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This study provides a 16.2-kyr record of mercury (Hg) deposition derived from a lacustrine sedimentary sequence in Dahu Swamp, eastern Nanling Mountains. Results indicate that changes in climatic conditions had a significant effect on Hg concentrations (Hg–C) and accumulation rates (Hg-AR). Multi-proxy records including dry density, grain size, geochemical elements, organic matter and pollen indicators were compared with Hg accumulation. The results revealed that the contributions of detrital input and atmospheric deposition were minor, and Hg accumulation in the sediments was closely related to changes in climatic conditions: relatively drier and colder climate would result in shrinkage of the lake water body thus favoring increased formation of organic-rich peat or gyttja and leading to enhanced absorption of Hg by organic matter and result in increases of Hg–C and Hg-AR in sediments, and vice versa. Our results indicate that variations of Hg accumulation in Dahu Swamp were greatly impacted by climate under the influences of solar insolation changes and shrinkage or expansion of ice sheets in high latitudes to the north. The results of this study provide an insight into the response of Hg accumulation to low latitude climate processes in the East Asian summer monsoon region.

This paper presents the first result of a study of two long-term natural archives in the southwestern part of the Western Siberian Plain. Bchron age models based on 17 AMS dates allowed us to determine a chronology of changes in properties of lake and peat deposits. Significant changes in the Holocene were identified according to geochemical indices, accumulation rates, and compositions of the plant macrofossils of sediment cores in Lake Kyrtyma and Oshukovskoe peat bog. Sediments with a low content of organic matter and maximum weathering accumulated in the Late Glacial, below the border of the Holocene. The transition to the Holocene manifested as a black organic gyttja with ostracods and marked warming ∼12–11.2 ka BP. At about 11.2–10.1 ka BP it was replaced by the Preboreal oscillation. Subsequent changes in lake sedimentation were associated with general warming and an unstable hydrological regime. An increase in humidification ∼8.2 ka BP was reflected by lake level rise and contributed to swamping of the watersheds. The aridest Holocene phase at ∼7.1–5.5 ka BP was reliably recorded by geochemical data, but poorly reflected in the stratigraphy of both profiles. Subsequent cooling and the resulting decrease in evaporation began at ∼5.5–4.9 ka BP. A pronounced cardinal shift in sedimentation conditions due to a gradual increase in precipitation was recorded at ∼4.9–2.8 ka BP, though short-term fluctuations towards dryness were also marked at ∼3.5–3.3 ka BP. The most significant increase in humidification and cooling began at 2.8 ka BP. Geochemical indices in the lacustrine sediments are climate sensitive and allowing us to obtain enough reliable data associated with changes in sedimentation environments. The stratigraphy of peat reflected the nuances of climatic changes less clearly and primarily demonstrated the stages of bog self-development; however, sphagnum peat provided a better-resolution record.

We present a case study of a bog showing how an integrated approach of multi-method geophysical sounding and local soil sampling can be used to identify, differentiate, and map organic sediments. Our study is based on ground-penetrating radar (GPR), electrical resistivity tomography (ERT) and shear-wave seismic (SH seismic) profiling applied to sediments of the former Lake Duvensee (northern Germany), nowadays a bog. This is a well-known locality for remains from the Mesolithic hunter-gatherers&rsquo, occupation that has been attracting archaeological and geoarchaeological research for100 years. The bog is embedded in low conductive glacial sand and is characterized by layers of different gyttja sediments (detritus and calcareous). The present study was conducted in order to identify the bog morphology and the thickness of the peat body and lake sediments, in order to understand the basin evolution. To validate the geophysical results, derived from surface measurements, drilling, soil analyses as well as borehole guided wave analysis of electromagnetic waves and Direct-Push (DP-EC) have been carried out and used for comparison. It turned out that each method can distinguish between sediments that differ in grain size, particularly between peat, lake sediments (gyttjas and mud) and basal glacial sand deposits. GPR is even able to separate between strongly and weakly decomposed peat layers, which is also clear considering resistivity variations in the ERT computation. From the association between geophysical properties and sediment analysis (e.g., water content and organic matter) different gyttjas were distinguished (coarse and fine) and seismic velocity was correlated to bulk density. Moreover, GPR and SH-wave seismics present different resolutions, confirming that the latter allows measurements, which are more focused on determining the extension of basal sand deposits, the depth of which is difficult to reach with GPR. Representative values of electrical resistivity, dielectric permittivity, and shear wave velocity have been determined for each sediment type and are therefore available to complete the investigation of wetland environments. Fine grained lake sediments were difficult to differentiate by the applied methods. This could be a result of high ionic concentration within the permanent groundwater body, partly masking the sediment properties.

Five sections of sediment from mire infillings located in different part of the catchment small river valley in central Europe were studied by lithological and geochemical analysis in order to examine the response of aquatic ecosystems to the environment changes during Late Weischselian (LW). Differentiation of geochemical composition and grain-size properties in biogenic deposits is being considered as a result of change hydroclimatic conditions and geology structure in individual parts of the catchment. The principal component analysis (PCA) and clustered by hierarchical method (HCA) were chosen to create the lithogeochemical facies and their chronostratigraphy variability. Biogenic sediments of the studied river mires, regardless of the location in a given reach of the valley, are represents mainly by mineral or organic-mineral lithogeochemial facies with increased of lithophilic elements (Na, K and Mg). Similar chemical composition of gyttja and peat sediments in almost all periods of LW, indicate the strongly mechanical denudation processes in the Grabia River valley. The major process, conditioning the development of the mires (in it type and rate sedimentation), was the variable terrigenous material input which are related to its variable dynamic of floods. The higher than expected chemical denudation probably a result of specific groundwater flow direction and dissolving vari-grained sands and silts, which build plains in the central part of the study catchment. The number and thickness of individual lithogeochemical facies are caused by differences in the potential volume of the hydrologically active zone and geological conditions of the emerge or disappear permafrost.

Despite recent progress in understanding high-latitude climate variability, paleoclimate records are scarce from the Alaskan Arctic. We conducted isotopic and sediment analyses at Wahoo Lake to infer Holocene climate variability in northeastern Alaska. Water δ18O and δD values from the lake and its inlet/outlet streams suggest that winter precipitation dominates modern water inputs and that evaporation has limited influence on the lake’s hydrological budget. The isotopic composition of Pisidium exhibits marked variations during the past 11,500 years, with δ18O ranging between −18.7‰ and −16.2‰ and δ13C between −7.1‰ and −2.3‰ (Vienna Pee Dee Belemnite (VPDB)). Elevated δ18O and sediment composition from 11.5 to 8.9 kcal. BP suggest evaporative 18O enrichment and arid conditions. Rising lake levels are evidenced by the disappearance of Pisidium and a transition to low-carbonate gyttja ca. 6.3 kcal. BP and by the onset of sediment deposition on an adjacent shelf by 5.3 kcal. BP. These changes coincided with enhanced effective moisture in interior and southern Alaska as inferred from lake-level records and may be related to broad-scale atmospheric circulation changes. In the shelf sediments, carbonate abundance increases markedly at 3.5 kcal. BP, and δ18O increases from −18.0‰ to −16.5‰ at 2.1 kcal. BP, possibly resulting from increased temperature and/or summer precipitation. After 2.1 kcal. BP, δ18O fluctuates with an overall decreasing trend to −17.2‰ at 0.9 kcal. BP. Late-Holocene variations in our δ18O record display coherent patterns with regional glacier fluctuations at centennial to millennial scales, suggesting that δ18O minima were related to a combination of low temperatures and enhanced winter snowfall. Holocene variations in organic matter abundance at Wahoo Lake also show broad similarities to total solar irradiance, implying that suborbital solar variability played a role in modulating regional climate and aquatic productivity.

Organic-rich freshwater sediments formed from the remains of water plants, plankton and benthic organisms, which are transformed by microorganisms, and mixed with mineral components supplied from the lake basin, are known as gyttja (sapropel or dy). Gyttja is a valuable natural resource that can be used in various fields such as agriculture, forestry, construction, chemical industry, balneology and the latter ones are especially interested in chemical composition and safety of natural materials. The aim of the study was to investigate micro- and macro-element content of gyttja derived from lakes of eastern Latvia (north-east of Europe). Depending on composition, sediment samples were identified as peaty, various algae, green algae, diatom, carbonate and organic-silicate types of gyttja. Dried samples were wet-digested by heating in HNO3/H2O2 solution until complete mineralization. Sample solutions were analysed by atomic absorption spectrometry (AAS) to detect concentration of Ca, Fe, K, Mg, Mn, Na and Zn, but inductively coupled plasma mass spectrometry (ICP-MS) was applied for As, Ba, Cd, Co, Cr, Cu, Li, Ni, Pb, Rb, Se, Sr and V concentration measurements. Total content of elements was variable; higher macroelement concentration was detected for gyttja of carbonate type, but higher microelement concentration-for organic-silicate gyttja. As concentration of several elements was much lower than permitted by the European Union legislation, gyttja is not only safe, but also highly valuable resource applicable in organic agriculture. There is a potential to use gyttja as a peloid in health care, but element bioavailability should be estimated likewise.

