The schulterkofel section in the Carnic Alps,Austria: Implications for the carboniferous-permian boundary

Summary The upper part of the LowerPseudoschwagerina Limestone (Rattendorf Group), outcropping on the northwestern flank of Schulterkofel Mountain, Carnic Alps (Austria) is described with special emphasis on fusulinid microfossils and facies. This fusulinid-rich section offers an ideal opportunity for biostratigraphy in defining the Permo-Carboniferous boundary in this region. The LowerPseudoschwagerina Limestone is composed of shallow-marine limestones with intercalated thin siltstone and sandstone beds. Fusulinid limestones are represented by two types of wackestones, both containing large quantities of smaller foraminifers. Fusulinid grainstones are rare. Limestones rich in fusulinids were found only within the bedded limestone facies in beds both below and especially above siliciclastic intercalations. This may indicate that the best living conditions for fusulinids existed immediately before and especially after the climax of a regressive phase (sea-level lowstand). The fusulinid limestones were deposited within a protected, shallow-marine shelf environment with normal salinity. Pseudoschwagerinid fusulinids appear in the upper part of the LowerPseudoschwagerina Limestone, in samples SK 107d (undeterminable species) and SK 108, i.e. between 92 m and 93 m above the base of the section within a bedded limestone immediately above the uppermost clastic intercalation. The fusulinid fauna is represented by about 30 species belonging to only a few genera. Species ofTriticites andRugosofusulina dominate, whereas those ofDaixina, Rugosochusenella andPseudofusulina are rare. A characteristic feature of the fauna is the strong similarity with fusulinid faunas described from Russia as well as from Middle and East Asia. Some of the described fusulinids are new for the Carnic Alps. The first appearance ofPseudoschwagerina andOccidentoschwagerina (Occidentoschwagerina alpina Zone) in the upper part of the LowerPseudoschwagerina Limestone in the Schulterkofel section defines the position of the Carboniferous-Permian boundary.     

Anthracoporella mounds in the Late Carboniferous Auernig Group,Carnic Alps (Austria)

Summary A heretofore undocumented example of skeletal mounds formed by the dasycladacean algaAnthracoporella spectabilis is described from mixed carbonate-clastic cycles (Auernig cyclothems) of the Late Carboniferous (Gzhelian) Auernig Group of the central Carnic Alps in southern Austria. The massive mound facies forms biostromal reef mounds that are up to several m thick and extend laterally over more than 100 m. The mound facies is developed in the middle of bedded limestones, which are up to 16 m thick. These limestones formed during relative sea-level highstands when clastic influx was near zero. The mound facies is characterized by well developed baffler and binder guilds and does not show any horizontal or vertical zonation. Within the massive mound faciesAnthracoporella is frequently found in growth position forming bafflestones and wackestones composed of abundantAnthracoporella skeletons which toppled in situ or drifted slightly.Anthracoporella grew in such profusion that it dominated the available sea bottom living space, forming ‘algal meadows’ which acted as efficient sediment producers and bafflers. BecauseAnthracoporella could not provide a substantial reef framework, and could not withstand high water turbulence, the biostromal skeletal mounds accumulated in shallow, quiet water below the active wave base in water depths less than 30 m. The massive mound facies is under- and overlain by, and laterally grades into bedded, fossiliferous limestones of the intermound facies, composed mainly of different types of wackestones and packstones. Individual beds containAnthracoporella andArchaeolithophyllum missouriense in growth position, forming “micromounds’. Two stages of mound formation are recognized: (1) the stabilization stage when bioclastic wackestones accumulated, and (2) the skeletal mound stage when the sea-bottom was colonized byAnthracoporella and other members of the baffler and binder guilds, formingAnthracoporella bafflestones and wackestones of the mound facies. A slight drop in sea-level led to the termination of the mound growth and accumulation of organic debris, particularly calcareous algae, fusulinids, crinoids and bryozoans, forming well bedded limestones, which overlie the mound facies     

