Hydrothermal vent myodocopid ostracods from the Eifelian (Middle Devonian) of southern Morocco

A monospecific assemblage of myodocopid ostracods has been found in the Middle Devonian of a unique hydrothermal vent system of Hamar Laghdad (eastern Anti-Atlas, southern Morocco), which developed over a submarine eruption of basaltic rocks. This fauna has been recovered from a neptunian dyke representing the sediment infill of an Eifelian venting fissure discovered in the central part of Hamar Laghdad. The assemblage consists of thousands of relatively large shells forming a coquina layer in which the valves are disarticulated, perfectly washed, well sorted and stacked into each other. Their orientation points to transport due to fluids migrating in the vent system. The ostracod specimens, on the base of the general outline, the presence of rostrum and rostral incisure is assigned to the order Myodocopida. The new genus and species Hamaroconcha kornickeri is proposed, most likely representing a new family. Its carapace morphology gives no clear clue to its mode of life; however, a relatively long rostral incisure may suggest that frontal appendages of this species were sufficient for active swimming. Therefore, a nectobenthic lifestyle is postulated for H. kornickeri nov. gen., nov. sp. Isotope data from the sediment infill provide evidence for the activity of hydrothermal fluids.     

Iron bacteria in Devonian carbonates (Tafilalt, Anti-Atlas, Morocco)

A condensed Mid-Upper Devonian succession of the Tafilalt (Anti-Atlas) contains numerous red carbonate intervals. Bioclastic tempestites form a transition between an outer shelf and a hemipelagic setting. The red pigmentation is not related to the abundance of detrital iron oxides, but to the presence of iron bacteria and fungi. They form bioconstructions remarkably similar to those previously described in the Jurassic Ammonitico Rosso from Italy and Spain. Thus, dysaerobic microenvironments are proposed and not oxic conditions for these Fe-poor sediments.     

A late Devonian (Frasnian) coral-bafflestone reef at Houshan in Guilin, South China

Summary Givetian to early Carboniferous sediments of South China are characterized by carbonates. Middle and Late Devonian strata are best developed in the Guilin area. Reefs and organic shoals are recorded by various lithofacies types indicating the existence of an extended carbonate platform and a change of the composition of reef communities in time. Starting in the late Devonian, stromatoporoids and corals were replaced by algae that subsequently played an important role together with stromatoporoids, receptaculitids and fasciculate rugose corals in reef communities. In Houshan, 5 km west of Guilin, a coral-bafflestone reef occurs in the Frasnian strata, situated near an offshore algal-stromatoporoid reef. The coral reef was formed in a back-reef area adjacent to the inner platform margin. The coral-bafflestone reef is unique among the late Devonian reefs of South China with regard to the biotic composition. The reef is composed of fasciculate colonies ofSmithiphyllum guilinense n. sp. embedded within in packstones and wackestones. The height of colonies reaches 1 m. The community is low-diverse. The species ofSmithiphyllum occurring in the Frasnian reef complexes of Guilin exhibit a distinct facies control:Smithiphyllum guilinense occurs in or near to margin facies and formed bafflestone, constituting a coral reef whereasSmithiphyllum occidentale Sorauf, 1972 andSmithiphyllum sp.—characterized by small colonies with thin corallites—are restricted to the back-reef and marginal slope facies. The bush-like coral colonies baffled sediments. Algae and stromatoporoids (mainlyStachyodes) are other reef biota. Reef-dwelling organisms are dominated by brachiopods. The reefs are composed from base to top of five lithofacies types: 1) cryptalgal micrite, 2) peloidal packstone, 3) stromatactis limestone, 4) coral-bafflestone, and 5) pseudopeloidal packstone. The reef complex can be subdivided into back-reef subfacies, reef flat and marginal subfacies, and marginal fore-slope subfacies. The Houshan coral-bafflestone reef is not a barrier reef but a coral patch reef located near the inner margin of a carbonate platform.     

Signatures of hydrocarbon venting in a Middle Devonian Carbonate Mound (Hollard Mound) at the Hamar Laghdad (Antiatlas, Morocco)

