Lake Sediments

Dal lake is known as jewel of Kashmir valley and it work as a pull factor for lakhs of tourists every year. However Dal lake has lost its beauty what it had until 1980’s. Several reasons are responsible for miserable condition of Dal lake. Data were collected by multi-methods approach both primary and secondary resources were involved. Locals and students were interviewed in Srinagar city and several news portals, journals was also observed.  The findings of the research indicate that most of politicians had made misuse and made lot of money on the name of development of Dal lake. This case study will provide useful findings for policymakers to improve the existing condition policies for lake.

In 2012 and 2013 extensive sedimentological field work was conducted to study the depositional setting, the regional geology and facies relationships, and measure sections of the Green River Formation in all the subbasins, in Wyoming, Colorado and Utah (USA). Several pervasive horizons of seismically induced deformation structures were identified mainly in profundal lacustrine sediments. Deformation is represented by brittle and plastic behaviour, as well as sediment injection and mass transport. The deformed layers are confined by undeformed beds which implies sporadic short-lived events that affected only near-surface sediments with susceptible rheological state at the time.
Based on: (1) the tectonic setting of the lacustrine basins; (2) the sedimentary environment and sedimentological characteristics of the successions in which the deformed layers occur; (3) their lateral extent and proximity to known active fault systems during the time of the deposition of host sediments; (4) their recurrence at different stratigraphic levels, intervals showing large-scale sedimentary deformation structures are interpreted as result of in-situ loss of shear strength, formed by increased pore pressure and vertical or horizontal stress induced by seismic activity

Phosphate fertilizers manufactured from rock phosphate play a major role in modern agriculture. This geochemical investigation to determine the fertilizing capacity of lake sediments was conducted in upstream and downstream lakes (Koon-wewa and Ihalahalmilla-wewa in upstream and Kiralogama-wewa in downstream) with respect to the Eppawala Phosphate Deposit (EPD), Sri Lanka. In this regard, total 20 and 21 surface sediment samples were collected from upstream and downstream lakes, respectively. Samples were analyzed for major oxides such as P2O5, CaO and K2O to assess the possibility of using lake sediments as a source of nutrients, particularly phosphorus. Average concentrations of P2O5, CaO, K2O, Cd and As in downstream lake were 0.80%, 0.62%, 0.25%, 76.2 ppb and 28.8 ppb, respectively, compared to 0.45%, 0.36%, 0.12%, 396.8 ppb and 845.2 ppb in upstream lakes. Trace elements such as Cd and As are contained in rock phosphate which are environmentally hazardous elements. These elements can be concentrated in sediments due to the excessive and continuous usage of fertilizers. Based on correlation analyses, P2O5 shows significantly and moderately positive correlations with Ca and K2O, respectively in downstream sediments. From available P2O5, 28.88% from total P2O5 in upstream lake sediments and 43.75% from total P2O5 in downstream lake sediments were soluble in 2% citric acid. Phosphates in sediments, especially in downstream, are more soluble than in Eppawala Rock Phosphate. Therefore, nutrients in downstream lake is high and they are in more soluble form which show the influence of EPD for the geochemistry of the downstream lake due to the interaction between the deposit and Jaya-Ganga. The results also suggest that the lake sediments in downstream has higher fertilizing capacity which can possibly use as a low grade phosphate fertilizer for direct applications in low intensity farming.

The Eocene Green River Formation and associated fluvial strata host a large variety of widely distributed and laterally extensive synsedimentary to early post-depositional deformation features. Although mostly overlooked in past studies, these structures provide insight into the rheology of the sediments and hydrodynamic conditions at the time of deformation. They also have implications about basin configuration and bottom topography, as well as the structural history of the region.
In the Uinta and Piceance Creek Basins of Utah and Colorado, deformed intervals are present in littoral (sand-dominated) to profundal (oil shale) lacustrine deposits, as well as fluvial facies. Deformation structures exhibit a wide range of morphology, size, and style, ranging from ductile (convolution, folding, load and pinch-and-swell structures) to brittle (microfaults, breccias), to sedimentary injection into fissures and cracks forming dikes, to various mass transport deposits. In most cases, these layers are bound above and below by undisturbed beds of similar facies with horizontal bedding planes, which implies short-lived but recurring events that affected only sediments with a susceptible rheological state. Deformation typically occurred intrastratally, i.e. under shallow burial. The variations in deformation style, size, morphology, and areal extent are related to differences in grain size and type, water content, cementation, organic content, thickness of susceptible material, lateral facies variation, and the nature of the driving force. Some of the sedimentary injection features overprint each other, indicating multiple events affecting a single interval.
We interpret most of these features as seismically induced (‘seismites’) based on: (1) the tectonic setting of the basin; (2) the sedimentary environment and sedimentological characteristics of the host succession; (3) the lateral extent of deformation structures; (4) their recurrence at different stratigraphic levels; and (5) their similarity to those ascribed to seismically induced deformation elsewhere and reproduced experimentally. They developed as a result of increased pore pressure and a complex combination of extensional, compressive, and shear stresses acting in many directions caused by shaking during strong earthquakes. Mass transport deposits indicate in situ disruption and failure of the imperceptibly dipping lake floor. These ‘seismites’ represent the direct sedimentary record of syndepositional tectonic activity in the Uinta Basin.

