Discovery of the Ordovician Kinnekulle K-bentonite at the Põõsaspea cliff, NW Estonia

A previously unknown outcrop of the Kinnekulle K-bentonite (metabentonite) is reported from the Põõsaspea cliff, NW Estonia. The bed has a sharp lower and a gradational upper contact and comprises ca 28 cm of clay overlain by ca 10 cm of hard K-feldspar-rich variety. The latter contains a layer of breccia, which indicates early onset of recrystallization and hardening of volcanic material. The discovery shows that the Põõsaspea cliff section is younger than previously thought and includes rocks of both Haljala and Keila stages

Carbonate shelf development and early Paleozoic benthic diversity in Baltica : a hierarchical diversity partitioning approach using brachiopod data

The Ordovician-Silurian (similar to 485-419 Ma) was a time of considerable evolutionary upheaval, encompassing both great evolutionary diversification and one of the first major mass extinctions. The Ordovician diversification coincided with global climatic cooling and paleocontinental collision, the ecological impacts of which were mediated by region-specific processes including substrate changes, biotic invasions, and tectonic movements. From the Sandbian-Katian (similar to 453 Ma) onward, an extensive carbonate shelf developed in the eastern Baltic paleobasin in response to a tectonic shift to tropical latitudes and an increase in the abundance of calcareous macroorganisms. We quantify the contributions of environmental differentiation and temporal turnover to regional diversity through the Ordovician and Silurian, using brachiopod occurrences from the more shallow-water facies belts of the eastern Baltic paleobasin, an epicontinental sea on the Baltica paleocontinent. The results are consistent with carbonate shelf development as a driver of Ordovician regional diversification, both by enhancing broadscale differentiation between shallow- and deep-marine environments and by generating heterogeneous carbonate environments that allowed increasing numbers of brachiopod genera to coexist. However, temporal turnover also contributed significantly to apparent regional diversity, particularly in the Middle-Late Ordovician.Peer reviewe

A diverse Hirnantian scolecodont assemblage from northern Estonia and resilience of polychaetes to the end-Ordovician mass extinction

We report the discovery of a rich assemblage of latest Katian and Hirnantian scolecodonts (polychaete jaws) from a new OrdovicianâSilurian boundary outcrop in the Reinu quarry, northern Estonia. The recovered polychaete fauna contains at least 40 species attributed to 11 families. Many common taxa appear to range from the latest Katian to the Hirnantian and into the Rhuddanian, indicating the resilience of jawed polychaetes to the end-Ordovician mass extinction. The Reinu assemblage is similar to the coeval faunas known from other Baltic sections, as well as from Anticosti Island, Canada, although with some specific features. The study revealed the highest abundance of scolecodonts in the Ordovician of Baltica, with ca 5400 maxillae per kilogram of rock recorded in the Siuge Member of the Ãrina Formation, Porkuni Regional Stage, early Hirnantian

Searching for the Ordovician–Silurian boundary in Estonia, Latvia and Lithuania

The present study focuses on determining the position of the lower boundary of the Silurian System in the eastern Baltic region. To achieve this, we conducted a comprehensive analysis of stable isotopic curves, combined with previously published data on the graptolite record. Our isotopic correlations are primarily based on the δ13Corg curve of the Dobâs Linn section, the GSSP of the Silurian System, and the δ13Ccarb curve of the Monitor Range section in Nevada. Our results provide robust evidence for correlating the basal Varbola Formation, the lower part of the Ãhne Formation and the StaÄiÅ«nai Formation, and suggest their latest Ordovician age. The integration of stable isotopic data and graptolite records allows for a more accurate characterisation of the OrdovicianâSilurian boundary in this region

