.

Origin of dolomites in oolitic carbonates of the Middle Jurassic Dorgali Formation, eastern Sardinia, Italy: Petrographic and geochemical constraints

The Bathonian-Callovian (Middle Jurassic) Dorgali Formation in eastern Sardinia (Italy) consists of dolomitized oolitic grainstone and records a complex diagenetic history. Petrographic examinations revealed three main phases of replacive (D1, D2) and fracture-filling (D3) dolomites with crystal-size ranges of <4–50 μm (dolomicrite to dolomicrosparite D1), 50–200 μm (eu-to subhedral dolomite D2), and 50–400 μm (sub-to anhedral crystals of dolomite D3). The early D1 exhibits dull luminescence (CL) under cathodoluminoscope, whereas the later D2 shows dull to zoned CL, and D3 consistently zoned CL. The near-micritic grainsize, low Sr contents (136 ± 43 ppm) and estimated δ18O values of the parent dolomitizing fluids (−1.3‰ to −0.9‰ VSMOW) suggest an early-diagenesis origin for D1 at low temperatures of near-surface conditions. In contrast, the larger crystal size and microthermometric measurements of primary two-phase fluid inclusions (Th = 101.7 ± 8.0 °C) reveal that D2 precipitated during later stages at higher temperatures of mid-to deeper burial settings, which is supported by the high calculated δ18O values of D2 parent dolomitizing fluids (10.0‰–10.7‰ VSMOW). Petrographic examinations suggest that the vug- and fracture-filling D3 and coarse calcite cement (C3, up to 2 mm) precipitated at deeper burial conditions, which is consistent with the low δ18O (−5.2 ± 1.0‰ VPDB) and δ13C (−5.1 ± 2.6‰ VPDB) compositions of C3. The similarity in shale-normalized REESN patterns, strong negative Ce anomalies and lack of Eu anomalies, suggest a seawater origin for the parent dolomitizing fluids.

Development of coral\u2013sponge\u2013microbialite reefs in a coated grain-dominated carbonate ramp (Upper Jurassic, eastern Sardinia, Italy)

The Late Jurassic is a peak time of diversification of reefs with corals, stromatoporoids, calcareous and siliceous sponges, and microbialites during the Phanerozoic. This study focuses on the Callovian–Kimmeridgian carbonate succession of eastern Sardinia, deposited at tropical latitudes on the European passive margin that recorded from the late Oxfordian the evolution from a coated grain-dominated to a reef-bearing carbonate ramp. The coated grain-dominated carbonate ramp (phase 1; Callovian–middle Oxfordian) includes inner ramp ooidal shoals and peloidal packstone in the middle-to-outer ramp. The overlying reef-bearing ramp (phase 2; late Oxfordian–late Kimmeridgian) is characterized by three types (1–3) of bioconstructions. The distribution of these build-ups along the middle-to-outer ramp depositional profile reflects bathymetric parameters, related to the interplay of water energy and light penetration. Type 1 build-ups developed in the proximal middle ramp and consist of 45 m thick, 100 m wide, coral-stromatoporoid boundstone associated with coral–stromatoporoid rudstone–grainstone. Type 2 build-ups, colonizing deeper environments in the middle ramp, are lens-shaped coral–calcareous sponge–diceratid boundstone including stromatoporoids and chaetetid sponges, 1–2 m thick and 3–4 m wide, associated with bioclastic packstone–grainstone. Type 3 lens-shaped calcareous and siliceous sponge–coral–microbialite boundstone build-ups (1 m thick and a few metres wide) formed in lower energy, distal middle-to-outer ramp settings. The evolution of the eastern Sardinian carbonate ramp reflects the Oxfordian–Kimmeridgian spread of the coral–sponge-microbialite reefs along the Tethyan European passive margin.