Heavy metals which pollute aquatic environments typically bond with bottom sediments and the analysis of the spatial distribution of metals allows to assess the geochemical purity of deposits and to identify the potential pollution sources. Research carried out on the Wigry Lake involved the collection of almost 500 samples of sediments, and the specification of the depth of their residence (0.2–71.4 m) as well as the level of concentration of three metals: Fe (80.3–32 857 mg kg−1), Mn (17.8–1698 mg kg−1) and Zn (3.14–632 mg kg−1). The geochemical and bathymetric data was interpolated using geostatistical methods and mapped with the consideration of 5 types of sediments: lacustrine chalk, carbonate gyttja, fluvial-lacustrine sediment, organic gyttja and clastic sediment. As a result, a significant increase in the concentration of metals was revealed in deeper zones, at a considerable distance from the lake shore, wherein the respective values of correlation coefficients were as follows: depth–Mn 0.77; depth–Fe 0.60; depth–Zn 0.58. A strong dependency between the concentration of analysed metals and the type of sediment, attributed to the granular and chemical composition of sediments, was also revealed. Correlations between individual metallic pairs (Fe–Mn 0.77; Fe–Zn 0.80; Mn–Zn 0.75) indicated that similar factors influence spatial distribution of metals in sediments. The implementation of 3 different geochemical backgrounds allowed to conclude that the Wigry Lake is slightly polluted with the analysed metals, and that the origin of Mn is mainly natural, while in the case of Fe and Zn anthropogenic influence can also be identified.

WOS: 000377882700006, Lake Neor is the largest lacustrine basin in the high mountains of the Middle East, at 2500 m altitude in the Alborz belt. This lake of Holocene age is a shallow, fresh water body of glacial origin with ca 4 km(2) surface area and a 40 km(2) drainage area. Its sedimentary sequence comprised of peat and gyttja consists of >10 m infill, which is fairly thick for such a lake. Autochthonous organic matter is limited in and around the lake except for small areas at the northern and southern ends. Inorganic constituents of the infill sediment include a significant amount of fine-grained calcite, dolomite and mica particles that are exotic to the catchment. They do not occur in the source rocks, as the drainage area of the lake is composed of only andesites and trachyandesites of Eocene age. In addition, the uppermost part of the infill includes abundant fine-grained charcoal particles derived from large forest fires perhaps derived as far as the Mediterranean region. As shown by the present meteorological records, the sediment of Lake Neor is under aeolian control during dust storms; this is leading to a considerable amount of deposition air-borne particles. The infill of some lakes, particularly those in highlands, may have contain an important aeolian component and thus they cannot be used directly for the interpretation of the evolution of the palaeogeography without taking into consideration the role of dust storms on deposition. Crown Copyright (C) 2015 Published by Elsevier Ltd. All rights reserved., Ankara University [12B434002]; [1227], The study has been supported by a research project of Ankara University (no 12B434002). Figures were drawn by Yasar Suludere. Water analyses of the lake were provided by the Ardabil Directorate for Environment Protection of Iran. Stephen Kershaw and Lorna Anguilano from Brunel University London critically read the original version. Mike Turner (Brunel University London) has kindly revised the English of the manuscript. Authors are grateful for all support. The publication is a contribution to the INQUA QuickLakeH project (No 1227).

X-ray fluorescence (XRF) core scanning has become widely available for geological studies during the last decade. The data obtained from XRF core scanning, however, may be strongly influenced by the amount of organic matter, water content, density and porosity of the sediment matrix. In this study we discuss the usefulness of XRF core scanning to distinguish different kinds of organic-rich sediments and peat based on examples from tropical Lakes Kumphawapi and Nong Leng Sai in Thailand. We examined how sedimentary factors influence XRF core scanning analyses by comparing elemental and scattering ratios to lithological changes and quantitative LOI, TOC, biogenic silica (BSi) and grain-size values. Our comparison suggests that the (inc/coh) scattering ratio is of limited use as an indicator for variations in LOI and TOC in peaty gyttja or peat. In Lake Kumphawapi's sediments, Si/Ti ratios reflect clastic input associated with grain-size variations rather than BSi contents. The Ti-normalized ratios of Si, Zr, Sr, K and Rb are linked to mineral input and associated grain-size variations. We conclude that XRF core scanning of organic-rich tropical lake sediments and peat is useful to infer palaeoenvironmental conditions. However, XRF core scanning data does not stand-alone and needs to be underpinned by additional proxies.

The results of lithological analysis, diatom analysis and radiocarbon dating of bottom sediments from the basin of a lake located at an elevation of 17 m above sea level near the Teriberka settlement (Barents Sea coast, Kola Peninsula) are presented. The stages of the lake evolution were revealed based on a comprehensive investigation of its bottom sediments. The lake basin was covered by sea at the end of the Pleistocene. The lake became isolated from the sea approximately 11500 cal. yrs BP, but was re-filled with sea water after 10400 cal. yrs BP due to the Tapes transgression. In lower part of the Tapes sediments, there is a disturbance of the sediment sequence, represented by a mixture of sand, gyttja and plant residues. According to radiocarbon dates, this disturbed hori­zon was deposited between 10400 and 8200 cal. yrs BP. An abrupt increase in the con­tent of marine diatoms was found in this horizon. The disturbed sediments have possibly formed as a result of the Storegga tsunami. When the horizon of tsunamigenic sediments was forming, the sea level was slightly above the threshold for discharge from the lake (ca. 18 m above modern sea level). The second local event (tsunami?) occurred after 8220 cal. yrs BP, when the coastline was already below the lake threshold. As a result of this event, an interlayer of sandy sediments formed in the bottom sediments within gyttja.

This paper presents the results of an assessment of macro- and microelements in the sediments of lakes laying within protected areas in Poland – the Drawa National Park, the Wel Landscape Park and the Górzno-Lidzbark Landscape Park. In each lake two grab sediment sample were collected: one in the littoral zone and the other in the deepest part of the lake basin. Sediment samples analysed for their content of inorganic carbon (IC) and the loss on ignition (LOI at 550°C) and, according to these parameters classified into three sediment types. Micro elements were detected with SEM-EDX system and the bioavailability of Zn, Cu, and Fe was evaluated after an extraction with DTPA (diethylenetriaminepentaacetic acid) solution. The most diverse chemical composition of the sediments was observed in the lakes of the Wel Landscape Park Lacustrine sediments were characterized by the heterogeneous content of organic matter (from 11.70 to 52.89%), calcium carbonate (from 0.0 to 42.73%) and mineral fractions (from 38.24 to 79.46%). They consisted of three different types of gyttja (fine grain-size, clayey-calcareous, clayey). The highest content of trace elements was determined in fine grain-size gyttja, which results from their current sorption properties, as well as alimentation by river waters flowing into the lakes. The sediments contained relatively low concentrations of the analysed elements, which was reflected in the low values of the contamination factor (CF), the contamination degree (Cdeg), the geo-accumulation index (Igeo) and the enrichment factor (EF). Values of the Igeo point out also that these lake sediments were not contaminated by heavy metals. The total content of zinc and copper in some analyzed sediments was higher than the content assumed as acceptable for protected areas. The contribution of bioavailable forms of Zn and Cu ranges from 2.3 to 29.1% for Zn, and from 4.6 to 18.4% for Cu. The type of sediment, and the surface area largely determined the lake sediment chemical composition, while land-use in the catchments had a minor effect. This applies to both lakes of different parks and lakes within each of the parks.

Hjarno Sund is one of 37 submerged archaeological sites that have been recorded in the 15-km-long Horsens Fjord. It is now located in a water depth of 0.5–2 m. Until recently, the gyttja deposits containing the archaeological material were covered with a protective layer of sand. Recent erosion by water currents has exposed the archaeological material and prompted detailed investigation before further damage occurs. Methods of investigation include underwater excavation and sediment coring, which have revealed a rich collection of material ranging in age from the late Kongemosen to the Middle Ertebolle. The deposits include two shell-midden layers dominated by oysters and cockles, which contain concentrations of flint artefacts and bones of fish and mammals, and layers of gyttja, from which artefacts of bone, antler and wood have been recovered. Of particular interest are decorated antler axes, one of which was found hafted on a wooden handle, and two wooden paddles decorated with distinctive painted designs. An extensive cultural deposit is still protected by overlying sediments, and would repay further excavation, especially given the threat of destruction by erosion.

