Gosau Group Research Articles

Application of micro‐CT to resolve textural properties and assess primary sedimentary structures of deep‐marine sandstones

AbstractOver the past decade, there has been growing interest in the sedimentological community to use micro X‐ray computed tomography to analyse microfacies in sediment cores. However, little attention has been paid to the application of micro‐computed tomography in lithified deposits, even though this can allow their texture to be characterised in three dimensions, providing key information about sedimentary structures. A novel application of micro‐computed tomography in lithified sediment‐gravity flow deposits is presented with the objective of characterising their internal 3D sedimentary structures. This technique is applied to three deep‐marine sandstones showing different compositional properties: Cretaceous Gosau Group (Austria), Eocene Hecho Group (Spain) and the Oligocene Annot Formation (France). From micro‐computed tomography data the size of particles and their distribution throughout the sample is reconstructed in 3D permitting a better visualisation of sedimentary textures. Particle distributions computed from micro‐computed tomography are similar to those computed from thin section image analysis, corroborating the reliability of the micro‐computed tomography to evaluate grain‐size trends. Micro‐computed tomography is complemented with micro‐X‐ray fluorescence and thin section petrographic analyses. In cases where mineral composition or grain size are homogeneous or matrix and grains have similar mineral composition, sedimentary structures do not appear visible from micro‐X‐ray fluorescence or thin section analyses. By separating particles based on their computed tomography density, it is possible to isolate the coarsest fraction, highlighting the sedimentary structures. This study demonstrates (i) the potential of micro‐computed tomography in analyses of sedimentary structures from outcrop data and (ii) the importance of the mineralogical composition and degree of grain sorting in assessing the origin of structureless deposits. Considering the importance of visualising sedimentary structures when interpreting depositional processes, micro‐computed tomography is a new and reliable tool to assess the physical properties of sandstones and to analyse their internal 3D sedimentary structures.

Vestige of a subaerial rock avalanche deposit in an upper Cretaceous synorogenic wedge-top succession (Gosau Group, Eastern Alps)

Modern subaerial catastrophic mass-wasting (rockslides, rock avalanches) are identified as being huge bulky masses with a surface littered with boulders to blocks. The identification of partly preserved deposits of ‘fossil’ subaerial catastrophic mass-wasting, in contrast, requires assessment of deposit fabrics. In the Alps, within the synorogenic Gosau Group (Turonian to Ypresian) that accumulated in an oblique-convergent setting, we had identified a ‘megabed’ (Wäschkogel megabed) up to 95 m thick that is interpreted as a vestige of a subaerial rock avalanche deposit. This megabed is an extremely poorly sorted, disordered, clast-supported deposit of sand- to boulder-sized dolostone fragments from an upper Triassic succession that comprises the local bedrock. In the megabed, numerous clasts display crackle, jigsaw and mosaic fabrics with fitted subclast boundaries. The matrix is a lithified gouge of fragmented dolomite crystals. In its upper part, the megabed displays very thick planar parallel stratification. Across strata, no change in sediment fabric is discerned.The distinctive features of the megabed, i.e., the sharp intercalation between fluvial deposits, large bed thickness with a uniform fabric, abundant clasts fractured in situ, and the gouge matrix all indicate that the megabed and lateral correlatives accumulated from a rock avalanche. The planar stratification in the upper part of the megabed is interpreted as a dynamic feature produced by internal simple shear during a terminal phase of rock avalanche propagation. Bedrock geology and the distribution of other Gosau Group deposits in the area suggest that the rock avalanche propagated along a SSW–NNE striking incised valley. This is the first identification of a subaerial rock avalanche deposit in the Gosau Group. Our case study may help to consolidate the awareness of deposits of fossil subaerial catastrophic mass-wasting.

