Detrital record of Early Palaeozoic and Devonian clastic sediments at the southwestern border of the Fennoscandian Shield - provenance signals for a Caledonian geodynamic evolution

Early Palaeozoic and Devonian elastic sediments along the southern border o f the Fennoscandian Shield were studied by sedimentary petrography, heavy m ineral analysis and mineral chemistry of detrital components. The detrital record of Lower Cambrian sandstones of Bornholm and the well G 14 reflect a crystalline basement source composed of high-grade gneisses and granitoid intrusions which characterise a Baltican provenance. The detrital compositi on of Ordovician elastic sediments of the Rugen boreholes is different and defines a Peri-Gondwanan provenance. As the Peri-Gondwanan realm experience d subduction and an active continental margin stage in the Middle/Upper Ord ovician, the elastic record reflects predominantly an ophiolite and magmati c arc source. During the Silurian, mixing of both provenances is evident. I t implies the complete closure of the Tornquist Ocean and the detrital infl ux from both source areas in a Caledonian foreland basin. Exhumation, erosi on and recycling of Caledonian tectonometamorphic source areas is only refl ected by the Lower/Middle Devonian Old Red molasse sediments. The detrital record clearly supports the predominant derivation from the adjacent Danish -N-German-Polish Caledonian foldbelt. Thus, a complete Caledonian orogenic cycle is documented in the detrital record of Early Palaeozoic and Devonian elastic sediments at the southwestern border of Baltica. In combination wi th recent palaeontological, geochronological and structural results, it fur ther substantiates the geodynamic evolution of the Rugen Caledonides.