Geological Sketch and the Non-Karstic Caves of the Bakony Mountains in Hungary
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Cadernos Lab. Xeolóxico de Laxe Coruña. 2013. Vol. 37, pp. 11 - 36 ISSN: 0213-4497 Geological sketch and the non-karstic caves of the Bakony Mountains in Hungary ESZTERHÁS, I.1 and SZENTES, G.2 (1) Köztársaság út 157, H-8045 Isztimér, Hungary, [email protected] (2) Alte Frankfurter Str. 22 b, D-61118 Bad Vilbel, Germany, [email protected] Abstract The about 4000 km2 Bakony Mountains form the most extensive region of the Trans-Danubien Mountains between Lake Balaton and Marcal River. They have a typical medium relief, including plateaux of various heights, and denudated fault blocks interspersed with inter mountain basins. In the southern and western areas of the mountains, basalt cones and basaltic sheets are frequently found. In the central area, the variously sloping landscape is inclined towards the blocks. Limestone and dolomite predominate, and there are extensive karst regions and numerous karst caves. Of course, from the point of view of the non-karstic caves, these regions are insignificant. Significantly smaller is the occurrence of quartziferous (sandstone and conglomerate) and basalt rocks, however 147 non-karstic cave are known in these rocks and, in addition, 35 artificial cavities, considered as caves, are listed. The authors describe the geology, the geomorphology and the non-karstic cave development of the Bakony Mountains. Furthermore, typical examples of the caves have been selected and presented according to the different rock formations and development types. Key words: sandstone; geyserites; gas bubble; explosion cave; geyserite cave; tectonic cave; atectonic cave; break down cavity; consequence cave; talus cave; cavity between basalt columns; alkaline solution cave; ice cave; flooded cave.Abstract 12 Eszterhás and Szentes CAD. LAB. XEOL. LAXE 37 (2013) INTRODUCTION As a result of systematic research by the Volcanspeleological Collective, 147 natural The Bakony Mountains form a section non-karst caves and 35 artificial cavities of the 4000 km2 of the Trans-Danubien have been listed in the Bakony Mountains. Mountains between Lake Balaton and Fifty-six non-karstic caves have developed Marcal River. They have a typical medium in basalt. Forty-one caves are listed in the relief, including plateaux of various heights, geyserite of the Tihanyi Peninsula. Thirty- and denudated fault blocks interspersed with two non-karstic caves appear in the Miocene intermontane basins. In the southern and calcareous conglomerate and 10 caves are western areas of the mountains, basalt cones known in the Pannonian quartziferous and basaltic sheets are frequently found. sandstone. Furthermore, 7 caves have In the central area, the variously sloping developed in basaltic tuff and one in loess. landscape is inclined towards the blocks. Artificial cavities have generally been dug in Limestone and dolomite predominate, basalt tuff and loess (Fig. 1). and there are extensive karst regions and The present study intends to summarize numerous karst caves. Of course, from the the development of the non-karstic caves point of view of the non-karstic caves, these and to demonstrate their speleological regions are insignificant. significance. CAD. LAB. XEOL. LAXE 37 (2013) Geological sketch and the non-karstic caves 13 Fig. 1. Location of the non-karstic caves or the clusters of non-karstic caves in the Bakony Mountains SKETCH OF THE GEOMORPHOLOGY Mountains and the Balaton Upland. Other less significant areas of the mountains are The Bakony Mountains make up the Keszthelyi Mountains, the Tapolca the most extensive region of the Trans- Basin and the Bakony Foreland (Fig. 1). The Danubien Mountains (3974 km2) which Northern and Southern Bakony Mountains extends from the Zala River Valley to the are divided by the Veszprém- Devecser Móri Trench and from Lake Balaton to Trench, while the Veszrém – Ngyvázsony the Little Hungarian Plain. The mountains Trench separates the Southern Bakony are divided into three main areas along Mountains and the Balaton Upland. The NE–SW trending fault lines, the Northern Tertiary and Quaternary uplifts formed Bakony Mountains, the Southern Bakony the present elevation of the region. Young 14 Eszterhás and Szentes CAD. LAB. XEOL. LAXE 37 (2013) tectonic movements uplifted the land more buried limestone layers. Fertile basins are and more towards the north. The highest also to be found in the western area. An point of the mountains is Mount Kőris unusual surface formation, an altiplanation 701 m above the sea level, which rises in the surface, is the “Stone Sea” in the Kali Basin, north of the region. The main constituents whilst Castle Hill at Sümeg, a western block of this region are the karstic limestones and of the Southern Bakony, is composed of dolomites. Many characteristic surface and Cretaceous limeston. subsurface karstic forms are to be found in The Keszthelyi Mountains, the the covered and in the opened karst regions westernmost part of the Bakony Mountains, (JUHÁSZ, 1987). are adjacent to the Balaton Uplands. The