Early ordovician reefs from Argentina: Stromatoporoid vs stromatolite origin

Summary Late Arenigian biohermal reef mounds and biostromes within the shallow-marine platform facies of the upper San Juan Formation of the Precordillera (Western Argentina) represent a new Early Ordovician reef type. The meter-sized reefs are dominated byZondarella communis n.g. n. sp. The new taxon is characterized by domical, bulbous and laminar morphotypes exhibiting growth layers and thin horizontal and vertical as well as intermingled skeletal elements included within different sets. The fossil maybe compared with stromatolites and stromatoporoids but an interpretation as primitive stromatoporoids is favoured.     

Ordovician reefs of the Ural Mountains,Russia: A review

Summary The Upper Ordovician reefs of the Urals were formed at a subsiding shelf-margin during an early Late Ashgillian (Sur’ya time interval) regressive phase. Reefs of this age were studied in detail from the western slope of the Northern, the Subpolar and the Polar Urals with respect to lithofacies, biotic composition and paleogeographical patterns. The thickness of the reefs varies between 100 and 500 m. The backreef areas are characterized by lagoons with increased salinity and sabkha development. Microbial associations and a diverse algal flora (Cyanophyta, green and red algae and alga incertae sedis) are the main constituents of reefal boundstones. Tabulate and rugose corals, heliolitids, calcareous sponge-like fossils, bryozoans and problematic hydroids were also part of the reef communities. Each reef exhibits a characteristic framework-building association. Reef development was terminated by a rapid and abrupt sea-level rise at the end of the middle Upper Ashgillian connected with the global Late Ordovician glaciation.     

The Messinian reef complex of the Salento Peninsula (southern Italy): Stratigraphy, facies and paleoenvironmental interpretation

Summary An integrated study of the early Messinian reef complex cropping out along the eastern coast of the Salento Peninsula (southern Italy), including stratigraphy, facies analysis and paleoecological aspects, is here presented. Fourteen facies types belonging to three main facies associations (back reef and shelf, shelf-edge, slope) have been recognized. They document a wide spectrum of depositional environments, reef building organisms and growth fabrics, in response to depth and other environmental factors in different parts of the reef complex. The biotic structure of the reef is also described and discussed in detail. It consists of different types of reef building organisms and of their bioconstructions (mainlyPorites coral reefs,Halimeda bioherms and vermetidmicrobial “trottoirs”), that differ in composition and structure according to their position on the shelf edge-toslope profile. Results indicate that the reef complex of the Salento Peninsula has strong similarities with the typical early Messinian reefs of the Mediterranean region. However, the recognition of some peculiar features, i.e. the remarkable occurrence ofHalimeda bioherms and of vermetid-microbial “trottoirs”, gives new insights for better understanding reef patterns and development of the reef belt during the Late Miocene in the Mediterranean.     

Bioerosion in Late Permian Rugosa from reefal blocks (Hawasina Complex,Oman Mountains): implications for reef degradation

Summary Rugose corals are known from allochthonous Late Permian reefal blocks of the A1 Jil and Ba’id Formation (Hawasina Complex), Oman Mountains. In contrast to many Late Permian Rugosa found elsewhere in the Tethys, they occurred in sponge reefs and contributed to reef construction. The waagenophyllid warm water coral fauna is moderately diverse comprising cerioid, thamnasterioid, and fasciculate taxa. In contrast to sponges, chaetetids, and low-growing reefbuilders, the corals secreted diagenetically stable, most probably Mg-calcitic skeletons. Borings in coral skeletons are consequently well preserved providing important data for the interpretation of reef destructive processes. Thin-section analysis revealed three taxa of infaunal borers includingEntobia Bronn 1837, uncertain thallophyte borings, and borings of unknown bioeroders. Macroborers were more important than microborers, because of the dominance of clionid sponges. Good evidence exists also for the occurrence of two types of undetermined grazers which destroyed the coral surfaces. The amount and distribution of bioerosions is variable among different coral taxa. The fasciculate coralPraewentzelella regulare Flügel 1995 was the favorate substrate. Up to 33% of the calices were bored. Dendroid and compound corals were bored subordinately. Bioerosion of these colonies does not exceed 2%. There is good evidence for substrate preference amongst the borers. Major controlling factors affecting borer distribution are believed to be variations of skeletal density and gross morphology. The borer assemblage could not limit reef accretion significantly. Factors controlling boring activity might have been quality of substrate, sedimentation rate, rapid incrustation of substrates, and competition for food with reef constructors including sponges, chaetetids, and rugose corals.     

