Abstract In the central part of the Mid-Ordovician–Early Silurian Baltic Basin, two different tra... more Abstract In the central part of the Mid-Ordovician–Early Silurian Baltic Basin, two different transport pathways of terrigenous material can be recognized. Kaolinite indicates the south-to-north sediment influx, and Cr the western and northern sources. A pathway from the Ukrainian Shield in the South was active in the Floian–Darriwilian (Ordovician) and in the Llandovery (Silurian). The influx from the western source was active in the Sandbyan, and influx from the northern side occurred in the Katyan. The sediment transport was carried ...
The present study deals with the possibilities of applying the zircon saturation thermometry, whi... more The present study deals with the possibilities of applying the zircon saturation thermometry, which is based on the equilibrium between the zircon crystals and the melt, to strongly altered volcanic ashes—bentonites. It proposes an alternative to a widely used method of calculating magma temperature from Zr content and major component composition (Boehnke in Chem Geol 351:324–333, 2013), that is not suitable for bentonites, as most of the major components have been largely altered in these rocks. For calculating source magma temperatures in strongly altered volcanic ashes, the exponential function from the Zr (ppm)/Al 2 O 3 (%) ratio with compositional corrections from the TiO 2 /Al 2 O 3 ratio was found applicable. The idea to use the ratios of these elements is based on the low mobility of these elements in the earth's surface conditions. Temperatures of magma, forming in the partial melting process, are assessed from the bulk rock composition. Pre-eruption temperatures were estimated from the composition of fine fractions of bentonites. The accuracy of the new method was established from comparison with the method by Boehnke et al. (Chem Geol 351:324–333, 2013). The difference between the two methods was mostly less than ± 30° to ± 50°. The comparison with the magma temperature, estimated from the sanidine composition, revealed 13° lower values on average. Although the proposed method for estimating the source magma temperatures is less precise than the method of accounting for detailed rock compositions, it can be used in strongly altered rocks, where other methods are not usable. The new method still enables differentiation between felsic source magmas originating at low or high temperatures. Early Palaeozoic bentonites in the Baltic Basin can be divided, according to the source magma temperatures, into two types: (1) Low temperature (650–790 °C), containing potassium-rich sanidine and abundant biotite (S type), (2) high temperature (770–850 °C) with sodium-rich sanidine and scarce biotite (I type).
Abstract. Study of volcanic ash beds using biostratigraphy, sanidine composition and immobile ele... more Abstract. Study of volcanic ash beds using biostratigraphy, sanidine composition and immobile elements within bentonites has manifested several well-established and some provisional correlations between Gotland and East Baltic sections. Energy dispersive X-ray fluorescence microanalysis of phenocrysts has revealed bentonites containing Mg-rich or Fe-rich biotite. Sanidine phenocrysts contain, in addition to a major Na and K component, often a few per cent of Ca and Ba. On the basis of new correlations the mapping of the ...
Abstract. The major oxide and trace element compositions of seven sedimentary rock reference samp... more Abstract. The major oxide and trace element compositions of seven sedimentary rock reference samples (claystone, organic-rich argillite, 2 limestones, dolostone, sandstone and feldspathized volcanic ash) are presented. Among studied samples the organic rich argillite (“dictionema shale”) is conspicuouse, exhibiting wide range of chemical elements with higher contents than in common sedimentary rocks.
Abstract Silurian bentonites from Sweden and the eastern Baltic are correlated using XRD analysis... more Abstract Silurian bentonites from Sweden and the eastern Baltic are correlated using XRD analysis of sanidine composition. Identifying the same bentonite in different sections has constrained correlations between the conodont, graptolite and chitinozoan zonations. Three bentonites correlate the Cyrtograptus murchisoni Zone with the upper part of the Pterospathodus amorphognathoides Zone and both the Lower and the Upper Pseudooneotodus bicornis conodont biozones at their type locality. Thus the base of the ...
