Description: A pollen record, obtained from sediments of Lake Sokoch in mountain interior of the Kamchatka Peninsula, covers the last ca. 9600. years (all ages are given in calibrated years BP). Variations in local components, including pollen, spores and non-pollen palynomorphs, and related changes in sedimentation document the lake development from initially seepage and shallow basin to deeper lake during the mid Holocene and then to the hydrologically open system during the late Holocene. The studies of volcanic ashes from the lake sediment core show their complex depositional histories.Lake Sokoch occupies a former proglacial basin between two terminal moraines of the LGM time. The undated basal part of record before ca. 9600. year BP, however, does not reflect properly cold conditions. At that time, although shrublands and tundra dominated, stone birch and white birch forests have already settled in surroundings; the presence of alder woodland indicates wet and maritime-like climate. The subsequent forest advance suggesting warmer conditions was interrupted by the ca. 8000-7600. year BP spell of cooler climate. The following culmination of warmth is bracketed by the evidence of the first maximal forest extent between ca. 7400 and 5100. year BP. During that time, dramatic retreat of alder forest suggests a turn from maritime-like to more continental climate conditions. The cool and wet pulse after ca. 5100. year BP was pronounced as forests retreat while shrublands, meadows and bogs extended. An expansion of white birch forest since ca. 3500. year BP reflected the onset of drier climate, strengthening continentality and seasonal contrast. The second maximum of forests dominated by both stone and white birches occurred between ca. 2200 and 1700. year BP and indicated warming in association with relatively dry and increasingly continental climate. The following period was wetter and cooler, and minor outbreak of alder forest around ca. 1500. year BP suggests a short-term return of maritime-like conditions. Since ca. 1300. year BP forests retreated and replaced by shrublands, tundra and bogs, pointing to cool and wet climate and likely increased back continentality. A prominent re-advance of stone birch forest shown atop the record, most probably reflects recent warming trend.The reconstructed cool periods correlate well with Holocene glacial advances in neighboring mountain areas and with the tree ring and ice core records from the Central Kamchatka Depression. The Lake Sokoch pollen record, being consistent with the previously obtained regional paleoclimatic data, yet contributes new detailed information, especially for the late Holocene.

Description: Distal volcanic tephras in soil sections and lake sediments in the Dvuh-yurtochnoe (Two-Yurts) lake area, central Kamchatka, were investigated in order to provide a chronological framework for the reconstruction of late Quaternary landscape development. Mineralogical and geochemical data point to sources from 5 volcanoes. Ten tephra layers were identified and correlated to known eruptive events. The ages were corroborated by radiocarbon dating of the soil sections around Two-Yurts lake. These findings allow the reconstruction of regional paleoenvironmental change, recorded in the soil sections around Two-Yurts lake. During the Last Glacial Maximum (LGM) time, the area was affected by glacial advances that produced the glacial moraines at the eastern outlet of the lake. A large landslide, ca. 15,000 to 18,000 14C BP, dammed the valley and led to formation of Two-Yurts lake. Several more landslide events can be recognized in the Holocene, and one affected Two-Yurts lake ca. 3000 14C BP. This event produced a “tsunami”, documented by poorly sorted deposits with rounded pebbles in the onshore sections around the lake. In contrast to the soil sections, tephras buried in the “soupy” lacustrine sediments of Two-Yurts lake are not well preserved and show inconsistent age-depth relationships compared to those suggested by radiocarbon dating, due to sinking through the lake sediments. Nevertheless, tephrochronological data revealed the strong impact of terrestrial landslides on lake sedimentation.

