New paleoenvironmental insights on the Miocene condensed phosphatic layer of Salento (southern Italy) unlocked by the coral-mollusc fossil archive

From the Late Oligocene to the Late Miocene, the central Mediterranean area was characterized by the extensive deposition of phosphate-rich sediments. They are usually represented by 10 to 20-cm-thick hardgrounds made of phosphatic and glauconitic sediments containing a rich macrofossil association. This study represents the first thorough investigation of the biotic assemblage of Mediterranean phosphorites aimed at collecting new information on the environmental factors controlling their deposition. The Serravallian/Tortonian phosphatic deposits of the Salento Peninsula (“Aturia level”) have been selected for the abundance of fossil remains and special attention is given to the coral–mollusc association. Two different facies have been recognized: a basal coral rudstone that includes most of the macrofossils, superimposed by a detrital rudstone made of thin layers mainly composed of phosphatic fragments. These two facies are separated by a phosphatic crust several millimeters in thickness. The coral assemblage contains at least 17 azooxanthellate taxa belonging to four families, while the molluscs are represented by a rich gastropod fauna (26 species), associated with bivalves (18 species) and cephalopods (two species). Four distinct depositional phases have been recognized, with the coral rudstone representing the key-facies to reconstruct the onset of the “Aturia level” and the original environment of its fossil content. The composition of the coral–mollusc association has been reliably compared with present-day analog taxa, suggesting the occurrence of a heterogeneous seafloor formed by rocky substrates and accumulations of soft sediment, at around 100–350-m water depth, and under the influence of moderate-to-strong bottom currents rich in nutrients and resuspended organic matter

QUATERNARY BUILD-UPS AND RHODALGAL CARBONATES ALONG THE ADRIATIC AND IONIAN COASTS OF THE ITALIAN PENINSULA: A REVIEW

In the Mediterranean, build-ups (created by coralline algae, Cladocora caespitosa, deep-water corals, vermetids, polychaetes and bacteria) and rhodolith beds are important hot-spots of biodiversity. Being severely threatened by anthropogenic impact and climate change, they have been included in international directives on environmental protection. This work wants to support the ongoing research on modern bioconstructions by providing further data on the long-term effects of environmental factors on these habitats. Our results are based on the analysis of the existing literature on the outcropping Quaternary successions of the Adriatic and Ionian coasts of peninsular Italy. The existing reports of build-ups and rhodalgal carbonates have been summarized in an homogeneous data-set and then studied to highlight distribution patterns in space and time. The analyses consistently outlined the importance of sedimentation rate in controlling the general distribution of build-ups and rhodalgal carbonates. The majority of the reports is concentrated south of the Gargano, where the sediment-load of the rivers is small. The majority of the reports is related to coralline algae, suggesting that they were the main carbonate producers during the period. C. caespitosa general distribution is mainly controlled by temperature, with most of the occurrences dating back to the warm periods of the late Ionian and of the Tarantian. Large build-ups of Cladocora are restricted to embayments and gulfs well-protected against storm waves. The distribution of the outcrops of deep-water corals is biased by the geological setting. A remarkable uplift is necessary to bring these corals from their original deep-water setting to elevated areas onshore. Consequently, most of the outcrops are in Southern Calabria which is characterized by a strong Quaternary uplift. Chemosynthetic build-ups, intertidal bioconstructions (made by vermetids, polychaetes or coralline algae), as well as stromatolites, are rare in the study area

New insights on coral mound development from groundtruthed high-resolution ROV-mounted multibeam imaging

