Interglacial Deposits Research Articles

Facies characterization based on physical properties from downhole logging for the sediment record of Lake Van, Turkey

Lake Van (Turkey) is the 4th largest terminal lake in the world and is located at a key position for climatic reconstruction. The ICDP project ‘PALEOVAN’ is a deep-drilling campaign initiated in the summer of 2010 to enhance the understanding of paleoclimatic and paleoenvironmental conditions in the Middle East for a period of 550,000 years. Multiple coring of two sites (Northern Basin and Ahlat Ridge) at a water depth of up to 360 m has been performed. The sedimentary record is mainly composed of clayey silts and tephra deposits that were supplied by four volcanic sources: 1) the Süphan volcano, located on the northern shore, 2) the Nemrut volcano, 15 km west of the westernshore, 3) the Incekaya volcano, on the southwestern shore and 4) intralake eruptive centers. The dominant chemical composition of the volcanic sources is known from studies of land deposits.High-quality downhole logs have been acquired from both sites. To construct a continuous lithological profile, 180 m of downhole logging data from the Ahlat Ridge have been analyzed by cluster analysis. To improve the differentiation of the sediments, two elemental intensity profiles from x-ray fluorescence core-scanning (calcium and zirconium) performed on the composite profile core material were added to the cluster analysis. Five cluster units were derived and transformed into three tephra and two clayey silt units.To compare the two clayey silt units with the composite profile from the visual core description (VCD) that showed 15 lithological units, the composite profile was classified into two major groups of lacustrine sediments: banded clayey silts (interpreted as glacial deposits) and laminated clayey silts (interpreted as interglacial deposits). Despite this simplification, no correlation between the two clayey silt units derived from cluster analysis and the banded and laminated clayey silts could be found. The following reasons are proposed: (a) the comparability of the datasets was limited by significant depth shifts of up to 2.5 m between the composite profile based on the VCD and the downhole measurements in hole 2D of the Ahlat Ridge, (b) a correlation was difficult to ascertain from the vertical resolution of the downhole logging data and the extremely detailed core description in mm-scale, (c) mixed signals were obtained because of prevailing thin layers and intercalations of different lithotypes and (d) cluster analysis was difficult to perform because the contrast within the input data is too low (possibly background sedimentation) to distinguish between glacial and interglacial deposits.Tephra units are characterized by contrasting properties and differ mainly in their magnetic susceptibility, spectral gamma ray components (uranium, thorium and potassium) and XRF-intensities of calcium and zirconium. Tephra units have been linked to the dominant volcanic composition of the deposited tephra layers and partly to the volcanic sources. Depth trends are derived with prevailing basaltic deposits in the bottom part (128 m–210 m below lake floor) and are gradually outweighed by the highly differentiated (dacitic and rhyolitic/trachytic) products towards the top of the record.

Vegetation And Stratigraphic Interpretation Of The Mazovian (Holsteinian) Interglacial Profile From Dobropol and other New Sites in the West Polesie Region (SE Poland)

AbstractGeological mapping in eastern Poland resulted in the new find of organic deposits near Włodawa. Pollen and plant macrofossils analyses at the Dobropol site proved deposition during the Mazovian (Holsteinian) Interglacial (MIS 11). Pollen spectra indicated strong predominance of Carpinus in the optimum phase (pollen period III), suggesting intensive influence of continental climate in this part of Po land. The paleolake Dobropol was shallow, with many species of rushes in a littoral zone. During the Liviecian (MIS 10) and the Krznanian (MIS 8) Glaciations the reservoir was occupied by an ice-dam lake, in which silt and clay de position prevailed. The Mazovian Interglacial organic deposits were also recorded in immediate surroundings of the study area. Based on geological and paleobotanical examination of the Dobropol site, the ice sheet of the Krznanian Glaciation seemed to have reached at least the southern part of Włodawa. The ice sheet has not covered pre sum ably the whole study area as its advance occurred in several lobes. The surroundings of Włodawa in the West Polesie Region are the third largest Mazovian paleo-lakeland area in Po land, apart from the vicinities of Biała Podlaska and the Łuków Plain.

