| Popis: |
The Frasnian carbonate-siliciclastic deposits of the Stipinai Formation exposed in two quarries at Petrašiūnai and Klovainiai (northern Lithuania) show considerable vertical facies changes. The lower part of this succession is dominated by argillaceous dolomitic facies with subordinate fine siliciclastic deposits. They display haloturbation and bioturbation structures, represent a hypersaline lagoonal environment, and record the beginning of the transgression. The middle part of the succession consists of secondary dolostones containing moulds of brachiopods, tetracorals, stromatoporoids and trace fossils of deposit feeders; these were deposited in a shallow subtidal marine environment and represent the deepest sedimentary environment of this succession. This was followed by a lagoonal environment (episodic hypersaline), represented by dolomudstones and marly dolomudstones. The upper part of the succession is built of bedded dolostones which document a shallowing trend. Intercalations of clays and palaeosol horizons record emergence events. Palynostratigraphic data tentatively indicate that the Stipinai Formation represents the Upper Frasnian. The succession can be interpreted as a record of the upper part of a T-R cycle (related to the semichatovae transgression) in the Main Devonian Field of the East European Platform. The Stipinai Formation is distributed across western and central Latvia and has a correlative in the Pomerania Basin (northern Poland). |
