Carbonate Platform Research Articles

Suprasubduction ophiolite (SSZ) components in a middle to lower upper Jurassic Hallstatt Mélange in the Northern Calcareous Alps (Raucherschober/Schafkogel area)

The Northern Calcareous Alps in the Western Tethys realm were affected in Middle to Late Jurassic times by a mountain building process triggered by ophiolite obduction similar to that in the Inner Western Carpathians or Inner Dinarides. In contrast to these other mountain ranges, in the Northern Calcareous Alps the obducted ophiolites or ophiolite derived components in the Bathonian-Oxfordian mélanges are missing. Cr-spinels in Kimmeridgian basinal deposits are the oldest known relics of a Jurassic ophiolite obduction. This study reveals new data from a newly detected Hallstatt Mélange below the Late Jurassic Plassen Platform in the southeastern Northern Calcareous Alps (Raucherschober/Schafkogel area). Upper Triassic Hallstatt Limestone blocks from the former distal northwestern continental margin of the Neo-Tethys Ocean, as well as ophiolite and radiolarite blocks from the Neo-Tethys Ocean floor rest within an upper Middle to lower Upper Jurassic radiolaritic-argillaceous matrix. Ophiolitic blocks show calc-alkaline volcanic arc affinity, defining the rocks as the product of intra-oceanic subduction and the formation of an early arc during stacking of the oceanic crust. Resedimented ribbon radiolarite blocks deposited above the newly formed suprasubduction (SSZ) ophiolites in the Neo-Tethys Ocean east of the island arc have a Middle Jurassic age. Later, at a time of decreasing tectonic activity, the Hallstatt Mélange was sealed by the Kimmeridgian-Tithonian Plassen Carbonate Platform, showing a shallowing-upward trend.

Geochemical records in subaerial exposure environments in Croatia using discriminant function analysis of bauxite data

Croatian bauxites are long known for their chemical and physical diversity arisen from their characteristic origin and emplacement within the area of the Adriatic–Dinaric carbonate platform (ADCP). They include eight horizons spanning the period between the Upper Triassic (Carnian) and the Miocene, formed on subaerially exposed platform paleoenvironments. The bauxite genesis is recorded in the bauxite geochemical composition as a unique signature of tectonostratigraphic evolution of the different parts of the Croatian Karst, including, for example, the forebulge unconformity typical for the Istrian area. In this work, an explanation of the typical patterns of bauxite formation is based on the construction of a discriminant function model (DFM) resulting from the compositional data (CoDa) analysis of bauxite geochemical data (major and trace elements). The model shows that the greatest part of the variation contained in the analyzed bauxite data (the first discriminant function, DF1) is associated with systematic alteration of geochemical composition in time, emphasizing characteristic decrease in clay component and gradual enrichment in heavy metals from oldest (Upper Triassic) to the youngest (Miocene) bauxites. In the general scheme, particular bauxite horizons represent standalone groups (Upper Triassic) while others form clusters showing increase and/or decrease of a particular set of elements signaling the changes in environmental conditions during the considered geological history of ADCP. Other discriminant functions (DF2 and DF3) also contribute to the all-inclusive distinction between the eight a priori defined bauxite groups discriminated by the characteristic set of geochemical variables where DF2 typically refers to the process of desilication, while DF3 to that of deferralitization.

Astrochronology and carbon-isotope stratigraphy of the Fengcheng Formation, Junggar Basin: Terrestrial evidence for the Carboniferous-Permian Boundary

