Expression of the Younger Dryas cold event in the Carpathian Mountains, Ukraine?

Abstract

Past glacial activity in the Ukrainian Carpathian Mountains is characterized by cirques, glacial valleys and moraine ridges at altitudes between 1350 and 1850 m a.s.l. Although the geomorphology of this area was extensively studied, the deposition time of these glacial forms, and specifically the moraines was never determined. We surveyed and mapped the geomorphology of the Pozhezhevs’ka glacial Valley, which is part of the Charnogora Ridge. We used surface exposure dating and developed a data base of this area using remote sensing and Geographic Information System to understand the timing and nature of glacial event in the eastern Carpathian Mountains. Well-developed continuous lateral-frontal moraines cross the valley floor at ∼1400 m a.s.l. Ten sandstone boulders were sampled from one of these to determine the deposition time of the moraine. Samples were prepared at the Glasgow University Cosmogenic Nuclide Laboratory and analyzed at the SUERC AMS Laboratory. Surface exposure ages were calculated using the CRONUS-Earth online 10Be exposure age calculator. Our exposure ages for nine samples (UKR-2 to UKR-10) range from 11.0 ± 0.4 10Be ka to 14.5 ± 0.5 10Be ka. One sample (UKR-1) produced no current and thus no exposure age is available. The mean deposition time for the moraine ranges from 12.4 ± 0.3 to 12.9 ± 0.3 10Be ka, depending on choice of surface erosion and snow cover. These results provide the first direct indication, using surface exposure dating, of a possible glacier response in the Ukrainian Carpathian Mountains to a cold event contemporary with the Younger Dryas (YD). Together with exposure ages from other mountain ranges across Europe, the new data provide direct chronological evidence for a widespread expression of the YD cold event outside the main ice margin limits left by the former Scandinavian Ice Sheet.