New bryozoans (Bryozoa) from the Upper Devonian (Lower Famennian) of the Kuznetsk Basin

New bryozoans from the Upper Devonian (Famennian) of the borderlands of the Kuznetsk Coal Basin are described: Orthopora tomensis sp. nov. and Minussina incrustata sp. nov.     

Biostratigraphical value of some Strunian (Devonian, uppermost Famennian) Productidina, Rhynchonellida, Spiriferida, Spiriferinida brachiopods

The space of Devonian time considered in this paper corresponds to the uppermost part of the Famennian or the latest Famennian as a fourfold subdivision of the stage, usually called by many authors Strunian in neritic facies and Wocklumeria Stufe or Wocklumian in pelagic facies. Here, we examine the biostratigraphical value of certain brachiopod genera and species as bio-markers of the uppermost Famennian throughout the world (Europe, the former USSR, Middle East, Asia, North America, North Africa, and Australia). We have focused our study for species which stratigraphical range has been firmly established in correlation with the conodont biozones (Upper expansa, Early, Middle and Late praesulcata), the ammonoid biozones (do VI = “Wocklumeria Stufe”), or the foraminifera biozones (kobeitusana Zone). Other data for which the stratigraphical range is not based on standard biozonation are provided in the annex. The brachiopod bio-markers discussed in this paper belong to 14 Productidina genera (Acanthatia, Araksalosia, Ericiata, Hamlingella, Mesoplica, Nigerinoplica, Orbinaria, Ovatia, Rugauris, Semiproductus, Sentosia, Spinocarinifera, Steinhagella, Whidbornella), 7 Rhynchonellida genera (Araratella, Centrorhynchus, Hadyrhyncha, Megalopterorhynchus, Novaplatirostrum, Rozmanaria, Tchanakhtchirostrum), 13 Spiriferida genera (Brachythyris, Cyrtospirifer, Dichospirifer, Eochoristites, Imbrexia, Parallelora, Prospira, Rigauxia, Sphenospira, Tenisia, Toryniferella, Tylothyris, Voiseyella) and one Spiriferinida genus (Syringothyris). Other orders have not been studied in this paper. The main features of the uppermost Famennian brachiopod taxa represented in this paper are commented. All these taxa are listed as completely as possible throughout the world (with complements in the annex). A quick summary of the geographic distribution of the more represented taxa is given in conclusion.     

Famennian (Late Devonian) ammonoids from the Ouarourout section (Saoura Valley,Algeria)

In North Africa, the ammonoids constitute an important part of the Devonian marine macro-invertebrates. New material has been recently collected in the ‘Argiles de Marhouma’ Formation from several sections located near Béni-Abbès in the Saoura Valley (Ougarta Mountains, Algerian Sahara). Red nodular limestones (i.e., ‘griotte’ facies) characterize this formation rich in ammonoids. The assemblages from the Ouarourout section are composed of Goniatitida and Clymeniida constituting 30 species and 19 genera belonging to 11 families, with Cyrtoclymenia, Erfoudites, Kosmoclymenia, Planitornoceras, Platyclymenia, and Prionoceras, as the most abundant genera. The taxonomic comparison and the biostratigraphic correlations are made by considering the assemblages recorded in the Anti-Atlas of Morocco, which are very close to those observed in Algeria. In the Ouarourout area, the ‘Argiles de Marhouma’ Formation contains middle and late Famennian ammonoid assemblages and three biostratigraphic intervals can be identified: Planitornoceras, Platyclymenia and Medioclymenia.     

The Tournaisian (Early Carboniferous) of the Kahanag section (central Alborz; northern Iran); biostratigraphy with calcareous algae and foraminifers; palaeobiogeographic implications

The Tournaisian beds of the Kahanag section in central Alborz (northern Iran) are described. This Tournaisian is probably complete and continuous from MFZ1 to MFZ8 biozones; nevertheless, (1) the base is only lithostratigraphically characterized, (2) the biozones MFZ1 to MFZ5 cannot be differentiated, and (3) in topmost beds, Eoparastaffella simplex indicative of the basal Viséan have not yet found. This Tournaisian is subdivided into a local lower Tourmaisian (MFZ1-MFZ5) showing a poor assemblage of monolocular and bilocular foraminifers, and a local upper Tournaisian where the biozones MFZ 6 and 7 are precisely defined. In Kahanag, MFZ 6 is characterized by the FO of Eotextularia diversa; MFZ 7 is the range-zone of Darjella monilis; and the base of MFZ8 is marked by the appearance of Eoparastaffellina. The biozone MFZ 8 is particularly developed in Kahanag, and represents almost one third of the field-section; therefore, a local subdivision is proposed, especially in order to characterize an upper MFZ8 subbiozone. Additionally, some algae of the section are accurately described; especially a trio which might be characteristic of the latest Tournaisian in Iran, (1) the unilayered “Koninckopora” mentioned for the first time in Iran; (2) a new genus of dasycladaleans Kahanagella n. gen.; and (3) a new genus of palaeoberesellaceans, Oblikamaena n. gen. More classical Algospongia (incertae sedis algae) are briefly mentioned Issinella, Crassikamaena, Kamaena, Palaeoberesella, Exvotarisella, Pseudostacheoides, Sinustacheoides and Stacheoides. Regionally, the new genus Kahanagella might be an important palaeobiogeographic marker because it was also discovered in the Tabas Block, while it seems absent in the adjacent, well-known areas (Taurus, southern Urals, Kazakhstan). Perhaps, Kahanagella might permit to reconstruct the initial geography of the latest Tournaisian Iranian platforms. Oblikamaena elbursica n. gen. n. sp. is an endemic taxon for the moment but might become also palaeobiogeographically interesting. Finally, the whole foraminiferal and algal Tournaisian assemblage permits to propose a reconstruction of the initial palaeoposition of the Iranian terranes prior to the progressive assemby of the Cimmerian terranes.     