Barbafera carnica Senowbari-Daryan, 1980: A Triassic worm-tube

Summary Barbafera carnica Senowbari-Daryan (1980), a Carnian reef fossil of uncertain systematic position, is redescribed based on extraordinarily preserved material from Carnian reef boulders of the Cassian Formation of the Southern Alps (Dolomites/Italy).Barbafera is interpreted as a worm tube characterized by a complicated wall structure.Barbafera may belong to the family SerpulidaeRafinesque.     

Upper jurassic to lower cretaceous carbonate facies of african affinities in a Peri-European area: Chalkidiki Peninsula, Greece

Summary The Epanomi-New Iraklia area (West coast of the Chalkidiki peninsula) is considered to belong to the Prepeonias subzone (or Gevgeli unit), with a palaeogeographic position near the European margin, represented by the Serbo-Macedonian massif, and at a considerable distance from the fragmented African plate, the marginal block of which is here the Pelagonian Domain. In some boreholes in the area an Upper Jurassic to Lowei Cretaceous limestone sequence has been observed, ending with an unconformity and followed by an Upper Middle-Lower Upper Eocene transgressive bioclastic limestone, an Upper Eocene to Lower Oligocene clastic series and Neogene deposits. This Upper Jurassic to Lower Cretaceous carbonate platform sequence and probably the Upper Jurassic limestones with bauxites of the nearby Mt. Katsika, show African affinities, viz: the presence of the essentially Aptian algal speciesSalpingoporella dinarica, an African plate marker; the chlorozoan type association and the bauxite formation during the Late Jurassic indicating tropical conditions; finally, the chloralgal type association and the sporadic presence of radial-fibrous ooids during the Early Cretaceous indicating peritropical conditions. Lower Cretaceous limestones are apparently missing in the innermost Hellenides. In the Pelagonian Domain s.l., on the other hand, Upper Jurassic to Lower Cretaceous limestones are found in some places, with same characteristics as in the Epanomi-New Iraklia boreholes. On the contrary, the Upper Eocene to Lower Oligocene clastic series of the boreholes can be correlated with the Axios (=Vardar) molassic basin, inline with its present situation. During the Mesozoic, the Epanomi area therefore belonged to a micro-block, next to the NE margin of the Pelagonian Domain, in contrast to earlier interpretations. Its present time position results from Early Cenozoic tectonic phases.     

Paleocene reefs on the Maiella Platform Margin, Italy: An example of the effects of the cretaceous/tertiary boundary events on reefs and carbonate platforms

Summary Reef facies, reef types and their biotic associations in the Maiella platform margin (central Italy) provide qualitative evidence for a significant reef decline across the Cretaceous/Tertiary (K/T) boundary, and indicate two phases of reef recovery during the Paleocene. Rudists dominated the reef community until the latest Cretaceous. A significant sea-level fall around the time of the K/T boundary is documented by a truncation surface associated with emersion. During sea-level highstands in the Danian to Early Thanetian and, more extensively, during the Late Thanetian, coral-algal patch-reefs grew along the platform margin and top. Already in the Danian to Early Thanetian, the reef communities were more diverse and the constructional types more evolved than previously known from this time. Differences between the Danian to Early Thanetian coral association, the Late Thanetian association, and Late Cretaceous coral faunas may have ecological or evolutionary causes. Repeated emergence produced a complex diagenetic history in the Danian to Lower Thanetian limestones. All Paleocene reefs were displaced by gravitative redeposition. Coral-algal reefs are less important in the Early to mid Eocene, when alveolinid foraminifera dominated on the Maiella shelf. Reefs on the Maiella platform diversified and attained large sizes in the Late Eocene to Early Oligocene, as known from other Mediterranean platforms. The external controls on the Late Cretaceous to Oligocene evolution and demise of reef communities that are most easily demonstrated with our data are sealevel fluctuations and climate change. We propose that the change in reef biota and reef types across the K/T boundary and during the Early Tertiary were important causes of the parallel changes in platform growth style.     