The Carboniferous–Permian Boundary (CPB) is a major stratigraphic boundary and a marker for global stratigraphic correlation. However, the delimitation and global correlation of the CPB is hindered by the erosion during the Late Paleozoic Ice Age. Several carbonate platforms show a negative carbon isotope excursion (NCIE) in response to the CPB, which has great potential for the delimitation of this boundary. However, the response of terrestrial profiles to the CPB is unclear, and the global synchroneity of this NCIE is controversial. We studied a high paleolatitude section to evaluating the feasibility of the NCIE for delimitating CPB. We used astrochronological analysis of the 340 m Gamma Ray log of the Fengcheng Formation in Mahu Sag, Junggar Basin, northwest China, where the CPB may have been recorded. We constructed a high-resolution chronostratigraphic framework for the Fengcheng Formation, which precisely defines the chronostratigraphic attribution of the Fengcheng Formation as the Gzhelian–Asselian, and confirms that the CPB is recorded in the Fengcheng Formation. In addition, a global correlation of carbon isotope profiles revealed a negative excursion in terrestrial carbon isotope profiles across the CPB, which is consistent with the characteristics of NCIEs in several marine profiles. The similarity of the NCIE records supports their global synchrony and confirms that they can be used to delimit the CPB in terrestrial sections. Combining the astronomical time scale and the carbon isotope profile, we constrain the position of the CPB to the depth range of 4694.84–4703.56 m, with 4698.9 m as a preliminary estimate of the CPB. This new astronomical timescale and the stratigraphic position of the CPB enable the revision of the chronostratigraphic attribution of the terrestrial strata in the Junggar Basin. Overall, our results contribute to studies of the Carboniferous–Permian global carbon cycle, high-latitude glaciation, eustatic fluctuations, global volcanism, and their potential relationships.

Corpus of Carbonate Platforms with Lexical Annotations for Named Entity Recognition

An obviously challenging problem in named entity recognition is the construction of the kind data set of entities. Although some research has been conducted on entity database construction, the majority of them are directed at Wikipedia or the minority at structured entities such as people, locations and organizational nouns in the news. This paper focuses on the identification of scientific entities in carbonate platforms in English literature, using the example of carbonate platforms in sedimentology. Firstly, based on the fact that the reasons for writing literature in key disciplines are likely to be provided by multidisciplinary experts, this paper designs a literature content extraction method that allows dealing with complex text structures. Secondly, based on the literature extraction content, we formalize the entity extraction task (lexicon and lexical-based entity extraction) for entity extraction. Furthermore, for testing the accuracy of entity extraction, three currently popular recognition methods are chosen to perform entity detection in this paper. Experiments show that the entity data set provided by the lexicon and lexical-based entity extraction method is of significant assistance for the named entity recognition task. This study presents a pilot study of entity extraction, which involves the use of a complex structure and specialized literature on carbonate platforms in English.

Middle Eocene (Lutetian-Bartonian) larger benthic foraminifera assemblages from Batman and Siirt (Southern Neotethys, SE Turkey): a new assessment

The benthic foraminifera assemblage has been described in the limestones outcropped in Kurtalan and Eruh district of Hoya formation which is one of autochthonous units of Arabian Platform (SE Turkey). From the two measured sections, one of them has rare fossil content due to dolomitization (DH-Dodan section),while the other is fairly remarkable in terms of fossil content (EH-Eruh section). The foraminiferal assemblages are represented by Asterigerina rotula (Kaufmann), Operculina ex. gr. gomezi Colom and Bauza, Victoriella conoidea Rutten, Amphistegina sp., Elphidium sp., Peneroplis sp., Carpenteria sp., Stomatorbina sp., miliolid and rotaliid forms and echinoderms, coral fragments in the Dodan section. The foraminiferal assemblages are represented by Nummulites biedai Schaub, Nummulites maximus d’Archiac, Nummulites perforatus de Montfort, Nummulites postfossulatus Sirel and Deveciler, Nummulites praeaturicus Schaub, Assilina exponens (Sowerby), Sphaerogypsina globulus (Reuss), Asterigerina rotula (Kaufmann), Lockhartia cf. hunti Ovey, Neoratlia sp., Operculina sp., Discocyclina sp., Asterocyclina sp., Lockhartia sp., Lenticulina sp., miliolid-rotaliid forms and echinoderms in the Eruh section. The fossil assemblage described shows that the limestones are of Lutetian-Bartonian and this assemblage indicates a very shallow marine deposition environment. This study provides biostratigraphic and stratigraphic data that help to reassess the Eocene geological evolution of the region. Paleobiogeographically, larger benthic foraminiferal assemblages recorded on carbonate platforms in southeastern Turkey show an affinity to Arabian and Middle Eastern platforms.

