FIRST MULTY-PROXY STUDIES OF HIGH-MOUNTAIN LAKES IN ARMENIA: PRELIMINARY RESULTS (original) (raw)
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2013
KuniIliko Endo, TosIliIliko Sugai, TsuyosIli HaragucIli, TakasIli CIliba, Reisuke Kondo, Yuriko Nakao , Yasunori Nakayama , SIligeru Suzuki,' IlitosIli SIlimizu, Akio Sato, Iliroki Montani, Ilideo Yamasaki , Haruka Matsuoka, YuicIli YosIlinaga , KosIliro Miyata, YuicIliro Minami , Jiro Komori, YoicIli Hara ,' Arisa Nakamura, Natsumi Kubo, IlideIliro Sohma, Jean-Marc Deom, Renato Sala, Saida A. Nigmatova, and Bolat Z. Aubekerov
The Holocene, 2020
This paper presents new multi-proxy records of the Holocene environmental and climatic changes in the Western Caucasus revealed from a continuous sediment sequence from mountainous Lake Khuko (Caucasus State Natural Biospheric Reserve, 1744 m a.s.l.). Palaeoecological analyses of a sediment core for grain size, magnetic susceptibility, loss on ignition, and pollen allowed us to determine five principal climatic phases with several subphases since 10.5 ka BP. The age model is based on seven accelerator mass spectrometry 14C dates, supplemented by 210Pb data for the uppermost part of the sediment core. Warm periods (10.5–6.7, 6.7–5.5, 3.5–2.4, 0.8–0.5 ka BP) were characterized by high biological productivity in the lake as indicated by high organic matter content and expansion of forests, typical of modern low and middle mountain zones, as indicated by the increase in abundance of Quercus, Ulmus, Corylus, and Tilia in the pollen assemblages. Cold periods (5.5–3.5, 2.4–0.8, and 0.5 ka ...
Late Pleistocene to Holocene paleoenvironmental evolution of Lake Hazar, Eastern Anatolia, Turkey
Quaternary International, 2018
High-resolution seismic reflection profiles and core analyses in Lake Hazar provide a detailed record of the lake level fluctuations and the robust chronology of paleoclimatic events of the Eastern Anatolia during the late Pleistocene to Holocene. The earlier period of Marine Isotope Stage 3 (MIS-3) prior to 48 cal ka BP was accompanied by considerable lake level drop below À95 m, whereas the lake level increase during the later period (ca. 48-29 cal ka BP) gave rise to deposition of a transgressive unit with typical of aggradational architecture in the seismic reflection profiles. High climate variability with the Greenland interstadials and stadials (Dansgard-Oeschger and Heinrich events) in Lake Hazar are sensitively recorded in the core sediments by using multi-proxy analyses. Adjustment of seismic units correlating with the radiocarbon-dated chronostratigraphic units in the studied cores implies that the early Marine Isotope Stage 2 (MIS-2) is marked by an another lowstand lake level existed at ca. À90 m during 29e23 cal ka BP. In comparision to MIS-3 stage, the multi-proxy analyses reveal a general dry evaporative condition during most of the Last Glacial Maximum. In Lake Hazar, the maximum humidity in the late glacial period existed during 14.9e13.5 cal ka BP. The existence of a hiatus in the sedimentary record is documented in the seismic data that coincides with the cold and dry Younger Dryas period, implying a remarkable lake level drop. The multi-proxy records of the Holocene sediments reveal that a maximum precipitation in the early Holocene period prevailed during 10.1e9.3 cal ka BP, leading water level rise in the lake. In Lake Hazar, the middle Holocene until 4.9 cal ka BP is represented by highly climate variations, indicating a series of shorter wet and longer dry climate periods. The late Holocene is accompanied by lake level rises under a general wet climate condition that was interrupted by short dry climate intervals during 3.7e3.3 cal ka BP, 2.8e2.6 cal ka BP and 2.1e1.8 cal ka BP.
Paravani, a puzzling lake in the South Caucasus
Quaternary International, 2020
Sediments of Lake Paravani, the largest natural lake in the South Caucasus, were analysed to reconstruct the millennial history of the environment. Pollen analysis, previously undertaken on the first core retrieved in the middle of the lake, revealed a vegetation history for the last 12 millennia. As part of the present study, a new core was taken from the northwestern part of the lake. Pollen analysis was performed on this new core with the same methodology as for the previous one. A sedimentological and geochemical analysis was also conducted on both cores in order to gain an understanding of the dynamics of erosion in the catchment area in response to landscape modifications. The results show that the sediment deposits within Lake Paravani yield rather complex and puzzle-like palaeoecological records. Despite the differences between the two records, correlations have been made that are supported by the 14C dates. By combining all of the data from both cores, it was finally possible to reconstruct the puzzle of the environmental history recounted by the Lake Paravani sediments. This reconstructed history is composed of four main phases: 1. a steppic environment marked by pronounced erosion processes from 12 000 to 10 000 cal. BP; 2. a transition phase characterized by the expansion of grasses (Poaceae) from 10 000 to 9-8 000 cal. BP; 3. a more forested phase from 9-8 000 to 2 000 cal. BP, during which the erosion fluxes decreased; and 4. a decline in tree cover probably due to human activities over the last 2 millennia. Manuscript File Click here to view linked References
Mid Holocene vegetation reconstruction from Vanevan peat (eastern shore of Lake Sevan; Armenia)
Leroyer, C., Joannin, S., Aoustin, D., Ali, A.A., Peyron, O., Ollivier V., Tozalakyan, P., Karakhanyan, A., Jude F. Quaternary International 2015 A sediment core has been retrieved from Vanevan peat (south-eastern shore of Lake Sevan, Armenia), which is today disconnected from Lake Sevan thanks to an artificial shallowing of the lake. Based on 5 radiocarbon dates, Vanevan record covers the Mid Holocene (from ca. 7800 to ca. 5100 cal. BP). The Late Holocene is today absent in the peat stratigraphy due to modern peat exploitation by surface mining. This study focuses on a multi-proxy approach including pollen, charcoals, and pollen-inferred climate reconstruction. An open-land, steppic vegetation is recorded up to ca. 7700 cal. BP, followed by a more forested landscape during the Mid Holocene (up to ca. 5700 cal. BP), and ending again with an open-land vegetation (to the end of record, 5100 cal. BP). This vegetation dynamics responds to general climate changes documented in the Near East. Whether human activities are documented since ca. 7500 cal. BP (Late Neolithic) in Vanevan, they remain marginal and probably did not affect the area. Early Holocene dry climate, which caused the steppic environment to be widespread through the Near East, is strongly related to low late spring precipitation (PMay–Jun = 180 mm). Mid Holocene forested landscape and increasing lake-level seem related to late spring precipitation (+28%), which is the main change in estimated climate parameters. This has to be linked with reinforcement of the Westerlies and less active Siberian High, which are inversely involved in the following, dry phase starting at ca. 5700 cal. BP.