Geochemical anomalies caused by meteorite impact and volcanism at the Cretaceous-Paleogene boundary, Wasserfallgraben (Lattengebirge, Germany)

The Cretaceous-Paleogene (K/Pg) mass extinction is the only major mass extinction event that is known to be related to a major meteorite impact (Chicxulub, Mexico) and also occurred during major flood basalt eruptions (Deccan Traps, India). Here, we present geochemical proxies for impact and volcanism analysed in the same sediment samples from the deep-marine sedimentary record of the Gosau Group spanning the K/Pg boundary at Wasserfallgraben, Germany. We measured major and trace elements, including iridium (Ir), tellurium (Te), mercury (Hg), total organic carbon (TOC), and organic carbon isotopes (δ13Corg) on 33 samples from 2 m below to 1.36 m above the K/Pg boundary, a timespan of ∼260 ka. Results show an undisturbed profile, confirmed by changes in calcareous nannofossils assemblages, with a sharp positive Ir peak (2.3 ppb) at the K/Pg boundary (0–10 cm, 25 cm). Volcanic proxies (Hg/TOC, Te/Th) show three distinct peaks not corresponding to the Ir peak, suggesting a volcanic origin, and higher values in the earliest Danian. Compared to the profile in Bidart the proxies of volcanism are less intense in our profile, indicating that the “Deccan Signal” is either diluted or not present in some locations worldwide. The time recorded in the sampled sediments is short (∼0.26 Ma) compared to Deccan flood basalt eruptions (∼1 Ma), but elevated Hg/TOC and Te/Th ratios in the Danian sediments suggests the impact happened prior to the main volcanic outgassing of the Deccan Traps. Our results support the hypothesis that the impact might have triggered the largest, rapidly-erupted Deccan lava formations.

The Paleogene Gosau Group Slope Basins of the Incipient Eastern Alpine Orogenic Wedge: A Case Study at the Gams Basin (Austria)

This study investigates the Paleogene deep-water depositional system of the Gosau Group at Gams, Styria (Austria). The examined sections of the Danian to the Ypresian age (NP1–NP12) comprise sediments of the Nierental and Zwieselalm Formations. Four deep-water clastic facies assemblages were encountered: (1) pelagic marls with thin turbidites, (2) carbonate-rich turbidites, (3) carbonate-poor turbidites, and (4) marl-bearing turbidites; slump beds and mass flow deposits are common features in all facies assemblages. Based on heavy mineral, thin section, microprobe, and paleoflow analyses, provenance was from the surrounding Northern Calcareous Alps (NCA) rocks and exhuming metamorphic Upper Austroalpine units to the south. In addition, biogenic calcareous material was delivered by adjacent contemporaneous shelf zones. The sedimentary depocenter was situated at the slope of the incipient Alpine orogenic wedge, in frontal parts of the NCA, facing the subducting Penninic Ocean/Alpine Tethys. The evolution of the Gams Basin was connected to the eoalpine and mesoalpine orogeny and the adjunctive transpressional setting. The Gams deep-water depositional system is interpreted as an aggrading or prograding submarine fan, deposited into a small confined slope basin, positioned along an active continental margin, bound and influenced by (strike-slip) faults, related to crustal shortening. The development of the Gams slope basin and its infilling sequences was mainly dominated by tectonism and sediment supply, rather than by eustatic sea-level fluctuations. The basin was cut off during the Eocene due to renewed orogeny. A Quaternary analogue for the Upper Cretaceous to Paleogene basin setting of the Gams area is represented by the Santa Monica Basin in the California Continental Borderland.

Stratigraphic architecture of a mixed clastic-carbonate succession and 87Sr/86Sr-based chronostratigraphy along the margin of a synorogenic extensional basin (Hochmoos Formation, upper Santonian, Northern Calcareous Alps)

