Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 14. 1989. (Budapest, 1989)

FRAGMENTA MINERALOGICA ET PALAEONTOLOGICA 14. BUDAPEST, 1989 p. 4142 A survey of the Aptian Brachiopoda from the Northern Bakony Mountains (Hungary) By Á.SOMODY (Received November 29, 1988) Abstract: Description of 17 species of Brachiopoda from four localities (Közöskuti-árok, Szilas-árok, Bocskor-hegy, Eperkés-hegy) in the Northern Bakony Mts., Hungary is given. 572 specimens were collected from the basal horizon of the Aptian crinoidal limestone (Tata Formation). According to pétrographie and taphonomic studies, the crinoidal limestone was formed in a basin of varied morphology. The majority of brachiopods can not be found in their sites of life, they suffered redistribution. The fauna closely resembles that of the Caucasus, Sardinia and the Jura region. INTRODUCTION The Bakony Mountains is one of the best known geological units of Hungary. The study of its Mesozoic formations provided geological and palaeontological data known all over the world. However, some groups of fossils, such as the Aptian brachiopods, have not been accurately studied so far. The preserving rock is a grey crinoidal limestone, which is quite unknown in the Aptian of the surrounding area. It rests unconformably on older rocks. Hungarian geologists of the 19th and the early 20th centuries (KOCH 1875, SCHAFARZIK 1890, BÖCKH 1909) described this crinoidal limestone as Tithonian. The correct stratigraphie position and the detailed description of the formation was given by NOSZKY (1934) and WEIN (1939). NOSZKY remarks that especially in the deeper norizons, compressed shells of rhynchonellids and terebratulids can be found. The accurate study of the Tata Limestone Formation was carried out by FÜLÖP (1964). According to the cephalopod fauna found in the Márványbánya (Zirc), he determined the age of the formation as Aptian. Faunal lists of brachiopods identified by A. HORVÁTH were also published there. It soon became clear that as the material I collected was poorly preserved, the determination of several forms would be rather uncertain. The majority of the specimens were disarticulated shells, a lot of them were dissolved and compressed. Due to the bad preservation, I could not make transverse sections of some genera. Ignorance of the internal struc tures made the determination even more difficult and uncertain. LOCALITIES The Aptian crinoidal limestone is a widely distributed formation in the Transdanubian Mts., overlying older rocks unconformably. It is formed of crinoid ossicles of different size often displaying cross-bedding. It also contains extraclasts of different size, originating from the older surrounding rocks (LELKES 1985). The colour of the rock is grey, greyish