Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 83. (Budapest 1991)

Fischer, O. ; Hably, L.: Pliocene flora from the alginite at Gérce

ANNALES HISTORICO-NATURALES MUSEI NATIONALIS HUNGARICI Tomus 83. Budapest, 1991 p. 25-17. Pliocene flora from the alginite at Gérce by O. FISCHER, Berlin & L. HABLY, Budapest FISCHER, O. & HABLY, L.: Pliocene flora from the alginite at Gérce. - Annlshist-nat Mus. natn. hung. 1991, 83: 000-000. Abstract - The new Pliocene locality at Gérce represents a remain of the zonal vegetation, belonging to the deciduous broad-leaved forest, characterized by Quercus kuhinyii-Zelkova zelkovaefoüa. It differs from the earlier published Pliocene floras (HORVÁTH 1961, 1963), which belonged to the riparian vegetation. Gérce is the first locality for Buxuspliocenica in Hungary, determined by anatomical analysis. With 31 figures and 8 photoplates. INTRODUCTION Three-five million years ago violent volcanic eruption occurred in the Pannon lake system that filled the Carpathian Basin. As well as the basalt mountains they also built special tuff rings. After calming down of volcanism the inner part of these tuff rings were filled with water, thus crater lakes were formed. Alga multiplied incredibly in these well- closed crater lakes whose water was quiet and rich in nutriment. After dying and settling down at the bottom of the lakes they accumulated as alginite. Together with the material of the basaltic tuff which had crumbled into clay sediment measures accumulated consisting of filmy plates. There are four volcanic craters in Hungary in which alginite settled. All of them are in Transdanubia: Gérce, Egyházaskesző, Pula, Várkesző. The alginite colony at Gérce of 2.1 km

2 having a depth of 100 m (it is the deepest colony in Hungary) is found in a tuff ring under 4-15 m overlying bed of Pleistocene sand and gravel (Solti 1987). The fine grained lamellar alginite consists of rich, well-conserved leaf remains. The material of this study belongs to the Savaria Museum in Szombathely; it is the collection of E. Horváth. He was the first researcher who called the attention to this locality at a lecture, but his sudden death prevented him from intensive study and publication. Apart from the leaf remains, fossils of animal origin, like the imprints of two feathers and an elytron of a beetle turned up. THE CIRCUMSTANCES OF FOSSILIZATION Certain parts of the plants and animals living near the crater lake drifted into the lake and fossilized. The fine-grained sediment made the conservation of the leaf remains possible. The remains of culticle can be observed in several cases, altough they are disintegrated in the majority of the cases so that they are unsuitable for cuticular analysis. Only one specimen of Buxus pliocenica was so well preserved that good preparation could bee made of it. The fine venation was generally well conserved in alginite, although together with the