Jiří Kříž and his research in Carnic Alps

An Alpine immigrant: Phragmoceras Broderip, 1839 from the Silurian of the Carnic Alps (Austria)

Silicified kirkbyoid ostracodes from the Cantabrian Mountains (Spain) bear a striking resemblance to those of the Carnic Alps (Austria and Italy). The Spanish ostracodes come from the upper part of the Cuera Limestones (Bashkirian-upper Moscovian), which are exposed along the Playa de la Huelga section (Ponga Nappe) in the coastal area of eastern Asturias, northern Spain. These fossils were collected from upper Moscovian limestones deposited in an outer-platform environment. Most of the material from the Carnic Alps was obtained from the Nassfeld Pass area (eastern Carnic Alps), near the Austrian-Italian border, in limestones of the Kasimovian-Gzhelian Auernig Group and the Lower Permian Rattendorf Group. The several Auernig Group limestones that contain silicified ostracodes were deposited in a shallow-marine environment.Despite the differences in age (according to fusulinids and conodonts), these kirkbyoids are very similar and in some cases identical.Coronakirkbya pramollanew species andKirkbya carniacantabricanew species occur in both areas. Two other pairs of species,Coronakirkbya krejcigrafiBecker, 1978, andCoronakirkbya carinanew species, andAurikirkbyacf.beckeri(Kozur, 1990) andAurikirkbya carinthicanew species, show close affinities, though they are considered to be different species. Most of the species described herein are either very rare or absent in other regions.The close paleobiogeographic relationships between the Cantabrian Mountains and the Carnic Alps, documented previously only by brachiopods, are confirmed.

During the latest Carboniferous and earliest Permian (Virgilian-Wolfcampian), the eastern margin of the Orogrande Basin in south-central New Mexico was rimmed by a narrow, tectonically unstable shelf, on which sediments of the Laborcita and Abo formations were deposited. Sediments of the Hueco Group accumulated on the more stable western margin of the Orogrande Basin. On the eastern shelf, the Laborcita Formation of the northern Sacramento Mountains represents a transition from marine to terrestrial facies and is composed of clastic-carbonate cycles. Limestones accumulated during relative sea-level highstands in a shallow marine shelf environment. Clastic sediments were deposited during relative lowstands when there was strong clastic influx in a nearshore to terrestrial environment. The overlying Abo Formation is composed of terrestrial red beds. On the western shelf, the Shalem Colony Formation of the Hueco Group, equivalent to the Laborcita Formation, is composed of mostly normal marine shallow shelf limestones with only minor interbedded clastics. The Robledo Mountains Formation and Hueco Group reflects a trend from a restricted shallow shelf and tidal flat clastics facies in the lower part to more open conditions in the upper part, which also prevailed during deposition of the overlying Apache Dam Formation. Limestones of the Laborcita Formation and Hueco Group contain smaller foraminifers, algae and problematic carbonate microfossils. All taxa except two pseudoalgae in open nomenclature ( Litostroma (?) sp. and “problematicum gen. 1”) are taxa already described. Compared with the Carnic Alps (Austria/Italy), the assemblages of smaller foraminifers of the Laborcita Formation and Shalem Colony Formation are very similar to those of the Auernig and Carnizza Formations (Auernig Group), and Lower Pseudoschwagerina Limestone (Rattendorf Group), indicating an Orenbugian (“Bursumian”) to Asselian age. Smaller foraminifers of the Robledo Mountains Formation allow correlation with the Grenzland Formation and Upper Pseudoschwagerina Limestone (Rattendorf Group) of the Carnic Alps, dated as Asselian to Sakmarian. Smaller foraminifers of the Apache Dam Formation suggest an Artinskian age, correlating with the Wolfcampian, or the Trogkofel Group of the Carnic Alps.