The siliciclastic lacustrine rocks of the~1000 Ma Diabaig Formation, northwest Scotland, contain a remarkable diversity of macroscopic structures on bedding planes that can be compared with various kinds of microbially induced sedimentary structures (MISS). Field sedimentological investigations, combined with laboratory analysis of bedding planes and petrographic study of thin sections have allowed us to characterise a range of depositional environments and document the spectrum of biological structures. MISS are reported from frequently subaerial environments, through commonly submerged facies, and down to permanently sub-wavebase settings. Palaeoenvironmental conditions (water depth, exposure, hydrodynamic energy) control the distribution of MISS within these facies. This demonstrates that mat-forming microbial communities were arguably well adapted to low light levels or periodic exposure. Some MISS from the Diabaig Formation are typical of Precambrian microbial mats, including reticulate fabrics and 'old elephant skin' textures. In addition to these, a number of new and unusual fabrics of putative microbial origin are described, including linear arrays of ridges and grooves (cf. 'Arumberia') and discoidal structures that are comparable with younger Ediacaran fossils such as Beltanelliformis. These observations indicate that benthic microbial ecosystems were thriving in freshwater lake systems~1000 Ma, and indicate how microbially induced sedimentary structures may be applied as facies indicators for Proterozoic lacustrine environments. The discovery of structures closely resembling Ediacaran fossils (cf. Beltanelliformis) also serves to highlight the difficulty of interpreting simple discoidal bedding plane structures as metazoan fossils.

16.1 Introduction                                                                                                                271
16.2 Changes in the watershed and their long-term impacts on Lake Kinneret  273
16.3 Long-term lake salinity changes                                                                            276
16.4 Long-term lake stratification changes                                                                    276
16.5 Long-term changes to phytoplankton                                                                    277
16.6 The invasion of nitrogen-fixing cyanobacteria (Nostocales)                              280
16.7 Winter populations of toxic Microcystis                                                                  281
16.8 Long-term variation of chlorophyll and primary production                                282
16.9 Long-term sedimentation flux changes                                                                283
16.10 Gaseous methane emission                                                                                285
16.11 Long-term changes in fish populations and the fishery                                    286
16.12 Conclusions                                                                                                              289
16.13 Acknowledgements                                                                                                  290
References                                                                                                                            290
Lake Kinneret (Sea of Galilee) is a warm lake located at ~ 210 m below sea level in the northern part of the Afro-Syrian Rift Valley. The major water inflow to the lake is the Jordan River, which drains the relatively high-rainfall watershed area (2730 km2) of the Upper Galilee and the Golan Heights. At its maximal water level the lake holds 4,200 MCM and its surface area is 167 km2. The main outflow from the lake is via the Israel's National Water Carrier, supplying between 100 and 400 MCM annually, which is ~30% of the Israel water demand. The water level of the lake strongly depends on natural inflows and artificial withdrawal for water supply. The lake is thermally stratified during April - December, with surface temperatures approaching 30°C. The anoxic conditions in the hypolimnion develop in May. Lake Kinneret is meso-eutrophic with a mean annual primary production of ~600 g C m-2.
Long-term monitoring (~40 years) of Lake Kinneret ecosystem revealed multiannual changes in many physical, geochemical, and biological parameters. During the past decades fluctuations in water level increased significantly along with general decline in the average water level. Gradual increase in surface water temperature and a reduction of metalimnion thickness were observed. Water level fluctuations strongly influenced sedimentological processes and concentrations of nutrients in the hypolimnion. Decline of water level forced ebullition of gaseous methane and its delivery to the atmosphere. Destabilization of phytoplankton community was observed since mid 90’s and resulted in blooms of the filamentous nitrogen-fixing blue-green algae and general deterioration of the water quality. The increased fluctuations in water level also strongly influence the productivity of fish populations, fish-zooplankton relationships, and the yields of many commercially important fishes. These changes are attributed to (a) various human activities and management measures in the lake and its watershed area; (b) local and regional hydrological fluctuations; and (c) global climatic changes. In this paper we summarize these major changes and discuss the role of each of the above causes. In the future, global warming, change in precipitations, and extensive use of fresh water in the arid and semiarid zones should impose excessive stresses on freshwater ecosystems, affect their dynamics, stability, and water quality.
Key words: climate change, global warming, anthropogenic impact, eutrophication, water level fluctuation, extreme floods, watershed, upstream wetlands, precipitation, physical regime, stratification, chemical regime, salinity, sedimentological regime, trophic relationships, littoral communities, sedimentation, methane emission, phytoplankton, cyanobacteria, algae, chlorophyll, primary production, Microcystis, Nostocales, fish, fishery.

