Landscapes and Landforms of Hungary by Dénes Lóczy

Author:Dénes Lóczy
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

17.3 Geological Background

The characteristic elements of the geological build-up (Gyalog 1999; Prakfalvi et al. 2007; Gaál and Horváth 2007) are Tertiary sediments, lying on a little known Proterozoic-Paleozoic crystalline basement. In the Paleogene mostly nearshore neritic sediments accumulated, forming mainly clayey marls, sandstones and aleurolites (schlieren). The main and thickest sediments are partly cross-bedded sandstones , particularly the Pétervására Sandstone Formation (see Chap. 19), and the schlieren , mainly the fine-grained Szécsény Schlier Formation. Due to marine regression at the beginning of the Miocene, a varied terrestrial relief came into being, enhanced by a heavy volcanic activity resulting in the thick ignimbrite-like Gyulakeszi (so-called “lower”) Rhyolitic Tuff Formation (see Chap. 18). Following renewed transgression, brown-coal seams formed around Salgótarján. In the second half of the Miocene andesitic laccoliths intruded into the sequence, the largest one constituting Mt. Karancs, which later weathered out and now bears the highest point (729 m) of the region (Fig. 17.1). By the end of the Miocene continental conditions became dominant, resulting in heavy denudation. In the Pliocene, owing to intensive tectonic movements, the area was dismembered, certain tilted tectonic units began to rise and subside, accompanied by heavy volcanic activity. Basalts (Salgóvár Basalt Formation) erupted along deep-seated faults. Small lava cones and plateaus, explosion craters (tuff rings, maars), and weathered necks are the witnesses of this phase of volcanism. The different products (unweathered basalt, columns, laminas, scoria, xenoliths etc.) can be studied best of all along the short (0.5 km) Boszorkány-kő (“Witch Rock”) Nature Trail.

Fig. 17.1Mt. Karancs (729 m), an andesite laccolith (photo by Zoltán Karancsi)

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