How to resolve Pleistocene stratigraphic problems by different methods? A case study from eastern Poland

Different methods have been used to determine the stratigraphic position of Pleistocene alluvial deposits, particularly fluvial interglacial deposits. Near-surface deposits of a meandering river, developed in point-bar and oxbow lake facies, in the Samica River valley (near Łukow, eastern Poland) have been investigated. The fossil valley is incised into the till plain and the outwash. The fluvial succession is locally overlain by solifluction deposits. All the deposits underwent sedimentological analysis. The petrographic composition of basal till occurring in the vicinity of a fossil valley was determined with the method of indicator erratics. Fluvial deposits were examined by pollen analysis and plant macrofossil analysis of oxbow lake facies. Absolute dating methods were applied to the deposits (thermoluminescence methods: TL and additionally IRSL). Lithological differences between fluvial and the surrounding glaciofluvial deposits were identified and their lithostratigraphic position assigned. Petrographic analysis of till and palaeobotanical analyses of oxbow lake facies gave compatible results. Fluvial deposits were formed after the Sanian 2/Elsterian Glaciation, during the Mazovian/Holsteinian Interglacial. Luminescence dating of the fluvial deposits by the TL MAX method yielded the most relevant results (412-445 ka), which indicate that these deposits were formed during the end of the MIS 12 and beginning of the MIS 11 stage.

Reconstructing North Sea palaeolandscapes from 3D and high-density 2D seismic data: An overview

AbstractThe North Sea subsurface shows the marks of long-term tectonic subsidence. Much of it contains a thick record of glacial and interglacial deposits and landscapes, formed during multiple glacial cycles and the associated regressions and transgressions during the past two million years. At times of lower sea level than today, areas that are presently submerged were fertile lowlands more favourable for hunting and gathering than the surrounding upland. These drowned lowlands are not captured by traditional 1:250,000 geological maps of the North Sea subsurface because the underlying seismic and core data are commonly too widely spaced to achieve this. Palaeolandscape mapping requires identification of building blocks with spatial scales in the order of 1 km or less. As high-density 2D and high-quality 3D seismics are becoming available for an increasing part of the North Sea, glacial and interglacial palaeolandscapes can be reconstructed for more and more areas. An overview of published palaeolandscape reconstructions shows that shallow time slices through 3D data provide map views that are very suitable for the identification of landscape elements. For optimal results, each time slice needs to be validated and ground-truthed with 2D seismics and with descriptions and analyses of cores and borehole samples. Interpretations should be made by teams of geoscientists with a sufficiently broad range of expertise to recognise and classify even subtle or unfamiliar patterns and features. The resulting reconstructions will provide a context and an environmental setting for Palaeolithic, Mesolithic, and Neolithic societies and finds.

Inorganic geochemistry data from Lake El'gygytgyn sediments: marine isotope stages 6–11

Abstract. Geochemical analyses were performed on sediments recovered by deep drilling at Lake El'gygytgyn in central Chukotka, northeastern Russia (67°30' N; 172°05' E). Major and rare element concentrations were determined using X-ray fluorescence spectroscopy (XRF) on the < 250 μm fraction from 617 samples dated to ca. 440 and 125 ka, which approximates marine isotope stages (MIS) 11 to 6. The inorganic geochemistry indicates significant variations in elemental composition between glaciations and interglaciations. Interglacial sediments are characterized by high contents of SiO2, Na2O, CaO, K2O, and Sr and are depleted in Al2O3, Fe2O3, TiO2, and MgO. An extreme SiO2 enrichment during MIS 11.3 and 9.3 was caused by an enhanced flux of biogenic silica (BSi). The geochemical structure of MIS 11 shows similar characteristics as seen in MIS 11 records from Lake Baikal (southeastern Siberia) and Antarctic ice cores, thereby arguing for the influence of global forcings on these records. High sediment content of TiO2, Fe2O3, MgO, Al2O3, LOI, Ni, Cr, and Zr typifies glacial stages, with the most marked increases during MIS 7.4 and 6.6. Reducing conditions during glacial times are indicated by peaks in the Fe2O3 content and coinciding low Fe2O3/MnO ratios. This conclusion also is supported by P2O5 and MnO enrichment, indicating an increased abundance of authigenic, fine-grained vivianite. Elemental ratios (CIA, CIW, PIA, and Rb/Sr) indicate that glacial sediments are depleted in mobile elements, like Na, Ca, K and Sr. This depletion was caused by changes in the sedimentation regime and thus reflects environmental changes.

