Middle devonian-lower frasnian natural hydrocarbon reservoirs of the Pechora Sea shelf and Timan-Pechora oil and gas province adjacent area

The research is based on the three-layer natural hydrocarbon reservoirs theory, which allocates 3 layers in a natural reservoir – the genuine seal, the productive part and the intermediate layer situated between them - the false seal. The Middle Ordovician-Lower Frasnian terrigenous complex variable in thickness, composition and stratigraphic completeness sub-regional natural reservoir was identified in the northern part of the Timan-Pechora oil and gas province adjacent to the Pechora Sea. It includes several zonal and local natural reservoirs (Middle Ordovician-Lower Devonian, Middle Ordovician-Eiffelian, Zhivetian-Lower Frasnian and others). The distribution areas of these natural reservoirs were extrapolated to the Pechora Sea offshore. The areas with the highest prospects of oil and gas potential of the Pechora Sea offshore were delineated, basing on the Timan-Pechora oil and gas potential analysis. These are the northwest extensions into the Pechora Sea of the Denisov trough, the Kolva megaswell, as well as the Varandei-Adzva structural zone and the Karotaiha depression. Keywords: natural reservoir; genuine seal; false seal; field; pool; hydrocarbons.

Stratigraphical reinterpretation of Devonian strata underlying the Mons Basin based on cuttings from the Saint-Ghislain borehole, Hainaut, Belgium

It is revealed that the lowest 1010 m of the Saint-Ghislain borehole (-4393 to -5403 m), of which cuttings are available, constitutes a crucial source of information to investigate, amongst others, the deep geothermal potential within the Brabant Parautochthon, underlying the Mons Basin, Hainaut. The lithological succession of this interval was reconstructed based mainly on visual analysis and calcimetry of 852 cutting samples as well as four cored sections. Additionally, palynological, magnetic susceptibility and X-ray diffraction analyses were conducted in order to complement the dataset. The lower section of the investigated borehole sequence mainly consists of grey calcareous shale while the middle section is dominated by blue-grey shaly limestone and the upper section is mainly composed of green shale. Palynomorphs found at -5261 m suggest a latest Givetian–Early Frasnian age. A new lithostratigraphical interpretation of the deepest part of the Saint-Ghislain borehole is proposed. The lower calcareous shale from ‑5403 to ‑5100 m is interpreted as the Bovesse Formation (Lower Frasnian) and at its base possibly uppermost Givetian. The overlying limestones from -5100 to -4790 m can be attributed to the Rhisnes Formation (Upper Frasnian), and the green shale between ca. -4393 and -4790 m, to the Bois de la Rocq Member (Famennian). These results open new insights regarding the geological interpretation of the basement underlying the Mons Basin. They also present a promising approach and example regarding interpretations based on cuttings.

Neosyringaxon Jia in Jia et al., 1977 (Anthozoa, Rugosa) in the Middle and Late Devonian of Europe and North America

The new species Neosyringaxon michelini is described from the lower Frasnian of Ferques near Boulogne-sur-Mer in northern France. The genus (family Petraiidae) was only known from the lower Givetian of southern China. Further species were found by revision of older literature data: Zaphrentis polonica Sobolev, 1904 from the lower Givetian of Skały, Holy Cross Mountains, Poland (meanwhile assigned to Stewartophyllum, Adradosia) and Syringaxon independense Stainbrook, 1946 and Syringaxon calvini Stainbrook, 1946, from the Frasnian Independence Shale of Iowa, USA are now transferred to Neosyringaxon. Such a disjunctive record occurs often in Cyathaxoniid assemblages of ahermatypic Rugosa and suggests a perhaps nearly cosmopolitan distribution.

Rare Middle and Upper Devonian dalmanelloid (Orthida) of the Cantabrian Mountains, N Spain

Rare Cantabrian Dalmanellidae (Costisorthis lisae nov. sp.), Dicoelosiidae (Teichertina cf. peregrina, T. cf. ?tzroyensis), and Mystrophoridae (Mystrophora sp., Biernatium sucoi nov. sp., and Biernatium sp. 2) are described and ?gured for the ? rst time in Spain. Most of them are scarce forms that occur only in certain localities. All the species but one came from the lower part of the Portilla (province of León) and Candás (province of Asturias) formations, Faunal Interval 21, Polygnathus rhenanus/P. varcus conodont zone, middle Givetian. The exception is Biernatium sp. 2 that occurs in Asturias in FI 25, Piñeres Fm., Palmatolepis transitans zone, lower Frasnian. Costisorthis ranges from Pragian to Eifelian rocks in central Europe. C. lisae nov. sp., from the Givetian of Asturias di?ers from other Costisorthis species in the weaker development of the distinctive ventral and dorsal plications.