32 species of bivales are desribed from the lowermost Devonian of the eastern Anti-Atlas, Morocco. The majority of the species are closely related to the species described from Perunica (Prague Basin, Bohemia) and the Northern Gondwana marginal regions (Sardinia, Massif Armoricain, and the Carnic Alps). Two new species (Panenka hollardi n. sp. andVevoda tada n. sp.) are characteristic to the Anti-Atlas. The bivalve dominated communities, known also from Bohemia, Sardinia, Massif Armoricain, and the Carnic Alps are closely related to the cephalopod limestone biofacies and micritic limestone facies. In practice they may be used for the correlation with Perunica and other Gondwanan European basins. Analyses of the Bivalve dominated communities shows that the development of the Anti-Atlas during the Lower Devonian, Lochkovian was very similar to other Northern Gondwana regions and that the distance between Perunica and Northern Gondwana was much smaller than it has been interpreted on the basis of paleomagnetic measurements. In Gondwanan Europe and in Perunica the Silurian type cephalopod limestone facies is developed only up to the lowermost Lochkovian. In Morocco, the cephalopod limestone facies of this type is developed in several other levels higher in the Devonian, at least up to the upper Lochkovian. This may be caused by the paleogeographic position of Morocco during the Lower Devonian being in the same position as the Gondwanan Massif Armoricain, Sardinia, Carnic Alps and Perunican Prague Basin were during the Silurian. They all shifted together during the Lower Devonian to the equatorial region while Morocco changed its position to the temperate region just south of the equatorial region.

A biostratigraphic correlation of the Devonian/Carboniferous (D/C) boundary sections from the Carnic Alps, the Graz Palaeozoic, the Montagne Noire and the Pyrenees resulted in a high‐resolution record of the carbon isotopic composition of micrites (δ13Ccarb), of sedimentary organic matter (δ13Corg) and of oxygen isotope ratios of conodont apatite (δ18Ophosph). The studies focused on the interval between the Upper postera Zone (Late Famennian) and the sandbergi Zone (Lower Tournaisian). For the first time, weak but significant positive carbon isotope excursions in micrites and in the sedimentary organic matter is reported from the Middle and Upper expansa zones of the Carnic Alps. They coincide with a decrease in the oxygen isotope values of conodont apatite. The excursions indicate changes in the global carbon cycle during an episode of high seawater temperatures, and correlate with sedimentary change and a stepwise eustatic rise in the Rhenish Massif. High carbon isotope values were also measured in limestones from the Graz Palaeozoic in the Upper praesulcata Zone, which were previously reported from the Rhenish Massif, Carnic Alps, Montagne Noire and the North America continent. The change from a palmatolepid–polygnathid conodont biofacies to a palmatolepid–bispathodid–branmehlid biofacies in the expansa Zone in the Carnic Alps is obviously influenced by anoxic conditions and repeated transgressive phases. The protognathodids and the polygnathids start to radiate in the Upper praesulcata Zone, after the main end‐Famennian extinction episode. This is connected with the disappearance of the palmatolepids, and environmental stress created by worldwide anoxic conditions, climate change and sea‐level changes, stimulated the radiation of both protognathodids and the polygnathids. The regional correlation of the geochemical records as well as interpretations of these records on a global scale indicate that changes in conodont biofacies of Late Famennian–Early Tournaisian limestones were caused by a complex pattern of environmental changes. Copyright © 2008 John Wiley & Sons, Ltd.

