fertilizing potential of volcanic ash in ocean surface water the fertilization potential of newly erupted and well preserved ash from the 2000 hekla eruption in iceland was measured for the first time by flow through experiments as previously shown 1 the north atlantic ocean including the subarctic seas surrounding iceland is the largest net sink of the world s oceans for atmospheric co 2 owing to biological drawdown during summer 2 almost complete consumption of phosphate in chlorophyll rich areas of the north atlantic ocean might limit primary production and 3 in the southern pacific ocean and parts of the equatorial pacific ocean iron might limit primary production we found through laboratory experiments that volcanic ash exposed to seawater initially releases large amounts of adsorbed phosphate 1 7 mmol g 21 h 21 iron 37 0 mmol g 21 h 21 silica 49 5 mmol g 21 h 21 and manganese 1 7 mmol g 21 h 21 dissolution of acid aerosols adsorbed to the surface of the ash caused the high initial release of major and trace elements because of the instantaneous dissolution of adsorbed components when newly erupted volcanic ash comes in contact with the ocean surface water macronutrients and bioactive trace metals are released fast enough to become available to support primary production

environmental change during the early cretaceous in the purbeck type durlston bay section dorset southern england a biomarker approach abstract the purbeck type section durlston bay dorset uk exhibits littoral lagoonal to lacustrine facies it shows a gradual climatic environmental change from semi arid conditions associated with evaporites at the jurassic cretaceous transition to a more humid climate at the end of the berriasian though generally organic poor total organic carbon toc the distribution of alkanes hopanes and steranes indicates that the origin of the om is mainly algal bacterial and only changed moderately with the climatic evolution the saline and anoxic bottom water conditions indicated for most of the samples point to the recurrence of salinity stratification within the basin a high contribution of odd numbered c 23 c 31 n alkanes from algaenan containing freshwater algae in particular botryococcus is noted for all the samples despite the low abundance of these organisms in the corresponding palynofacies this prominence probably results from the high resistance to degradation and the selective preservation of botryococcus related lipids the subtle balance of aridity and freshwater inputs favoured both an abundance of botryococcus and the development of anoxia leading to the enhanced preservation of om during the intermediate climatic episode while the conditions were less favourable during the semi arid and more humid episodes

applications of organic geochemistry to paleolimnological reconstructions a summary of examples from the laurentian great lakes the organic matter content of lake sediments contains information that helps to reconstruct past environmental conditions evaluate histories of climate change and assess impacts of humans on local ecosystems the elemental isotopic and molecular compositions of organic matter buried in sediment provide evidence of the biota that have lived in a lake and its catchment area and they serve as proxies of organic matter delivery and accumulation sedimentary records from the north american great lakes provide examples of applications of organic geochemistry to paleolimnological reconstructions the records of these lakes date from retreat of the laurentide ice sheet around 12 ka include the mid holocene hypsithermal and show consequences of recent human changes low corg ntotal ratios indicate that most of the sediment organic matter in the great lakes is from algal production yet changes in biomarker molecule compositions also show that varying amounts of land plant organic matter have been delivered to the lakes elevated algal productivity that accompanies nutrient enrichments of lake waters is recorded as excursions to less negative 13c values in the organic matter of sediments that were deposited in the 1960s and 1970s increased organic carbon mass accumulation rates mirror the isotopic excursions in most parts of the great lakes accumulations of petroleum residues and pyrogenic polycyclic aromatic hydrocarbons in sediments identify fluvial and eolian delivery of organic matter components to different parts of the great lakes emerging applications of multiple and novel organic geochemical proxies to paleolimnological reconstructions are promising yet some potentially important measurements remain underutilized

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

posteruptive impacts of pyroclastic deposits from basaltic andesite stratovolcanoes on surface water composition volcanic ash deposition following explosive eruptions can pose significant hazards for water quality human health agriculture and infrastructure functionality many studies have examined how fresh ash deposition may lower the ph of and introduce a range of potentially toxic elements into exposed surface waters however no study has yet determined the effects on water composition as a result of mechanical pyroclast disaggregation and production of new fresh particle surfaces and increasingly fine grained particles such disaggregation could result from natural posteruptive processes such as debris avalanches lahars or fluvial aeolian transport and human activities such as cleanup efforts or mining of pyroclastic deposits the posteruption time scales of pyroclast disaggregation may vary from months in moist tropical or temperate environments to years or decades in arid settings here we show for the first time in experimental studies that mechanical milling of pyroclasts will introduce a range of elements into exposed waters including al which can be toxic at elevated levels and na which increases the electrical conductivity of solutions the ph of leaching solutions also increases by several log units such dramatic changes on the experimental scale may have implications for surface water composition in posteruptive settings necessitating longer term risk assessments for ecosystem health and consideration of the role of pyroclastic deposits in element cycling in volcanically active regions

rapid releases of metal salts and nutrients following the deposition of volcanic ash into aqueous environments deposition of volcanic ash into aqueous environments leads to dissolution of adsorbed metal salts and aerosols increasing the bioavailability of key nutrients volcanogenic fertilization events could increase marine primary productivity leading to a drawdown of atmospheric co2 here we conduct flow through experiments on unhydrated volcanic ash samples from a variety of locations and sources measuring the concentrations and fluxes of elements into de ionized water and two contrasting ocean surface waters comparisons of element fluxes show that dissolution of adsorbed surface salts and aerosols dominates over glass dissolution even in sustained low ph conditions these surface ash leachates appear unstable decaying in situ even if kept unhydrated volcanic ash from recent eruptions is shown to have a large fertilization potential in both fresh and saline water fluorine concentrations are integral to bulk dissolution rates and samples with high f concentrations display elevated fluxes of some nutrients particularly fe si and p bio limiting micronutrients are released in large quantities suggesting that subsequent biological growth will be limited by macronutrient availability importantly acidification of surface waters and high fluxes of toxic elements highlights the potential of volcanic ash leachates to poison aqueous environments in particular large ph changes can cause undersaturation of caco3 polymorphs damaging populations of calcifying organisms deposition of volcanic ash can both fertilize and or poison aqueous environments causing significant changes to surface water chemistry and biogeochemical cycles

late quaternary variation of lignin composition in core md01 2421 off central japan nw pacific abstract in order to understand the responses of terrestrial vegetation in central japan to global climate changes we have generated the record of lignin composition from core md01 2421 off central japan in the nw pacific during the last 145 000 years by tetramethylammonium hydroxide tmah pyrolysis gas chromatography mass spectrometry gc ms the relative abundance of lignin was significantly low in early mis 1 and mis 5e and higher in mis 5c to early mis 4 this reflects glacial interglacial changes in sea level and riverine runoff the ratio of syringyl s to vanillyl v phenols s v ratio which is a contribution index of angiosperms against gymnosperms was lower in mis 2 mis 4 and mis 6 reflecting the glacial interglacial variation of air temperature the ratio of cinnamyl c to vanillyl v phenols c v ratio which indicates the contribution of grasses was higher in late mis 2 early mid mis 3 and mis 6 the periods of higher c v ratio correspond to the periods of lower sea surface temperatures ssts suggesting a dry and cold climate in late mis 2 mid mis 3 and mis 6

organic matter sources to the water column and surficial sediments of a marine bay sediment trap and net plankton samples were collected monthly for a year at three depths in a marine bay dabob bay washington these materials and subsamples from a sediment box core were analyzed for lignin oxidation products as well as elemental and stable carbon isotope compositions the sediment core was compositionally uniform over its entire 50 cm length the elemental and lignin compositions of the sediment trap and core samples indicate nitrogen rich atomic c n 7 5 plankton derived organic matter mixed with vascular plant debris at most vascular plant debris accounts for 10 nonwinter months to 35 winter months of the total organic carbon in the upper water column 30 m sediment trap samples and consists predominantly of gymnosperm wood along with some nonwoody gymnosperm tissues and angiosperm woods bulk land derived organic matter in dabob bay contains a maximum of 50 vascular plant debris and comprises an average of one third of the total organic carbon in the sediment trap samples and two thirds of the total organic carbon in the underlying sediments lignin in the sediment trap and core samples shows evidence from elevated vanillic acid vanillin ratios of white rot fungal degradation before but not after introduction to the water column at the study site vascular plant debris introduced to the bay has already lost almost half of its initial bulk polysaccharide glucose yields are particularly low whereas rhamnose and fucose are obtained in excess of expected yields and must have additional sources lignin and neutral sugars together account for 20 of the total organic carbon in the sediment trap and core samples overall the sediments of dabob bay compositionally resemble the gymnosperm wood rich particulate material introduced to the overlying water column during winter and poorly record the input of plankton and other types of vascular plant debris during nonwinter months

diagenetic and catagenetic products of isorenieratene molecular indicators for photic zone anoxia a wide range of novel diagenetic and catagenetic products of the diaromatic carotenoid isorenieratene a pigment of the photosynthetic green sulphur bacteria chlorobiaceae has been identified in a number of sedimentary rocks ranging from ordovician to miocene compound identification is based on nmr mass spectrometry the presence of atropisomers and stable carbon isotopes atropisomers contain an axially chiral centre which in combination with other chiral centres results in two or more diastereomers that can be separated on a normal gc column chlorobiaceae use the reverse tca cycle to fix carbon so that their biomass is enriched in 13c high 13c contents of isorenieratene derivatives therefore support their inferred origins isorenieratene derivatives include c 40 c 33 and c 32 diaryl isoprenoids and short chain aryl isoprenoids with additional aromatic and or s containing rings c 33 and c 32 compounds are diagenetic products of c 33 and c 32 carotenoids formed from isorenieratene during early diagenesis through expulsion of toluene and m xylene respectively cyclisation of the polyene acyclic isoprenoid chain can proceed via an intramolecular diels alder reaction followed by aromatisation of the newly formed ring sulphurisation is also an important process during early diagenesis competing with expulsion and cyclisation sulphur bound isorenieratane is released during progressive diagenesis due to cleavage of relatively weak ss and cs bonds cleavage of c c bonds during aromatisation of newly formed rings and during catagenesis yields short chain compounds the inherent presence of a conjugated double bond system in carotenoids implies that similar diagenetic and catagenetic reactions can occur with all carotenoids chlorobiaceae live at or below the oxic anoxic boundary layer and require both light and h 2s the presence of isorenieratene or its diagenetic and catagenetic products in ancient sedimentary rocks and crude oils is therefore an excellent indication for photic zone anoxia in the depositional environment diagenetic and catagenetic products of isorenieratene are expected to find applications in reconstruction of palaeoenvironments and in oil oil and oil source rock correlation studies their presence in several petroleum source rocks suggests that anoxia is an important environmental parameter for the preservation of organic matter

