weak monsoon event at 4 2 ka recorded in sediment from lake rara himalayas abstract the strength of the indian summer monsoon varied significantly on centennial to millennial timescales during the holocene among these variations a weak summer monsoon event occurred approximately at 4 ka the so called 4 2 ka event this event is considered to have been a relatively sustained and widespread phenomenon at regional scales across southern asia to eastern africa however little is known about the impact of such variations in the himalayas a key location for understanding the monsoon system here we present a record of changes in summer monsoon strength during the holocene from lake rara western nepal using redox sensitive elements mn ti and mn fe measured by x ray fluorescence xrf core scanner in addition organic matter properties toc 13c and c n and changes in the 14c age offset between bulk organic matter and leaf matter namely the old carbon offset are used to augment the environmental reconstruction collectively the data indicate a period of prolonged weak monsoon interval at around 4 ka the timing of onset and recovery from the event observed at lake rara exhibits particular similarity with changes in the indus river discharge this is the first record of the 4 2 ka event from the himalayas based on a relatively well constructed age model using 14c dates that are not influenced by reservoir effects these findings provide an important step towards better understanding the spatial and temporal variability in the holocene indian monsoon

monitoring of active but quiescent volcanoes using light hydrocarbon distribution in volcanic gases the results of 4 years of discontinuous monitoring in the campi flegrei italy abstract during the period from january 1991 to january 1994 the 10 yr geochemical monitoring in the campi flegrei southern italy usually performed using the inorganic gas fraction was implemented by discontinuous monitoring of the hydrocarbon gas fraction the measured compositions have revealed the presence of significant amounts of at least 11 hydrocarbon species related to alkane alkene and aromatic classes thermodynamic calculations showed the possible existence of partially independent equilibria within the c1 c2 c3 and c1 c2 c3 c4 alkane systems as well as among alkene alkane pairs at redox conditions controlled by the geothermal feo fe1 5o redox buffer system at temperatures between 200 and 400 c and ph2o controlled by the presence of a saline brine unlike the constancy of the measured and calculated inorganic temperature equilibrium temperature based on organic species has displayed fluctuations and a significant increase starting from the second half of 1993 according to their apparent correlation with other independent observations such as the measured increases of vapor fraction h2s co2 and h2 n2 ratios on the monitored fumarole in addition to a general increase of dissolved co2 in the campi flegrei groundwaters the observed variations of the organic parameters were interpreted as the result of a general increase in acid bearing gas flux throughout the re equilibration zone

genesis and evolution of the fumaroles of vulcano aeolian islands italy a geochemical model a geochemical model explaining the presence of fumaroles having different gas composition and temperature at the top of the crater and along the northeastern coast of vulcano island is proposed a pressurized biphase liquid vapor reservoir at the depth of about 2 km is hypothesized energy and mass balance sheets controlp t conditions in the system p t must vary along a boiling curve of brine as liquid is present the co2 content in the steam is governed by the thermodynamic properties of the fluids in the h2 nacl co2 system on the assumption that oxygen fugacity in the system is between the hm fmq oxygen buffers observed so2 h2s co2 co co ch4 ratios in the fumarolic gases at the fossa crater appear in equilibrium with a temperature higher than that observed such as may exist at depth the more reduced gas phases present on the sea side may result from re equilibrium processes in shallower aquifers the suggested model would help in monitoring changes in volcanic activity by analyzing fumarolic gases

atmospheric radiocarbon calibration to 45 000 yr b p late glacial fluctuations and cosmogenic isotope production more than 250 carbon 14 accelerator mass spectrometry dates of terrestrial macrofossils from annually laminated sediments from lake suigetsu japan provide a first atmospheric calibration for almost the total range of the radiocarbon method 45 000 years before the present the results confirm the recently revised floating german pine chronology and are consistent with data from european and marine varved sediments and combined uranium thorium and carbon 14 dating of corals up to the last glacial maximum the data during the glacial show large fluctuations in the atmospheric carbon 14 content related to changes in global environment and in cosmogenic isotope production