Abstract The Gosau Group (Turonian to Ypresian) of the Eastern Alps is a synorogenic wedge-top succession that accumulated in active depocenters in an oblique-convergent plate tectonic setting. Due to high morphological differentiation of depocenters by tectonism, the Gosau Group displays a wide range of facies as well as marked facies heteropy and thickness variations over short lateral distances. In the area of the locations Gosau and Russbach, the Hochmoos Formation along the SE basin margin near Gosauschmied comprises coastal to shallow-marine deposits and small rudist bioconstructions and was investigated by way of field mapping, profile descriptions, microfacies analysis, isotope measurements and assessment of fossil content. Strontium isotope ratios (87Sr/86Sr) from 0.707485 (oldest) to 0.707549 (youngest) indicate a latest Santonian age, with the youngest parts of the Hochmoos Formation possibly extending into the Campanian. On the west side of the study area, the succession of lithologies and fossil content record transgression of a fan-delta to marginal-marine environment (lowstand to transgressive systems tract), followed by shallow neritic deposition (part of the transgressive systems tract) and, finally, by progradational stacking of limestone beds in the highstand systems tract, culminating in growth of rudist thickets in an inner shelf and partially protected ‘lagoonal’ milieu. Eventually, at the inception of the following falling stage systems tract, input of large clasts of Dachstein Limestone, quartz and chert record a recurrence of the subaqueous part of a fan-delta. On the east side of the study area, a preponderance of rudist-clastic limestones over a few rudist biostromes preserved in situ indicate a normal-marine environment punctuated by high-energy events, such as storms or tsunami. The scarcity of benthic foraminifera and the presence of only isolated specimens of colonial corals underscore a habitat with a calcarenitic substrate frequently shifted by currents. Several lines of evidence indicate that the western part of the study area was more proximal relative to the eastern one. With a maximum thickness of 68 m, the Hochmoos Formation at Gosauschmied is slightly thicker and more distal than outcrops located nearer to the basin margin and farther towards the SE (Schmiedsippl, Katzhofgraben), but significantly thinner than the nearly 300 m at Gosau Pass-Gschütt, or the thickness of 170 m observed in the area of Rigaus-Abtenau farther in the West. These thickness variations are interpreted as a result of extensional syndepositional tectonism. At Gosauschmied, the vertical arrangement of facies records a cycle of relative sea-level change that may have been tectonically enhanced.

Palynological and calcareous nannofossil investigation of the Gosau Group deposits from three boreholes in the Vienna Basin, Austria

Palynological and calcareous nannofossil investigations on samples from the basal part of the Gosau Group succession in three boreholes (Glinzendorf T1, Gänserndorf T3 and Markgraf Neusiedl T1) in the Vienna Basin provide calibrated age assessment of late Coniacian to early Campanian age for this thick non-marine to marginal-marine siliciclastic interval.

A brackish to non-marine aquatic and terrestrial fossil assemblage with vertebrates from the lower Coniacian (Upper Cretaceous) Gosau Group of the Tiefengraben locality near St. Wolfgang im Salzkammergut, Austria

The Turonian–Coniacian continental fossil record in Europe is scarce. Here we present a new fossil assemblage of early Coniacian age that was systematically collected from the coal-bearing Gosau Group of the Tiefengraben locality near St. Wolfgang, Austria. The diverse assemblage is composed of at least 60 taxa including sporomorphs and Normapolles-related pollen, seeds and leaves of angiosperms and gymnosperms, charophytes, gastropods, bivalves, ostracods, termites, fishes, crocodiles and dinosaurs. Concerning charophytes, ostracods, gastropods, crocodiles and dinosaurs, the discovered specimens either extend the temporal and spatial range of specific groups (in some cases as possible relict forms) or suggest the occurrence of new taxa. The discovered remains of algae, molluscs, ostracods, calcareous nannofossils and lepisosteid fish represent a mixed faunal assemblage from different palaeohabitats, from marginal marine to low salinity and freshwater or terrestrial environments. As Normapolles-related angiosperm plants dominate the flora with a relatively high number of dentate leaves, a slightly cooler microenvironment compared to other Turonian–Coniacian Central European localities is indicated. The characteristically grooved crocodylian teeth of Tiefengraben differ from the previously known Upper Cretaceous European crocodyliform teeth and suggest a more diverse crocodyliform fauna in the region. Dinosaurs are represented by teeth of at least three different theropods, the largest of which is referred here to as basal tetanurans. The fossil assemblage of this early Gosau Group occurrence is of great importance for our understanding of the continental floristic and faunistic composition of the western Tethyan archipelago during the Cenomanian–Campanian gap.