lignin geochemistry of a late quaternary sediment core from lake washington long term lignin stability and paleovegetation patterns were investigated using cuo oxidation products of sediments from an 11 m core of late quaternary sediment collected from the mid basin of lake washington washington state relatively constant yields of lignin derived phenols normalized to organic carbon from the entire core indicate minimal in situ lignin degradation over the last 13 000 years compositional patterns within the phenolic suite and increased corresponding yields from baseextracted sediments indicate that sedimentary lignins are present predominantly as well preserved plant tissue fragments abundance patterns of vanillyl syringyl and cinnamyl phenols record four distinct sequences within the core characterized by 1 a high concentrations of gymnosperm wood in a basal horizon of glacial flour 11 10 m 2 b an essentially pure mixture of nonwoody angiosperm tissues in late pleistocene sediments 10 8 m 3 c relatively high concentrations of angiosperm woods in the bottom half of a limnic peat sequence deposited approximately 10 000 7 000 years b p 8 4 m and 4 d a progressive enrichment in gymnosperm woods at the expense of angiosperm woods over the last 7 000 years in the upper limnic peat 4 0 m vascular plant tissues account for less than half the total sedimentary organic carbon throughout the core

predicted bulk composition of petroleum generated by lower cretaceous wealden black shales lower saxony basin germany the berriasian wealden shale provides the favourable situation of possessing immature to overmature source rock intervals due to differential subsidence within the lower saxony basin hydrocarbon generation kinet ics and petroleum physical properties have been investi gated on four immature wealden shale samples situated in different depth intervals and following the phaseki netics approach of di primio and horsfield aapg bull 90 7 1031 1058 2006 kinetic parameters and phase prediction were applied to a thermally calibrated 1d model of the geodynamic evolution at the location of an overmature well the immature source rocks of all depth intervals comprise kerogen type i being derived from the lacustrine algae botryococcus braunii bulk kinetics of the lower three depth intervals sample 2 4 can be described by one single activation energy ea typical for homogene ous lacustrine organic matter om whereas sample 1 from the uppermost interval shows a slightly broader ea distribution which hints to a more heterogeneous less sta ble om but still of lacustrine origin predicted physical

chemostratigraphy of the posidonia black shale sw germany ii assessment of extent and persistence of photic zone anoxia using aryl isoprenoid distributions aquatic depositional environments where anoxic conditions extend from bottom waters into the photic zone occurred frequently during the geologic past periods of photic zone anoxia pza can be recognized by the presence of specific lipids produced exclusively by the green sulphur bacteria chlorobiaceae that are preserved in the sedimentary record chlorobiaceae perform anoxygenic photosynthesis that requires light penetration into h2s saturated waters sediment samples integrate paleoenvironmental conditions over time intervals ranging from at best a few decades to more commonly several millennia photic zone anoxia recognized in paleoenvironmental analyses is thus defined as episodic with no further interpretation on the duration and persistence of the anoxic events we provide here a high resolution multiproxy chemostratigraphy study for the toarcian posidonia black shale from the dotternhausen section in sw germany in order to assess duration and seasonal fluctuation of photic zone anoxia based on the relative abundance of derivatives of chlorobiaceae lipids we assess the variability in the degree and persistence of photic zone anoxia using an aryl isoprenoid ratio air obtained by calculating the proportion of the short chain c13 17 versus the intermediate chain c18 22 aryl isoprenoids higher relative abundance of the short chain analogues is interpreted as indicating more intensive aerobic degradation of aryl isoprenoids air varies between values of 0 5 indicative of persistent pza phases and 3 0 for short termed episodic pza events absolute concentration of aryl isoprenoids is negatively correlated with the air which is in agreement with a progressive diagenetic breakdown of aryl isoprenoids the air decreases are validated using independent palecological and geochemical redox indicators for the posidonia shale in sw germany d 2004 elsevier b v all rights reserved

δ13c compositions of saturate and aromatic fractions of lacustrine oils and bitumens evidence for water column stratification abstract saturate fractions of oils and source rocks are generally depleted in 13 c relative to the aromatic fraction the isotopic difference between these two fractions aro sat is largest typically in lacustrine oils and bitumens and smallest in marine samples depletions of 13 c in saturate fractions in samples from three lacustrine basins china argentina and u s a correlate strongly with hopane abundance extremely 13 c depleted hopanes have been documented in ancient and modern lacustrine settings and are explained by input from methanotrophic bacteria as these bacteria thrive at the chemocline of stratified lakes extremely 13 c depleted hopanes in geologic samples is evidence for paleostratification comparatively low aro sat values in marine samples are related to abundant sulfate in marine environments since sulfate reducers out compete methanogens for metabolic intermediates and attenuate the methane cycle the strong positive correlation of quantitative hopane abundance with the 13 c depletion in saturate fractions of lacustrine samples provides circumstantial evidence for biogenic input from methanotrophic bacteria and for stratified water columns during source rock deposition further this observation explains why the sofer plot effectively differentiates stratified lacustrine samples from open marine and non stratified lacustrine samples the wide distribution of our sample set suggests that this is a global phenomenon

making loess sized quartz silt data from laboratory simulations and implications for sediment transport pathways and the formation of desert loess deposits associated with the sahara abstract results from a series of laboratory simulations designed to investigate quartz silt generation by a number of geomorphic mechanisms are reviewed these findings are then used to discuss potential sediment pathways involved in the formation of desert loess deposits and a pathway is presented to show a proposed sequence of events involved in the formation of the loess deposits associated with the sahara the results indicate that both fluvial and aeolian systems can be very effective at producing quartz silt it is suggested that fluvial systems within hot desert environments may play a central role in both the production and distribution of loessic silt first the highly energetic but periodic fluvial regimes associated with arid and semi arid environments may be responsible for considerable quantities of particle comminution second the intermittent nature of these systems will help maintain geomorphologically active surfaces from which silt sized material can be easily deflated as well as fluvial comminution a range of weathering mechanisms and aeolian abrasion may also be responsible for the generation of silts in desert loess consequently silt sources and mechanisms of silt generation are likely to be much more diverse for desert loess than those associated with glacial loess

organic geochemistry and petrography of lower cretaceous wealden black shales of the lower saxony basin the transition from lacustrine oil shales to gas shales abstract ninety seven wealden black shale samples from three wells in the lower saxony basin have been studied by organic geochemical and organic petrographical methods to determine their maturity organic facies and depositional environment the maturities of the three wells range from early mature ex a late to postmature ex c to overmature ex b as determined by vitrinite reflectance measurements diamondoid ratios and other geochemical maturity parameters ex c and ex b show distinct petrographic features related to oil generation and migration in particular the occurrence of dispersed solid bitumen replacing initial type i kerogen suggests a formerly active petroleum system structural and textural differences between early mature alginites and solid bitumen in postmature to overmature samples show an alteration of the pore system with increasing maturity a freshwater depositional environment is indicated by widespread occurrence of botryococcus algae and other small alginite particles predominating in the immature well these alginites are absent in the more mature gas shales of wells ex c and ex b geochemical evidence of algae and phytoplankton in general is provided by numerous biomarker parameters while the occurrence of carotane in some samples indicates events of increased salinity although no hypersaline conditions are inferred due to very low gammacerane indices increased amounts of vitrinite and inertinite in samples of ex b suggest locally significant terrigenous input of organic matter for some periods during wealden shale deposition high sulfur organic carbon ratios provide evidence for sulfate rich waters and partly anoxic bottom water conditions while the lower mature lacustrine source rocks generate paraffinic waxy oils gas and condensates are produced at post mature stages furthermore maturity distribution maps from 3d numerical petroleum systems modeling reveal substantial differences in respect to petroleum generation

photic zone euxinia in the central rhaetian sea prior the triassic jurassic boundary abstract shortly after the deposition of black shales in the rhaetian sea central european basin ceb the triassic jurassic tr j boundary witnessed one of the big five mass extinction events in earth s history aiming at a better understanding of paleoenvironmental changes in the geochemically less well known middle to late rhaetian german subdivision we studied samples from a cored borehole from the central rhaetian sea in nw germany hebelermeer 2 biomarkers palynomorphs and bulk geochemistry all support a marine brackish setting with inputs from terrestrial plants dinosteranes were found throughout the core most likely suggesting the spread of dinoflagellates it is widely accepted that volcanic exhalations during the development of the central atlantic magmatic province camp had a major impact on marine and terrestrial environments in the earliest jurassic e g the development of photic zone euxinia and h2s poisoning of benthic life there is evidence from the studied core however that comparable conditions already thrived in the central rhaetian sea during the middle rhaetian a first indication of euxinia anoxia is evident from low to very low total organic carbon versus total sulfur toc ts ratios