New biostratigraphy and microfacies analysis of Eocene Jahrum Formation (Shahrekord region, High Zagros, West Iran). A carbonate platform within the Neo-Tethys oceanic realm

The Eocene Jahrum Formation in High Zagros was studied in Kuh-e- Soukhteh and North Gahrou sections (southwest of Shahrekord region, Chahar-mahal Bakhtiari Province). This formation, composed of limestone, marl, and dolomitic limestone (dolostone), accumulated on a marine platform within the Neo-Tethys ocean realm. It yields a rich foraminiferal fauna, in which three larger benthic foraminiferal assemblage zones were identified. Two assemblage zones in the North Gahrou section were correlated to the Ypresian and Bartonian, and one assemblage zone is represented in the Kuh-e- Soukhteh section and assigned to the Bartonian. In addition, three other groups of benthic foraminiferal associations have been identified based on test wall type (porcellaneous, agglutinate, hyaline) and paleogeographical significance. A discontinuity marked by a hiatus from Cuisian to Lutetian in the North Gahrou section was most probably due to a concealed fault. According to microscopic textures and distribution of benthic foraminifera and other components (peloids, intraclasts, etc.), a gentle depth gradient from the inner ramp to the proximal outer ramp may be reconstructed.

Microbial influence in the Messinian sedimentation: Example of Cap Bon (NE Tunisia)

Messinian sedimentation in Tunisia is characterized by the absence of large carbonate platforms known in many Mediterranean marginal basins. As a result, correlations are not easy to establish in order to integrate it into a general pattern of development at the regional level. However, the discovery of microbial constructions of metric scale makes it possible to precise uncertain points. Thus in the sector of Cap Bon in the northeast of Tunisia, stromatolitic constructions can form, over distances of several hundred meters, domes containing columnar structures at different scales as well as carbonate beds showing sedimentary ripples also of microbialite nature. The highlighting of an assemblage of microbialites, associated with oolitic deposits, allows linking these formations to the Terminal Carbonate Complex which finds its place at a part of the so-called Messinian Salinity Crisis.

Systematic paleontology and biostratigraphy of upper Eocene larger benthic foraminifera from Fanari (Thrace Basin, Greece)

Paleogene sedimentary deposits are exposed in several localities along the extended Thrace Basin in the Greek territory. One of the best sites in terms of preservation, richness and type of sediment occurs along the coastline of Fanari village (SW ofKomotini city). Two outcrops, which consist of upper Eocene shallowmarine clastic sediments, were sampled to analyze the full spectrum of larger benthic foraminifera (LBF) that comprises a rich and diverse assemblage of orthophragmines (Discocyclina, Orbitoclypeus and Asterocyclina), nummulitids (Nummulites, Assilina, Operculina, Heterostegina and Spiroclypeus), and other benthic taxa (e.g., Silvestriella, Pellatispira, Fabiania, Sphaerogypsina, etc.).Adetailed systematic description of LBF from Fanari is presented,which refines the biostratigraphic age of SBZ (Shallow Benthic Zone) 20 corresponding to the late Priabonian for the whole sequence. Twenty-four taxa among which six at (chrono)subspecies level belonging to twelve genera were identified and morphometrically analyzed for the first time from Greece. The LBF assemblage is characterized by the constant presence of Nummulites fabianii almost throughout the whole sequence. The most abundant species are Pellatispira madaraszi and Spiroclypeus carpaticus, though they occur in the upper part of the sequence along with orthophragmines. The foraminiferal distribution in the sequence enables paleoenvironmental observations and the reconstruction of the evolution of the Fanari area. Three main depositional marine shelf facies are distinguished at the shallow upper foreslope of the carbonate platform, making the Fanari section a key area not only of latest Priabonian but also of outer shelf biofacies.