Sequence stratigraphy provides an alternative approach to correlation that may also serve as a predictive framework for the interpretation of sea-level and sedimentological change. The main aim of this study is to apply sequence stratigraphic concepts to the biostratigraphically well constrained shallow to moderately deep shelf carbonates and basinal graptolitic shale facies of the Silurian successions in the Carnic Alps of Austria in order to correlate the sequence packages and sea-level changes established there with those identified in other areas of North America and Europe. Documenting local sea-level curves is essential for determining global eustasy. The sea-level curve for the Silurian of the Carnic Alps has been elaborated within a refined stratigraphic framework for the Silurian based on conodont and graptolite biozonation [Melchin, M.J., Cooper, R.A., Sadler, P.M., 2004. The Silurian Period. In: Gradstein, F.M., Ogg, J.G., Smith, A.G. (Eds), A Geologic Time Scale. Cambridge University Press, Cambridge, pp. 188–201.]. In particular, the minor and frequent sea-level changes within the Silurian of the Carnic Alps are of special interest as these stratigraphic intervals are poorly preserved and not well studied in other Silurian localities. The interpretation of the field and microfacies analysis indicates major sequence boundaries in the Llandovery (3), Wenlock (3), Ludlow (3) and Přídolí–Lochkovian (2) which may be correlated with coeval disconformities in the Appalachian Foreland Basin of eastern North America and/or in the Welsh Basin of the British Isles. The following times appear to represent relative sea-level highstand maxima in the Silurian of the Carnic Alps, as indicated by dark, graptolitic shales in deep shelf to basinal carbonate-dominated sections: a) early Aeronian, approximately the Coronograptus cyphus graptolite Zone/ Demirastrites triangulatus graptolite Zone), b) the early Telychian ( Oktavites spiralis graptolite Zone; Pterospathodus celloni conodont Superzone), c) late Telychian (lower Pterospathodus a. amorphognathoides conodont Zone); d) early to middle Sheinwoodian ( Kockelella ranuliformis to Ozarkodina sagitta rhenana conodont Zones; Monograptus riccartonensis graptolite Zones); e) mid-Wenlock ((?upper Kockelella walliseri conodont Zone; Cyrtograptus rigidus graptolite Zone); f) mid Homerian ( Ozarkodina bohemica conodont Zone; Gothograptus nassa graptolite Zone); g) near the Wenlock–Ludlow boundary ( Neodiversograptus nilssoni graptolite Zone); h) Polygnathoides siluricus conodont Zone; i) near the Ludlow–Přídolí boundary (upper Ozarkodina snajdri Interval Zone); j) lower Přídolí ( Monograptus parultimus graptolite Zone) and k) at the Silurian–Devonian boundary (earliest Lochkovian: Icriodus woschmidti woschmidti conodont Zone. Of these, the earlier (at least b–e) are well represented in the Appalachian Basin, as in Avalonian sections in Great Britain and in Baltica. Johnson [Johnson, M.E., 2006. Relationship of Silurian sea-level fluctuations to oceanic episodes and events. GFF 128, 115–121.] documented eight major highstands in global sea-level during the Silurian. The temporal resolution obtained in the Carnic Alps for local sea-level changes allows for refinement of the Telychian to Přídolí sea-level curve, as the stratigraphic successions are chronologically well-defined using both conodont and graptolite biostratigraphy and K-bentonite levels. Nearly all inferred deepenings in the Carnic Alps section, with the exception of that in the Polygnathoides siluricus conodont Zone, approximately match highstands recorded on the Silurian sea-level curves of Johnson [Johnson, M.E., 1996. Stable cratonic sequences and a standard for Silurian eustasy. In: Witzke, B.J., Ludvigson, G.A., Day, J. (Eds.), Paleozoic sequence stratigraphy – Views from the North American Craton. Geol. Soc. Am. Spec. Pap. vol. 306, Boulder, pp. 203–212., Johnson, M.E., 2006. Relationship of Silurian sea-level fluctuations to oceanic episodes and events. GFF 128, 115–121.]; however, the two Telychian highstands are not distinguished but rather are combined as highstand 4 on the Johnson curve, although they are recognized by Loydell [Loydell, D.K., 1998. Early Silurian sea-level changes. Geol. Mag. 135 (4), 447–471.], and the upper Kockelella walliseri conodont Zone deepening is not explicitly numbered by Johnson. These similarities suggest pervasive and probably eustatic events that are manifested in the Apulia Terrane [Cocks, L.R.M., Torsvik, T.H., 2002. Earth geography from 500 to 400 million years ago: a faunal and palaeomagnetic review. J. Geol. Soc. Lond. 159 (6), 631–644.], Laurentia and Avalonia during these time intervals.