The ∼1000 Ma Torridon Group of northwest Scotland are here shown to contain a rich diversity of organic walled microfossils preserved in exceptional detail within sedimentary phosphate. The phosphatic nodules and bands in which they occur are autochthonous, as are the organic fossils they contain. The associated sedimentology of this phosphate is shown to be consistent with a lacustrine setting. Informal taxonomic treatment of the microfossils allows statistical assessment of the relative abundances of different morphotypes across a range of lacustrine environments. Exceptional preservation of pristine organic-walled eukaryotes and prokaryotes, together with a taphonomic spectrum in both physicochemical and biological degradational conditions allows a picture to be built of the earliest lacustrine ecological communities.

Thick lake sediments discovered in the southern part of the Czech Republic provide a high-resolution archive for detailed study of paleoenvironmental changes during the Late Pleistocene to Holocene in eastern-central Europe. Until recently, no similar records were available for this important region in the transition from oceanic to continental macro-climatic settings. Using a multi-proxy approach that combines sedimentological, pollenanalytical, paleozoological (Chironomids), geochemical and mineral-magnetic methods we demonstrate that major climatic events of the Late Glacial can be correlated with Atlantic rather than continental regimes as reported in paleoclimatic literature for the area of the interest. The sensitivity of applied biological and abiological techniques to climatically-driven processes allows trans-regional comparisons and enables us to discuss the pattern of geographic variation in these processes. We are able to establish a clear relationship between vegetation cover, soil development and erosional processes. A short-term intra-Alleröd cool event has been correlated with the Gerzensee oscillation. Proxy evidence suggests that the early half of the Younger Dryas was rather humid, whereas the latter half was dry and had significant impact on vegetation, sedimentary dynamics and lake level status during the YD/Preboreal transition.

Outcrops and cores from the top of the lacustrine Tipton Member and the base of the Wilkins Peak Member (~51.5 Ma) of the Eocene Green River Formation, Bridger Basin in southwestern Wyoming yield a wide variety of sedimentary deformation features many of which are laterally extensive for more than 50 km. They include various types of folds, load structures, pinch-and-swell structures, microfaults, breccias and sedimentary dikes. In most cases deformation is represented by hybrid brittle–ductile structures exhibiting lateral variation in deformation style. These occur in low-energy, profundal organic-rich carbonate mudstones (oil shales), trona beds, tuffs, and profundal to sublittoral silty carbonate deposited in paleolake Gosiute. The deformation is not specific to the depositional environment because sedimentary units stratigraphically higher with similar facies show no deformation.
The studied interval lacks any evidence for possible trigger mechanisms intrinsic to the depositional environment , such as strong wave action, rapid sediment loading, evaporite dissolution and collapse, or desiccation, so 'endogenic' causes are ruled out. Thus, the deformation features are interpreted as seismites, and change in deformation style and inferred increase in intensity towards the south suggest that the earthquakes were sourced from the nearby Uinta Fault System. The 22 levels exhibiting seismites recognized in cores indicate earthquakes with minimum magnitudes between 6 and 7, minimum epicentral intensity (MCS) of ~9, and varying recurrence intervals in the seismic history of the Uinta Fault System, with a mean apparent recurrence period of ~8.1 k.y. using average sedimentation rates and dated tuffs; in detail, however, there are two noticeably active periods followed by relative quiescence. The stratigraphic position of these deformed intervals also marks the transition between two distinct stages in lake evolution, from the balanced-filled Tipton Member to the overlying, underfilled Wilkins Peak Member. Thus, these seismites are evidence for regional-scale changes in lacustrine sedimentation of Eocene Lake Gosiute in response to syndepositional tectonic activity. Analysis of synsedimentary deformation features is, therefore, a promising yet under-utilized tool to trace the tectonic evolution of lacustrine deposits of the Green River Formation and other tectonically active marine and non-marine basins.

There is a lack of high-resolution records of hydroclimate variability in the Eastern Mediterranean from the late glacial and early Holocene. More knowledge of the speed of climate shifts and the degree to which they were synchronous with changes in the North Atlantic or elsewhere is required to understand better the controls on Eastern Mediterranean climate. Using endogenic carbonate from a sediment sequence from Nar Gölü, a maar lake in central Turkey, dated by varve counting and uranium-thorium methods, we present high-resolution (∼25 years) oxygen (δ18O) and carbon isotope records, supported by carbonate mineralogy data, spanning the late glacial and Holocene. δ18Ocarbonate at Nar Gölü has been shown previously to be a strong proxy for regional water balance. After a dry period (i.e. evaporation far exceeding precipitation) in the Younger Dryas, the data show a transition into the relatively wetter early Holocene. In the early Holocene there are two drier periods that appear to ...