Pithonellid calcitarch record in the middle? Cenomanian Derdere-A Member, SE Turkey: palaeoenvironmental changes and stratigraphic significance

Pithonellid calcitarchs are studied in the organic-rich limestones of the Derdere-A Member from the middle? Cenomanian deposits of SE Turkey for the first time. Little is known about the distribution of pithonellid calcitarchs in the Cretaceous strata of Turkey. Three morphogroups of pithonellid calcitarchs are distinguished: they are represented by Pithonella sphaerica (Kaufmann, 1865) and P. ovalis (Kaufmann, 1865), both dominating the pithonellid assemblages, and by Bonetocardiella conoidea (Bonet, 1956), this latter being less abundant. Compared to the relative abundance of Upper Cretaceous pithonellid calcitarchs in the study area, the diversity is extremely low. The significant increase in abundance of pithonellid calcitarchs is particularly noticeable in the Cenomanian. We observed a significant increase in abundance of pithonellid calcitarchs in the Derdere-A Member, which is associated with an early transgressive phase of the middle? Cenomanian Arabian Platform. They are present in relative abundance and could therefore represent a potentially useful correlative marker horizon in SE Turkey. Pithonellid calcitarchs have been interpreted as indicators of increased nutrient input. A positive correlation exist between pithonellid calcitarchs abundance and nutrition input in the Derdere-A Member which is a sequence of carbonates deposite under eutrophic conditions, as evidenced by the low diversity and very low abundance of benthonic and planktonic foraminifers, and the high abundance of pithonellid calcitarchs. As a result, the increase of pithonellid calcitarchs indicates the increase of nutrient input in the Derdere-A Member. We noticed that a comparable trophic change also occurred throughout the SE Turkey carbonate platform in the middle? Cenomanian. The increase in the pithonellid abundance reported here may be a possible indicator of such a change.

Evolution from Carbonate Platform to Siliciclastic Shelf Driven by Relative Sea–Level Changes: Lower Cretaceous of the Zagros Area, Southwest, Iran

Evolution from Carbonate Platform to Siliciclastic Shelf Driven by Relative Sea–Level Changes: Lower Cretaceous of the Zagros Area, Southwest, Iran

Questioning carbonate facies model definition with reference to the Lower Cretaceous Urgonian platform (SE France Basin)

Designing carbonate facies models requires the integration, correlation and conceptual interpretation of multiple geological data sets. Potential significant errors are sourced from uncertain stratigraphic correlations, speculative palaeoecological interpretations and poorly recorded palaeotopographic profiles. The present study explores a methodological workflow to define a well-supported facies model. An exhaustive literature review is presented on sedimentary facies and depositional profiles of Urgonian carbonate platform from SE France and Switzerland (Barremian–Aptian interval). The historical evolution of Urgonian facies models and related sedimentological concepts is investigated to contextualise published models. The presented conceptual model and table of depositional facies shows a consistent, process-based organization of specific elementary facies, facies associations and carbonate system. Within the chronostratigraphic framework, the study of synchronous strata correlations provides quantitative analyses of facies-belt extents and palaeobathymetric estimations. The resulting depositional profile is based on general palaeoecological and sedimentological concepts, facies distribution on palaeogeographic maps and stacking trends. In rare locations in the field, direct lateral facies belt transitions are recorded. Proximal (i.e. emersive and peloidal-foraminiferal) depositional facies are rarely observed; most outcrops record the (i) rudist facies association, which corresponds to distal parts of the inner platform, (ii) coral, ooidal and bioclastic facies associations, which are interpreted to occur on the outer platform, and (iii) calcisiltite, slope and basinal deposits. Key data and concepts allow for the building up of a robust, harmonised facies model that can be used to properly interpret palaeoenvironmental changes, stacking trends and stratigraphic sequence evolution, the resolution of which depends on the available chronostratigraphic framework.

From shallow-water carbonate ramp to hemipelagic deep-marine carbonate deposition: Part 3. Lithostratigraphy and Formations of the Middle to Late Anisian Bulog sedimentary successions (Bulog Group) in the Dinarides (Bosnia and Herzegovina, Serbia, Montenegro)

