Bathymetry of the Carpathian Flysch Basin

Abstract

The environment in which the Carpathian flysch was deposited is here discussed. The views ascribing !its origin to paralic, littoral or neritic environment. Its are rejected on the basis of the sedimentary features and faunal evidence. Arguments are presented in favor of deposition from decelerating currents. This type of deposition is indicated by the sorting of mineral grains and fossils, an approximately positive correlation between the thickness and coarseness of beds and ·dimensions of erosional structures (flutes) on their soles, and a succession of structures in flysch sequences. Proximal, intermediate and distal deposition regions are characterized in each member of the succession. From the sedimentary features the conclusion is drawn that the Carpathian flysch was deposited at depths greater than the neritic zone. It is shown that the makrofauna contains 50 species of Foraminifera which in present-day seas live in waters with normal salinity. Most of these species display a marked preference for bathyal and abyssal depths. Several Foraminifera, closely related to modern deep-water species, also occur in the Carpathian flysch. The presence of calcareous Foraminifera in nearly an stratigraphic members excludes a deposition below the calcium carbonate compensation depth. Consequently, bathyal (mostly upper bathyal) depths are assigned to the Carpathian flysch basin, and changes in depths during the long deposition (uppermost Jurassic through Lower Miocene) are estimated tentatively. It has been found that the number of branched and patterned traced fossils is larger in the beds, to which greater depths are assigned on the basis of sedimentological and microfaunal evidence.