Radiolarian skeletons with their walls encrusted with calcareous nannofossils were studied, using the Upper Cretaceous (upper Campanian–Maastrichtian) cherty sections of the Saratov Volga region as an example. It has been shown that during the of diagenesis of siliceous rocks, with sedimentation slow or absent, the biogenic components, specifically rock-forming microfossils such as radiolarian skeletons, can undergo complete leaching, dissolution, or significant recrystallization and replacement by other mineral phases such as bacterial calcite, or become encrusted with microscopic nannoplankton. The mechanism of “encrustation” of radiolarian skeletons with calcareous nannofossils indicates the presence of a hiatus in sedimentation that is invisible in the visual description of the sections.
Ichnofossils are quite characteristic of the Lower Ordovician terrigenous formations of Tuva. Traces of vital activity of organisms found in the Lower Ordovician section of the Ulug–Khondergey–Koshara include Trypanites Mägdefrau, Scoyenia White, ?Skolithos Haldeman, ?Conichnus Männil. A new ichnotaxon Trypanites khondergensis is proposed for the Tuvan Trypanites.
New radiolarian assemblages not previously known from the Eastern Peri-Tethys are identified and described from Lower and Middle Danian flysch deposits on the southern slope of the Northwestern Caucasus (Agoy–Tuapse area). Index species and associated assemblages are correlated with zones RP1, RP2, and RP3 of the Global Paleogene Standard (GPS) Austral scale. The photographs of radiolarians presented in this paper provide valuable scientific material. Continued research will allow development of the Paleocene radiolarian zonation scale for the Peri-Tethys basin.
This is the first description of a representative of the problematic Morania Walcott, 1919, interpreted as remains of cyanobacterial colonies, from deposits of the Amgian Stage of the Middle Cambrian (Wuliuan Stage and lower Drumian Stage of the Miaolingian Series of the International Stratigraphic Chart) in Yakutia. Their macroscopic and microscopic morphology, ecological characteristics, and possible systematic position are discussed. A new species has been identified, distinguished from all other species of this genus by the co-occurrence of separate drop-like colonies. Possible mechanisms regulating the regular arrangement of colonies within the settlement are discussed.
Three new species of Lower Permian radiolarians are described from the Sakmarian and Artinskian of the South Urals, from the Dal’ny Tulkas main section and trench section near the village of Krasnousolsk and from the Staritsa section near the village of Donskoe: Pluristratoentactinia rozanovi sp. nov., Astroentactinia sungatullinae sp. nov., and A. gracilobelona sp. nov.