Summary. Lake Luokesas in Lithuania has become the centre of attention in northern European wetland archaeological research after the discovery of two Late Bronze Age/Early Iron Age pile dwellings. Their unique location, chronology and building techniques have the potential to revolutionise our understanding of important aspects of wetland communities in later prehistoric Europe.

Across the Arctic, postglacial lakes contribute a substantial amount of the total atmospheric methane (CH4), and their emissions are predicted to increase. However, there is still much uncertainty as to the contribution of northern water bodies to atmospheric CH4 emissions. This is mainly due to the spatiotemporal variability of the predominant pathway of emission from high latitude lakes: ebullition (bubbling). There are a myriad of factors that affect ebullition fluxes, including solar radiation input and atmospheric pressure, which make it difficult to model the impact on regional emissions. Very few studies have correlated sediment characteristics and submerged vegetation density with ebullition, to see what drives the variation across space and time. This study investigated the effect of submerged aquatic macrophyte (SAM) species distribution and abundance on CH4 dynamics in three postglacial lakes in Stordalen Mire, near Abisko, Sweden (68°21'N, 18°49'E). Submerged vegetation density maps developed from vegetation transects and sediment geochemistry derived from sediment cores were compared to ebullitive flux measured with bubble traps,. The source contribution of terrestrial and aquatic vegetation to the lake sediment carbon (C), the substrate for methanogens, was investigated using δ13C stable isotope analysis and organic carbon-to-nitrogen (C:N) elemental analyses. These data suggest that the organic C in postglacial subarctic lakes are a mixture of allochthonous and autochthonous inputs, with significant C being added by the in-situ decay of submerged vegetation, providing annual organic matter to the sediment. It was found that submerged vegetation density does not influence sediment CH4 concentrations, but rather, among shallow zone cores, the physical structure of the sediments drives most of the variation in ebullitive flux. Among shallow zones, the best predictor of overlying CH4 ebullitive efflux is the sediment porosity. It was also found that total sediment CH4 concentration has a strong negative relationship with ebullitive efflux, meaning that high sediment CH4 concentration is not an indication of high ebullition potential. Increased macrophyte density was not observed to ‘fertilize’ the sediment with organic C, nor did submerged vegetation density have any observed effect on sediment CH4 concentrations, downcore geochemistry, or ebullitive flux. Findings suggest that in a system that is not C-limited, it is perhaps the C quality and not the C quantity that drives the variability in methanogenesis. An investigation into which microbial communities exist in these sediments and in what abundance is required. These data also suggest that anaerobic oxidation of methane (AOM) might also be occurring even in freshwater lake environments, a finding that is implicative in terms of our understanding and modeling of CH4 ebullition and emissions across the Arctic, perhaps yielding new insights into how net emissions might change in the future.

The Alpenquai lake-dwelling is located on Lake Zurich, and can be considered as one of the rare Late Bronze Age lake-dwellings with a pronounced organic-rich cultural layer in the northern Circum-Alpine region. Within a larger research project, investigating the final abandonment of the lakeshores in the Circum-Alpine area at the end of the Late Bronze Age, this setlement has been investigated using a multidisciplinary research design. Combining micromorphology, archaeobotany, palynology, archaeozoology and material culture studies, the formation of the site is reconstructed, and the reasons for its inal abandonment are sought. A highly dynamic lake system that caused a lake water level rise before 900 BC, a regression in the second half of the 9th century BC, and a later transgression, could be detected. The setlement appears to have been established during the lake regression, and abandoned during the transgression, proving a high degree of environmental adaptation by its inhabitants.

The present study aims to investigate the comparative corrosion of lightweight metals such as aluminum and magnesium in palm biodiesel. Immersion test at room temperature was carried out for each metal for 1440 h. Sample characterization techniques employed include weight loss measurement, SEM (scanning electron microscope), XRD (X-ray diffraction), TAN (total acid number) and FTIR (Fourier transform infrared spectroscopy). Results showed that the corrosion rate of magnesium was much higher compared to that of aluminum. The surface morphology revealed a significant difference between the biodiesel exposed aluminum and magnesium specimens. Upon exposure to biodiesel, the magnesium surface was found to be fully covered by gel-like sticky mass while the aluminum surface remained clean.