Spatial distribution and habitat characterization of marine animal forest assemblages along nine submarine canyons of Eastern Sardinia (central Mediterranean Sea)

Submarine canyons are peculiar habitats of the continental margin due to their hydrodynamic and geomorphological features. Coral assemblages forming marine animal forests (MAFs) are one of the key benthic components dwelling in these habitats, where they enhance the substrate's heterogeneity and provide shelter, feeding and spawning habitats for a wide variety of species. They are also considered Vulnerable Marine Ecosystems (VMEs), since their fragile three-dimensional framework and slow growth rate exposes them to multiple anthropogenic stressors. Understanding the coupling processes between environmental factors and the scale at which coral assemblages develop in these habitats, is an essential step towards their protection. This study aims to identify MAFs along submarine canyons in the central Mediterranean basin (Eastern Sardinia) on the basis of video transects carried out using Remotely Operated Vehicle and test the influence of environmental variables (silt coverage, distance from the coast, water depth and slope of the substrate) in driving the spatial distribution variability. We identified nine MAF assemblages dwelling in both rocky and silted substrate, from 90 to 220 m depth. We found that the most significant variability in densities and diversity of MAF assemblages occurs mostly within canyons rather than among canyons that are distant hundreds of km apart. Distance-based linear modelling (DistLM) identified silt coverage and water depth as the main factors explaining the observed variability. Overall our study provided new insights on MAFs composition and spatial distribution in submarine canyons which are, in turn, strongly influenced by local physical conditions. Such results emphasized the need for sound in situ conservation strategies in order to preserve MAFs and their ecological role.

NEW GEOLOGICAL AND STRATIGRAPHICAL DATA AND DISCOVERY OF LOWER ORDOVICIAN ACRITARCHS IN THE SAN VITO SANDSTONE OF THE GENN'ARGIOLAS UNIT (SARRABUS, SOUTHEASTERN SARDINIA)

The subject of this paper is new geological and stratigraphical data regarding the Paleozoic in the Sarrabus area (Southeastern Sardinia). More particularly Tremadocian (Lower Ordovician) acritarchs have been found in samples taken for microfossils research from the weakly metamorphosed terrigenous sediments of the San Vito Sandstone.&#x0D; Until recently only acritarchs from the Middle and Upper Cambrian has been found in the San Vito Sandstone. This new finding provides a more precise dating of the San Vito Sandstone, a more exact correlation between this Sarrabus formation and analogous formations with acritarchs in Central- Eastern Sardinia and also further confirmation of the Intraordovician age of the Sarrabese Phase and of the corresponding Sardic Phase of Iglesiente-Sulcis area (Southwestern Sardinia).

New onshore/offshore evidence of the Messinian Erosion Surface from key areas: The Ibiza-Balearic Promontory and the Orosei-Eastern Sardinian margin

As the Messinian sea-level draw down associated with the Messinian Salinity Crisis is still questioned, we propose to show that the widely spread erosion surface affecting the Mediterranean margins is indeed linked to an exondation demonstrated from offshore and onshore data. Our study presents a comprehensive onshore to offshore correlation of the Messinian erosional surface. It is focused on small drainage systems or interfluve areas, outside of evaporite basins or incised canyons, where the Messinian erosion had not yet been studied previously: around Ibiza on the Balearic Promontory and around Orosei on the Eastern Sardinian margin, Tyrrhenian Basin, both areas where new offshore data were recently acquired. We show that the late Messinian erosion formed in subaerial settings, as testified by evidence of continentalization events, and attests for a regression phase that was correlated from the offshore continental slopes to the onshore paleo-platforms in both areas. Characteristics of this erosion in both study areas strengthen the scenario with at least one important low-stand sea-level for the Messinian Salinity Crisis with evaporites subbasins lying at different depths and possibly disconnected.

