Kónya Péter (szerk.): A Bakony-Balaton-felvidék vulkáni terület ásványai - TQS Monographs 1. (Miskolc - Budapest, 2015)
Kónya P.: A Bakony-Balaton felvidék vulkáni terület földtana
Kónya P. (szerk.) (2015): A Bakony-Balaton-felvidék vulkáni terület ásványai. TQS Monographs 1. Miskolc-Budapest: Herman Ottó Múzeum és Magyar Földtani és Geofizikai Intézet, pp. 27^t0. A Bakony-Balaton-felvidék vulkáni terület földtana Geology of the Bakony-Balaton Highland Volcanic Field, Hungary KÓNYA PÉTER Magyar Földtani és Geofizikai Intézet, 1143 Budapest, Stefánia út 14. e-mail: konya.peter@mfgi.hu Abstract The Bakony-Balaton Highland Volcanic Field (BBHVF) belongs to the southern part of the Transdanubian Range of the Pelso (North Pannonian) megatectonic unit. The BBHVF forms the southern flank of the syncline of the Transdanubian Range. The oldest (Lower Palaeozoic) formations are slightly metamorphosed clays, sandstones, shales and psammites (Balaton Phyllite Group). In the Upper Ordovician acidic volcanism (Alsóörs Metarhyolite) and in Ordovician to Devonian intermediate volcanism (Révfülöp Metaandesite) interrupted clastic sedimentation. Basalt volcanism was active in the Silurian (Litér Matabasalt). The volcanic and sedimentary rocks were metamorphosed in the Hercynian orogeny (327-311 Ma). The large scale denudation and debris accumulation of the Balatonfelvidék Sandstone Formation in the Transdanubian Range is an expression of this orogeny. On the Tethyan shelf siliciclastics (Arács Marl, Csopak Marl, Zánka Sandstone) and carbonates (Köveskál Dolomite, Hidegkút Dolomite) were deposited during the Early Triassic. The sedimentary rocks of the Lower Anisian shallow marine carbonate ramp (Aszófő Dolomite, Iszkahegy Limestone) are overlain by the different heteropic platform carbonates (Megyehegy Dolomite, Tagyon Limestone) and basin sedimentary rocks (Felsőörs Limestone) of the Middle Anisian. Basin facies limestone and volcanites on the BBHVF represent the major part of Ladinian (Vászoly and Buchenstein Formations) which are replaced by platform carbonates (Budaörs Dolomite) to the NE and N. At the lower part of the Upper Triassic a thick pelitic sequence was deposited (Veszprém Marl), which becomes more carbonaceous upwards (Sándorhegy Formation). During the next highstand platform carbonates (Sédvölgy Dolomite, Ederics Limestone) developed. The uniform platform of Main Dolomite started to develop at the end of the Carnian. In the Middle to Late Norian the platform dissected across the whole area of the Transdanubian Range. Formations, younger than Upper Triassic and older than Miocene are unknown in the area of the Balaton Highland. Before the Alpine orogeny there were probably no significant differences in the evolution history of the Balaton Highland and the South Bakony Mountains. Folding and thrusting took place on the limbs of the Bakony syncline during the Middle Cretaceous. After the uplift, the Mesozoic to Palaeogene strata started to erode. At the beginning of the Jurassic the development of the carbonate platform continued (Kardosrét Limestone), and then the dissection of the platform started (Pisznice Limestone). Separation into blocks resulted in different carbonate formations (shallow sea — Hierlatz Limestone, shallow basin type — Isztimér Limestone and away from blocks — Tűzkövesárok Limestone). The oxide variant of the Úrkút Manganese-ore Formation reflects conditions of a shallow sea. At the end of the Aptian time a short, general regression followed. After denudation the Alsópere Bauxit Formation, accumulated in the Dachstein Limestone (deep karstic pits), is the first sign of renewed sedimentation. During the regression the swamp-lake sediments (Tés Clay Marl), then the shallow marine Zirc Limestone Formation were deposited. In the Upper Cretaceous fluvial and swamp-lake sedimentation started (Csehbánya Formation), followed by the deposition of coal-swamp sediments (Ajka Coal). After uplift in the Late Cretaceous, during the Palaeocene - Early Eocene the Bakony area became dry land, and subjected to strong erosional effects. After erosion, during continental sedimentation bauxite deposits were formed (Gánt Bauxite). Burial of the bauxite began from the Middle Eocene onwards when transgression from the SW reached the area (Darvastó Formation, Szőc Limestone). After the regression of the Eocene sea, during the Early Oligocene denudation had again its turn. The blocks, during the Late Eocene were lifted and so exposed to erosion during the Lower to Middle Oligocene. At the end of the Middle Oligocene the Transdanubian Range was broken up and subsided slowly but unevenly. At the same time terrestrial sedimentation started in the Bakony area (Csatka Pebble). The Neogene basins (Tapolca, Várvölgy and Nagygörbő Basins) in the western part of the Bakony Mountains were formed during extension, and resulted from the horizontal and vertical movements between the blocks of the Keszthely Mountains, Balaton Highland and the Bakony Mountains during the Miocene. Sedimentation is characterised