Biostratigraphical correlation of late carboniferous (Kasimovian) sections in the Carnic Alps (Austria/Italy): Integrated paleontological data, facies, and discussion

Summary The fusulinacean faunal content of the Bombaso Fm. and lower part of the Auernig Group (Carnic Alps, Austria/Italy) is reviewed and completed by data on conodonts and algae. Four different faunal associations can be distinguished within this stratigraphic interval. The beginning of the postvariscan sedimentation in the investigated sections is diachronous, shifting in age from early Kasimovian (Krevyakinian) at Zollner Lake and Mt. Auernig, early to middle Kasimovian at Cima Val di Puartis to late Kasimovian (Dorogomilovian) at Mt. Ro?kofel. The sections analyzed consist of shallow-marine sediments, which differ in microfacies of limestones and partly in biotic assemblages. They are geographically isolated and could not be traced laterally for lithologic correlation in the field. The biostratigraphic correlation with the faunas of the stratotype sections in the Moscow Basin is hindered by the searceness of fusulinaceans in the critical levels, especially in the lowermost Kasimovian, and differences in the species composition. A biostratigraphic correlation of the Bombaso Fm. and basal part of the Auernig Group with the Peski Fm. (Myachkovian) of the Moscow Basin, as suggested byDavydov & Krainer (1999), is not confirmed by our results. Due to our taxonomic reinterpretation of the oldest fauna (Protriticites aff.permirus with distinct mural pores and largeBeedeina (Pseudotriticites) asiaticus) a lowermost Kasimovian (Lower Krevyakinian) age is more probable. This correlation is supported by the co-occurring conodont fauna, which is suggested to belong to the zone of “Streptognathodus subexcelsus”. This biozone reaches from the topmost Peski Fm. to the Suvorovo Fm. (Lower Krevyakinian) in the Moscow Basin, and may be correlated with the uppermost Desmoinesian of the Midcontinent North America. Fusulinaceans and conodonts of the overlying strata at Zollner Lake and from the sections at Cima Val di Puartis and Mt. Auernig most probably correspond to the upper Krevyakinian/lowermost Khamovnikian of the Russian platform (Lower Missourian of the Midcontinent North America). The algal associations (Dvinella, Beresella, Herakella) from these lowermost strata are unique for the Carnic Alps. Their stratigraphic range points to Moscovian-Kasimovian as well, and fits with the fusulinacean and conodont data. Sediments of the N?lbling Group (=“untere kalkreiche Schichtgruppe”) have their correlative levels in the upper Khamovnikian, but reach higher into the Dorogomilovian. More reliable correlations are possible with the fusulinacean faunas of the Cantabrian Mts. and Central Asia, based on the coincidence of several species. A revised biostratigraphic correlation with the different remote basins of the Paleotethyan realm and the Russian Platform is given, based on own data and recent results by the members of the SCCS Working group to define a GSSP close to the Moscovian/Kasimovian boundary. The sequence-stratigraphic scheme, the systematics, and the biostratigraphic correlation ofDavydov & Krainer (1999) are discussed.     

An updated Telychian (Late Llandovery, Silurian) conodont zonation based on Baltic faunas

Five conodont zones, Pterospathodus eopennatus ssp. n. 1, P. eopennatus ssp. n. 2, P. amorphognathoides angulatus , P. a. lennarti and P. a. lithuanicus , are described in the interval previously known as the P. celloni Zone. The new zones are grouped into two superzones: the first two form the P. eopennatus Superzone and the other three the P. celloni Superzone. All zones correspond to the intervals of the total ranges of the nominal taxa and to the boundaries between the zones to the levels at which one taxon was evolutionally replaced by another. The lower boundary of the P. a. amorphognathoides Zone is redefined. The P. eopennatus ssp. n. 2, P. a. angulatus and P. a. amorphognathoides zones are further subdivided into the Lower and Upper subzones. Although the zones described are mainly based on data from Estonia, they can be recognized all over the world, in most sections containing Telychian strata and from where adequate data are available. Most of the subzones can so far be applied only in a limited area.     

