Characeae-dominated vegetation succession as a key to understanding the late glacial environmental changes (ca. 14,600–13,500 cal yrs BP): a multi-proxy record of palaeo-waterbody developed within the Klaklowo landslide, the Outer Western Carpathians

Abstract Aquatic ecosystems developed within landslide depressions are common in the region of the Outer Western Carpathi, and they frequently record detailed pond-to-fen vegetation successions initiated by the warming climate of the Bølling-Allerød period. In the Klaklowo landslide fen (the Beskid Makowski Mountains, S Poland) the late glacial deposits are represented by a long (approximately 2.5 m) minerogenic-organic sequence with a distinct section corresponding to the Older Dryas cooling. Here, we applied a high-resolution multi-proxy study (grain size, geochemical, pollen and macrofossil analyses, radiocarbon dating), and we reconstructed vegetation, hydrological and climate changes recorded in the bottom part of the Klaklowo fen sequence (depth range of 250–367 cm). A special emphasis was put on investigating the conditions affecting development of Characeae-dominated vegetation succession and possible reasons behind the discontinuous pollen record. Multi-proxy results revealed that the late glacial sequence (ca. 14,600–13,500 mod. cal yrs BP) of the Klaklowo fen consisted of five palaeoecological stages of development which correspond to the Greenland ice core and Gerzensee chronologies. During the first stage, presumably dry and cold conditions of steppe-tundra prevailed in the surroundings of a poor-in-vegetation Klaklowo waterbody I, matching the Oldest Dryas and Bølling climatic phases. Deterioration of the pollen record observed within this stage most probably resulted from the post-depositional oxidation due to periodical water-level changes of the waterbody I. During the second stage, palaeo-pond was transformed into a short-lasting fen likely with a more wide-spread steppe-tundra vegetation in the catchment area reflecting the dry and cold climate of the Older Dryas. Further two sub-stages of the Klaklowo waterbody II were characterized by aquatic vegetation and boreal forest succession signalizing the Allerød warming. The co-occurrence of macrophytes dominated by wide-spread Characeae meadows and intense precipitation of calcium carbonate indicate that alkaline conditions prevailed in the Klaklowo waterbody II at that time. Carbonate formation probably resulted from leaching of carbonate-bearing bedrock in the catchment area and calcium-rich groundwater supply to the pond intensified by increased precipitation. The last stage is characterized by the disappearance of Characeae meadows which may be attributed to multiple factors including the transition of the palaeo-pond into a fen and related acidification.