The Lowest Elevated Pleistocene Glaciers in the Carpathians – Geomorphological and Sedimentological Record of Glaciation in the Polonyna Rivna and Borzhava Massifs (Ukraine Carpathians)

Abstract

The Polonyna Rivna (1480 m asl) and Borzhava (1682 m asl) ranges represent the medium-high mountain massifs located in the north-western part of the Ukrainian Carpathians, where the legacy of the Pleistocene glaciation has long been unexplored. Based on the first detailed mapping of glacial landforms and sedimentological analysis, we document the presence of freshly-shaped outer moraines and glacial cirques and reconstruct the extent and ice-surface geometry of the six very small (0.09–0.78 km2 area) palaeoglaciers. The specific feature of the area is the presence of extensive mountain-top plateaus that play an important role as additional areas for snowblow accumulation. The equilibrium line altitudes (ELAs) calculated from hypsometry of reconstructed maximal glacier extent using the area x altitude balance ratio (AABR) 1.6 method is exceptionally low at 1138 m in the Polonyna Rivna and 1230 m in the Borzhava range. Excluding the topographic effect produced by additional snow accumulation the ELA shift upwards between 120 – 180 m which corresponds to 25 – 53% of the glacier elevation range. The resulted climatic ELA (1282–1352 m) together with the mean cirque floor altitude (1194 m) and mean elevation of the glacier fronts (994 m asl) represent the lowest values in the entire Carpathian arc. Our data indicate glacier-friendly conditions in the mountain massifs exceeding 1400 m asl in the windward NW part of the Ukrainian Carpathians where due to relatively cold air temperatures and orographic induced precipitation local topolimatic factors dictated the development of marginal glaciation.