Search

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 distribution of five groups of fossils in the upper Llandovery (Telychian) and Wenlock of the Viirelaid core section, Estonia, is presented and discussed in terms of their biozones (conodonts and chitinozoans) and mutual positions (scolecodonts, ostracods, and brachiopods). Graphical correlation of the Viirelaid and Paatsalu sections shows a stronger linear correlation for zonal conodonts than for chitinozoans and scolecodonts. In the given case, this is caused by different nature of zones: chitinozoan zones are based on appearances and/or disappearances of ordinal taxa whereas conodont zonation corresponds, as a rule, to evolutionary succeeding species in the Pterospathodus lineage. At the same time, the positions of chitinozoan zones in the Viirelaid, Ruhnu, Aizpute, and Paatsalu cores are oscillating with respect to conodont zones.

Conodonts are an important biostratigraphic tool for many Phanerozoic stages. Along with graptolites, they define all global Ordovician Stage boundaries. Within the Upper Ordovician interval, a known species of Amorphognathus tvaerensis (Bergström) is present in both Sandbian and Katian stratotype sections. Study of changes in the succession of A. tvaerensis revealed that elements in the upper part of its range differ morphologically quite distinctly from those in its lower part. Here, they are described as a new conodont species, A. viirae sp. nov. This new species is recognized in several Estonian and Swedish sections, with apparent occurrence also in Mójcza Quarry, Holy Cross Mountains, Poland and Black Knob Ridge, Oklahoma, USA. Detailed analysis of early Amorphognathus elements from Estonian and Swedish sections revealed the absence of A. inaequalis (Rhodes) in both regions, although a conodont subzone based on this species was identified earlier by some authors. Both the absence of A. inaequalis (Rhodes) and recognition of the new species A. viirae sp. nov. resulted in the revision of the conodont zonation, and a new version of it is proposed for the Sandbian Stage in the Atlantic Realm. The new zonation includes (from below) Pygodus anserinus , Baltoniodus variabilis , A. tvaerensis , B. gerdae , A. viirae and B. alobatus Conodont zones. [ABSTRACT FROM AUTHOR]

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 present work analyses the numerical distribution data of ostracods in the Late Ordovician (Katian) deposits of Estonia for establishing trends in carapace morphology along a facies profile from a shallow shelf to a deep basin. We present a quantitative analysis of facies-related trends in carapace size, shape and ornamental features. In addition, changes in diversity as well as major changes in the taxonomic composition of the assemblages are addressed, based on the number of individuals. The quantitative analysis of ostracod distribution data reveals distinct trends in the offshore direction: carapaces become larger and shorter, the dominance of smooth valves decreases and the share of ornamented valves increases. Tuberculate valves are most common in open-shelf environments. Species diversity decreases in the offshore direction. The taxonomic composition changes from a clear majority of podocopes to an association of podocopes and palaeocopes, and further to a majority of binodicopes. The fact that these patterns are persistent throughout the Late Ordovician (within three chronostratigraphic units) suggests that they represent environmental control. Some of the results are not in full agreement with previous observations. [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 Late Ordovician Baltic Palaeobasin (BPB) offered a favourable environment for a diverse and abundant ostracod fauna to thrive across the basin. A short period of unstable environmental conditions at the end of the Ordovician, the Hirnantian glaciation, and the concurrent extinction event completely rearranged the ostracod associations. Statistical analyses reveal temporal (diverse preglacial, more uniform glacial and poorly diverse postglaciation faunas) and geographical (upper shelf and middle shelf faunas) separation of ostracod associations in the BPB. The geographical division applies to the preglacial and glacial faunas only; the scanty postglacial fauna found in deeperwater sections is uniform. Ostracod associations are distinct both in a temporal and geographical sense. Juxtaposing ostracod data with δ13C curves shows that the typical Hirnantian Harpabollia harparum fauna in the BPB appeared near the peak of a δ13C excursion. This might explain why the H. harparum fauna seems to appear first in deeperwater sections and is absent or appears later in shallowerwater sections. The majority of the nearshore sections in Estonian and Lithuanian shelves lack most or all of the Hirnantian strata. The lowermost Hirnantian is preserved in only a few sections (e.g. Männamaa and Puhmu in Estonia). The appearance of the postglacial ostracod fauna, which most probably was a survival fauna rather than a recovery fauna, is related to the falling limb of the δ13C curve. The appearance of this fauna was previously considered as a marker of the Ordovician-Silurian boundary in the region but, according to the present understanding, took place in the late Hirnantian. [ABSTRACT FROM AUTHOR]