Summary The Middle Devonian Hollard Mud Mound is situated in the eastern Hamar Laghdad, which is a small mountain range in the Tafilalt in SE Morocco. In contrast to the well known Lower Devonian Kess-Kess mounds, the Hollard Mound is of Middle Devonian age. The facies in the core of this mud mound differs from that of the other parts of the mound, and exhibits signatures of ancient hydrocarbon venting. The carbonate phases of the core facies are derived from the oxidation of vent fluids and consist of clotted micrite, a cryptocrystalline carbonate associated with spheres of uncertain origin, and a calcitic rim cement (rim cement B). These vent carbonates show δ¹³C values in the range of −11 to −20% PDB indicating that some of their carbon is derived from isotopically light hydrocarbons. Fossiliferous micrite has been affected by hydrocarbon venting in the proximity of the vent site, which is indicated by intermediate δ¹³C values between vent carbonates and not affected sediments. Bivalves occur in dense populations within the core facies. They form autochthonous shell accumulations and are almost exclusively articulated. it is likely that these bivalves were dependent on chemosynthesis similar to their counterparts at modern vents. The vent deposits also exhibit an unusual prasinophyte assemblage, which might have been linked to the specific nutrient availability at the vent site. The ancient vent site is characterized by an enhanced carbonate precipitation and rapid lithification. The latter is corroborated by the three-dimensional preservation of phytoplankton (prasinophytes and acritarchs) and the occurrence of stromatactoid pores. An early phase of carbonate corrosion predating the formation of vent carbonates affected the fossiliferous micrite of the core facies and is thought to be related to a phase of H₂S-rich venting.     

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.     

Miospore stratigraphy of Lower and early Middle Devonian deposits from Tidikelt, Central Sahara, Algeria

The Tidikelt region forms an outstanding area for subsurface Lower Devonian stratigraphy in the central Algerian Sahara. Sediments from five boreholes have revealed abundant and diverse assemblages of miospores, acritarchs, chitinozoa, scolecodont and microplant remains. The miospores are moderately well preserved. Three new miospore species (Dibolisporites saharansis nov. sp. Hassan Kermandji, Acinosporites conatus nov. sp. Hassan Kermandji and Scylaspora tidikeltense nov. sp. Hassan Kermandji) are described. Miospore assemblages vary through the regressive and transgressive sequences. Seven miospore assemblage biozones, including six new miospore assemblage biozones (Scylaspora tidikeltense-Perotrilites microbaculatus, Dictyotriletes emsiensis-Emphanisporites spinaeformis, Apiculiretusispora arenorugosa-Camptozonotriletes caperatus, Verrucosisporites polygonalis-Dictyotriletes subgranifer, Emphanisporites annulatus-Geminospora svalbardiae, Hystricosporites microancyreus-Grandispora protea, Calyptosporites velatus-Rhabdosporites langii) are proposed for the Lower and early Middle Devonian rocks of Tidikelt Plateau. The combined use of distinctive, wide distribution cosmopolitan and Gondwanan forms as biozonal and species characteristics permits accurate subdivision, dating and correlation of Tidikelt successions with other similar miospore zones of the Lower Devonian of Europe, Canada and other parts of Gondwana plate. The miospore data provide new explanations to stratigraphic relationships of regional rock units, sedimentary cycles and stratigraphic hiatus. The miospore biozones are proposed as a provincial biozonation, which may also be applied to other Palaeozoic rocks of similar miospore content.     

Vent and mound rugose coral associations from the Middle Devonian of Hamar Laghdad (Anti-Atlas, Morocco)

Peculiar associations of small, solitary, deep-water rugose corals are described from the Middle Devonian buildups situated in the easternmost part of Hamar Laghdad area of southern Morocco. The most of them are monospecific and consist of simplified taxon “Amplexus” florescens but one is polyspecific and composed of specimens belonging to four different species representing three families. These rugosan associations form isolated nest-like aggregations where numerous densely packed specimens are arranged mostly in life position. The polyspecific and two monospecific associations are interpreted as growing in close proximity to venting fields. They reveal a unique “calice-in-calice” recolonization pattern expressed by successive settlement of juvenile specimens in the calice of dead individuals. This pattern was presumably a consequence of selective survival of coral larvae settling in extreme vent habitats. Although, the “calice-in-calice” pattern is common in both, mono- and polyspecific associations, there are differences expressed in the character of larval attachments and various types of the calice fillings. The trophic interaction between corals and ostracods is discussed. Additionally, associations of “Amplexus” florescens, not displaying “calice-in-calice” pattern of growth have been found within the mound where polyspecific association occurs. These are interpreted as growing away from venting fields. Comparisons of Amplexus-type coral faunas with the other North African and European corals allow the classification of these ampleximorph rugosan taxa as characteristic biotic components of the Middle Devonian mound environments influenced by venting activity. Two new genera and species, Weyeraia prima and Vesiculolasma erfoudi, are introduced.     

Earliest vertebrate embryos in the fossil record (Middle Devonian,Givetian)

Serial sectioning of a nodule encapsulating an adult specimen of the arthrodire placoderm Watsonosteus fletti from the Eday Flagstone Formation (Givetian) in the Orcadian Basin of northern Scotland has revealed the presence of a number of embryos within the adult. This specimen represents the oldest known record of fossilized vertebrate embryos. Thin sections of two of the slices have revealed the detailed histological structure of embryonic plates in placoderms, showing that as previously deduced from visual examination, the outer and inner layers were the first to form. Gut contents preserved near the embryos show that the species had a varied diet, with dermal bone fragments from sarcopterygians and placoderms.     