Studies of infills of present-day peatland basins of the Łódź Region revealed the presence of lacustrine sediments underlying peats. They usually rest on mineral bottoms of basins, and their accumulation began in the Late Vistulian and continued in the Holocene. Out of 17 objects subjected to geological and palaeoecological examinations such arrangement was found in 8 of them. In the locality of the Żabieniec peatland 16.4 m of biogenic sediments was documented. The essential part of the profile contains detrital gyttja (at the bottom – detrital-clay gyttja, above – fine detrital gyttja). Within the Ner-Zawada peatland the thickness of biogenic sediments is 4.70 m and lake sediments are represented by clay- calcareous gyttja and calcareous gyttja. The thickness of biogenic sediments in the Ługi peatland reaches to 2.90 m. At this locality detrital- calcareous gyttja and detrital gyttja accumulated on the mineral substratum. In the Rąbień peatland basin the thickness of lacustrine sediments and peat reaches 6.2 m; on sandy bottom rest detrital-clay gyttja and detrital gyttja. In the Silne Błoto-Witów peatland only the 3.5 m long profile of the so- called “west island” contains lacustrine deposits covered by herbaceous peat. In the bottoms of a few other peatlands of the region, biogenic lake deposits were found, but their thickness is small (such as Korzeń, Bęczkowice, Parchliny). Therefore it may be assumed that some peatlands of the Łódź Region are of limnic origin. The presented examples of lake sediment series in the basins of contemporary peatlands in the Łódź Region allow to conclude that during the last fifteen thousand years, lakes occurred in this area, not only in numerous oxbow basins, but also in plateau depressions and aeolian landforms. Lake basins were more frequent during the late Vistulian, and survived in the Holocene until the Subboreal period. All water bodies of wetlands of the Łódź Region, except for oxbows, which are observed today, are of an anthropogenic origin. Analiza wypełnień mis współczesnych torfowisk regionu łódzkiego wykazała pod torfami obecność osadów jeziornych. Zalegają one zwykle na mineralnym dnie mis, a ich akumulacja rozpoczęła się w późnym vistulianie i trwała jeszcze w holocenie. Spośród 17 obiektów poddanych szczegółowym badaniom geologicznym i paleoekologicznym taki układ osadów stwierdzono w ośmiu z nich. W misie torfowiska Żabieniec udokumentowano 16,4 m osadów biogenicznych, a zasadniczą część profilu stanowi gytia detrytusowa (w dolnej części detrytusowo-ilasta, a powyżej gytia drobnodetrytusowa i grubodetrytusowa). W obrębie torfowiska Ner-Zawada miąższość osadów biogenicznych wynosi 4,70 m, a osady jeziorne reprezentują: gytia ilasto-wapienna i gytia wapienna. Miąższość osadów biogenicznych w obrębie torfowiska Ługi sięga 2,90 m, na mineralnym podłożu zalega gytia detry- tusowo-wapienna i gytia detrytusowa. W torfowisku Rąbień miąższość torfu i podścielających go osadów jeziornych sięga 6,2 m, na piaszczystym podłożu zalegają: gytia detrytusowo-ilasta i gytia detrytusowa. Torfowisko Silne Błoto-Witów dokumentuje jedynie profil z tzw. wyspy zachodniej o miąższości 3,5 m prezentujący głównie osady jeziorne, przykryte przez torf zielny. W podłożu torfów kilku innych torfowisk regionu stwierdzono biogeniczne utwory jeziorne, ale ich miąższość jest niewielka (m.in.: Korzeń, Bęczkowice, Parchliny). Uznać więc należy, że część torfowisk regionu łódzkiego ma pochodzenie limnogeniczne. Zaprezentowane przykłady serii osadów jeziornych w misach współczesnych torfowisk regionu łódzkiego pozwalają stwierdzić, że w trakcie ostatnich 15 tysięcy lat jeziora występowały na tym obszarze nie tylko w licznych starorzeczach, ale także w obniżeniach wysoczyznowych i wśród form eolicznych. Zbiorniki jeziorne funkcjonowały liczniej w okresie późnego vistulianu, a w holocenie przetrwały aż do okresu subborealnego. Wszystkie zbiorniki wodne na obszarach mokradeł regionu łódzkiego, poza starorzeczami, obserwowane współcześnie, mają charakter antropogeniczny.

The composite sediment profile (12.39 m) from Lake Szurpily (NE Poland) represents an annually laminated organic-carbonaceous gyttja occasionally interrupted by turbidites and massive sand layers. This study focuses on the 7.58-m long and almost continuously varved top section of the profile, which produced a 8410-year long varve chronology with a cumulative counting error of ± 1.24%. The age-depth model was established by multiple microscopic varve counts and improved by the application of independent radiometric dating methods (210Pb, 137Cs). Ten additional AMS 14C dates are consistent with varve counts. In some sections, missing varves were identified as a result of erosional processes related to turbidite deposition. Varve thickness ranges from less than 0.1 to 13.7 mm (mean: 0.83 mm; std: 0.75 mm) with highest variability during the last 1500 years. The accuracy of the varve chronology depends mostly on the regularity of the varve thickness and the distinctness of varve boundaries, and was not influe...

This study presents a detailed analysis of geochemical and biotic proxies in a lake sediment profile to assess the effects of local and regional environmental drivers on the Holocene development of Lake Loitsana, situated in the northern boreal forest of NE Finland. Multi-proxy studies, in particular those that include a detailed plant macrofossil record, from the part of the northern boreal zone of Fennoscandia which has not been affected by treeline fluctuations, are scarce and few of these records date back to the earliest part of the Holocene. A 9-m sediment sequence of gyttja overlying silts representing the last c. 10,700 cal year, allowed for a high-resolution study with emphasis on the early to mid-Holocene lake history. The lacustrine sediments were studied using lithology, loss-on-ignition and C/N ratios, micro- and macro-fossils of aquatic and wetland taxa, diatoms, chironomids and accelerator mass spectrometry 14C dating on terrestrial plant macrofossils. Our study shows that the local development at Loitsana was complex and included a distinct glacial lake phase and subsequent drainage, a history of fluvial input affected by nearby wetland expansion, and lake infilling in an eventual esker-fed shallow lake. Enhanced trophic conditions, due to morphometric eutrophication, are recorded as Glacial Lake Sokli drained and open water conditions became restricted to a relatively small Lake Loitsana depression. pH appears to have been stable throughout the Holocene with a well-buffered lake due to the local carbonatite bedrock (Sokli Carbonatite Massif). The fossil assemblage changes are best explained by a complex mixture of drivers, including water-body conditions (i.e. depth, turbidity and turbulence), rate of sediment input, and the general infilling of the lake, highlighting the need to carefully evaluate the possible influence of such local factors as palaeoenvironmental conditions are reconstructed based on aquatic proxies.

The development of a glacial lake impounded along the retreating, northeastern ice margin of the Fennoscandian Ice Sheet during the last deglaciation and environmental conditions directly following the early Holocene deglaciation have been studied in NE Finland. This so-called Sokli Ice Lake has been reconstructed previously using topographic and geomorphologic evidence. In this paper a multiproxy approach is employed to study a 3-m-thick sediment succession consisting of laminated silts grading into gyttja cored in Lake Loitsana, a remnant of the Sokli Ice Lake. Variations in the sediment and siliceous microfossil records indicate distinct changes in water depth and lake size in the Loitsana basin as the Sokli Ice Lake was drained through various spillways opening up along the retreating ice front. Geochemical data (XRF core-scanning) show changes in the influence of regional catchment geochemistry (Precambrian crystalline rocks) in the glacial lake drainage area versus local catchment geochemistry (Sokli Carbonatite Massif) within the Lake Loitsana drainage area during the lake evolution. Principal component analysis on the geochemical data further suggests that grain-size is an additional factor responsible for the variability of the sediment geochemistry record. The trophic state of the lake changed drastically as a result of morphometric eutrophication once the glacial lake developed into Lake Loitsana. The AMS radiocarbon dating on tree birch seeds found in the glaciolacustrine sediment indicates that Lake Loitsana was deglaciated sometime prior to 10 700 cal. a BP showing that tree Betula was present on the deglaciated land surrounding the glacial lake. Although glacial lakes covered large areas of northern Finland during the last deglaciation, only few glaciolacustrine sediment successions have been studied in any detail. Our study shows the potential of these sediments for multiproxy analysis and contributes to the reconstruction of environmental conditions in NE Finland directly following deglaciation in the early Holocene.

The northern part of the Mazury Lake District is marked by the presence of a depression described as the Skaliska Basin. At the end of the Pleistocene, the Skaliska Basin was the site of functioning of a thaw lake, within series of laminated clayey sediments were formed. The surface of the clayey sediments was overlain by a sandy fan. Blocks of dead ice underlying the fan and the overlying surface of the clayey sediments were the origin of small isolated water basins. Since the Allerod they were filled with limnic sediments, passing into peats towards the upper part. In order to reconstruct the vegetational history of the Skaliska Basin and the conditions of sedimentation of the lacustrine gyttjas and peats, several sections were obtained from such basins and subjected to examination of plant macroremains, palaeolimnological analysis and AMS dating. Sedimentation of lacustrine sediments began with sands with an admixture of silt and peat. The beginning of sedimentation of lacustrine sands of aeolian origin falls within the Allerod, whereas the end of that process in ca the middle of the Preboreal. Sands are frequently overlain by a strongly decomposed lacustrine dy sediment. Subsequently a sequence of detritus gyttja accumulated. The complex of gyttjas is interbedded with occasional Scirpo-Typheti peats. Sedimentation of lacustrine sediments is followed by accumulation of peats formed within communities with tall sedges. These communities, according to their compoition, correspond to the associations of Cicuto- Caricetum pseudocyperi Boer. et Siss. and Caricetum elatae Koch. The upper part comprises peats resembling the present-day community of Sphagnum centrale, displaying features of a transition bog. Also the occurrence of Eriophorum vaginatum confirms changes towards ombrotrophic conditions. The uppermost part of the sections often comprises heavily decomposed peat with components no longer identifiable by macroscopic analysis.

