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Algae have always been the most diverse and numerous eukaryotic autotrophs in marine ecosystems. Both fossil andmolecular data point to an early Proterozoic origin for algae. Although known for their long evolutionary history, the fossil recordof algae is sparse and mainly remains of taxa with heavily calcified thalli are preserved. However, fossils of noncalcareous algae,known as extremely sporadic and occasional finds from different parts of the world, provide important insights into thepalaeobiology of algal flora in the Earth's past. Here we describe highly diverse flora of noncalcareous thallophytic algae from aSilurian age deposit.

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 δ13Corgcurve of the Dob’s 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 Õhne Formation and the Stačiūnai Formation, and suggest their latest Ordovician age. The integration of stable isotopic data and graptolite records allows for a more accurate characterisation of the Ordovician–Silurian boundary in this region. [ABSTRACT FROM AUTHOR]

The article presents the highlights of the archaeological investigations in the Tarvastu Castle of the Teutonic Order in Viljandi County, Estonia. The castle was claimed to have been built in the 14th century. Also cited are a brief history of the castle including its association with the Livionian Master and the incursions by Russian and Lithuanian militaries, as well as the conduct of the first archaeological excavations at the castle in 2021.

Brachiopods are the biological constituents most often used for the delineation of stable C and O isotopic compositions in Palaeozoic sediments. We present C and O isotope data for the Late Ordovician and early Silurian to evaluate the palaeotemperatures and palaeoenvironmental variability in Baltica from bulk rock and brachiopod shells. The studied carbonate rocks and fossils are well preserved in most of the localities as the area has not been affected by substantial tectonic activities or deep burial diagenesis. The δ13C and δ18O values for the samples range from-1.5‰ to 5‰ and from -7‰ to -2‰, respectively. If the isotope signal reflects the original oxygen composition in sea water, the high δ13C and δ18O values could correspond to the colder episodes and vice versa. The Late Ordovician Hirnantian stable carbon isotopic excursion (HICE) is well recognized globally as an eminent glacial isotopic event and has been reported in several sections in the Baltic region. The HICE is observable in the bulk rock carbon stable isotope curves as a very clear gradual rise and a maximum confined to the upper part of the Ärina Formation (Porkuni Regional Stage) in northern Estonia. The rising interval of δ13C in the Ärina Formation may correspond to the early Hirnantian time interval. The peak HICE is followed by a gradual decline in the δ13C values in the basal beds of the Varbola Formation (Juuru Regional Stage). The bulk carbonate δ18O values show a prominent positive excursion in the Hirnantian interval possibly reflecting the global cooling event. The post-glacial latest Ordovician to early Silurian global warming might be responsible for the clear decreasing trend of both the δ18Obulk and δ18Obrach values in the interval of the Juuru Regional Stage in the studied sections. Our study shows that δ18O values revealed from both the brachiopod and bulk rock material of marine Upper Ordovician-lower Silurian carbonates could tentatively be interpreted as reflecting the major temperature trends. [ABSTRACT FROM AUTHOR]

The Middle Darriwilian Isotopic Carbon Excursion (MDICE) is a global isotopic event described in sections from different palaeocontinents. Here we present new stable carbon isotopic data from carbonates of ten sections in different parts of the Baltoscandian Palaeobasin (Estonia, Latvia, Lithuania, Sweden, NW Russia). The definition of the MDICE as a chemostratigraphic unit is discussed, as well as the subdivision of its peak into two distinct peaks. The MDICE is one of the longest carbon isotopic events in the Palaeozoic. It was preceded by the L-chondritic cosmic dust flow event, which may have been responsible for cooling through the Darriwilian and the initiation of the Great Ordovician Biodiversification Event. High-resolution chemostratigraphic analyses show that the time interval between these environmental events and the base of the MDICE is up to one million years. Due to the long duration of the MDICE the modelling of this excursion should address more complex scenarios than a simple response of the carbon cycle to rapid climatic perturbations. [ABSTRACT FROM AUTHOR]