Facies and paleoecology of the late ordovician (Caradoc-Ashgill) stromatoporoid bioherms of Tasmania, Australia

Summary Stromatoporoids, together with other sedentary organisms, form bioherms in the Ordovician Gordon Group which were deposited on a carbonate platform of the Western Tasmanian Terrane. The shallow marine carbonates of the older formations show monotonous lithofacies and biota. The variety of the lithofacies and the diversity of sedentary organisms increases in the younger formations which exhibit evidence of subaerial exposure (fissure fillings and mud-cracks). These phenomena partly reflect the tectonic history of the Western Tasmania Terrane, and probably indicate a general increase in amplitude of sea-level change during the late Ordovician (Caradoc-Ashgill). The bioherms are most frequent in the uppermost horizons (the Den Formation—late Caradoc to early Ashgill?), where the outerops exhibit floatstone and bindstone fabrics. Stromatoporoids and corals construct generally small-scale (less than several meters in width and less than 1 m in height) binding structure. Based on growth forms, stromatoporoid genera are assigned to two morphotypes. Morphotype A generally shows laminar to low domical forms (low height/width ratio) exhibiting ragged margins and sediment inclusions within skeletons. In contrast, morphotype B consists of high domical growth forms (high height/width ratio) and lacks sediment inclusions. These differences in growth forms are interpreted to reflect different modes of biomineralization, together with environmental preferences of the individual organisms. Results of this study and previous publications, overall suggest a progressive development and diversification of biohermal biota in the middle to upper Ordovician of Tasmania. The scale and diversity of the Tasmanian bioherms are probably much smaller than the bioherms and reefs of the younger ages (Silurian and Devonian), and for stromatoporoids, the tendency of diversification is consistent with those of the other Ordovician sections. The Gordon Group provides useful information regarding the early evolutionary history of the Ordovician-Devonian reef-forming communities.     

Musteloids and feloids (Mammalia, Carnivora) from the late Miocene locality of Pikermi (Attica, Greece)

Some relatively rare carnivore remains from Pikermi are studied. The present specimens include Simocyon primigenius(ROTH and WAGNER, 1854), Promeles palaeatticus(WEITHOFER, 1888), Martes woodwardiPILGRIM, 1931, Felis atticaWAGNER, 1857 and Machairodus giganteus(WAGNER, 1848), as well as some postcranial remains that resemble Enhydriodon? latipesPILGRIM, 1931 and are assigned to Mustelidae gen. et spec. indet. Some of these species were not known until now but from their holotypes as M. woodwardi and E.? latipes. Other species such as F. attica and M. giganteus are better known but from relatively scant material. Since the material of the earlier mentioned species comes from Pikermi, their type locality, it is of especial importance and improves our knowledge for the Pikermi carnivores and their relationships to other species. In some cases where the material comes from ossiferous blocks, the accompanying faunal context is discussed.     

Oligocene swamp sediments of Lesvos Island,Greece (geochemistry and mineralogy)

Summary The Tertiary Lapsarna swamp sedimentary rocks include thin horizons (organic-rich sediments, up to 22% C_org). Analyses of major elements of carbonates, shaly and siliceous rocks, and a thin, intensively silicified coaly horizon were taken (10 representative samples). Pure carbonates consistalmost completely of calcite, the siliceous sediments of quartz and calcite, and the shales of montmorillonite, feldspar, quartz, dolomite and calcite. The shales contain montmorillonite as the only clay component. The presence of montmorillonite in all shales suggests that the chemistry of the clay-forming solutions lies within the stability field of montmorillonite. Geochemical data indicate that montmorillonite and associated immobile elements (La, Zr, Y, Nb) are the products of hydrolysis of volcanic material in a subtropical region. The intense silification of the coaly horizon is due to a contact with silica-rich solutions that formed during the formation of montmorillonite. Quartz is produced diagenetically by transformation of amorphous opal-A after burial.     

Hybridization and karyotype variability of three endemic Fritillaria L. (Liliaceae) in Argolis Peninsula (Greece)

Abstract

The Argolis Peninsula covers the north-eastern part of Peloponnisos and is surrounded by the Gulf of Argosaronic. The area hosts three species of the genus Fritillaria: F. graeca, F. rhodocanakis and F. spetsiotica. Fritillaria graeca is a Greek endemic taxon and its distribution includes Peloponnisos, C & E Sterea Ellas, C Evia and in proximity to Sterea Ellas, Salamis and Kea islands, while the stenoendemic F. rhodocanakis and F. spetsiotica are mainly found on Idra and Spetses islands respectively. The last two taxa are included in the Red Data Book of Rare and Threatened Plants of Greece, while F. rhodocanakis is also included in the IUCN Red List. Hybridization among them is a common phenomenon in the areas where they coexist, leading to an array of morphologically and karyologically intermediate forms. The current study presents the taxa’s karyomorphometric analysis for the first time and reveals hybrids’ cytological variety, including differences in marker chromosomes, polyploidy and the number of B-chromosomes.     