Pattern of conodont reworking in the Upper Devonian of the Alps: palaeoenvironmental and palaeotectonic implications

Transfer of sediments from shallow shelf to basin usually implies vertical (stratigraphic) reworking of fossils, but in a few instances produces only lateral reworking (actually within the time span of a subzone). An Upper Devonian (Frasnian) pelagic carbonate sequence with allodapic intercalations and thick intraclast parabreccias triggered by seismic shocks and related tsunami and turbidity currents has been studied. Here, the standard biozone sequence is undisturbed at the zonal as well as the subzonal level. However, distribution of conodonts is discontinuous, and ranges of some important species are altered; mature specimens are commonly broken, whereas complete specimens are mostly juvenile forms. Maxima and minima of element frequency and anomalous thickening or thinning of subzones are recognized. Such distribution patterns of conodonts are compared with the four main facies distinguished and related to the environmental interpretation (a platform-basin system, the original gentle slope of which was fragmenting in fault-controlled blocks). The mean frequency of shallow-water, proximal conodonts is 10% whereas transitional to distal deeper-water genera dominate throughout the entire section. In the dominant biofacies, conodonts settled vertically, in the subordinate one they were transported laterally. The 'intraclast parabreccia' is interpreted as a peculiar type of seismitc. The anomalous thickness variation of biozones is related to the step topography of the slope in a fault-controlled carbonate basin.     

A close look at late carboniferous algal mounds: Schulterkofel,Carnic Alps,Austria

Summary During the uppermost Carboniferous and lowermost Permian algal mounds were formed in inner shelf settings of the Carnic Alps (Austria/Italy). A specific mound type, characterized by the dominance of the dasyclad green alga Anthracoporella was studied in detail with regard to geometry, relationship between mound and intermound rocks, composition of the sediment, biota and diagenetic criteria. The two meter-sized mounds studied, occur within depositional sequences of transgressive systems tracts in the Lower Pseudoschwagerina Limestones (uppermost Gzhelian) at the flank of the Schulterkofel. The mounds consist of an Anthracoporella core facies with a spongecrust boundstone facies at the base and at the top. The massive limestones of the Anthracoporella core facies exhibit abundant algal tufts and bushes, frequently in life position. The limestones of the intermound facies represented by thin-bedded bioclastic wackestones and packstones with abundant phylloid algae underlie and overlie the mounds. Intercalations of intermound beds within the mound facies indicate sporadic disruption of mound growth. Onlapping of intermound beds on steep mound flanks indicate rapid stabilization and lithification of mound flanks and the existence of a positive paleorelief. Asymmetrical shape of the mounds may be current controlled. Mound and intermound biota differ in the prevailing algae but are relatively similar with regard to associated foraminifera. Conspicuous differences concern bioerosion and biogenic encrustations. Bothare, high in intermound areas but low in the Anthracoporella core facies. The mounds show no ecological zonation. The mounds grew by in-place accumulation of disintegrated algal material and trapped bioclastic material between erect algal thalli. The comparison of the various Anthracoporella mounds demonstrates that almost each mound had ist own history. Establishing a general model for these mounds is a hazardous venture.     

Middle Triassic basin evolution and stratigraphy in the Carnic Alps (Austria)

