Stratigraphic position of alkaline volcanic rocks in the autochthonous cover of the high-tatric unit (Western Tatra Mts., Central Western Carpathians, Slovakia)

Abstract

Biostratigraphic investigations of carbonate strata that sandwich volcanic rocks and studies of the volcanic rocks were made along five composite lithological sections across the Upper Jurassic-Lower Cretaceous carbonate rocks of autochthonous cover of the High-Tatric Unit in the Osobita peak area of the Western Tatra Mts. A carbonate microbreccia that consists almost exclusively of limestone clasts containing calpionellids occurs immediately below the volcanics. The youngest identified microfossil Calpionella elliptica Cadisch in the individual limestone clasts showed the age of breccia formation to be youngerthan late Early-early Middle Berriasian. The volcanic rocks are overlain by the Osobita Limestone Formation, which in the lowermost horizons consists of a few metres thick crinoidal limestone containing the foraminifers Meandrospira favrei (Charollais, Bronnimann and Zaninetti), Sabaudia minuta Hofkerand Montsalevia salevensis (Charollais, Bronnimann and Zaninetti) indicating a Late Valanginian-Early Hauterivian age. The biostratigraphical and sedimentological data obtained show that volcanism took place in several phases. Less intense phases of volcanism are recorded as thin tuffitic laminae within the upper parts of the Tithonian-early Middle Berriasian Sobótka Limestone Member and as fragments of volcanic rock in the carbonate breccia. The main phase(s) of volcanism took place during the Late Berriasian-?Early Valanginian.