Northern Calcareous Alps Research Articles

Dynamic landscape response to Younger Dryas and earliest Holocene cooling events in the European Eastern Alps (Austria)

In classic loess areas research into dust deposition and concomitant environmental changes has a long history and numerous well-investigated loess-palaeosol sequences provide insights into Late Quaternary landscape responses to climatic change on orbital to centennial time scales. This contrasts with mountain regions, where an understanding of dust deposition under rapidly changing climatic and environmental conditions is much less developed. Here we describe two sediment records from the Austrian Alps that provide rare evidence for intramontane loess accumulation. Dust deposition has been numerically constrained to the Younger Dryas (YD) to earliest Holocene interval, making these sites the first proof of significant intramontane aeolian activity during this time interval in the Eastern Alps.At study site 1, located in the Northern Calcareous Alps, a loess layer 10–20 cm in thickness and laterally exposed over more than 300 m is sandwiched into an alluvial-fan succession. Two optically-stimulated luminescence ages of quartz and four radiocarbon ages of charcoals indicate loess accumulation during the Younger Dryas to earliest Holocene. This laterally extensive loess drape suggests much drier climatic conditions compared to today, which is corroborated by palynological investigations. Macro- and micro-charcoal particles within the loess indicate regional wildfires that might have exaggerated climatically induced sedimentary processes. The second site is a Mesolithic site located ∼30 km southeast of site 1. At site two, redeposited till and pebbly scree are sharply overlain by a few centimetre thick light-grey loess layer, which is capped by the archaeological living floor hosting 14C dated fireplaces suggesting human presence as early as 10.9 ± 0.2 cal ka BP. These radiocarbon ages in combination with single-grain IRSL dating of feldspar at site two suggests concomitant aeolian deposition at site 1 and 2.Recently, a widespread drape of loess deposited immediately subsequent to the LGM was described for the same sector of the Eastern Alps (Gild et al., 2018). The present study expands on these findings and provides evidence for the recurrence of loess deposition also during the YD to earliest Holocene, and suggests a highly sensitive response of the geomorphic system in mountain ranges to abrupt post-LGM climate fluctuations. We conclude that, in addition to moraine records of Alpine glaciers and speleothems that accurately chronicle Late Glacial temperature fluctuations, the spatio-temporal pattern of inner-Alpine loess deposits records the mode and sensitivity of landscape responses to such cooling events. Because such aeolian sediment layers can be redeposited or pedologically overprinted, they are often overlooked, and are thus still severely under-researched.

Determination of a normal orogenic palaeo-geothermal gradient with clay mineral and organic matter indices: a review

A collection of large data sets from different orogenic belts was compiled for a correlation between organic matter (OM) versus clay mineral (CM) indices calibrated with the vitrinite reflectance, (VR) vs Kübler-Indices (KI) method. Data selection was based on a normal geothermal gradient (25 to 35 °C/km) as determined in previous studies, e.g. by maturity modelling and clay mineral reaction progress calculations. In the Lower Austroalpine (Eastern Switzerland, European Alps) a 20 myr lasting metamorphic overprint caused an OM–CM thermal equilibrium among the indices used. The observed correlation enables to determine gradual changes in metamorphic factors such as pressure, temperature and time causing sensitive shifts of the gradient slope in the range of normal gradients. For New Caledonia, an identical correlation has been determined. Prior to re-equilibration of the VR/KI indices, sediments in New Caledonia of diagenetic to incipient metamorphic grade underwent a high-pressure subduction event. VR/KI indices are in or close to equilibrium, while slight differences in OM vs CM indices allow for a better understanding of polyphase conditions, especially with respect to pressure. Temperature estimations are identical despite of their poly-phase metamorphic history, which was mainly controlled by the last orogenic thermal event lasting > 5 to < 10 myr. In the eastern Helvetic Alps and Northern Calcareous Alps similar correlations were found with slightly different slopes. Comparison between different regions is possible when using KI standardization and same data discrimination. In both parts of the Alps a complex thermal history of short durations (< 5.0 myr for the Northern Calcareous Alps to 10 myr for the Helvetic Alps) caused similar VR/KI trends, but disequilibrium is suggested by weaker regression parameters. The following correlation is calculated for a moderate geotherm (55 to 74 mWm2, mean = 61 mWm2) and normal temperature gradient conditions (25 to 35 °Ckm−1): KI = 1.134e−0.305VR, (R2 = 0.880, n = 462) with VR given as %Rmax, KI as Δ°2θ (limited to values between 0.2 to 1.0 Δ°2θ). With increasing depth (z) a VR gradient of 1.4 ± 0.2%Rmaxkm−1 is determined and a KI gradient of 0.09 ± 0.002 Δ°2θ km−1 is observed. The study illustrates that a normal geotherm can be described by VR/KI correlation, even if different heating episodes may occur. For the detection of a poly-phase or plurifacial thermal history, several indices of clay minerals and organic matter with very different kinetics should be used, as e.g. demonstrated by strong differences in smectite content at equal VR/KI values versus structural depth. A specific interest is given to the correlation of vitrinite like solid bitumen reflectance as an alternative method to VR, the persistent preservation of liptinite macerals and the stability range of clay minerals and sub-greenschist facies critical minerals compared with VR/KI data. Until now, despite the Alps in this study, systematic liptinite maceral studies have not been published in other orogenic settings.

