Parvamussium fallax (KOROBKOV) in the Padrag Marl in the vicinity of Csabrendek and Gyepükaján

Abstract

The species Parvamussium fallax KOROBKOV occurs in medium quantities in the lower, so-called Csabrendek Marl Member of the Padrag Marl Formation transected by wells in the surroundings of Csabrendek and Gyepükaján (S Bakony, Hungary). The Member is made up of marl and calcareous marl beds. According to literary data the species – which occurs both in the late Eocene and in the early Oligocene – can be found in this area in beds representing the upper part of the middle Eocene (Bartonian stage). Thus, its stratigraphic distribution is wider than it was previously known. Its position in the succession, i.e. its occurrence in glauconite-poor marls and calcareous marls (above the glauconitic beds comprising molluscs of shallow and middle sublittoral facies and below the pelagic beds characterised by planktonic foraminifers in large numbers) indicates that the species dwelt in the deep sublittoral zone, at the boundary of the shelf and the slope. It is not an age-indicator species; however, it is an indicator of facies.
The publication reveals the Hungarian aspects of the taxon. The species was first depicted by HOFMANN (1873) under the name of Pecten bronni MAYER. Its first description was published by LŐRENTHEY (1911). H, they did not recognise that the characteristics of the specimens found in the Buda Hills differ from those of the taxon Pecten bronni MAYER. The latter was classified by KOROBKOV (1937) into a new species discovered by him i.e. the Variamussium fallax KOROBKOV. He considered Hofmann’s drawings (HOFMANN 1873. Plate XIV: Figure 1) as the first depiction of the species.