Geochemistry and varves on a sediment profile from Hämelsee, Germany

The Alleroed biozone encompasses 625 calendar years. The pollenanalytically determined upper and lower boundary is in good agreement with the development of the microfacies. The study of the macrofacies of annually laminated sediments is a useful tool. It yields not only very accurate varve counts but also paleoclimatological and environmental proxy data. The LST -event occurred 200 years before the Younger Dryas. They exIsts no relationship. However, during ten to twenty years following the LST, the lake deposited sediments similar to those at the beginning of the Younger Dryas, which should be due to comparable meteorological conditions.

Downcore rock-magnetic properties of ICDP Core 5045-1, Lake Ohrid

The bulk magnetic mineral record from Lake Ohrid, spanning the past 637 kyr, reflects large-scale shifts in hydrological conditions, and, superimposed, a strong signal of environmental conditions on glacial-interglacial and millennial timescales. A shift in the formation of early diagenetic ferrimagnetic iron sulfides to siderites is observed around 320 ka. This change is probably associated with variable availability of sulfide in the pore water. We propose that sulfate concentrations were significantly higher before ~320 ka, due to either a higher sulfate flux or lower dilution of lake sulfate due to a smaller water volume. Diagenetic iron minerals appear more abundant during glacials, which are generally characterized by higher Fe/Ca ratios in the sediments. While in the lower part of the core the ferrimagnetic sulfide signal overprints the primary detrital magnetic signal, the upper part of the core is dominated by variable proportions of high- to low-coercivity iron oxides. Glacial sediments are characterized by high concentration of high-coercivity magnetic minerals (hematite, goethite), which relate to enhanced erosion of soils that had formed during preceding interglacials. Superimposed on the glacial-interglacial behavior are millennial-scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Like the processes on glacial-interglacial timescales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both environmental conditions on land and intra-lake processes.

FTIR-inferred biogeochemical properties for the past 3.6 Myr in the sediment record of core ICDP5011-1 in Lake Elgygytgyn, NE Russia

A number of studies have shown that Fourier transform infrared spectroscopy (FTIR) can be applied to quantitatively assess lacustrine sediment constituents. In this study, we developed calibration models based on FTIR for the quantitative determination of biogenic silica (BSi; n = 420; gradient: 0.9-56.5%), total organic carbon (TOC; n = 309; gradient: 0-2.9%), and total inorganic carbon (TIC; n= 152; gradient: 0-0.4%) in a 318 m-long sediment record with a basal age of 3.6 million years from Lake El'gygytgyn, Far East Russian Arctic. The developed partial least squares (PLS) regression models yield high cross-validated (CV) R2CV = 0.86-0.91 and low root mean square error of cross-validation (RMSECV) (3.1-7.0% of the gradient for the different properties). By applying these models to 6771 samples from the entire sediment record, we obtained detailed insight into bioproductivity variations in Lake El'gygytgyn throughout the middle to late Pliocene and Quaternary. High accumulation rates of BSi indicate a productivity maximum during the middle Pliocene (3.6-3.3 Ma), followed by gradually decreasing rates during the late Pliocene and Quaternary. The average BSi accumulation during the middle Pliocene was ~3 times higher than maximum accumulation rates during the past 1.5 million years. The indicated progressive deterioration of environmental and climatic conditions in the Siberian Arctic starting at ca. 3.3 Ma is consistent with the first occurrence of glacial periods and the finally complete establishment of glacial-interglacial cycles during the Quaternary.

Varve sediments of the Lake Meerfelder Maar

Lake Meerfelder Maar (Germany) provides a varved record from the Last Glacial/Interglacial transition back to ca 1500 years BP. This study shows results for the Holocene sequence from new cores collected in 2009 based on varve counting, microfacies and micro-XRF analyses. The main goal of combining those analyses is to provide a new approach for interpreting long-term palaeolimnological proxy data and testing the climate-proxy stationarity throughout the current interglacial period. Varve counting provides a new independent Holocene chronology (MFM2012) with an estimated counting error of 1-0.5% and supported by 14C dating. Varve structure and thickness and geochemical composition of the varves give information about the main environmental processes that affect the lake and its catchment as well as the possible climate variability behind. Varves are couplets of i) a spring/summer laminae composed of monospecific diatom blooms and ii) an autumn/winter sub-layer made of minerogenic material and re-worked sediments. Thickness of the varves and sub-layers reflect lake variability and allow seasons to be distinguished as well as seasonal proxies. Changes in the winter minerogenic influx into the lake are reflected by Ti intensities and the Si/Ti ratio as a indicator for diatom concentration, which can be used as a proxy for water circulation during the early spring. Long-term variability of geochemical composition shows a reduction of the detrital material input (Ti) at 5,000 varve yrs BP and a visible sensitivity to water mixing (Si/Ti) during the Late Holocene. Variations of Ti intensities during the early and mid-Holocene do not show a clear relationship with climate. In contrast, higher values of the Si/Ti ratio together with thicker varves have been interpreted as wind-stress phases, which coincide with centennial variability of European cold/wet episodes during the Late Holocene. Our findings show that a long-term change in the lake and/or variability of the climate system can influence proxy sensitivity of a lacustrine record.