Radiolarian response to environmental changes at the Sinemurian–Pliensbachian transition in the Northern Calcareous Alps, Austria

AbstractMajor environmental, climate and sealevel changes occurred in the Western Tethyan Realm during the late Sinemurian to early Pliensbachian time interval. Here, we examine how these changes affected the taxonomic composition of radiolarian fauna. Radiolarian assemblages were collected on Mount Rettenstein (Northern Calcareous Alps) from a siliceous limestone and marl succession, deposited in a well‐oxygenated basin a few hundred metres in depth on the continental shelf at the western edge of the Neotethys Ocean. Radiolarian research was complemented with elemental and isotope geochemistry on bulk carbonate samples. The siliceous microfaunas below and above the stage boundary consist of more than 80% sponge spicules and less than 20% radiolarians, with a strong predominance of the Order Spumellaria. The Nassellaria to Spumellaria abundance ratio ranges from 1:5 to 1:3. At the Sinemurian–Pliensbachian transition, a significant drop in diversity occurred, accompanied by a substantial change in relative abundances of radiolarian taxa. The most severely affected groups were surface‐dwelling radiolarians (Angulobrachiidae, Hagiastridae, Pantanelliidae; mostly Gorgansium, Poulpidae and Ultranaporidae), which almost or completely disappeared. In contrast, Archaeocenosphaera, Praeconocaryomma, Zhamoidellum and Lantus became abundant and were apparently the most resistant to environmental stress. The changes in radiolarian assemblages were local and probably induced by the end‐Sinemurian sealevel drop that transformed the area into a semi‐enclosed basin with restricted ocean circulation. The exchange of water masses and thus radiolarian faunas with the open sea was reduced and their productivity may have been lowered by the lower inflow of fertile waters from the ocean.

Patterns of extinction and recovery across the Triassic–Jurassic boundary interval in three resilient Southern Tethyan carbonate platforms

