Body fossil assemblages from the Lower Idzików Beds (Coniacian) in the Upper Nysa Kłodzka Graben, south-west Poland: Preliminary taphonomic, palaeoecological and palaeogeographical data

Abstract

From mudstones and sandstones referred to as the Lower Idzików Beds, as exposed at Stary Waliszów (Upper Nysa Kłodzka Graben, south-west Poland), a rich assemblage of body fossils has been recovered. This comprises rare ammonites (Baculites incurvatus, Forresteria cf. petrocoriensis, ?Scalarites sp.), nautiloids (Anglonautilus sinuatoplicatus), numerous bivalves, inclusive of inoceramids such as Inoceramus frechi and Volviceramus involutus, oysters (Ceratostreon, Vultogryphaea and Hyotissa) and other common genera such as Scabrotrigonia, Protocardia, Cucullaea, Neithea, Pinna, Liopistha, Panopea and Goniomya. Gastropods include mainly aporrhaids, turritellids, naticids and ampullinids. Echinoids are rare and comparatively poorly preserved, comprising only irregular forms (cardiasterids, micrasterids and hemiasterids), some of them being recorded from the Upper Cretaceous of Poland for the first time. Decapod crustaceans are fairly abundant in the Lower Idzików Beds, with axiideans predominating. A taphonomic analysis shows that this assemblage is well preserved, suggesting rapid burial as a result of storm events, while a palaeoecological assessment of taxonomic composition and trophic modes implies that deposition took place in a shallow-marine, well-oxygenated environment with a soft-bottom substrate, rich in nutrients and close to the fair-weather wave base. The presence of stenohaline taxa such as ammonites and echinoderms provides evidence of normal salinity.