The sedimentary sequence of the Palaeozoic Baltic Basin contains numerous bentonite layers whose ... more The sedimentary sequence of the Palaeozoic Baltic Basin contains numerous bentonite layers whose composition is dominated by the mineral assem- blage of illite-smectite-K-feldspar-kaolinite. The contents of these minerals may vary between in- dividual bentonite layers as well as laterally from almost pure illite-smectite to K-feldspar and/or kaolinite end-member compositions, but the assem- blage remains principally the same. In this respect the bentonites of the Upper Ordovician Ashgill Pirgu (Regional) Stage are exceptional and unique in the Baltic Basin. The clay mineral composition of these bentonites is characterized by the chlorite- smectite (corrensite) and illite-smectite assemblage. The micritic-bioclastic to argillaceous limestones of Pirgu age in the northern Baltic Basin include up to three (four?) individual bentonite beds, all of which contain chlorite-smectite and/or corrensite miner- als. In this contribution we present preliminary data on the clay mineral compositio...
The Silurian was characterised by severe environmental perturbations recorded in lithological seq... more The Silurian was characterised by severe environmental perturbations recorded in lithological sequences as rapid facies changes, extensive gaps (particularly in shallow water regions) (Jeppsson et al. 1994), extinctions of biota (Kaljo et al. 1995) and isotopic variations (Kaljo et al. 1997, 1998). Climatic changes and oceanic circulation overturns have been considered to be the causes of these variations (Jeppsson 1990, 1993; Jeppsson et al. 1995; Samtleben et al. 1996; Bickert et al. 1997). Tillites from multiple glaciations (the youngest of them dated as latest Telychian to earliest Sheinwoodian) are recorded in the Llandovery in Brazil (Grahn & Caputo 1992; Caputo 1998). In order to study and understand the nature of ancient environmental changes, detailed correlation of sections is essential. Without this, the true succession of events (e.g. extinctions of various faunal groups, isotopic anomalies, and sea-level fluctuations) is not possible to ascertain. In the present paper, ...
Seventy-seven Telychian bentonite samples from six drill-core sections were correlated on the bas... more Seventy-seven Telychian bentonite samples from six drill-core sections were correlated on the basis of their sanidine composition. In total, bentonites from 43 volcanic eruptions, of which six are new discoveries, were established in the Telychian of Estonia. Names and identification (ID) codes were assigned to the bentonites. The different distribution patterns of volcanic ash thicknesses indicate different source volcanoes. Lack of several bentonites near the transition between the Rumba and Velise formations and at the Llandovery-Wenlock boundary indicates sedimentary hiatuses in the eastern part of the studied area.
Abstract In the central part of the Mid-Ordovician–Early Silurian Baltic Basin, two different tra... more Abstract In the central part of the Mid-Ordovician–Early Silurian Baltic Basin, two different transport pathways of terrigenous material can be recognized. Kaolinite indicates the south-to-north sediment influx, and Cr the western and northern sources. A pathway from the Ukrainian Shield in the South was active in the Floian–Darriwilian (Ordovician) and in the Llandovery (Silurian). The influx from the western source was active in the Sandbyan, and influx from the northern side occurred in the Katyan. The sediment transport was carried ...
The present study deals with the possibilities of applying the zircon saturation thermometry, whi... more The present study deals with the possibilities of applying the zircon saturation thermometry, which is based on the equilibrium between the zircon crystals and the melt, to strongly altered volcanic ashes—bentonites. It proposes an alternative to a widely used method of calculating magma temperature from Zr content and major component composition (Boehnke in Chem Geol 351:324–333, 2013), that is not suitable for bentonites, as most of the major components have been largely altered in these rocks. For calculating source magma temperatures in strongly altered volcanic ashes, the exponential function from the Zr (ppm)/Al 2 O 3 (%) ratio with compositional corrections from the TiO 2 /Al 2 O 3 ratio was found applicable. The idea to use the ratios of these elements is based on the low mobility of these elements in the earth's surface conditions. Temperatures of magma, forming in the partial melting process, are assessed from the bulk rock composition. Pre-eruption temperatures were estimated from the composition of fine fractions of bentonites. The accuracy of the new method was established from comparison with the method by Boehnke et al. (Chem Geol 351:324–333, 2013). The difference between the two methods was mostly less than ± 30° to ± 50°. The comparison with the magma temperature, estimated from the sanidine composition, revealed 13° lower values on average. Although the proposed method for estimating the source magma temperatures is less precise than the method of accounting for detailed rock compositions, it can be used in strongly altered rocks, where other methods are not usable. The new method still enables differentiation between felsic source magmas originating at low or high temperatures. Early Palaeozoic bentonites in the Baltic Basin can be divided, according to the source magma temperatures, into two types: (1) Low temperature (650–790 °C), containing potassium-rich sanidine and abundant biotite (S type), (2) high temperature (770–850 °C) with sodium-rich sanidine and scarce biotite (I type).