During the end-Triassic extinction (ETE), carbonate platform biocalcifiers suffered high extinction rates that have been linked to volcanically-induced global changes in climate and carbon cycle. Most studies have been focused on the classical sections of the Northern Calcareous Alps (NCA, Austria) and Lombardy Basin (Italy), where the extinction of the aragonitic Dachstein-type biota (involutinid foraminifera and megalodontid bivalves) coincides with the demise of the carbonate platform and with the initial negative carbon isotope excursion (CIE) of the reference sections for the Triassic/Jurassic Boundary (TJB).In this study, we present a detailed facies analysis, bio- and carbon-isotope stratigraphy of three Southern Tethyan carbonate platform sections, Mt. Messapion (Greece), Valle Agricola and Mt. Sparagio (southern Italy) that instead show persisting carbonate productivity across the TJB and potentially preserve the most detailed record of timing and patterns of the ETE in these ecosystems.In the studied sections, the disappearance of the Dachstein-type biota is observed within a positive δ13Ccarb excursion that, according to our study, correlates with that documented in the Schattwald beds (NCA) and Malanotte Fm (Lombardy Basin) above the initial CIE. This level represents the true extinction of the Dachstein-type biota, while the disappearance in the Northern Tethyan sections of the NCA and Lombardy Basin represents a pseudoextinction coinciding with the carbonate platform demise. Above the ETE, Southern Tethyan carbonate platform sections are characterized either by microbial laminites or ooid and oncoid limestones and low-diversity associations.This study reveals a possible paleogeographic and/or latitudinal control on the response of biocalcifiers and carbonate platform ecosystems during the ETE. The Dachstein-type biota was resilient to the environmental perturbations associated with the initial CIE in Southern Tethys, but probably failed to survive subsequent and/or prolonged stress. Despite extinctions, Southern Tethyan carbonate platforms adapted to environmental disturbances through a shift of the dominant carbonate production style from aragonitic biocalcification to chemical and microbially-mediated CaCO3 precipitation. The ecosystem recovery was slow and aragonitic biocalcifiers (dasycladacean algae) reappeared during the early Sinemurian.

Morphology, taxonomy and trophic interactions of rostrum-less coleoids from the Late Triassic Polzberg Konservat-Lagerstätte (Lower Austria)

AbstractColeoid cephalopods are widespread from the Mesozoic till today. The extinct group of the Phragmoteuthida is thought to represent either stem-neocoleoids, stem-decabrachians, or stem-octobrachians. The well-known, almost complete specimens of Phragmoteuthis bisinuata from the Carnian Polzberg Konservat-Lagerstätte near Lunz am See (Lower Austria, Northern Calcareous Alps) and Cave del Predil (Northern Italy, Julian Alps) come from historical collections. These specimens do not reflect the entire coleoid assemblage within this environment. In order to obtain a more complete picture of the Carnian coleoid fauna, 430 coleoid specimens from the Polzberg locality and 60 specimens from contemporaneous localities around Cave del Predil were studied in detail. All available elements (phragmocones, proostraca, cartilages, hooks, beaks, ink sacs) attributed to the coleoid fauna were recorded, measured and evaluated taxonomically and taphonomically. Reviews of historical collection material permitted comparisons with recently collected material. The notation of co-occurrences of other faunal elements yielded insights into the palaeoecological context of this Upper Triassic environment within the Polzberg Basin. The new material from Polzberg does not support the previous assumption of a monospecific composition of the Polzberg coleoid fauna. Instead, we report the occurrence of the new phragmoteuthid Phragmoteuthis polzbergensis nov. sp. and a newly excavated specimen of Phragmoteuthis indicates the presence of ten arms within the group of the Phragmoteuthida for the first time. Phragmocones with small opening angles combined with cylindrical (roundly closed) body chambers, and arm hook types which are unusual for phragmoteuthids indicate the presence of the basal coleoid group comprising the rostrum-less genus Mojsisovicsteuthis.ZooBank LSID: urn:lsid:zoobank.org:pub:7EE7425C-6B0C-4800-925A-52D9108C13C7.

Multi-proxy record of the Austrian Upper Triassic Polzberg Konservat-Lagerstätte in light of the Carnian Pluvial Episode

