The Scleractinian genus Actinacis. Systematic revision and stratigraphic record of the Tertiary species with special regard to Italian occurrences.

Twenty-seven Tertiary species belonging to the cosmopolitan reef-building scleractinian genus Actinacis, have been described in the literature. A detailed systematic revision has been carried out for Italian and European species by thin section measurements. A combination of several measured corallite morphologic characters and diagnostic features is proposed as a realiable tool for species recognition. Preliminary examination of the stratigraphic and geographic distribution of Actinacis species suggests that: 1) the Tertiary distribution of the genus ranges from the Late Paleocene to the Late Oligocene; 2) the highest species diversity occrred during the Middle Eocene, when the genus consisted of a relatively large number of geographically restricted species; 3) only two widespread species survived the Eocene/Oligocene turnover and reached the Late Oligocene, when the genus became globally extinct

Acropora (Scleractinia) from the Oligocene and Miocene of Europe: species longevity, origination and turnover following the Eocene–Oligocene transition

Four new species and new records for six species of the highly successful reef-building coral genus Acropora are described from Oligocene and Early Miocene (Rupelian to Burdigalian) localities in Europe. Acropora slovenica sp. nov. is described from Slovenia (Gornji Grad beds); A. piedmontensis sp. nov. and A. macrocalyx sp. nov. from the Torino Hills (Piedmont), and A. salentina sp. nov. from the Salento Peninsula (Apulia) of Italy. The remaining six species have an Eocene lineage. From south-west France, A. anglica and A. bartonensis, previously known from England (Priabonian and Bartonian), are recorded: A. anglica in Oligocene (Chattian) and both in Miocene (Aquitanian) deposits, indicating their persistence in the western Tethys for up to 17 and 20 million years respectively. Also recorded from Aquitaine is A. wilsonae (type locality Eocene Paris Basin), indicating persistence in western France for up to 28 million years. Italian material includes A. proteacea, also known from the Lower Bartonian of France and A. lavandulina, already known from Italy and the Eocene of France. From Slovenia (Oligocene, Rupelian), A. haidingeri is recorded, including from the type locality. The species are interpreted as representing seven extant species groups previously documented from the Eocene of Europe and the first records for two further extant groups. These results complement a previous finding of Eocene diversification of Acropora into the beginnings of up to 10 of the 20 recognized modern species groups in England and France. They indicate that the longevity of some Eocene taxa was extended into the Oligocene to Early Miocene of Europe and allowed some turnover, probably associated with changes in configuration of the western Tethys Sea. This information is important for interpreting molecular phylogenies and the evolution of modern Acropora diversity, by providing extended stratigraphical ranges for species groups with Eocene origins and dates of origination for two groups previously unrecorded in the early fossil record

THE SCLERACTINIAN GENUS ACTINACIS . SYSTEMATIC REVISION AND STRATIGRAPHIC RECORD OF THE TERTIARY SPECIES WITH SPECIAL REGARD TO ITALIAN OCCURRENCES

Twenty-seven Tertiary species belonging to the cosmopolitan reef-building scleractinian genus Actinacis, have been described in the literature. A detailed systematic revision has been  carried out for Italian and European species by thin section  measurements of material mostly sampled from several Italian localities by observation of some holotypes and topotypes and accurare examination of the available literature. A combination of several measured corallite morphologic characters and diagnostic features is proposed as a reliable tool for species recognition. Results indicate that only three species, of the twelve described for the Italian Tertiary sites, actually belong to the genus Actinacis. Moreover, a list of synonyms and a stratigraphic range chart of the established species are proposed. An approximate taxonomic identification and stratigraphic distribution are given for those species not included in the systematic revision. Preliminary examination of the stratigraphic and geographic distribution of Actinacis species suggests that:1) the Tertiary distribution of the genus ranges from the Late Paleocene to the Late Oligocene (from Late Cuisian to Middle Chattian as concerns ltaly); 2)the highest species diversity occurred during the Middle Eocene, when the genus consisted of a relatively large number of geographically restricted species; 3) only two widespread species survived the Eocene/Oligocene turnover and reached the Late Oligocene, when the genus became globally extinct

Stratigraphic architecture of the Salento Coast from Capo d’Otranto to S.Maria di Leuca (Apulia, Southern Italy)

The Cretaceous to Quaternary succession of the Apulia Platform cropping out on the eastern coast of the Salento Peninsula shows a special stratigraphic architecture. Whereas on the platform top, i.e. on the Salento Peninsula proper, the succession is at most a few tens of metres thick and is punctuated by unconformities, on the margin and slope of the platform, along the present-day eastern coast of the peninsula, several carbonate systems are laterally disposed and grafted one upon the other. Three of these systems are clinostratified and include well developed reef tracts of Priabonian, early Chattian and early Messinian age.The geologic conclusion of our study is that, since the Late Cretaceous, the eastern coast of the Salento Peninsula grossly coincided with the margin of the Apulia Platform. This paleogeographic element acted as a foreland horst and registered important geodynamic events related to the growth of the adjacent Hellenide and Apennine thrust belts. During the last 60 m.y., the horst carapace was constantly near sea level and sediments were mainly accommodated and preserved on the deep margin and slope of the platform