Abstract. Study of volcanic ash beds using biostratigraphy, sanidine composition and immobile ele... more Abstract. Study of volcanic ash beds using biostratigraphy, sanidine composition and immobile elements within bentonites has manifested several well-established and some provisional correlations between Gotland and East Baltic sections. Energy dispersive X-ray fluorescence microanalysis of phenocrysts has revealed bentonites containing Mg-rich or Fe-rich biotite. Sanidine phenocrysts contain, in addition to a major Na and K component, often a few per cent of Ca and Ba. On the basis of new correlations the mapping of the ...
Abstract. The major oxide and trace element compositions of seven sedimentary rock reference samp... more Abstract. The major oxide and trace element compositions of seven sedimentary rock reference samples (claystone, organic-rich argillite, 2 limestones, dolostone, sandstone and feldspathized volcanic ash) are presented. Among studied samples the organic rich argillite (“dictionema shale”) is conspicuouse, exhibiting wide range of chemical elements with higher contents than in common sedimentary rocks.
Abstract Silurian bentonites from Sweden and the eastern Baltic are correlated using XRD analysis... more Abstract Silurian bentonites from Sweden and the eastern Baltic are correlated using XRD analysis of sanidine composition. Identifying the same bentonite in different sections has constrained correlations between the conodont, graptolite and chitinozoan zonations. Three bentonites correlate the Cyrtograptus murchisoni Zone with the upper part of the Pterospathodus amorphognathoides Zone and both the Lower and the Upper Pseudooneotodus bicornis conodont biozones at their type locality. Thus the base of the ...
The sedimentary sequence of the Palaeozoic Baltic Basin contains numerous bentonite layers whose ... more The sedimentary sequence of the Palaeozoic Baltic Basin contains numerous bentonite layers whose composition is dominated by the mineral assem- blage of illite-smectite-K-feldspar-kaolinite. The contents of these minerals may vary between in- dividual bentonite layers as well as laterally from almost pure illite-smectite to K-feldspar and/or kaolinite end-member compositions, but the assem- blage remains principally the same. In this respect the bentonites of the Upper Ordovician Ashgill Pirgu (Regional) Stage are exceptional and unique in the Baltic Basin. The clay mineral composition of these bentonites is characterized by the chlorite- smectite (corrensite) and illite-smectite assemblage. The micritic-bioclastic to argillaceous limestones of Pirgu age in the northern Baltic Basin include up to three (four?) individual bentonite beds, all of which contain chlorite-smectite and/or corrensite miner- als. In this contribution we present preliminary data on the clay mineral compositio...
The Silurian was characterised by severe environmental perturbations recorded in lithological seq... more The Silurian was characterised by severe environmental perturbations recorded in lithological sequences as rapid facies changes, extensive gaps (particularly in shallow water regions) (Jeppsson et al. 1994), extinctions of biota (Kaljo et al. 1995) and isotopic variations (Kaljo et al. 1997, 1998). Climatic changes and oceanic circulation overturns have been considered to be the causes of these variations (Jeppsson 1990, 1993; Jeppsson et al. 1995; Samtleben et al. 1996; Bickert et al. 1997). Tillites from multiple glaciations (the youngest of them dated as latest Telychian to earliest Sheinwoodian) are recorded in the Llandovery in Brazil (Grahn & Caputo 1992; Caputo 1998). In order to study and understand the nature of ancient environmental changes, detailed correlation of sections is essential. Without this, the true succession of events (e.g. extinctions of various faunal groups, isotopic anomalies, and sea-level fluctuations) is not possible to ascertain. In the present paper, ...
Seventy-seven Telychian bentonite samples from six drill-core sections were correlated on the bas... more Seventy-seven Telychian bentonite samples from six drill-core sections were correlated on the basis of their sanidine composition. In total, bentonites from 43 volcanic eruptions, of which six are new discoveries, were established in the Telychian of Estonia. Names and identification (ID) codes were assigned to the bentonites. The different distribution patterns of volcanic ash thicknesses indicate different source volcanoes. Lack of several bentonites near the transition between the Rumba and Velise formations and at the Llandovery-Wenlock boundary indicates sedimentary hiatuses in the eastern part of the studied area.
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