Facies and stratigraphical analyses of glacial and interglacial sediments at Morgan Bluffs, Banks Island, Canadian Arctic Archipelago

Stratigraphical exposures of both glacial and non‐glacial sediments at Morgan Bluffs, a >6‐km long exposure on the east coast of Banks Island, comprise a discontinuous archive of Quaternary environmental change. A detailed facies analysis of the sediments and a new stratigraphical framework is incompatible with the many climatostratigraphical units proposed previously. Instead, three distinct intervals of sedimentation are recognized. The first records the progradation of a delta, followed by fluvial aggradation of a braided river valley perhaps ∼1 Ma. The second documents glacigenic sedimentation, including fluctuations of a tidewater glacier margin, in a marine basin more than 0.78 Ma. The third records till deposition by the NW Laurentide Ice Sheet during the Late Wisconsinan, followed by the progradation of a deglacial, ice‐contact delta into an ice‐dammed lake ∼12.8 cal. ka BP. The revised stratigraphical framework adds important new terrestrial observations to a sparse and fragmentary data set of Quaternary environmental change in the Canadian Arctic. This study challenges former references and correlations to the previously proposed climatostratigraphical framework and nomenclature.

An examination of the fidelity of n-alkanes as a palaeoclimate proxy from sediments of Palaeolake Tianyang, South China

This study examines n-alkane distributions from a 120 m long borehole extracted from Palaeolake Tianyang, South China, which covers the last five glacial cycles. We aim to determine the palaeoclimatic/environmental fidelity of n-alkane distributions in bulk organic matter (OM) from this tropical sedimentary archive. The Tianyang lithostratigraphy reveals a deep-lake sequence (120–42 m) dominated by diatomite, overlain by shallow-lake and marsh sediments in the upper 42 m. The Carbon Preference Index (CPI, C23–C31) suggests that there is weak odd/even predominance (OEP) in long chain n-alkane distributions (C27–C31) in OM from deep lake sediments, and a strong OEP of long chain n-alkane distributions in OM from shallow lake sediments. The opposite characteristics are evident in short chain n-alkane distributions (C16–C20). These CPI values suggest different sources of organic carbon within the deep (dominantly diatom synthesis) and shallow lake (dominantly high plant input), but cannot help differentiate glacial from interglacial sediments. The Terrigenous-to-Aquatic Ratio (TAR) shows high values throughout interglacial sediments (>4) and low values in glacial sediments (<4), corresponding to a higher productivity of high plants during interglacials, and vice versa. The proportion of aquatic plant n-alkanes (Paq) also reveals a clear change between glacial (0.31–0.39) and interglacial periods (0.22–0.28) during shallow lake stage, indicating a reduction in terrestrial OM input during glacial periods relative to interglacial periods. There is a greater amount of Unresolved Complex Mixture (UCM) in glacial sediments than within interglacial sediments. We suggest that the above n-alkanes indexes are useful environmental/climatic indicators within Palaeolake Tianyang, despite the fact that some other indexes, like Average Chain Length (ACL), provide less definitive interpretations.

A geosystems approach to permafrost investigations for engineering applications, an example from a road stabilization experiment, Beaver Creek, Yukon, Canada

The Alaska Highway crosses numerous terrain units underlined by warm and ice-rich discontinuous permafrost highly susceptible to thermal degradation. For years, this infrastructure, which is essential to transportation in northwestern Canada and Alaska, has been showing signs of road damage induced by permafrost degradation. In 2008, Yukon Highways and Public Works, and its international collaborators, implemented a road experimental site near Beaver Creek (Yukon) to test mitigation techniques aiming to control permafrost degradation. Permafrost investigations were done accordingly to a geosystem approach based on the hypothesis that permafrost has a distinctive sensitivity to climate and terrain conditions at a local scale and that changes (dynamics) in the system must be integrated in the analysis to obtain a holistic understanding of permafrost conditions and consequences of potential changes through time. Therefore, permafrost assessment at BC-RES came along with other components assessment such as local climate, natural terrain and embankment conditions.Four main units identified were typically ice-rich, with the exception of one shallow sub-unit (2B) that was ice-poor, but which contained the top of inactive ice-wedges, and Unit 3 at depth. The extent of the syngenetic ice wedges was not encountered, but reached at least a depth of 10.7m. Units 1 and 2 (likely eolian periglacial deposits) were fine-grained soils characterized by a potential to liquefy, if soils thaw and maintain their natural moisture content, and to differential thaw-settlement. Unit 3 (likely interglacial deposit) was mainly made of peat, while Unit 4 (likely glacial deposit) was a diamicton with a fine-grained matrix containing abundant excess ice. Impact from road embankment was measured at many locations in permafrost below the infrastructure. Isothermal profile under the road and embankment subsidence, assessed from core-drilling combination with GPR and ground temperatures, reflected the thermal impact of embankment and its interaction with other geosystem components (e.g. snow, groundwater) on the underlying ice-rich cryostratigraphic units. Thaw depth below embankment sideslopes had mostly reached sub-unit 2B, exposing now excess ground ice from the underlying very ice-rich sub-unit 2C and ice wedge to melting. In this context, an increase in permafrost degradation is expected in the near future, regardless of the mitigation technique performance.Application of the geosystem approach for road infrastructure in permafrost regions was beneficial at the BC-RES to identify the comprehensive critical engineering conditions that should be considered at the infrastructure spatial scale for road sustainability through timescale of its life. This approach emphasized the importance of changes in properties and processes, including their variability and dynamic related to interactions within the system. Overall, engineering studies in permafrost regions, which are typically sensitive to changes in conditions, would clearly benefit from applications of the geosystem approach, which can be adapted to spatial and time scales of these studies.