marked decline in atmospheric carbon dioxide concentrations during the paleogene the relation between the partial pressure of atmospheric carbon dioxide pco2 and paleogene climate is poorly resolved we used stable carbon isotopic values of di unsaturated alkenones extracted from deep sea cores to reconstruct pco2 from the middle eocene to the late oligocene approximately 45 to 25 million years ago our results demonstrate that pco2 ranged between 1000 to 1500 parts per million by volume in the middle to late eocene then decreased in several steps during the oligocene and reached modern levels by the latest oligocene the fall in pco2 likely allowed for a critical expansion of ice sheets on antarctica and promoted conditions that forced the onset of terrestrial c4 photosynthesis

water and gas geochemistry of the euganean and berician thermal district italy between 1987 and 1995 more than 100 chemical and isotopic analyses were carried out on the thermal fluids discharged at surface from wells and springs of the euganean and berician thermal district results for dd and d 18 o in waters d 13 ci n co2 and in c1 c4 n alkanes d di n ch4 3 he 4 he and 40 ar 36 ar ratios in natural gases were coupled with chemical analyses in an attempt to determine the main characteristics and evolutionary trends of thermal fluids emerging in the region the isotopic and chemical composition of thermal waters has led to the postulation of a meteoric origin of discharged thermal fluids and of a maturation trend as water moves from the peripheral manifestations of the berici hills towards those of the battaglia montegrotto and abano springs in the inner part of the geothermal field numerical simulation suggested that the observed evolutionary path is consistent with diaerentiation due to processes of water rock interaction the results of bulk analyses have shown that the gases are made up mainly of n2 65 95 vol co2 0 5 20 5 vol and ch4 up to 10 vol with relatively high ar and he contents up to 1 5 vol and 0 16 vol respectively and detectable amounts of c2 c6 saturated hydrocarbons the chemical and isotopic composition of the gases suggests that both the meteoric and crustal contributions to the natural discharges are significant while any significant magmatic contribution possibly related to vestiges of the volcanic activity that occurred in the abano area during the tertiary age can be ruled out 2000 elsevier science ltd all rights reserved

the hydrothermal volcanic system of rincon de la vieja volcano costa rica a combined inorganic and organic geochemical approach to understanding the origin of the fluid discharges and its possible application to volcanic surveillance abstract in the period 1998 2002 thermal spring discharges of rincon de la vieja volcano nw costa rica have been sampled and analyzed for major trace and isotopic 18 o 16 o and d h in waters and 3 he 4 he and 13 c 12 c in co 2 in gases composition the boiling pools hosted inside the summit crater active crater are characterized by high contents of magmatic related compounds so 2 hcl and hf that strongly affect the chemistry of the crater lake these chemical features are not shown by the thermal discharges seeping out in the surrounding area of the volcano here the shallow aquifer apparently masks any possible clues related to the magmatic system this suggests that the fluid vents located inside the active crater are likely to represent the most appropriate sampling sites for geochemical surveillance purposes although the high gas discharge rate from the lake may occasionally prevent any fluid sampling alternatively as already suggested by recent studies on the behavior of light hydrocarbons in different volcanic environments the compositional features of the organic gas fraction in the more accessible outer flank thermal discharges could usefully be utilized at least to assess the thermodynamic conditions of the volcanic hydrothermal system since these compounds are affected by secondary processes only at limited extent