An integrated multi-proxy study of cyclic pelagic deposits from the north-western Tethys: The Campanian of the Postalm section (Gosau Group, Austria)

The Upper Cretaceous Postalm section in the Northern Calcareous Alps (Austria) exposes pelagic deposits of the northwestern Tethys whose cyclostratigraphy and palaeoenvironments were examined in this study.The section displays rhythmic deposits of Santonian to late Campanian age (Gosau Group). The Santonian/Campanian transition is characterised by condensed greyish carbonates, while the younger deposits are composed of reddish foraminiferal packstones displaying distinct limestone-marl alternations. A biostratigraphic framework based on planktonic foraminifera and calcareous nannofossils is supported by carbon and strontium isotope stratigraphy as well as magnetostratigraphy. The carbon isotope data allow to correlate the Postalm section to other Tethyan reference sites and to identify δ13C events, such as the Late Campanian Event. Spectral analyses of three independently assessed proxies (δ13C, Fe content and the thickness of limestone/marl couplets) in the upper, continuously exposed section part identified 17 to 18 405 ka cycles spanning the mid to upper Campanian (Contusotruncana plummerae to Gansserina gansseri Zones or CC21/UC15c to CC23a/UC16 nannofossil zones).

Vertebrate remains from the Turonian (Upper Cretaceous) Gosau Group of Gams, Austria

A new, systematically collected vertebrate assemblage from the upper Turonian Schönleiten Formation of Gams bei Hieflau, Austria (Northern Calcareous Alps) is described here. The material consists of teeth and bones of chondrichthyan (Selachimorpha indet., Ptychotrygon gueveli) and osteichthyan fishes (cf. Lepisosteus sp., Vidalamiinae indet., Pycnodontidae indet.), amphibians (cf. Thaumastosaurus sp.), lizards (’Lacertilia’ indet.), mosasauroids (Tethysaurinae indet.), Theriosuchus-like and other, peculiar crocodyliforms and theropod dinosaurs (cf. Paronychodon sp.). The faunal composition is most similar to the Santonian fauna of Iharkút, western Hungary, a phenomenon that can be explained by the spatial and temporal closeness of the two landmasses. The Gams assemblage is of great importance since continental vertebrates from the Cenomanian to Santonian interval of Europe are extremely scarce, and it provides a small but significant link between older and younger vertebrate faunas in the region.

New coral genera and species from the Rußbach and Gosau area (Upper Cretaceous; Austria)

From the Coniacian to Santonian of the Gosau Group in Austria, six new genera (Astraraeatrochus, Geroastrea, Pachyheterocoenia, Pachyphylliopsis, Paractinacis, Synhydnophora) within the families Astraraeidae, Heterocoeniidae, Negoporitidae, Phyllosmiliidae, and Synastraeidae, and 12 new species of Scleractinian corals are established (Astraraeatrochus bachi, Crinopora ireneae, Crinopora thomasi, Geroastrea alexi, Gosaviaraea aimeae, Nefocoenia seewaldi, Nefocoenia werneri, Pachyheterocoenia leipnerae, Pachyphylliopsis magnum, Paractinacis uliae, Proplesiastraea rivkae, and Synhydnophora wagreichi). The new taxa emerged during a systematic revision of the coral fauna of the so-called Gosau facies in the area of Rusbach and Gosau (Austria), which was for the first time carried out by the systematic preparation of thin sections and the application of more profound measurements of the corallite dimensions.

The Santonian – Campanian boundary and the end of the Long Cretaceous Normal Polarity-Chron: Isotope and plankton stratigraphy of a pelagic reference section in the NW Tethys (Austria)