The present investigation is a study of physico-chemical parameters of sediment along the Bhavan's College Lake of Andheri, Mumbai. The parameters monitored include pH, alkalinity, chloride, sulphate and phosphate contents. The annual average values of above parameters where found to be 5.75, 239 ppm, 236 ppm, 40 ppm and 0.62 ppm respectively. The weakly acidic pH of the sediment might reduce the pH of lake water below the recommended limit of 6.5 to 8.5 set by CPCB which is necessary for propagation of wild life fishery. It was observed that the excess of accumulated chlorides in the lake sediments have affected the plants growth and biological life of the lake. It was also observed that at some places of the lake, the plants shows suppressed growth and flowering, leaf necrosis, black and flaccid roots, root decay which might be due to accumulation of sulphates in the sediment. Also the formation of dense blue-green algal blooms was observed along the lake which might be due to accumulation of phosphates in the lake sediments. From the overall results of the present investigation it seems that the present condition if neglected might create irreparable damage to the lake ecosystem. It is expected that such type of systematic and continuous monitoring will help to assess the extent and severity of sediment contamination, to evaluate the effects of contaminated sediments on freshwater and marine environment, and to prepare a plan for appropriate remedial action.

Based on a Fourier analysis of a continuous series of observations (188 years) of the water discharge in the Dnieper River, the study has identified qualitatively distinct periods of the discharge formation and a cyclicity constituent of 12,5 years. By means of the piece regression models, which make it possible to define the contribution of annual sums of precipitation and air temperature to the riverine discharge, the study has established the climatic dependence of the hydrological processes. It has also demonstrated that an essential increase in the annual precipitation sums since the 1940s did not result in an increase in the water volume in the Dnieper River. This suggests that the declining sensitivity of the hydrological cycles to the climatic rhythms is the effect of a strong man-made impact. Accordingly, the Dnieper water-volume formation period (1900—1946) optimal for simulation has been defined, which most accurately reflects the impact of natural climatic factors on the riverine discharge. The regression model for the conditions when the water discharge is over1686 m3/s can be used for prognosis (and retrognosis) of extreme hydrological events in the south of the East-European Plain based on the thickness of the bottom sediments of Lake Saki.

La contamination des sédiments lagunaires par les éléments traces métalliques constitue un danger pour l’eau, les espèces vivantes et pour la santé de l’homme. L’objectif de cette étude est d’évaluer le niveau de contamination des sédiments de la lagune Ouladine en éléments traces. Les éléments traces (Pb, Zn, Cu, Cd et Cr) ont été dosés dans les sédiments lagunaires à l’aide d’un spectromètre d’absorption atomique de type VARIAN AA 20. L’intensité de la contamination des sédiments a été estimée à partir du calcul de plusieurs indices, notamment le Facteur de Contamination (FC), le Degré de Contamination modifié (DCm) et l’Indice de Pollution Sédimentaire (IPS). La toxicité des sédiments a été mise en évidence en comparant les concentrations des éléments traces dosés aux valeurs guides américaines SQGs (Sediment Quality Guidelines). Les résultats mettent en évidence l’ordre d’abondance des teneurs en ETM (Eléments Traces Métalliques) des sédiments suivants : Cr (83,92 mg.kg-1)>Pb (62,03 mg.kg-1)>Zn (60,06 mg.kg-1)> Cu (13,76 mg.kg-1)> Cd (1,45 mg.kg-1). Le Facteur de Contamination (FC) et le Degré de Contamination modifiée (DCm) révèlent une contamination faible à considérable. Les valeurs de l’IPS montrent que les sédiments de la lagune Ouladine sont faiblement pollués sauf à la station S7 où les sédiments sont sains. Hormis le Zinc, les autres ETM dosés s’avèrent néfastes pour les organismes vivants de la lagune Ouladine à toutes les stations qui ont fait l’objet d’échantillonnage.

Preliminary studies of the palynoflora from the Lavanttal Basin show a relatively rich assemblage of pollen and spores. The palynoflora comprises at least 17 different kinds of spores, representing the Bryophyta (Sphagnum), Lycopodiophyta (Lycopodium, Selaginella), and the Pteridophyta (Dryopteris, Osmunda, Pteris), about 20 different pollen types of conifers assignable to Cupressaceae and Pinaceae, and 130-160 different kinds of angiosperm pollen. In this study, we describe all spores together with pollen from two seed plants, i.e. Ginkgo (Ginkgophyta) and Ephedra (Gnetophyta). The fossil spores and pollen grains are preserved in phosphoritic nodules. Absence of palynomorphs characteristic of marine settings and presence of numerous freshwater algae (diatoms, dinoflagellates, and different green algae) indicate freshwater environments. This is also supported by sedimentological observations suggestive of wetland surroundings, characterised by lakes, swamps, streams, rivers and floodplain areas. The taxa reported here all seem to represent part of azonal vegetation with plants growing in swamps, on hummocks, along border of lakes or streams, on levees, or on sandy patches of floodplains. Preliminary results suggest that the vegetation thrived under a relatively warm and humid climate.