Copyright of Estonian Journal of Earth Sciences is the property of Teaduste Akadeemia Kirjastus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Estonian Journal of Earth Sciences is the property of Teaduste Akadeemia Kirjastus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A metre-scale thick siltstone-sandstone lobe is described within the Dapingian outer ramp argillaceous limestone facies of the Baltoscandian palaeobasin. This bed is referred to as the Volkhov Oil Collector in previous studies due to its hydrocarbon accumulation potential. It formed on the palaeoslope of the regional Jelgava Depression, which represents an elongated axial region of the deepest part of the Ordovician Baltoscandian sedimentary basin. Sedimentological and petrological analysis of this siliciclastic bed in core sections shows that it was deposited as a result of a single event of turbidite flow. The internal structure of the turbidite bed follows the classical Bouma divisions of the turbidite sequence model. The triggers of this single siliciclastic turbidite bed within a tectonically inactive shallow carbonate basin are analysed. It is concluded that a rare tsunami might have eroded and transported sediments in suspension from land to shallow sea. Suspension fallout would have evolved into a density flow and later into a turbidity current that travelled into the deeper parts of the basin, depositing siliciclastic material at the slope of the Jelgava Depression. The occurrence of the Volkhov Oil Collector turbidite bed on the tectonically relatively stable and flat-bottomed Baltoscandian palaeobasin suggests that turbidite events can take place in rare cases also in epicontinental environments. [ABSTRACT FROM AUTHOR]

Palaeozoic carbonate δ13C studies have mainly focused on bulk rock analysis in chemostratigraphic correlations and palaeoenvironmental interpretations, assuming limited isotopic heterogeneity of samples. Particular attention has been paid to positive δ13C excursions, which likely reflect climatic events. However, several studies have provided isotope data from different rock components demonstrating significant sample-scale variation of δ13C values. We describe the isotopic and elemental composition of individual components in carbonate rocks and analyse which components carry the primary depositional isotopic signatures and which components have been isotopically reset by diagenetic processes. The comparison of bulk rock and component-specific data allows us to assess the reliability of isotopic data used in environmental reconstructions and offers an opportunity to better reconstruct magnitudes of δ13C excursions and related dynamics of seawater dissolved inorganic carbon. Here we focus on the Hirnantian Isotopic Carbon Excursion (HICE) at the end of the Ordovician period and the Mid-Ludfordian Carbon Isotope Excursion (MLCIE) during the late Silurian period. Previous bulk rock studies have demonstrated the occurrence of the HICE in multiple Estonian drill cores corresponding to the Porkuni Regional Stage. The HICE samples from the Kamariku, Karinu, and Otepää drill cores were subsampled by micro-drilling, and isotope analysis of individual components was done by isotope-ratio mass spectroscopy (IRMS). Limited sample-scale heterogeneity and good correspondence with bulk rock δ13C values are seen in micritic carbonate samples, whereas different bioclastic and cement components in wackestone and grainstone samples exhibit up to 4‰ range of δ13C values with some components having δ13C values up to 3‰ higher than the bulk rock values. Lithologically heterogeneous grainstone from the Otepää core shows δ18O variability as much as 3‰ and ooids carrying the lowest, most overprinted values. Isotope results obtained by the Secondary Ion Mass Spectrometry (SIMS) on MLCIE samples from Lithuanian Vidukle drill core show up to 5‰ range of δ13C values, and some values are up to 4‰ higher than the bulk rock values. A similar range can also be seen in δ18O values. Our results demonstrate that multi-component wackestone and grainstone samples from HICE and MLCIE intervals are isotopically heterogeneous and that heterogeneity needs to be accounted for in reconstructions of the past carbon cycle and δ13C curves. [ABSTRACT FROM AUTHOR]