We present a multi-proxy investigation of a lower Carnian basinal succession from Polzberg in the Northern Calcareous Alps (Lower Austria). A section comprising a unique Konservat-Lagerstätte was studied based on bio- and chemostratigraphy along with geophysical methods, yielding a detailed and robust stratigraphic calibration of the Polzberg succession. The Polzberg section revealed the paleoceanographic history and helped to identify a global climatic reversal, the Carnian Pluvial Episode. The age of the Upper Triassic Reingraben formation in the Northern Calcareous Alps is refined as the Austrotrachyceras austriacum Zone within the lower Carnian (Julian 2). Ammonoids and conodonts provide a detailed biostratigraphic subdivision that serves as a basis for analyses of the faunal distribution and the paleoenvironmental evolution of the Upper Triassic Reifling Basin. The succession includes lithological and facies changes similar to those of coeval units in the Tethys. The Carnian was characterized by a weak (~ 1‰) positive δ13C trend, punctuated by a negative shift during the lower Carnian corresponding to the initiation of the Carnian Pluvial Episode, a period representing the onset of early/late Carnian transitional global greenhouse conditions. Organic maturity parameters and the conodont alteration index (CAI) show that the thermal overprint of the Polzberg section is low. Biomarker proxies suggest that the organic matter of the uppermost Göstling formation is a mixture of marine and terrestrial material deposited in a dysoxic environment. Within the overlaying Reingraben formation, the amount of marine biomass decreased gradually upwards. Oxygen-depleted conditions, probably due to water-column stratification, continued during deposition of the Reingraben formation. Bacterial sulfate reduction played a major role in organic matter degradation.

Fold localization at pre-existing normal faults: field observations and analogue modelling of the Achental structure, Northern Calcareous Alps, Austria

Abstract. Within the Northern Calcareous Alps (NCA) fold-and-thrust belt of the Eastern Alps, multiple pre-shortening deformation phases have contributed to the structural grain that controlled localization of deformation at later stages. In particular, Jurassic rifting and opening of the Alpine Tethys led to the formation of extensional basins at the northern margin of the Apulian plate. Subsequent Cretaceous shortening within the Northern Calcareous Alps produced the enigmatic Achental structure, which forms a sigmoidal transition zone between two E–W-striking major synclines. One of the major complexities of the Achental structure is that all structural elements are oblique to the Cretaceous direction of shortening. Its sigmoidal form was, therefore, proposed to be a result of forced folding at the boundaries of the Jurassic Achental basin. This study analyses the structural evolution of the Achental structure through integrating field observations with crustal-scale physical analogue modelling to elucidate the influence of pre-existing crustal heterogeneities on oblique basin inversion. From brittle–ductile models that include a weak basal décollement, we infer that oblique shortening of pre-existing extensional faults can lead to the localization of deformation at the pre-existing structure and predicts thrust and fold structures that are consistent with field observations. Consequently, the Achental low-angle thrust and sigmoidal fold train was able to localize at the former Jurassic basin margin, with a vergence opposite to the controlling normal fault, creating the characteristic sigmoidal morphology during a single phase of NW-directed shortening.

Salt-rich versus salt-poor structural scenarios in the central Northern Calcareous Alps: implications for the Hallstatt facies and early Alpine tectonic evolution (Eastern Alps, Austria)

One of the most remarkable features of the central Northern Calcareous Alps (Eastern Alps, Austria) is the widespread presence of Upper Triassic deep-water carbonates (the Hallstatt facies) and Permo-Triassic evaporites resting on deep-water Middle Jurassic strata and their underlying Upper Triassic shallow-water carbonate platform successions. The Hallstatt facies and accompanying evaporites have been classically interpreted to originate either from a location south of the time-equivalent carbonate platforms, or to have been deposited in deeper water seaways within the broad platform domain. To date, this dispute has been addressed mostly through the analysis of Triassic and Jurassic facies distribution in map view, which, however, is subject to some degree of ambiguity and subjectivity. In this contribution we present, for the first time, sequentially restored regional cross-sections through the central Northern Calcareous Alps to understand the implications of the contrasting paleogeographic models. We present (a) an interpretation based on a highly allochthonous origin of the Triassic deep-water units and (b) an interpretation based on their relative autochthony in which we incorporate the potential influence of salt tectonics in the central NCA. The restored cross-sections provide a framework within which the alternative scenarios and their paleogeographic implications can be better understood. Through this analysis we propose that salt tectonics in the central NCA can provide a valid explanation for apparent inconsistencies in the relative autochthony scenario and thus constitutes a reasonable alternative to the currently accepted allochthony scenario.Graphical abstract

Upper Jurassic–lowermost Cretaceous hybrid build-ups of the Western Tethys Realm: Cement-rich microencruster-microbialite-calcified sponge framework

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.