Outcrops and cores from the top of the lacustrine Tipton Member and the base of the Wilkins Peak Member (~51.5 Ma) of the Eocene Green River Formation, Bridger Basin in southwestern Wyoming yield a wide variety of sedimentary deformation features many of which are laterally extensive for more than 50 km. They include various types of folds, load structures, pinch-and-swell structures, microfaults, breccias and sedimentary dikes. In most cases deformation is represented by hybrid brittle–ductile structures exhibiting lateral variation in deformation style. These occur in low-energy, profundal organic-rich carbonate mudstones (oil shales), trona beds, tuffs, and profundal to sublittoral silty carbonate deposited in paleolake Gosiute. The deformation is not specific to the depositional environment because sedimentary units stratigraphically higher with similar facies show no deformation. The studied interval lacks any evidence for possible trigger mechanisms intrinsic to the deposition...

Microscopic tephra layers ('cryptotephras') represent important age-equivalent stratigraphic markers utilised in many palaeoenvironmental reconstructions. When used in conjunction with proximal records of volcanic activity they can also provide information about volcanic ash cloud fallout and frequency. However, the spatial distributions of tephra layers can be discontinuous even within the same region. Understanding the deposition and post-depositional redistribution of tephra is vital if we are to use cryptotephras as records of ash cloud occurrence and chronostratigraphic markers. The discrete nature of tephra layers also allows for detailed study into processes of deposition and reworking which affect many palaeoenvironmental proxy records. We undertook a multi-core study in order to examine the historical tephrostratigraphy of a raised peatland in Northern Ireland. Three tephra layers originating from Iceland (Hekla 1947, Hekla 1845 and Hekla 1510) are present in 14 of the 15 cores analysed. This suggests that in areas not influenced by snowfall or anthropogenic disturbance at the time of tephra delivery, the presence or absence of a tephra layer is generally consistent across a peatland of this type. However, tephra shard counts (per unit area) vary by an order of magnitude between cores. These intra-site differences may confound the interpretation of shard counts from single cores as records of regional ash cloud mass/density. Bootstrap resampling analysis suggests that total shard counts from multiple cores are required in order to make a reliable estimate of median shard counts for a site. The presence of three historical tephras in 14 cores enables a spatio-temporal analysis of the long-term apparent rate of carbon accumulation (LARCA) in the peatland. Substantial spatial and temporal variations in LARCA are identified over the last ~450 years. This high variability needs to be taken into account when designing studies of peatland carbon accumulation.

Thick lake sediments discovered in the southern part of the Czech Republic provide a high-resolution archive for detailed study of paleoenvironmental changes during the Late Pleistocene to Holocene in eastern-central Europe. Until recently, no similar records were available for this important region in the transition from oceanic to continental macro-climatic settings. Using a multi-proxy approach that combines sedimentological, pollenanalytical, paleozoological (Chironomids), geochemical and mineral-magnetic methods we demonstrate that major climatic events of the Late Glacial can be correlated with Atlantic rather than continental regimes as reported in paleoclimatic literature for the area of the interest. The sensitivity of applied biological and abiological techniques to climatically-driven processes allows trans-regional comparisons and enables us to discuss the pattern of geographic variation in these processes. We are able to establish a clear relationship between vegetation cover, soil development and erosional processes. A short-term intra-Alleröd cool event has been correlated with the Gerzensee oscillation. Proxy evidence suggests that the early half of the Younger Dryas was rather humid, whereas the latter half was dry and had significant impact on vegetation, sedimentary dynamics and lake level status during the YD/Preboreal transition.

Sediments are solid, fragmented particulate matter (silt, sand, and gravel), which are transported and deposited by physical processes such as water, wind, and ice. Sediments consist of loose, solid particles originating from the weathering and erosion of rocks, or chemical precipitation from solution, including secretion by organisms in water.

Inland water sediments receive large quantities of terrestrial organic matter1–5 and are globally important sites for organic carbon preservation5,6. Sediment organic matter mineralization is positively related to temperature across a wide range ofhigh-latitudeecosystems6–10,butthesituationinthetropics remainsunclear.Hereweassessedtemperatureeffectsonthe biological production of CO2 and CH4 in anaerobic sediments of tropical lakes in the Amazon and boreal lakes in Sweden. On the basis of conservative regional warming projections until 2100 (ref. 11), we estimate that sediment CO2 and CH4 productionwillincrease9–61%abovepresentrates.Combining the CO2 and CH4 as CO2 equivalents (CO2eq; ref. 11), the predicted increase is 2.4–4.5 times higher in tropical than boreal sediments. Although the estimated lake area in low latitudes is 3.2 times smaller than that of the boreal zone, we estimate that the increase in gas production from tropical lake sediments would be on average 2.4 times higher for CO2 and 2.8 times higher for CH4.The exponential temperature response of organic matter mineralization, coupled with higher increases in the proportion of CH4 relative to CO2 on warming, suggests that the production of greenhouse gases in tropical sediments will increase substantially. This represents a potential large-scale positive feedback to climate change.