Summary A local intraplatform basin developed in the Gartnerkofel-Zielkofel area of the Carnic Alps (southern Carinthia, Austria) during the Middle Triassic (Ladinian). This basin was filled with a transgressive basinal sequence composed of the Uggowitz Formation and overlying Buchenstein Formation. At the northwestern slope of the Gartnerkofel, the platform carbonates of the Schlern Dolomite interfinger with the Buchenstein Formation, causing the formation of two depositional sequences. The Uggowitz Formation consists of the Uggowitz Breccia and the Kühweg Member. Sediments of the Uggowitz Breccia were formed by different types of gravity induced processes. The Kühweg Member is a thin sequence of silt-and fine-grained sandstones which were deposited in a slope to basin margin environment by turbidity currents. The overlying Buchenstein Formation consists of hemipelagic to pelagic limestones of Fassanian age with intercalated pyroclastic rocks (Pietra verde). Nodular limestones were deposited under slow rates of accumulation during a relative sea-level highstand. The uppermost Buchenstein Formation is composed of hemipelagic limestone beds with intercalated graded calcarenites and breccias of platform-derived debris, showing characteristics features of a fore-reef slope of the prograding Schlern Dolomite. Uggowitz Formation and basal Buchenstein Formation are interpreted as a transgressive systems tract, nodular limestones from the middle part of the Buchenstein Formation mark an early highstand systems tract, forereef slope sediments of the upper Buchenstein Formation formed during the beginning regression of a late highstand systems tract, the basal part of the overlying Schlern Dolomite probably reflects a lowstand systems tract. The intercalated bedded limestone facies within the Schlern Dolomite is characterized by large, platform derived blocks, slump structures, breccia beds, graded calcarenites and hemipelagic limestones indicating a forereef slope environent. This intercalated facies belongs to the Buchenstein Formation and interfingers with the Schlern Dolomite. Conodonts from this intercalated slope facies point to Late Fassanian age. Therefore, the two Middle Triassic depositional sequences of the Gartnerkofel area can be correlated with the depositional sequences ‘Ladinian 1’ and ‘Ladinian 2’ of the Dolomites, proposed byDe Zanche et al. (1993). A brief comparison with the basinal sequences of similar age of the karawanken Mountains and the Carnia is presented.     

A three- and two-dimensional documentation of structural elements in schwagerinids (superfamily Fusulinoidea) exemplified by silicified material from the Upper Carboniferous of the Carnic Alps (Austria/Italy): a comparison with verbeekinoideans and alveolinids

Silicified schwagerinids (superfamily Fusulinoidea v. Moeller 1878) from the Upper Carboniferous (Carnic Alps, Austria and Italy) were isolated from cemented carbonate rocks using hydrochloric acid. The shells show details of the wall texture and of internal structures in three dimensions which are illustrated with SEM pictures. Thin sections from hand specimens provided two-dimensional sections of the shell for comparison. The functional significance of fusulinoidean internal structures is discussed and compared with verbeekinoideans and alveolinids. Particular attention is paid on the disposition of the different openings within the shell and from the chamber lumen to the outside which reflects the direction of protoplasmic flow. Based on the knowledge of the nature of protoplasm ultrastructure in Recent foraminifera and its biological significance we draw some conclusions about the nature of protoplasm in fusulinoideans and its change within the Permian verbeekinoideans.     

Eurytholia plates (Problematica) from the late Silurian of the Austrian Carnic Alps

A small fauna of phosphatic plates of the enigmatic organism Eurytholia bohemica [Ferretti A., Serpagli E., ?torch P., 2006. Problematic phosphatic plates from the Silurian-Early Devonian of Bohemia, Czech Republic. Journal of Paleontology 80 1026–1031.], is described for the first time from upper Silurian beds of Austria. Other known Silurian occurrences of this taxon were restricted to Bohemian localities even if the genus had been previously reported from several Ordovician outcrops. The extension of E. bohemica from the microcontinent of Perunica to that of Carnica suggests that Eurytholia was not an uncommon constituent of Silurian fauna, at least at intermediate latitudes in the southern hemisphere.     

Late Devonian - Early Carboniferous vertebrate microremains from the Carnic Alps, northern Italy

Vertebrate microremains from the Late Devonian-Early Carboniferous of the Carnic Alps are predominantly chondrichthyan, with minor placoderm and actinopterygian remains. The faunas are sparse and, with very few exceptions, occur only in conodont-rich pelagic limestones (Pramosio Limestone) representative of the palmatolepid-bispathodid conodont biofacies. Phoebodont and jalodont chondrichthyans, also reflecting open-ocean environments, predominated during the Famennian, and eventually symmoriids seem to predominate during the Early Carboniferous. The presence of Siamodus in this assemblage gives a new locality for this genus known from few regions in the world and allows confirming its stratigraphical range (limpidus Zone) and its relation to deep-water environments. The Late Devonian vertebrate faunas are tropical and cosmopolitan, having much in common with coeval taxa from the North-Gondwanan margins and Asian terranes. Composition of the vertebrate faunas is consistent with the Carnic Alps terrane having occupied a position intermediate between Gondwana and Laurussia, as hypothesized by various authors, but because of sparsity of the taxa represented and the pronounced cosmopolitan nature of both the conodont and vertebrate faunas, the data are not compelling.     