This study uses the Holocene lake sediment of Lake Ķūži (Latvia, Vidzeme Heights) for environmental reconstruction with multi-proxy records including lithology, computerised axial tomography scan, grain-size analysis, geochemistry, diatoms and macrofossils, supported by AMS radiocarbon dating. Numerical analyses (PCA; CONISS) reveal three main phases in the development of the lake. Response to the Lateglacial–Holocene transition in Lake Ķūži took place around 11,300 cal. BP. Organogenic sedimentation started with distinctive 5-cm-thick peat layer and was followed by lacustrine sedimentation of carbonaceous gyttja. Several findings of the peat layer with similar dated age and position at different absolute altitudes indicate that lake basin was formed by glaciokarstic processes. In the Early Holocene (until around 8,500 cal. BP), the lake was shallow and holomictic, surrounded by unstable catchment with erosion and inflow events. Predominance of diatom species of Cyclotella and Tabellaria, large numbers of respiratory horns of phantom midge pupae (Chaoboridae), high Fe/Mn ratio, as well as the presence of laminated sediments indicates the transition to a dimictic and oligo-mesotrophic lake conditions with high water level, anoxia in the near-bottom and stable catchment in the Middle Holocene (8,500–2,000 cal. BP). This contrasts with many hydrologically sensitive lakes in Northern and Eastern Europe in which the water level fell several meters during this period. During the Late Holocene (from 2,000 cal. BP to the present), the lithological and biotic variables reveal major changes, such as the increase in erosion (coarser grain-size fraction) and eutrophication [diatoms Aulacoseira ambigua (Grun.) Sim., Stephanodiscus spp., Cyclostephanos dubius (Fricke) Round]. Characteristics of lake-catchment system during the Late Holocene reflect anthropogenic signal superimposed on the natural forcing factors. To date, the Late Quaternary palaeolimnological reconstructions using lake sediment has been limited in the Baltic region. Therefore, findings from Lake Ķūži provide important information about environmental and climatic changes that took place in this part of Eastern Europe. This study shows that the relative importance of climate and local factors has varied over the time and it is essential to consider the lake basin topography, catchment size and land cover as potential dominant forcing factors for changes in sedimentary signal.

Post-isolation (9,600 year BP) sedimentology in Lake Pyhajarvi, Finland, was studied using sub-bottom echo-sounding and sediment coring. The sediment sequence appeared in the echo-sounding profiles as two sections: (1) a lower section of homogenous, light grey gyttja clays, and (2) an upper section with dark layers of mainly clay gyttjas and gyttjas, here referred to as C_gyttja. We investigated the thickness and volume of sediments as well as their morphology and areas of accumulation. Approximately 77 % of the lake represents areas of accumulation, containing 34 and 1.3 million tons of dry matter and carbon, respectively. Spatial variability in sedimentological properties indicates that accumulation in the Kirkkoselka sub-basin was focused into the deepest areas since lake isolation. In the Isoselka sub-basin, however, accumulation was focused partially onto the flanks of the depression, whereas the deepest parts (23–27 m) of the sub-basin represent erosional areas. There appears to have also been sediment re-suspension and re-deposition, as indicated by erosion surfaces. This, combined with dune-like bottom morphology in the accumulation areas, provides evidence for the role of wind-driven bottom currents on sedimentation dynamics in the Isoselka sub-basin. Increases in Cu and Zn concentrations, driven by Pyhasalmi mining activities, were used as a geochemical marker for recent sedimentation (RS) between 1966 and 2008. As a consequence of wind-driven bottom currents, 60 % of the metals accumulated in the Kirkkoselka sub-basin and 40 % accumulated in the Isoselka sub-basin. There is a spatial correlation between amounts of C_gyttja and RS. In the middle of dune-like C_gyttja formations in the Isoselka sub-basin, the RS grain size is smaller than in other areas. Variations in RS are greatest along the borders of the accumulation area, likely a consequence of bottom currents in those areas.

On two short sediment cores from Lake Łazduny (northeastern Poland) different methods for age estimation were applied including varve counting, 210Pb, 137Cs and OSL dating. The investigated sediment consists of finely laminated, organic-rich calcareous gyttja interrupted by a sand layer. For 210Pb we tested the CFCS, CIC, CRS and SIT models and compared the results with the established varve chronology and the 137Cs distribution. The total 210Pb activity distribution is consistent between cores and shows a regular decrease with depth. However, the total inventory of unsupported 210Pb was significantly different and indicates varying rates of sediment focusing. Our results show that all 210Pb dating models used in this study produced different results, while the SIT model performed best in comparison with varve counts and 137Cs peaks. The CFCS model produced a realistic age-depth trend but obtained ages were too old compared to the varve time scale. The age estimates provided by the CRS model were too old as well with an increasing offset downcore and the CIC model failed completely by producing an unrealistic chronology with age inversions. This confirms that only systematic testing of different 210Pb dating models and routine validation using independent time markers produces reliable 210Pb chronologies. OSL dating of two samples from the sand layer provided much too old results which indicate incomplete bleaching during deposition of the analyzed quartz grains. This multiple dating approach demonstrates the considerable potential but also potential pitfalls of dating such young sediments.

Macrofossil analysis and radiocarbon dating were used to determine the age, composition and succession pattern of organic-rich deposits infilling oxbows and flood basins in the Rivers Kłodnica, Odra and Osobłoga valleys (southern Poland). Both detrital sediments representing the aquatic or terrestrial environments as well as five types of peat accumulated in amphibious or peatland conditions have been identified in cores analyzed. Studies have shown that an accumulation of organic-rich deposits was commonly initiated by terrestrialisation and was typically occurred under eutrophic conditions. In such circumstances, deposit sequences usually begin with aquatic detrital sediment (gyttja), or possibly brown-moss or reed peat. These deposits normally pass into sedge-reed peat and then alder peat. If the accumulation of organic-rich deposits was initiated by paludification, alder peat appears in the lowest sections of the fens. In the upper parts of the sequences, apart from wood peat, organic deposits dominated by sedge remains are also present. The latter were accumulated, probably, as an indirect effect of human activities in the floodplains.

The Lateglacial and postglacial sequence in the northern Gulf of Riga is sedimentologically subdivided into nine distinctive layers. In the seismo-acoustic sequence these layers are correlated with seven seismic/acoustic units, which largely reflect different stages in the development of the Baltic Sea. A uniform layer of the Late Weichselian till, a layer of waterlain glacial diamicton (WGD), a varved succession of the Baltic Ice Lake, a brackish-water/freshwater sandy/silty clay of Yoldia Sea, a FeS-rich layer of Ancylus Lake and discordantly bedded sand of the Litorina Sea and present-day gyttja are revealed both in sediment cores and in acoustic recordings. In general, the lateral extent of the distinguished sediment layers is gradually shrinking upwards in the Quaternary sequence towards the deepest, central depression of the gulf. Two distinguished regional discontinuities divide the Lateglacial and postglacial sediment sequence into three allounits: glacial diamicton deposits in the lower part; ice-proximal WGD, glaciolacustrine and postglacial lake/marine deposits in the middle; and brackish-water marine deposits in the uppermost part of the sequence. The presented detailed seismostratigraphic subdivision of the Quaternary sediment sequence of the Gulf of Riga permits a correlation/comparison with similar sequences across the Baltic Sea and in other former glaciated basins.

Paleoenvironmental reconstruction combining data from diatom, pollen, macrophytic, and archaeological analyses had not been attempted previously for coastal Peru. We analyzed two radiocarbon-dated sediment cores extracted from the “sacred” Urpi Kocha Lagoon at the pre-Hispanic religious center of Pachacamac (ca. AD 350–1533), near Lima, to characterize the paleoenvironment of the site. The data reveal an environmental history characterized by alternating periods of severe drought and catastrophic flood. Recurrent pulses with distinctive sediment, diatom, pollen, and macrophytic characteristics reflecting variations in water depth, substrate, turbidity and salinity, usually contain a thick basal sandy storm deposit overlain by thin organic accumulations of peat, gyttja, and snails. The most intense of these disturbance pulses, when correlated with pollen, plant macrofossils, radiocarbon dates, and regional proxy data, provide local evidence of four major floods associated with sustained, catastrophic El Nino events, tsunamis and/or severe storms in the Andean highlands over the last 2000 years.

