Epiphytaceans occur in Late Jurassic shallow-marine reef limestones at several localities in the Carpathian Mountains of Romania. These calcified dendritic microfossils are well-preserved in sparry ...calcite as sub-millimetric radial clusters of narrow well-defined filaments, 10–30μm in diameter that show dichotomous branching and consist of dense dark micrite, locally with tubiform structure. Epiphytaceans are widely interpreted as photosynthetic algae or bacteria, but their precise affinities remain elusive and the group may be heterogeneous. These Late Jurassic examples most closely resemble Cambrian Tubomorphophyton and Late Devonian Paraepiphyton. We interpret them to be calcified cyanobacterial sheaths. Post-Devonian records of epiphytaceans are extremely scarce. The Kimmeridgian–Tithonian specimens reported here represent one of the youngest known occurrences of epiphytaceans. Their highly sporadic geological distribution resembles that of marine calcified cyanobacteria, which show Phanerozoic abundance peaks in the Early Paleozoic, Late Devonian–Mississippian, and Late Jurassic–Early Cretaceous. We propose that Kimmeridgian–Tithonian epiphytacean cyanobacteria reflect environmental conditions that favored bioinduced calcification, in particular elevated seawater carbonate saturation state.
•Epiphyton-like calcified cyanobacteria occur in Late Jurassic reefs in Romania.•This is the first definite record of these distinctive microfossils in the Mesozoic.•They could reflect seawater chemistry that promoted bacterial calcification.
The easternmost side of the Getic Carbonate Platform at Postăvaru and Piatra Mare Massifs of Southern Carpathians (Romania) has been studied through eighteen sections using macro and microscopic ...analyses, micropaleontological studies combined with sedimentological and oxygen and carbon isotope analyses. The studied area is located in central Romania, in the easternmost part of the Southern Carpathians, in the vicinity of the Carpathian Bend. Eight major facies associations are identified defining lower slope, upper slope/reef crest, platform margin and inner platform depositional environments. The microfossil assemblages contain foraminifera, dasycladalean algae, microproblematica and calpionellids characterizing the Tithonian and Berriasian stages. The carbonate succession shares similar characteristics with coeval deposits from the Southern Carpathians and other regions of the Tethys Realm (especially Northern Calcareous Alps, Polish Outer Carpathians, Carpatho-Balkanides, Albanides and Hellenides). The sedimentological and isotope chemostratigraphic analyses provide evidence that subaerial exposure was common in shallow-water and inner platform depositional settings, in a prograding context, under the influence of carbonate sedimentation and eustasy. All the investigations allow deciphering the Tithonian–Berriasian transition in the easternmost Getic Carbonate Platform.
This study summarizes and provides new data concerning the composition, fabrics, depositional environment and palaeogeographic distribution of Upper Jurassic–lowermost Cretaceous ...(Kimmeridgian–Berriasian) upper slope build-ups with complex microencruster-microbialite-calcified sponge frameworks associated with large amount of early marine cement crusts. The focus is on reef carbonates from the Štramberk-type limestones from the Carpathians (Getic Carbonate Platform) and Apuseni Mountains in Romania, with additional data from the Plassen Carbonate Platform (Northern Calcareous Alps, Austria) and the Štramberk Carbonate Platform (Western Carpathians, Czech Republic and Poland). The microencrusters, often of problematic biological affinity, are mainly Crescentiella morronensis (Crescenti 1969), Labes atramentosa Eliášová 1986 and Radiomura cautica Senowbari-Daryan & Schäfer 1979. Specialized encrusting calcified sponges are also common, with Perturbatacrusta leini Schlagintweit & Gawlick 2011 as the most abundant and characteristic form. Light-dependent microencrusters (e.g., “Lithocodium-Bacinella”) that are abundant in coeval overlying coral-dominated reefs, are rare, as are corals (microsolenids adapted to low-light level). Three dominant types of fabric-based framework varieties are considered for the studied build-ups. The main differences between these types reflect a bathymetric zonation in their development. The abundance of Crescentiella, microbialites, massive radiaxial fibrous cement crusts, and poorly diversified microencruster/sponge assemblages, are all suggesting that Type I framework variety is characteristic for build-ups formed in the deepest parts of an upper slope environment. Type II most probably developed at slightly lower depths than Type I, as revealed by its main features (clusters of calcified sponges and microencrusters associated with less extensive cement crusts) and distribution between the other two types in the sedimentary sequences. Type III, the most common, characterizes build-ups formed