The base of the Campanian still lacks a designated primary marker and a defined GSSP (Global Boundary Stratotype Section and Point). We present a Santonian–Campanian boundary section from the Postalm in the Northern Calcareous Alps of Austria as a possible reference section for the northwestern Tethys. Including nearby complementary Gosau Group sections, the stratigraphy for this time interval is based on palaeomagnetic and stable isotope data, planktonic foraminifera and calcareous nannoplankton bio-stratigraphy, and strontium isotope stratigraphy, together with published ammonite, crinoid and inoceramid data. The Postalm section shows a deepening trend from upper Santonian conglomerates and grey shelf marls to pelagic bathyal red marly limestones of mainly Campanian age. Palaeomagnetic data allow identifying the top of the Long Cretaceous Normal Polarity-Chron C34n and the following reversal in the lower part of the red marly limestones. A 1 m-thick interval of high magnetic susceptibility is present at the end of C34n. Two of the main suggested biomarkers to pinpoint the Santonian–Campanian boundary, i. e. the last occurrence of the planktonic foraminifer Dicarinella asymetrica and the first occurrence of the nannofossil Broinsonia parca parca, occur in close proximity above the reversal, which is suggested herein as the main marker event for the base of the Campanian. Strontium isotope stratigraphy indicates a value of 0.707534 (mean of four measurements at the boundary interval) for the base of the Campanian in the Postalm section. Both carbon and oxygen isotope values show a negative excursion just below the boundary. The positive Santonian–Campanian carbon isotope event starts probably just below the reversal but seems to be diagenetically distorted. This interval is considered to correspond to a short sea-level high in the late Santonian followed by a distinct lowstand at the Santonian–Campanian boundary.

Geological evolution of the southwestern part of the Veporic Unit (Western Carpathians): based on fission track and morphotectonic data

AbstractZircon and apatite fission track (FT) and morphotectonic analyses were applied in order to infer quantitative constraints on the Alpine morphotectonic evolution of the western part of the Southern Veporic Unit which is related to: (1) Eo-Alpine Cretaceous nappe stacking and metamorphism of the crystalline basement in the greenschist facies. (2) Exhumation phase due to underthrusting of the northerly located Tatric-Fatric basement (~ 90–80 Ma), followed by a passive en-block exhumation with cooling through ~ 320–200 °C during the Palaeocene (ZFT ages of ~ 61–55 Ma). (3) Slow Eocene cooling through ~ 245–90 °C, which most likely reflected erosion of the overlying cover nappes and the Gosau Group sediments. Cooling reached up to 60 °C till the Oligocene (AFT ages of ~ 37–22 Ma) in association with erosion of cover nappes. The efficient Eocene erosion led to the formation of the first Cenozoic planation surface with supergene kaolinization in many places. (4) The early Miocene erosion coincided with surface lowering and resulted in the second planation surface favourable for kaolinization. (5) In the middle Miocene, the study area was covered by the Poľana, Javorie, and Vepor stratovolcanoes. (6) The late Miocene stage was related to the erosion and formation of the third Cenozoic planation surface and the final shaping of the mountains was linked to a new accelerated uplift from the Pliocene.

On late Santonian ammonites from the Hofergraben Member (Gosau Group, Upper Cretaceous, Austria)

On late Santonian ammonites from the Hofergraben Member (Gosau Group, Upper Cretaceous, Austria)

Geometry of growth strata in a transpressive fold belt in field and analogue model: Gosau Group at Muttekopf, Northern Calcareous Alps, Austria

The thrust sheets of the Northern Calcareous Alps were emplaced during Late Cretaceous thrustdominated transpression expressed by thrust sheets segmented by closely spaced tear faults. Thrust sheet-top sediments were deposited during thrusting and associated fold growth and were controlled by active folding and tearing. We observe two types of angular unconformities: (1) Angular unconformities above folds between tear faults conform with the model of progressive unconformities. Across these unconformities dip decreases upsection. (2) Here, we define progressive unconformities that are related to tear faults and are controlled by both folding and tearing. Across these unconformities both strike and dip change. In growth strata overlying folds dissected by high-angle faults, such unconformities are expected to be common. We used analogue modelling to define the geometry of the tear faults and related unconformities. Within the syn-tectonic sediments, a steep, upward flattening thrust within a broader, roughly tulip-shaped drag zone develops. The thrust roots in the tear fault in pre-tectonic deposits and is curved upward toward the downthrown block. Vertical offset on the thrust is related to differential vertical uplift caused by, for example, growth of folds with different wavelength and amplitude on either side of the tear fault. Formation of progressive unconformities is governed by the relationship between the rates of deposition and vertical growth of a structure. Fault-related progressive unconformities are additionally controlled by the growth of the vertical step across the tear fault. When the rates of vertical growth of two neighbouring folds separated by a tear fault are similar, the rate of growth across the tear fault is small; if the first differ, the latter is high. Episodic tear fault activity may create several angular unconformities attached to a tear fault or allow the generation of angular unconformities near tear faults in sedimentary systems that have a rate of deposition too high to generate classical progressive unconformities between the tear faults.