Representatives of the family Actinostromatidae (Stromatoporoidea) in the Devonian of southern Poland and their ecological significance

Stromatoporoids of the family Actinostromatidae are common constituents of Givetian to Frasnian (Devonian) organic buildups. The species-level structure of actinostromatid assemblages from the Devonian of southern Poland is described in the present paper, with special emphasis on ecological factors that influenced species composition of the communities. Nine species of the genera Actinostroma and Bifariostroma are distinguished. Members of the family Actinostromatidae predominated in stromatoporoid assemblages within lower Frasnian carbonate buildup margins. The most diverse actinostromatid faunas were found within the middle Givetian Stringocephalus Bank, in the upper Givetian-lower Frasnian biostromal complex and in the lower Frasnian organic buildups. Species-level biodiversity was lowest within detrital facies which surrounded the Frasnian carbonate buildups. Species of Actinostroma with well-developed colliculi are commonest within the middle Givetian to early Frasnian coral-stromatoporoid biostromal complexes, whereas species with strongly reduced colliculi predominate early-middle Frasnian organic buildups. The skeletal structure of actinostromatids reflects environmental changes, documenting a transition from species with thin, close-set pillars and widely spaced laminae (common in the middle Givetian) to those with long, thick pillars and megapillars (in Bifariostroma), which were predominant during the early and middle Frasnian. The distribution of growth forms among species reveals a significant intraspecific variation. Species of Actinostroma can be either tabular or low domical, depending on the palaeoenvironmental setting. Thus, the present study confirms that stromatoporoid morphology was influenced by environmental conditions.

Brachiopods and stratigraphy of the Upper Devonian (Frasnian) succession of the Radlin Syncline (Holy Cross Mountains, Poland)

The lower part of the Frasnian succession in the Radlin Syncline (Kielce–Łagów Synclinorium, southern region of the Holy Cross Mountains), in the two studied successions: Józefka at Górno and (for the first time) Radlin, consists of the rhythmic marly Szydłówek Beds, the fossil-rich limestones of the Wietrznia Beds (locally) and the atypically developed, calcareous Kostomłoty Beds. The carbon isotope chemostratigraphic pattern overall corresponds well to the global Early–Middle Frasnian biogeochemical perturbation, even if the majorpunctatapositive excursion is only fragmentarily recorded in the Kostomłoty intrashelf basin.Two brachiopod assemblages are abundantly represented in both sections: thePhlogoiderhynchus polonicusAssemblage, typical of the Szydłówek Beds, and theBiernatella lentiformisAssemblage, limited to the middle part of the Wietrznia Beds. Both are highly dominated by the index species. Twenty nine lower Frasnian brachiopod species (Craniida – 1 species, Strophomenida – 1, Productida – 2, Protorthida – 1, Orthida – 5, Pentamerida – 1, Rhynchonellida – 4, Atrypida – 4, Athyridida – 3, Spiriferida – 4, Spiriferinida – 3) are described from the Szydłówek and Wietrznia Beds. Seven new species are introduced:Skenidioides cretusHalamski sp. nov.,Biernatium minusBaliński sp. nov.,Monelasmina montisjosephiBaliński sp. nov.,Atryparia(Costatrypa)agricolaeHalamski and Baliński sp. nov.,Davidsonia enmerkarisHalamski sp. nov.,Leptathyris gornensisBaliński sp. nov., andEchinocoelia parvaBaliński sp. nov.Davidsonia enmerkarisHalamski sp. nov. is intermediate betweenDavidsoniaBouchard-Chantereaux, 1849 andRugodavidsoniaCopper, 1996 and is the youngest known representative of the suborder Davidsonioidea Copper, 1996.Skenidioides cretusHalamski sp. nov. is the last representative of the genus. Statistical investigation of a large sample ofSpinatrypina(Exatrypa)explanatadid not confirm the existence of two dimorphic forms, coarse- and fine-ribbed.The high-diversityBiernatella lentiformisAssemblage is quite dissimilar to coeval brachiopod assemblages described heretofore from the Holy Cross Mountains region. It is interpreted as consisting of mostly parautochthonous dwellers of deep-slope muddy habitats and a local, occasionally storm-agitated, intra-basin brachiopod-crinoid-coral shoal. The fauna was adapted probably to cooler and nutrient-poor waters during an initial phase of the severe carbon cycle perturbation.