Sedimentary evolution of a coral-, microbialites- and debris-rich Upper Jurassic reef (upper Tithonian, eastern Sardinia, Italy)

This work investigates a portion of a poorly documented upper Tithonian reef (Lower Mt. Bardia Reef, LBR) developed along the northern platform margin of the eastern Sardinia Platform (ESP). The LBR was probably one of the most southerly reefs of the northern Tethys margin, and this study provides the first comprehensive description of facies and internal structure, giving insights for the depositional setting.Detailed compositional and facies analyses of LBR have been carried out in three quarries located in the Orosei Gulf (eastern Sardinia). The main reef components are represented by carbonate (bioclastic) debris, microbialites and microencrusters, and reef-building organisms (mainly corals and stromatoporoids). These components combine in various proportions, forming several facies and facies associations. Ten reef facies (RF), grouped into three main Facies Associations have been identified within the studied reef portion. The distribution and arrangement of facies reveal a sedimentary evolution, evolving from a microframework-dominated reef to a carbonate debris-dominated one, with the internal reef architecture evolving from massive, to patchy, to coarsely stratified and roughly bedded.The reef components and facies indicate that the investigated portion of the LBR corresponds to a shallow back-reef zone, characterized by well-lit and generally low-energy hydrodynamic conditions, possibly developed in back position with respect to a higher-energy zone that was closer to the edge of the platform. In this depositional context, the arrival of large amounts of debris and the evolving internal architecture are interpreted as the result of the infilling process of the back-reef zone due to the progradation of a sand apron, during a long-term regional regressive phase.

Using salt tectonic structures as proxies to reveal post-rift crustal tectonics: The example of the Eastern Sardinian margin (Western Tyrrhenian Sea)

Abstract The METYSS project (Messinian Event in the Tyrrhenian from Seismic Study) is based on high-resolution seismic data acquired along the Eastern Sardinian margin, Western Tyrrhenian Sea. The main aim is to study the Messinian Salinity Crisis (MSC) in the Western Tyrrhenian Basin, but we also investigated the thinning processes of the continental crust and the timing of crustal vertical movements across this backarc domain. Our first results shown that rifting ended before the MSC, but that crustal activity persisted long after the end of the rifting. This has been particularly observed on the proximal margin, the East-Sardinia Basin, where the Mobile Unit (MU, mobile Messinian salt) is thin or absent. In this study, we examined the distal margin, the Cornaglia Terrace, where the MU accumulated during the MSC and acted as a decollement, thus potentially decoupling the basement from the sedimentary cover. Our observations provide evidence for lateral flow and gravity gliding of the salt and its brittle sedimentary overburden along local basement slopes generated by the post-MSC tilting of some basement blocks formerly generated during the rifting. We also investigated an intriguing wedge-shaped body of MU located in a narrow N-S half graben bounded to the west by a major, east-dipping, crustal normal fault. Classically, one could think that this salt wedge is related to the syn-tectonics deposition of the MU, but we propose an original scenario, in which the post-rift vertical motion of the major fault has been cushioned by lateral flow of an initially tabular salt layer, leaving the supra-salt series apparently unaffected by the crustal motions of the basement. We tested this scenario by comparing natural data and physical (analogue) modelling data. Our results reveal that salt tectonics provides a powerful tool to understand the deep crustal tectonics of the margin and to constrain the timing of vertical motions in the Western Tyrrhenian Basin, results that can be applied to rifted salt-bearing margins worldwide.

8000 years of coastal changes on a western Mediterranean island: A multiproxy approach from the Posada plain of Sardinia

A multi-proxy palaeoenvironmental investigation was conducted to reconstruct the Holocene history of coastal landscape change in the lower Posada coastal plain of eastern Sardinia. In the Mediterranean region, coastal modifications during the Holocene have been driven by a complex interplay between climate, geomorphological processes and human activity. In this paper, millennial-scale human-sea level-environment interactions are investigated near Posada, one of the largest coastal plains in eastern Sardinia. Biostratigraphic and palynological approaches were used to interpret the chrono-stratigraphy exhibited by a series of new cores taken from the coastal plain. This new study elucidates the main paleoecological changes, phases of shoreline migration and relative sea-level change during the last 8000 years. These results indicate the major role of sea-level stabilization and high sediment supply in driving major landscape changes, especially during the Neolithic period (6th–4th millennia BC), and the long-term settlement history of this coastal valley area. It is concluded that human occupation of the coastal plain, from prehistoric to historical times, was most likely constrained by the rapid and constant evolution of this coastal landscape.