Cave Levels in the Totes Gebirge (Eastern Alps)

Abstract The Totes Gebirge is not only the largest karst massif in the Northern Calcareous Alps, it also contains the most cave passages. In this area we are investigating the vertical distribution of phreatic cave passages to determine cave levels. These are vertical zones with clusters of cave passages that can be correlated with former valley floors. Since only phreatic cave passages (i.e. caves that were permanently or episodically filled with water during their formation) are to be analysed, a genetic classification is made on the basis of field observations, cave maps, 3D surveys and descriptions. As of Sept. 2023, the Totes Gebirge range, including the adjacent Warscheneck and the Hohe Schrott, contains 3172 known caves with a total length of 821 km, including the two longest cave systems in Austria, the Schönberg- (156 km) and the Schwarzmooskogel-Höhlensystem (137 km). As small caves do not contribute significantly to these statistics, only caves ≥50 m were included. The remaining 754 caves have a total length of 790 km. Only 46 % of these caves are at least partially of phreatic origin, but they contain 92 % of the total passage length. After subtracting the caves from which no data were available and cave sections that are not phreatic in origin (i.e. vadose or those created by weathering and erosion), 641 km of cave sections remained, which were analysed for their vertical distribution in 25 m increments. The histogram of cave length distribution vs. elevation for the Totes Gebirge range shows only a single significant cluster of phreatic cave sections between 1300 and 1850 m above see level (a.s.l.), with a clear maximum at 1500 m. The massif was divided into four sub-regions and all of them show this main interval, which is why it was interpreted as a cave level. It correlates well with the Giant Cave Level known from all other karst massifs in the Northern Calcareous Alps analysed so far. However, it is peculiar that in the other massifs at least three cave levels are present. Other reasons, such as the lack of known caves and the large size of the massif, which could lead to overlapping of cave levels, are unlikely. Therefore, it seems possible that the palaeo surface drainage pattern around the Totes Gebirge or its uplift history was different from the other karst massifs in the Northern Calcareous Alps and that low-lying cave levels (Spring and Berger Cave Level) or an elevated one (Ruin Cave Level) did not develop. For each of the 21 largest cave systems (≥5 km in length), the peak of the vertical distribution of the phreatic passages was determined. Vectors were calculated in order to test whether palaeo-flow directions could be inferred from their distribution. These phreatic maxima indicate a general dip from ESE to WNW, which could be interpreted either as a palaeo-drainage direction or as a tectonic tilting of the whole massif after the formation of the passages.

The type-section of the Gutenstein Formation at Gutenstein revisited (Anisian, Northern Calcareous Alps, Lower Austria): Lithostratigraphy, biostratigraphy and regional overview