Geochemistry and geomicrobiology profiles of ferruginous sediment, Lake Towuti, Indonesia

Lake Towuti is a tectonic basin, surrounded by ultramafic rocks. Lateritic soils form through weathering and deliver abundant iron (oxy)hydroxides but very little sulfate to the lake and its sediment. To characterize the sediment biogeochemistry, we collected cores at three sites with increasing water depth and decreasing bottom water oxygen concentrations. Microbial cell densities were highest at the shallow site - a feature we attribute to the availability of labile organic matter and the higher abundance of electron acceptors due to oxic bottom water conditions. At the two other sites, OM degradation and reduction processes below the oxycline led to partial electron acceptor depletion. Genetic information preserved in the sediment as extracellular DNA provides information on aerobic and anaerobic heterotrophs related to Actinobacteria, Nitrospirae, Chloroflexi and Thermoplasmatales. These taxa apparently played a significant role in the degradation of sinking organic matter. However, extracellular DNA concentrations rapidly decrease with core depth. Despite very low sulfate concentrations, sulfate-reducing bacteria were present and viable in sediments at all three sites, as confirmed by measurement of potential sulfate reduction rates. Microbial community fingerprinting supported the presence of taxa related to Deltaproteobacteria and Firmicutes with demonstrated capacity for iron and sulfate reduction. Concomitantly, sequences of Ruminococcaceae, Clostridiales and Methanomicrobiales indicated potential for fermentative hydrogen and methane production. Such first insights into ferruginous sediments show that microbial populations perform successive metabolisms related to sulfur, iron and methane. In theory, iron reduction could reoxidize reduced sulfur compounds and desorb OM from iron minerals to allow remineralization to methane. Overall, we found that biogeochemical processes in the sediments can be linked to redox differences in the bottom waters of the three sites, like oxidant concentrations and the supply of labile OM. At the scale of the lacustrine record, our geomicrobiological study should provide a means to link the extant subsurface biosphere to past environments.

Age model and chemistry of sediment core STK7 from Steisslinger See

Stable isotope records for carbon and oxygen in bulk carbonates, carbon in bulk organic matter, and for total and chromium-reducible sulfur in a lacustrine sediment core from Lake Steisslingen (Southwest Germany) show several distinct and abrupt shifts during the last 15,000 years. Variations in the isotopic composition of authigenic carbonates indicate two major phases in the lake history. In the pre-Holocene, the hydrological budget of the lake was apparently stable. Variations of delta18O values of authigenic carbonates were, therefore, dominantly controlled by temperature changes. A decrease in the delta18Ocarb values of about 2 per mil at the Allerød/Younger Dryas transition is interpreted as a drop in mean annual air temperatures of approximately 5°C. An abrupt temperature increase of a similar magnitude is inferred at the Younger Dryas/Preboreal boundary. Throughout most of the Holocene, the isotopic composition of authigenic carbonates was influenced by marked changes in the hydrological budget of the lake. A major positive excursion in the delta13Ccarb and delta18Ocarb values at the beginning of the Atlantic and a smaller one in the Preboreal were related to evaporation effects, which indicate that dry climatic conditions must have prevailed at that time. A simultaneous increase in delta13C values of bulk organic matter at the beginning of the Atlantic suggests a high level of productivity in the lake. As a consequence, aqueous sulfate became limited as indicated by variations in the delta34S values of total and chromium-reducible sedimentary sulfur. Therefore, we conclude that the beginning of the Atlantic was characterized not only by dry but also by warm climatic conditions, which triggered a higher productivity in the lake. In the Subatlantic sediments, large variations in carbon, oxygen, and sulfur isotope ratios were observed as a result of human activities, causing considerable perturbations in the biogeochemical element cycling of Lake Steisslingen. Results obtained by the study of the continuous 15 ka record of Lake Steisslingen document clearly that isotopic proxy data from lacustrine sediments can provide useful information on environmental and climatic changes of local, regional, and in the case of the Younger Dryas event, of even hemispherical significance.