Provenance of the Upper Cretaceous to Eocene Gosau Group around and beneath the Vienna Basin (Austria and Slovakia)

Chemistry of detrital garnets, chrome spinels and tourmalines of 30 selected samples in combination with the general heavy mineral distribution from 523 sandstone samples of the Upper Cretaceous to Eocene Gosau Group of the eastern part of the Eastern Alps and the western West Carpathians result in an advanced picture of sedimentary provenance and palaeogeographic evolution of that area. Garnets from Coniacian to Campanian sediments are partly derived from a metamorphic sole remnant of Neotethys ophiolites to the south. Tectonically high ophiolitic nappes, later on completely eroded, supplied mainly the paleogeographically southern Grunbach and Glinzendorf Gosau basins with ultramafic detritus, represented by chrome spinels of a mixed harzburgite/lherzolite composition, whereas no direct indications for a northern ophiolitic source, the Penninic accretionary wedge to the north of the Gosau basins, could be found. In the younger part of the Gosau basins fill, from the Maastrichtian to the Eocene, only almandine-rich garnets could be observed suggesting a southern provenance from low-grade metamorphic metapelites of exhuming Austroalpine metamorphic complexes. Ophiolite detritus is reduced in the Maastrichtian and disappears in the Paleogene.

Carbon, oxygen and strontium isotopes as a tool to decipher marine and non-marine environments: Implications from a case study of cyclic Upper Cretaceous sediments

Abstract The interplay of Late Cretaceous basin subsidence and oscillations in sea level produced a mixed freshwater–marine succession within the Upper Cretaceous Gosau Group of the Northern Calcareous Alps. Cored sections from wells of the Glinzendorf and Gießhübl Syncline, as well as sediments from the outcrop area of Grünbach–Neue Welt and Slovakian equivalents have been investigated for their stable isotopic composition. Bulk carbonate δ 13 C and δ 18 O values of 116 fine-grained samples (shales, siltstones, marls) and 87 Sr/ 86 Sr values of 10 samples from the borehole Markgrafneusiedl T1 were analysed in order to distinguish between non-marine and marine deposits and to compare and correlate isotope characteristics of the different Gosau synclines and basins. Non-marine samples have significantly lower mean δ 13 C values compared to the mean of marine samples. The discrimination between a marine and non-marine group using δ 18 O is also highly significant statistically, even though the difference between the average non-marine and marine values is small. Strontium isotope values of marine intervals are near the range of values of normal Upper Cretaceous sea water but show a trend towards higher ratios in marginal marine and non-marine deposits. Although diagenesis and the detrital carbonate admixture partly influence the isotopic composition, the original environmental signal can still be reliably identified.

Geochemistry of fine-grained sediments of the upper Cretaceous to Paleogene Gosau Group (Austria, Slovakia): Implications for paleoenvironmental and provenance studies

Bulk rock geochemistry of 169 fine-grained sediment samples of the upper Cretaceous to Paleogene Gosau Group (Northern Calcareous Alps, Austria and Slovakia) from borehole and outcrop localities was performed to separate non-marine and marine deposits. Geochemical characteristics of different Gosau depositional systems, basins and sediment provenance using major-, trace-, and rare earth elements were also investigated. Geochemical proxies such as boron concentrations were tested for seeking the possibilities of paleosalinity indicators. Due to the fact that several pelagic sections are represented by extremely low boron contents, B/Al* ratios are recognized as more robust and differentiate reliably between marine (mean: 160 ± 34) and non-marine (mean: 133 ± 33) samples. Using statistical factor analysis, hemipelagic to pelagic samples from the Gießhübl Syncline and Slovakian equivalents can be differentiated from marginal-marine to non-marine samples from the Grünbach and Glinzendorf Syncline related to terrigenous (SiO2, Al2O3, K2O, Th, Rb, Zr and others) and pelagic indicative elements (CaO, Sr, TOT/C and B/Al*). A clear indication for ophiolitic provenance is traced by high amounts of chromium and nickel. Only non-marine successions of the Glinzendorf Syncline show higher Cr and Ni concentrations (up to 250 and 400 ppm, respectively) and enriched Cr/V and Y/Ni ratios trending to an ultramafic source.

