Veress Márton: A Bakony természettudományi kutatásának eredményei 23. - Covered karst evolution... (Zirc, 2000)

THE NORTHERN BAKONY MOUNTAINS: A GEOLOGICAL AND GEOMORPHOLOGICAL DESCRIPTION

This points to a periodical uplift of the area. The meander loops formed during meander shifts are often of considerable size. They may have been formed both in unconsolidated cover sediments and in the underlying carbonate rocks. In loose deposits erosional inselbergs may also occur. It is frequently observed that a water-course is inherited over the present-day surface through backward incision (regressional superimposed valley). In the karst gorges of the mountains superimposition is mostly of antecedent nature (superimposed antecedent valley). Such valleys develop on elevated blocks encircling basins if they are mantled by cover sediments. Although terraced valleys are more typical along the mountain margin, some of the valleys in the mountains also show terraces, which are either gravel terraces (in the Gaja valley) or rock terraces (the section of the Gerence Valley between Bakonybél and Huszárokelőpuszta). Along the margins (and sporadically in basins) active alluvial fans are common. Around more elevated blocks abandoned alluvial fans occur, in the sides of valleys dissecting horsts debris fans and rockflows, while on valley floors accumulations of collapsed material can be detected. Subdivisions The High Bakony is constituted of several basins (cryptopeneplains) encircled by horsts of various type (Fig. 1). The basins are aligned in two NE to SW rows. The northern row of basins includes the Porva, Bakonybél and Bakonyjákó Basins and the more southerly one the Dudar, Zirc, Lókút, Pénzesgyőr, Hárskút and Csehbánya Basins. (The first, SE member of the southern row, the Dudar Basin belongs to the Eastern Bakony.) The two rows are bordered to the NE by the Csesznek-Bakonyoszlop Graben. Among the basins the Zirc, Porva and Hárskút Basins lie at relatively higher altitudes and the basement is exposed in several places. Consequently, they are transitional terrains to semiexhumed horsts. To the N and E, the Porva Basin is closed by a series of semiexhumed and exhumed horsts in summit position (Késelő, Kopasz and Csesznek-erdő Hills), although some valleys dissecting the blocks have retreated from the Cuha stream to the basin area. The blocks which border the basin to the N between the Hódos-ér and Bognár-árok streams (Kakas, Dörgő, Szent László-erdő and Télizöld Hills) are horsts or groups of horsts in summit position, buried or semiexhumed. The group of blocks along the W boundary, to the Gerence stream (Kőris, Kék and Parajos Hills) ia composed of horsts in summit position and an exhumed horst in summit position (Tönkölös Hill). To the N, to the Pápa Bakonyalja, horsts in threshold position (Kopasz, Répás-tető and Hosszú Hills) follow. The horsts W of the Gerence stream are the continuations of the Kőris Hill. They are classified as either low threshold surfaces or semiexhumed horsts in relatively low summit position (Somberek and Durrogós-teto Hills). The Bakonybél Basin is bordered to the N by the mentioned Kőris Hill. The W (Hideg, Tevelvár, Pápavár and Hajszabarna Hills) and the S boundaries (Mester-Hajag, ie. the northern member of the Hajag group of blocks) are exhumed horsts uplifted to summit position. The Bakonyjákó Basin is enclosed to the W, S and E by buried horsts in relatively low summit position (Kőpad, Som-hát and Hallgató Hills). To the N the basin is separated from the Pápa Bakonyalja by some smaller and lower blocks. (The E boundary is the mentioned Pápavár and Hajszabarna).