Paleośrodowisko margli kredowych w Tatrach Polskich w świetle badań ichnologicznych

Abstract

PALEOENVIRONMENT OF THE CRETAEEOUS MARLSTONES IN THE POLISH TATRA MTS IN THE LIGHT OF ICHNOLOGICAL RESEAREHES Summary Basinal marlstones and micritic limestones of the Kościeliska Marl Formation (Berriasian-Valanginian-?Lower Aptian) and partially turbiditic marly mudstones of the Zabijak Marlstone Formation (Lower Albian-Turonian) in the Tatra Mts. are heavily bioturbated. Trace fossil assemblages are dominated by Chondrites, Trichichnus, Pianolites , and ?Thalassinoides. Phycosiphon, Taenidium, Skolithos, Palaeophycus, ?Teichichnus and Scolicia occur rarely. These ichnotaxa indicate burrowing activity of deposit-feeding crustaceans, irregular echinoids, and deposit-feeding of chemosymbiontic polycheates and/or ?sipunculoids. Composite ichnofabrics indicate welI-oxygenated sediments, in which burrowers occupied well-defined tiers determined on the basis of cross-cutting relationships of trace fossils. The deepest tier is occupied by Trichichnus, the shalIower tier by Chondrites, and the more shallower tiers by the remaining ichnotaxa. Commonly, parting and bedding surfaces are discordant, owing to tectonic stress. Bedding is well indicated by ichnofabrics. The trace-fossil assemblages have not good counterpart among the classic ichnofacies. They resemble trace-fossil assemblages from marly mudstones of the Marnoso-arenacea Formation and associated facies (Miocene) in the Northern Apennines, which represent moderately oligotrophic, well oxygenated deep-sea environments.