compound specific carbon and nitrogen isotopic compositions of chlorophyll a and its derivatives reveal the eutrophication history of lake zurich switzerland to reconstruct the impact of eutrophication on phototrophic communities and the biogeochemical cycling of carbon and nitrogen in the surface water we investigated the distributions and carbon and nitrogen isotopic compositions 13c and 15n values of chlorins in the sediments of lake zurich the chlorin distributions were dominated by chlorophyll a chl a and its derivatives which reflect rapid degradation to the pheopigments in the water column and sediments of the lake the 13c values of these sedimentary chlorins followed the historical trends of eutrophication and reoligotrophication except in the surface sediments which were characterised by higher relative contributions of aged redeposited organic matter om the 13c values of the sedimentary chlorins together with bulk sediment 13c values and c n ratios indicate that the phototrophic communities in the lake used a 13c depleted carbon source which is mainly of aquatic origin the 15n values of chlorins reflect the predominance of nitrate assimilating phototrophs especially the non n2 fixing cyanobacterium planktothrix rubescens prevalent during sediment deposition shifts in 15n values of chl a followed mostly the trends in eutrophication and reoligotrophication but were also affected by community assemblage shifts to diatoms and or other cyanobacteria at the end of the 19th century and during the eutrophication maximum in the 1970s the lower 15nchl a values in the surface sediments coincide with increasing nitrogen to phosphorus ratios and reduced water column mixing that characterise the recent reoligotrophication period and may explain the predominance of p rubescens in lake zurich in contrast the higher contributions of laterally transported om explains the large offset of 15n values of the pheopigments relative to chl a which is supported by the high radiocarbon age of the surface sediments

sedimentary nitrogen isotopic ratio as a recorder for surface ocean nitrate utilization in two contrasting regions of the ocean the equatorial pacific and the southern ocean the 15n of core top sediments were strongly related to no3 in surface waters with distance from the equator in the equatorial pacific 15n increased from 7 to 16 as no3 decreased from 8 m to 0 1 m going from 60 to 30 s in the se indian ocean core top 15n increased from 5 to 11 as surface no3 decreased from 25 m to 0 1 m these results are strong evidence that sedimentary 15n in these regions is recording the increasing isotopic enrichment of near surface no3 with its depletion by phytoplankton in the case of the equatorial pacific 15n values for sinking particles collected at 150 m matched well the core top sediment values demonstrating little diagenetic alteration of the near surface generated isotopic signal these equatorial pacific data sets have variations with near surface no3 consistent with rayleigh fractionation kinetics for a fractionation factor u of 2 5 this value is substantially lower than previously found for temperate or polar regions perhaps as a result of differences in phytoplankton species assemblage or growth condition in the southern ocean south of the polar front comparison of 15n values for opal rich sediments south and sinking particles indicates an apparent 5 diagenetic enrichment relative to the surface generated signal that requires further investigation this exception aside our observations show that the surface water relationship of increasing 15n with increasing no3 depletion is generally transmitted to and preserved in the sediments an important requirement for further development and application of this important paleoceanographic tool

mineral assisted production of benzene under hydrothermal conditions insights from experimental studies on c6 cyclic hydrocarbons abstract volatile organic compounds vocs are ubiquitously present at low but detectable concentrations in hydrothermal fluids from volcanic and geothermal systems although their behavior is strictly controlled by physical and chemical parameters the mechanisms responsible for the production of most vocs in natural environments are poorly understood among them benzene whose abundances were found to be relatively high in hydrothermal gases can theoretically be originated from reversible catalytic reforming processes i e multi step dehydrogenation reactions involving saturated hydrocarbons however this hypothesis and other hypotheses are difficult to definitively prove on the basis of compositional data obtained by natural gas discharges only in this study therefore laboratory experiments were carried out to investigate the production of benzene from cyclic hydrocarbons at hydrothermal conditions specifically 300 c and 85 bar the results of experiments carried out in the presence of water and selected powdered minerals suggest that cyclohexane undergoes dehydrogenation to form benzene with cyclohexene and cyclohexadiene as by products and also as likely reaction intermediates this reaction is slow when carried out in water alone and competes with isomerization and hydration pathways however benzene formation was increased compared to these competing reactions in the presence of sulfide sphalerite and pyrite and iron oxide magnetite and hematite minerals whereas no enhancement of any reaction products was observed in the presence of quartz the production of thiols was observed in experiments involving sphalerite and pyrite suggesting that sulfide minerals may act both to enhance reactivity and also as reactants after dissolution these experiments demonstrate that benzene can be effectively produced at hydrothermal conditions through dehydrogenation of saturated cyclic organic structures and highlight the crucial role played by minerals in this process