Paleomagnetic and astronomical dating of sediment core BH08 from the Bohai Sea, China: Implications for glacial–interglacial sedimentation

Sediments from the continental shelf/coastal region bear significant signals of sea-level, climate change as well as local tectonic information. This study presents a high-resolution magnetostratigraphic and rock magnetic study of a 212.4m core (BH08, with a basal age of 1.06Ma) recovered from the shallow (<30m below sea level) Bohai Sea, China. Astronomical tuning based on the sediment redness (a*) of core BH08 allows the construction of a high-resolution chronology that is assisted by magnetostratigraphic data. Sedimentology and associated proxies (grain size and redness) indicate that the cyclic alternation of neritic/littoral sandy deposits and terrestrial silts/clayey silts was mainly controlled by changes in sea-level and associated base-level at glacial–interglacial timescales. The a* record of the core can be correlated with marine δ18O records at 40- and 100-kyr cycles, indicating that the sediments in the study area are continuous at least at orbital timescales regardless of significant base-level variations. This is likely due to continued subsidence in the basin and creation of accommodation space. The significant lower sedimentary accumulation rates since 750ka might be due to the deviation of the depositional locus from core site because of extreme low sea-level stands during the glacials since the Mid-Pleistocene transition (MPT). Especially the glacial sea-level lowstands might have resulted in bypassing or erosion of sediments on the BH08 core site during peak glacials (MIS 6, MIS 10 and MIS 16), limiting the sediment preservation potential. This study documents the longest Quaternary sedimentary succession in the Bohai Sea and provides, for the first time, a clear link between sedimentation in the area and glacial–interglacial climate-driven sea-level changes. This study also highlights the feasibility of astronomical tuning to obtain high-resolution chronology for shallow shelf deposits, which is otherwise very difficult to be achieved on the basis of magnetostratigraphic data alone.

Middle Pleistocene (MIS 7) to Holocene fossil insect assemblages from the Old Crow basin, northern Yukon, Canada

The Old Crow basin, northern Yukon, provides a key record of environmental change in northwestern North America from the late-Middle Pleistocene through the Early Holocene. Site chronologies are based on the presence of the Old Crow tephra (OCt: 124 ± 10 ka) at three sites, and provide a stratigraphic framework for observations. Ecological affinities of fossil insects indicate that Pleistocene environments were dominated by dry tundra and steppe-tundra. Forest insect species are relatively rare even during the last interglaciation (MIS 5e), and it is only by considering the total insect assemblages that interglacial beds can be recognized. Last interglacial insects from these sites indicate a relatively wet and warm tundra environment with evidence for sparse forest vegetation. Rare taxa with strong affinities to warmer temperatures are present and could suggest a warmer than modern climate. Early Holocene deposits yield a greater abundance of forest insects relative to MIS 5 or 7 interglacial deposits. Fossil insect assemblages reflect the position of the sites above the Arctic Circle, and in contrast to central Yukon sites, steppe insects are less common during cold stages and forest insects are less common during warm stages. These data suggest overall that the contrast between cold and warm stages was less pronounced than in other regions of Yukon and Alaska, and may indicate influence of persistent large regional lakes during the Pleistocene.

