The sedimentary series from Academician Ridge, Lake Baikal, eastern Siberia, was examined using cation exchange capacity (CEC) to estimate the amount of expandable clay minerals (ECM) and high-temperature X-ray diffraction (HT-XRD) to determine their basic classification. The comparison of the magnetic susceptibility (MS) at sub-millennial resolution and the δl8O record of a reference Atlantic core (ODP 980) was used to create an age model. The most closely studied part of the series covered the major part of the last glacial cycle (120–20 ky BP). The HT-XRD analysis is based on monitoring the course of ECM dehydration with 5°C steps between 25 and 250°C and enabled us to improve the discrimination between ECM, chlorite and micas. The CEC obtained at millennial resolution showed that the neoformation of ECM in warmer periods of the last interglacial was either insignificant or fully compensated by their dissolution or dilution. The CEC record was correlated with the main climatic stages in the period studied. Both MS and CEC records reflected the environmental changes at about millennial resolution, including climatic instabilities between 117 and 73 ky BP (late MIS5).

A new method is proposed for modelling complex X-ray diffraction patterns effectively. The method is based on the calculation of the interference function of the onedimensional disordered crystals with finite thickness. First, we calculated the diffraction effects from structures of individual mineral phases with different layer defects modelled according to the Reynolds’ algorithm. To fit the theoretical to the observed XRD patterns more accurately, we then used a specially developed optimization procedure. This iterative procedure selects the optimal set of chemical and structural parameters (probability and domain size) and yields consistent solutions.

The composition of the clay component in bottom sediments of Lake Baikal relates strongly to glacial/interglacial climate cyclicity. Besides changes in the relative abundance of illite and illite/ smectites between glacial and interglacial periods, significant differences are observed in the crystal chemistries and structures of layered minerals. A change from chlorite during glacial periods to chlorite-smectite during interglacials is probably indicative of the weathering processes in the watershed. Changes in the degree of ordering, in domain size and grain-size distribution of illitesmectites imply differences in genesis of this mineral phase in different palaeoenvironments. These findings further strengthen the case for using clay minerals in the sedimentary record of Lake Baikal as palaeoclimate indicators.

One of our findings was that none of the fractions separated by Stokes’ settling is representative of the bulk sample for either the glacial or interglacial intervals. For the interglacial sample, illitesmectite was concentrated in the <2 μm fraction whereas, for the glacial sample, most of illitesmectite is contained in the <1 μm fraction. The selective use of one fraction is yet another potential source of uncontrolled errors that has to be avoided. We suggest using X-ray patterns of bulk samples as a preferred method of analysis of Lake Baikal (and other) sediments.

The amphipod Gmelinoides fasciatus from Lake Baikal is an example of a species being introduced into a number of water bodies in Russia, including the water system of North-west Russia, to expand food reserves of commercial fish. The interest in this crustacean has been attributed to its successful adaptation and expanding habitat area in the region. In order to assess the role of genetic mechanisms in adaptation to new conditions the frequency of chromosomal aberrations (ChA) at anaphase and telophase stages of mitosis in G. fasciatus embryos from six local populations of Lake Baikal and two invasive populations of the Gulf of Finland, originating from natural habitats were studied in two sequential years. The average level of ChA varied slightly between 0.95% in the samples collected in Lake Baikal and 2.9% in those from the Gulf of Finland. A significant increase in the frequency of ChA was found at two sites in Lake Baikal in 2015 and at two locations in the Gulf of Finland in 2016. First information on G. fasciatus chromosome number and constitution acquired by means of molecular cytogenetic techniques is presented and discussed. The results enable us to suggest this amphipod as a sensitive model to study possible mechanisms of biological adaptation and at the same time as a natural bioindicator of the environmental state.

Paleoproductivity records from Lake Baikal indicate that the last interglaciation in southeastern Siberia lasted ca. 12,000 yr from 127,000 to 115,000 yr B.P., was punctuated by a climatic oscillation about 120,000 yr ago, and ended abruptly with a rapid onset of regional glaciation during marine isotope substage (MIS) 5d. The Siberian equivalent of the MIS 5e–5d transition appears to lead the post-Eemian cold pulses in Europe and in the central North Atlantic by 5000 to 8000 yr. The Baikal record also registers a pronounced cold event during early MIS 5c, which correlates with the Montaigu event in pollen records from France. In Siberia, the climatic deterioration during the MIS 5d was a full-scale glacial pulse unlike the short, moderate cooling during the Montaigu event.

