Diverse ophiuroid faunules from the basal Teplice Formation, of Late Turonian age, exposed at Úpohlavy in the northwestern part of the Bohemian Cretaceous Basin, northwest Bohemia, are based on only dissociated lateral arm plates, vertebrae and some other skeletal elements of the disc. The material can be ascribed to ten species, including a new taxon named Stegophiura? nekvasilovae sp. nov. Three additional species are represented in the material but these are left in open nomenclature. Relative species abundance is evaluated and discussed.•

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In 1908, a massive explosion known as the Tunguska Event (TE) occurred in Central Siberia. However, its origin remains widely discussed and environmental impacts are not known in detail. We investigated evidence of the TE in sediments of Suzdalevo Lake, which is located near the explosion epicenter. According to local nomads (Evenkis), Suzdalevo Lake did not exist before the TE and was considered as a possible impact-origin water body. However, apart from oral testimony, there is no evidence of the lake formation process. Two short sediment cores (SUZ1 and SUZ3) were retrieved from the lake and dated using 210Pb and 137Cs. The sedimentary record was characterized using magnetic susceptibility, X-ray fluorescence, and the screening for melted magnetic microspherules. To study possible effects of the TE on the lake ecosystem, we performed diatom and freshwater fauna remains analyses. Results indicate that the lake contains sediments that originated before the TE and thus its formation was not related to the impact. Also, the depth to diameter ratio of the lake basin is too low (<1/100) for a young impact crater. In one of the two cores (SUZ1), we documented distinct changes in the lake-catchment ecosystem that occurred within a 5-cm-thick depth interval calculated for the best fit depths for the year 1908 using three alternative age-depth models (CRS, CIC, CFCS), namely, increases in terrestrial matter input (abundant fine plant macroremains, peaks in magnetic susceptibility and the Sr to Rb ratio) and taxonomic diversity and relative abundance of benthic taxa. The shifts in aquatic biota assemblages were likely caused by nutrient supply and improved water column mixing following a catchment disturbance. Nevertheless, precise timing of the observed abrupt changes in relation to the TE is not clear due to uncertainty of the 210Pb dating method and absence of melted magnetic microspherules or an event layer. The disturbance signals in the proxy data may postdate the TE. Our results demonstrate potential usefulness of the paleolimnological approach to understand the possible environmental consequences of the TE and similar events elsewhere.

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<p>Near 12,850 cal. yr. BP, the Younger Dryas cooling (YD) abruptly reversed the warming trend from the last glacial to the present interglacial at high northern latitudes. Subsequent YD-onset-related changes, including hydroclimate shifts, affected ecosystems and human societies worldwide. The main YD trigger – e.g., a massive meltwater input into the North Atlantic Ocean, volcanic gas aerosols from the cataclysmic Laacher See (LS) eruption in the Volcanic Eifel, Germany, or an extraterrestrial body impact or airburst – remains widely debated and unclear. We have obtained lake sediment cores from three sites located in the Bohemian Forest Mts., Czechia-Germany-Austria border area (distance of 450–470 km from the LS volcanic crater). The characteristic LS tephra glass shards were documented in all three cores using X-ray fluorescence scanning, magnetic susceptibility measurements, and direct observation by scanning electron microscopy, and their concentrations were quantified by a TESCAN Integrated Mineral Analyzer (TIMA). Our geochemical results show the closest match with the so-called MLST-B phreatomagmatic phase of the LS eruption. Moreover, a significant amount of LS-(crypto)tephra-related phosphorus (up to 0.15%), often the limiting nutrient in both terrestrial and freshwater ecosystems, was found in the sediments. The discovery of the LS volcanic ash in the Bohemian Forest points to a wider distribution of this (crypto)tephra than has been known so far (evident transport also in the eastern direction). It opens up new potential for tephrochronologically supported research of Late-glacial sediments in eastern Central Europe and exploring the role of the event in human prehistory. In addition to the LS cryptotephra, we observed magnetically extracted iron-rich microspherules with signs of high-temperature melting and quenching in all studied sediment cores. Their maxima (3–36 objects per 1 g of dry sediment) were situated 2.2–3.1 cm above peaks in the LS tephra shard concentrations. Such exotic objects were reported from numerous sites on several continents where more impact-related proxies were documented by proponents of the YD impact hypothesis. Based on this evidence, we hypothesize that the Allerød-Younger Dryas transition in Central Europe was likely affected by more than one extreme event. The LS eruption was followed by an event during which the iron-rich microspherules were formed. The ongoing study is supported by the Czech Grant Foundation (20-08294S – PROGRESS).</p>