Composition of bottom sediments from the anoxic Mogil'noe Lake, Kil'din Island (Barents Sea)

In summer 2006 integrated geological, geochemical, hydrological, and hydrochemical studies were carried out in the relict anoxic Mogil'noe Lake (down to 16 m depths) located in the Kil'din Island in the Barents Sea. Chemical and grain size compositions of bottom sediments from the lake (permanently anoxic basin) and from the Baltic Sea deeps (periodically anoxic basins) were compared. Vertical location of the hydrogen sulfide layer boundary in the lake (9-11 m depths) was practically the same from 1974 up to now. Concentrations of suspended matter in the lake in June and July 2006 appeared to be close to its summer concentrations in seawater of the open Baltic Sea. Muds from the Mogil'noe Lake compared to those of the Baltic Sea deeps are characterized by fluid and flake consistency and by pronounced admixtures of sandy and silty fractions (probably of eolic origin). Lacustrine mud contains much plant remains; iron sulfides and vivianite were also found. Concentrations of 22 elements determined in lacustrine bottom sediments were of the same levels as those found here 33 years ago. Concentrations also appeared to be close to those in corresponding grain size types of bottom sediments in the Baltic Sea. Low C_org/N values (aver. 5.0) in muds of the Mogil'noe Lake compared to ones for muds of the Baltic Sea deeps (aver. 10) evidence considerable planktogenic component in organic matter composition of the lacustrine muds. No indications were reveled for anthropogenic contaminations of the lacustrine bottom sediments with toxic metals.

Pollen record and age determiation of sediments from the Labaz Lake area

Pollen records from perennially frozen sequences provide vegetation and climate reconstruction for the last 48,000 14C years in the central part of Taymyr Peninsula. Open larch forest with Alnus fruticosa and Betula nana grew during the Kargin (Middle Weichselian) Interstade, ca. 48,000-25,000 14C yr B.P. The climate was generally warmer and wetter than today. Open steppe-like communities with Artemisia, Poaceae, Asteraceae, and herb tundralike communities with dwarf Betula and Salix dominated during the Sartan (Late Weichselian) Stade, ca. 24,000-10,300 14C yr B.P. The statistical information method used for climate reconstruction shows that the coldest climate was ca. 20,000-17,000 14C yr B.P. A warming (Allerød Interstade?) with mean July temperature ca. 1.5°C warmer than today occurred ca. 12,000 14C yr B.P. The following cooling with temperatures about 3°-4°C cooler than present and precipitation about 100 mm lower corresponds well with the Younger Dryas Stade. Tundra-steppe vegetation changed to Betula nana-Alnus fruticosa shrub tundra ca. 10,000 14C yr B.P. Larch appeared in the area ca. 9400 14C yr B.P. and disappeared after 2900 14C yr B.P. Cooling events ca. 10,500, 9600, and 8200 14C yr B.P. characterized the first half of the Holocene. A significant warming occurred ca. 8500 14C yr B.P., but the Holocene temperature maximum was at about 6000-4500 14C yr B.P. The vegetation cover approximated modern conditions ca. 2800 14C yr B.P. Late Holocene warming events occurred at ca. 3500, 2000, and 1000 14C yr B.P. A cooling (Little Ice Age?) took place between 500 and 200 14C yr ago.

(Tables, page 17-18), Chemical composition of ferromanganese concretions of the lakes of Northern Savolax in Eastern Finland

This paper discusses the occurrence of manganese-rich concretions in the lakes of Northern Savolax in Eastern Finland. The samples were collected in the summer of 1905 and left to dry for 2 months at room temperature. The quantity of H2O mentionned in the analysis was obtained by dessication at 155°C. The amount of Mn is calulated as MnO2 although other valences might be present in the samples. The contents in CO2 and organic substances was not determined. J. Aschan determined that as a general rule, in Finland the manganese rich lake deposits are rather associated with soft bottom sediments while the iron rich deposits are more assocaited with hard or sandy bottoms.

Multi-proxy records of Two-Yurts Lake

Within the scope of Russian-German palaeoenvironmental research, Two-Yurts Lake (TYL, Dvuh-Yurtochnoe in Russian) was chosen as the main scientific target area to decipher Holocene climate variability on Kamchatka. The 5x2 km large and 26 m deep lake is of proglacial origin and situated on the eastern flank of Sredinny Ridge at the northwestern end of the Central Kamchatka Valley, outside the direct influence of active volcanism. Here, we present results of a multi-proxy study on sediment cores, spanning about the last 7000 years. The general tenor of the TYL record is an increase in continentality and winter snow cover in conjunction with a decrease in temperature, humidity, and biological productivity after 5000-4500 cal yrs BP, inferred from pollen and diatom data and the isotopic composition of organic carbon. The TYL proxy data also show that the late Holocene was punctuated by two colder spells, roughly between 4500 and 3500 cal yrs BP and between 1000 and 200 cal yrs BP, as local expressions of the Neoglacial and Little Ice Age, respectively. These environmental changes can be regarded as direct and indirect responses to climate change, as also demonstrated by other records in the regional terrestrial and marine realm. Long-term climate deterioration was driven by decreasing insolation, while the short-term climate excursions are best explained by local climatic processes. The latter affect the configuration of atmospheric pressure systems that control the sources as well as the temperature and moisture of air masses reaching Kamchatka.