at the shallowest depths of the upper slope environment and is composed of alternating layers of diverse microencrusters (including several light-dependent species), calcified sponges, rare microsolenid corals, microbialites and early marine cement crusts. The distribution patterns of these framework varieties (Type I to Type III) together with their associated facies, strengthen this depositional interpretation. From a process-based perspective, these upper slope build-ups exemplify triple hybrid carbonates which are intimate combinations of microbial and skeletal components (microencrusters/microbialites and calcified sponges), associated with abiotic precipitates (early marine cement crusts). Their palaeogeographic importance is reflected in their formation on the slopes of rimmed carbonate platform systems facing open oceanic domains, predominantly within the central Western Tethys Realm. Such hybrid build-ups appear to have been absent on the southern European shelf where other reef frameworks commonly developed on carbonate ramps and ramp-type carbonate platforms.
•Recognition of Upper Jurassic–lowermost Cretaceous hybrid build-ups in the Western Tethys Realm.•Establishment of three main types of microencruster-microbialite-calcified sponge framework based on microfabric diversity.•Identification of key-elements for the recognition of carbonate platforms with the microbial factory on their slopes.•Implications for palaeogeographic reconstructions of the central-Western Tethys Realm.
We studied deposits belonging to the Bihor Unit from the Northern Apuseni Mountains (Romania). The described outcrops are located in the SW of Șes Mountain and the northeastern Pădurea Craiului ...Massif. We determined the depositional environment and the mechanisms controlling the accumulation of Upper Triassic–Lower Jurassic continental deposits. The sedimentary formations contain carbonate breccia and calcretes embedded in continental clay deposits. Late Triassic–Early Jurassic depositional processes were influenced by the inherited paleobasement of the subaerially exposed Middle Triassic deposits. Numerous fragments of Anisian and Ladinian carbonate deposits are encased in weathered clay deposits accumulated on karstification surfaces developed at the top of Middle Triassic limestones. We integrated facies analysis and clay mineralogy to obtain an accurate interpretation of the continental processes acting at the Triassic–Jurassic boundary in the northern part of the Apuseni Mountains. The composition of the carbonate pebbles is described in terms of the carbonate facies, whereas the clay mineralogy was determined by applying X-ray powder diffraction. Thirteen facies associations are described consisting of carbonate, siliciclastic and ferilitic rock types. Such facies indicate sediment accumulation in a continental, mixed carbonate-siliciclastic depositional environment. A Late Triassic exposure event was followed by an Early Jurassic (Hettangian) transgression. Two major facies types are identified on the basis of their depositional environment. The first category includes subaerially exposed Triassic carbonates and ferilitic facies, while the second category consists of transgressive siliciclastic facies from the basal Lower Jurassic (Hettangian) sediments. The existing data suggest continental deposition in alternating, arid–humid warm climate conditions at the Triassic–Jurassic transition.
The lowermost Cretaceous carbonate deposits of the Carpatho–Balkanides (Eastern Serbia), which crop out in the Kučaj zone, were studied in three sections: Kamenica, Prekonozi and Jerma River Canyon. ...The identified micropalaeontological assemblages generally consist of calcareous green algae (mainly dasycladaleans), benthic foraminifera (mainly orbitolinids, cyclaminids, pfenderinids), and scarce calpionellids. The dasycladalean algal association comprises mostly species known from the Berriasian–lower Valanginian. The same age is also indicated by the majority of the identified benthic foraminifera, except for the orbitolinids from the upper parts of the sampled successions that hitherto were only known from the upper Hauterivian–lower Aptian of Southern France and Northern Spain. The co-occurrence of Berriasian–lower Valanginian algae and benthic foraminifera with Hauterivian–Aptian orbitolinids challenges establishment of the age of the sampled succession and, potentially, other carbonate successions too. The recognition of rare calpionellid specimens in samples containing orbitolinids can resolve this dilemma. Calpionellids are planktonic microfossils with a well-defined stratigraphic distribution within the Neotethyan realm; consequently, the identified species belonging to the Calpionellopsis zone confirm a late Berriasian age. In addition, it should be emphasized that some of the orbitolinids known until now only from upper Hauterivian–lower Aptian deposits were already present in the studied region from the base of the upper Berriasian.
