Folia Historico-Naturalia Musei Matraensis - A Mátra Múzeum Természetrajzi Közleményei 17. (1992)

Füköh, L.: Malacostratigraphical Investigation of the Late Quaternary Subsided Zones of Hungary

MALACOSTRATIGRAPHICAL INVESTIGATION OF THE GREAT PLAIN Danube - Tisza Interfluve The juvenile subsided zones of the Great Plain has been examined at the Oanube-Tisza Interfluve the best. The results of these investigations were published by the research workers of the Geological Department of the József Attila University of Arts and Sciences at Szeed. The papers contain the palaeecologlcal examinations of the Holocene faunae. Hereinafter I summarize the results of the faunistical examinations of the best known subsided zones. The sequences begin mostly with loessy-sandy sdiments (MUCSI, L. 1963, 1965, 1966) which sign cold climate. The following calcareous deposits and their fresh-water species prove the permanent humid relief and the rainy climate. The sequence is completed by peet formation and humic depostls. The characteristic species of the fauna are the Planorbis planorbis the Gyraulus crista, the ValvTta cristata, etc. The best investigated lake of the territory is the Kolon-tó (MOLNÁR, В. IVANYOSI-SZABÓ, Л. - FÉNYES, J. 1979). It was emerged in one of the filled up branches of the river Danube. The bottom of the sequence is consist of fractions of different grain size sand and silt, on which settles lime mud. The siltation is finished with peat sediments here, too. The most interesting and most significant species of the Holocene layers is the Gyraulus riparius. Beside this species the other faunistical, interest Is meant by the Pisldium moitesserianum which rare occurrence is already noteworthy In the fauna of the Fertö-tó (Lake-Fertö) (FÖKÖH, L. 1986). The paper, written by FÉNYES (1983) contains the results of the further examinations. Beside the Kolon-tó he publishes the malacostratigraphlcal and palaeocological examination of the Kerek-tó (Bugac) and the Vörös-mocsár (Danube-valley). In case of Kerek-tó the sequence Is similar to the above mentioned series: sandy loess is on the bottom, the next is the lime mud and the overlying bed is the peat. According the ecological distribution of Fényes the calcareous mud contains the so called "species requiring permanent water-cover" here,too. The sequence of Vörös-mocsár is almost homogeneus peat. There are clay deposits under the peat. Its deposits are highly similar to the formation of those sediments which were explored at the vicinity of Nádasladány (Sárrét, Fejér county), (FÜKÜH, L. 1988), and also similar to the sequence Fertőrákos 2 (Ferte-tó), (FÜKÜH, L. 1986). The author (FÉNYES, J. 1983) with the full knowledge of the three lakes' faunal-succession, attempts to analyse the connection between the sedimentation and the climate. It Is based on the relative frequency of the polythermic end oligothermic species of the fauna. Relying upon these findings he writes the next: the absolute rate of the polythermic species grow remarkably during the formation of the calcareous mud. This conclusion is in well-accordance with the result of those investigations which were performed at Sárszentmihály profile number I. (Sárrét, Fejér County FÖKÖH, L. 1977). The growth of the relative abudance of the polythermic species during the period of peat formation, stops short in its lower level-we could observe 20 per cent decrease in case of Kolon-tó - and then it grows rapidly again. The paper of TÖTH, A\ - MOLNÁR, В. (1987) marks the third period in the malacological Investigation of the Danube-Tisza Interfluve. The paper dissects the fauna of the holocene sediments of Bugac-Bócsa from the point of view of palaeoecology. The teritory belongs to the Kiskunság National Park. The above mentioned dissertation is published in that volume which issued for the Canadian Congress of the INQA. Apart from the detailed analyses I refer to that the deposits of the three finding places are similar to the formers,: calcareous mud settles onto the sandy-loess sediments, end the sequence is finished by peat. In both sequence (Bugac-Bócsa, Feketeszéki-tó, Gáspárszéki-tó,) can be found the Gyraulus riparius! 102