the effect of volcanic eruptions on the chemistry of surface waters the 1991 and 2000 eruptions of mt hekla iceland abstract the mt hekla eruptions in 1991 and 2000 have provided a unique opportunity to study the local environmental effects of high latitude volcanic eruptions in the middle of winter both eruptions started around sunset at sub zero temperatures in order to define better these effects we studied the chemistry of surface waters in the vicinity of the volcano additionally we describe and predict the environmental consequences of these volcanic eruptions on the chemistry of surface waters on land and in the ocean several dissolved elements in the polluted snow melt from the 2000 eruption cl f al fe mn as cd pb zn and u exceeded the limits for water intended for human consumption the volcanic ash the primary minerals and secondary mineral phases that commonly form in the weathering environment of iceland were undersaturated in the polluted snow melts with the exception of fluorite barite goethite and amorphous feooh these minerals can constrain the maximum initial concentration of the respective dissolved constituents in the meltwaters it took few days after the first rainfall on the volcanic ash to flush out the readily soluble constituents in the vicinity of the headwaters of the ytri ranga river the polluted river waters were oversaturated with respect to several secondary minerals resulting in precipitation of amorphous al hydroxide and feooh and further scavenging of some trace elements on the al and fe surfaces dissolved al and f were the main contaminants in the ytri ranga river water previous studies have shown that combined al f toxicity is directly related to the predominance of specific al f species in solution model calculations for mixing of a hekla type volcanic cloud with 4 surface water end members shows al f species to be most important in rain and dilute river waters this makes al and f phyto available but diminishes the concentration of the al 3 species the most toxic al species mixing with high alkalinity river waters or seawater results in the domination of non toxic al oh 4 species at dilutions greater than 800 thus hindering al toxicity and bioavailability this study indicates that h 2 so 4 contamination from volcanic eruptions is time and place dependent volcanic eruptions that take place during winter at high latitudes result in relatively high global sulfur contamination and relatively low local sulfur contamination due to the low oxidation rate of so 2 into h 2 so 4 because of the low solar radiation

surface area porosity and water adsorption properties of fine volcanic ash particles our understanding on how ash particles in volcanic plumes react with coexisting gases and aerosols is still rudimentary despite the importance of these reactions in influencing the chemistry and dynamics of a plume in this study six samples of fine ash 500 a all the specimens had similar pore size distributions with a small peak centered around 50 a these findings suggest that fine ash particles have relatively undifferentiated surface textures irrespective of the chemical composition and eruption type adsorption isotherms for water vapour revealed that the capacity of the ash samples for water adsorption is systematically larger than predicted from the nitrogen adsorption a s values enhanced reactivity of the ash surface towards water may result from i hydration of bulk ash constituents ii hydration of surface compounds and or iii hydroxylation of the surface of the ash the later mechanism may lead to irreversible retention of water based on these experiments we predict that volcanic ash is covered by a complete monolayer of water under ambient atmospheric conditions in addition capillary condensation within ash pores should allow for deposition of condensed water on to ash particles before water reaches saturation in the plume the total mass of water vapour retained by 1 g of fine ash at 0 95 relative water vapour pressure is calculated to be 10 2 g some volcanic implications of this study are discussed

effects of source thermal maturity and biodegradation on the distribution and isomerization of homohopanes in petroleum abstract the distributions of c31 c35 17 21 h homohopanes in marine petroleums can be used to describe redox conditions in the source rock depositional environment for example high c35 homohopane indices c35 c31 c35 are typical of petroleums generated from source rocks deposited under anoxic marine conditions where the c35 backbone of the precursor bacteriohopanetetrol is preferentially preserved homohopane distributions have been used to distinguish petroleums from different organic facies of the same source rock homohopane distributions are altered by secondary processes for example the c35 homohopane index decreases with increasing api gravity and thermal maturity of related oils from the monterey formation offshore california similar decreases in the homohopane index are observed for expelled oils from monterey source rock during hydrous pyrolysis biodegradation can result in selective loss of high or low molecular weight homologs apparently depending on the bacterial population in the reservoir bacterial demethylation of homohopanes appears necessary to explain 25 norhopanes in at least one biodegraded oil hydrous pyrolysis studies of the phosphatic and siliceous members in the monterey formation show that identical heating conditions result in different homohopane c 22 epimer ratios furthermore a reversal in the trend of the epimer ratio at high experimental temperatures is observed for the phosphatic but not for the siliceous lithology this could be caused by the combined effects of isomerization and differential thermal destruction of epimers at high temperatures possibly mediated by rock mineralogy

a possible terrigenous origin for perylene based on a sedimentary record of a pond lorraine france abstract the origin of perylene a five ring polycyclic aromatic hydrocarbon pah in sediments has been a matter of constant debate and its formation mechanisms remain unclear a perylene record in sediment was described and could support a clear link between perylene and terrigenous organic matter om input the distributions of pahs the variations of organic proxies such as the ratio of terrigenous to aquatic n alkanes tar hc and 5 h stanols 5 sterols ratio in sediments have been investigated sediments were sampled from a pond artificially created during the middle ages from a swampy area in the period prior to the pond creation for which high contributions of terrigenous om were evidenced perylene was found to be the predominant pah furthermore perylene content was shown to increase in response to the establishment of more reducing conditions this result supports the common idea that the main source of perylene is natural and derives from biogenic precursors under reducing conditions the creation of the pond in this wetland is marked by the deposition of a wood rich level characterized both by more oxygenated conditions and higher concentrations of perylene these high concentrations could result from the introduction of high concentrations of biogenic precursors of perylene under oxidative conditions subsequently the progressive burial of the woody level could have allowed the establishment of oxygen depleted conditions and the formation of perylene these results validate the use of perylene as a paleoenvironmental marker of terrigenous sources but it must be carefully used as a marker for syn or post depositional oxygen depleted conditions in lacustrine environments

fatty acid geochemistry of a 200 m sediment core from lake biwa japan early diagenesis and paleoenvironmental information abstract fatty acids fas and hydroxy acids dicarboxylic acids and n alkanes were studied in a 200 m sediment core taken from lake biwa japan fas showed bimodal distribution with peaks at c 16 and c 22 c 28 their distribution patterns clearly changed with depth from lower molecular weight c 12 c 19 predominance to higher molecular weight c 20 c 32 predominance in the upper 20 m interval analyses of related compounds and hydroxy acids and dicarboxylic acids suggest that and oxidative degradation of c 12 c 19 fas has occurred in the sediments the ratio of bound c 12 c 19 to unbound fas increases with depth in the upper 0 1 m sediments suggesting that unbound fas are more labile however the ratio varies significantly in deeper sections and may be associated with water temperature in the sediments deeper than 20 m in depth c 12 c 19 fas gradually decrease on the other hand higher molecular weight fas hfas c 20 c 32 which were probably derived from terrestrial plants increase in concentration from 20 m to 100 m suddenly decrease at 100 m and show progressively lower concentration in deeper sediments these fluctuations are interpreted in relation to paleolimnological changes of the lake and the drainage basin hydroxy c 20 c 30 acids and c 20 c 30 dicarboxylic acids show a distribution pattern similar to hfas branched chain fas hydroxy acids and c 9 c 19 dicarboxylic acids show a major peak around 3 15 m in depth this peak is probably caused by increased bacterial activity in the water column and surface sediments in the past which may be associated with an increase in primary production of the lake

geochemical and biological marker assessment of depositional environments using brazilian offshore oils abstract a combined geochemical and molecular characterization of a wide selection of oils from the major brazilian offshore basins has been undertaken the elemental sulphur nickel and vanadium and bulk oapi and 13c properties of each sample been considered together with its molecular composition determined using liquid and gas chromatography and quantitative biological marker investigations using gas chromatography mass spectrometry for alkanes the results reveal significant differences in the chemical features of the various oils which enable them to be divided into five groups the distinction of the groups appears to reflect differences in the depositional environment of the source rocks of the oils each group is correlated tentatively with source rocks laid down in a specific depositional regime namely lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate or marine deltaic the diagnostic features that allow this classification are the relative abundance and carbon number distributions of n alkanes pristane phytane ratios sulphur nickel and vanadium contents carbon isotope data the absolute concentrations of hopanes and steranes and their abundance relative to 4 methylsteranes and also the occurrence and abundance of several specific biological markers including 18 h oleanane gammacerane carotane tricyclic terpanes higher acyclic isoprenoids 28 30 bisnorhopane and 25 28 30 trisnorhopane this investigation shows the value of a combined geochemical and molecular approach in the assessment of the palaeoenvironment of deposition of the source rocks which gave rise to the oils

the dependence of dissolution rates on grain size for some fresh and weathered feldspars abstract ground samples from naturally weathered mineral fragments can still contain substantial proportions of weathered bet surface area if the freshly ground and naturally weathered surfaces in such samples have different dissolution rates data must be interpreted by a kinetic model in terms of both types of surface such a kinetic model is presented the model was used to reexamine literature data for ground size fractions from nine different naturally weathered feldspars ratios of dissolution reactive bet to measured bet surface area were analyzed as a function of the grain size both for the fresh and weathered surfaces in the samples for the naturally weathered surfaces the model strongly suggests that the ratio of reactive bet to measured bet surface area is either independent of the grain size or alternatively increases with decreasing grain size if so grinding does not destroy and possibly creates weathered reactive surface area relative to weathered surface area for the freshly ground surfaces the ratio of reactive bet to measured bet surface area was approximately directly proportional to the grain size thus grinding destroys fresh reactive surface area relative to fresh surface area at all grain sizes additional dissolution experiments on samples essentially containing fresh bet surfaces only have confirmed this finding in the literature ground samples from large naturally weathered fragments are frequently implied to contain fresh bet surface only observed dissolution rates can then be explained if dissolution rates per unit of fresh bet surface area are approximately independent of the grain size in fact however two partly counteracting processes appear to be active during grinding of naturally weathered mineral fragments these are 1 1 increase of the ratio of freshly ground bet to measured freshly ground plus naturally weathered bet surface area and 2 2 decrease of the dissolution rate per unit of fresh bet surface area these observations demonstrate that rate constants and dissolution rates when normalized to fresh bet surface are valid at one grain size only tentative calculations further suggest that dissolution rates normalized to dissolution reactive bet surface are approximately two orders of magnitude higher for fresh feldspar surfaces than for naturally weathered feldspar surfaces

