Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 20. 2002. (Budapest, 2002)

FRAGMENTA PALAEONTOLOGICA HUNGARICA 20, BUDAPEST, 2002 New data to the stratigraphy of the Pelsonian Substage at Köveskál (Middle Triassic, Balaton Highland, Hungary) by Attila VÖRÖS & József PÁLFY Abstract — New excavation and fossil collection at the classical Middle Triassic locality of Horog-hegy (Köveskál, Balaton Highland, Hungary) revealed that a nearly 40 m thick sequence of the Felsőörs Limestone Formation represents the Pelsonian and Illyrian Substages. Within the Balatonicus Zone, the Balatonicus Subzone, the Zoldianus Subzone and a third, unnamed subzone are proved by detailed collections; the Trinodosus and Pseudohungaricum Subzones of the Trinodosus Zone have been inferred from ammonoids found in loose blocks. Brachiopod limestone ("Recoaro" limestones, or Horoghegy Member) appears in two distinct horizons: in the Balatonicus Subzone and at the top of the Zoldianus Subzone. These two horizons were correlated with "Recoaro" beds at other, well-dated sections of the Balaton Highland (Aszófö, Felsőörs). The synchronous and repeated appearance of brachiopod shell beds in the basinal sequences is interpreted as reflecting local tectonic episodes related to the fragmentation of the Anisian platforms. The first phase may correspond to the first differentiation episode of the formerly uniform Megyehegy platform or ramp, i.e. the birth of the isolated platforms (e.g. Tagyon platform) in the Balatonicus SubChron. The second phase may be connected to the progressive fragmentation and demise of the platforms at the Balaton Highland at the end of the Zoldianus SubChron. Key words: lithostratigraphy, biostratigraphy, ammonoids, brachiopods, Middle Triassic, Balaton Highland, Hungary. VÖRÖS, A. & PÁLFY, J. (2002): New data to the stratigraphy of the Pelsonian Substage at Köveskál (Middle Triassic, Balaton Highland, Hungary) — Fragmenta Palaeontologica Hungarica, 20: 53-60. Introduction The village of Köveskál has a well-established name in the Triassic literature. It was first mentioned in the early report by ZEPHAROVICH (1856) and it lent its name to the brachiopod species " Spiriferina" koeveskalyensis (STUR, 1865), and subsequently the genus Koeveskallina DAGIS (see SlBLIK, 1970, 1972). All these records refer to a small hill called Horog-hegy (or Mezőmái in the earlier literature), two kilometres east of the village, where Middle Triassic limestones were quarried in small pits. BÖCKH (1873) described the fundamental geological features of the locality. In the northward dipping sequence, he distinguished a basal, platy limestone overlain by a dolomite that forms the hill top, followed by brachiopod limestone ("Recoaro" limestone) and bituminous, platy limestone, and, finally, the grey "Reifling" limestone. BÖCKH (1873) listed a rich brachiopod fauna from the "Recoaro" limestone and observed that "Ammonites balatonicus" occurred both in the brachiopod limestone and in the bituminous, platy limestone; whereas the "Reifling" limestone was characterised by "Arcestes Studeri" and "Ceratites binodosus"

. DIENER (1899, 1900) and ARTHABER (1903) provided additional data about the ammonoid fauna and emphasized that the upper ammonoid level corresponded to the trinodosus horizon. LÓCZY (1913, 1916) drew a sketchy but informative geological profile of the Horog-hegy. The recent stratigraphical reviews (e.g. BALOGH et al. 1983, CRÛS & SZABÓ 1984) merely summarised the results of previous authors. As part of a detailed study of the Anisian brachiopods from the Balaton Highland, PÁLFY (1986, 1991) made new collections at the locality. He recognised that two different types of "Recoaro" limestone occurred: a reddish-brown and another, grey, bituminous, siliceous, organodetrital limestone, but their stratigraphical relationship remained unclear. The present study on the stratigraphy of the Horog-hegy at Köveskál is part of an ongoing research project aimed at the definition of the Pelsonian Substage at the Balaton Highland. The figured specimens are deposited in the Geological and Palaeontological Department of the Hungarian Natural History Museum.