Last glacial loess dynamics in the Southern Caucasus (NE-Armenia) and the phenomenon of missing loess deposition during MIS-2

Abstract

The Marine Isotope Stage (MIS) 2 is considered the coldest, driest and stormiest period during the last Glacial-Interglacial cycle in large parts of Eurasia. This resulted from strongly decreased northern hemisphere temperature and related maximum extension of northern ice sheets that strongly reinforced large-scale circulation modes such as westerlies and East Asian Winter Monsoon driven by the Siberian High. Normally, this intensified circulation is reflected by maximum loess deposition in numerous loess regions spanning Europe and Asia. However, here we present a new loess record from the Caucasus region in NE-Armenia providing evidence in support of heavily reduced or even lacking loess formation during the MIS-2. Owing to implementations of comprehensible luminescence dating work and a provenance survey using rock magnetic and geochemical data, we are able to define distinct loess formation phases and to retrace sediment transport pathways. By comparing our results to other Eurasian palaeo-records, we unveil general atmospheric circulation modes that are most likely responsible for loess formation in the Southern Caucasus. Moreover, we try to test different scenarios to explain lacking loess formation during MIS-2. In line with other archive information, we suggest that loess formation was hampered by higher regional moisture conditions caused by a southward-shift of westerlies and renewed moisture absorption over the Black Sea. Our results show that modifications of MIS-2 circulation modes induced a very heterogeneous moisture distribution, particularly in the lower mid-latitudes of Eurasia producing a juxtaposition of very dry (morphodynamically active) and moderately dry (morphodynamically stable) areas.

Palaeoenvironmental and Chronological Context of Hominin Occupations of the Armenian Highlands During Mis 3: Evidence from Ararat-1 Cave

“…Climatic reconstructions from Ararat-1 further highlight the spatial variability of MIS 3 environments and its role in hominin land use adaptations, demonstrating the importance of the Armenian Highlands for understanding regional MP settlement dynamics during a critical period of hominin dispersals and evolution. Wolf et al, 2016Wolf et al, , 2022Trigui et al, 2019;Richter et al, 2020…”

“…Conversely, the micro-faunal assemblage from Kalavan-2 indicates more humid and vegetated conditions during early MIS 3 (60-45 ka; Malinsky-Buller et al, 2021), whilst faunal remains from the Upper Palaeolithic site of Aghitu-3 suggest relatively warm and humid climate conditions similar to present-day from 39-32 ka, followed by cooling between 32 and 29 ka (Kandel et al, 2017). Although there is limited palaeoenvironmental evidence for MIS 3 elsewhere in the Armenian Highlands, malacological evidence from the loess-palaeosol sequences (LPS) in the Sevkar region shows a predominance of semi-desert and xerophilic steppe taxa, indicating persistently arid conditions throughout MIS 3 (Wolf et al, 2016(Wolf et al, , 2022Trigui et al, 2019;Richter et al, 2020).…”

“…There are several probable explanations for this. First, this could be related to a reduction in cave sediment supply (i.e., a reduction in available fine-grained material for aeolian transport conditions), due to climate or broader landscape changes (e.g., Wolf et al, 2022). Second, the upper part the Ararat-1 sequence containing the MIS 2 and MIS 1 sediments may have been removed through erosion processes (i.e., a cave flood or deflation event).…”