Description: This study presents a reconstruction of the Late Holocene climate in Kamchatka based on chironomid remains from a 332 cm long composite sediment core recovered from Dvuyurtochnoe Lake (Two-Yurts Lake, TYL) in central Kamchatka. The oldest recovered sediments date to about 4500 cal years BP. Chironomid head capsules from TYL reflect a rich and diverse fauna. An unknown morphotype of Tanytarsini, Tanytarsus type klein, was found in the lake sediments. Our analysis reveals four chironomid assemblage zones reflecting four different climatic periods in the Late Holocene. Between 4500 and 4000 cal years BP, the chironomid composition indicates a high lake level, well-oxygenated lake water conditions and close to modern temperatures (w13 �C). From 4000 to 1000 cal years BP, two consecutive warm intervals were recorded, with the highest reconstructed temperature reaching 16.8 �C between 3700 and 2800 cal years BP. Cooling trend, started around 1100 cal years BP led to low temperatures during the last stage of the Holocene. Comparison with other regional studies has shown that termination of cooling at the beginning of late Holocene is relatively synchronous in central Kamchatka, South Kurile, Bering and Japanese Islands and take place around 3700 cal years BP. From ca 3700 cal years BP to the last millennium, a newly strengthened climate continentality accompanied by general warming trend with minor cool excursions led to apparent spatial heterogeneity of climatic patterns in the region. Some timing differences in climatic changes reconstructed from chironomid record of TYL sediments and late Holocene events reconstructed from other sites and other proxies might be linked to differences in local forcing mechanisms or caused by the different degree of dating precision, the different temporal resolution, and the different sensitive responses of climate proxies to the climate variations. Further high-resolution stratigraphic studies in this region are needed to understand the spatially complex pattern of climate change in Holocene in Kamchatka and the surrounding region. �

Description: Palaeoenvironmental reconstructions with temporal coverages extending beyond Marine Isotope Stage (MIS) three are scarce within the data sparse region of Chukotka, Far East Russia. The objective of this paper is to infer palaeoenvironmental variability from a 10.76 m long, OSL- and 14C- dated sediment core from Lake Ilirney, Chukotka (67°21′N, 168°19′E). We analysed high-resolution sediment-geochemistry (XRF), sedimentology (TC, TN, TOC, grain-size), mineralogy (XRD) and preliminary micropalaeontological data (diatoms and pollen) from the core as well as acoustic sub-bottom profiling data from the lake basin. Our results affirm the application of XRF-based sediment-geochemical proxies as effective tracers of palaeoenvironmental variability within arctic lake systems. Our study reveals that a lake formed during MIS3 from 51.8 (±4.1) ka BP, following extensive MIS4 glaciation. Catchment palaeoenvironmental conditions during this time remained harsh associated with the continued presence of a catchment glacier until 36.2 (±2.6) ka BP. Partial amelioration reflected by increased diatom, catchment vegetation and lake organic productivity and clastic sediment input from mixed sources from 36.2 (±2.6) ka BP resulted in a lake high-stand ∼15 m above present and is interpreted as evidence of a more productive palaeoenvironment coincident with the MIS3 interstadial optimum. A transitional period of deteriorating palaeoenvironmental conditions occurred ∼30–27.9 ka BP and was superseded by periglacial-glacial conditions from 27.9 (±0.8) ka BP, during the last glacial maximum. Deglaciation as marked by sediment-geochemical proxies commenced at 20.2 (±0.8) ka BP. Our findings are compared with lacustrine, Yedoma and river-bluff records from across Beringia and potentially yield limited support for a marked Younger Dryas cooling in the study area.

Description: The Drake Passage, as the narrowest passage around Antarctica, exerts significant influences on the physical, chemical, and biological interactions between the Pacific and Atlantic Ocean. Here, we identify terrigenous sediment sources and transport pathways in the Drake Passage region over the past 140 ka BP (thousand years before present), based on grain size, clay mineral assemblages, geochemistry and mass-specific magnetic susceptibility records. Terrigenous sediment supply in the Drake Passage is mainly derived from the southeast Pacific, southern South America and the Antarctic Peninsula. Our results provide robust evidence that the Antarctic Circumpolar Current (ACC) has served as the key driver for sediment dispersal in the Drake Passage. High glacial mass accumulation rates indicate enhanced detrital input, which was closely linked to a large expansion of ice sheets in southern South America and on the Antarctic Peninsula during the glacial maximum, as significantly advanced glaciers eroded more glaciogenic sediments from the continental hinterlands into the Drake Passage. Moreover, lower glacial sea levels exposed large continental shelves, which together with weakened ACC strength likely amplified the efficiency of sediment supply and deposition in the deep ocean. In contrast, significant glaciers' shrinkage during interglacials, together with higher sea-level conditions and storage of sediment in nearby fjords reduced terrigenous sediment inputs. Furthermore, a stronger ACC may have induced winnowing effects and further lowered the mass accumulation rates. Evolution of ice sheets, sea level changes and climate related ACC dynamic have thus exerted critical influences on the terrigenous sediment supply and deposition in the Drake Passage region over the last glacial-interglacial cycle.