Microfacies analysis and palaeoenvironmental interpretation of Lower Oligocene, shallow-water carbonates (Gornji Grad Beds, Slovenia)

Summary The microfacies and palaeoenvironment of Lower Oligocene carbonates of the Gornji Gradbeds from Slovenia are investigated. These beds form part of a transgressive succession overlying both terrigenous sediments (sand-stones and conglomerates) and marine carbonates of Eocene age as well as transgressing directly over Triassic lime-stones. They are followed by foraminiferal rich marls. The carbonates were investigated using multivariate statistical techniques on point counts of thin sections. They are dominated by poorly sorted biogenic rudstones with pack-/wackestone matrix; pack- and grainstones are subordinate. The biogenic components of the carbonates are dominated by coralline red algae (9 genera with 11 species), corals, small benthic, large benthic, and encrusting foraminifera as well as bivalves. Gastropods, bryozoans, brachiopods, echinoderms, serpulids, and green algae are subordinate. The well preserved components allow details pertaining to taxonomy, growth-forms and taphonomic features to be observed. The following carbonate facies are distinguished: 1) nummulitic, 2) bivalve, 3) foraminiferal—coralline algal, 4) grainstone, 5) coralline alga, 6) coralline algal—coral, and 7) coral facies. All the carbonate facies represent fully marine conditions within the photic zone. They are interpreted with respect to substrate composition and stability, water turbulence, terrigenous input and light.     

Palynological investigation of Holocene palaeoenvironmental changes in the coastal plain of Marathon (Attica, Greece)

The identification of Middle-Late Holocene palaeoenvironmental conditions of the Marathon coastal plain gained great interest in the last decades due to its high environmental and archaeological importance. Palynological analysis of samples from two boreholes and two trenches along a transect in the marshy area of the Marathon coastal plain, enabled the tracing of the vegetation and the main environmental changes for the last ∼6000 cal BP. Pollen data suggest a human disturbed environment with Pinus, Quercus, Juniperus and Ericaceae, while a general trend towards Mediterranean vegetation patterns is observed during the last ∼3000 cal BP. Pollen grains from aquatic and hydrophilous plants, dinoflagellate cysts, algal remains and other palynomorphs were used in order to determine the local depositional environment and its evolution through time.     

Stratigraphy, geometry, and facies of a Middle Devonian ramp-to-basin transect (Eastern Anti-Atlas, SE Morocco)

Summary In the castern Anti-Atlas (SE Morocco), a small sedimentary basin (Mader Basin) evolved during the late Palacozoic. The Middle Devonian deposits consist of shales and limestones with a thickness up to 700 m in the depocentre. Sedimentary structures and sole marks of Middle Devonian limestones indicate transport from the northwest and the south towards the basin centre, located in the central Mader area. Lithostratigraphic, biostratigraphic, and dynamic stratigraphic approaches were applied to correlate stratigraphic sections. Five correlatable large-scale base-level hemicycles were recognized in the Middle Devonian succession. Thickness trends of Middle Devonian deposits, regional correlations, and facies-trends reveal the geometry of a carbonate ramp. The carbonate ramp was slightly inclined (<1°) to the NE. A sedimentary wedge, consisting of limestones and limestone/marl alternations, was deposited during the Eifelian and marks the transition from the ramp to the adjacent basin. Middle Devonian water depths are estimated as close to and within the storm wave-base at the southern area of the ramp and far below storm wave-base in the northeastern part of the ramp. Shallowest conditions (inner-ramp environment), close or within the fairweather wave-base, existed during the early Givetian as documented by the abundance of recfal fauna (stromatoporoids, corals) and calcimicrobes (lumps, micritic envelopes) in the eastern and southeastern area of the ramp.     

Stratigraphy and facies of an oligocene fringing reef (Castro Limestone,Salento Peninsula,Southern Italy)

Summary The coastline of the Salento Peninsula (Apulia region, Southern Italy) is characterized by a rocky shore with spectacular cliffs where the investigated fringing reef complex, the so called Castro Limestone, spectacularly outcrops for at least 40 km. As reconstructed from several measured sections, the Castro Limestone, which is Middle Chattian in age from our own data, disconformably mantles a tectonically deformed falaise of Cretaceous-Eocene rocks and is overlain by a remarkable erosional surface characterized by a very peculiar rhodolite rudstone. The Castro Limestone unit can be considered as a classic unconformity bounded depositional sequence representing, most probably, a shelf margin prograding complex, related to the major Middle Oligocene sea level lowstand. Stratigraphic and sedimentologic features, together with paleontological characters, allow recognition of a virtually complete range of reef environments across the reef profile. Several geomorphic zones and associated facies are described, from the most landward reef area (‘back reef’) across the reef flat and reef from downward to the fore reef slope, contributing to a better knowledge of the evolution of Oligocene reefs and reef communities in Italy and in the Mediterranean area.     

