Dulai Alfréd: A Bakony természettudományi kutatásának eredményei 26. - A Dunántúli-középhegység hettangi és kora-szinemuri (kora-jura) brachiopoda faunája I. Diverzitás, rétegtani elterjedés, paleoökológia, paleobiogeográfia, faunafejlődés (Zirc, 2002)

Summary

SUMMARY Hettangiari and Early Sinemurian (Early Jurassic) brachiopods of the Transdanubian Central Range (Hungary) I. Diversity, stratigraphie distribution, paleoecology, paleobiogeography, evolution. Earliest Jurassic brachiopods are only sporadically known from the Transdanubian Central Range. The aim of my PhD dissertation is the complex examination of Hettangian and Early Sinemurian brachiopod fauna in this area. Bed-by-bed collections have been made at 12 localities of the Bakony Mts and 5 localities of the Gerecse Mts. Intensive collections were made from the Kardosrét Limestone ("Dachstein-type Liassic Limestone") which yielded 10 species, compared to the previously-known two species. No ammonites were found but on the basis of the stratigraphie situation of the formation, a Hettangian age is generally accepted. Seven brachiopod species were determined from the oncoidal basal layers of the Liassic section in the Kálvária Hill at Tata. The associated ammonites indicate the upper part of the Megastoma Zone and the lower part of the Marmorea Zone. Thus 14 brachiopod species have been recovered from the Hettangian formations of the Transdanubian Central Range (5 rhynchonellids, 2 spiriferinids, 7 terebratulids). From the Early Sinemurian localities, 33 taxa were found at Lókút Hill of Early Sinemurian (Bucklandi Zone). At Som Hill in Márkó, 40 taxa are known from the whole sequence. On the basis of the ammonite fauna, the lower part of the sequence (layers 2-20) belongs to the Bucklandi Zone (or perhaps to the Semicostatum Zone), while the upper part of the sequence (layers 23-31) represents the Obtusum Zone. Thus 32 taxa were found in the Lower Sinemurian and 25 taxa in the Upper Sinemurian at this locality. In the Gerecse Mountains 9 species were found in Tölgyhát quarry, 16 species at Póckő and 22 species at Kisgerecse. No ammonites were found at these localities, but on the basis of the brachiopod correlation between these localities and Vöröshíd Quarry, the collected specimens probably belong to the Bucklandi Zone. In Vöröshíd Quarry, ammonites of the upper, thinbedded sequence indicate the Semicostatum Zone, while the lower, thick-bedded part probably belongs to the Bucklandi Zone. Thus 13 brachiopod taxa were found in the Bucklandi Zone and 19 taxa in the Semicostatum Zone of Vöröshíd Quarry. In summary, 64 brachiopod species occur in the Lower Sinemurian layers of the Transdanubian Central Range (27 rhynchonellids, 16 spiriferinids, 21 terebratulids). The Som Hill sequence yielded 8 brachiopod species (3 rhynchonellids, 4 spiriferinids, 1 terebratulid) which were previously unknown from the Late Sinemurian fauna of the Transdanubian Central Range. With the addition of these species, 74 Late Sinemurian brachiopod species are now known from this area (31 rhynchonellids, 13 spiriferinids and 30 terebratulids). Brachiopods are the most frequent (or sometimes only) fossils in the Lower Liassic formations of the Transdanubian Central Range. Therefore in these cases, brachiopods are valuable for biostratigraphy and correlation. Comparison has been made with a global data base (ALMÉRAS, 1964) in which the stratigraphie distribution of Liassic and Dogger brachiopods were summarized. Another comparison was made with a local data base (VÖRÖS,