Dating landslides in the Gorce Mts. (Polish Outer Carpathians) – preliminary results

Abstract

Preliminary results of dating landslides in the Gorce Mts. (Polish Outer Carpathians) are given, where ages of landslide activity have been poorly constrained. Four landslide zones with minerogenic mires (fens) were selected in order to determine the age of landslide movements, with depositional sequences of six fens being investigated by boreholes. Conventional radiocarbon dating of wood samples from mineral sediments sealing the landslide depressions was carried out to establish the age of landslide formation or rejuvenation. Loss on ignition analyses were obtained at 2.5 cm intervals along the cores to indicate possible delivery of allochthonous material into the peat bogs. Landslide formation in the Gorce Mts. corresponds to phases of mass movement hitherto identified in the Polish Outer Carpathians. Increased mass movements activity in the Gorce Mts. relate to cold and humid periods of the Holocene which occurred: ~11.1 ka cal BP, 8.6–8.0 cal BP; 6.5–5.9 ka cal BP, 4.8–4.5 cal BP, 3.3–2.5 cal BP and 1.75–1.35 cal BP. Loss on ignition analyses revealed changes in sedimentation in the landslide mires such as formation of mineral and illuvial horizons in peat sequences, and mineral covers overlying fens, associated with humid climatic phases of the Holocene.