Elsterian‐Holsteinian deposits at Kås Hoved, northern Denmark: sediments, foraminifera, ostracods, and stable isotopes

The coastal cliff section at Kås Hoved in northern Denmark represents one of the largest exposures of marine interglacial deposits in Europe. High‐resolution analyses of sediments, foraminifera, ostracods, and stable isotopes (oxygen and carbon) in glacial‐interglacial marine sediments from this section, as well as from two adjacent boreholes, are the basis for an interpretation of marine environmental and climatic change through the Late Elsterian‐Holsteinian glacial‐interglacial cycle. The overlying glacial deposits show two ice advances during the Saalian and Weichselian glaciations. The assemblages in the initial glacier‐proximal part of the marine Late Elsterian succession reveal fluctuations in the inflow of sediment‐loaded meltwater to the area. This is followed by faunal indication of glacier‐distal, open marine conditions, coinciding with a gradual climatic change from arctic to subarctic environments. Continuous marine sedimentation during the glacial‐interglacial transition is presumably a result of a large‐scale isostatic subsidence caused by the preceding extended Elsterian glaciation. The similarity of the climatic signature of the interglacial Holsteinian and Holocene assemblages in this region indicates that the Atlantic Ocean circulation was similar during these two interglacials, whereas Eemian interglacial assemblages indicate a comparatively high water temperature associated with an enhanced North Atlantic Current. The foraminiferal zones are correlated with other Elsterian‐Holsteinian sites in Denmark, as well as those in the type area for the Holsteinian interglacial in northern Germany and the southern North Sea. Correlation of the NW European Holsteinian succession with the marine isotope stages MIS 7, 9 or 11 is still unresolved.

Palaeoecology of a late MIS 7 interglacial deposit from eastern England

A multidisciplinary investigation was undertaken to establish the palaeoecology of three different fluvial depositional environments in the basal sediments of a richly fossiliferous channel infill at Whittlesey, eastern England, which is dated by amino acid racemization (AAR) to marine oxygen isotope stage (MIS) 7. Molluscan and coleopteran data indicate that the river flowed throughout the year, supporting extensive adjacent marshland. Palaeobotanical and insect evidence indicates that extensive deciduous woodland was present, and the ostracod evidence indicates that saline habitats were available locally, suggesting that sea level at the time was not much different to today. Pollen and insect data do not differentiate the three different depositional environments, in contrast to the molluscan and ostracod evidence. Temperature estimates based on insect and ostracod data indicate a ‘mutual mutual’ mean July temperature of 16–21 °C and −1 to 3 °C for January. This is the first fully interglacial fluvial fossil assemblage described so far for the River Nene catchment that is reliably dated to MIS 7. Of particular note is the molluscan assemblage, which contains eight exotic species, including Theodoxus danubialis – a species described previously in the United Kingdom only in MIS 11 deposits associated with the River Thames catchment. Also of note is the insect assemblage, which in contrast contains no exotic species – unlike other MIS 7 insect assemblages recorded so far in the United Kingdom. Together these faunal assemblages may suggest a hitherto uninvestigated phase of a British interglacial stage, which the AAR data indicate could be late in MIS 7. The possibility that this so far unique interglacial fossil assemblage is the result of a combination of local preservation potential and environmental factors, however, cannot be ruled out.

Podłoże i stratygrafia osadów czwartorzędowych w SW części Pojezierza Mazurskiego