Skriufonnen is a small cirque glacier (0.03 km2) in the continental mountains of Rondane in southern Norway. At
present, it is the only glacier in Rondane, and very little is known about Holocene glacier fluctuations in this
region. Direct observations of the glacier began in 2002, since which time Skriufonnen has been in a state of
strong decline. In order to provide a temporal context, past glacier fluctuations were reconstructed based on a
series of short HTH gravity cores (n = 8) and long piston cores (n = 6) retrieved from three downstream lakes
of Skriufonnen. The coreswere analysed for selectedmagnetic properties (χbulk, ARM, SIRM, 77 K/293 K), organic
content (LOI), and geochemical trace elements. Soil catchment samples (n = 6) were collected along a transect
running from the three lakes up to the present glacier terminus. Bulk susceptibility (χbulk) measurements show
that the finest fractions systematically return the highest values and that ferromagnetic minerals are depleted
with distance to the glacier front. Thismeans that periods dominated by paramagneticminerals indicate very little
or no glacier activity, whereas intervals with more ferromagnetic minerals suggest increased glacier activity. The
quantitative core analyses indicate that Skriufonnen existed prior to 10,200 b2k (years before A.D. 2000) and
disappeared ~10,000 b2k. No glacier activity is recorded from c. 10,000 b2k until the glacier reoccurred at the
onset of the local Neoglacial period, c. 4000 b2k. The glacier attained its maximum extent between 3200 and
2400 b2k and during the end of the ‘Little Ice Age’ (LIA) c. A.D. 1800. Neoglacial fluctuations of Skriufonnen are
in line with shifts in local summer temperatures and show a delayed Neoglacial inception compared to western
Norway.

Sedimentary evidence spanning the last 3500 years from cores taken from the centre of Gormire Lake, Cleveland, northeast England, points to two periods of deforestation and catchment erosion. The first, mainly late Iron Age/Romano-British phase, began c. 200 BC and ended c. AD 600. The second began c. AD 1200, the time of early Monastic activity, and continued into the nineteenth century. The chronology for the core rests on '3Cs, 2"sPb and "C measurements and on the history of lead accumulation in the sediments. The majority of the AMS "C dates are shown to be too old to varying degrees, depending on the source of the organic matter in the sediments. The record of vegetation change is derived from pollen analysis. Evidence for changes in sediment composition and source and for catchment erosion comes from magnetic measurements, element analyses using XRF, and organic biogeochemical analyses. There is a high degree of coherence between all these lines of evidence. Interpretation of the magnetic record is complicated as a result of the formation of biogenic magnetite by magnetotactic bacteria, especially during periods of minimal erosion, by the presence of the authigenic magnetic sulphide greigite and by probable magnetite dissolution. Despite these modifications to the magnetic mineral assemblage in the sediments, magnetic indications of catchment erosion are clearly distinguishable, especially in the record of the antiferromagnetic minerals haematite and goethite. Partial estimates of catchment erosion rates are presented, based on the evidence from the sediments from the deepest part of the lake. a simple bathymetry with a narrow zone of fringing reedswamp and fen, best developed to the northeast of the open water. The catchment is underlain by sedimentary rocks of Lower Jurassic age, upon which a range of brown earth to podzolic soils have developed. The vegetation in the immediate vicinity of the lake is deciduous woodland that dates back at least to the sixteenth century, though changing grazing pressures and land use in the surrounding area have led to changes in structure and species composition through time. Above the woodland lies an area of largely heather and bracken dominated moorland. Much of the

Palaeontological research on the Miocene and Pliocene oras and faunas of Iceland date back to the 1770's. At that time, plant fossils from Iceland were considered belonging to a single ora, and in the early 20th century scientist considered this ora of Eocene age. During the past few decades systematic palaeontology, palaeoclimatology, stratigraphy, and palaeogeography have been linked to results from isotopic (K/Ar and Ar/Ar) absolute age determinations and palaeomagnetic measurements of Cainozoic lavas in Iceland. As a result, numerous fossil oras and a few faunas identied from terrestrial sediments in Iceland are now known to give a contiguous record dating back 15 Ma. The oldest oras are therefore Middle Miocene in age. Younger oras are quite different from the older ones and their composition changed as the Miocene came to an end. Gradual cooling that occurred on Iceland since 12 Ma, when the climate was mild with no dry season and warm summers, and continuous isolation of Iceland, in the northern North Atlantic, had its affect on the Icelandic ora. Thermophilous plants soon became extinct and more cold tolerant species became prominent.