In the Middle Anisian the opening of the Neo?Tethys started and this is characterized by a significant change in deposition in the whole Western Tethys Realm. In the Dinarides the Middle to Late Anisian tectonostratigraphic and basin evolution is mirrored by their sedimentary successions. In the Middle Anisian, the evolution of the shallow?water Ravni Carbonate Ramp ended relatively abrupt in the late Pelsonian: a rapid decrease of carbonate production is accompanied by formation of a horst?and?graben topography. This change is expressed by the change in deposition from shallow?water carbonates to deepwater sedimentary rocks, i.e. the Ravni Carbonate Ramp experienced a drowning. Contemporaneously neptunian dikes were formed in the underlying Ravni Formation, filled with deep?water limestones. In the grabens, near to the newly formed escarpments mass transport deposits accumulated. During the time span late Pelsonian to middle Illyrian a general deepening trend is mirrored in the sedimentological trend and the microfacies characteristics. Fossilla ? gerst?tten (mainly cephalopods) and hardgrounds occur widespread in the deeper?water red nodular limestones formed widespread above the Ravni Carbonate Ramp. Around the middle/late Illyrian boundary a second intense pulse of tectonic motions, related to the onset of volcanic activity, resulted in a crosscut of the older horst?and?graben topo graphy. A second generation of neptunian dikes was formed, the blocks tilted, and again mass transport deposits accumulated near to escarpments. The late Illyrian is characterized by an overall deepening trend expressed also in a change in the microfacies characteristics to radiolarian?rich wacke? to packstones. In cases even radio larites or silicified limestones are characteristic sedimentary rocks in late Illyrian to Ladinian times beside silicified volcano?sedimentary rocks. This paper will define the late Middle?Late Anisian red nodular limestones and related sedimentary rocks with mass transport deposits overlying the Ravni Carbonate Ramp on base of new sedimen tological, stratigraphic and micro facies data following the international rules and standards. The palaeo geographic position together with characteristic litho? and microfacies features cause the lithostratigraphic definition of the different units. Included in the newly introduced Bulog Group are: 1) the emended and formalized Bulog Formation and 2) the newly introduced and defined Komarani Formation. The type?section of the Bulog Formation east of Sarajevo (Han Vidovic, central Bosnia and Herzegovina) is revisited. The Komarani Formation is introduced with the type?section in Komarani village (Zlatar Mt. in SW Serbia). The reference sections for the Bulog Formation in SW Serbia (Klisura quarry on Zlatibor Mt.), Bosnia and Herzegovina (Pridvorica locality at Romanija Mt.) and in Montenegro (Boljevici near Virpazar), are defined. In the reference sections some characteristic lithological and microfacies features are better preserved as in the type?section and included in the emendation and formalization of the Bulog Formation. The Bulog Formation at the type?section and all reference sections are in the Late Triassic overlain by the shallow?water carbonates of the Wetterstein and Dachstein Carbonate Platforms. Age and facies equivalent red nodular limestones deposited in the outer shelf region are part of the Middle to Late Triassic Hallstatt Limestone succession. In the type?region of the Hallstatt Limestones these late Middle to Late Anisian red nodular limestones are named Schreyeralm Limestones. The name Schreyeralm Limestone was introduced earlier as the name Bulog Limestone. It is discussed if also in the Dinarides the name Schreyeralm Limestone should be used for such Anisian red nodular limestones deposited in the outer shelf region, for priority reasons, or if they should be included into the Bulog Formation to avoid confusion, for historical reasons.

Middle Triassic calcareous algae and microproblematica from south China

The Yangtze carbonate platform (Southern China) recorded a long sedimentary evolution from Neoproterozoic to the basal Upper Triassic. During the Early and Middle Triassic, this platform was dominated by shallow-water carbonates. In various sectors of the platform, the Middle Triassic (Anisian-Ladinian) succession contain abundant assemblages of benthic foraminifera and calcareous algae. Following a previous paper about the Middle Triassic dasycladalean algae from SW Guizhou Province, the present study describes algae and microproblematic organisms from three sections: Honyan, Longtou and Guanling. Some dasycladalean algae are well known from the Alpine-Dinaric domain: Diplopora annulatissima, D. annulata, Euteutloporella triasina, Macroporella dinarica, Oligoporella minutula, O. pilosa pilosa, Poncetella hexaster and Pseudodiplopora proba. However, the dasycladalean association is dominated by species belonging to the genus Kantia, including K. cf. dolomitica and K. cf. comelicana. New Kantia species (K. intusannulata n. sp., K. granieri n. sp., K. muxinanii n. sp.) are characterized by the presence of intusannulation, a feature unknown from the Kantia species in the Alpine domain. The dasycladalean association also contains new species of the genus Mizzia and specimens belonging to the organo-genus Acicularia and/or Terquemella. Besides, rare specimens of "Solenopora" and Rivularia-type cyanobacteria are also present. The algal association is accompanied by microproblematic organisms including Tubiphytes sp., Zorniella obscura, Plexoramea cerebriformis, Ladinella porata, and Baccanella floriformis. Anisian-Ladinian foraminifera complete the micropaleontological spectrum of the sections studied. The most important are Meandrospira dinarica, Endotriadella wirzi, Paleolituonella meridionalis, and Turriglomina mesotriasica. The microfossils from the Middle Triassic Yangtze carbonate platform of south China belong to the Eastern Tethys province. Some of these species are also present in the Western Tethys (Alpine Domain). The new species presented in this study are absent from the Alpine Domain and probably represent endemic species for the Eastern Tethys.