Quaternary International, 2014
A lake sediment core collected from the Staroje Lake, southeastern Belarus, reveals significant changes of the terrestrial and limnic environmental during the Lateglacial and Early Holocene in the periglacial zone of the Late Weichselian Glaciation. The combination of lithological (loss-on-ignition), palaeobotanical (pollen, non-pollen palynomorphs, diatoms) and isotopic (d 18 O, d 13 C, 14 C) proxy parameters was applied for the reconstruction of the vegetation pattern and sedimentation regime. The Lateglacial pre-Interstadial (GS-2) vegetation was dominated by mineral-soil pioneers with scattered occurrence of Pinus and Betula; an Interstadial (GI-1) dominated by Pinus forest with increasing representation of openground species since approximately 13,500 cal BP; and Lateglacial Stadial (GS-1) with recurring opening of the vegetation pattern with scattered tree patches including those of Picea. Presence of Pinus stomata confirms the local origin of this plant since the pre-Interstadial. Starting from the Holocene, birch, later accompanied by other deciduous species (Ulmus, Alnus, Quercus, Corylus), took over in the local vegetation structure.
A lake sediment core collected from the Staroje Lake, southeastern Belarus, reveals significant changes of the terrestrial and limnic environmental during the Lateglacial and Early Holocene in the periglacial zone of the Late Weichselian Glaciation. The combination of lithological (loss-on-ignition), palaeobotanical (pollen, non-pollen palynomorphs, diatoms) and isotopic (d 18 O, d 13 C, 14 C) proxy parameters was applied for the reconstruction of the vegetation pattern and sedimentation regime. The Lateglacial pre-Interstadial (GS-2) vegetation was dominated by mineral-soil pioneers with scattered occurrence of Pinus and Betula; an Interstadial (GI-1) dominated by Pinus forest with increasing representation of openground species since approximately 13,500 cal BP; and Lateglacial Stadial (GS-1) with recurring opening of the vegetation pattern with scattered tree patches including those of Picea. Presence of Pinus stomata confirms the local origin of this plant since the pre-Interstadial. Starting from the Holocene, birch, later accompanied by other deciduous species (Ulmus, Alnus, Quercus, Corylus), took over in the local vegetation structure.
Acta Palaeobotanica, 1996
On the basis of palynological studies of lake, lake-swamp and soil sediments located in the alpine and subnival belts of the northern part of the Western Caucasus (Arkhyz, Russia), the character of the evolution of vegetation, climate and lake levels during the last 5-6 millenia has been established. During the period 4300- 4200 BP the landscape of the Arkhyz high mountains underwent radical changes when, as a result of intense cooling, the alpine belts descended several hundred metres. The lakes that had existed on the site under investi gation throughout the Atlantic period began to disappear. Alpine meadows were replaced by the sparse vegeta tion of the subnival belt. The deterioration of the SB climate was rather prolonged and was interrupted by one significant warming. However, the SA coolings were marked by their short duration and greater frequency. The most important were the climatic deteriorations from 1300-1200 BP and 400-350 BP.
Quaternary Geochronology, 2019
A 601 m long sedimentary sequence was drilled in Lake Acig€ ol, located in the lakes region of SW Anatolia, near the Denizli travertine from which the oldest hominin of Turkey was unearthed. Among all dating methods applied to the sedimentary sequence, paleomagnetism, through the recognition of geomagnetic chrons, was the most successful and led to a quasi linear age model, with the 601 m long sedimentary record covering the last 2.3 Ma. An attempt to use the atmospherically deposited 10 Be as a dating method was not very successful but provides interesting clues on this new method. Long-term lake level changes are depicted through lithological variations, in particular the carbonates and evaporites abundance. This change could be influenced by both long term cooling during the last 2 Ma and tectonic activity, which may in particular be responsible for a maximum water depth at around 1.8 Ma. Despite active tectonic influence, the sedimentary facies description and the magnetic susceptibility record (cleaned from tephra intervals) show that climate fluctuations (i.e., glacialinterglacial alternations) are likely recorded in the sedimentary succession, with warm periods marked by enhanced carbonate precipitation and cold and dry periods characterized by more detrital input linked to reduced vegetation cover and consequently more erosion in the catchment area. Preliminary pollen data, used to interpret magnetic susceptibility fluctuations, show that an average dry and open landscape prevailed around Acig€ ol lake during the whole record.