Veress Márton: A Bakony természettudományi kutatásának eredményei 23. - Covered karst evolution... (Zirc, 2000)
THE NORTHERN BAKONY MOUNTAINS: A GEOLOGICAL AND GEOMORPHOLOGICAL DESCRIPTION
THE NORTHERN BAKONY MOUNTAINS: A GEOLOGICAL AND GEOMORPHOLOGICAL DESCRIPTION This overview of the Northern Bakony is based on works of LÁNG (1958), KORPÁS (1981), PÉCSI (1980), FÜLÖP (1989) and JUHÁSZ (1988,1990). Macrotectonic position and physico-geographical divisions The Bakony Mountains of 200 to 710 m altitude is a member of the NE-SW-striking range of the Transdanubian Mountains at its SW end. (The Bakony Mountains and the adjacent marginal hill regions of lower topographic position constitute the Bakony region.) The Transdanubian Mountains is a macrotectonic unit bordered by the Rába (Raab) lineament and the Balaton tectonic zone. It occupied its present position by way of a NE directed rotational intrusion by the Middle Miocene. The mostly Mesozoic carbonate rocks of the mountains were formed in the zone between the Eastern and Southern Alps, on the southern shelf of the opening ocean branch of the Eastern Alps. (Mesozoic formations are regarded as basement and Cenozoic rocks are cover deposits.) Particularly in the area of the Bakony, the Triassic basement of the mountain range gradually acquired a syncline structure, which has become asymmetrical by present. Along the SE flank older Paleozoic formations are exposed, while along the NW flank Triassic and Jurassic and along the axis more recent (Cretaceous and Eocene) rocks occur. Consequently, there is a general NW dip of strata in the SE and a SE one in the NW. (Since the block beyond the present mountain margin have subsided to ever increasing depths, the NW flank is incomplete.) The strikes of Mesozoic rocks of various age are mostly parallel with the overall strike of the mountains. In a geographical sense, the Bakony region is bordered by the Little Hungarian Plain on the NW, by the Great Hungarian Plain on the SE, by the Zala Hills on the SW and by the Vértes Mountains on the NE. The Bakony Mountains is divided into two units by the Tertiary Veszprém-Devecser graben, formed between E-W faults, they are the Northern and Southern Bakony. The Northern Bakony is further subdivided along the Cuha valley into the High and Eastern Bakony. Along the margins (Pápa Bakonyalja, Pannonhalma Hills and Sur Bakonyalja) the blocks of lower elevation are mostly covered by alluvial fans out of which hill regions and glacis surfaces were carved out. The Old or High Bakony is composed of higher mountains and lower basins. The eastern part is subdivided by intramontane basins (Sűrű Mountain Group, Tés Plateau and some horst groups isolated from the latter). The areas studied for karst evolution include parts of the High and Eastern Bakony (Fig. 1) of a total area of 1070 km 2 . Lithology Most of the mountains are built up of Triassic carbonate rocks like „Hauptdolomit" (of 500-600 m thickness) and Dachstein Limestone (300-400 m). The distribution and thickness (ca 250 m) of Jurassic limestones are more limited. Among them the Dachstein-type Liassic Limestone is of the greatest thickness. As a result of the oscillatory basement movements, Cretaceous limestones could not form in great thickness either and their spatial occurrence is relatively restricted. The reef limestones which belong here are the Requienian limestone of 30-80 m thickness and the
