Late Holocene glacier fluctuations in the Northern Greater Caucasus (Russia) inferred from 10 Be cosmic ray exposure moraine dating

Abstract

Our understanding of mountain glacier changes located in the Greater Caucasus during the Holocene is only loosely constrained. So far moraines were tentatively dated from sporadic cosmic ray exposure (CRE) ages, tree rings and radiocarbon ages. Here, we present 78 ¹⁰Be CRE ages that were obtained from samples collected on moraine boulders and roches moutonnees from one debris-free Terskol glacier and two debris-covered Bashkara and Donguz-Orun glaciers, all located in the Elbrus area. ¹⁰Be CRE ages span from the beginning of the Late Holocene to the Little Ice Age. We did not found evidence of moraine formed neither during the Early Holocene nor during the Mid-Holocene suggesting that during both periods glaciers had a smaller size than during the Late Holocene, when several moraines were deposited at the base of the three glaciers. The oldest moraine that documents the largest Holocene glacier advance occurred around 3.4 ka at the base of the debris-covered Bashkara and Donguz-Orun glaciers, respectively. The debris-free Terskol glacier experienced its largest Holocene extent a bit later in the Late Holocene with moraines dated to ~2.7 ka. Subsequently several glacier advances of smaller extent were recorded almost synchronously between the three glaciers around ~2.2 ka, 1.5 ka, and during the Little Ice Age. Regional climate conditions estimated from TraCE simulations and rare proxy records suggest that the Early and Mid-Holocene were dry and warm with progressive wetter and cooler conditions during the Late Holocene concomitant with glacier evolution observed in the three valleys.