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

© 2020 Cushman Foundation. All rights reserved. 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 (Roa-dian Stage, Guadalupian Series) beds of Russia (East Euro-pean Platform and Urals), Turkey, and Tajikistan (Darvaz) allowed a revision of the species composition of the genera Honchinia, Monotaxirtoides, Eolasiodiscus, Turrispiroides, and Mesolasiodiscus. A new genus, Postmonotaxinoides, is described. The species Monotaxirtoides transitorius, M. suhplanus, 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 pecies are proposed

Microfacies of the Tulian Horizon (Visean Stage, Lower Carboniferous) of the Sikaza 2 section (Southern Urals, Russia)

The Carboniferous deposits of the Sikasi (Sikaze) River sections in the western part of the Southern Urals are of great geological importance and included in the list of particularly significant sites of the Toratau Geopark of the Republic of Bashkortostan. In this article, a lithofacies description of the carbonate deposits of the Tulian Horizon of the Visean Stage in the Sikaza 2 section near the Sikasi River was performed based on the microfacies analysis of carbonate rock sections of the samples from the collection of the Museum of Geology and Mineral Resources of the Republic of Bashkortostan (Ufa, Russia). Micro-description of limestones was carried out with the help of R. Dunham’s classification, E. Flügel’s methodology. The revealed textural and structural features and the composition of faunal remains in the Tulian deposits of the Sikaza 2 section allowed us to identify and describe in detail five microfacies of limestones that developed under the open-shelf conditions. The sequence of these microfacies indicates the alternation of sediments of currents and waves in the early Tulian time, which was followed by the gradual shallowing and formation of the shallow-shelf conditions by its end

The foraminiferal zonal scale of the Devonian–Carboniferous boundary beds in Russia and Western Kazakhstan and its correlation with ammonoid and conodont scales

This paper reviews the foraminiferal biostratigraphy of the Devonian–Carboniferous (D–C) boundary beds in Russia and Western Kazakhstan. The regional records of the zonal successions of Russia are summarised from sections and boreholes of the Volga-Urals Subregion of the East European Platform (Syzran no. 401 Borehole, Melekesskaya no.1 Borehole); Timan-Pechora Province of the East European Platform (Kamenka Section); South Urals (Sikaza, Zigan, Ryauzyak and Dzerzhinka sections); Middle Urals (Pershino Section); and West Siberia, Vagai-Ishim Basin (Borehole no. 1 Kurgan-Uspenskaya), and the zonal successions of Western Kazakhstan are summarised from the Mugodzhary Mountains. Three foraminiferal biozones can be defined in the interval comprising the latest Devonian and earliest Carboniferous: Quasiendothyra kobeitusana Zone, the Tournayellina pseudobeata – remnant Quasiendothyra Zone, and the Earlandia minima Zone. The D–C boundary interval is situated within the Tournayellina pseudobeata–remnant Quasiendothyra Zone. A correlation with the ammonoid and conodont zonations is proposed, which is useful for correlating deep-water and shallow-water successions

Room-temperature lasing in microring cavities with an InAs/InGaAs quantum-dot active region

Microring cavities (diameter D = 2.7-7 μm) with an active region based on InAs/InGaAs quantum dots are fabricated and their characteristics are studied by the microphotoluminescence method and near-field optical microscopy. A value of 22 000 is obtained for the Q factor of a microring cavity with the diameter D = 6 μm. Lasing up to room temperature is obtained in an optically pumped ring microlaser with a diameter of D = 2.7 μm. © 2013 Pleiades Publishing, Ltd

Investigation of the effect of surface passivation on microdisk lasers based on InGaAsN/GaAs quantum well active region

Microdisk lasers based on three InGaAsN/GaAs quantum wells with different types of surface passivation are fabricated and studied under optical pumping. Room temperature lasing at 1.3 μm in 7 μm in diameter microdisks with InGaAsN/GaAs QW is demonstrated. We evaluated the thermal resistance as 1 °C/mW.publishedVersionPeer reviewe