Epizoans immured in the heterocoral Oligophylloides maroccanus Weyer, 2017: a unique record from the Famennian (Upper Devonian) of Morocco

Exceptionally well-preserved proximal parts of colonies of the late Famennian heterocoral Oligophylloides maroccanus Weyer, 2017 with immured epizoans are described here from the Jebel Bou Ifarherioun ridge of the eastern Anti-Atlas, Morocco. This is the first evidence of unique syn vivo interactions between a heterocoral and numerous epizoans, that is the colonial tabulate corals Zemmourella? sp. and Aulopora? sp.; solitary rugose corals Czarnockia? sp. and Gorizdronia? sp.; and other juvenile, undeterminable solitary rugosans, crinoids, as well as microbial structures. Detailed analysis of sectioned specimens allowed mutual interactions to be traced during growth of the host and infesting encrusting taxa. The studied associations show that the epizoans must have settled on the proximal parts of Oligophylloides in places devoid of soft tissue. The encrusted proximal portions of the colonies show that soft tissue of the heterocoral could have retracted and expanded again, fouling and immuring dead epizoans. The process of bioimmuration is perfectly marked by thin layers of microbial encrustations developing on the epibiont skeletons prior to their overgrowth by the skeleton of the heterocoral. The studied encrustations seem to be widespread, but the association provided the epizoans with additional substrate for encrustation, as well as an elevated position above the seafloor, beneficial for access to nutrients. We suggest that the host bioimmured the encrusters after their death, because of noticeable microbial encrustations and veneers of sediment, a lack of malformations, relatively rapid growth and aggressive activity of epizoans.     

Stromatoporoid palaeoecology in the Frasnian (Upper Devonian) Belgian platform,and its applications in interpretation of carbonate platform environments

Abstract: Stromatoporoid faunas in the Frasnian of southern Belgium are abundant in the carbonate platform environments present in this area. Stromatoporoids dominate the large skeletal organisms and occur principally in biostromes. The stromatoporoid assemblage is represented by a small number of taxa. Stromatoporoid genera include Actinostroma, Amphipora, Atelodictyon, Clathrocoilona, Salairella, Stachyodes, Stictostroma, Stromatopora and Trupetostroma which are present in environments ranging from the outer, outer intermediate, inner intermediate and inner zones and associated biostromes. Most large skeletal stromatoporoids are low profile, which reinforces the conclusions of previous studies that low‐profile growth forms were the most successful stromatoporoid forms. These low‐profile forms are likely to have been important sediment stabilisers that may have led to expansion of the carbonate factory. Growth forms vary between facies, indicating some degree of environmental control on form; for example, laminar in the intermediate zone, bulbous and domical in the inner and outer zones. Stromatoporoid taxa vary in occurrence across the environmental gradient from shallow to deep. There is some taxonomic control on growth forms, with some taxa showing more variability than others in different environments.     

A neotype for Colpodexylon gracilentum Dou (Lycopsida) from the Middle Devonian of North Xinjiang,China

Abstract According to newly collected and well preserved specimens, herbaceous lycopsids Colpodexylon gracilentum Dou and Colpodexylon laminatum Dou from the late Middle Devonian of Xinjiang, NW China are reduced to C. gracilentum, for which a neotype is designated and emended diagnosis is given. Colpodexylon gracilentum has leaves with three nearly equal segments, an elliptical sporangium adaxially attached by a pad on the isomorphic sporophyll.     

A neotype for Coipodexylon gracilentum Dou (Lycopsida) from the Middle Devonian of North Xinjiang, China

According to newly collected and well preserved specimens,herbaceous lycopsids Colpodexylon gracilentum Dou and Colpodexylon laminatum Dou from the late Middle Devonian of Xinjiang,NW China are reduced to C.gracilentum,for which a neotype is designated and emended diagnosis is given.Colpodexylon gracilentum has leaves with three nearly equal segmems,an elliptical sporangium adaxially attached by a pad on the isomorphic sporophyll.     

Restudy and reassignment ofDentalium antiquum Goldfuss, 1841 (Middle Devonian)

Dentalium antiquum is one of two moderately well-known Devonian “scaphopods” in the German literature. Examination of the type material and a few specimens in other institutions indicates more individual variability than is to be expected in species of the molluscan class Scaphopoda. The species is transferred with question toColeolus Hall, a fossil presumed to be a calcareous “worm” tube.