W zbadanym obszarze w podlozu osadow czwartorzedowych wystepują liczne depresje i elewacje, ktorych powstanie jest prawdopodobnie związane z ruchami tektonicznymi, w mniejszym stopniu z deformacjami glacitektonicznymi. Osady czwartorzedowe zawierają osiem poziomow glin zwalowych: po dwa – zlodowacenia podlaskiego i krakowskiego, trzy – zlodowacenia środkowopolskiego i jeden – zlodowacenia baltyckiego. Lądolod zlodowacenia baltyckiego w czasie maksymalnego zasiegu zająl jedynie polnocną oraz zachodnią cześc terenu. SUBSTRATUM AND STRATIGRAPHY OF QUATERNARY DEPOSITS IN SOUTH-WESTERN MAZURY LAKELAND The studies have been carried through in the south-western part of the Mazury Lakeland situated in the upper Wkra and Drweca river drainage basins (Fig. 1). A small number of deep boreholes enabled an approximative only interpretation of topography of the bedrock composed of Maestrichtian marls and Lower Palaeocene sandstones (Fig. 2). The bedrock is distinctly inclined eastwards, with considerable elevations close to Żuromin and Ostroda and with a depression in Ilawa. Map of Quaternary substratum could be prepared with a greater accuracy (Fig. 3). One can easily find a set of deep depressions running from north-west to south-east. At both sides of these depressions substratum topography is quite different. To the south-west there are also deep depressions and aside them, just under the Quaternary deposits, there are Pliocene variegated clays. To the north-east, depressions are generally small and shallow but the whole area is formed mainly of brown coal formation. It makes an impression of “flooding” the previous topography of earlier Tertiary deposits by variegated clays. The present relief of Quaternary substratum is after all an effect of denudation as it is suggested by isolated patches of variegated clays in the northern area. Oligocene deposits occur in the Quaternary substratum mainly in depression bottoms. No examined interglacial sediments in the studied area made stratigraphy to be grounded on references to the surroundings, first of all to the Mlawa area. In the described region the Quaternary deposits are usually 70–l00 m thick and in the substratum depressions – even over 250 m. Generally, eight till horizons can be distinguished: two each of Cracovian (Mindel) and Podlasie (Gunz) glaciations, three of Middle-Polish (Riss) Glaciation and one – of Baltic (Wurm) Glaciation (Figs. 4 – 6). Three lowermost till horizons occur in substratum depressions only, the rest form already more or less continuous beds in a larger area. Some deposits of small rivers were also found; lack of larger rivers is caused by localization of the area in a watershed zone for most of Pleistocene. A more distinct, two-cyclic alluvial series in the western part of the area, was connected with Great (Holstein) Interglacial (Tab. 1); one-cyclic one close to Rybno – with an interglacistadial of Cracovian (Mindel) Glaciation (Fig. 6). The third, uppermost till horizon of Middle-Polish (Riss) Glaciation was referred to Mlawa Glacistadial. It forms vast morainic plateau in southern and south-eastern parts of the area (Fig. 7). On the plateau, there are fragments of fluvioglacial levels (fig. 8) and denuded end moraines, kames and eskers. Till horizon of Baltic (Wurm) Glaciation can be found only in the northern and western part of the area. Locally but especially in the south-western part on the area, this till series was removed by fluvioglacial erosion.

Okrzemki środkowego plejstocenu w osadach jeziornych z Krępca (Wyżyna Lubelska)

Osady jeziorne z profilu Krepiec 13 kolo Łecznej zostaly uznane na podstawie analizy pylkowej (Z. Janczyk-Kopikowa, 1980) za rownowiekowe z osadami z Ciechanek Krzesimowskich, ktore wedlug A. Środonia (1969) reprezentują interglacjal lubelski. W nawiązaniu do podzialu palinologicznego opisywanego profilu dokonano korelacji wydzielonych okresow rozwoju roślinności wyzszej z fazami rozwoju okrzemek – diatomofazami (KI, K2, K3). W obrebie diatomofaz wyrozniono ponadto ich cześci oraz subdiatomofazy reprezentujące poszczegolne etapy rozwoju jeziora interglacjalnego. MIDDLE PLEISTOCENE DIATOMS FROM LACUSTRINE DEPOSITS FROM KRĘPIEC (LUBUN UPLAND) A thick packet of lacustrine deposits, about 20 m thick, was found at depth from 21.15 m to 41.50 m in the Krepiec 13 borehole column. They are represented by silts varying in lithology and with intercalations of gyttja, peat and peaty silts. They are underlain by sands with boulders, resting on till, and overlain by sands, peats, clay silts, chalk gravels and sandy silts. The pollen analysis, carried out by Z. Janczyk-Kopikowa (in print), has shown that the Krepiec borehole column comprises Interglacial deposits coeval with those from Ciechanki Krzesimowskie. According to A. Środon (1969), the latter do not correspond to the Masovien I Interglacial but to the Lublin Interglacial. On the basis of palynological subdivision of the studied borehole column, the differentiated periods of development of higher plants were correlated with phases of development of diatoms – diatom phases (K1, K2, K3). The diatom phases were further subdivided into parts and diatom subphases representing individual stages in evolution of the interglacial lake (Fig. 2). The bulk of the studied lacustrie deposits from Krepiec, comprising diatom phases Kl, K2A and K3A, are characterized by predominance of nannoplankton diatoms Stephanodiscus and Cyclotella in the dominant group (Tables I – IV). Fragilaria crotonensis , Asterionella formosa and Synedra ulna and S. acus are fairly common in the subdominant group. Middle part of the studied column (diatom phase K2B) displays a transitional stage in the development of the lake, characterized by decrease of plankton, accompanied by increase in number of littoral, mainly epiphytic, and rheophilous species typical of flowing water. Upper part of the section (diatom phase K3B) is characterized by predominance of Melosira italica and Epithemia zebra and, subsequently, Synedra ulna and Fragilaria construens . The development of these species indicates a marked shallowing, eutrophication of waters in the lake, and its overgrowing by macrophytes. The changes are related to further amelioration of climate, recorded as an Interglacial optimum in the pollen spectrum (III) by Z. Janczyk-Kopikowa (in print). The Krepiec section seems most close to that of the Lichwm Interglacial from Gwoznica in south-western Byelorussia (G.G. Gruzman et al., 1975).