Arctic glaciers are currently undergoing major changes, but accurate knowledge about how they varied during the entire Holocene is still scarce. Here we present a new complete glacier record from Austre Okstindbreen in Nordland, northern Norway. This reconstruction is based on a number of short and long cores retrieved from several downstream basins, which have been analyzed by a suite of methods including geochemical elements (XRF), rock magnetic properties, dry bulk density (DBD) and Loss-on-ignition (LOI). Lake sediment distribution was surveyed and mapped prior to coring by the use of ground penetrating radar (GPR). Independently lichen-dated marginal moraines and historical information about the glacier frontal positions from old photographs and maps have made it possible to link the moraine sequence to the 210Pb dated lake sediment chronology. This integrated approach reveals that Austre Okstindbreen is the first known glacier in Scandinavia to possibly have survived the “Holocene Thermal Optimum”. It also brackets the four largest glacier advances to c 7400–7000, 1400–1200, 900–700 and 300–150 years before AD 2000 (b2k). In contrast to most reconstructed glaciers in Scandinavia, the largest glacier advance was not associated with the “Little Ice Age”, but rather to an earlier period centred at 1300 b2k. Both the moraine chronology and the lacustrine records document this Neoglacial advance. Compared to other glacier reconstructions from the Northern Hemisphere, we identify near-synchronous glacier advances occurring roughly at 4000 b2k; 2700 b2k; 1300 b2k and during the “Little Ice Age”. These correlative advances across the Northern Hemisphere suggest that these observed centennial-scale events are a shared feature regardless of the large geographical distances separating them. Some minor discrepancies between different geographical areas may be caused by lack of precise dating, but local climatic conditions may play a role as well.

About 5,000 years ago near Morasko (the district of the present-day city of Poznañ, western Poland) the largest known iron meteorite shower in Central Europe took place. The evidence of that impact, documented so far, comprises numerous iron meteorite fragments distributed over an area of approximately 3 km 2 and at least six meteorite impact craters with a maximum diameter of about 100 m. The present paper reviews the most recent findings related to the meteorite, craters, processes of their formation, as well as the environmental effects of the impact in the Morasko area. The most important findings, reported in this review cover: 1) the recognition of two new minerals in the meteorite: moraskoite and czochralskiite; 2) the identification and detailed analysis of the ejecta layer around the craters and underlying paleosoil providing evidence for the mid-Holocene age of the impact; 3) the numerical modelling constraining the range of likely physical properties of the impactor, e.g. the diameter of the projectile forming the largest crater and its landing velocity (c. 1.5 m and 10 km/s, respectively);4) the studies of the nearby lake and peat deposits revealing restricted environmental effects of the impact. The Morasko craters field is currently one of the best-studied examples of small/moderate-sized meteorite impact in unconsolidated sediments.

The carbonate-rich sediments of the Eocene Green River Formation (53–43 Ma) were deposited in a complex lake system in present-day Wyoming, Colorado and Utah during the Laramide orogeny. Although syndepositional tectonic activity has been inferred previously for this interval, sedimentary deformation features linked to ancient earthquakes have never previously been studied.
Stratigraphic intervals with synsedimentary deformation features were studied at several locations in all the sub-basins to provide information on the paleotectonic history of the area. Laterally extensive deformed horizons are common in laminated deposits of Fossil Basin (WY), and include folds, water-escape structures, dikes, microfaults, and chaotically brecciated intervals that preserved flow structures. These indicate hydrofracturing, dewatering and the liquified state of sediments during deformation. Sediments deposited in sublittoral environments of the Bridger Basin (WY), at the boundary between the Tipton Shale and Wilkins Peak members, also show evidence of synsedimentary deformation. These features, some traceable laterally for tens of kilometers, imply tectonically influenced changes in sedimentary processes during that time. Pervasive deformation features are also present in the Mahogany Oil Shale Zone in the Piceance Creek and Uinta basins (CO, UT). Behavior ranges from brittle (fragmented laminites and faulted beds) to plastic (convolution, folds), to cm- to m-scale cracks filled with injected sediment. Deformation styles were controlled by the rheological properties of the host sediment.
All these structures resulted from increased pore pressures from cyclic loading, and vertical and horizontal stresses induced by ground motion. Typically, undeformed strata separate the deformed horizons, which indicates that brief (tectonically-driven) events affected only near-surface sediments that were rheologically susceptible to syndepositional deformation.

Shells of subfossil snails and bivalves commonly noted in deposits of the Eemian Interglacial were used by several authors as more or less important stratigraphic indicators. In Poland, they have been noted in 35 sections, 20 of which are described as basic ones.Molluscan assemblages found at these sites include 60 species of freshwater molluscs and 58 species of land snails, the former being dominant. Climatic tolerance of particular species is the main attribute deciding on their stratigraphic values. Cold-tolerant snails are typical of the preceding Late Glacial and some of them occur also in early phases of the interglacial, while species connected with moderate climate and warm-demanding ones characterise the middle part of the Eemian Interglacial. The freshwater snail Belgrandia marginata is typical of the climatic optimum of this interglacial. Particular species of molluscs were related to regional pollen assemblage zones of the Eemian Interglacial in Poland.