The Zweikofel Formation of the Rattendorf Group in the Carnic Alps (Austria) is 95–102 m thick and consists of a cyclic succession of thin‐ to thick‐bedded fossiliferous limestone and intercalated thin intervals of siliciclastic sediment. The siliciclastic intervals were deposited in a shallow marine nearshore environment. The variety of carbonate facies indicates deposition in a shallow neritic, normal‐saline, low‐ to high‐energy environment. The Zweikofel Formation is characterized by a paracyclic vertical arrangement of facies and represents sedimentary sequences that are not well understood elsewhere in the Tethys. Fusulinids and conodonts from the upper Grenzland and Zweikofel formations in the Carnic Alps clearly suggest that what has been called ‘Sakmarian’ in the Tethys includes both the Sakmarian and Artinskian stages of the Global Time scale. Fusulinids from the lower part of the Zweikofel Formation at Zweikofel closely resemble those of the Grenzland Formation and approximately correlate with the upper part of the Sakmarian and lower part of the Artinskian of the Global Time scale. The upper part of the Zweikofel Formation correlates approximately with the lower‐middle (?) parts of the Artinskian Stage of the Global Time scale. A new regional Hermagorian Stage of the Tethyan scale is proposed between the Asselian and Yakhtashian. The lower boundary of the Hermagorian Stage is proposed to be located at the base of bed 81 in the 1015 section of Darvaz (Tadzhikistan). The boundary between the Hermagorian and Yakhtashian stages is placed at the base of bed 73 in the Zweikofel section at Zweikofel, Carnic Alps. In the Darvaz region, Tadzhikistan, the type area for the Yakhtashian Stage, this boundary has never been precisely defined. The entire fusulinid assemblage of the upper part of the Grenzland and Zweikofel formations reported herein includes 62 species of 18 genera, of which one subgenus and 12 species and subspecies are new. Copyright © 2012 John Wiley & Sons, Ltd.

Contents vol. 25, 1988

The Late Pennsylvanian flora of the Italian Carnic Alps

We conducted a phytosociological study of alpine grasslands with dominant Luzula alpinopilosa in the Julian and Carnic Alps. Based on a comparison with similar communities elsewhere in the Alps we described a new association Junco jacquinii-Luzuletum alpinopilosae, which we classify into the provisional alliance Doronico glacialis-Juncion jacquinii, order Festucetalia spadiceae and class Juncetea trifidi. The new association characterises moist shady grasslands in gullies and on ledges on limestone admixed with marlstone and chert, in the elevation range between 2000 and 2500 m, where the snow cover persists for extended periods. We distinguish three subassociations: -galietosum anisophyllae (the most calcareous form), -potentilletosum aureae (typical form) and -leucanthemopsietosum alpinae (acidophilic form on Werfen sandstones in the Carnic Alps, which is the most similar to the stands of the association Luzuletum alpinopilosae from the Central Alps).

In the late Lochkovian a regression is documented in several areas of the world, followed by a transgression in the early Pragian. Connected with the eustatic variation, a minor extinction event occurred (“Lochkovian-Pragian Event”), affecting several fossil groups, a strong reduction of carbonate production and sedimentary facies changes. The Carnic Alps are a key area for studying this event, because Lower Devonian rocks are widely exposed, representing diverse sedimentary environments from shallow water to relatively deep shelf. Fourteen sections were measured along the Carnic Alps across the Lochkovian-Pragian boundary. In the shallower part of the basin, both the Polinik and the Seekopf formations span the boundary, but evident erosional surfaces are observable in the field at the Lochkovian-Pragian boundary. Above the unconformity, at places the so-called megaclast horizon is present in the Seekopf Formation. In intermediate settings the Rauchkofel Fm. is unconfomably followed by the Kellerwand Fm., and different parts of the upper Lochkovian and lower Pragian are missing in the various sections. In the deeper parts of the basin the transition from the La Valute Fm. to the Findenig Fm. is slightly diachronous from the latest Lochkovian to the earliest Pragian; however, conodonts and tentaculitids are rare in the marly boundary beds, preventing a precise chronostratigraphic calibration of these levels. At places, evidence of subaerial exposure at the formational boundary is documented. In general, the hiatus seems to be larger in the western part of the Carnic Alps, in correspondence with the shallower parts of the succession, suggesting a sea level drop in the late Lochkovian, followed by a transgression in the Pragian. Data from the Carnic Alps are compared with those of other regions of North Gondwana to demonstrate that the sea-level variation at the Lochkovian-Pragian boundary are of global importance