structure kinematics and composition of fluid controlled brittle faults and veins in lower cretaceous claystones lower saxony basin northern germany constraints from petrographic studies microfabrics stable isotopes and biomarker analyses abstract investigation of fault rocks is crucial for the evaluation of sealing properties of rock formations considered as oil and gas storage or for the disposal of heat generating radioactive waste even in tight rock formations fluid flow may concentrate along brittle faults the present study focuses on the sealing properties of faulted lower cretaceous clay and siltstones encountered in drill cores from the central and eastern lower saxony basin germany our investigations are based on a multidisciplinary approach including microstructural mineralogical geochemical stable isotope and biomarker analyses the new data suggest that preexisting discontinuities and or sedimentary heterogeneities played a significant role for the increase in fluid pressure and formation of mode i veins within low permeability claystones high strain domains of fault cores consist of fine grained fault gouge a scaly fabric of varying deformation intensity is present around larger faults calcite precipitation in faults and complex mineralized veins and the differences in trace element concentrations of various veins reflect several phases of palaeofluid activity calcite precipitation in the fault rocks led to elevated amounts of mn ba and or sr isotope signatures indicate a local carbonate source for the origin of thin calcite coatings of fault planes but a more complex palaeofluid interaction for the larger faults and for complex veins consistent with the microfabrics biomarker signatures reveal the presence of mature hydrocarbons pointing to hydrocarbon migration in sections where steep only weakly mineralized faults occur the new results suggest that faulted claystones represent critical zones with a potentially reduced barrier capability consistent with published data

effects of chemical weathering and sorting on the petrogenesis of siliciclastic sediments with implications for provenance studies the bulk chemical compositions mineralogy and mineral proportions of sands and muds of the mallacoota basin in southeastern australia reflect the composition of weathering profiles mantling source rocks rather than bedrock muds contain abundant clay minerals that are virtually absent from the source rocks but abundant in the weathering profiles sands are strongly enriched in quartz relative to source rocks even in the headwaters of the fluvial system demonstrating that feldspar destruction occurs by in situ chemical weathering within profiles and before detritus enters the fluvial system k feldspar is proportionally more abundant in fluvial sands than in source rocks because plagioclase is more rapidly destroyed than either quartz or k feldspar in weathering profiles subsequent erosion and sorting produce sands enriched in quartz with high k feldspar plagioclase ratios relative to source rocks the composition of plagioclase incorporated into the fluvial sands is also controlled by chemical weat

environmental hazards of fluoride in volcanic ash a case study from ruapehu volcano new zealand abstract the vent hosted hydrothermal system of ruapehu volcano is normally covered by a c 10 million m3 acidic crater lake where volcanic gases accumulate through analysis of eruption observations granulometry mineralogy and chemistry of volcanic ash from the 1995 1996 ruapehu eruptions we report on the varying influences on environmental hazards associated with the deposits all measured parameters are more dependent on the eruptive style than on distance from the vent early phreatic and phreatomagmatic eruption phases from crater lakes similar to that on ruapehu are likely to contain the greatest concentrations of environmentally significant elements especially sulphur and fluoride these elements are contained within altered xenolithic material extracted from the hydrothermal system by steam explosions as well as in residue hydrothermal fluids adsorbed on to particle surfaces in particular total f in the ash may be enriched by a factor of 6 relative to original magmatic contents although immediately soluble f does not show such dramatic increases highly soluble naf and casif6 phases demonstrated to be the carriers of available f in purely magmatic eruptive systems are probably not dominant in the products of phreatomagmatic eruptions through hydrothermal systems instead slowly soluble compounds such as caf2 alf3 and ca5 po4 3f dominate fluoride in these phases is released over longer periods where only one third is leached in a single 24 h water extraction this implies that estimation of soluble f in such ashes based on a single leach leads to underestimation of the f impact especially of a potential longer term environmental hazard in addition a large proportion of the total f in the ash is apparently soluble in the digestive system of grazing animals in the ruapehu case this led to several thousand sheep deaths from fluorosis

pebble abrasion during fluvial transport experimental results and implications for the evolution of the sediment load along rivers 1 in actively eroding landscapes fluvial abrasion modifies the characteristics of the sediment carried by rivers and consequently has a direct impact on the ability of mountain rivers to erode their bedrock and on the characteristics and volume of the sediment exported from upland catchments in this experimental study we use a novel flume replicating hydrodynamic conditions prevailing in mountain rivers to investigate the role played by different controlling variables on pebble abrasion during fluvial transport lithology controls abrasion rates and processes with differences in abrasion rates exceeding two orders of magnitude attrition as well as breaking and splitting are efficient processes in reducing particle size mass loss by attrition increases with particle velocity but is weakly dependent on particle size fragment production is enhanced by the use of large particles high impact velocities and the presence of joints based on our experimental results we extrapolate a preliminary generic relationship between pebble attrition rate and transport stage c where fluvial shields stress and c critical shields stress for incipient pebble motion this relationship predicts that attrition rates are independent of transport stage for c 3 and increase linearly with transport stage beyond this value we evaluate the extent to which abrasion rates control downstream fining in several different natural settings a simplified model predicts that the most resistant lithologies control bed load flux and fining ratio and that the concavity of transport limited river profiles should rarely exceed 0 25 in the absence of deposition and sorting

lignin phenols in sediments of lake baikal siberia application to paleoenvironmental studies abstract sediments from three cores obtained from distinct depositional environments in lake baikal siberia were analyzed for organic carbon total nitrogen and lignin phenol concentration and composition results were used to examine changes in paleoenvironmental conditions during climatic cycles of the late quaternary c n ratios and organic carbon accumulation rates were significantly higher in the holocene compared with the late pleistocene reflecting overall warmer temperatures and increased runoff during the holocene a holocene maximum in organic carbon was observed at about 6 ka and may represent the warmest wettest period of the holocene at one site academician ridge pronounced late pleistocene maxima in organic carbon and biogenic silica were observed at about 80 85 ka probably indicative of an interstadial period with enhanced aquatic productivity total sedimentary lignin phenol contents were generally lower in the late pleistocene compared to the holocene but with several peaks in concentration during the late pleistocene these late pleistocene peaks in total sedimentary lignin content dated at about 80 50 and 30 ka directly precede or occur during peaks in sedimentary biogenic silica contents these periods likely represent relatively warm interstadial times with increased precipitation producing the observed increase in terrestrial runoff and aquatic productivity lignin phenol ratios s v c v and p v were used to examine changes in terrestrial vegetation type resulting from changes in paleoenvironmental conditions during the late pleistocene a degree of caution must be used in the interpretation of these ratios with regard to vegetation sources and paleoenvironmental conditions because of potential compositional changes in lignin resulting from biodegradation nevertheless results show that long glacial periods were characterized by terrestrial vegetation composed of a mix of non woody angiosperm vegetation and minor gymnosperm forest shorter interstadial periods are defined by a change to dominant gymnosperm forest and were observed at about 80 75 63 50 and 30 ka ranging from about 2 6 kyr in duration these interstadial periods of the late pleistocene defined by lignin phenol ratios generally occur during longer periods of enhanced sedimentary biogenic silica content about 10 15 ka in duration providing corroborative evidence of these warm interstadial periods

methylhopane biomarker hydrocarbons in hamersley province sediments provide evidence for neoarchean aerobiosis abstract bacteriohopanepolyols with a ring methyl substituents are bacterial lipid biomarkers that are presently known to originate from just a few specific taxa when preserved in ancient rocks the fossilized hydrocarbon skeletons of these molecules have the potential to provide biogeochemical records of those taxa and their respective physiologies considering both their occurrences in modern organisms and their proterozoic and phanerozoic sedimentary distributions hopanes carrying 2 methyl or 3 methyl substituents are proposed to be derived from cyanobacteria and oxygen respiring methanotrophs respectively here we report the distribution of methylhopanes in 2 72 2 56 billion year old neoarchean rocks from the hamersley province on the pilbara craton the relative abundance of c 31 3 methylhopane but not that of c 31 2 methylhopane shows a strong correlation to the carbon isotopic composition of co occurring kerogen insoluble particulate organic matter the unanticipated nature of this relationship provides evidence for a shallow water locus of carbon cycling through aerobic oxidation of ch 4 and coincidentally a means to demonstrate biomarker syngenicity 2 methylhopanes are most abundant in both shale and carbonate from shallow water sediments and a positive correlation to carbonate abundance contrasts to variable but generally lower 2 methylhopane abundances of deeper water facies these observations are consistent with their origin from cyanobacteria which were likely the cornerstone of microbial communities in shallow water ecosystems providing molecular oxygen fixed carbon and possibly fixed nitrogen

the origin and fate of 4 methyl steroids ii dehydration of stanols and occurrence of c30 4 methyl steranes abstract certain features of the distributions of sedimentary 4 methyl steroid hydrocarbons have been investigated i competitive dehydration experiments with stanols adsorbed on a shale suggests a possible explanation for the low abundance of 4 methyl sterenes relative to their desmethyl counterparts in immature sediments ii a 4 methyl spirostene which is a minor product of the backbone rearrangement of 4 methylcholest 4 ene in the laboratory has been tentatively assigned its presence in a toarcian black shale with a second isomer provides further evidence that the sedimentary backbone rearrangement of 4 methyl sterenes is analogous to that of their desmethyl counterparts and iii the major c30 4 methyl steranes in semecourt shale toarcian paris basin differ from those in an eocene lacustrine shale from china this indicates the potential complexity of c30 steroidal alkanes both 4 methyl and desmethyl which can occur in sedimentary organic matter and shows that care must be taken in using m z 217 mass chromatograms alone for routine input and maturity assessment using steroidal alkanes