palaeolimnological approaches to climate change with special regard to the biological record abstract lakes systems respond physically chemically and biologically to changes in climate and these responses are registered in many various ways in lake sediment records this paper focuses principally on the biological record and describes recent research that aims to reconstruct i past variability in effective moisture and ii past variability in temperature changes in effective moisture are manifested especially by changes in lake water level in closed lake basins water level change can cause significant changes in water salinity that is registered in sediments by changes in the composition of fossil assemblages especially diatoms in open freshwater lake basins changes in water level are best reconstructed from the aquatic macrofossil record and potentially from the ratio of open water to littoral species of cladocera ostracods and diatoms the most promising biological method for reconstructing past temperature is chironomid analysis and a range of new chironomid temperature transfer functions are being developed however biological responses to changing temperature are usually indirect as a result of temperature effects on water column stratification nutrient cycling and alkalinity generation and in most cases a correct interpretation of the climatic significance of changes in the fossil record requires an understanding of the processes that are operating in the water column a multi proxy whole lake approach is advocated as the best way forward not only as a means of reconstructing past climate but also as a means of assessing the impact of climate change on lake systems

groundwater flow and chemistry of the oases of al wahat ne libya the quality and geochemistry of groundwater are significantly affected by the depositional environment of aquifer sediments miocene sediments in al wahat area jalu awjilah and shakherah oases in the libyan desert at the north east of the country have been deposited in fluvial marginal marine and marine environments the purposes of this paper are to describe the areal distribution of the dominant water quality constituents to identify the major hydro geochemical processes that affect the quality of water and to evaluate the relations of sedimentary depositional environments and groundwater flow to the quality and geochemistry of water in aquifer sediments of post eocene this study is the first investigation in al wahat oasis and also in the whole sahara which introduces the importance of considering the end members and the synsedimentary influence for the interpretation of the aquifer hydrochemistry the area involved in this study is within the boundaries 28 n 30 n and 21 e 23 e eighteen wells are selected in the area including eight piezometers and ten samples were analysed from wells used for domestic and agricultural purposes results show high and significant increase in total dissolved solids especially na cl so42 and no3 compared with the previous years the chemical results for the groundwater samples in al wahat are classified according to the stuyfzand groundwater classification system the water type is mostly brackish and brackish saline nacl in the downstream direction and fresh brackish nahco3 upstream these water types indicate that groundwater chemistry is changed by cation exchange reactions during flushing of the diluted saline aquifer by freshwater from the south the different stages of cation exchange produce a chromatographic sequence of groundwater types these cation exchange reactions during the freshening process occur mainly in the intercalated clay resulting in a na increase and peaks of k and mg2 in the aquifer in the north the synsedimentary marine influence on the groundwater is stronger and the abstraction for irrigation is higher upconing of deep saline water and anthropogenic pollution may contribute significantly to the aquifer water quality calcite equilibrium and gypsum dissolution are also important hydrochemical processes in the aquifer