Currents play a vital role in sustaining and developing deep water benthic habitats by mobilising food and nutrients to otherwise relatively barren parts of the seabed. Where sediment supply is significant, it can have a major influence on the development and morphology of these habitats. This study examines a segment of the Belgica Mound Province, NE Atlantic to better constrain the processes affecting a small-sized cold water coral (CWC) mound habitat and conversely, the hydrodynamic influence of CWC mounds on their own morphological development and surroundings. Here, we utilise ROV-mounted multibeam, ROV-video data, and sediment samples to investigate current processes, mound morphology, density and development. Detailed mapping shows that the area may have the highest density of coral mounds recorded so far, with three distinct mound types defined based on size, morphology and the presence and degree of distinct scour features. A residual current of 36–40 cm s−1 is estimated while large scour features suggest low-frequency, high-magnitude events. These 3 mound types are i) smaller mounds with no scour; ii) mounds with scour in one to two distinct directions and; iii) larger mounds with mound encircling scour. The differing mound types likely had a staggered initiation where younger mounds preferentially developed near clusters of pre-existing mounds. Given the high density of these small CWC mounds, we support the hypothesis that over time, this clustering may eventually lead to these mounds coalescing into larger coral mound features

Hanging coral gardens of a Tyrrhenian submarine cave from Sicily (Italy)

An exceptionally well-preserved cave palaeocommunity is described from the Capo Milazzo Peninsula (NE Sicily). The Fulco Cave formed within a layer of breccia including metamorphic and Miocene limestone blocks together with rare clasts of isidid-bearing lithified bathyal sediments. This new breccia type points to a still undescribed deposition event in the early Pleistocene. The fossil association inside the cave is relatively diversified and dominated by the dendrophyllid coral Astroides calycularis whose colonies encrusted the cavity ceiling and grew in an upside-down position, forming spectacular "hanging gardens". The warm climate affinity of Astroides indicates that colonisation took place during an interglacial period, possibly during the Tyrrhenian. The palaeocommunity indicates a semi-dark cave open toward the sea in a shallow water setting. The elongation of Astroides corallites was possibly driven by a low level of water motion and/or competition for space and food. The common constrictions point to slow or no growth phases possibly related to environmental fluctuations, periodically leading to mass mortality events

Facies character and skeletal composition of heterozoan carbonates in a high-energy confined embayment (Miocene, Finale Ligure Limestone, NW Italy)

During the early and middle Miocene, diverse photozoan to heterozoan carbonate and mixed carbonatesiliciclastic depositional systems characterized the Mediterranean region at palaeo-latitudes of 30-40 degrees N, during a time of warm climate. These systems ranged from carbonate ramp to rimmed platforms to current-swept flooded incised palaeo-valleys, seaways and straits. This study focuses on the facies character, skeletal biota composition, diagenesis and stable carbon and oxygen isotope signature of a mixed carbonate-siliciclastic succession (lower-middle Miocene Finale Ligure Limestone and underlying Oligocene-lower Miocene siliciclastic deposits) accumulated in a high-energy coastal setting (Finale Ligure, NW Italy) to improve the knowledge on the variety and controlling factors of Miocene heterozoan skeletal carbonates. The 3D reconstruction of the geometry of the early-middleMiocene Finale Ligure basin identifies an embayment, about 35 km2wide, limited by uplifted and eroded Alpine tectonic units and connected to the open sea through a strait. The Oligocene-Miocene sedimentary succession unconformably overlying the Alpine deformed substrate consists of 14 lithofacies (L1-L14). Besides pockets of karstic breccias (L1) preceding the marine transgression, discontinuous outcrops of glaucony-bearing litharenite, siltstone, conglomerate and wackestone/packstone with planktonic foraminifera (L2-L4) represent the preserved remnants of an eroded marine shelf affected by tectonic uplift and subsequent erosion, approximately in the Aquitanian-Burdigalian, overlain through an angular unconformity by transgressive conglomerates and bioturbated litharenites (L5-L7). The onset of carbonate skeletal production characterizes the overlying compositionally mixed carbonate-siliciclastic LanghianSerravallian Finale Ligure Limestone succession (up to 100-150 m thick, L8-L14). These cross-bedded skeletal packstone and grainstone/rudstone are composed of barnacles, echinoderms, bryozoans, bivalves, scleractinian and stylasterid corals, and lack halimedacean algae as previously published. They accumulated in a highenergy setting with strong bottom currents, driven by the amplification of tidal and/or storm currents in a confined embayment, promoting the formation of seaward prograding metre-scale subaqueous dunes. Unlike other lower-middleMiocene carbonate systems, the Finale Ligure heterozoan carbonates contain rare coralline red algae and larger benthic foraminifera but are enriched in barnacles, scleractinian and stylasterid corals. The coastal palaeo-environmental conditions, with hard rocky substrates, strong bottom currents, high nutrients and water turbidity, influenced the composition of the skeletal carbonate producers. These distinctive lithofacies character and composition resulted from the confined embayment morphology inherited from the marine flooded Alpine bedrock that was subjected to land runoff driving nutrient input. (c) 2022 Elsevier B.V. All rights reserved

