Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 24-25. 2007. (Budapest, 2007)
FRAGMENTA PALAEONTOLOGICA HUNGARICA 24—25, BUDAPEST, 2007 Jurassic brachiopods of the Transdanubian Range (Hungary); stratigraphical distribution and diversity changes by Attila VÖRÖS & Alfréd Du LAI Abstract — Several thousands brachiopod specimens have been collected from 7 different stages of the Jurassic in the Transdanubian Range (TR). The fauna shows a great diversification in the Hettangian to Pliensbachian interval, with a diversity peak reached in the late Sinemurian. This is consistent with the global recovery process after the end-Triassic extinction. The Early Toarcian disappearance of the brachiopods from the TR was apparently connected to the Tethyan anoxic event. The decreasing diversity and/or absence of brachiopods in the Middle to Late Jurassic is explained by the limited food-supply at the deepening sea-floor, i. e. to the gradual subsidence of the territory of the TR. The minor Bajocian and Tithonian diversity peaks were related to phases of extensional tectonic movements providing hard substratum favourable for settlement of brachiopods. Possible cold seeps might contribute to the enrichment of brachiopods by supporting chemosynthetically based communities. Keywords — Brachiopoda, Jurassic, Hungary, stradgraphical distribution, diversity. VÖRÖS, A. & DULAI, A.: Jurassic brachiopods of the Transdanubian Range (Hungary); stratigraphical distribution and diversity changes. — Fragmenta Palaeontologica Hungarica, 24—25: 51-68. Introduction Jurassic sequence except the Callovian and Oxfordian, which are mainly represented by radiolarite. Brachiopods were almost always collected together with ammonites and this offered a possibility to record their stratigraphie distribution. The Hettangian, Sinemurian, Pliensbachian, Bajocian and Tithonian stages yielded a considerable number of specimens while the Toarcian, Aalenian, Bathonian and Kimmeridgian appeared to be almost free of brachiopods. The stratigraphical distribution of Jurassic brachiopods and the faunal changes were previously discussed by us in some detail, but most of these studies were restricted to certain stages, or to the Bakony Mts only (VÖRÖS 1983, 1993, 1997, DULAI 2001, 2002, 2003). Some of these works have been of comprehensive character, but appeared only in Hungarian. In the present paper we extend the overview to the whole Transdanubian Range. This work uses an updated database of the stratigraphical record of the brachiopod species, and considers the results of the new collections, taxonomic studies and nomenclatural emendations. In this paper the brachiopod faunas are shortly introduced and listed by stages and their stratigraphical distribution will be summarized in range charts. Then the diversity changes will be demonstrated in diagrams and the most frequent and characteristic brachiopod taxa are illustrated in photographic plates (Plates I, II, III). Figure 1 — The studied Jurassic brachiopod localities in the Transdanubian Range. — 1: Sümeg; 2: Úrkút, Csárda-hegy; 3: Szentgál, Tűzköves-hegy; 4: Márkó, Som-hegy; 5: Hárskút, Középső-Hajag (Kisnyerges-árok, Közöskútí-árok, Gyenes-puszta); 6: Lókút (Fenyves-kút, Papod-alja); 7: l.ókút, Kericser; 8: Lókút, Lókúti-domb; 9: Eplény (Mangán-bánya, Kávás-hegy); 10: Olaszfalu, Eperkés-hegy; 11: Porva, Kék-hegy; 12: Porva, Kőris-hegy; 13: Bakonybél, Som-heg)'; 14: borzavar (Szilas-árok, Páskom); 15: Zirc (Szesztra-hegy, Cuha-völgy); 16: Iszdmér, Hamuháza-puszta; 17: Csókakő, Csóka-hegy; 18: Tata, Kálvária-domb; 19: Dunaszentmiklós, Hosszúvontató; 20: Neszmély, Nagy-Somló; 21: Neszmély, Asszony-heg)-; 22: Neszmély (Nagy-Teke-hegy, Nyerges-heg) 7 ); 23: Tardos (Alsó-Látó-hegy, Szél-heg)'); 24: Süttő, Vörös-híd; 25: Süttő, Kis-Gerecse; 26: Lábatlan (Póc-kő, Tölgy-hát); 27: Dorog, Nagy-kőszikla; 28: Kesztölc, Kétágú-heg)'. The Jurassic brachiopod fauna of the Transdanubian Range (Hungary) is well-known to brachiopod specialists. It was studied by several Hungarian palaeontologists during the last 130 years (e.g. BÖCKH 1874; ORMÓS 1937; VlGH G. 1943; VÖRÖS 1983,1986,1993,1997,2001; DULAI 2002, 2003). Until now, several thousands brachiopod specimens were collected from the different Jurassic stages. The collecting work, mostly performed by the Hungarian Geological Institute in the 1960's and 1970's, targeted the whole
