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- Dahlqvist, Peter, et al.
(author)
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Late Ordovician shelly faunas from Jamtland: palaeocommunity development along the margin of the Swedish Caledonides
- 2010
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In: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 85:3, s. 505-512
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Journal article (peer-reviewed)abstract
- Late Ordovician shelly faunas occur at several localities in the Ostersund area of Jamtland (Sweden) and developed against a background of intense and rapid global climate change. In the eastern part, approximately in the middle parts of the Krykas Quartzite, and in the western part in the uppermost Kogsta Siltstone changes in faunas and sedimentary patterns provide regional evidence of these global events. In both areas the faunas occur in shale and siltstone facies and are used to effect correlations between the eastern and western parts of the region, which show major differences in facies development. These sub-basins, situated on the margins of a developing mountain belt, reacted differently to global signals providing further evidence of the heterogeneous responses to climate change at the end of the Ordovician Period.
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- Kiipli, Tarmo, et al.
(author)
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Wenlock bentonites in Lithuania and correlation with bentonites from sections in Estonia, Sweden and Norway
- 2008
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In: GFF. - 2000-0863. ; 130:4, s. 203-210
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Journal article (peer-reviewed)abstract
- Seven Wenlock bentonite beds from four drill cores in Lithuania with sufficient thickness for sampling were analysed by XRD and XRF. The sanidine composition of bentonites combined with graptolite biozonation of the host rock were used for correlations. Two of the studied bentonite samples at the antennularius/flexilis biozone boundary can be confidently correlated between two Lithuanian sections. Four of the studied bentonites can be correlated with lower or higher probability with earlier studied bentonites in Estonia and Sweden. Identification of the Grotlingbo Bentonite in the Vidukle-61 drill core, and descriptions of other east Baltic sections enables composition of it thickness map of the Grotlingbo Bentonite. The thickness pattern with two axes, and the layered composition of the Grotlingbo Bentonite, indicate a change of the wind direction during a long lasting eruption. Hypothetical location of the volcanic source in the Silurian was within the zone of the Baltica-Laurentia collision.
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