biomarker paleo reconstruction of the german wealden berriasian early cretaceous in the lower saxony basin lsb during the early cretaceous berriasian wealden 3 4 northwestern germany was covered by an east west elongated tentatively brackish lake in which locally more than 700 m thick black shales were deposited while the distribution of organofacies in the basin is relatively well documented the paleoenvironmental conditions in the basin center e g occurrence and spread of water column stratification and the spatial record of biomarkers in wealden 3 4 shales and coals are rarely known we here present respective data from the entire basin in large areas total organic carbon toc contents are above 5 wt and hi values above 700 mg hydrocarbons hc g toc supporting the high potential of shales in the central basin as petroleum source rocks furthermore bulk geochemical data as well as biomarkers clearly mirror the wealden 3 4 facies distribution with the differentiation of a predominantly terrestrial setting east of the weser river and an aquatic and brackish lake setting in the west certain biomarkers such as isorenieratane specific for green sulfur bacteria indicate that the basin consisted of a permanently stratified water column with a brackish marine deep water body and an oxic anoxic transition zone in the photic zone in the southwestern gate of the lake including the isterberg area and towards the east no water column stratification developed characteristic of wealden 3 4 black shale organic matter are high relative abundances of saturated versus aromatic hydrocarbons most likely due to high botryococcus algal input highly negative 13c values in the extract fractions low isotopic canonical variables sensu sofer in aapg bull 68 31 49 1984 and high gammacerane dinosterane and c35 homohopane relative abundances interpreting those data the different sub facies of the environmental setting can be excellently documented particularly in the western part of the basin wealden 3 4 shales are important petroleum source rocks however an overlap of biomarker signatures with those from jurassic posidonienschiefer formation posidonia shales from the same area shows that oil source rock correlations in this area remain challenging

lignin and fatty acid records in lake baikal sediments over the last 130 kyr a comparison with pollen records abstract a 10 m sediment core from academician ridge in lake baikal was analyzed for its molecular composition using on line tmah tetramethylammomium hydroxide thermochemolysis major products are lignin phenols n c 14 to c 30 fatty acids alkanoic acids cutin acids hydroxy acids and aliphatic dicarboxylic acids lignin phenols are abundant in warmer periods the interglacial marine isotope stage mis 5e and mis 1 but extremely low in the other colder periods this result coincides well with pollen records reported for a core near the present site where an expansion of coniferous forests in sub stage 5e and mis 1 was implied normal c 24 c 30 alkanoic acids important components of plant wax esters are abundant in 5e and mis 1 and are present in significant amounts in the other colder periods unlike the lignin phenols a high abundance of n c 24 to c 30 alkanoic acids relative to lignin phenols in the bolling allerod warm period suggests an enhanced development of herbs it is implied from comparison of the sedimentary lignin phenol record with fossil pollen records and lignin phenol analysis of modern pollen that the ratio of cinnamyl phenols to vanillyl phenols may serve as an indicator of pollen contribution to sedimentary organic matter

molecular marker records of land use change abstract evidence of a changing environment in the catchment area of a small lake gormire yorkshire uk over the past 3000 years is provided by the mean carbon number of n alkanes and the ratio of lignin thermochemolysis products together with pollen analysis and bulk organic geochemistry periods of deforestation which commenced at 600 bc and ad 1200 display a significant decrease in organic carbon contents of the lake sediments which probably reflects dilution by enhanced influx of clastic material the mean carbon number of waxy c27 c31 n alkanes closely corresponds with the percentage of pollen derived from grass in the sediments a higher plant derived triterpenoid tentatively identified from its mass spectrum as 28 carboxyursen 12 enol appears exclusively in samples where tree and shrub derived pollen is dominant thermochemolysis of lignin confirms that there was a significant change in the nature of material deposited in the lake sediments from woody to grass dominated changes in both the sedimentary c n ratios and yields of lignin derived phenols suggest that deforestation events led to enhanced aquatic productivity initially through the development of reed swamp vegetation

volcanic ash leachate compositions and assessment of health and agricultural hazards from 2012 hydrothermal eruptions tongariro new zealand abstract after almost 80 years of quiescence the upper te maari vent on mt tongariro erupted suddenly at 2352 h nz time on 6 august 2012 the short lived hydrothermal eruption distributed a fine ash of minor volume 5 10 5 m 3 over 200 km from source the threat of further eruptions prompted an investigation of the possible health and agricultural impacts of any future eruptions from this volcano particularly since the most recent large scale ash falls in new zealand in 1995 1996 had generated significant agricultural problems including livestock deaths deposited ash was sampled between 5 and 200 km from the volcano as soon as possible after the eruption two sub lobes of ash were identified from different vent areas and displayed subtly different leaching properties the first was an initial small lobe directed nne likely formed from drifting low level clouds associated with the initial lateral explosive blast and surges the main fall lobe directed eastward was sourced from a short lived vertical plume that rose up to c 8 km ash from the initial fall lobe had higher concentrations of f and al in single step leaches as well as in the totals of three sequential extractions further the initial lobe showed a higher proportion of soluble f and al extracted in the first leach compared to totals a linear relationship between concentrations of al and f in single leaches from the 6 august eruption was highly significant pearson correlation coefficient r 0 987 for 1 20 leaching ratios and r 0 971 for 1 100 suggesting the presence of soluble alumino fluoride complexes alf x 3 x an even more significant 1 1 ratio is displayed for the largest concentration leached ions of ca and so 4 which correspond to the presence of crystalline gypsum throughout the newly excavated hydrothermal system although no fresh magma was erupted in this event a shallow intrusion prior to the hydrothermal explosion apparently provided significant contents of volcanic gas that was dissolved within the hydrothermal fluids and adhering to ejected particles this and the ubiquitous presence of gypsum dominated the soluble components of these ash deposits leading to a complex leaching profile the leaching study carried out here showed that agricultural and human health hazard assessment particularly of f and s is not straightforward particularly because f solubility may be complex and not well characterised by simple leaching studies in the case of s which is agriculturally important saturation effects are apparent using normal leaching protocols and also imply a need for modification of standard methods

characterization of peatified and coalified wood by tetramethylammonium hydroxide tmah thermochemolysis abstract seven samples of peatified and coalified wood varying in rank from peat to subbituminous coal have been analyzed using a new technique thermochemolysis with tetramethylammonium hydroxide tmah the preserved lignin in the coal undergoes thermochemolysis reactions when subjected to treatment with tmah at 300 c for 10 min yielding a series of methylated guaiacyl derivatives that originate from the cleavage of o 4 bonds from preserved lignin as rank increases from peat to subbituminous coal the yields of lignin derived monomers decreases and the ratio of methylated acids to methylated aldehydes increases systematically describing a general increase in the level of alteration of the lignin side chain this new technique of tmah thermochemolysis lends itself well to studies of structural changes that may occur in lignin as it is being altered during coalification data obtained in this study along with structural models proposed in the past have given insight to mechanistic changes that occur in the lignin biopolymer during early coalification we propose that the first reaction to occur is o 4 bond cleavage and subsequent re alkylation of the aromatic ring followed by demethylation of the methoxyl side chain functionalities to produce catechol like structures

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

the biogeochemistry of ellesmere lake u k i source correlation of leaf wax inputs to the sedimentary lipid record abstract analyses of the free lipid distributions from ellesmere lake sediments taken from two depths and comparison with leaf wax lipid distributions from six deciduous tree species around the lake were made in order to assess lipid sources close correlations of aliphatic lipid distributions in the carbon number range c 20 c 50 were seen c 28 and c 29 sterols were observed in both sediment and leaf waxes but c 27 sterols were only present in the sediments and were thus assigned a nonleaf wax source unsaturated steroidal ketones were observed both in the sediment and in certain leaf waxes and were assigned specific sources alkan 2 ones were not present in the leaf waxes but were present in the sediment samples with an almost identical distribution to the sediment n alkanes indicating a microbially mediated source c 20 c 30 n aldehydes which have not previously been widely reported in free lipid distributions of freshwater lacustrine sediments were prominent in the surface sediment and in the leaf waxes examined

the respiratory health hazard of tephra from the 2010 centennial eruption of merapi with implications for occupational mining of deposits ashfall into heavily populated areas during the october november 2010 eruption of merapi volcano indonesia created anxiety regarding the growing impacts to health as the eruption escalated and the hazard zone widened we made a preliminary assessment of the respiratory hazards to human health of the tephra deposits ashfall lahar and pdc surge from the eruption using a laboratory protocol specifically developed to study the toxic potential of volcanic ash particles twenty samples collected from a range of locations were analysed for health pertinent mineralogical parameters grain size crystalline silica content morphology surface area bulk chemistry and leachable elements and bio reactivity hydroxyl radical generation haemolytic potential oxidative capacity pro inflammatory response the grain size pertinent to respiratory health was variable ranging from 1 4 15 6 vol sub 4 m and 3 0 28 9 vol sub 10 m diameter material no fibre like particles were observed cristobalite was present in all samples ranging from 1 9 9 5 wt but surface reactivity and in vitro toxicity assays showed low reactivity for all samples tested the risk of direct exposure to ash from fallout was in any case low due to seasonal rains limiting its re suspension and the immediate and effective clean up of communities by local people who supplied the ash to the indonesian construction industry for use as aggregate however mining of the lahar and thick pdc deposits in the valleys draining the volcano is performed on a vast industrial scale which could result in high occupational exposure to thousands of sand miners at merapi during the dry seasons further study of the health hazard of the mined merapi deposits is warranted