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

A rare occurrence of Phragmoceras imbricatum Barrande is recorded from moderately shallow marine Silurian sequences in the Carnic Alps (Austria). The specimen was collected from a condensed series of nautiloid-bearing wackestones/packstones which are documented as being one of the earliest levels of the Silurian Cephalopod Limestone Biofacies deposited along the North Gondwana margin. The presence of this genus and particular species in the Alpine area, whether as an in situ fauna or as a “stray immigrant”, during a period of global eustatic lowstand, adds new data with regard to the mechanisms of faunal exchange of nectobenthic nautiloid taxa between the Carnic Alps, the Prague Basin, SW Sardinia, Avalonia and Baltica which must have been made possible by currents connecting all five areas. It seems likely that some of the nautiloid taxa appearing in the Prague Basin during the Ludlow may have already been present in the Carnic Alps much earlier in the Silurian; these document early faunal affinities with Baltica. As well as confirming the existence of open migrational seaways between these terranes at a precise stratigraphic interval during the Silurian (lower Homerian: Wenlock), the presence of this species also indicates a prevailing more temperate paleoenvironment in these areas which this element of a usually tropical fauna could tolerate, and provides significant evidence that warm water currents reached the Carnic Alps at this time. In addition due to the bathymetric restrictions of the shells of these particular faunas, exchange by currents could not have taken place over great distances, even considering drifted individuals, and therefore indicates the relatively close positions/connections of various peri-Gondwana Terranes such as the Carnic Alps, SW Sardinia and the Prague Basin to Avalonia and Baltica during this time slice.     

First documentation of Llandovery (Silurian) conodont genus Astropentagnathus in China (Langao,Shaanxi Province) and the age of Baiyaya Formation

Age of the Baiyaya Formation in the Ziyang-Langao region of Shaanxi Province remains debatable. Ten samples were taken for conodont biostratigraphical studies from the Tianwancun section. The first discovery of Astropentagnathus in China indicates that the genus has a wider geographical distribution than previously known. Conodont fauna from the Baiyaya Formation suggests that the lower part of the unit corresponds to the Pterospathodus eopennatus Superbiozone, and its upper part to the lower Wenlock (probably mainly to the Kockelella ranuliformis Superbiozone). Diachroneity of the Baiyaya Formation in the region is confirmed by conodont studies from the Tianwancun and Qiaoxi sections. Further studies are required to find out age-variation of the formation more precisely.     

Conodont biostratigraphy of the Upper Devonian-Lower Carboniferous Shahmirzad section, central Alborz, Iran

The conodont fauna from the Devonian-Carboniferous Shahmirzad section, located in the Central Alborz Mountains (North Iran), have been studied mainly for biostratigraphic purposes. Some levels were barren of conodonts, whereas others yielded a not very abundant, but quite differentiated fauna. No conodonts have been found from the mainly terrigenous and shaly Geirud Formation, whereas representative of genera Bispathodus, Clydagnathus, Gnathodus, Hindeodus, Mehlina, Polygnathus, Protognathodus, Pseudopolygnathus and Siphonodella have been collected from the mainly calcareous overlaying Mobarak Formation. The fauna allowed to discriminate five biointervals, from the sulcata Zone to a “Lower typicus - anchoralis-latus interval” in the central part of the section, while the lower and upper parts cannot be zoned on the basis of conodonts. This paper is the first report on lowermost Carboniferous conodonts from the Mobarak Formation in central Alborz.     