Ostracods of the Ordovician and Silurian transition interval in the Jūrmala section, Latvia, were studied. The diverse pre-Hirnantian ostracod assemblage is replaced by the Harpabollia harparum association that has been recorded across the Baltoscandian region and northwestern Poland and is confined to the Hirnantian. The first complete ostracod succession throughout the Kuldīga and Saldus formations reveals a remarkable diversity decline and rise of dominance of ostracods in this interval. The appearance level of the H. harparum association in other sections is drawn distinctly above the range of Spinachitina taugourdeaui, nearly coinciding with the appearance of Conochitina scabra and Noixodontus girardeauensis. The transition from the Saldus Formation into the Stačiunai Formation marks a complete ostracod turnover. The newly appearing assemblage, dominated by Longiscula smithii, is of low diversity. Slow diversity rise may in part be ascribed to the overall low recovery rate of post-glaciation faunal assemblages. The shape of the stable carbon isotopic curve in the Jūrmala core suggests that this section is one of the most complete successions across the Ordovician-Silurian boundary in the Baltoscandian area. The correlation of this curve with that of the Monitor Range, Nevada, and comparison with other curves of Latvia and Estonia suggest that the well-known appearance level of the 'Silurian faunas' is confined to the upper M. persculptus graptolite Zone. Judging from the chemostratigraphic correlation, the latter zone ranges for more than 10 m into the Stačiūnai Formation in the Jūrmala core. [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 common problem in biogeochemical mapping and contamination studies is that the same plant species are not available everywhere. Filipendula ulmaria is a widely used indicator plant but it does not grow in dry and high altitude areas. We used different plant species (F. ulmaria, Carex species and Urtica dioica) and analysed the concentrations of Cd, Cu, Fe, Mg, Mn, Pb, Zn and P in the material from 19 sampling points in eastern Estonia. The geometric mean concentrations of Pb, Cd and Zn were similar in F. ulmaria and Carex, as were the dominating ranges of Cu, Mn and Zn. The geometric mean concentrations typically differ between F. ulmaria and U. dioica. Simultaneous use of multiple indicator plants could generally not be recommended. Still, in case of urgent need the results could be amalgamated for the elements with more than 50% similarity of dominating ranges in different plants. [ABSTRACT FROM AUTHOR]

Previous late Precambrian and Cambrian correlation charts of Estonia, summarizing the regional stratigraphic nomenclature of the 20th century, date back to 1997. The main aim of this review is updating these charts based on recent advances in the global Precambrian and Cambrian stratigraphy and new data from regions adjacent to Estonia. The term 'Ediacaran' is introduced for the latest Precambrian succession in Estonia to replace the formerly used 'Vendian'. Correlation with the dated sections in adjacent areas suggests that only the latest 7-10 Ma of the Ediacaran is represented in the Estonian succession. The gap between the Ediacaran and Cambrian may be rather substantial. The global fourfold subdivision of the Cambrian System is introduced for Estonia. The lower boundary of Series 2 is drawn at the base of the Sõru Formation and the base of Series 3 slightly above the former lower boundary of the 'Middle Cambrian' in the Baltic region, marked by a gap in the Estonian succession. The base of the Furongian is located near the base of the Petseri Formation. [ABSTRACT FROM AUTHOR]

For nearly a century the Ordovician System was hidden as Murchison and Sedgwick tussled over the overlapping ground between their Silurian and Cambrian systems. The Ordovician is, in fact, one of the longest of the geological periods, characterised by major magmatic and plate tectonic activity; the roles of microcontinents and volcanic archipelagos were significant in shaping the Ordovician planet and the evolution of its biotas, associated with an immense biodiversification, significant fluctuations in climate and sea levels, and the first Phanerozoic mass extinction of marine invertebrates. The period was unique in being thalassocratic; epicontinental seas had a wider reach than during any other geological period. The land areas were restricted to isolated microblocks of archipelagos of various sizes with low relief, with rivers traversing gentle gradients, carrying sparse terrigenous material seaward. It is an ancient world with few parallels elsewhere in the Phanerozoic, and little in common with Holocene ecosystems and environments. The Ordovician System was introduced by Charles Lapworth as a solution to the stratotypes of overlapping units loosely defined by Adam Sedgwick for the Cambrian and by Roderick Murchison for the Silurian. Following a period of intensive research into all the key regions of the globe, unit stratotypes in the type areas of England and Wales have been replaced by seven global stages and three series based on Global Boundary Stratotype Sections and Points, enhancing the definition of these chronostratigraphic units and facilitating global correlation. As a consequence, the biological and geological events during the period can be recognised, and the magnitude and significance of originations and extinctions understood. A global synthesis of successions in Europe (Geological Society, London, Special Publications, 532) and the rest of the world (Geological Society, London, Special Publications, 533) has emphasised the importance of a universal language for Ordovician chronostratigraphy and its dividends. [ABSTRACT FROM AUTHOR]

