Paleoecological analasis of the miospore assemblages from the borehole 39, Moscow region, Russia

Abstract

Palynological material was obtained from Upper Visean deposits in the borehole No 39 that is located on the left bank of the Oka River, on 105 km to the south-east of the Moscow in the Serpukhov district. The lithological sequence of the borehole generally consist of the limestones, stigmarian limestones, interbedded with clays and siltstones. Total twenty five palynological samples from the sandy siltstones and charcoal clays (deep interval 29.4–33.25 m) have been collected. All samples contained abundant well-preserved miospores. Two palynoassemblages have been defined. The palynoassemblage S1 is described from the sandy siltstone and stigmarian limestones of the depth interval 29.4– 29.59 m. The palynoassemblage S2 is established from the coaly dark clays that occurred at the depth interval 29.64–33.25 m. All palynoassemblages are dominated by Lycospora pusilla. Based on both the presence Cingulizonaes bialatus, Triquitrites comptus, (index-species of the CBd palynozone) and the occurrence of the Late Visean species Tripartites vetustus, Triquitrites marginatus, Schulzospora campyloptera, Calyptosporites arenaceous the age of the palynoassemblages is defined as transitional Aleksinian-Mikhaylovian. The results well corresponded with data of miospore zonal scheme for Carboniferous of Russian Platform (Makhlina 1993). Paleoecological interpretation of the obtained palynoassemblages has been carrying out. General model of the paleoecological analysis is explained by the connection between the Carboniferous miospore taxa and their parent plants. Natural affinity of the miospores is determined by the comparison of dispersed material with the in situ spore findings that are elucidated in paleobotanical articles (more detail see Balme 1995, Orlova et al. 2014). In concordance with the comparison of the dispersed spores and in situ data, the miospore genera of the palynoassemblages have been subdivided into six paleobotanical patterns: arborescent lycopsids (Lycospora-producing plants), sub-arborescent lycopsids were produced the “densospores” (Densosporites, Vallatisporites, Cingulizonates), spores of ferns (Leiotriletes, Punctatisporites, Granulatisporites, Cyclogranisporites, Knoxisporites, Raistrikia, Tripartites, Triquitrites, Acanthotriletes, Convolutispora), miospores (prepollen) of seed ferns (Schulzospora, Remysporites, Geminospora, Rotaspora), spores of the sphenopsids (pars Calamospora) and pattern of unknown natural affinity (Diatomozonotriletes, Camarozonotriletes, Iugisporis, Simozonotriletes, Waltzispora, Calyptosporites). Abovementioned paleobotanical patterns are generalized into three paleoecological units: forest mire (arborescent and sub-arborescent lycopsids), non-forest mire (ferns, seed ferns and sphenopsids) and problematic one (unknown natural affinity). Accordingly, palynoassemblage S1 is dominated by arborescent lycopsids (66%). Sub-arborescent lycopsids (11%) and ferns (13%) were quite common in the plant communities. The seed ferns elements (2%) and sphenopsids (3%) were rare in the local palaeoflora. On the one side the forest-mire related miospores were increased upward the sequence (from 70% up to 88%), on the other side the percentage of the non-forest mire elements (from 26% up to 8%) were constant decreased in the same direction. The high percentage of forest mire unit is largely due to short