Depression of the ancient Lumparn meteorite impact structure in the Åland Islands is partly infilled with the lower Palaeozoic sediments, lying presently below sea level. The Cambrian and Ordovician sedimentary cover is distributed in the area of 15 km², with a total thickness of up to 70 m. The Ordovician carbonate rocks of this site, known by the erratic boulders and by the drill­ing project in the late 1950s, are particularly interesting because of the isolated distant position of this outlier from other distribution areas of the Ordovician sediments preserved in the Baltoscandian Palaeobasin. Ordovician sections in the Lumparn Bay are com­posed of two distinct lithological units. The older, argillaceous wackestone-packstone unit has been tradi­tionally named ‘Orthoceras limestone‘ or ‘Orthoceratite Limestone’, and the younger micritic limestone unit is addressed as ‘Östersjö Limestone’ (or ‘Baltic Limestone’). Here we present new data on ostracod biostratigraphy and stable carbon isotope chemo­stratigraphy derived from three old drillcores from the Tranvik area of the Lumparn Bay. The comparison of ostracod distribution with its succession in Estonia generally supports the previous Darriwilian and Sandbian age interpretations for the Orthoceras Limestone. Considering the ostracod distribution together with earlier acritarch and conodont datings, stable carbon isotopic data and limestone lithology, the Orthoceras Limestone unit might correspond to the Kunda, Aseri, Lasnamägi, Uhaku, Kukruse, Haljala, and Keila regional stages (RSs). The Österjö Limestone comprises almost the entire Katian, corresponding to the Rakvere, Nabala, Vormsi and Pirgu RSs in the Baltoscandian stratigraphic chart. The uppermost sample yielded the most abundant and diverse assemblage of ostracods that suggests it to correspond to the Vormsi or lower-middle Pirgu (late Katian) RSs. The global Middle Darriwilian Carbon Isotopic Excursion (MDICE) and Guttenberg Carbon Isotopic Excursion (GICE) as well as the Katian Rakvere and Saunja carbon isotopic excursions are recorded in the studied succession. The δ13Ccarb bulk rock curve of the Orthoceras Limestone shows a positive excursion up to 1‰ in the lower part of the interval followed by a negative excursion up to –1‰ in the middle part and another positive excursion reaching 2‰ in the upper part of the interval. This curve resembles well the carbon isotope curve from the Darriwilian and Sandbian in the core sections of the Hiiumaa Island, NW Estonia, and could be interpreted as the MDICE and the rising limb of the GICE. The δ13C curve of the Östersjö Limestone interval shows two positive excursions. The lower one comprises most likely the peak of the Rakvere Excursion (Rakvere RS) in Estonia, which is also supported by the ostracod data. The upper carbon isotopic excursion may represent the Saunja Excursion correlated with the upper part of the Nabala RS. The ostracod biofacies characterized by faunal associations of both the Orthoceras and Östersjö limestone units, and the lithological succession of these units suggest more similarities with the Estonian Shelf facies (North Estonian Confacies) than Scandinavian Basin facies of the Baltoscandian Palaeobasin. [ABSTRACT FROM AUTHOR]

Magnetic susceptibility (MS), its frequency-dependence and anisotropy of the Middle Ordovician Dapingian and Darriwilian sedimentary sequence from three sites (Uuga, Testepere and Leetse) in the Pakri Peninsula, NW Estonia are analysed in combination with the mineralogical composition. The study is based on 463 cores drilled at intervals of a few centimetres to a maximum of about 1 m. All the samples show low and positive MS, which suggests the presence of small quantities of paraand/ or ferromagnetic minerals. The stratigraphic units of the three studied sites have a similar along-section appearance, which provides a base for a composite curve. The relatively higher susceptibilities are carried by secondary Fe-Ti oxides (Toila Formation), goethite ooids (Kandle Formation) and ferrous dolomite (Pae Member), whereas paramagnetic minerals are mostly responsible for the rest of the sequence. Considering the dependence of MS on regressive-transgressive cycles (high/low MS within deposits of regressive/transgressive parts of the cycles, respectively), the MS data do not agree with sedimentologically derived sea-level compilations. The measured changes in MS in the Pakri Peninsula outcrops correlate at certain characteristic levels with those deposited in the deeper part of the palaeobasin (Viki core), indicating that the post-depositional iron mobilization within the sediments took place at least at a regional level. Because of post-depositional reorganization of ferromagnetic carrier minerals, the MS values may, however, not be used as a detrital proxy. [ABSTRACT FROM AUTHOR]