Provenance of the Middle Miocene Barreiras Fan Delta in the Onshore Pará-Maranhão Basin, Northern Brazil

The demise of the carbonate platform in the Brazilian Equatorial Margin has been related to the progradation of massive siliciclastic inflow from the Cratonic Amazon River during the middle Miocene. The sediment plume did not influence the eastern portion of this drainage, including the Bragantina Platform andthe Marajó Basin, the onshore Pará-Maranhão Basin. The provenance signatures of these tectonic segments have been demonstrated in siliciclastic coastal deposits of the Barreiras Formation, whose progradation caused the suppression of the Oligocene-Miocene carbonate platform. Our provenance study is based on clast morphology, quartz cathodoluminescence, and heavy minerals of mainly Barreiras alluvial-fluvial deposits, using new and published facies data. This study opens a window of opportunity to investigate, for the first time, the proximal facies combined with paleocurrents exposed only in this area of Brazil. The restricted occurrence of proximal facies indicates an exceptional potential for preservation related to subsiding regions generated by reactivated faults in the Gurupi Belt. Provenance data indicate the strong influence of metamorphic source rocks with minor volcanic and plutonic contributions from the southeastern and southern of the Bragantina Platform and eastern Marajo Basin. Respectively, two heavy minerals assemblages were found: 1) staurolite, metamorphic quartz, and angular clasts; and 2) abundant zircon, kyanite, tourmaline, mixed quartz (metamorphic, plutonic, and volcanic), and rounded clasts. The assemblages are associated with São Luís Craton, mainly crystalline rocks from Gurupi Belt. In addition, the proximal facies of the Bragantina Platform provide rich staurolite concentration and angular clasts indicating near source area; the uplifted Marajó Basin during the middle Miocene contributed with reworked sediments containing rounded clasts and ultrastable minerals related to Silurian-Cretaceous rocks. This work complements the previous paleoenvironmental reconstruction for the Barreiras deposits, including the most robust proximal facies interpretation contributing to understanding sediment dispersion during the middle Miocene, reinforcing previously defined source areas.

U-Pb detrital zircon ages and Hf isotope from Sardinia and Adria Cretaceous bauxite (Italy): Constraints on the Alpine Tethys paleogeography and tectonic evolution