Upper miocene carbonate ramp deposits from the southernmost part of Maiella Nountain (Abruzzo, Central Italy)

Summary The development of carbonate ramp depositional systems in the Neogene of the Mediterranean Region represents a widespread feature so far analysed in several papers. It is striking to note that the evolution of upper Miocene carbonate ramps, characterized by the presence of coralgal bioherms, highlights the events leading to the Messinian salinity crisis. The coralgal bioherms of preevaporite Messinian age exhibit fossil assemblages indicating marine waters with normal salinity, whereas stromatolitic and microbial encrustations underline the deterioration of the environment during the Messinian salinity crisis. Maiella Mountain is a broad carbonate massif located in Abruzzo (Central Italy). The late lower Oligocene-Messinian part of its stratigraphic succession consists of stacked non-tropical carbonate ramp deposits related to third and higher order sequences. The investigations performed in the southernmost portion of the massif allowed to recognize a complete fourth order carbonate depositional sequence on a homoclinal ramp of pre-evaporite Messinian age. The presence of small coralgal patch reefs and overlaying microbial encrustations is significant. A transect exhibits the stratigraphic framework of the area. The data show how local parameters play a notable role in the development of these deposits.     

Late Triassic reefs from the Northwest and South Tethys: distribution, setting, and biotic composition

The paleolatitudinal distribution patterns during Ladinian and Carnian time are characterized by an increasing expansion of reefs from the northern to the southern hemisphere. The optimum of reef diversity and frequency in the Norian is associated with the development of extended attached or isolated carbonate platforms. Norian-Rhaetian sponge and coral reefs of the Northern Calcareous Alps developed (1) as reef belt composed of patch reefs in platform-edge positions facing the open-marine northwestern Tethys basins and (2) as patch reefs in intraplatform basins as well as in ramp positions.Carnian and Norian-Rhaetian sponge and coral reefs of the Arabian Peninsula are formed (1) as reef complexes at the margins of carbonate platforms on the tops of volcanic seamounts in the southern Tethyan ocean, as small biostromes on these isolated platforms, and (2) as transgressive reef complexes on the attached platform of the Gondwana margin. The Norian Gosaukamm reefal breccia of the NW Tethys is a counterpart of Jabal Wasa reefal limestone of the Gondwana margin with similarities in geological setting and biotic composition. Rhaetian coral biostromes of low diversity known from the Austrian Koessen basin resemble to the time equivalent Ala biostromes of the isolated Kawr platform in the southern Neo-Tethys by forming a discontinuous layer in shallow intraplatform basin setting.     

Dietary adaptations in an ungulate community from the late Pliocene of Greece

The dietary morphological methods of mesowear and microwear were applied to ungulates of the late Pliocene fauna of Sésklo (Thessaly, Greece). The results provide evidence for the predominance of open grassland in the area, as the most common species, Equus stenonis, was a strict grazer. The rare cervid cf. Croizetoceros ramosus was the only browser. The antelopes (genera Gazella and Gazellospira) yielded discrepant microwear and mesowear results. This is interpreted as an indication of regional or seasonal dietary resource differentiation, inferring that the antelopes were probably mixed feeders that grazed occasionally or periodically.     

Non-rigid cryptic sponges in oyster patch reefs (Lower Kimmeridgian, Langenberg/Oker, Germany)