Abstract New biostratigraphic data derived from the stratotype of the Gutenstein Formation at the village Gutenstein (Lower Austria) help to solve some long-standing problems about the stratigraphy of the Anisian stage within the eastern part of the Northern Calcareous Alps. At Gutenstein, the lower lithostratigraphic boundary of the Anisian Gutenstein Formation to the underlying lower Anisian Reichenhall Formation is defined, assuming a normal stratigraphic contact of the Reichenhall Formation to the underlying Werfen Formation and to the overlying Gutenstein Formation. Microfacial data confirm the sedimentary origin of the rauwackes of the Reichenhall Formation. A detailed lithostratigraphic and facies-oriented definition of the Gutenstein Formation includes prevailing thin and planar-bedded, black colored, sometimes fine-bedded limestone (rarely dolostone) and radiolarian (calcispheres) bearing, black colored mud- to wackestone, mostly containing some fine crinoid debris. Upsection, a quick change to an upper (Pelsonian) member of the Gutenstein Formation with nodular bedding planes and brachiopod-, crinoid-, conodont- and ammonite accumulations is presented. The general depositional environment of the Gutenstein Formation is interpreted as a dysoxic outer carbonate ramp deposit, with a shallowing upward trend to rather thick-bedded mid- and inner carbonate ramp settings of the Annaberg- and Steinalm formations. The approximate interval of the Anisian/Ladinian boundary within the type-section of Gutenstein is determined with help of new fossil findings such as dasycladalean green-algae. Based on distinct lithological differences on a regional scale, which occur in thick basinal stratigraphic successions within the Gutenstein Formation like at Großreifling (Styria, Bajuvaric Nappe System), at Innerfahrafeld (elevation Fuchsriegel, Lower Austria) and on mount Kasberg at Grünau (Upper Austria, Tirolic Nappe System), a subdivision of the Gutenstein Formation into a lower Gutenstein Member, and an upper Kasberg Member (= Upper Gutenstein Formation), is proposed herein. The lower member corresponds to the black, thin- and planar-bedded interval, whereas the Kasberg Member is characterized by nodular bedding planes, greater bed thicknesses and higher fossil content.

Calcareous nannofossils at the Cretaceous/Paleogene boundary of the Northern Calcareous Alps (Wasserfallgraben section, Germany; Nussdorf section, Austria).

Calcareous nannofossils at the Cretaceous/Paleogene boundary of the Northern Calcareous Alps (Wasserfallgraben section, Germany; Nussdorf section, Austria).

Middle Cenomanian coral fauna from the Roßsteinalmen (Northern Calcareous Alps, Bavaria, Southern Germany) – a revised and extended version

In the Northern Calcareous Alps, relics of a formerly widely distributed shallow marine facies belonging to the Branderfleck Formation (upper Albian to lower Turonian) crop out and contain locally abundant corals. The fauna described here derives from Middle Cenomanian sediments. This study complements a former revision. In total, the fauna includes 98 species in 46 genera, belonging to 16 scleractinian superfamilies and two octocorallian families. One species – Enallhelia octasepta – is described as new. The fauna that was formerly located at the northern part of the Apulian plate (Austroalpine unit), south of the Penninic Ocean, shows palaeobiogeographic relationships to Cenomanian faunas from the Basque-Cantabrian Basin, the Prebetic zone, the Pelagonium, and the Quillan Basin, indicating stronger connections to Tethyan rather than Boreal faunas. The fauna also shares species with Aptian and Albian, but also with Late Cretaceous faunas of the Gosau Basin. Eight genera experienced a range extension; five genera have their last occurrence in the Middle Cenomanian fauna, and three genera have their first occurrence. Although the fauna presents numerous genera that became widespread in the Late Cretaceous, its generic composition is more closely related to late Early Cretaceous corals than to post-Cenomanian corals. The faunal turnover at the Cenomanian/Turonian boundary was not marked by the sudden appearance of new faunal elements, but rather by the disappearance of taxa. Some faunal elements that constitute post-Cenomanian faunas already existed in the Cenomanian, but they were very rare. The increase of taxa after the Cenomanian/Turonian boundary took place during the Coniacian and Santonian.

Late Sinemurian and Early Pliensbachian Radiolaria from Mount Rettenstein (Northern Calcareous Alps, Austria). Part 2. Entactinaria and Spumellaria

On Mount Rettenstein (Northern Calcareous Alps, Austria) a 95-m-thick Lower Jurassic succession of grey siliceous limestone and marl allowed us to study well-preserved and diverse radiolarian assemblages. The succession crossing the Sinemurian–Pliensbachian boundary yielded seven productive radiolarian samples, five of which were assigned to the Upper Sinemurian and two to the Lower Pliensbachian. In this article, we present 24 species and nine genera belonging to the order Entactinaria, and 66 species and 27 genera to the order Spumellaria. One genus (Tetractoma Cifer nov. gen.) and six species are described as new: Charlottalum austriacum Cifer nov. sp., Crucella optima Cifer nov. sp., Hexapyramis? sphaericus Cifer nov. sp., Paronaella triangularis Cifer nov. sp., Pseudoheliodiscus rotaformis Cifer nov. sp., and Tetractoma tollmanni Cifer nov. gen. nov. sp. In the Sinemurian, by far the most abundant genus amongst either Spumellaria and Entactinaria is Gorgansium. The Pliensbachian samples are, on the other hand, dominated by the genera Archaeocenosphaera and Praeconocaryomma. Compiled stratigraphic and geographic ranges as well as synonymies, descriptions and remarks are provided.

