Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 19. 2001. (Budapest, 2001)

2 Vö Figure 1 — The location of the Aszófő section. as a result of submarine gravity sliding and resedimentation. The most common elements of the fauna are the brachiopods, but ammonites (Balatonites balatonicus) and thick-shelled gastropods and bivalves are also frequent. After this phase of redeposition, a more quiet, basinal sedimentation follows. The dark-grey or darkbrown, well-bedded, sometimes laminated limestone is highly bituminous. The fauna is markedly different from the previous one. The ammonite assemblage is extremely rich (Balatonites, Norites, Beyrichites, Proavites, Ptychites, etc.); in addition, small, thin-shelled burrowing bivalves (Palaeoneilo, Solemya, Unionites) are rather common. Around Bed 1/43 this type of fauna gradually disappears and through 1—2 metres only Posidonia and Daonella can be found in rock-forming quantity. The undisturbed "pavements" made by the flat shells of these pelagic bivalves, the absence of benthos and bioturbation indicate anaerobic bottom conditions. Higher up the limestone becomes nodular and cherty. This part contains rare and poorly preserved ammonites (Bulogites, Beyrichites). This "Reifling-type" limestone is exposed in the uppermost few metres in the trench, but it can be traced in the detritus up in the hillside in more than 50 m thickness. The section was subdivided on the basis of ammonites (VÖRÖS 1987, TATZREITER Sc VÖRÖS 1991; !, A. see also for detailed description and logs). The boundary between the Balatonicus and Trinodosus Zones, i.e. the Pelsonian/Illyrian boundary, can be drawn between Beds 1/88 and 89. The Balatonicus Zone can be further subdivided: the whole sequence exposed in Trench II, and Beds 1—43 of Trench I. belong to the Balatonicus Subzone; Beds 1/59-88 to the Zoldianus Subzone. After all, the Aszófő section is a very important reference section for Pelsonian ammonite biostratigraphy and is the best, though not perfect, candidate for being the type section of the Pelsonian Substage. Figure 2 Stratigraphie columns of the two trenches (I. and II.) of the Aszófő section (after TATZREITER & VÖRÖS 1991) and the frequency distribution of ammonoid and nautilid specimens. Material The Aszófő section yielded a relatively rich, but not Anoploceras cf. rollieri (ARTHABER, 1896) very well-preserved nautilid fauna. From the 38 Encoiloceras balatonicum sp. n., specimens, representing the Nautilida, the following 10 Encoiloceras lajosi sp. n., species were determined: Mojsvaroceras ? cf. binodosum (HAUER, 1887)