predicting gully occurrence at watershed scale comparing topographic indices and multivariate statistical models abstract in this study the ability of five topographic indices to predict the gully trajectories observed in two adjacent watersheds located in sicily italy was evaluated two of these indices named mspi and mtwi as far as we know have never been employed to this aim they were obtained by multiplying the stream power index spi and the topographic wetness index twi respectively by the convergence index ci the predictive ability of the topographic indices was measured by using both cut off independent auc area under the receiver operating characteristic curve and dependent statistics cohen s kappa index sensitivity specificity these statistics were calculated also for 100 mars multivariate adaptive regression splines and 100 lr logistic regression model runs which used as predictors the topographic variables i e contributing area slope steepness plan curvature and convergence index combined into the five indices performance statistics of both topographic indices and statistical models were calculated using 100 random samples of 2 m grid cells which were extracted only from flow concentration lines this was done in order to focus the validation process on where gully erosion is more likely to occur mspi achieved the best predictive skill auc 0 93 0 71 among the topographic indices and exhibited similar and better accuracy than local i e trained and validated in the same watershed and transferred i e trained in one watershed and tested in the other one lr models respectively on the other hand mspi performed similarly to transferred mars runs auc 0 92 0 71 but slightly worse than local mars runs auc 0 95 0 77 based on the results of this experiment it can be inferred that i including ci helps in detecting hollow areas where gullies are more likely to occur and ii mpsi can be a valid alternative to a data driven approach for mapping gully erosion susceptibility in areas where a gully inventory is not available which is necessary to calibrate statistical models

signs of potential renewal of eruptive activity at la fossa vulcano aeolian islands since the end of the last magmatic eruption 1890 activity of la fossa southern tyrrhenian sea italy has consisted of fumarolic emissions of fluctuating intensity fluids are discharged principally at two fumarolic fields located in the northern rim of the active crater and at the beach sited at its northern foot increased thermal seismic and geochemical activity has been recorded since 1978 when an earthquake of m 5 5 occurred in the region this paper combines available geophysical and geochemical information in order to develop a tentative interpretation of two episodes of apparent unrest which occurred in 1985 and 1987 1988 enhancing the risk of renewal of the eruptive activity the 1985 unrest consisted essentially of a sharp build up of the internal pressure in the shallow hydrothermal system which was induced by the injection of hot gases of magmatic origin the crater fumaroles displayed significant increases in co2 and other acid species but their outlet temperature did not change conversely the 1987 1988 episode was characterized by appreciable modifications at the crater fumaroles with only secondary effects at the fumarole system of the beach the sliding of part of the eastern flank of the la fossa cone into the sea occurred on 20 april 1988 when the region was affected by crustal dilatation producing a seismic sequence of relatively high intensity both episodes of unrest were accompanied by increases of local microseismic activity which affected the nothern sector of the island in 1985 and the southern one in 1988 finally a phase of appreciable areal contraction was detected in 1990 probably due to the effect of the cooling and crystallization of magma at relatively shallow depths accompanying the increased thermal activity at the crater fumaroles regional tectonic stress seems to play an important role in the transition of the volcanic system from a phase of relative stability to a phase of apparent unrest inducing the heating and the expansion of shallow hydrothermal fluids available information is insufficient to indicate whether or not the volcano is building towards the renewal of a magmatic eruption and there is no evidence to hypothesize episodes of significant magma migration the frequency of measurements of many parameters needs to be increased in order to learn more about the temporal relationships between geochemical and geophysical variations preceding and accompanying periods of increased thermal activity this will probably be a valid tool for recognizing short term precursors of a future eruption reducing the risk of false alarms

the magmatic and hydrothermal dominated fumarolic system at the active crater of lascar volcano northern chile low to high temperature fumaroles discharging from the active crater of lascar volcano northern chile have been collected in november 2002 may 2005 and october 2006 for chemical and isotopic analysis to provide the first geochemical survey on the magmatic hydrothermal system of this active volcano chemical and isotopic gas composition shows direct addition of high temperature fluids from magmatic degassing mainly testified by the very high contents of so2 hcl and hf up to 87 800 29 500 and 2 900 mol mol and the high r ra values up to 7 29 contributions from a hydrothermal source mainly in gas discharges of the active crater rim has also been detected significant variations in fluid chemistry mainly consisting of a general decrease of magmatic related compounds i e so2 have affected the fumarolic system during the period of observation indicating an increase of the influence of the hydrothermal system surrounding the ascending deep fluids the chemical composition of active crater fumaroles has been used to build up a geochemical model describing the main processes that regulate the fluid circulation system of lascar volcano to be utilized in volcanic surveillance