The Western Tyrrhenian Sea revisited: New evidence for a rifted basin during the Messinian Salinity Crisis

In the last fifty years, the Messinian Salinity Crisis (MSC) has been widely investigated in the Mediterranean Sea, but a major basin remains fewly explored in terms of MSC thematic: the Western Tyrrhenian Basin. The rifting of this back-arc basin is considered to occur between the Middle-Miocene and the Early-Pliocene, thus including the MSC, giving a unique opportunity to study the crisis in a context of active geodynamics. However the MSC seismic markers in the Western part of the Tyrrhenian Sea have only been investigated in the early eighties and the MSC event in the Western Tyrrhenian Basin remains poorly studied and unclear.In this study, we revisit the MSC in the Western Tyrrhenian Basin, i.e. along the Eastern Sardinian margin. We present results from the interpretation of a 2400km long HR seismic-reflection dataset, acquired along the margin during the “METYSS” research cruises in 2009 and 2011. The maps of the MSC seismic markers reveal that the Eastern Sardinian margin was already dissected in structurals highs and lows during the MSC. We also demonstrate that the MSC markers constitute powerfull time-markers to refine the age of the rifting, which ended earlier than expected in the East-Sardinian Basin and the Cornaglia Terrace. These results allow us to discuss the palaeo water-depth of the Western Tyrrhenian Basin during the MSC, as well as implications for possibles scenarios of the Messinian Salinity Crisis across the Eastern Sardinian margin.

Origin of exotic clasts in the Central-Southern Apennines: clues to the Cenozoic fold-and-thrust collisional belt in the Central Mediterranean area

AbstractThe Central-Southern Apennines are the result of the collision between Europe and Africa. Despite the volume of existing literature, many problems remain unsolved such as the presence of Tertiary conglomerates containing exotic basement clasts. The lack of basement rocks in the Central-Southern Apennines implies that the origin of these clasts has to be sought in areas where the basement is extensively exposed. These include the Calabro–Peloritani arc and the Sardinia–Corsica block, which in Cenozoic time were connected to the Central-Southern Apennines. In this work we present the results of sedimentary, geochemical and petrographic analyses performed on the exotic basement-derived clasts. These analyses include lithological, major- and minor-element and rare Earth element compositions which are compared to analogous rocks from Calabria and Sardinia basements. Results indicate Eastern Sardinia as the primary source area for the studied conglomeratic units, linking the Central-Southern Apennines sedimentary cover to the Mesozoic carbonates of Eastern Sardinia prior to the opening of Tyrrhenian Sea. The Cilento unit (Campania) was directly fed by an uplifting Cenozoic orogen, and the Filettino, Gavignano (Latium) and Ariano Irpino (Campania) units were produced by the successive reworking of ‘Cilento-like’ sedimentary units. These results may imply that part of the Central-Southern Apennines represented a portion of the European margin of the Tethys.

Reply to Comments on “the Cenozoic Fold‐and‐Thrust Belt of Eastern Sardinia: Evidences from the Integration of Field Data With Numerically Balanced Geological Cross Section” by Arragoni et al. (2016)

AbstractThe comment by Berra et al. (2017) on the evidence of Alpine tectonics in Eastern Sardinia proposed by Arragoni et al. (2016) is based on the sedimentological interpretations of few local outcrops in a marginal portion of the study area. The Cenozoic Alpine fold‐and‐thrust setting, which characterizes this region, presents flat‐over‐flat shear planes acting along originally stratigraphic contacts, where stratigraphic continuity is obviously maintained. The ramp sectors present steeply dipping bedding attitudes, and there is no need to invoke and to force prograding clinoforms with unrealistic angles to justify them. The balanced geological cross section proposed by Arragoni et al. (2016) is fully supported by robust newly collected structural data and is compatible with the overall tectonic setting, while the interpretation proposed by Berra et al. (2017) lacks a detailed structural investigation. We believe that the partial application of the techniques available to modern geology may lead to incorrect interpretations, thus representing an obstacle for the progress of knowledge in the Earth sciences.