palynofacies micropalaeontology and source rock evaluation of non marine jurassic cretaceous boundary deposits from northern germany implications for palaeoenvironment and hydrocarbon potential abstract the jurassic cretaceous boundary interval of northern germany is characterised by non marine deposits attributed to the purbeck and wealden facies these organic rich sediments were deposited under restricted brackish lacustrine conditions in a palaeogeographically isolated basin lower saxony basin rock eval and 13corg measurements were performed to characterise the composition and distribution of the organic matter to determine the kerogen type chemically and to define the quantity and maturity of the organic matter a strong correlation between the optical characteristics documented by the palynofacies analysis and the chemical kerogen analyses have led to a better understanding of the palaeoenvironment and the processes which caused the organic matter enrichment the samples studied from the basin center show a high petroleum generation potential their estimated maturity is close to the onset of oil generation total organic carbon toc concentrations of up to 18 have been measured hydrogen index values reach up to 1185 mg hc g toc the kerogen assemblages in two basinal successions are dominated by granular amorphous organic material aom dinoflagellate cysts and botryococcus algae in a more marginal succession continent derived debris phytoclasts pollen and spores is dominant the aom is interpreted to have originated either from phytoplankton probably dinoflagellate cysts and botryococcus or its bacterial archaeal degradation products formed under anoxic conditions toc rich samples which are dominated by these amorphous kerogens show the highest petroleum potential the aom therefore plays a key role for the petroleum generation the long term climatic and hydrological evolution of the lower saxony basin which is based on palynomorphs ostracods and benthic foraminifera is here interpreted by a five stage model fluctuations in the salinity of the water bodies are directly reflected by the ratio between different freshwater and brackish marine organisms as well dinoflagellate cyst diversity five different cyst morphogroups are used for palaeoenvironmental interpretations the deposition of toc rich beds in the german wealden can be best explained by both high primary productivity and the establishment of prolonged phases of bottom water anoxia in a brackish lacustrine depositional environment ecological conditions supporting enhanced productivity and preservation of the algal bacterial derived organic matter were most favourable during the mid late berriasian wealden 1 4

recognition of paleobiochemicals by a combined molecular sulfur and isotope geochemical approach study of organic matter in immature sediments from a messinian evaporitic basin shows that consideration of structures modes of occurrence and carbon isotopic compositions of free and sulfur bound carbon skeletons allow identification of biochemical precursors detailed information concerning biotic communities present during deposition of sediments can be retrieved in this way moreover unprecedented biochemicals were recognized these extend the horizon of biomarker geochemistry

the immediate environmental effects of tephra emission the earth s history is punctuated by large explosive eruptions that eject large quantities of magma and silicate rock fragments into the atmosphere these tephra particles can sometimes be dispersed across millions of square kilometres or even entire continents the interaction of tephra with or in receiving environments may induce an array of physical chemical and biological effects the consequences for affected systems and any dependent communities may be chronic and localised in the event of frequent small eruptions while larger and rarer events may have acute regional scale impacts it is therefore necessary to document the range of possible impacts that tephra may induce in receiving environments and any resulting effects in interconnected systems we collate results from many studies to offer a detailed multidisciplinary and interdisciplinary review of the immediate post eruptive effects of tephra emission into the atmosphere onto vegetation soil or ice snow surfaces and in aquatic systems we further consider the repercussions that may be induced in the weeks to years afterwards in the atmosphere tephra can influence cloud properties and air chemistry by acting as ice nuclei in or by offering sites for heterogeneous reactions respectively tephra on vegetation causes physical damage and sustained coverage may elicit longer term physiological responses tephra deposits on soils may alter their capacity to exchange gas water and heat with the atmosphere or may have a specific chemical effect such as nutrient input or acidification on sensitive soils tephra deposition onto snow or ice may affect ablation rates rivers and lakes may experience turbidity increases and changes in their morphology as a result of fallout and prolonged months or years erosion from the tephra covered catchment in the first weeks after deposition tephra leaching may affect river chemistry the abundance and speciation of phytoplankton populations in lakes may be altered by tephra induced changes in water chemistry or sediment water nutrient cycling in the oceans tephra deposition may fertilise fe limited waters with potential impacts on the global carbon cycle embracing the full complexity of environmental effects caused by tephra fall demands a renewed investigative effort drawing on interdisciplinary field and laboratory studies combined with consideration of the interconnectivity of induced impacts within and between different receiving environments

total shale oil inventory from an extended rock eval approach on non extracted and extracted source rocks from germany abstract rock eval pyrolysis data are used for assessments of the quality and maturity of potential hydrocarbon source rock but is also often applied among shale oil studies to estimate the so called total oil for oil in place oip calculations however for these approaches rock eval may underestimate total oil due to a carryover effect a bias which is particularly crucial for shale oil investigations in this study we examined the total oil of marine to lacustrine source rocks from german shale oil formations using data from rock eval combined with solvent extraction each source rock was analysed by rock eval both non extracted and extracted to obtain values for total oil s1whole rock s1extracted rock s2whole rock s2extracted rock comparison of these two data sets revealed that for the individual formations in average 17 23 of the s2 fraction is extractable herein termed s2 oil this s2 oil increases the total oil amount compared to the conventional free oil s1 by average factors of 2 2 3 6 for selected source rocks the molecular composition of the s2 oil was obtained by a specific approach rock eval analysis was terminated after s1 detection at 301 c samples were retrieved solvent extracted and analysed by gas chromatography depending on the type of organic matter and maturity the s2 oil contains significant amounts of higher boiling hydrocarbons such as n alkanes but also contributes to the unresolved complex mixture it is to date unclear how much of this s2 oil should be finally considered as technically mobilized shale oil

recent vegetation history from a swampy environment to a pond based on macromolecular organic matter lignin and fatty acids and pollen sedimentary records evidence of environmental and vegetation changes in the catchment area of a small pond created artificially during the middle ages from a swampy area was provided by coupling palynology data and a detailed study of macromolecular organic matter om tetramethylammonium hydroxide tmah thermochemolysis after solvent extraction was used to characterize macromolecular om and particularly lignin and fatty acids fas molecular ratios such as tar fa c 16 1 c16 0 and c 18 1 c 18 0 were calculated to characterize the fas incorporated into the macromolecular om moreover syringyl vs vanillyl phenols s v and cinnamyl vs vanillyl phenols c v molecular ratios were investigated to fingerprint the lignin sources these different markers suggested that the swampy area was dominated by a non woody angiosperm input and gave rise to pond status over a period of several centuries indeed tar fa correlated with the aquatic contribution which became predominant after creation of the pond the use of ratios of total acid phenols to the total aldehyde phenols of syringyl or vanillyl units ad al s ad al v which are related to the degree of oxidation of lignin revealed the irregular operation of oxidative conditions

sources of sedimentary organic matter in the mississippi river and adjacent gulf of mexico as revealed by lipid biomarker and δ13ctoc analyses abstract changes in the organic matter om composition c n 13 c toc and lipid biomarker compounds of surface sediments 0 1 cm were examined along the dispersal pathway from mississippi river and marsh estuarine end members to the adjacent shelf and canyon regions of the gulf of mexico organic carbon content decreased fourfold from the marsh to the offshore sites with corresponding changes in organic matter sources biomarkers representing allochthonous higher plant and autochthonous algal plankton bacteria sources demonstrated regional differences in the sources of sediment organic matter som a two end member mixing model using 13 c toc indicated that c 3 vascular plant sources comprised 80 and 50 of the toc at the river and marsh sites respectively however sources of som differed in these regions with contributions of soil organic matter terrigenous plant sources dominant in the river 13 c toc 25 while marsh plants likely contributed to the enriched signatures found in the marsh sediments 13 c toc 18 allochthonous om contributions calculated from fatty acid and sterol biomarkers in the river and marsh regions 39 48 and 50 72 respectively differed from those determined using 13 c toc this was likely due to overlapping 13 c toc values for vascular plants and freshwater microalgae and the higher lipid content of the autochthonous sources although biomarkers representing terrigenous sources decreased with distance offshore they comprised approximately 17 34 of the fatty acid and sterols at even the most distal slope and canyon sites suggesting that these deeper regions could be an important sink for terrigenous carbon in contrast the shelf sites were enriched in algal material 60 78 autochthonous oc with biomarkers for diatoms dominating suggesting that terrigenous carbon is either diluted in or bypasses this region results from this study suggest that processes including hydrodynamic sorting diagenesis and variations in river flow should be considered in future studies investigating the fate of terrigenous om in coastal and shelf regions

perils in distinguishing phreatic from phreatomagmatic ash insights into the eruption mechanisms of the 6 august 2012 mt tongariro eruption new zealand abstract the weak geophysical precursors of the 6 august 2012 te maari eruption of mt tongariro and a lack of obvious juvenile components in its proximal ballistic deposits imply that the eruption was caused by the sudden decompression of a sealed hot hydrothermal system strong magmatic signals in pre and post eruption gas emissions indicate that fresh magma had intruded to shallow levels shortly before this eruption here we examine the volcanic ash produced during the august eruption with the aim of determining whether juvenile magma was erupted or not the widely applied criteria for identifying fresh juvenile pyroclasts provided inconclusive results the te maari ash sorting and trend towards a unimodal grain size distribution increase with distance along the dispersal axis proximal to intermediate sites showing polymodal grain size distributions can be related to the re fragmentation of different pre existing lithologies overlapped erupted pulses and transport mechanisms and to particle aggregation between 69 and 100 vol of particles coarser than 3 and 45 75 vol of grains finer than 3 were sourced from the pre existing commonly hydrothermally altered vent area lavas and pyroclasts free crystals pyroxene plagioclase magnetite pyrite make up 0 23 vol of particles coarser than 3 and 22 41 vol of grains finer than 3 brown to black fragments of fresh glass are a small 1 15 vol but notable component under sem these blocky glassy particles are poorly vesicular and irregularly shaped some with fluidal or bubble wall surfaces and others with fragmented stepped surfaces and fine adhering ash in thin section they contain variable amounts of microlites within an isotropic groundmass the range in silica content of the microprobe analysed glass is very wide 56 77 wt and cannot be correlated to any specific particle textural type these chemically and texturally diverse glassy fragments are identical to mechanically broken pieces of country rock lavas and pyroclasts both their diversity and their match with vent country rocks argue strongly against a juvenile origin for the glassy fragments we conclude that rising magma provided only heat and gas into the overlying sealed vapour dominated hydrothermal system a landslide from this area led to a rapid decompression and ash was produced by top down hydrothermal explosions careful attention must be paid to the combination of compositions and textures of fine ash particles in such situations as well as to the context of their source vent in order to be confident that new magma has reached the surface

