Budai Tamás, Csillag Gábor: A Bakony természettudományi kutatásának eredményei 22. - A Balaton-felvidék középső részének földtana (Zirc, 1998)

GEOLOGY OF THE CENTRAL PART OF THE BALATON HIGHLAND (TRANSDANUBIAN RANGE, HUNGARY)

sure before the establishment of the Main Dolomite platform. In the Balaton Highland only the lower 200 metres of the formation has been preserved. Syncline structure of the Transdanubian Range was formed in the Middle Cretaceous. The Balaton Highland is located in its south-eastern limb. It is characterised by longitudinal compression structures, i.e. synclines, anticlines, overthrusts. Multi-stage uplift in the orogenic phases led to erosion of younger Mesozoic and Paleogene rocks in the Balaton Highland. After the Middle Miocene transgression shallow marine carbonates were deposited (Rákos Fm.). This type of sedimentation continued also in the Late Miocene under brackish-water conditions (Tinnye Fm.). During the latest Miocene the environment became limnic and deposition of siliciclastics became predominant. In the inner part of the Pannonian basin silt and clay (Tihany Fm.), whereas in the coastal belt sand and gravel were deposited (Diás Fm., Kálla Fm.). In an inner lagoon which was separated from the open lake, freshwater lime-mud and clay were formed (Nagyvázsony Fm. ). At the end of the Miocene and in the Early Pliocene basalt volcanism took place in the study area. The volcanic activity produced lava flows, dykes and pyroclastics (Tapolca Fm.). Petrologic feature of the basalts is continental alkaline type. The lehrzolite xenoliths and the mineralogical composition of the olivine bombs prove mantle origin of the magma. Present-day surface of the Balaton Highland was formed during Quaternary. Valley pattern on the peneplane of Nagyvázsony plateau is hardly developed, whereas, on the southern hillside of the range deep incised valleys were formed and several generations of alluvial fans deposited.