Taxonomy and Evolution of Visean–Roadian (Late Mississippian–Guadalupian) Lasiodiscidae

ABSTRACT The study of the test morphology of type specimens and newly collected foraminiferal material of the family Lasiodiscidae Reitlinger, 1956, from the Carboniferous (Visean Stage, Mississippian Subsystem) to Permian (Roadian Stage, Guadalupian Series) beds of Russia (East European Platform and Urals), Turkey, and Tajikistan (Darvaz) allowed a revision of the species composition of the genera Howchinia, Monotaxinoides, Eolasiodiscus, Turrispiroides, and Mesolasiodiscus. A new genus, Postmonotaxinoides, is described. The species Monotaxinoides transitorius, M. subplanus, M. gracilis, Eolasiodiscus donbassicus, E. galinae, Mesolasiodiscus tenuis, M. nigrans, Postmonotaxinoides horridus, P. costiferus, and P. grandis are redescribed based on new data of their test morphology. Their taxonomy is revised and new phylogenetic reconstructions for the species are proposed.

Feature space of the Atasu type deposits (Сentral Kazakhstan)

Purpose. Studying geological formations of the Atasu type deposits to identify prospecting criteria. Methodology. Analysis of literature and fund materials, comparative analysis of geological factors characteristic of stratiform ores, stage formation and metamorphism. Findings. The main features characteristic of the deposits of the Atasu type have been formed: their belonging to the lower strata of the Upper Famennian, Upper Devonian to the Visean stage of the Lower Carboniferous; complex composition of ferromanganese and polymetallic ores formed in three hydrothermal stages (sedimentary, metasomatic and vein ones), stratiform, lenticular, localized near volcanic edifices. Originality. The main geological criteria have been established that determine the belonging of the Uspensky ore belt in Central Kazakhstan deposits to the stratiform deposits of the Atasu type formed at different depths in continental rift valleys. The criteria include the age interval of the formation of ore deposits of the stratiform type, hydrothermal staging of mineralization (sedimentary, metamorphic, metamorphic (hydrothermal, dislocation multistage and dynamothermal)); localization of folded and post-folded subvolcanic intrusions near former volcanic edifices. Practical value. The main prospecting geological criteria (features) established for the Atasu type deposits can be used to form a feature space for predicting the areas of mineral deposits localization of the Uspensky ore belt of Central Kazakhstan formed in close time periods, in similar geological-geochemical, thermodynamic and geodynamic conditions.

Belgian substages as a basis for an international chronostratigraphic division of the Tournaisian and Viséan

The Tournaisian and Viséan were formerly considered as series and in Belgium were divided into two (Hastarian and Ivorian) and three stages (Moliniacian, Livian and Warnantian), which are now considered as substages. The Belgian substages are based on conodonts and foraminifers, and incidentally on rugose corals, and are described here. Their boundaries, biostratigraphy and sequence stratigraphy are well detailed and clearly defined. The base of the Hastarian (lower Tournaisian) corresponds to the base of the Tournaisian (base of Carboniferous); the base of the Ivorian (upper Tournaisian) corresponds to the appearance of the conodont Polygnathus communis carina, a little above the last Siphonodella; the base of the Moliniacian (lower Viséan) corresponds to the base of the Viséan stage defined by the first occurrence of the foraminifer Eoparastaffella simplex; the Livian (middle Viséan) corresponds to the foraminiferal MFZ12 Zone and is marked by the appearance of Koskinotextularia and Pojarkovella nibelis; the base of the Warnantian (upper Viséan) is marked by the appearance of Neoarchaediscus, Vissariotaxis, Planospirodiscus, and Palaeotextularia with a bilaminar wall, the index taxa of the MFZ13-Neoarchaediscus Zone. The up-to-date chronostratigraphic subdivision of the Tournaisian and Viséan is not limited to Belgium and the surrounding areas. It can be applied through Eurasia as far as South China. The Belgian units could therefore be the basis for a future international division of the Tournaisian into two parts (Hastarian and Ivorian) and of the Viséan into three parts (Moliniacian, Livian and Warnantian), corresponding to time intervals of c. 5–8 Ma.