Chitinozoan nomenclature and databases

In 1930, Alfred Eisenack suggested the term âchitinozoanâ for a microfossil group that he discovered from erratic boulders on the Baltic Sea coast. They are known from the Early Ordovician until the end of the Devonian and have a broad paleogeographic distribution in marine deposits. Even though they are useful biostratigraphy markers, their biological affinity is unknown. Several theories have been proposed through the years, with the most widely accepted to date being that they are the eggs of soft-bodied metazoans. Nevertheless, some studies suggest that chitinozoans are fossils of individual microorganisms (protists) rather than of metazoan origin. The aim of this contribution is to summarize the advantages of the current chitinozoan classification and analyze the status quo of the current chitinozoan databases in order to make the classification less subjective and data more accessible. Since the beginning of their study, chitinozoan workers have used a binominal taxonomy describing genera and species based on morphological features. In 1999, Florentin Paris and co-authors introduced a revised suprageneric classification regulated by the International Code of Zoological Nomenclature (ICZN), which proved very efficient and has since been followed by all workers on this group. According to the ICZN, the concept of âspeciesâ is the only one that refers to an actual population or entity and all higher categories are abstract entities. This means that any feature can be selected to separate the genera and families. In chitinozoans, scanning electron microscope (SEM) images are used to distinguish morphologic features such as the vesicle, aperture, neck, and ornamentation. These main characteristics were used as the basis of classification. The category of âOrderâ is not regulated by the ICZN; however, in 1972, Eisenack proposed the useful subdivisions of âOperculatiferaâ and âProsomatiferaâ that have been maintained until today. This classification gives stability to the nomenclature, prevents overlap of generic descriptions, and provides a framework for phylogenetic analysis. It was highlighted by the authors of this classification that a computer-assisted system of identification could be developed if a digital taxonomic database were available. There are several databases with the potential to be useful for chitinozoan taxonomic classification. ZooBank is the official registry of the ICZN. It records nomenclatural acts and includes the original descriptions of new scientific names and their publications. For occurrence-based paleontological records, the Paleobiology Database and the Geobiodiversity Database are extremely useful. Both have an intuitive and simple interface for the user to see the taxa distribution and taxonomic information. These three databases complement each other, but they either have few chitinozoan records or lack complete taxonomic information. There is a desktop taxonomic database CHITINOVOSP for chitinozoans, designed by Florentin Paris, which has proven to be useful but needs to be purchased. Achab et al. developed in Canada another chitinozoan database CHITINOS that is not currently used. The most complete and useful chitinozoan database at present seems to be CHITDB, where browsing and searching for chitinozoan taxa, samples, sections, references, and SEM images is simple. However, it is focused only on material from the Baltic region. Databases such as the Encyclopedia of Life, the Catalogue of Life and the World Register of Marine Species lack chitinozoan records but they are collaborative and provide free global access to knowledge. This collaborative formula seems to be efficient enough to have a trusted digital source of information. Since at present the taxonomic classification of chitinozoans is no longer under discussion and it has proven to be workable, the following step for chitinozoan researchers would be to have a complete database. We believe that a collaborative effort should be made as there are only a few specialists in the area nowadays. It is not crucial which database should be completed, but it should be useful, as complete as possible, and freely accessible. In particular, we believe that the Baltic CHITDB database is an excellent starting platform to achieve that goal in the near future

Latest Ordovician age of the Spinachitina fragilis Chitinozoan Biozone in Baltoscandia

The global Spinachitina fragilis Chitinozoan Biozone has been considered the lowermost Silurian zone in most publications. S. fragilis was first described from the Ohesaare drill core, Estonia, and utilised as a Baltic regional zonal taxon together with Ancyrochitina laevaensis. Despite its wide geographical occurrence, S. fragilishas remained poorly documented in its type region. This has created confusion in taxonomy and distribution of the species. Herein, we have restudied material from the type locality and supplementary sections in the East Baltic region. S. fragilis generally has a very short stratigraphic range, which, according to new data on carbon isotope chemostratigraphy, coincides with the falling limb of the Hirnantian carbon isotope excursion. This suggests the latest Hirnantian rather than the early Rhuddanian age of the Spinachitina fragilis Chitinozoan Biozone in Baltoscandia. Based on this view, we revise the latest Ordovician chitinozoan biozonal scheme for the region. Globally, the S. fragilis Biozone may span across the OrdovicianâSilurian boundary