The lower Carboniferous succession of the Carnic Alps represents the best-preserved example of such stratigraphic interval within the Alps, thus providing crucial insights for paleogeographic and paleoclimatic reconstructions. This research focuses on the combined biostratigraphic and sedimentological analyses of a stratigraphic section near Passo di Monte Croce Carnico (central Carnic Alps). The presence of two polygonal sedimentary structure-bearing levels suggests a sea level drop. Conodont biostratigraphy places these events within the lower part of the Gnathodus interregnum, correlating with the latest Tournaisian. These data, combined with insights from coeval sedimentary records within the Carnic Alps and from other basins worldwide, indicate that higher-frequency sea-level fluctuations, superimposed on an overall regressive trend, influenced the late Tournaisian evolution of the Carnic Basin.

The Carnic Alps represent the best exposed Paleozoic succession within the Alpine domain being fossiliferous, mostly non-metamorphic and largely complete. This study focuses on the area around Mt. Pizzul, because the bedrocks record well the basin dynamics and most of the units are conodont bearing. Our aims were to contribute to the procedure of formalization of the lithostratigraphic units and to understand the depositional and deformation history of the study area. The area has been mapped, tectonic overprint constrained and the successions described, measured and dated. As a second-order aim, we discuss these data to infer the relations with other parts of the Carnic basin and to recognize the global controls on sedimentation. The depositional evolution can be sketched as follows: pre-Hirnantian ramp-type margin; Hirnantian glacioeustatic-related deposits and unconformity; pelagic deposition in a ramp-type margin (Přidoli–Eifelian); slope formation and differentiation in buildup, foreslope and pelagic environments (Eifelian–Frasnian); transgression and reef drowning (Frasnian–Visean); probable subaerial exposures likely during in uppermost Famennian and Visean times; and turbidite deposition (Visean). Global controls or deposits suggesting a global control are documented, including the Boda Event, the Hirnantian glaciation, the Middle Devonian reef growth, the Kacak Event, and the high-frequency sea-level fluctuations around the Devonian–Carboniferous boundary. The drowning of the buildups here and elsewhere in the Carnic Alps started during the Frasnian, unlike observed globally. This suggests that local tectonics lead to progressive deepening up to the transition to turbidite deposition.

Proxy evidence from the Gartnerkofel-1 core (Carnic Alps, Austria) for hypoxic conditions in the western Tethys during the end-Permian mass-extinction event

An integrated approach of petrographic analysis, whole rock geochemistry and microprobe analysis has been applied to obtain information on the geodynamic development and the provenance for Ordovician to Permian siliciclastic successions exposed within the Carnic Alps (Austria). Sandstone detrital mode and geochemical results refine previous geodynamic interpretations. Late Ordovician samples indicate a stable craton and recycled orogenic and, possible, extensional setting. The Early Carboniferous is interpreted to represent a compressional environment, followed by a Late Carboniferous molasse-type foreland basin, and a Permian extensional geodynamic setting. Contrasting geochemical patterns of post-Variscan and Permian sequences suggest a rift setting. Electron microprobe data of detrital white mica also indicate changes in the provenance. Compositional data reflect a shift from low- to medium-grade metamorphic (Ordovician) to high-grade metamorphic (Carboniferous) to low- to medium-grade metamorphic and plutonic source rocks (Permian). Additionally, our data show that various chemical discrimination diagrams do not include all possible ranges of sandstones, and that high contents of detrital mica and ultra-stable heavy minerals may cause misclassification. Consequently, we propose the use of multi-method approach for provenance studies, including the control of geochemical data by modal analysis and heavy mineral investigations.