Morphological polymorphism of Desmophyllum dianthus (Anthozoa: Hexacorallia) over a wide ecological and biogeographic range: Stability in deep habitats?

[EN] This adaptation text reproduces chapter II of the dissertation “Results”: Systematics and phylogeography of the deep-sea coral Desmophyllum dianthus (Anthozoa, Hexacorallia): Morphological and molecular evidences, de Anna Maria Addamo (2014), http://hdl.handle.net/10261/134194[ES] Este artículo es una adaptación del capítulo II de “Resultados” de la tesis doctoral: Sistemática y filogeografía del coral de profundidad Desmophyllum dianthus (Anthozoa, Hexacorallia): Indicios morfológicos y moleculares, de Anna Maria Addamo (2014), http://hdl.handle.net/10261/134194Although zooxanthellate corals are well known for their ecophenotypic variations, there is increasing evidence that azooxanthellate species also harbour a high degree of plasticity. Desmophyllum dianthus, a widespread solitary coral, exhibits a high degree of morphological variation in corallum forms that has never been analysed quantitatively. To assess if the clear morphological variation of D. dianthus follows a specific pattern based on environmental (or others) variables, this study combines three different morphometric approaches: (1) classical linear external morphology, (2) use of three-dimensional coordinates landmarks, and (3) linear measurements and counts made of cnidocyst features. Comparative morphological characterization of D. dianthus specimens shows a pattern of intraspecific variation over a wide ecological and biogeographic range. However, additional future studies on this and other proposed cosmopolitan species, including a similar sampling effort in localities and specimens, will be useful to explore the existence of common global patterns of morphological variability. Hypotheses for intraspecific polymorphism are discussed to explain the incongruence between the obtained results and the seemingly high morphological variability observed within D. dianthus.This research was supported by Spanish grants (CGL2011-23306 and CTM2014-57949-R) and EU CoCoNET- “Towards COast to COast NETworks of marine protected areas (from the shore to the high and deep sea), coupled with sea-based wind energy potential”- from the VII FP of the European Commission. The Spanish projects REN2001-4920-E/ANT and CTM2005-07756-C02-02/MAR supported the participation in Sub-Antarctic and Mediterranean expeditions.Peer reviewe

Cribrilinids (Bryozoa, Cheilostomata) associated with deep-water coral habitats at the Great Bahama Bank slope (NW Atlantic), with description of new taxa