Bauxite deposits in Italy mainly distribute in Sardinia and Adria regions within Cretaceous carbonate sequences. Parental affinity of Italian bauxite deposits has long been a controversial problem. At least four potential sources have been proposed: (1) Cretaceous debris and autochthonous marlstones; (2) alluvial sheets from the weathered Variscan basement; (3) weathering materials from North Africa and (4) Cretaceous bimodal volcanism in the Dinaric and Carpatho-Balkan orogenic belts. In this study, a total of 374 detrital zircon U-Pb ages and 86 Hf isotope values have been acquired from Cretaceous bauxites of Sardinia and Adria regions. Combining with the published geochemical data, provenances of Cretaceous bauxite deposits in Sardinia and Adria regions have been discussed. In bauxite deposits of Sardinia, dominant Early Paleozoic aged zircon grains (main age peaks at 291 – 295 Ma, 454 – 465 Ma, and 582 – 639 Ma) and their various Hf isotope compositions (εHf(t) = +9.61 to −5.66) indicate a parental affinity of Variscan metasedimentary basement. As a contrast, bauxite deposits in Adria show abundant Jurassic – Cretaceous (93 – 178 Ma) zircon grains with negative εHf(t) values (-13.75 to −4.61), demonstrating significant supply from coeval volcanic materials. Cretaceous bauxite samples from Sardinia and Adria shed light on paleogeographic restoration and tectonic evolution of Alpine Tethys. Began in Early Cretaceous, Sardinia was affected by uplift due to the subduction between Ligurian oceanic crust and the Iberia plate. The Mesozoic carbonate sequence were eroded and the underlying Variscan basement was exposed in the area from Sardinia to the Massif Meridional, provided weathering materials for bauxitization. Late Cretaceous witnessed the further NNE-trending subduction of the Adria Plate to the West Vardar oceanic plate, where calcalkaline igneous rocks and volcanic ashes from Dinarides supplied windborne weathering materials to carbonate platforms in Adria. Particularly, provenance difference between the bauxite of central-southern Apennine and Sardinian reveals that the hosting carbonate sequence in Apennine was not located on the Sardinia shelf before the Cenozoic tectonism in the south Mediterranean realm. Diversity of provenances in bauxite deposits from Sardinia and Adria may cause differences in geochemical composition and further influence qualities of bauxite ore in two regions.

New Stratigraphical and Sedimentological Data on the Lower Cretaceous Rocks in Section Kalotina, Western Bulgaria

Biostratigraphic, microfacies and C–O isotope data from the lowermost Cretaceous deposits in section Kalotina reveal the development of a shallow carbonate platform (Slivnitsa Formation) in a photozoan mode under moderate to high-energy conditions during the Berriasian. Around the Berriasian/Valanginian boundary the carbonate production switched to a heterozoan-type suggesting a biological crisis. After a subaerial exposure in the earliest Valanginian and subsequent karst formation the platform was drowned during the latest Valanginian. Deposition of carbonate-argillaceous sediments (Salash Formation) occurred in a deeper, open-marine environment under mesotrophic to eutrophic, low-energy conditions with periodical formation of crinoid-rich packstones probably by mass gravity flows. Limestone samples from the Slivnitsa Formation yield higher δ13C values compared to coeval open-marine deposits which can be explained by an elevated amount of aragonite in the photozoan carbonate production and an enrichment in δ13C of the shallow platform waters due to high levels of photosynthesis. The most depleted δ13C value in the uppermost part of the unit most likely reflects a change from oligotrophic to mesotrophic conditions. The C-isotope signatures in limestones of the Salash Formation indicate correspondence to the third, smooth decrease phase in the δ13C record of the global Weissert Event (latest Valanginian and Early Hauterivian) where values tend to recover to pre-excursion values.

A glimpse of the lost Upper Triassic to Middle Jurassic architecture of the Dinaric Carbonate Platform margin and slope

In the southernmost outcrops of the Slovenian Basin the Middle Jurassic coarse-grained limestone breccia (mega)beds are interstratified within a succession that is otherwise dominated by hemipelagites and distal turbidites. In this paper, these beds are described as the Ponikve Breccia Member of the Tolmin Formation. We provide descriptions of the studied sections with detailed geological maps and analysis of the breccia lithoclasts. From the latter, a non-outcropping margin of the Dinaric Carbonate Platform is reconstructed. In the Late Triassic the platform margin was characterized by a Dachstein-type marginal reef. After the end-Triassic extinction event, the platform architecture remained, but the reefs were replaced by sand shoals characterized by ooids. In the late Early Jurassic and/or early Middle Jurassic a slope area might have been dissected by normal faults and a step-like paleotopography was formed. In the Bajocian, during a period of major regional geodynamic perturbations, extensional or transtensional tectonic activity intensified and triggered the large-scale collapses of the Dinaric Carbonate Platform margin producing the limestone breccias described herein. This may in turn have caused a backstepping of the platform margin, as is evident from the occurrence of Late Jurassic marginal reefs that are installed directly above the Upper Triassic and Lower Jurassic inner platform successions.