A new Middle Pleistocene interglacial record from Denmark: Chronostratigraphic correlation, palaeovegetation and fire dynamics

Previously only three terrestrial interglacial periods were known from southern Scandinavia, all of which could be relatively easily correlated within the central European stratigraphical framework. Here, we present a new interglacial–interstadial pollen, plant macrofossil and charcoal record from Trelde Klint, Denmark, and analyse its biostratigraphy, correlation with other European records, vegetation development, fire dynamics and absolute dating. Except for a slight truncation of the early part of the record, the pollen stratigraphy exhibits a full interglacial succession, including temperate trees (Quercus, Ulmus and Tilia) during its mesocratic stage. Macrofossil analysis allowed identification to species level for Quercus robur, Picea abies and two mosses. Conifers (Pinus and Picea) dominate the pollen record of the interglacial sequence, and the occurrence of Larix pollen in the top part of the interglacial record as well as in the interstadial sediments is especially indicative of this interglacial. The overall diversity of tree genera is rather low. These biostratigraphical features suggest that Trelde Klint is unique among Danish records, but it is similar to records from northern Germany. Numerical analyses (REVEALS and DCA) indicate that forests during the temperate stage were dense and that vegetation openness increased only towards the end of the interglacial, accompanied by increased fire occurrence. A short interstadial sequence with a dominance of Pinus and Betula and the presence of Larix is present above the interglacial deposit. We argue that lack of attention to differences in fire regimes may hamper understanding of between‐site correlations of interglacial pollen records. OSL dating, using a novel feldspar technique, yields an average age of 350±20 ka for the sandy sediments above the interglacial layers at Trelde Klint, suggesting that the whole interglacial–interstadial succession belongs to Marine Isotope Stage 11.

Interglacial Quaternary Sediments as Possible Natural Source of Anomalies of Harmful Chemical Elements in Lithuania

Based on the geochemical results of interglacial Quaternary sediments in Lithuania obtained during implementation of the project “CIKLAS” the possibility appeared to study if these sediments can be a natural source of 10 potentially harmful chemical elements: As, Ba, Cr, Cu, Mn, Mo, Ni, Pb, V, Zn. Total contents of Ni, Cu, Pb, Ba in all analysed samples were lower than maximum permissible concentrations MPC for soil, of Zn, V, Cr, Mn exceeded MPC values in not more than 4% of samples. The highest percentage of anomalous samples where MPC was exceeded was characteristic of Mo (21%) and As (12.6%) indicating that interglacial sediments enriched in organic matter comprise one of the possible natural sources of Mo and As anomalies in stream sediments of Lithuania.

Glaciology and volcanology on the centenary of Sigurður Þórarinsson's birth: a special issue

The year 2012 marks the centenary of the birth of the late Sigurður Þórarinsson, the first professor of geology at the University of Iceland. His legacy is widely recognized in the international geoscientific community and the highest award of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI), the Thorarinsson Medal, is awarded to scientists for outstanding contributions to volcanology. Sigurður’s influence on Icelandic geoscientists was immense both through his university teaching and scientific collaborations. Although his research spanned a broad range of geosciences, including e.g. physical geography, geomorphology, periglacial features, and studies of interglacial sediments and tectonic earthquakes, his main fields of research were glaciology and volcanology in a broad context. Sigurður was president of the Iceland Glaciological Society from 1969 till his death, leader of most of its annual expeditions to Vatnajökull from 1953, and co-editor and frequent contributor to its scientific journal Jökull. This special issue of Jökull is dedicated to Sigurður’s contribution to geosciences and long-lasting influence on research in glaciology and volcanology in Iceland. This special issue contains an overview of Sigurður Þórarinsson’s life and scientific career by Sigurður Steinþórsson, ten peer-reviewed papers on different aspects of glaciology, glacial geomorphology and volcanology, Sigurður’s principal research fields and three society documentaries by two of Sigurður’s travel companions.