Taphonomy of Early Permian benthic assemblages (Carnic Alps, Austria): carbonate dissolution versus biogenic carbonate precipitation

During the Early Permian, in the area of the Carnic Alps, a quartz-gravelly beach fringed a mixed siliciclastic-carbonate lagoon with fleshy algal meadows and oncoids; seaward, an ooid shoal belt graded down dip to a low-energy carbonate inner shelf with phylloid algal meadows. In limestones, foraminiferal biomurae and bioclast preservation record tapholoss by rotting of non-calcified organisms (interpreted as fleshy algae) and by dissolution of aragonitic fossils. Carbonate loss by dissolution was counteracted and, locally, perhaps exceeded by carbonate precipitation of encrusting foraminifera and as oncoids. Sites of abrasion and carbonate dissolution (beach), sites with tapholoss by rotting and dissolution, but with microbialite/foraminiferal carbonate precipitation (lagoon, inner shelf), and sites only of carbonate precipitation (ooid shoals) co-existed on discrete shelf compartments. Compartmentalized, contemporaneous carbonate dissolution and precipitation, to total amounts yet difficult to quantify, impede straightforward estimates of ancient carbonate sediment budget.     

Silurian to Mississippian series of the eastern Catalan Pyrenees (Spain), updated by conodonts, foraminifers and algae

Stratigraphic sections and microfossils samples from the upper part of the “Graptolitic Shales-Orthoceras Limestones” and from the Camprodon Formation lying in the area of Camprodon, eastern Pyrenees, Spain, have been studied. Some beds at the top of the “Graptolitic Shales-Orthoceras Limestones” correspond to the Torres Member of the Rueda Formation, and conodont faunas, indicating a Lochkovian age, are described. The Camprodon Fm. is interpreted to be turbidites deposited in deep sea fans, although slope deposits prevail in the eastern sections. One reworked carbonate clast from the Camprodon Fm. provided a valuable early Ludlow conodont fauna, from the Kockelella crassa Zone, reported for the first time in the Iberian Peninsula. Late Devonian conodonts and late Visean (Asbian-Brigantian) foraminifers and algae were also obtained from reworked limestone clasts, and latest Visean or Serpukhovian foraminifers from the sandstone matrix in the Camprodon Fm. The studied microfossils suggest a late Mississippian age for the Camprodon Fm. instead of the previously assigned late Silurian-Lochkovian age. This age must be considered when discussing the distribution of the Culm Facies in the Pyrenees and the significance of the contact between the Camprodon Fm. and the underlying “Graptolitic Shales”.     

The Pragian-Emsian conodont successions of the Barrandian area: search of an alternative to the GSSP polygnathid-based correlation concept

Six Pragian-Emsian boundary sections in the Barrandian area, western of Prague, provided evidence of well detectable entries of Latericriodus fauna probably at the earliest Emsian beds (particularly Latericriodus bilatericrescens gracilis Bultynck). The chance to find icriodontid conodonts increases with latest part of Praha Fm., which is apparently of Emsian age, whereas polygnathids are sparsely preserved to absent. The high icriodontid/polygnathid ratio links together all these Barrandian sections, although their open-sea depositional environments range widely from deep troughs with rapid calciturbidite accumulation (Pod Barrandovem section) to relatively starving slope environments on elevations (Na Po?árech sections). The reports on polygnathid occurrences around the Pragian-Emsian boundary beds of the Barrandian area are much biased by poor reproducibility of the results (the conodonts cannot be found again) as well as by different levels where they were randomly found and/or by major taxonomic problems with the “kitabicus” and “dehiscens” definitions and their stratigraphic use. Apart from the GSSP in the Zinzilban Gorge (Uzbekistan) and its “kitabicus” boundary, the newly introduced “gracilis” biostratigraphic-marker concept preserves the major volume of the Pragian and respects also approximately the base of the traditional Emsian. These “gracilis” entries are clustered around the dark-colored “graptolite-bearing interval” beds, which largely form a prominent lithological marker within the latest, light gray-colored Dvorce-Prokop Limestone of the Barrandian area. This “gracilis” biostratigraphic marker has a promising correlation potential relative to Spanish and Moroccan sections.     