Core scans and lithologic analysis of Subglacial Lake Whillans sediment cores

The hydrologic system beneath the Antarctic Ice Sheet is thought to influence both the dynamics and distribution of fast flowing ice streams, which discharge most of the ice lost by the ice sheet. Despite considerable interest in understanding this subglacial network and its affect on ice flow, in situ observations from the ice sheet bed are exceedingly rare. Here we describe the first sediment cores recovered from an active subglacial lake. The lake, known as Subglacial Lake Whillans, is part of a broader, dynamic hydrologic network beneath the Whillans Ice Stream in West Antarctica. Even though "floods" pass through the lake, the lake floor shows no evidence of erosion or deposition by flowing water. By inference, these floods must have insufficient energy to erode or transport significant volumes of sediment coarser than silt. Consequently, water flow beneath the region is probably incapable of incising continuous channels into the bed and instead follows preexisting subglacial topography and surface slope. Sediment on the lake floor consists of till deposited during intermittent grounding of the ice stream following flood events. The fabrics within the till are weaker than those thought to develop in thick deforming beds suggesting subglacial sediment fluxes across the ice plain are currently low and unlikely to have a large stabilizing effect on the ice stream's grounding zone.

Sedimentary n-alkanes, their hydrogen isotopes, GDGTs and d15N as well as d13Corg of lake Nam Co, Tibet

The transition from the last Glacial to the current Interglacial, the Holocene, represents an important period with climatic and environmental changes impacting ecosystems. In this study, we examined the interplay between the Indian Ocean Summer Monsoon (IOSM) and the Westerlies at lake Nam Co, southern Tibet to understand the climatic effects on the ecosystem. Different organic geochemical proxies (n-alkanes, glycerol dialkyl glycerol tetraethers, dD, d13Corg, d15N) are applied to reconstruct the environmental and hydrological changes on one of the longest available paleorecords at the Tibetan Plateau. Based on our paleohydrological dD proxies, the aquatic signal lags the terrestrial one due to specific ecological thresholds, which, in addition to climatic changes, can influence aquatic organisms. The aquatic organisms' response strongly depends on temperature and associated lake size, as well as pH and nutrient availability. Because the terrestrial vegetation reacts faster and more sensitively to changes in the monsoonal and climatic system, the dD of n-C29 and the reconstructed inflow water signal represent an appropriate IOSM proxy. In general, the interplay of the different air masses seems to be primarily controlled by solar insolation. In the Holocene, the high insolation generates a large land-ocean pressure gradient associated with strong monsoonal winds and the strongest IOSM. In the last glacial period, however, the weak insolation promoted the Westerlies, thereby increasing their influence at the Tibetan Plateau. Our results help to elucidate the variable IOSM, and they illustrate a remarkable shift in the lake system regarding pH, d13Corg and d15N from the last glacial to the Holocene interglacial period.

Soil and sediment analyses of Lake La Thuile (Bauges, France)

Data used in the study of the evolution of soils of Lake La Thuile catchment, in relation with the long sediment sequence of the lake. Data of pH, Loss On Ignition, Oxygen and Hydrogen Index (Rock-eval analyses) and mineral geochemistry (Portative XRF, Al2O3/TiO2 and K2O/TiO2 ratios) are available for each soil horizons that have been studied in the catchment. For sediments, data of Oxygen and Hydrogen Index (Rock-eval analyses), mineral geochemistry (Portative XRF, Al2O3/TiO2 and K2O/TiO2 ratios), erosion, soil evolution modelization and the ages are available according to depth.

A mesocosm analytical study on the impact of freshwater mussel (Lamellidens marginalis Lamarck) mediated bioturbation and biodeposition on some ecological factors of a freshwater lake