geolipid pollen and diaton stratigraphy in postglacial lacustrine sediments as part of our continuing investigation of specific compounds as organic matter indicators in lake bottoms we have examined geolipids pollen and diatoms in sediments from different periods in the postglacial history of heart lake new york sediment core sections representing the major watershed vegetation periods were extracted for unbound and bound fatty acids hydrocarbons and alcohols fatty acids constitute most of the extracted material minor decreases in unsaturated acids with depth indicate little degradation of organic matter in these sediments the dominant unbound n alkanoic acid in the core sections is either cz2 or c24 but bound fractions contain few long chain acids and are dominated by n cry nearly all the hydrocarbons are found in the unbound fraction the ratio of c2 c 7 n alkanes increases from the bottom of the core to near the top as watershed forests have matured and lake productivity has diminished but drops since european settlement of the region organic degradation in this lake bottom is mild and input indicators appear to be well preserved

variability of early diagenesis in lake sediments evidence from the sedimentary geolipid record in an isolated tarn abstract a 0 5 m long core of sediment from coburn mountain pond maine u s a has provided a virtually undisturbed and continuous record of sediment deposition for the last 200 yr in this small essentially pristine tarn organic carbon concentrations c n ratios carbon isotopic compositions and extractable hydrocarbon molecular compositions indicate subtle differences in the sources of organic matter between sediments deposited before and after ca 1950 but are otherwise constant in contrast total concentrations and molecular distributions of n fatty acids and n alkanols vary considerably the fatty acid and alkanol geolipid fractions are both sensitive to early diagenetic alteration yet the two fractions react differently concentrations and compositional parameters such as long short even odd and branched unbranched ratios fluctuate with sediment depth and reflect amounts of microbial reworking which have varied repeatedly over the depositional history n alkane distributions are relatively unaffected by the short term changes and therefore better preserve the history of biolipid sources to the sediments

biomarkers in sedimentary sequences indicators to track sediment sources over decadal timescales abstract long term sedimentary sequence research can reveal how human activities and climate interact to affect catchment vegetation flooding soil erosion and sediment sources in this study a biomarker sediment fingerprinting technique based on n alkanes was used to identify long timescale decadal sediment sources in a small agricultural catchment however the highly saline carbonate environment and bacterial and algal activities elevated the levels of even chain n alkanes in the sediments leading to an obvious even over odd predominance of short and middle components c 15 c 26 therefore by analyzing three odd long chain n alkanes c 27 c 29 and c 31 in 27 source samples from cropland gully and steep slope areas and one sediment sequence one cultivated horizon and 47 flood couplets a composite fingerprinting method and genetic algorithm optimization were applied to find the optimal source contributions to sediments the biomarker fingerprinting results demonstrated that the primary sediment source is gullies followed by cropland and steep slope areas the average median source contributions associated with 47 flood couples collected from sediment core samples ranged from 0 0 1 to 91 9 0 4 with an average of 45 0 for gullies 0 0 4 to 95 6 1 6 with an average of 38 2 for cropland and 0 2 1 to 60 7 0 4 with an average of 16 8 for steep slopes however because farmers were highly motivated to manage the cropland after the 1980s over half the sediments were derived from cropland in the 1980s biomarkers have significant advantages in the identification of sediments derived from different landscape units e g gully and steep slope areas and n alkanes have considerable potential in high resolution research of environmental change based on soil erosion in the hilly loess plateau region

biogenic silica storage in soils the role of plants in soil development has become of crucial interest in quantifying global weathering processes on the volcanic reunion island indian ocean a 15 cm thick phytolith rich horizon biogenic opal a developed at the expense of trachytic ashes between 3820 85 and 335 90 yr b p then 97 138 t km 2 yr of sio 2 were biogeochemically recycled from the weathering of parent rocks through a past forest of bamboos nastus borbonicus this rate is in the same range as the present chemical weathering rates of silica in the area considered to be among the highest in the world these results demonstrate that the storage of biogenic silica in soils may be significant and may retard the output of silica to rivers and ocean

molecular evidence for recent land use change from a swampy environment to a pond lorraine france evidence of a changing environment in the catchment area of a small pond lansquenet lorraine france during the last millennium was provided by coupling palynology data and organic ratios terrestrial to aquatic ratio tar hc the c29 vs c27 sterols c29 c27 st average chain length acl and aquatic macrophytes ratio paq the depositional and alteration conditions of organic matter om were provided by the 5 h stanols 5 sterols ratio this study shows that quite simple organic ratios clearly allow identification of the different evolution steps of a watershed from a swamp to the progressive settlement of a pond during the swampy period the c n at ca 11 1 tar hc ca 36 8 c29 c27 st ca 8 7 and paq 0 3 show a high contribution of allochthonous om associated with the presence of particular aquatic and mesohygrophilous species a woody level dated to the xiiith century reflects the period of the settlement of the pond in a more oxic environment 5 h stanol 5sterol ratio 0 2 then the progressive increase in aquatic input and the development of submerged and floating macrophytes are evidenced by low c n at 7 6 tar hc ca 2 7 c29 c27 st ca 2 and high paq ca 0 5 suggesting an increase in the water level and eutrophication of the pond a second oxic event 5 h stanols 5sterols ratio averaging 0 16 associated with extensive om degradation corresponds to the most recent dredging in 2002 and reflects an important disturbance of sediments due to pond management

organic matter and lipids in sediments of lake bled nw slovenia source and effect of anoxic and oxic depositional regimes sources of organic matter om and lipids were assessed and factors affecting om degradation were studied for two sediment cores representing distinct depositional regimes i e the oscillating oxic to suboxic anoxic western basin and oxic zaka bay for eutrophic lake bled nw slovenia lower surface organic carbon oc concentration was determined in the western basin than for zaka bay sediments 5 1 vs 5 4 wt dry sediment respectively but one order of magnitude greater total lipid concentration was observed in the former also there was a higher proportion of autochthonous om in the western basin 77 vs 66 on the basis of atomic c n ratios lipid based origin assessment suggested a similar contribution of autochthonous om in the western basin 64 77 but a lower one in zaka bay 50 it seems that redox potential is the main factor governing om degradation in the western basin in contrast a contribution from more refractory terrestrial om via the surface inflow in zaka bay and higher sedimentation rates may surpass redox effects in zaka bay overall oxygen may play a more important role in degradation of the more labile pool i e lipids than bulk om higher apparent degradation rate constants k for lipids also suggested a greater lability than for oc while respective k values were higher in the oxic than anoxic environment

molecular indicators of palaeoenvironmental conditions in an immature permian shale kupferschiefer lower rhine basin north west germany from free and s bound lipids a study of the distributions of free and s bound biomarkers and their 13c values in the extract of a bulk sample of the permian kupferschiefer from the lower rhine basin has been carried out to provide a more detailed characterization of the biological inputs the distributions and isotopic compositions of selected components released from nickel boride desulphurization have been compared with those of components in the free fraction the free biomarkers occur in greater abundance than their s bound counterparts the distribution and carbon isotopic composition of both free and bound components in the extract indicate a major cyanobacterial and algal input likewise the free and bound aromatic hydrocarbons contain components which reveal an origin from the carotenoids of chlorobiaceae green sulphur bacteria providing molecular evidence for the occurrence of photic zone anoxia in the water column most of the components in the complex mixture of mono di tri and tetra aromatics in the free aromatic hydrocarbon fraction result from cyclization and aromatization reactions

age and origin of the well preserved organic matter in internal sediments from the silesian cracow lead zinc deposits southern poland the molecular and petrographic characteristics of organic matter in internal sediments from the mississippi valley type lead zinc deposits in southern poland reveal immature and well preserved organic matter huminite reflectance values of organic matter in all internal sediments are low with a mean value of 0 29 corresponding to a lignite range of coalification most organic compounds in the organic matter e g cadalene retene simonellite perylene and sitosterol and its transformation products stigmastanol and stigmasta 3 5 dien one as well as lignin degradation compound products e g benzoic acid vanillin 4 benzaldehyde benzenedicarboxilic acids and hydroxybenzoic acids are of terrestrial origin monosaccharides with dominant and glucose were identified as possible remnants of cellulose degradation products suggesting an excellent state of organic matter preservation given that monosaccharides are preserved only under conditions of limited oxygen after sedimentation resulting from the rapid accumulation of internal sediments in meteoric paleokarst cavities followed by insignificant diagenesis petrologic and palynological data on internal sediments clearly indicate a middle triassic age for organic matter and for the development of a triassic meteoric karst system immediately after anisian carbonate sedimentation