We carried out combined micropaleontological, microfacies and multivariate statistical analyses of benthic foraminiferal assemblages on a previously undocumented lowermost Cretaceous carbonate ...succession from the western part of the Getic Carbonate Platform (Pui-Bănița zone, Southern Carpathians). The microfacies analysis and interpretations suggest that these limestones were developed under peritidal settings within different zones of a shallow-water inner platform paleoenvironment (bioclastic grainy bars, subtidal–intertidal flats and intertidal–supratidal ponds), where benthic foraminifera, microbial microstructures and calcareous algae were the main carbonate producers. The well-preserved micropaleontological content (mostly benthic foraminiferal assemblages) is important for lowermost Cretaceous Neotethyan biostratigraphy and allows the recognition of the Valanginian stage within this part of the Getic Carbonate Platform. The multivariate data processing (diversity indices, cluster analyses and principal components analyses) performed on the benthic foraminifera assemblages provide valuable information about their compositional patterns, diversity trends and spatial distribution with respect to the main facies zones. The results obtained through these analyses are extremely useful for the recognition of common/different paleoecological features and for a more precise interpretation of depositional paleoenvironments.
•Combined micropaleontological, microfacies and multivariate statistical analyses.•Important biostratigraphic arguments for the Berriasian–lower Valanginian.•Diversity indices reflect strong facies control over species richness and the spatial distribution of species.•A more accurate interpretation of the paleoenvironmental/paleoecological conditions.
Piatra Craiului Massif is situated in the easternmost part of the Southern Carpathians, Romania. The Kimmeridgian–lowermost Valanginian carbonate succession from this area is part of the large Getic ...Carbonate Platform system, and forms a 25 km long, NE-SW oriented calcareous ridge with a maximum thickness of 1200 m. Previous studies of Upper Jurassic-Lower Cretaceous carbonate platforms from Romania focused on microfacies and biostratigraphic features but few studies addressed their sequence stratigraphy. This study aims to decipher the geological evolution of the Eastern Getic Carbonate Platform by integrating sequence stratigraphic, biostratigraphic and chemostratigraphic analysis methods. The studied sections are located in the northern and central part of the Piatra Craiului Massif. Centimeter to meter thick carbonate beds or banks are common and carbonate lithologies reveal five facies associations (F1F5) of outer platform deposits and inner platform peritidal settings. The outer platform deposits contain fragments of subaerially exposed intraclasts. Such processes are indicated by the facies characteristics and isotope chemostratigraphy data. The peritidal succession is characterized by the repetition of distinct sets of small-scale sequences, each of which commonly shows a deepening to shallowing upward trend. This trend is defined by a vertical scale transition from high-energy intertidal deposits to intertidal restricted ponds, swamps or supratidal marshes. The general trend shows a shallowing upward tendency. Commonly, intertidal deposits cap the shallowest facies of the corresponding small-scale sequences. The entire peritidal succession from the Piatra Craiului Massif forms a superimposed prograding wedge on platform margin deposits. Autocyclic processes and allocyclic processes appear to be responsible for the development of this carbonate succession.