Engels, S., Helmens, K. F., Valiranta, M., Brooks, S. J. & Birks, H. J. B. 2010: Early Weichselian (MIS 5d and 5c) temperatures and environmental changes in northern Fennoscandia as recorded by chironomids and macroremains at Sokli, northeast Finland. Boreas, Vol. 39, pp. 689–704. 10.1111/j.1502-3885.2010.00163.x. ISSN 0300-9483. A 25-m-long sediment record spanning the time from the Eemian to the Holocene was recovered from Sokli, northeast Finland. This study focuses on a 6-m-long sediment interval that is dated to the Early Weichselian period (MIS 5d and 5c) and consists of lacustrine and fluvial deposits. Using chironomid remains, botanical and zoological macroremains as well as sediment lithology, we were able to reconstruct past changes in the environment, including climate. The results indicate that the site was situated on a flood-plain during the latter stages of MIS 5d (Herning Stadial) and that summer temperatures might have been ∼6 °C lower than at present. Although this value should be treated with caution, as numerical analysis shows that it has a very poor fit-to-temperature, this low reconstructed value concurs with several other reconstructions that are available from western Europe. During MIS 5c (Brorup interstadial), the depositional environment changed into a lake system, initially with stratification of the water and subsequently with complete mixing and a strong influence of streams. Both chironomid-based and macroremain-based temperature inferences indicate past July air temperatures that were significantly higher than at present. This result is in contrast to other (low-resolution) reconstructions from northern Fennoscandia that indicate past temperatures 6–7 °C lower than present using fossil coleopteran assemblages. However, several central European sites indicate that there was a phase during the Brorup interstadial that was characterized by high summer temperatures, and a comparison between the high-resolution reconstructions from western Europe and the results presented in this study suggests that the north–south July air temperature gradient between the mid- and high-latitudes was much weaker during the Brorup interstadial than it is at present. High solar insolation values (particularly the obliquity) during the Brorup interstadial might explain the low summer temperature gradient over the European continent. A return to fluvial conditions occurred in the upper parts of the sediment sequence, and, after a brief interval of gyttja deposition under cooling conditions, the site became glaciated during MIS 5b.

Lakes are prominent features in distal zones of delta plains. Organic-clastic lake fills may form in these lakes, which include gyttja and lacustrine deltas. Understanding of the geometrical properties, the facies distribution, and the origin of organic-clastic lake fills is limited. Knowledge of their development and composition, however, will improve our fundamental understanding of both sediment distribution in and evolution of distal delta plains. Furthermore, organic-clastic lake fills potentially form connectors in hydrocarbon reservoirs. This study aims to describe and explain the characteristics of organic-clastic lake fills and thereby to contribute to the understanding of delta evolution, especially of distal delta plains. A field study conducted in the Schoonhoven and Angstel–Vecht areas, located in the distal part of the Rhine–Meuse delta, the Netherlands, indicates that organic-clastic lake fills developed in peat-bounded lakes after an avulsion initiated fluvial sedimentation. The characteristics of organic-clastic lake fills, such as geometry, sedimentary facies, and sedimentation rates, were both qualitatively and quantitatively determined by cross sections, geomorphogenetic maps, and logs. The results show that in the Angstel–Vecht area as much as 30% of the fluvial-sand volume is stored in organic-clastic lake fills. This contrasts to the general notion that overbank deposits do not contain significant portions of sand. Further, the lacustrine setting often results in vertically bounded sediment bodies that include gyttja and underlies clastic depositional facies, which show a prominent coarsening-upward succession. It is concluded that the presence of organic-clastic lake fills enlarges the reservoir capacity of ancient fluvio-deltaic successions as they contribute to the reservoir volume and also can form connectors between isolated channel-belt sand bodies.

Organic–clastic lake fills, which include lacustrine deltas, are prominent architectural elements in the distal zone of delta plains. We hypothesize that lakes and fossil lake fills affect the development of a fluvial distributary channel. To test this hypothesis, a Holocene palaeogeographic reconstruction is presented of the Angstel–Vecht area, The Netherlands based on a geomorphogenetic map, lithogenetic cross sections, microfossil analyses, and various dating methods (i.e. 14 C-dating, OSL dating, pollen analyses and archaeological evidence). We found that peat accumulation on the Pleistocene substratum started ~ 8000 cal yr BP in response to base-level driven groundwater-level rise. Peat-bounded lakes existed in which gyttja was formed. Fluvial sedimentation in the study area commenced when a new Rhine distributary – the Angstel–Vecht – formed ~ 2970 cal yr BP. As a result, the lakes were filled with fluvially supplied clastic material. Fluvial activity diminished after ~ 2300 cal yr BP although the system continued to function as a high-discharge spillway for Rhine distributaries. This study illustrates the influence of lakes and lake fills on fluvial architecture and sedimentology. Downstream of a lake, levee deposits are thin compared to upstream reaches and the channel-belt sediment is clayey. Furthermore, channels maintain a meandering pattern when organic–clastic lake fills form the substrate because of the relative low bank stability. This is in contrast to straight channels in the distal delta plains that are influenced by erosion-resistant peat substrate.

A comprehensive study (chronological, lithological and geochemical) of an 8.5 m postglacial sediment sequence from Lake Peipsi was conducted to elucidate the effects of lake-level changes on the sedimentary environment and biogeochemical dynamics in a large lake. Four lithological units were distinguished in the sediment sequence studied: clayey silt, slightly laminated greyish carbonaceous gyttja, brownish-grey gyttja and dark gyttja. These units indicate that large shifts in sedimentation processes occurred in the past. The sediment data show that fluctuations in water depth had a profound impact on the lake environment, recorded as changes in the lithological composition, phosphorus content of sediments and composition of diatom assemblages. The corresponding changes are best reflected in sediments accumulated during phases of regression when the lake area was also smaller. As the water depth and area of the lake increased, wave-induced erosion and resedimentation smoothed or even disturbed the initial information. The increase of phosphorus content in the unconsolidated, high-porosity surface sediments (0.5 m) is most probably connected with active diffusion and matter exchange between the water-sediment pools.

Increased concentrations of several trace elements have been observed in water draining areas with sulphidic sediments along the Baltic Sea coast of Sweden and Finland. Some of these elements are harmful to the water environment. The increased leaching of trace elements is often caused by antrophogenic activities, such as ditching, which cause oxidation of the sulphides and thereby acid soil conditions. It is therefore important to recognise areas with sulphidic sediments and, if possible, avoid land use, which causes sulphide oxidation. The aim of this study was to find time effective methods, which can be used to delineate areas with sulphidic sediments. Three areas in Sweden with known occurrences of sulphidic sediments were studied. Data obtained from the mapping program at the Geological Survey of Sweden (SGU) were first studied. Selected sites were thereafter visited and geoelectrical measurements were carried out by the use of several instruments. The results imply that areas with sulphidic sediments are reflected as areas with high trace element contents on SGUs biogeochemical maps, which are based on analyses of trace elements in aquatic plants. The same deposits are often shown as gyttja clay on the maps of Quaternary deposits. Furthermore models derived from airborne electromagnetic measurements show that areas with sulphidic sediments often have a lower electric resistivity than surrounding sediments. Also the results from ground geoelectrical measurements suggest that the sulphidic sediments have a lower resistivity than surrounding fine-grained deposits. That interpretation was verified after stratigraphical studies and analyses of the sulphur contents of the sediments. It is therefore suggested that data from ground geophysical measurements can be used for a detailed delineation of sulphidic sediments, whereas data obtained from airborne geophysical and geological maps give an overview over potential areas with these sediments. The absolute resistivity of the sulphidic sediments varies, however, between the three investigated areas. Complementary corings and stratigraphical descriptions are therefore always necessary to verify the occurrence of these sediments.

A 6.5 m long sediment succession (18.5-2.2 ka BP) from the northern sub-basin of lake Endletvatn was analysed lithologically, palynologically and chemically. The chemical analyses were performed at about 10 cm depth intervals for the following parameters: total organic C, N, P, Fe, Mn, Mg, Na, K, Ca and S, in addition to water content, dry density, and pH. Two main lithostratigraphical units can be distinguished, which also differ substantially in chemical characters. Five chemostratigraphical main units were distinguished. The two lowermost units 1–2 (18.5–12.9 ka BP) correspond to the lower lithostratigraphical main unit and are characterized by minerogenous sediments with low C and N, and high Fe, Mg and K. P is low, partly because of a scarcity of P in parent rocks. Chemostratigraphical unit 3 (12.9-9.6 ka BP) is characterized by increasing C and N and a high N/P ratio (10–20) culminating in the early part of the Younger Dryas, indicating abundant N available for bio-production. The Fe, Mg, and K content is still high, but decreasing, indicating decreasing glacial and kryogenic erosion and allogenic deposition until c. 10.5 ka BP. A hiatus represented by a sand layer covers most of the time-span 10.5–9.6 ka BP. Chemostratigraphical unit 4 (9.6-5.3 ka BP) represents the Holocene thermal optimum in three subunits. In the time interval 9.6–9.1 ka BP, Fe, Mg and K decrease to a minimum and P shows a pronounced increase. The megathermal period c. 8200-5300 BP, is characterized by maxima of C, N and P and a minimum of Fe. The katathermal period after 5.3 ka BP is characterized primarily by increased Fe precipitation, increasing Fe/Mn ratio, and P, C and N at a constantly lower level than during the megathermal. A stable C/N ratio of about 10, of the sediment interval younger than 12.9 ka BP characterizes the sediments as transitional between gyttja and dy. The Holocene lake type varied between weakly oligohumic and mesohumic. Stagnant bottom waters (reducing conditions) occur in the periods 12.9–11.5 ka BP and c. 7.5-5.3 ka BP. The climatic development and other environmental implications of the joint chrono-, chemo-, litho-and biostratigraphical data set are discussed.