Summary Two patch reefs which predominately consist of the oysterNanogyra nana (Sowerby 1822) are exposed in Lower Kimmeridigian strata of the Langenberg hillrange, central Germany. Left oyster valves making up the frame-work of the reefs formed small abundant cavities that were inhabited by a unique sponge community. The excellent preservation of non-rigid sponges was related to early organomineralization within the decaying sponge tissue. As a process of sponge taphonomy, different types of microbially induced carbonates precipitated preserving spicule aggregates. Organomineralization within sponge soft tissues is especially favored with the Langenberg patch reefs due to the closed or semi-closed system conditions with the cavities. The δ¹³C values ofin situ formed microbialities reveal that carbonate precipitation was in equilibrium with Jurassic seawater. The carbon of the microbialites does not derive from the bacterial remineralization of organic matter, but is of a marine source. Likewise, organomineralization is probably related to bacterial EPS or decaying sponge tissues providing an organic matrix for initial carbonate precipitation. Biomarker analyses revealed, that the patch reef microbialites contain terminally branched fatty acids (iso-andanteiso-pentadecanoic acid) in significant concentrations. These fatty acids, like hopanoid hydrocarbons, are most likely of a bacterial source. This is in agreement with sulfate-reducing bacteria remineralizing the decaying sponges as further indicated by the occurrence of framboidal pyrite in sponge microbialites.     

Prostrepsiceros and Protragelaphus (Artiodactyla,Mammalia) from the Late Miocene locality of Chomateri (Attica,Greece)

The Late Miocene fossiliferous locality of Chomateri is located close to the classic locality of Pikermi, but unfortunately its faunal context is not sufficiently known. Some fossil remains of spiral-horned antelopes from Chomateri are assigned to Prostrepsiceros rotundicornis and Protragelaphus skouzesi. The co-existence of P. rotundicornis and P. skouzesi is relatively rare in the Late Miocene, but well-documented in Pikermi. Comparisons of the Chomateri material support a middle Turolian age for the Chomateri locality and suggest a close chronological relation to the Pikermi fauna.     

The late Miocene bovids from Platania (Drama Basin,Greece), with description of a new species of Palaeoryx

This study presents the new fossil material of bovids from the recently discovered upper Miocene locality of Platania, Drama (Greece). The material was excavated from 2012 to 2016 and yielded approximately 760 specimens attributed to hipparions, rhinos, cervids, giraffids, suids, proboscideans, hyaenids, and turtles. The bovid material described here includes six taxa of Antilopinae and one of Bovinae. Antilopines are represented by Gazella sp., Gazella cf. ancyrensis, Prostrepsiceros aff. syridisi, cf. Palaeoreas, Palaeoryx minor nov. sp., and Tragoreas? aff. oryxoides. Bovines are recorded by a single boselaphine attributed to Miotragocerus sp. Departing from other Palaeoryx species, the new species P. minor has rather straight and weakly divergent horn-cores tilted backwards, obtuse facial and occipito-parietal angles, and smaller cranial and horn-core size, though associated with a proportionally large toothrow. Miotragocerus sp. from Platania seems to be conspecific to the Miotragocerus sp. from the end-Vallesian Nikiti-1 fauna (Greece). The bovid assemblage of Platania shows a mix of both Vallesian and Turolian taxa indicating a likely late Vallesian-early Turolian age.     

The mud mound nature of the Cassian Platform Margins of the Dolomites A case history: the Cipit boulders from Punta Grohmann (Sasso Piatto Massif, northern Italy)

Summary The sedimentological features and the microbiofacies of the Cassian platforms (Late Ladinian-Carnian) of the Dolomites can be studied only on the basis of the socalled “Cipit boulders”, that are platform-derived olistoliths and clasts fed to the basin and escaped to the extensive dolomitization affecting the buildups. Our paper deals with the Cipit boulders occurring in the Punta Grohmann section (Wengen and S. Cassiano formations, Late Ladinian, Archelaus and Regoledanus Zones). The dominant microfacies are represented by boundstone, consisting of nearly 60% of micritic limestone occurring both as peloidal or aphanitic micrite, mostly organized into stromatolitic laminites of thrombolites. The skeletal organism (Tubiphytes, skeletal cyanobacteria, sphinctozoan sponges, etc.) represent only a minor component of the rock (usually less than 10%). Early cements are widespread and consist both of fan-shaped calcite (replacing former aragonite), bladed isopachous magnesian calcite and radial-fibrous calcite (neomorphic after Mg-calcite). The carbonate platforms from which the olistoliths derive were made up mainly of carbonate mud that underwent early lithification, as witnessed by the considerable amount of early cements: therefore they may be regarded to as mudmounds, and more precisely as microbial mud-mounds, due to the clearly accretionary, organic-controlled nature of most micrites. The micrites, subdivided into auto- and allomicrite on the basis of micromorphological and fabric characteristics, have been tested for epifluorescence. The results confirm the organic control on the deposition of automicrite, also in the cases in which a microbial influence is not obvious (i.e. aphanitic micrite without internal organization).