Dasycladaleans from the Upper Turonian to Santonian of Austria (Gosau Group pro parte) and paleobiogeographic considerations

Previously unreported dasycladaleans and one morpho-taxon of assumed algal origin are described from Upper Turonian to Santonian rocks of the Lower Gosau Subgroup (LGS) of the Northern Calcareous Alps. A taxonomic inventory of green-algal/benthic foraminiferal assemblages shows that assemblages of “pure” carbonate environments are more diverse than those of siliciclastic and mixed siliciclastic-carbonate settings. A comparison of the taxonomic inventory of the LGS with assemblages in similar sedimentary successions of the Alpine-Mediterranean realm shows the highest similarity with the “Mirdita Zone” of the internal Dinarids. Comparability of assemblages, however, is limited due to narrow chronostratigraphic overlap and/or because of scarcity of data from areas outside the Alps. Although higher than previously known, the total diversity of the green-algal/benthic foraminiferal assemblage of the LGS is clearly inferior to that of the peri-Adriatic carbonate platforms.

The dinocyst record across the Cretaceous/Palaeogene boundary of a bathyal mid-latitude Tethyan setting: Gosau Group, Gams Basin, Austria

A high-resolution palynological study carried out across the Cretaceous/Palaeogene (K/Pg) boundary in two sections (Knappengraben and Gamsbach) of the Gosau Group near Gams (Gams Basin, Northern Calcareous Alps, Austria) has identified over 178 dinoflagellate species and subspecies from 89 rock samples. In most samples, the dinocysts are moderately well to well preserved, but associated with reworked material. Some well-known marker species around the K/Pg boundary, such as Carpatella cornuta, Spongodinium delitiense, Trithyrodinium evittii, Palynodinium grallator, Manumiella druggii, Cordosphaeridium fibrospinosum, Membranilarnacia? tenella, Senoniasphaera inornata, Damassadinium californicum, and Dinogymnium acuminatum have been recorded from the samples studied. In addition to these, Trabeculidinium quinquetrum, Lejeunecysta izerzenensis, Batiacasphaera rifensis, Impagidinium maghribensis and Cyclonophelium compactum represent local markers. A Spongodinium delitiense acme is recorded in both sections above the K/Pg boundary and is interpreted to indicate a transient cooling event of oceanic surface waters. The stratigraphic distribution of the dinocyst species indicates that they were not seriously affected by the mass extinction event at the K/Pg boundary, but their diversity slightly increases above it. The composition of the assemblages, however, changes drastically. Six dinocyst assemblages and four palynofacies assemblages were identified by means of cluster analysis. Their distribution does not show any regular pattern. The increase of phytoclasts in the Danian clearly indicates enhanced terrestrially derived input into the basin. The palynological and sedimentological differences between the two sections can be explained by small scale local lateral variations.

Late Cretaceous extension overprinting a steep belt in the Northern Calcareous Alps (Schesaplana, Rätikon, Switzerland and Austria)

The Triassic to Cretaceous sediment succession of the Lechtal Nappe in the western part of the Northern Calcareous Alps (NCA) has been deformed into large-scale folds and crosscut by thrust and extensional faults during Late Cretaceous (Eoalpine) and Tertiary orogenic processes. The following sequence of deformation is developed from overprinting relations in the field: (D1) NW-vergent folds related to thrusting; (D2) N–S shortening leading to east–west-trending folds and to the formation of a steep belt (Arlberg Steep Zone) along the southern border of the NCA; (D3) E–W to NE–SW extension and vertical shortening, leading to low-angle normal faulting and recumbent “collapse folds” like the Wildberg Syncline. D1 and D2 are Cretaceous in age and predate the Eocene emplacement of the Austroalpine on the Penninic Nappes along the Austroalpine basal thrust; the same is probably true for D3. Finally, the basal thrust was deformed by folds related to out-of-sequence thrusting. These results suggest that the NCA were at least partly in a state of extension during the sedimentation of the Gosau Group in the Late Cretaceous.