Depositional environment and climate changes during the late Pleistocene as recorded by the Netiesos section in southern Lithuania

The Netiesos section in southern Lithuania exposes a late Pleistocene sedimentary sequence at a depth of between 17 and 4 m. An interdisciplinary study of the section investigated the environmental changes that occurred in the study area during the greater part of Marine Isotope Stage (MIS) 5. Geochemical, thermoluminescence, palaeontological (plant macro-remain, diatoms, fishbones) and magnetic susceptibility analyses were performed on numerous sediment samples. Chronological control of the sequence was provided by electron spin resonance (ESR), infrared optically stimulated luminescence (IR-OSL) and conventional radiocarbon dating methods. This interdisciplinary approach enabled the subdivision of the section into stratigraphic units reflecting environmental changes. According to chronological data, the development of the Netiesos palaeolake began at the end of the Medininkai (Saalian) glaciation, which is thought to correlate with MIS 6, and continued up to the thermophilous deciduous forests phase of the subsequent last interglacial of MIS 5. Sediments of the final phase of the interglacial are missing, as are the initial and final phases of the following early Nemunas (Weichselian) cooling (MIS 4). The palaeomagnetic Blake Event was recorded in the interglacial sediments. One of the richest palaeofloras in the East Baltic region was observed representing the second half of MIS 5. The implications of the results for the regional late Pleistocene climato-chronostratigraphy are discussed.

Eemian-Weichselian palaeoenvironmental record from the Mickūnai glacial depression (Eastern Lithuania)

An extensive area of distribution of palaeolacustrine sediments (sand, silt with humus and interlayers of gyttja), occurring above the Eemian (Merkinė) Interglacial deposits and below the relief forming the Upper Weichselian till, was determined in the Mickūnai glaciodepression (in the vicinities of Vilnius, East Lithuania). These sediments were interpreted as being formed in a shallow palaeolake or lacustrine system, which occupied the depression during the Early-Middle Weichselian. Four boreholes were drilled in the central part of the Mickūnai depression and their sections were studied using lithostratigraphic and pollen analyses and datings by the optically stimulated luminescence (OSL) method. On the basis of the lithological composition and pollen and spores data the studied sections were tentatively subdivided into thermomers (time periods with relatively warmer climate) and cryomers (time intervals with colder periods). In the Mickūnai site seven thermomers and eight cryomers occurring above the Eemian Interglacial were determined. The thermomers of Middle Weichselian, however, were defined only by slight climatic changes in the background of general climatic deterioration. The Mickūnai sequence reflects presence of nonglacial palaeoenvironments from the end of the Eemian Interglacial to the Late Weichselian ice advance.

Relative paleointensity and environmental magnetism since 1.2 Ma at IODP site U1305 (Eirik Drift, NW Atlantic)

Integrated Ocean Drilling Program (IODP) Expedition 303 to the North Atlantic in 2004 recovered rapidly deposited deep-sea sediments at IODP Site U1305 on Eirik Drift, located south of Greenland at 3460m water depth, along the path of the Western Boundary Under Current (WBUC). About 200m of sediment was sampled with u-channels from the composite section, providing a continuous record of paleomagnetic field directions and relative paleointensity (RPI) variations covering the past 1.2Myr. The age model, based on an oxygen isotope record, is consistent with the fit of the RPI record to a calibrated template, and indicates higher sedimentation rates during interglacials relative to glacial epochs. Magnetite grain-size and concentration proxies indicate higher concentrations of magnetite with larger grain sizes during interglacials. Enhanced interglacial deposition can be attributed to a combination of elevated entrainment of terrigenous detritus into the WBUC due to glacial retreat on continents flanking the upstream path of the WBUC (east Greenland and Iceland), and of increased bottom current (WBUC) vigor leading to elevated transport and deposition at the site during interglacials. This pattern is opposite to observations of flow of the Antarctic circum polar current (ACC) in the south Indian Ocean, which suggests an inter-hemispheric antiphase in marine circulation at the Milankovitch scale, with strong circulation in the deep North Atlantic when the ACC is weak, and vice versa.