Tidal facies in the Upper Silurian Oved-Ramsåsa Group of Scania, Sweden: Linkages of radial and cerebroid ooids and evaporite tracers to subtidal, lagoonal environment
Titel:
Tidal facies in the Upper Silurian Oved-Ramsåsa Group of Scania, Sweden: Linkages of radial and cerebroid ooids and evaporite tracers to subtidal, lagoonal environment
Auteur:
Wigforss-Lange, Jane
Verschenen in:
GFF
Paginering:
Jaargang 129 (2007) nr. 1 pagina's 7-16
Jaar:
2007-03-01
Inhoud:
A sequence in the Upper Silurian Oved-Ramsåsa Group in Scania, Sweden has been investigated sedimentologically and geochemically. This sequence represents a regressive marine succession. The sedimentary structures and the rapid vertical changes in lithologies and the lateral variability of beds indicate a tide-dominated sedimentation in a shallow epeiric sea, where even small oscillations in sea water level and water energy affected sedimentation. The succession of facies shows an upward transition from open marine shallow subtidal/intertidal to lagoonal subtidal/intertidal conditions. These facies changes are accompanied by faunal changes and shifts in major and trace element concentrations. Of particular interest are the presence of radial and cerebroid ooids and evaporite tracers. The radial fabric of the ooids is regarded as primary and it is suggested that these ooids formed in suspension, in the low-energy subtidal lagoonal environment. Implications for a restriction in water circulation and progressive evaporation, coinciding with the ooid formation are seen in associated sediments of this facies. A salinity increase is demonstrated by the presence of BaSO4 and elevated values of MgO, NaO and Ba. A high Zr and SiO2 content, most probably derived from eolian dust, indicate increased aridity and a relative decrease of water transported clastics.
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