The biotic potential of the benthic filter feeding freshwater bivalve mollusc Lamellidens marginalis (Lamarck) influencing the nutrient dynamics of the bottom sediments of the lake by means of biodeposition and bioturbation activities were analysed using a lake mesocosm experiment. Five control as well as experimental mesocosms was maintained up to 60 days (d). The factors studied included the percentage of water content of the sediment, percentage of total nitrogen, percentage of organic matter along with the total phosphorus and humic acid content. While total phosphorus and humic acid content of the experimental mesocosoms showed gradual and significant increases from 30d of the experiment to reach the maximum levels after 60d, the percentage of organic matter registered significant increases right from 15d onwards and reached the maximum values after 60d. On the other hand, while the percentage of water content of the sediments of the experimental mesocosoms increased only up to 30d experiment, percentage of nitrogen was increased during the first half and at the fag end of the experiment. All the investigated ecological factors were found to be significantly influenced by the presence of L. marginalis in the experimental mesocosms. The study indicated that the mussel influence the nutrient dynamics of the inhabitant ecosystem through the processes of excretion, biodeposition of pseudofaeces and faeces, along with the bioturbation of the sediments brought about by their ploughing movements. KEYWORDS: freshwater mussel, Lamellidens marginalis, bioturbation, biodeposition, mesocosms.

Quantifying uplift and denudation of a thermally heterogeneous crust: a detailed multi-thermochronometeric study of central west Britain

Topography is often thought as exclusively linked to mountain ranges formed by plates collision. It is now, however, known that apart from compression, uplift and denudation of rocks may be triggered by rifting, like it happens at elevated passive margins, and away from plate boundaries by both intra-plate stress causing reactivation of older structures, and by epeirogenic movements driven by mantle dynamics and initiating long-wavelength uplift. In the Cenozoic, central west Britain and other parts of the North Atlantic margins experienced multiple episodes of rock uplift and denudation that have been variable both at spatial and temporal scales. The origin of topography in central west Britain is enigmatic, and because of its location, it may be related to any of the processes mentioned above. In this study, three low temperature thermochronometers, the apatite fission track (AFT) and apatite and zircon (U-Th-Sm)/He (AHe and ZHe, respectively) methods were used to establish the rock cooling history from 200◦C to 30◦C. The samples were collected from the intrusive rocks in the high elevation, high relief regions of the Lake District (NW England), southern Scotland and northern Wales. AFT ages from the region are youngest (55–70 Ma) in the Lake District and increase northwards into southern Scotland and southwards in north Wales (>200 Ma). AHe and ZHe ages show no systematic pattern; the former range from 50 to 80 Ma and the latter tend to record the post-emplacement cooling of the intrusions (200–400 Ma). The complex, multi-thermochronometric inverse modelling suggests a ubiquitous, rapid Late Cretaceous/early Palaeogene cooling event that is particularly marked in Lake District and Criffell. The timing and rate of cooling in southern Scotland and in northern Wales is poorly resolved as the amount of cooling was less than 60◦C. The Lake District plutons were at >110◦C prior to the early Palaeogene; cooling due to a combined effect of high heat flow, from the heat producing granite batholith, and the blanketing effect of the overlying low conductivity Late Mesozoic limestones and mudstones. Modelling of the heat transfer suggests that this combination produced an elevated geothermal gradient within the sedimentary rocks (50–70◦C/km) that was about two times higher than at the present day. Inverse modelling of the AFT and AHe data taking the crustal structure into consideration suggests that denudation was the highest, 2.0–2.5 km, in the coastal areas of the Lake District and southern Scotland, gradually decreasing to less than 1 km in the northern Southern Uplands and northern Wales. Both the rift-related uplift and the intra-plate compression poorly correlate with the timing, location and spatial distribution of the early Palaeogene denudation. The pattern of early Palaeogene denudation correlates with the thickness of magmatic underplating, if the changes of mean topography, Late Cretaceous water depth and eroded rock density are taken into consideration. However, the uplift due to underplating alone cannot fully justify the total early Palaeogene denudation. The amount that is not ex- plained by underplating is, however, roughly spatially constant across the study area and can be referred to the transient thermal uplift induced by the mantle plume arrival. No other mechanisms are required to explain the observed pattern of denudation. The onset of denudation across the region is not uniform. Denudation started at 70–75 Ma in the central part of the Lake District whereas the coastal areas the rapid erosion appears to have initiated later (65–60 Ma). This is ~10 Ma earlier than the first vol- canic manifestation of the proto-Iceland plume and favours the hypothesis of the short period of plume incubation below the lithosphere before the volcanism. In most of the localities, the rocks had cooled to temperatures lower than 30◦C by the end of the Palaeogene, suggesting that the total Neogene denudation was, at a maximum, several hundreds of metres. Rapid cooling in the last 3 million years is resolved in some places in southern Scotland, where it could be explained by glacial erosion and post-glacial isostatic uplift.

