Аннотация:Landscapes of the Kola Peninsula mountains are regarded as products of extensive Pleistocene glaciations, followed by intensive erosion resulting in a network of deep troughs and valleys. At present, slushflows appear as an essential agent of valley sediment transport alongside fluvial erosion. Despite large and widespread geomorphological manifestations (debris fans and terraces), only the latter is considered when reconstructing the Holocene evolution of initial Late Glacial valley topography. However, a detailed study of a series of mountain basins revealed a significant impact of debris flows and slushflows on their transformation. To reliably distinguish landforms and deposits of different origin, we applied a combination of remote sensing data interpretation, mapping, and field investigation of geomorphic patterns and stratigraphic sequences. Facies analyses and radiocarbon dating of buried organic-rich lenses allowed revealing the age, succession, and magnitude of paleogeographical events and drivers of valley lithodynamics since the Late Glacial-Holocene transition. During the Late Glacial and Early Holocene, debris flows played a leading part in sediment transport, leaving large geomorphic footprints inconsistent with modern runoff conditions. Asynchronous degradation of continental and mountain glaciers caused moraine-dammed lakes those breaches led to the largest of debris flow events. Later, their transportation capacity and frequency distinctly decreased due to depletion of both water and sediment sources. Since the Late Holocene, they broadly succumbed to slushflows with much lower clastic content against the higher erosional potential, causing a pronounced incision of older glacial and debris flow landforms. Integration of 50 14C dates for peats and primitive soils in debris fans and taluses indicates several stages of increased slushflow and slope activity over the second part of Holocene. Even low-magnitude yet high-frequency slushflows almost paralyze the normal fluvial process. Disregarding such intensive landscape transformation agents throughout the Holocene causes difficulties in regional correlations of the postglacial mountain basins’ development.