Compostional variations and patterns of condont reworking in Late Devonian and early carboniferous calciturbidites (Moravia, Czech Republic)

Summary Compositional variations and grain-size properties of both carbonate constituents and conodonts as an alternative component group were used for interpreting the processes governing the deposition of upper Famennian and middle Tournaisian calciturbidites in Moravia, Czech Republic. Both the composition and grain-size properties of conodont element associations showed to be markedly dependant on facies type of their host sediment. Upper Devonian calciturbidite successions deposited on flanks of wide, Moravian-Silesian carbonate platform are composed mainly of echinoderm-and peloid-rich wacke/packstones and intraclastic float/rudstones (fine-grained calciturbidites, “normal” calciturbidites with Tab Bouma sequences, debris-flow breccias) with abundance of shelf-and shelf margin conodont taxa and epipelagic and “mesopelagic” conodonts. Upper Devonian calciturbidites deposited on slopes of volcanic sea-mounts are composed of echinoderm-and peloid-rich wacke/packstones and float/rudstones with increased proportion of intraclasts and volcanigenic lithoclasts (fine-grained calciturbidites, normal calciturbidites), yeilding abundant conodont associations with higher proportion of “mesopelagic” taxa compared to the platform-flank examples. Middle Tournaisian calciturbidite succession composed of crinoid-, peloid-, intraclast-and lithoclast-rich lime mudstones, wacke/packstones and float/rudstones (normal calciturbidites and debris-flow breccias) yielded conodont element associations rich in shelt-and shelf-margin taxa, “mesopelagic” conodonts and reworked Middle-and Upper Devonian conodonts. In general, the ratio of shelf-and shelf margin conodont taxa to “mesopelagic” taxa is distinctly lower in finegrained calciturbidites than it is in normal calciturbidites and debris-flow breccias. Grain-size properties (mean grain size and sorting) and percentage of fragmented conodont elements, too, are markedly dependant on the facies type: in fine-grained calciturbidites the values of mean grain-size and fragmentation are low and the sorting is good to very good whereas in normal calciturbidites and debris-flow breccias the values of mean grain-size and fragmentation are distinctly higher and the sorting is poorer. The interdependence of facies type and composition and grain-size properties of conodont element associations in gravity-flow deposits is explained as resultant from hydrodynamic sorting during turbidity current flow and final deposition of the bed. Compositional variations observed in our sections may thus be attributed to facies variability (coarsening-and thickening-upward trends) rather than to sea-level fluctuations (highstand shedding of carbonate platforms). On the other hand, significant enrichment in reworked conodont taxa in middle Tournaisian normal calciturbidites compared to scarcity and/or absence of such conodonts in essentially identical facies of upper Famennian age indicate sea-level to be the major control governing such compositional variations, with low relative sea-level stand in middle Tournaisian and high relative sea-level stand in upper Famennian. Thorough analysis of conodont evolution, palaeoecology and taphonomy, with emphasis on understanding the processes of deposition of their host rock, are recommended for any biostratigraphic and biofacies study to be done in carbonate sediments deposited under strong hydrodynamic regimes, such as calciturbidites, temperstites, debris-flow deposits, shelf-edge oolitic sands, tidal-channel facies etc.     

The youngest African clymeniids (Ammonoidea, Late Devonian) – failed survivors of the Hangenberg Event

A co-occurrence of the clymeniid Postclymenia evoluta Schmidt, 1924 and the goniatite Acutimitoceras hilarum Korn, 2002 is reported from the Anti-Atlas of Morocco. Both species occur in the same limestone horizon within the Acutimitoceras prorsum Zone, that has yielded an exclusive conodont fauna of the Upper praesulcata Zone (latest Devonian, above the Hangenberg Black Shale). This record is firm evidence that some clymeniids survived the global Hangenberg Event, but soon later became extinct without descendants.     

The genus <Emphasis Type="Italic">Unispirifer</Emphasis> Campbell (Brachiopoda,Spiriferida) in the Early Carboniferous of the Moscow Syneclise

Two new species of the genus Unispirifer Campbell, U. semicircularis and U. parvus, are established as a result of a revision of Early Carboniferous spiriferids from the Moscow Syneclise. These forms have previously been described under Spirifer tornacensis Koninck, 1883 and S. taidonensis Tolmatschow, 1924.