Four cribrilinid bryozoans associated with deep-water corals (578-682 m depth) from the Great Bahama Bank slope, are described, two of them are new. The generic allocation of some species prompted us to raise the subgenera Puellina, Cribrilaria, and Glabrilaria to genus rank. The new combination Cribrilaria saginata (Winston, 2005) n. comb, is proposed. Genus Glabrilaria is reported from the NW Atlantic for the first time based on the description of Glabrilaria hirsuta Rosso n. sp. and Glabrilaria polita Rosso n. sp. The new genus Teresaspis Rosso n. gen. is erected, and Teresaspis lineata (Canu & Bassler, 1928) n. comb, is proposed as its type species. The new genus Harmelinius Rosso n. gen. is erected for Cribrilina uniserialis (Harmelin, 1978). Both genera have uniserial colonies formed by slightly caudate zooids with extensive gymnocyst and a frontal shield of flattened costae. Teresaspis lineata n. comb., however, has costae with pelmatidia that are connected by few intercostal bridges and separated by intercostal spaces, four orificial costa-like processes with the proximal pair arching above the orifice, hyperstomial acleithral ovicells with a pseudoporous ooecium formed by the distal zooid or a kenozooid, two types of kenozooids (large with costate frontal shield and small with smooth shield and central opesia), and an ancestrula with costate frontal shield. Avicularia are apparently absent in this species. In contrast, the type species of Harmelinius Rosso n. gen. has costae lacking pelmatidia and which are separated by slit-like intercostal spaces. The hyperstomial cleithral ovicells have smooth ooecia with a median suture and without pseudopores, and are formed by a distal kenozooid associated with a small avicularium. Additional paired oral avicularia are occasionally present, as are large kenozooids with a central opesia. Oral spines or spine-like processes are absent. Taxonomy of the above reported cribrilinid genera is discussed in detail together with the geographic distribution of all mentioned taxa

Characterisation of Middle-Late Pleistocene groove-and-ridge landforms incised across the Dover Strait

Recent investigations have revealed several sets of linear ridges and grooves located in the seafloor of the submarine Dover Strait. The formation of these features is associated with the occurrence of megaflood flows during Middle-Late Pleistocene glacial stages. These megaflood events are also linked to the formation of a prominent inner channel within the Lobourg Channel and the incision of streamlined islands and longitudinal scours into its bed. However, the erosional origin of the linear ridges and grooves and their possible relationship to megaflood erosion have never been demonstrated. In the present study, high-resolution geophysical data were combined with geological data and direct observations to better understand the mechanisms that caused the formation of linear ridges and grooves in the Dover Strait. The combined interpretation of these datasets corroborates that those features are carved into a hard substratum. However, the linear ridges and grooves are truncated by scours, the formation of which is associated with the last episodes of megaflood erosion that imprinted the seafloor of the Dover Strait. Therefore, the linear ridges and grooves were carved by erosional/weathering processes that took place before the incision of those scours. Based on their morphology and regional palaeogeographic reconstructions, it is proposed that the incision of the linear ridges and grooves was caused by fluvial and high-magnitude (not necessarily mega) flood erosion. The linearity of these features and their location in carbonate rocks might also indicate some control of the erosion by permafrost processes, chemical weathering and/or the rock's fabric

Merging scleractinian genera: the overwhelming genetic similarity between solitary Desmophyllum and colonial Lophelia

Background In recent years, several types of molecular markers and new microscale skeletal characters have shown potential as powerful tools for phylogenetic reconstructions and higher-level taxonomy of scleractinian corals. Nonetheless, discrimination of closely related taxa is still highly controversial in scleractinian coral research. Here we used newly sequenced complete mitochondrial genomes and 30 microsatellites to define the genetic divergence between two closely related azooxanthellate taxa of the family Caryophylliidae: solitary Desmophyllum dianthus and colonial Lophelia pertusa. Results In the mitochondrial control region, an astonishing 99.8 % of nucleotides between L. pertusa and D. dianthus were identical. Variability of the mitochondrial genomes of the two species is represented by only 12 non-synonymous out of 19 total nucleotide substitutions. Microsatellite sequence (37 loci) analysis of L. pertusa and D. dianthus showed genetic similarity is about 97 %. Our results also indicated that L. pertusa and D. dianthus show high skeletal plasticity in corallum shape and similarity in skeletal ontogeny, micromorphological (septal and wall granulations) and microstructural characters (arrangement of rapid accretion deposits, thickening deposits). Conclusions Molecularly and morphologically, the solitary Desmophyllum and the dendroid Lophelia appear to be significantly more similar to each other than other unambiguous coral genera analysed to date. This consequently leads to ascribe both taxa under the generic name Desmophyllum (priority by date of publication). Findings of this study demonstrate that coloniality may not be a robust taxonomic character in scleractinian corals