We developed a new method for reconstructing millennia-long hurricane records from coastal environments that uses Organic Geochemical Proxies (OGPs) of organic carbon and nitrogen concentrations and their δ13C and δ15N compositions. The new method is independent of presence/absence of sand layers and improves significantly the severe-storm history resolution. The subject of this investigation is a 1.5 m long sediment core raised at 2.8 m water depth from the center of Lake Shelby, Alabama, a freshwater lake located approximately 250 m from the Gulf of Mexico, from which an overwash sand-layer based record was previously derived. The core contains two distinct sediment units; an upper 62 cm thick, fine-grained, organic-rich lacustrine sapropel (gyttja) that shows no visible structures except one sand lamina at 23.7 cm depth, and an underlying 90 cm thick, organic-poor lagoon/estuary clay unit. The sapropel unit was deposited over a 682 ± 30 cal year time interval (1320–2002 A.D.) with a mean sedimentation rate of 0.79 ± 0.04 mm/year. Lake Shelby’s water column exhibits two contrasting states based on water chemistry surveys (i) an “isolated”, stratified, mode under calm weather conditions with a relatively low trophic state, and (ii) a “flooded” mode occurring during storm surges when nutrient-rich seawater floods the lake. Statistically significant δ13C and δ15N positive excursions in organic matter, up to maximum values of −25 (‰ PDB) and 4 (‰ Air N2), respectively, are interpreted as geochemical responses to the marine intrusions that fertilize the lake, increase light availability, and cause eutrophication spikes. Detailed OGPs analyses crossing a sand layer that offers visual evidence of a catastrophic hurricane overwash event at 1717 A.D. exhibit large δ13C and δ15N positive shifts bounded by rapid returns to base values, thus confirming the validity of the hurricane identification by the OGPs model. Our data indicate that 11 catastrophic hurricanes hit the Alabama coast over the past 682 years with a rough recurrence interval of one in 62 years.

Phosphorus content in sediment, water and tissues of three macrophyte species growing in Myall Lake, Australia were studied from January to November, 2004. The sites investigated were North–West (NW), North–East (NE), South–West (SW) bays and Central deep area of the lake (CL). The objective of this study was to investigate how total phosphorus (TP) in plant tissues relate to phosphorus pools and the role played by the aquatic macrophyte species under investigation in phosphorus recycling in the lake. Of the four investigated sites of the lake, TP in plant tissues were significantly higher in North–West and South–West bays compared to the rest. Najas marina had significantly higher TP content (e.g., 1.55 and 1.44 mg/g dw.; P

The article presents the results of lithological and geochemical investigations of recent sediments of Lake Pusty Staw. The analysed sediments document about 300 years of the history of this lake. Historical materials indicate that significant changes in the catchment of the lake took place from the beginning of the 18th century (deforestation and afforestation) followed by 19th century tourist development, and 20th century industrialisation. The sediments were dated using the 210Pb and 137Cs method and core lithology. These made it possible to establish a reliable chronology to the year 1730. The calculated sedimentation rates ranged between 0.17 and 0.83 cm year−1. There was a period of intensified erosion caused by land clearance between 1734 and 1810, which resulted in an acceleration in sedimentation rate (0.36 cm year−1) and a change of lithological type of sediment from detritus gyttja to clayey gyttja. On the basis of Cu, Zn, Cd and Pb content in the sediments, it was determined that the beginning of pollution of the lake dates back to the 19th century and was caused probably by the existence of a health resort. A systematic increase in pollution occurred in the 20th century as a result of industrial plants. Normalised with respect to Al, the content of heavy metals in polluted sediments was from several to twenty times higher than in sediments of the preindustrial period, and a comparison of historical materials with changes of sediments in most cases made it possible to identify the direct causes of the increase in pollution.

Lake Vaha-Pitkusta is a 35-m deep meromictic kettle-hole lake in SW Finland. The topmost 15cm of the sediment stratigraphy consists of black gyttja, representing the last ca. 600years. A sediment core from the deepest point was examined with multi-proxy methods to determine the origin and evolution of the basin, the onset of the meromictic conditions and the primary factors that initiated the meromictic processes. The results indicate that Lake Vaha-Pitkusta became isolated from the Baltic basin during the Yoldia Sea stage. After initial unstable sedimentary conditions the development continued steadily until ca. 2500–2300 cal.BP when there is indication of lake level rise and/or increased surface runoff, probably resulting from a cooler and moister climate. The diatom and cladoceran results indicate only a slight rise in the trophic state following the increased erosion. Pollen evidence suggests weak anthropogenic activity in the catchment during the last 1000 years, and this had only little effect on the trophic state, which remained rather low. Thus, it is most unlikely that the trophic state was the primary reason for the origin of meromixis, although it may have contributed to it. We tentatively suggest that the primary reason was the peculiar morphometric dimensions of Lake Vaha-Pitkusta (small, deep, sheltered from winds) which made it very sensitive and that even a very slight increase in soluble electrolytes may push it over the edge into meromixation. It is possible that this did not occur during the cold/moist period around ca. 2300 cal.BP but during the Medieval Climate Anomaly. Studies on sediment geochemistry are needed to verify this assumption.

In Lake Bergsee, southern Germany, the upper 13 m of gyttja and detritus mud were deposited during the latest Pleistocene and Holocene. These have been investigated for physical properties using mainly geotechnical methods and X-ray computed tomography. These deposits are extremely weak even compared with similar deposits in Scandinavia and elsewhere. It has been possible to recognise a significant change in the density and in the undisturbed undrained shear strength at a depth of 6.5 m, which can be related to a change in the sediment type. Other variations in properties can be related to organic fibre length and mineral growth. Although compressibility has not been measured directly, the deposits have the properties of a highly compressible sediment and estimates of effective stress and compression have been made. The sediment column seems to have experienced very little shortening, apparently because the microstructure of the organic sediments would hinder the movement of water under the expected sediment loads.

Stump Lake is strategically located to provide a sediment record of very large debris flows that travel down Cheekye River to lower Cheekye fan from the west flank of Mount Garibaldi, a Quaternary volcano in the southern Coast Mountains of British Columbia. Cores collected from Stump Lake span the last 11,500 years and consist largely of gyttja. However, a diamicton layer and an associated detrital organic layer, which is capped by a clay lamina, record a large debris flow derived from the headwaters of Cheekye basin. Radiocarbon ages indicate that this event occurred about 6,900 years ago. We estimated the peak discharge of the flow by measuring cross-sections of the Cheekye River channel adjacent to Stump Lake and by calculating flow velocity using a Newtonian flow model. Reasonable values of peak discharge, calculated in this way, were input into an empirical equation linking discharge and debris-flow volume, developed for non-granitic debris flows. The estimated minimum volume of the debris flow is 3 to 5 × 106 m3. Another large debris flow (ca. 3 × 106 m3), which occurred about 800 years ago, is not recorded in Stump Lake sediments and thus was too small to reach the lake. The Stump Lake sediment sequence indicates that no debris flows larger than several million cubic meters have reached lower Cheekye fan in post-glacial time.

A sub-bottom acoustic survey of Devil Lake on the Canadian Shield in southern Ontario reveals three acoustic facies: (I) a moderately acoustically transparent, laminated sequence interpreted as a glacilacustrine deposit in glacial Lake Iroquois or a subsequent phase in water depths up to 200 m greater than at present, (II) a transitional more transparent, less layered facies interpreted as being deposited in a more distal glacial lake from erosion of sediment in the watershed exposed by the failure of the ice dam and lowering of the glacial lake before stabilization by the development of forests, and (III) an acoustically transparent facies with similar transmissivity to the water column, interpreted as Holocene gyttja. Each is spatially variable in extent and thickness in response to those processes. There is only a very weak relation between sediment thickness and the water depth in which it was deposited. Wave processes prevent deposition in water depths less than about 6 m and evidence of erosion to the greatest depths of the lake (>40 m) is pervasive. The data demonstrate the value of acoustic survey in assessing lacustrine processes and the history of lakes, and the significance of such documentation in planning a coring program and in interpreting the results.