Taxonomic revision of the canaliculate radiolitid (rudist, bivalve) genus Lattenbergites Lupu, 1987 from the Upper Cretaceous of the central and eastern Mediterranean Tethys: palaeobiogeographic distribution

Lattenbergites Lupu was previously considered to be a new genus of canaliculate radiolitid from the middle–upper Coniacian of Lattenberg, Germany. The re-examination of the holotype and paratypes of the type species L. hermi Lupu of this genus reveals diagnostic characters of Joufia milovanovici (Slišković), including the presence in the left valve of a single ring of radial canals in the calcitic outer shell layer, the canals having sub-rectangular cross-sectional shape flanking the myocardinal apparatus in the originally aragonitic inner shell layer, and a pair of tubular structures in its postero-ventral part, opposing the ‘pseudopillar’-like structures of the right valve. Therefore, we propose that Lattenbergites Lupu, is a junior synonym of Joufia milovanovici. J. milovanovici from the Malatya, Haymana-Polatlı Basins and eastern Pontides of Türkiye, as well as the Roşia Basin of Romania is also described and compared to Lattenbergites. The presence of J. milovanovici in the Northern Calcareous Alps during the middle–late Coniacian, Romania during the late Santonian to early–middle Campanian, and Türkiye during the late Maastrichtian, allows us to reconsider the palaeobiogeographic distribution of this species within the Mediterranean Tethys during Late Cretaceous time, as well as for the genus Joufia.

Taxonomic and stratigraphic remarks on Placites urlichsi Bizzarini, Pompeckjites layeri (Hauer), Carnites floridus (Wulfen) and Sageceras haidingeri (Hauer)

Investigations of an Lower Carnian Wettersteinkalk ammonoid fauna found in the Hochobir massif (Carinthia/Austria) gave rise to problems in the taxonomic relationship within the Triassic ammonoid Family Pinacoceratidae. The morphological parameters of the ammonoid genus Pompeckjites are rather unclear. Morphological variation of at least two ammonoid species as Pompeckjites layeri Hauer on one end, Placites urlichsi Bizzarini on the other end have to be take into account. Numerous field surveys, studies and excavations on upper Wettersteinkalk sites within the Karavank Mountains and Hallstatt-facies sites in the Northern Calcareous Alps were implemented and compared with the reference sites in the Dolomites. As a consequence of our investigations, the Hochobir Wettersteinkalk ammonite assemblage is thought to be equivalent in time to the ammonoid fauna of the Upper San Cassian Formation. The frequent occurrence of the Julian (Lower Carnian) ammonoid Placites urlichsi Bizzarini may be a powerful tool in field investigations for a refined correlation of the upper Wettersteinkalk reef limestone to the coeval basinal facies of the Upper San Cassian Formation (Lower Carnian/upper Trachyceras aonoides Zone). As a result of this study Placites urlichsi was included in the genus Pompeckjites. This paper could be an attempt to recognize the differences in juvenile forms of Pompeckjites layeri and Placites urlichsi and other similar disciform ammonoid genera like Carnites floridus and Sageceras sp. based on suture lines, polished transversal-sections and morphological features.

Facies, biostratigraphy and isotope chemostratigraphy of the Tithonian‒Berriasian transition in the easternmost Getic Carbonate Platform (Southern Carpathians, Romania)

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.

