Вилафранският етап на България: палеогеоморфоложки и морфотектонски проблеми

Кирил Мишев, Иван Вапцаров. Вилафранският етап на България: палеогеоморфоложки и морфотектонски проблеми

Kiril Mishev, Ivan Vaptsarov. Villafrancian stage in Bulgaria: palaeogeomorphologic and morphotectonic problems

---

VILLAFRANCIAN STAGE IN BULGARIA; PALAEOGEOMORPHOLOGICAL AND MORPHOTECTONIC PROBLEMS

Kiril Mishev, Ivan Vaptsarov

Summary

The geomorphological surveys in Bulgaria are considered to be a solid basis in establishing an intermediate stage between Pliocene and Pleistocene which is well expressed in the recent relief. It is named Villafrancian and is represented by various paragenetic landforms such as river-bedding levels, high river terraces, alluvial-proluvial stepping foothills, mountain summit surfaces, etc. This complex of forms is covered by relatively thick alluvial and alluvial-proluvial sediments consisting of gravel-boulder reddish-brown filling.

Within the single morphostructural units, developed in Bulgaria, the morphogenetic stage in question is specific. Thus, in the Danubian epiplatform it has formed wide flat watersheds (for instance, in the Lom depression) and a valley level at an altitude from 50—60 m up to 100—110 m. The latter can be traced out along the right Danube river slope. It lies under a thick alluvial cover with remnants of Zugolophodon borsoni, Ananancus arvernensis, Archidiscodon meridionalis and others. In the Stara Planina epigeosynclinal system during the Villafrancian stage high river terraces, valley levels or wide footings have come into existence, being now quite often overlain by proluvial deposits. In the Krayshtidi and Sredna Gora morphostructural unit the stage has led to the formation of 120 m, 140— 160 m and 200 m river valley levels within the main river valleys, of stepping footings of glacis type or of thick proluvial trains in the mountain foothills. In the Rila and Rhodopy massif this stage has shaped 2 or 3 high river terraces reaching up to 160—180 m above the river beds and inclined footing surfaces situated in the periphery of the Neogen depressions. By examining the tectonic deformation which the Villaffrancian levels have suffered, it is possible to decode amplitude and intensity of the vertical crustal movements in Bulgaria during the Quaternary. Considerable is their negative tectonic regime especially in the depressions where are located the most active seismic zones in the country.

---

Към съдържанието на статията/ Access to the full text of the article