Sedimentary record of subaerial volcanic activity in the basal Ordovician shoal-marine deposits: the Trenice Formation of the Prague Basin, Bohemian Massif, Czech Republic
Abstrakt
The basal Ordovician Třenice Formation represents an initial member of preserved (in)fill of the Prague Basin. Volcanic admixture in sediments preserved within the south-western part of the basin suggests an activity of subaerial volcanism during the deposition of the Třenice Formation sediments.
Three principal lithofacies associations were defined within a sedimentary record of the Třenice Formation based on petrography and observed sedimentary structures: i) graded conglomerates, ii) lithic sandstones and iii) volcanigenic deposits. Studied sediments deposited in form of sand dunes commonly interbedded with volcaniclastics are supposed to be deposited at the marine shoreface with influence of ebb-tide currents.
The volcaniclastic intercalations are interpreted as a record of debris flows, hyperconcentrated currents and turbidity currents that resedimented volcaniclastic material derived originaly from subaerial Křivoklát-Rokycany and Strašice volcanic complexes.