Age of the Silurian Wuxiahe Formation in Langao,Northwest China: New conodont data

A recent study of conodonts from the Wuxiahe Formation (lower to middle part) in the Ziyang-Langao region suggested its age of middle Telychian (Llandovery) to lower Sheinwoodian (Wenlock), contradicted by subsequent graptolite studies indicating an age of late Telychian for the same interval. New samples from the Qiaoxi section for conodonts to re-access the age of the Wuxiahe Formation collected in this study show that the lower to middle part of the formation belongs to the Pterospathodus amorphognathoides amorphognathoides Biozone, suggesting the age of late Telychian; thus, the Llandovery–Wenlock boundary in the section is most probably higher than previously estimated, but its precise position is not determined since the identification of the Wenlock graptolite Cyrtograptus cf. lundgreni in the section is to be further confirmed. Based on the conodont faunas recognized in the Qiaoxi and Tianwancun sections, the base of the Wuxiahe Formation in the Ziyang-Langao region is diachronous, i.e., not higher than the upper Telychian Pterospathodus amorphognathoides amorphognathoides Biozone at Qiaoxi, but not lower than the lower Sheinwoodian Kockelella ranuliformis Biozone at the Tianwancun setion.     

High-resolution biostratigraphy of the Tournaisian-Visean (Carboniferous) boundary interval, Mokrá quarry, Czech Republic

This paper summarizes the results of investigations carried out in the Mokrá quarry since 2006 on the biostratigraphy of the Tournaisian-Visean (T-V) boundary interval. It also integrates previous results obtained by J. Kalvoda and collaborators. The main focus is on the boundary itself, but stratigraphically lower and higher levels have been investigated as well to provide a biostratigraphical context spanning the late Tournaisian to early Visean. This stratigraphical level has been the focus of intense international research in the recent years under the auspices of the Subcommission on Carboniferous Stratigraphy (SCCS) in order to find a new criterion and reference section (Global Stratotype Section and Point, GSSP) for the base of the Visean Stage. The appearance of Eoparastaffella simplex from its ancestor E. “ovalis” and the Pengchong section (Guangxi, southern China) have recently been proposed by the Task Group on the Tournaisian-Visean Boundary and ratified by the SCCS as the new biostratigraphic criterion and GSSP for the base of the Visean, respectively. The sequence exposed in Mokrá is not suitable as a GSSP, notably because it is an active quarry, but it contains most of the foraminifer and conodont guides allowing a high-resolution biostratigraphy of the boundary interval. In addition, it contains abundant trilobites. For these reasons, it constitutes one of the best sections across the T-V boundary in Europe and can serve as a useful additional reference.     

Middle Telychian (upper Llandovery, Silurian) graptolites from boreholes of northwestern Libya: Their biostratigraphic significance and palaeogeographical implication

A low-diversity but stratigraphically and palaeobiogeographically important graptoloid association comprising Metaclimacograptus flamandi (Legrand), Parapetalolithus meridionalis (Legrand), and Torquigraptus australis Štorch was identified in the core samples of wells A1-66, F1-66 and A1-43 in the Ghadamis Basin of Libya. The former two species have been originally recovered from Algeria. All three taxa are common and widespread in the middle Telychian strata of Spain (Central Iberian Zone and western Iberian Cordillera) and France (Brittany). In European sections, the species are associated with other, moderately diverse graptoloid fauna, which enables a more precise and worldwide biostratigraphic correlation of Saharan boreholes and surface sections. The present faunal association indicates a middle Telychian age (upper crispus, griestoniensis and lowermost crenulata/tullbergi biozones) for the strata and suggests palaeobiogeographical links between North African pericratonic basins and Ibero-Armorican shelves. M. flamandi has not been found outside this NW-Gondwanan realm.