Microtaphofacies analysis of lower Oligocene turbid-water coral assemblages

The presence, distribution, and preservation of coral-rich facies in the lower Oligocene Gornji Grad Beds of Slovenia are analyzed using a microtaphofacies approach. This method allows taphonomic signatures to be recognized in thin section along with the presence of coral specimens and growth forms within and between stratigraphic logs. Coral-dominated limestones within the Gornji Grad Beds are represented by rudstones in a packstone-wackestone matrix. The conditions are generally reconstructedas turbid water due to the prevalence of muddy carbonate matrix, which also leads to excellently preserved morphological features in thin section. These beds represent a reference area for the study of Paleogene corals, especially during the Oligocene, a key phase of reef development during the Cenozoic. This study also contributes to the characterization of fossil reefs in turbid-water environments. The evaluated coral fauna is dominated by delicate-branching Stylophora and Acropora, although thickly branching (Actinacis, Goniopora), phaceloid (Caulastrea), and massive forms (Alveopora, Astreopora, Antiguastrea) also occur. Assessed taphonomic signatures include fragmentation, abrasion, bioerosion, and encrustation. Three types of bioerosion traces are distinguished (Entobia, Gastrochoenolites, Trypanites). Encrustation includes both thincrusts and complex multi-taxon sequences dominated by coralline algae. Five microtaphofacies are distinguished based on variation of taphonomic signatures, taxonomic composition, and growth forms. Differences in microtaphofacies are interpreted with respect to turbidity, sediment accumulation, and water turbulence; both parautochthonous and allochthonous deposits are reconstructed. A depositional model based on the distribution of microtaphofacies in the studied sections shows a succession of coral communities with different colonization strategies reflecting generally high stress levels

STRATIGRAPHIC ARCHITECTURE OF THE SALENTO COAST FROM CAPO D'OTRANTO TO S.MARIA DI LEUCA (APULIA, SOUTHERN ITALY)

The Cretaceous to Quaternary succession of the Apulia Platform cropping out on the eastern coast of the Salento Peninsula shows a special stratigraphic architecture. Whereas on the platform top, i.e. on the Salento Peninsula proper, the succession is at most a few tens of metres thick and is punctuated by unconformities, on the margin and slope of the platform, along the present-day eastern coast of the peninsula, several carbonate systems are laterally disposed and grafted one upon the other. Three of these systems are clinostratified and include well developed reef tracts of Priabonian, early Chattian and early Messinian age. The geologic conclusion of our study is that, since the Late Cretaceous, the eastern coast of the Salento Peninsula grossly coincided with the margin of the Apulia Platform. This paleogeographic element acted as a foreland horst and registered important geodynamic events related to the growth of the adjacent Hellenide and Apennine thrust belts. During the last 60 m.y., the horst carapace was constantly near sea level and sediments were mainly accommodated and preserved on the deep margin and slope of the platform.&nbsp

Coral assemblages and bioconstructions adapted to the depositional dynamics of a mixed carbonate-siliciclastic setting: the case study of the Burdigalian Bonifacio Basin (South Corsica)

Coral bioconstructions associated with mixed carbonate-siliciclastic settings are known to be strongly controlled by coastal morphology and paleotopography. A striking example is represented by the different types of coral bioconstructions and coral-rich deposits of the Cala di Labra Formation deposited in the coastal environment of the Bonifacio Basin (Corsica, France) during the Early Miocene. Detailed mapping on photomosaics allowed accurate documentation of the internal organization of coral deposits as well as lateral and vertical facies relationships. Four types of coral bioconstructions (CB) and one reworked coral deposits (RCD) have been recognized. The CB are represented by sigmoidal cluster reefs, coral carpets and skeletal conglomerates rich in corals. The RCD occurs in lens-shaped bodies intercalated within clinoforms composed of bioclastic loatstones and coarse packstones. The investigated bioconstructions can be contextualised in a coastal environment. In the upper shoreface corals developed in association with the oyster Hyotissa, above bioclastic conglomerates sourced by ephemeral streams and erosion of the granitic coastline. In the lower shoreface corals formed sigmoidal bioconstructions interpreted as cluster reefs, whereas coral carpets developed during a relative sea-level rise related to the middle Burdigalian transgressive phase. The reworked coral deposits can be interpreted as lobe-shaped deposits of coarse-grained bioclastic submarine fans formed at the base of the depositional slope of an infralittoral prograding wedge system

Impact of ocean acidification on crystallographic vital effect of the coral skeleton

Distinguishing between environmental and species-specific physiological signals, recorded in coral skeletons, is one of the fundamental challenges in their reliable use as (paleo)climate proxies. To date, characteristic biological bias in skeleton-recorded environmental signatures (vital effect) was shown in shifts in geochemical signatures. Herein, for the first time, we have assessed crystallographic parameters of bio-aragonite to study the response of the reefbuilding coral Stylophora pistillata to experimental seawater acidification (pH 8.2, 7.6 and 7.3). Skeletons formed under high pCO2 conditions show systematic crystallographic changes such as better constrained crystal orientation and anisotropic distortions of bio-aragonite lattice parameters due to increased amount of intracrystalline organic matrix and water content. These variations in crystallographic features that seem to reflect physiological adjustments of biomineralizing organisms to environmental change, are herein called crystallographic vital effect (CVE). CVE may register those changes in the biomineralization process that may not yet be perceived at the macromorphological skeletal level. https://doi.org/10.1038/s41467-019-10833-6 OPEN