Multi-victim sexual assault : a case study in rural Australia

Objective: There is a paucity of information regarding cases of multi-victim sexual assault of children. The reported incidence suggests that these cases are rare. The aim of this paper is to provide practitioners with information about effective intervention strategies arising out of the direct experience of managing a case of multi-victim sexual assault in an Australian rural community. --------- Method: A descriptive, case-report methodology summarizing the investigation and intervention in a case of multi-victim sexual assault is reported. A community based intervention arising out of the disclosures of 21 male children is described. The intervention occurred at an individual, group, and community level using a coordinated multi-disciplinary team and natural helping networks. ---------- Results: The coordination of police and welfare services increased the communication flow to victims, their families, and the community. The case also demonstrated the utility in regularly briefing political and bureaucratic authorities as well as local officials about emergent issues. Coordinating political and bureaucratic responses was essential in obtaining ongoing support and sufficient researching to enable the effective delivery of services. ---------- Conclusions: Interventions were focused at an individual, group, and community level using a coordinated multi-disciplinary team and natural helping networks. This provided a choice of services which were sensitive to the case setting. Recommendations are offered for practitioners who are confronted with similar events. While this paper describes an approach for intervening in a case of multi-victim sexual assault, further empirical research is needed to enable service deliverers to efficaciously target interventions which offer choice to victims and their families.

A study on matching and multi-objective fuzzy control strategy of heavy truck suspension system

Matching method of heavy truck-rear air suspensions is discussed, and a fuzzy control strategy which improves both ride comfort and road friendliness of truck by adjusting damping coefficients of the suspension system is found. In the first place, a Dongfeng EQ1141G7DJ heavy truck’s ten DOF whole vehicle-road model was set up based on Matlab/Simulink and vehicle dynamics. Then appropriate passive air suspensions were chosen to replace the original rear leaf springs of the truck according to truck-suspension matching criterions, consequently, the stiffness of front leaf springs were adjusted too. Then the semi-active fuzzy controllers were designed for further enhancement of the truck’s ride comfort and the road friendliness. After the application of semi-active fuzzy control strategy through simulation, is was indicated that both ride comfort and road friendliness could be enhanced effectively under various road conditions. The strategy proposed may provide theory basis for design and development of truck suspension system in China.

Raman spectroscopic study of the multi-anion mineral dixenite CuMn2+14Fe3+(AsO3)5(SiO4)2(AsO4)(OH)6

The mixed anion mineral dixenite has been studied by Raman spectroscopy, complimented with infrared spectroscopy. The Raman spectrum of dixenite shows bands at 839 and 813 cm-1 assigned to the (AsO3)3- symmetric and antisymmetric stretching modes. The most intense Raman band of dixenite is the band at 526 cm-1 and is assigned to the ν2 AsO33- bending mode. DFT calculations enabled the position of AsO22- symmetric stretching mode at 839 cm-1, the antisymmetric stretching mode at 813 cm-1, and the deformation mode at 449 cm-1 to be calculated. Raman bands at 1026 and 1057 cm-1 are assigned to the SiO42- symmetric stretching vibrations and at 1349 and 1386 cm-1 to the SiO42- antisymmetric stretching vibrations. Both Raman and infrared spectra indicate the presence of water in the structure of dixenite. This brings into question the commonly accepted formula of dixenite as CuMn2+14Fe3+(AsO3)5(SiO4)2(AsO4)(OH)6. The formula may be better written as CuMn2+14Fe3+(AsO3)5(SiO4)2(AsO4)(OH)6•xH2O.

Raman spectroscopic study of the hydroxy-arsenate mineral pharmacolite Ca(HAsO4)•2H2O : implications for aquifer and sediment remediation

The removal of arsenate anions from aqueous media, sediments and wasted soils is of environmental significance. The reaction of gypsum with the arsenate anion results in pharmacolite mineral formation, together with related minerals. Raman and infrared spectroscopy have been used to study the mineral pharmacolite Ca(HAsO4)•2H2O. The mineral is characterised by an intense Raman band at 865 cm-1 assigned to the (AsO4)3- symmetric stretching mode. The equivalent infrared band is found at 864 cm-1. The low intensity Raman band at 886 cm-1 provides evidence for (AsO3OH)2-. A series of overlapping bands in the 300 to 450 cm-1 are attributed to ν2 and ν4 bending modes. Prominent Raman bands at around 3187 cm-1 are assigned to water OH stretching vibrations and the two sharp bands at 3425 and 3526 cm-1 to the OH stretching vibrations of (HOAsO3) units.