The Northern Bakony Mountains make mountains consist of limestone and dolomite up the the highest and most extensive area in blocks, which are bordered on either side by the region. The land itself is a forest covered steep multiple faults. Between the blocks karst, which is dotted with many romantic several small basins are to be found. In the valleys. The creeks eroded the covering north-western part of the basalt formation gravel sheet and have cut deep canyons into the Mount Tátika Group occurs. the underlying limestone or dolomite. The The volcanic series of the Balaton largest basin is the loess covered Zirci Basin, Upland is an intra-plate monogenetic which is surrounded with the large blocks of volcanic formation. The volcanic landforms the Northern Bakony Mountains. Surface are composed of denudated maars, tuff water occurrence is insignificant, therefore, rings, spatter cones, lava lakes, valley- settlements are to be found only near the filling lava flows and lava fields. The basalt karst springs. The easternmost parts of has broken through and covered the loose the mountains are the Tési Plateau and the Pannonian sediments of the Tapolca Basin. Bodajki Block. This is a karst region with The overlying hard basalt trap has prevented creeks and dry valleys, with barren rock denudation and thus has developed witness surface and patches of forest with sinkholes buttes. In some witness buttes, for instant and caves. on Mount Szent György, spectacular Southern Bakony is surrounded by the columnar basalt forms occur. Volcanic towns of Veszprém – Devecser - Sümeg and activity has played an important role in Tapolca. The eastern part, the Veszprémi the formation of the Tihanyi Peninsula. Plateau, is a barren dolomite plateau from The Inner Lake and the Outer Lake are the 250 to 300 m above sea level. In the western apparent remains of two calderas (BUCKÓ, part limestone is dominant and contains 1970). Several hundred geyser cones have many diverse karstic features. South of developed as a result of postvolcanic activity the Séd Valley a layer of gravel covers a (CHOLNOKY, 1931). The base formation basalt plateau. The 601 m high Mount Kab of the peninsula is the yellowish white and Mount Agár are the most extensive Pannonian sand and clay, which crops out in stratovolcanoes in the region. The basalt is the steep banks of the Lake Balaton. In the underlain by limestone and pseudokarstic postvolcanic period erosion has significantly depressions which appear on the basalt denuded the volcanic forms themselves surface due to karstic corrosion of the and revealed the fossil surface beneath the CAD. LAB. XEOL. LAXE 37 (2013) Geological sketch and the non-karstic caves 15 Pannonian sediments. Recent valley patterns Hauptdolomite. In the Northern Bakony and alluvial fans have developed over the Mountains, the Dachstein Limestone complete Bakony Mountain range. appears in a narrow belt. The Lower- the Middle- and the GEOLOGICAL SETTINGS Upper Jurassic formations are to be found throughout over in the Bakony Mountains. The Bakony Mountains are basically Limestone and marl series are typical of the composed of sedimentary rocks, which Lower Jurassic among others on the Tési have been superimposed by young basaltic Plateau. Also associated with the Lower formation and geyserite in the Tihanyi Jurassic period it is the black shale-related Peninsula (GYALOG, 2005). manganese ore deposit near the village of The oldest formation is the Ordovician Úrkut. The red ammonitic limestone is a and Silurian series of phyllite and clay schist typical Middle Jurassic formation in the near the village of Alsóörs in the Balaton central region of the mountains. Limestone Upland. series also occur in the Upper Jurassic. Permian red sandstone and conglomerate Cherty limestone was deposited in the overlie the folded Palaeozoic bedrock with Lower Cretaceous period in the Zirci Basin. angular unconformity. Large Permian Limestone was deposited in the Middle outcrops are to be found in the eastern part Cretaceous period. In the Upper Cretaceous of the Bakony Mountains and in the Balaton marl, claey marl and coal seams formed near Upland. The thickness of the formation is the settlements of Ajka and Csehbánya. A some 800 m (JUHÁSZ, 1987). unique formation, which is economically The Triassic sequences have typical important, is the Lower Cretaceous bauxite, classical stratigraphy. The Lower Triassic which occurs extensively in the central strata are composed of clay shale and marl region of the mountains. layers interspersed with thin laminated In the Eocene, terrestrial red clay is limestone and dolomite. This formation overlain by coal measures in the Northern can be observed in the Southern Bakony Bakony Mountains, which are, in turn, Mountains and in the Balaton Upland. In overlain either by Eocene Nummulites the Middle Triassic, thick bedded dolomite Limestone or by algal carbonate platform has been deposited, associated to a lesser sediments. The Nummulites Limestone often extent with limestone. This dolomite forms overlays the bauxite deposits (GYALOG, the Veszprémi Dolomite Plateau.