Copyright of Estonian Journal of Earth Sciences is the property of Teaduste Akadeemia Kirjastus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Hirnantian Isotope Carbon Excursion (HICE), a glaciation-induced positive δ13C shift in the end-Ordovician successions, has been widely used in chemostratigraphic correlation of the Ordovician--Silurian boundary beds in many areas of the world. However, large regions with Ordovician sediments in Siberia are almost unstudied for stable isotope chemostratigraphy. The Burovlyanka section in the Altai area is one of the rare Hirnantian--Rhuddanian sections with both carbonates and graptolitiferous shales occurring in the succession. Here we report the discovery of the HICE in the uppermost beds of the Tekhten' Formation, the Dalmanitina Beds in the Burovlyanka section. The Dalmanitina limestone Member between the graptolitiferous shales may correspond to the mid-Hirnantian glacial episode, which led to a global sea level drop and major extinction of marine fauna. [ABSTRACT FROM AUTHOR]

The δ13C isotope data from the Tartu-453 core section in southern Estonia enabled creation of a continuous Ordovician carbon isotope record, ranging from the Floian to the end of the Hirnantian. Five positive δ13C excursions and one negative δ13C excursion were recognized. Most of the positive excursions correspond to those defined on the Baltoscandian carbon isotope chemostratigraphic scheme, except for the Paroveja and Rakvere ICEs which are not well expressed in the Tartu-453 curve. Besides the positive δ13C excursions, a distinctive negative δ13C excursion, the Lower Sandbian NICE, was recorded in the Tartu-453 succession. The well-expressed HICE extends about 10 m higher than the traditional Ordovician-Silurian boundary (between the Porkuni and Juuru regional stages) into the Juuru Regional Stage, suggesting that the Ordovician-Silurian boundary is positioned significally higher than traditionally suggested for the East Baltic area. [ABSTRACT FROM AUTHOR]

Based on the integrated chemostratigraphic and lithostratigraphic studies, as well as biostratigraphic and palaeo-ecological analyses of conodonts in the Ledai-179 core, we present a combined model of change in the upper Wenlock and lowermost Ludlow strata of the inner shelf settings in the eastern part of the Baltic Basin. The comparison of the δ13C trend, and conodont and lithological successions confirms previous suggestions that the Birštonas and Nevėżis formations correspond to the Homerian. This is quite unexpected, however, that the chronostratigraphic position of the Širvinta Formation changed from the Gorstian to the upper part of the Homerian. The numerical biostratigraphic changepoint analyses of local conodont richness, per capita immigration and also per capita extirpation rates revealed several episodes of permanent change. These episodes of dynamic states either preceded or postdated the Mulde extinction interval at the beginning of the late Homerian δ13C excursion, which points to possible transient effects of this extinction event on conodonts. [ABSTRACT FROM AUTHOR]

Isolated asterozoan ossicles and pedicellariae occur in micropalaeontological samples from the Darriwilian (Middle Ordovician) of the Mishina Gora section, north-western Russia. The well-preserved Bursulella unicornis type fossils represent the oldest hitherto record of asterozoan pedicellariae. The accompanying ossicles are not diagnostic but allow their tentative placement within the asteroid stem group. The abundance of disarticulated ossicles in the samples proves that asterozoans were not as rare as they have been considered and were important members of Ordovician ecosystems in the Baltic Palaeobasin. [ABSTRACT FROM AUTHOR]

Copyright of Estonian Journal of Earth Sciences is the property of Teaduste Akadeemia Kirjastus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Focuses on the erosional history of the rimwall of the K aumi rdla meteorite crater in Hiiumaa, Estonia as indicator of Late Ordovician sea-level changes in the Baltoscandian area. Geological setting of the crater; Thickness differences of post-impact sediments; Composition of non-carbonate material in sediments.