Lower Cretaceous successions that crop out in the eastern part of the Getic Carbonate Platform (Southern Carpathians, Romania) preserve records of the Valanginian events in different settings of the ...platform. The integrated sedimentological, biostratigraphical, geochemical and mineralogical analysis of the upper Berriasian–Valanginian successions reveal successive stages in the evolution of the carbonate platform: (a) pre-drowning stage of the shallow-shelf and slope settings of the platform; (b) subaerial exposure and karstification; and (c) incipient flooding and drowning of the carbonate platform. Following the subaerial exposure, starting in the middle early Valanginian, the eastern part of the Getic Carbonate Platform experienced a drowning phase documented by iron oxyhydroxides, phosphate and glaucony mineralized discontinuity surface and glaucony-rich sediments disposed on the discontinuity surface. Recognition of the diachronous intra-Valanginian discontinuity surface within the studied successions is based on clear evidences (facies contrast, depositional and diagenetic features, biostratigraphic and taphonomic data, and geometrical relations). The negative–positive carbon isotope excursion is correlated with the global perturbations of the carbon cycle related to the Valanginian “Weissert” episode, and it is documented for the first time in the shallowest parts of the Getic Carbonate Platform. Tectonic activity and eustatic sea-level fluctuations were most probably the main factors that led to fault-block tilting, local emersion and subsequent drowning of the eastern part of the Getic Carbonate Platform during the Early Cretaceous. We infer that the eastern part of the Getic Carbonate Platform was affected by late Berriasian–early Hauterivian extensional tectonics that could be related to the Neo-Cimmerian movements with effects generally recognized in the northern peri-Tethyan areas.
•We document the early Cretaceous drowning history of the Getic Carbonate Platform.•The drowning event was related to extensional tectonics and eustatic fluctuations.•The drowning event was preceded by subaerial exposure and karstification.•The biostratigraphic data indicates Lower Valanginian stratigraphic gaps.•The carbon-isotope data correspond to the global Valanginian Weissert episode.
The shallow-marine, mixed siliciclastic-calcareous Late Cretaceous deposits from the Apuseni Mountains have been extensively studied and compared to coeval deposits from the Alpine Gosau. The former ...are mainly represented by conglomerates, sandstones, marls, and limestones with rudists that unconformably overlie the crystalline basement and its Permo-Mesozoic cover. Our new, detailed investigations on the rudist fauna from Măgura Hill, the type locality of Pseudopolyconites hirsutus (Patrulius) and Miseia costulata Patrulius, indicate a Late Santonian–Early Campanian age for these deposits instead of an Early Santonian one as previously suggested (Patrulius, 1974). This study also mentions for the first time the occurrences of Pseudosabinia klinghardti (Böhm) and Pseudopolyconites parvus Milovanović in the rudist-bearing deposits from the Apuseni Mountains. We include their palaeontological features, as well as the ones for Pseudopolyconites hirsutus. Based on new biostratigraphic data, our study expand the stratigraphic range of Pseudosabinia klinghardti and Pseudopolyconites parvus – previously considered characteristic for the Early Campanian–Maastrichtian interval. Also we add new information on their palaeobiogeographic distribution within the central-eastern Mediterranean area during the Late Cretaceous.
•We study the rudist fauna from type locality of P. hirsutus and M. costulata.•We reveal a Late Santonian–Early Campanian age of deposits instead of Early Santonian.•Pseudosabinia klinghardti and P. parvus are first time reported in Romania.•In this study we present a taxonomic analysis of these rudist species.•We show the palaeogeography and stratigraphy of these species during Late Cretaceous.
The middle Miocene carbonates from the NW part of the Transylvanian Basin are represented mainly by rhodalgal facies. This paper provides an accurate taxonomic account of the red algal assemblages, ...facies analysis, and paleoenvironmental interpretation of the Badenian deposits outcropping in Vălenii Șomcutei area. A total of 13 red algal species belonging to the orders Corallinales, Hapalidiales, Sporolithales, and Peyssonneliales have been identified. The microfacies distinguished in the succession (bio-extraclastic grainstone, oolitic packstone/grainstone, bio-extraclastic packstone/grainstone, rhodolith rudstone, coralline algal rudstone, and coralline algal debris grainstone) suggest a general shallowing-upward succession, from an open-marine middle-outer ramp setting to an inner-ramp environment.
