New insights into Southern Caucasian glacial–interglacial climate conditions inferred from Quaternary gastropod fauna

Abstract

In the present study, we performed gastropod analyses on loess–palaeosol sequences from northeast Armenia (Southern Caucasia) covering at least three glacial–interglacial cycles. The elaborated ecostratigraphy shows significant patterns of species composition related to the succession of pedocomplexes and loess, respectively. Pedocomplexes included species that can be associated with high‐grass to forest‐steppe biomes, indicating increased humidity for these sections compared to the loess layers. In contrast, loess layers that relate to glacial periods are associated with gastropod species of semidesert environments with shrub‐ and shortgrass‐steppes, indicating semiarid to arid conditions. Furthermore, the loess deposits do not show any evidence for cold‐adapted gastropod species. Therefore, we suggest that average July temperatures in the study area were above 10 °C, even during periods of loess deposition. Consequently, we propose that the limiting factor for tree growth during glacial periods was aridity, rather than temperature. In addition, we observe environmental differences between the various glacial times, with our results indicating a trend towards steadily increasing aridity in Southern Caucasia across the Middle to Late Pleistocene.

Evidence for Middle Palaeolithic occupation and landscape change in central Armenia at the open-air site of Alapars-1

“…MIS 5 is regarded in eastern Anatolia as a period of warm, humid climates (Litt et al, 2014, Pickarski et al, 2015a), but despite the resource-rich landscapes that likely resulted, Alapars-1 is only the second site in the region dating to this time interval. Other documented exposures in Armenia with well-developed compound palaeosols and associated biomarker evidence also indicate a relatively warm and stable climate during MIS 5 (e.g., Wolf et al, 2016; Trigui et al, 2019; Richter, 2020). In contrast, during MIS 4–3, when climatic conditions are likely to have been be more arid and less stable in the region (Pickarski et al, 2015b; Stockhecke et al, 2016; Wolf et al, 2016; Trigui et al, 2019; Richter, 2020), hominin occupations at Alapars-1 were more intensive than those documented during MIS 5.…”

“…Other documented exposures in Armenia with well-developed compound palaeosols and associated biomarker evidence also indicate a relatively warm and stable climate during MIS 5 (e.g., Wolf et al, 2016; Trigui et al, 2019; Richter, 2020). In contrast, during MIS 4–3, when climatic conditions are likely to have been be more arid and less stable in the region (Pickarski et al, 2015b; Stockhecke et al, 2016; Wolf et al, 2016; Trigui et al, 2019; Richter, 2020), hominin occupations at Alapars-1 were more intensive than those documented during MIS 5. Lithic artefact assemblages of the latter document nearly all stages of core reduction, showing an emphasis on blank production, use, and maintenance.…”

“…The occurrence of several Bt–Bk horizons at Alapars-1 may indicate that conditions were warm and humid during MIS 5. Elsewhere in Armenia, there is evidence for the development of similar soil profiles associated with interglacial warmth (see Wolf et al, 2016; Trigui et al, 2019; Richter et al, 2020). Although fragmentary in nature, the evidence from these sequences correlates well with palynological evidence from the long lacustrine sequences at Lake Van, Turkey (Litt et al, 2014) and Lake Urmia, Iran (Djamali et al, 2008; Stevens et al, 2012), where warm and humid interglacial periods dominated by the expansion of open deciduous oak steppe-forest are postulated.…”

Short-term occupations at high elevation during the Middle Paleolithic at Kalavan 2 (Republic of Armenia)

“…During glacial periods, winters were thought to have lasted longer, while summer droughts were more frequent, whereas during interglacials precipitation occurred mainly in spring to early summer [35][36][37]. These hydrological changes impacted distributions of terrestrial biota, such as shifts in the treeline elevation [23,24]. The seasonal distribution of resources currently shapes animal migrations [38][39][40][41][42] and most likely will also then have governed the migrations of animals and the hominins that followed them [43,44].…”

“…However, the majority of the Middle and Upper Paleolithic sites (MP and UP) are dated to~65-30 ka (late Marine Isotope Stages (MIS) 4 up to 2) [4][5][6][7][8][9][10][11][12][13][14][15][16]. The environmental conditions during this time interval indicated by regional long-term climatic records were characterized by abrupt, millennial-scale temperature and precipitation oscillations between cold (stadial) and warm (interstadial) stages [17][18][19][20][21][22][23][24][25]. Two parts of the research area have been widely studied: the Imereti region in Georgia where mainly cave sites were studied, including Ortvale Klde are located at 530 m asl [5,13,26].…”