mechanisms of loess sized quartz silt production and their relative effectiveness laboratory simulations the production of loess sized quartz silt is frequently ascribed to glacial grinding mechanisms in this study a series of laboratory simulations was set up the purpose of which was to demonstrate that a range of geomorphic mechanisms are capable of producing silt under laboratory conditions the geomorphic mechanisms investigated were aeolian abrasion fluvial comminution glacial grinding salt weathering and frost weathering the results confirmed that under laboratory conditions all of these mechanisms were capable of producing silt the relative effectiveness of these mechanisms at producing silt under laboratory conditions was then calculated in order to provide a starting point for a consideration of their potential effectiveness within the natural environment these results indicate that fluvial and aeolian activity are highly effective at producing quartz silt over short time periods in a dust storm of four days duration 287 g of silt could potentially be produced from every kilogram of sand entrained while fluvial comminution in a turbulent fluvial environment could potentially produce 900 g of silt from every kilogram of sand entrained within 32 h over longer periods of time the glacial grinding and weathering mechanisms represent more continuous and hence more effective silt producing mechanisms although it is realised that the relative importance of each silt producing mechanism will differ spatially and temporally due to differences in climate relief geology and geomorphic history the findings from this work do have implications for the genesis of loess deposits they demonstrate that glacial and cold weathering processes are not solely responsible for fine particle formation and that efficient silt producing mechanisms can operate within a variety of environments under suitable conditions weathering together with episodic contributions from aeolian and fluvial mechanisms could be responsible for a considerable proportion of global quartz silt production

relationship of biomarker distribution to depositional environment phosphoria formation montana u s a from biomarker distributions it is possible to distinguish extracts from four different members facies meade peak rex retort and tosi of the permian phosphoria formation at little sheep creek montana these distributions relfect changes in floral and faunal distribution in response to a changing depositional environment and suggest that the retort and tosi members the second cycle of deposition were deposited under more anoxic conditions and at higher salinity than meade peak and rex members the first cycle correlations between biomarker indicators of anoxia and salinity suggest that anoxia was in part the result of a chemocline separating normal marine waters above from more saline bottom waters anoxia and salinity in the bottom waters increased with time making conditions in the basin progressively more hostile to benthic organisms development of extreme environmental conditions in continental shelf habitats such as those suggested by biomarker parameters at little sheep creek may have compounded spatial problems created by continental suturing suggested to be a cause of permian extinctions factor analysis indicates that four factors for 75 3 of the variance in biomarker ratios these factors are suggested to be source organisms types of eukaryotic plankton salinity eh and mineralogy the grandeur member of the phosphoria which is a typical reservoir rock for phosphoria derived oils yields an extract containing a novel c30 nitrogen containing steroid this unique steroid is not abundant in any other known extracts or oils which along with the extremely low porphyrin maturity parameter of all the extracts pmp 0 01 confirms the absence of migrated oils in the phosphoria at little sheep creek the biomarker ratios c29 ga a steranes ts ts tm triaromatic triaromatic monoaromatic steroids short long short chain monoaromatic steroids and short long short chain triaromatic steroids are commonly used to determine the thermal maturity of oils and source rock extracts however these ratios show considerable variation in core extracts of the same thermal maturity from different facies in contrast the thermal maturity parameters c29 20s 20s 20r steranes and porphyrin maturity parameter pmp show little variation indicating that these parameters are less affected by changes in depositional environment and may be most useful for thermal maturation determinations of phosphoria related oils and source rocks this study supports previous work suggesting environmental effects must be considered if correct determination of thermal maturity of an oil or extract is to be made this is especially true of oils and extracts from source rocks with high sulfur concentrations and or those deposited at elevated salinities

stable carbon isotope compositions of crude oils application to source depositional environments and petroleum alteration the carbon isotopic composition of the c15 saturate and aromatic hydrocarbon fractions and the gas chromatographs of the c15 saturate fraction of 339 oils were geochemically and statistically evaluated results of this study show that the average isotopic compositions of the c15 aromatic hydrocarbon fractions of oils sourced from terrigenous or marine organic matter are identical the average isotopic composition of the c15 saturate fraction of oils derived from terrigenous organic sources is slightly more negative 0 9 pmil than the average for marine oils but this difference is insufficient to be used as a reliable source indicator reports in the literature stating that marine oils are isotopically more positive than te rigenous oils and that the difference can be utilized to distinguish between the two are therefore not supported by this study the isotopic differences between oils sourced from terrigenous and marine organic matter do not manifest themselves in the range of absolute values of one oil fraction but rather in the isotopic relationship between the saturate and aromatic hydrocarbon fractions the isotopic relationship is the following oils of terrigenous organic source dgr13caro 1 12 dgr13csat 5 45 oils of marine organic source dgr13caro 1 10 dgr13csat 3 75 the difference between the two equations was evaluated statistically and a statistical parameter cv the canonical variable cv 2 53 dgr13csat 2 22 dgr13caro 11 65 was used to distinguish between marine and terrigenous oils cv values larger than 0 47 indicate predominantly a terrigenous organic source for the oil whereas cv values smaller than 0 47 indicate mostly a marine organic source thermal maturity differences in oils and isotopic variations in the source beds can cause as much as 2 pmil variations in the isotopic composition of one family of oils finally stable carbon isotopes can in some situations help correlate biodegraded oils to their nondegraded counterparts

the origin of closed depressions in northeastern france a new assessment over 10 000 closed depressions cds are found in the silty plains of northeastern france these small wetlands support the growth of rare plant species although their origins which could be anthropogenic or geologic due to salt gypsum lens dissolution have been debated for 150 years they have not yet been the focus of an integrated study in 39 geological borings along a 15 km strip no salt gypsum lenses and more than 260 cds were recorded using lidar all of the investigated cds have a bathtub form with a flat bottom complete excavations clearly showed a cut contact between the sediment and the horizontal marl substratum at the bottom and a cut at the edges of the upper marl layers radiocarbon dating of sediment bottoms showed that sedimentation began between the second iron age and the roman period the frequencies of pollen and sporormiella type depict an open landscape with grassland pasture and cropland these convergent findings challenge the hypothesis that cds formed naturally and suggest that they area instead anthropogenic because no soil deposits were found around the cds digging may have been intended to marl the surrounding acidic silty soils the high density and small size of cds will allow the detailed reconstruction of landscape and biodiversity modifications in the region for the two last millennia

organic geochemistry of recent marine sediments from the nansha sea china recent marine sediments from two cores collected on the continental slope of the nansha sea china have been analyzed for organic matter content n alkane and isoprenoid hydrocarbons fatty acids n alkanols and sterols the organic carbon contents of the two sediment cores average 0 7 and 0 53 respectively and are higher than those of other sedimentary environments in this region the distributions of various lipid compounds indicate that most of the sedimentary organic matter in the two cores is derived from marine plankton and bacteria with land derived organic matter present in relatively small amounts the decrease in relative abundances of shorter chain lipids n alkanes n fatty acids and n alkanols with depth is evident as is the biochemical conversion of stenols to stanols in some samples the low pristane phytane ratios may result primarily from microbial activity and reflect the occurrence of significant diagenetic alteration of organic matter in the two cores

leachability of uranium and other elements from freshly erupted volcanic ash abstract a study of leaching of freshly erupted basaltic and dacitic air fall ash and bomb fragment samples unaffected by rain shows that glass dissolution is the dominant process by which uranium is initially mobilized from air fall volcanic ash si li and v are also preferentially mobilized by glass dissolution gaseous transfer followed by fixation of soluble uranium species on volcanic ash particles is not an important process affecting uranium mobility gaseous transfer however may be important in forming water soluble phases adsorbed to ash surfaces enriched in the economically and environmentally important elements zn cu cd pb b f and ba quick removal of these adsorbed elements by the first exposure of freshly erupted ash to rain and surface water may pose short term hazards to certain forms of aquatic and terrestrial life such rapid release of material may also represent the first step in transportation of economically important elements to environments favorable for precipitation into deposits of commercial interest ash samples collected from the active guatemalan volcanoes fuego and pacaya high al basalts and santiaguito hornblende hypersthene dacite bomb fragments from augustine volcano andesite dacite alaska and heimaey basalt vestmann islands iceland and fragments of rhyolitic pumice from various historic eruptions were subjected to three successive leaches with a constant water to ash weight ratio of 4 1 the volcanic material was successively leached by 1 distilled deionized water ph 5 0 5 5 at room temperature for 24 h which removes water soluble gases and salts adsorbed on ash surfaces during eruption 2 dilute hcl solution ph 3 5 4 0 at room temperature for 24 h which continues the attack initiated by the water and also attacks acid soluble sulfides and oxides 3 a solution 0 05 m in both na co and nahco ph 9 9 at 80 c for one week which preferentially dissolves volcanic glass the first two leaches mimic interaction of ash with rain produced in the vicinity of an active eruption the third leach accelerates the effect of prolonged contact of volcanic ash with alkaline ground water present during ash diagenesis

lacustrine responses to tephra deposition examples from mexico one of the major problems with palaeoclimate investigations in volcanic regions is that tephra inputs to lakes can cause changes in proxies analogous to those of climate forcing we review the range of impacts thought to be associated with tephra deposition distinguishing between direct effects on lake ecosystems and indirect changes to catchment nutrient cycles to achieve better understanding of these complex responses we have used high resolution diatom analysis from around 17 tephra layers in three mexican lakes a positive response to the tephra inputs has been identified for over half of these layers the most common response was for diatom concentrations to increase after tephra deposition also in plankton dominated systems fragilaria spp replaced stephanodiscus spp and aulacoseira spp an increase in the supply of silica to the lakes through their catchments is probably the cause of the diatom changes in the lakes studied direct effects of the tephra inputs to these lakes can be excluded as they would not generate changes of sufficient longevity the impact of these tephras which lasted for several decades was insufficient to perturb the underlying long term climate forcing of these lake systems c 2004 elsevier ltd all rights reserved