In situ modulation of Pt-Ni heterocatalysts on highly graphitized wood-derived carbon platform to boost hydrogen production

Although Pt is an ideal electrocatalyst for hydrogen evolution reaction (HER), in addition to high cost and scarcity, Pt nanocatalysts suffer from low water dissociation rates and poor stability. Herein, we used graphitized wood-derived carbon (GWC) as a platform to construct dual-active catalytic sites via Pt-Ni recombination and modulate interactions of heterointerface atoms through in situ phase transition to improve HER activity and durability of Pt nanocatalysts. Specifically, Ni(OH)2 nanosheets were grown on GWC; then, Pt nanoparticles were introduced and converted in situ into Pt-Ni(PO3)2-GWC. As expected, the catalyst exhibited excellent HER activity, requiring only 10 mV (overpotential) to reach a current density of 10 mA cm–2 and excellent durability over 120 h. DFT calculations further revealed that in situ converted Pt and Ni(PO3)2 heterointerface tuned the electronic structure of interface atoms and synergistically promoted water dissociation and hydrogen adsorption. Notably, Pt-Ni(PO3)2-GWC can be used as a bifunctional catalyst for overall urea electrolysis, and the assembled electrolytic cell exhibited high-efficiency hydrogen production performance, requiring a cell voltage of only 1.39 V to reach a current density of 10 mA cm–2. These findings will provide new insights into the development of highly efficient, stable catalysts for energy-saving hydrogen production.

Carbonate platform architecture and carbon isotope stratigraphy from the neoproterozoic Narji limestone formation, Kurnool Group, India: Decoding clues of relative sea level fluctuations

From a detail process-based facies and facies association analysis in a spatio-temporal framework, a rimmed shelf platform geometry is proposed for the Neoproterozoic Narji Limestone Formation, Kurnool Group, India. Ten carbonate facies types were delineated and clubbed under seven facies associations belonging to four different paleogeographic settings viz. Forereef (intertidal to shallow subtidal and shallow to deep subtidal), peritidal reef and back-reef lagoon. Whereas crinkly microbial laminites with subordinate domal stromatolites constitute the reef part, the fore slope deposition in the platform largely remained tide-and storm-dominated. Grey to black colored pyrite bearing bedded limestone-shale alternation without any current or wave imprint represents the back-reef lagoon deposition. A high carbonate saturation and productivity in the Narji inner and mid shelf is suggested from an overall dominance of microalgal laminite and microdigitate stromatolites over columnar stromatolites. From documentation of decimeter-to meter-thick shallowing-upward depositional hemicycles, embedded within an overall aggradational Narji lithosuccession, a combined control of sea level and carbonate productivity is inferred in course of Narji sedimentation. A short-duration medium-to large-scale rise in the base level led to the aggradation in shallow water rim of the Narji platform margin; interruption of this overall motif by short thickening- and shallowing-upward progradational hemicycles bear testimony for higher productivity in the Narji mid-to inner shelf areas. The present study intends to correlate shallowing-upward hemicycles with keep-up to catch-up depositional cycles with signature of apparent sea level fall. The control of relative base level variation in Narji depositional history is strengthened with multiple signatures including secular δ13C composition, total organic carbon (TOC) content and siliciclastic content documented from the entire Narji litho-succession.

Depositional environment of the Middle Triassic Strelovec Formation on Mt. Raduha, Kamnik-Savinja Alps, northern Slovenia

The Raduha section represents a continuation of the research of the Anisian Strelovec Formation in the Kamnik-Savinja Alps. The Strelovec Formation was deposited during the Anisian on a drowned section of the Serla Dolomite carbonate platform in a restricted probably outer ramp environment associated with an intraplatform basin. The base of the section is represented by dolostone breccia containing angular carbonate lithoclasts of shallow-marine origin. This is followed by alternations of laminated and homogenous hemipelagic limestones deposited in a restricted and anoxic environment. Hemipelagic sedimentation was occasionally interrupted by clay input and deposition of sediments from gravity mass flows. Slow filling of the basin lead to a gradual cessation of anoxic conditions and sedimentation of bedded shallow-marine limestones. After shallow water conditions were established, bioclastic dolostone of the Contrin Formation was deposited.