Four sediment cores and twenty-five 14C ages from Ritterbush Pond in northern Vermont provide a detailed and continuous temporal record of Holocene lake and watershed dynamics. Using visual logs, carbon content, magnetic susceptibility, stable isotope signatures, and X-radiography, all measured at 1-cm scale, we identify and date discrete layers of terrestrially-derived sediment in the organic-rich, lacustrine gyttja. These inorganic layers range in thickness from 10 cm and range in grain size and sorting from homogeneous silt to graded sand. AMS radiocarbon ages both from macrofossils within the thickest layers, and gyttja bracketing these layers, provide the basis for correlation among the cores, the dating of 52 basin-wide sedimentation events, and the development of a detailed sedimentation chronology for the Holocene.

A 137 cm sediment core from Fog Lake, a small upland basin that was not glaciated during the Late Wisconsinan, reveals the following stratigraphic succession: (I) basal diamicton, (II) laminated silts, (III) compacted dewatered gyttja, (IV) stratified minerogenic sediments, and (V) overlying gyttja. Units I—III, and most of unit IV, were deposited prior to the Holocene; unit V represents approximately the last 8000 14C years. Alternate luminescence dating techniques (TL and IRSL) place unit III in latter oxygen isotope stage (OIS) 5, ’74,000 years BP. A suite of 20 AMS 14C dates suggests that much of the post-OIS 5 paleoenvironmental record is characterized by either extremely low continuous sediment accumulation, or by one or more episodes of more rapid sedimentation. Diverse pollen and spore assemblages have concentrations that are unexpectedly high throughout the pre-Holocene sediments (’10,000 grains cm~3), by comparison to the Holocene (&5000 grains cm~3). Exceedingly low sediment accumulation rates appear to have resulted in the concentration of atmospherically derived pollen and spores. Diatom assemblages record the evolution of the lake’s chemistry and past algal production. Several abrupt changes occurred synchronously in both the terrestrial and aquatic components of the system, and these appear to represent ecological responses to pre-Holocene climatic variability. The sediments of Fog Lake provide the first integrated paleoecological record older than Holocene for a vast region of the Canadian Arctic, thereby refining our understanding of long-term arctic ecosystem ontogeny. ( 2000 Elsevier Science Ltd. All rights reserved.

Sediment stratigraphy and palaeobotanical data from five cores were used to reconstruct the postglacial water-level changes of a small lake in southern Québec. The cores were taken along two transects from the centre of the lake to the margins. Lake level was relatively high before 11 000 cal. BP, when sedimen tation was characterized by the deposition of silty gyttja (.13 000 cal. BP) and marl (13 000–11 000 cal. BP). From 11 000 to 7000 cal. BP, a sediment hiatus was indicated by the lack of two regional pollen zones between the marl and the overlying gyttja, suggesting either nondeposition or erosion of the previously deposited sedi ments due to a low lake level. The lake level was approximately 2 m lower than present on the basis of macrofossil assemblages. A rise in the water level of about 1 m occurred around 7000 cal. BP, which was interrupted by a second lowering between 6100 and 4400 cal. BP, as indicated by a hiatus in the pollen stratigra phy. During this low period, the water level was at least 2 m lower than present. The last 4400 years are characterized by a continuous rise. The lake-level fluctuations are broadly synchronous with other palaeo hydrological records in northeastern United States, Ontario, and Subarctic Québec, implying broad-scale climatic control.

Two sediment cores, ca. 6 m long, have been recovered from the north basin of Loch Ness, Scotland. Each consists of ca. 4.5 m of laminated gyttja, terminating in a basal grey, unlaminated clay. A suite of three 14C AMS dates have been obtained, and place the base of the gyttja at ca. 9500 yr B.P. Investigations into the structure, composition and formation of the laminae are in progress. Analysis by Backscatter Scanning Electron Microscopy (BSEM) has demonstrated that they consist of couplets comprising dark, clay-rich sediments thought to be deposited from spring to autumn, and pale, silt-rich layers believed to represent sedimentation through winter. The laminae are thus thought to record incidence and intensity of streamflow into the Loch over the past nine millennia, and thus illustrate environmental change over the region for most of the Holocene. X-ray densitometry has been utilised in order to count the laminations and test the hypothesis that they are varves. It has, however, proved difficult to obtain a continuous sequence of countable laminations, although it has been possible to construct a fragmented, floating chronology which indicates that the hypothesis may be correct. Examination of lamination thickness reveals that although the average rate of sedimentation throughout the time periods studied seems to have remained fairly constant, significant variations have occurred. As Loch Ness is located on the northwest oceanic fringe of Europe, any climatic signal which the laminations contain will be closely related to even larger scale events over and within the North Atlantic Ocean, which is a major controller of global climate. Preliminary statistical investigation of sequences of laminae is being carried out in order to search for periodicity of sedimentation which may then be related to appropriate climatic indices.

The accumulation of heavy metals and trace elements has been investigated in a well laminated sequence of Holocene and late Pleistocene lake sediments composed of diatomaceous gyttja, tuff and silt and clay sediments. Varve chronology of the annually deposited gyttja yielded a continuous high-resolution time sequence and allowed the absolute age dating of the sediment. Fluxes of elements remained largely uniform from the late Pleistocene into the Holocene. Higher trace element and heavy metal fluxes occur from 2322 to 862 VT years ago (VT: varve time, years before 1950) and reached their maxima in the uppermost sediments (

Methanogenesis was measured during the summer of 1994, in sediment coresand bulk samples from a Phragmites australis wetland in northern Jutland,Denmark. We compared sediment from healthy reed and dying-back reed, andan open lagoon resulting from die-back. Cores revealed variability withdepth and between sites, with the highest rates coinciding with layers oforganic gyttja, and negligible methane production from the underlying sandbase. Methanogenesis rates in the lagoon and die back sites were higher(up to 100–150 nmol h-1 g-1dry wt. sediment) than in the healthy reed (50–80 nmolh-1 g-1), with the highest rates being recordedfrom May to July. At these times, methanogenesis was markedly temperature-limited; samples incubated at 30 °C anon-limiting temperature, gave rates as high as 200–400nmol h-1 g-1 for the lagoon and die-backareas and 150 nmol h-1 g-1 for the healthyarea. Addition of 8 mM acetate and H2/CO2headspace suggested that both acetate-fermenting andCO2-reducing bacteria were present. Acetate additions suggested some co-limitation by substrate availability, with acetate limitation occurring in the healthy site during July and in the die-back site during August. Lower rates during August, especially in the healthy area, were associated with low water levels which resulted in more oxidized sediments. The data reveal highly variable methanogenesis in the sediment which, when considered with sediment depths, indicates that sites of Phragmites die-back have significantly greater rates of anaerobic mineralization than surrounding healthy wetland, and may be intense sources of methane.

Profiles of percent carbon and nitrogen, carbon/nitrogen (C/N) ratios and stable carbon (δ13C), and nitrogen (δ15N) isotopic ratios in organic matter from an 11.6 m core were used to reconstruct environments of deposition in the Swan Lake basin during the past 5300 YBP. The upper 6.5 m consisted of gyttja containing variable amounts of reddish brown-colored fine organic matter and calcium carbonate. It was followed by a 0.5 m sandy silt, which was followed by a 3.6 m reduced layer characterized by large quantities of black organic plant remains, sapropel, and then by another sapropel layer consisting mainly of well-sorted sapropelic sand with relatively low organic matter content. The C- and N-contents in the organic matter in the sediment profile ranged from 0.5 to 23% and from 0.02 to 2%, respectively. Carbon content were positively correlated to both N and clay content while carbon content was negatively correlated to sand content. Two major environmental phases in Swan Lake were apparent from large differences in the C and N data of the sediment organic matter. These include the sapropel (marsh) stage that stretched from approximately 5330 to 3930 YBP, and the following gyttja (open water stage). During the sapropel marsh plants identified in a previous pollen study as cattails and sedges proliferated and produced copious amounts of well-preserved organic matter. C/N ratios, δ13C values, and δ15N values in the sapropel were significantly different from those that characterized organic matter in the gyttja. During the gyttja δ13C values indicated that deep primary producers have dominated lake biomass. By utilizing bicarbonate as their C-source, the accumulating biomass became relatively enriched δ13C values. The presence of high sediment CaCO3 contents indicated more alkaline and deeper water conditions prevailed during the gyttja. Further refinement of the data suggested that each major phase initially contained an identifiable transition stage. During the sapropelic (initial marsh stage) which occurred before 5330 YBP, sand content gradually decreased as organic matter increased. As reflected by high C/N ratios and slightly enriched δ13C values, these sands appear to have contained sufficient permeability to promote partial mineralization of accumulated organic-N containing compounds. A short initial gyttja transition period from about 3930–3830 YBP occurred in which the sediment silt content was anomalously high relative that measured in the surrounding layers. The silt content suggests that this turbid transition layer can not be completely explained by sediment mixing via bioturbation. The silts appeared to have been associated with the sharp climate change that resulted in higher water-table conditions during the gyttja stage.

