Periglacial phenomena in the Pirin Mountains and on Vitosha (Bulgaria)

Abstract

Article in French.

ORIGINAL TITLE: Phénomènes périglaciaires dans le Pirin et sur la Vitocha (Bulgarie)

The author analyses stone fields, solifluction features and frost-induced sorting features observed in the Pirin Mountains and on Vitosha Mountain. He draws attention to the concise descriptions of such phenomena in the works of H. Louis, where their periglacial genesis was not identified. Stone fields are currently forming as a result of frost weathering at the level of rocky summits. In addition, within the dwarf pine belt of the Pirin Mountains, extensive covers of stabilised Pleistocene stone fields are present, some of which are locally reactivated by contemporary geomorphic processes. Forms of active solifluction have been identified above the dwarf-pine zone, on slopes with inclinations of several degrees. Traces of present-day frost sorting were observed at a lowest elevation of 2190 metres a.s.l, which was on the shore of Lake Ribno. A certain dependence on slope exposure is evident in the distribution of periglacial phenomena. Current solifluction forms occur on thermally favoured slopes, whereas frost weathering forms are found on shaded slopes. Therefore, it can be assumed that the asymmetry of valley forms in the Pirin Mountains, which were shaped during the Pleistocene, is related not only to glacial conditions, as believed by H. Louis, but also to periglacial influences.