One of the key objectives of the studies proposed by the Ordovician Subcommission is the improvement of regional stratigraphy for further advancements in global correlation. The results of this work can be found in numerous updates and reviews published in the recent Geological Society, London, Special Publications ‘A Global Synthesis of the Ordovician System’. Several of these papers refer to the Baltic Ordovician conodont biozones. While different schemes share many common features, their correlation with stages and biozones differ in detail. Considering the recent developments in the studies of the Sandbian stratigraphy in the Baltoscandian region, it is possible to complement the current conodont biozonation. Pygodus anserinus, Amorphognathus tvaerensis and A. superbus conodont zones are recognized in the Sandbian Stage in Baltica. The lower boundary of the stage is located within the Pygodus anserinus Zone, and the main part of the stage corresponds to the Amorphognathus tvaerensis Zone. In Scandinavia, the upper boundary of the stage correlates with a level within the A. superbus Zone or lies in a conodont-poor interval in the eastern Baltic region. The lower boundary of the A. inaequalisSubzone is tentatively correlated with the base of the Sandbian in Scandinavia but is located in the uppermost Darriwilian in the eastern Baltic region. In both areas, the A. tvaerensis Zone is subdivided into the Baltoniodus variabilis, B. gerdae and B. alobatus conodont subzones. The A. inaequalis Subzone – in some cases indicated as a zone – has been included in the regional stratigraphic charts for more than a decade. However, so far, A. inaequalis (Rhodes) has been reliably identified and also illustrated only from Avalonia, i.e. outside the palaeocontinent Baltica. A recent restudy of collections from the Fjäcka main section and the Smedsby Gård drillcore (both from Sweden), as well as from several Estonian sections, did not prove the occurrence of A. inaequalisin these areas. The A. tvaerensis Zone comprises almost the whole Sandbian, both in Scandinavia and the eastern Baltic areas. During this long age, the morphology of the P and M elements of A. tvaerensis (Bergström) gradually changed, and elements of distinct morphology appeared and were assigned to a new species, Amorphognathus viirae Paiste, Männik et Meidla, 2022, in the upper part of the range of the species. In succession, A. viirae appears in the upper part of the B. gerdae Subzone. Cur­rently, A. viirae has been identified in numerous Estonian sections, as well as in the Fjäcka main section and the Smedsby Gård drillcore in Sweden. Based on published figures, it occurs evidently in the Mójcza Formation of the Holy Cross Mountains (Poland) and the Black Knob Ridge section in Oklahoma (USA), in the GSSP for the base of the Katian Stage. A. inaequalis has also been reported and an eponymous zone identified in two other sections located on the palaeocontinent Baltica, in the Bliudziai-150 drillcore (Lithuania) and the Kovel-1 drillcore (Ukraine). During the restudy of collections from these sections, no elements of A. inaequalis were found in either of them. The earliest recorded elements of the genus Amorphognathus have been assigned to A. tvaerensis, and the specimens from the upper range of this species reidentified as A. viirae. Analysis of the new material and revision of previous collections has revealed problems related to the Sandbian conodont biozonation of the palaeocontinent Baltica and demonstrated the need for its updating. The new proposed zonation excludes the A. inaequalis Subzone, as the occurrence of its nominal taxon on the palaeocontinent Baltica could not be proved. Additionally, a new unit, the A. viirae Zone, has been included in the zonation. It corresponds to the upper part of the former B. gerdae Subzone, which is now treated as a zone. Also, all subzones based on the succession of Baltoniodus species have been elevated to the rank of zones. [ABSTRACT FROM AUTHOR]

The early Palaeozoic order Ascocerida is a group of morphologically unique and rare cephalopods known from the Ordovician and Silurian rocks of Avalonia, Baltica, Laurentia and Perunica. The limited Estonian record of Silurian ascocerids is complemented with a specimen from the Pähkla locality (Island of Saaremaa; Paadla Regional Stage, Ludlow Series) representing the stratigraphically oldest known occurrence of ascocerids in the Silurian of Estonia. The strata that were formerly exposed in Pähkla are likely correlated to the Hemse Group of the Island of Gotland (Sweden) having a remarkable record of ascocerids. The appearance of Silurian ascocerids in Estonia is confined to a time interval when the group had the highest species diversity and the widest geographic dispersion, reaching also outside Baltica for the first time. [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.)

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]