Sapropel is organic rich freshwater lake sediment with broad range of applications. Firstly it was named as “gyttja” in 1862 when Swedish scientist Hampus von Post called so a light-colored coprogenic deposit consisting of a mixture of plankton particles, mollusk shells, chitin remains from the exoskeletons of insects, pollen and spores of higher plants and mineral particles, formed in eutrophic water bodies. Term "sapropel" means "decayed sludge" it was proposed by Lautenberg in 1901 and by G. Potogne in 1904. Sapropel relates to renewable natural resources and is typically found only in freshwater basins; however, usually this term is used in saline aquifer stratigraphy studies. Sapropel’s chemical composition and peculiarities of different minefields are significantly different and defined by its formation conditions and by lakes’ flora and fauna. Sapropel as it contains organic matter is able to bind metal ions and change their speciation forms in soils forming stable complexes. The ability to form complexes with metal ions depends on the type of soil, type of metal, as well as quantity of sapropel as soil amendment. The main sapropel reserves are found in the lake-bottom sediments reserves in Latvia are estimated as 800-900 million m 3 or 170-190 million tons (with moisture content of 60%). In 1957-1967 more than 250 lakes in Latvia have been studied in detail on sapropel reserves and properties, later from 1990-2000 more than 1300 lakes were studied additionally. There are 56 strongly and more than thousand potentially contaminated sites with heavy metals in Latvia. The aim of this paper is to give overview status description on theoretical possibilities to use sapropel as the agent for remediation of contaminated with heavy metals soil.

This study determined whether artificially mixing gyttja, an organic sediment that contains high levels of NH4, with its overlying waters, affected phytoplankton abundance and species composition in Myall Lake (NSW, Australia). A series of mesocosms was employed, with three mesocosms being designated as controls, i.e. no gyttja mixing, and three others termed impact mesocosms, i.e. in which gyttja was mixed with the overlying waters. Sampling was undertaken during a 5 day period in sediment disturbance, and phytoplankton community variables were recorded at seven intervals, i.e. just prior to disturbance and 30 minutes, 3 hours, 1, 2, 3, 4 and 5 days after gyttja disturbance. Comparisons of these community variables among treatments and over time convincingly demonstrated that overall phytoplankton abundance rose from 20,000 cells/mL just prior to disturbance to between 30,000 cells/mL and 55,000 cells/mL 2 to 4 days after gyttja mixing. This rise in abundance was attributable to a substantial increase in the cyanophycea over the same period. In contrast to the cyanophyceae, the abundance of bacillariophyceae increased sharply following disturbance from 150 to >1000 cell/mL and did not exceed 1000 cell/mL for the duration of the experiment. This supported the hypothesis that gyttja mixing does introduce benthic microalgae into the water column. Sediment disturbance caused differences in species composition in time, with cyanobacteria being mostly influenced taxa. Each period of disturbance between mesocosm have different assemblages of species. Keywords Phytoplankton; Sediment disturbance; Mesocosm; Community structure

An interval of late-glacial to early Holocene sedimentation, spanning the period 12.9–8.4 ka BP (14C dated by accelerator mass spectrometry), is contained within 15 cm of gyttja in a core from a small lake on southwestern Cumberland Peninsula, Baffin Island. This sediment was subsampled in continuous 2.5 mm increments for diatom analysis. Extremely low sediment accumulation rates (~1.8 cm ka−1) are characteristic of the initial phase of organic sedimentation, but they increase rapidly (to 14.2 cm ka−1) after 9 ka BP. The first 0.5 cm of gyttja contained an acidophilous diatom flora resembling that of underlying mineral sediments. Thereafter, and throughout the late glacial and earliest Holocene, diatom floras were dominated by alkaliphilous and circumneutral species of Fragilaria. Around 9 ka BP, shifts to acidophilous floras dominated by Brachysira brebissonii, and, later, Eunotia rhomboidea and Frustulia rhomboides vars. saxonica and crassinervia, suggest a period of natural lake acidification. High diatom production accompanied the lowered lake-water pH, which reflects, respectively, the paleolimnological response to an early Holocene climatic optimum, and progressive depletion of lake alkalinity sources. There is no evidence of diatom or sediment responses attributable to the Younger Dryas oscillation, implying that deglacial reorganizations of the North Atlantic Ocean did not necessarily affect paleoclimatic conditions in the southern Cumberland Sound region.

Dolina Iny w między Suchaniem a Stargardem Szczecińskim została utworzona w czasie wytapiania się lądolodu z fazy pomorskiej zlodowacenia bałtyckiego. Powstała w miejscu rynny glacjalnej, która utworzyła się w miejscu kopalnych dolin rzecznych.Podczas uzupełniających badań geologicznych związanych z projektem nitki gazociągu Świnoujście – Lwówek Wielkopolski wykonano 20 otworów badawczych w odległościach od 50 do 100m w przekroju poprzecznym przez całą dolinę Iny. Głębokość otworów sięgała od 6 m w strefie krawędziowej do głębokości ponad 30 m w części środkowej doliny. Pozwoliło to na wykonanie dokładnego przekroju poprzecznego przez dolinę.W związku z tym, że w środkowej części doliny natrafiono na znaczną miąższość osadów organicznych i zastoiskowych glin pylastych wykonano sondowanie CPTU oraz pobrano próbki osadów organicznych oraz pylastych zalegających poniżej. Dla pobranych osadów wykonano standardowe badania geotechniczne a dodatkowo dla wybranych 2 próbek określono wiek TL.Wyniki badań potwierdzają istnienie zbiornika sedymentacyjnego wypełniającego dolinę w późnym plejstocenie (gliny pylaste), w którym spokojną sedymentację przerywały zmienne warunki sedymentacyjne. W holocenie osadzały się gytie, namuły a w stropie torfy). Zbiornik stanowiący dolinę Iny wypełniany osadami mineralnymi istniał w czasie funkcjonowania „Zastoiska Pyrzyckiego”.

Phosphorus (P) reactivity and bioavailability in lake sediments may be determined by different forms of P and their distribution. Reactive and nonreactive P pools in two shallow subtropical lake sediments (Lake Apopka and Lake Okeechobee) were determined by sequential chemical extraction using 1 M NH4Cl (pH 7.0), 0.1 M NaOH, and 0.5 M HCl, reportedly representing loosely-bound P, Fe- and Al-bound P, and Ca- and Mg-bound P respectively. The sequential P fractionation was tested using pure P compounds and selected P minerals. The scheme effectively separated Fe- and Al-P from Ca-P fractions in an FePO4-AlPO4-Ca3(PO4)2 mixture. Readily available P, defined as the sum of water-soluble P and NH4Cl-extractable P, in the unconsolidated gyttja (UCG) layer (surface 0–30 cm) of Lake Apopka sediments accounted for 10.1 to 23.7% of total P (TP). This sediment P fraction constitutes a large reservoir which may act as a source of P to the overlying water. In subsurface marl layers (134–148 cm depth) of Lake Apopka, NH4Cl-P constituted

Lead in the environment of Lake Wigry (NE Poland)Analysis was performed for lead content in the sediments of Lake Wigry (NE Poland), taking into account lithology, basic chemical component content and physical characteristics of sediment, Several hundred sediment samples from different parts of the lake and peatland around the lake, were collected. Their locations were determined by GPS and the depth of sediment by echosounder. The surface layer (0-10 cm) of sediment and sediment cores were taken to determine the spatial and vertical distribution of Pb. Concentrations of lead in the surface sediment range from 2.52 to 469 mg kg-1. One of the most important factors influencing spatial distribution of Pb is sediment type. The highest content of Pb was found in samples of organic gyttja and the lowest in clastic sediment samples. Strong positive linear correlation (r = 0.7) between organic matter content and Pb concentration in sediment was observed. It may be the result of simple bio-accumulation of lead. A large influence of sediment location on Pb distribution was found. The largest concentration of this element was found in sediment of the Wigry Basin. The major part of Pb accumulates in the surface layer of sediment.

Mazama tephra is a widespread mid-Holocene stratigraphic marker, dating to ca. 6845 BP, and is considered useful for the correlation of Holocene events in western North America. We present evidence from Copper Lake, Alberta, for a tephra layer that underlies Mazama tephra and appears to be a discrete tephra layer but that is indistinguishable from the conventional Mazama tephra by microprobe analysis of glass shards. Three alternative hypotheses are considered to explain this tephra underlying Mazama: in situ position of an earlier Mazama-like tephra, recycling of tephras, and settling of tephra slabs through the gyttja. The size distributions of birch pollen grains indicate that the Mazama-like tephra is in primary stratigraphic position in the early Holocene gyttja, and that sediment recycling has not destroyed the integrity of Copper Lake sediment stratigraphy. It is concluded that most probably a Mazama-like tephra was deposited between 9700 and 10 500 BP. If this in situ hypothesis is correct, the identification of a tephra as Mazama by major-element chemistry does not necessarily fix the age of the enclosing strata. Evidence to confirm the existence and plot the distribution of a Late Pleistocene – early Holocene, Mazama-like tephra is needed from other sites in northwestern America. A collateral result of this study is that ablation of valley-bottom ice in the vicinity of Castle Mountain took place prior to 10 500 BP.