The paleoclimatic record from bottom sediments of Lake Baikal (eastern Siberia) reveals new evidence for an abrupt and intense glaciation during the initial part of the last interglacial period (isotope substage 5d). This glaciation lasted about 12,000 yr from 117,000 to 105,000 yr B.P. according to correlation with the SPECMAP isotope chronology. Lithological and biogeochemical evidence of glaciation from Lake Baikal agrees with evidence for the advance of ice sheet in northwestern Siberia during this time period and also with cryogenic features within the strata of Kazantzevo soils in Southern Siberia. The severe 5d glaciation in Siberia was caused by dramatic cooling due to the decrease in solar insolation (as predicted by the model of insolation changes for northern Asia according to Milankovich theory) coupled with western atmospheric transport of moisture from the open areas of Northern Atlantic and Arctic seas (which became ice-free due to the intense warming during preceeding isotope substage 5e). Other marine and continental records show evidence for cooling during 5d, but not for intense glaciation. Late Pleistocene glaciations in the Northern Hemisphere may have begun in northwestern Siberia.

Lake-level changes inferred from seismic surveying and core sampling of the floor of Lake Baikal near the Selenga River delta can be used to constrain regional climatic history and appear to be correlated to global climate changes represented by marine oxygen isotope stages (MIS). The reflection pattern and correlation to the isotope stages indicate that the topset and progradational foreset sediments of the deltas formed during periods of stable lake levels and warm climatic conditions. During warm stages, the lake level was high, and during cold stages it was low. The drop in the lake level due to cooling from MIS 5 through MIS 4 is estimated to be 33–38 m; from MIS 3 through MIS 2, it fell an additional 11–15 m. Because the lake level is chiefly controlled by evaporation and river input, we infer that more water was supplied to Lake Baikal during warm stages.

This work presents a detailed, orbitally tuned biogenic silica record of continental paleoclimate change during the Brunhes chron. The Brunhes/Matuyama boundary lies within the warm isotopic stage 19 in Baikal, and the boundaries between eight lithological cycles correspond to terminations in the marine oxygen isotope record. The high amplitude and resolution of climatically driven changes in BioSi content in Lake Baikal sediments permits tuning of almost every precessional cycle during the Brunhes and reveals the structure of interglacial stages. For example, the last three interglacial stages (MIS 5, 7, and 9) clearly consist of five substages (a, b, c, d, e) corresponding to precessional insolation peaks. Abrupt and intense regional glaciations in Siberia during substages 5d and 7d were driven by extreme insolation minima. During substage 9d cooling was more gradual in response to more moderate forcing. The impact of strong glaciation is also observed in the middle of stage 15, where full glacial conditions appear to have lasted for over 30,000 yr during substages 15d, 15c, and 15b. Marine oxygen isotopic stage 11 appears to be the warmest period during the Brunhes in the Lake Baikal record, with at least three substages.

A new hypothesis is presented regarding the response of the Lake Baikal BioSi record to insolation forcing. Based on the mechanism controlling modern diatom blooms, biogenic silica production is hypothesized to be dependent on changes in the heat balance of the lake and consequently on changes in the thermal structure of the water column. This mechanism is also sensitive to short-term sub-Milankovich cooling events, such as the mid-Eemian cooling, the Montaigu event during substage 5c, and a cooling which appears to be analogous to the Montaigu event during substage 9c. The continuity of the Lake Baikal paleoclimate record, its sensitivity to orbital forcing, and its high resolution make it an excellent candidate for a new “paleoclimatic stratotype” section for continental Asia.

Here we discuss paleoenvironmental evolution in the Baikal region during the Holocene using new records of aquatic (diatom) and terrestrial vegetation changes from Hovsgol, Mongolia's largest and deepest lake. We reconcile previous contradictory Baikal timescales by constraining reservoir corrections of AMS dates on bulk sedimentary organic carbon. Synthesis of the Holocene records in the Baikal watershed reveals a northward progression in landscape/vegetation changes and an anti-phase behavior of diatom and biogenic silica proxies in neighboring rift lakes. In Lake Baikal, these proxies appear to be responsive to annual temperature increases after 6 ka, whereas in Lake Hovsgol they respond to higher precipitation/runoff from 11 to 7 ka. Unlike around Lake Baikal, warmer summers between 6 and 3.5 ka resulted in the decline, not expansion, of forest vegetation around Lake Hovsgol, apparently as a result of higher soil temperatures and lower moisture availability. The regional climatic proxy data are consistent with a series of 500-yr time slice Holocene GCM simulations for continental Eurasia. Our results allow reevaluation of the concepts of ‘the Holocene optimum’ and a ‘maximum of the Asian summer monsoon’, as applied to paleoclimate records from continental Asia.