Compositional and taphonomic gradients show fluctuating depositional conditions on Middle Jurassic brachiopod-rich accumulations from Northern Calcareous Alps (Austria–Germany)

ABSTRACT Brachiopod-rich accumulations of the well-known ‘VilserKalk’ calcareous units from the Middle Jurassic of Zehrer (Allgäuer Alps) have been recognised and analysed from a taphonomic standpoint. These brachiopod concentrations are frequent in the Jurassic deposits of various Alpine-Mediterranean localities, usually related to resedimentation processes generated by high-hydrodynamic episodes. In the four brachiopod-bearing accumulations recorded, high concentrations of mainly articulate shells are preserved in pocket-like deposits made up of brachiopod communities with quite different structure, size-frequency distribution, diversity and taxonomic composition. The analysed taphocharacters indicate different hydrodynamic regimes of diverse intensity for each accumulation, resulting in a gradation of the resedimentation processes. The inferred transport of the shells from the source area is minimal, the bioclastic levels constituting para-autochthonous assemblages without significant spatial averaging. The four defined taphofacies include different assemblages that chronostratigraphycally span the latest Toarcian-early Bajocian interval. These taphofacies are interpreted in terms of depth-related variations concurring with environmental disturbance events in several phases of the evolutionary history of the basin, progressively ranging from shallower proximal accumulations to shell-beds originated in more distal depositional environments.

Facies character and evolution of a mixed carbonate–siliciclastic shelf: Upper Triassic–Lower Jurassic succession in the eastern Northern Calcareous Alps (Stumpfmauer, Austria)

Western Tethys sedimentary successions constitute fundamental archives of Late Triassic–Early Jurassic environmental, carbonate production and tectonic changes. During the Late Triassic, the Northern Calcareous Alps (Austria) belonged to the Western Tethys passive margin, characterised by the deposition of the early-dolomitized peritidal Hauptdolomit (Norian) adjacent basinward to the Dachstein carbonate shelf and passing upward to the mixed carbonate–siliciclastic Kössen Formation (Upper Norian–Rhaetian). The Kössen Fm. was subdivided into the lower shallow-water Hochalm Member and the upper Eiberg Member, accumulated in an intraplatform basin coeval to shallow-water carbonates (Upper Rhaetian Limestone). The Eiberg Mb. and overlying Jurassic strata were extensively studied as a continuous marine record across the Triassic/Jurassic boundary. In contrast, shallow-water successions, time-equivalent to the Eiberg Mb. and Upper Rhaetian Limestone, located North of the Eiberg Basin, are poorly investigated. This study focusses on the approximately 350 m thick Norian to Lower Jurassic succession cropping out in the eastern Northern Calcareous Alps (Stumpfmauer). The 32 distinguished lithofacies compose seven, vertically superimposed, sedimentary units (A–G), belonging to the Hochalm Mb. of the Kössen Fm. (Unit A peritidal cyclothems, Unit B claystone/marlstone with fossiliferous beds, Unit C coral boundstone to floatstone), Upper Rhaetian Limestone (Unit D subtidal cyclothems with claystone), shallow-water carbonate strata transitional to Lower Jurassic (Unit E ooidal coated grain peloidal grainstone with basal transgressive lag, Unit F bivalve-rich, microbialite and oncoidal lithofacies, previously attributed to the Upper Rhaetian Limestone) and Hettangian–Sinemurian Kalksburg Fm. (Unit G cross-laminated coated grain peloidal grainstone with quartz and chert). The detailed lithofacies characterisation presented in this study contributes to the knowledge on the Northern Calcareous Alps stratigraphy and depositional environments across the Triassic/Jurassic boundary. The identified sedimentary units can be framed in the evolution of Western Tethys and share similarities with depositional systems from the Western Carpathians, Transdanubian Range, Southern Alps and Dinarides suggesting coherent sedimentary response and environmental, climate and tectonic controls in different palaeogeographic domains.

Extinctions and recoveries in the Allgäu Basin (Northern Calcareous Alps) during the end-Triassic mass extinction

Extinctions and recoveries in the Allgäu Basin (Northern Calcareous Alps) during the end-Triassic mass extinction