physical chemical conditions of the teide volcanic system tenerife canary islands the teide volcano 3717 m is the central structure of the island of tenerife and at present its morphology is that of a stratovolcano which has grown on a large caldera with a collapse 17 km in diameter which was generated some 0 6 million years ago the different studies that have been carried out seem to indicate that in a oversimplified model there is an intermediate magma chamber with an approximate volume of 30 km3 and located 2 3 km below the actual base of the caldera i e almost at sea level with a temperature of 430 50 c and a pressure of 400 100 bar the summit fumarole emissions are 85 c and are formed mainly of co2 with small amounts of sulphur species h2 ch4 and he the water vapor 68 82 emitted with the gases comes from the vaporization of a perched aquifer in the upper cone as shown by the isotopic analyses

the evolution of a dynamic geological system the support of a gis for geochemical measurements at the fumarole field of vulcano italy abstract the island of vulcano aeolian arc southern italy has displayed several periods of volcanic unrest since the end of the last eruption 1890 we report here results obtained from a long term survey concerning variations of both the steam output and the exhaling surface area at the summit crater fumarolic field of la fossa the field measurements analysed in a geographical information system gis show a highly dynamic volcanic system in which deep variations in the geochemistry and the temperature of the released fluids were accompanied by fluctuations in the mass output of steam and the topography of the crater field the use of a gis facilitated digitized reconstructions of maps of the crater field in addition to analysis of the steam flux data the fumarolic field expanded its surface area from 50 m 2 in 1983 to more than 2400 m 2 in 1995 accompanied by an increase in steam output from 152 to about 1400 tonnes per day the possibility that the observed phenomena are related to volcano tectonic activity and to magma uprising is taken into consideration

the episodic and abrupt geochemical changes at la fossa fumaroles vulcano island italy and related constraints on the dynamics structure and compositions of the magmatic system abstract herein we report on the chemical and isotopic c h o and he compositions of the fluids from la fossa crater fumaroles of vulcano from 1999 to 2010 consistent with records obtained since the end of the 1980s our data show that the geochemical features of the fumarole system have experienced several episodes of remarkable change each lasting no more than a few months typical signatures of these short term anomalies are large increments in co 2 n 2 and he concentrations coupled to increased 13 c 12 c isotopic ratios but their meaning remains widely debated within a model of fumarolic fluids based on mixing between hydrothermal and magmatic endmembers we have developed a novel approach to constrain chemical he co 2 and n 2 he and isotopic 13 c 12 c d h and 3 he 4 he ratios of the magmatic endmember during the short term anomalies although much of the geochemical variability in fumaroles results from changes in mixing proportions the magmatic fluid unquestionably shows significant variations in time the magmatic he co 2 n 2 he 13 c 12 c and 3 he 4 he values throughout 1988 1996 differed from those feeding the anomaly at the end of 2004 early clues of the new magmatic fluid appeared in 1998 1999 far from any short term anomaly whereas new and old magmatic fluids coexisted after 2004 we quantitatively prove that the detected geochemical changes are consistent with the degassing path of a magma having a latitic composition and suggest the presence of two magma ponding levels at slightly different pressures where bubble melt decoupling can occur the different he isotope compositions at these levels suggest low hydraulic connectivity typical of a complex reservoir with dike and sill structures in this framework the short term geochemical anomalies are probably due to gas accumulation at the top of magma bodies followed by massive escape or activation of new degassing levels in the reservoir for which the stress field almost certainly plays a key role such a scenario explains the observed increases in both fumarole output and shallow high frequency seismicity due to increased pore pressure during the anomalies while being consistent with the concomitant absence of any deep seismicity or ground deformation eventually related to magma movement

1980 1990 ten years of geochemical investigation at phlegrean fields italy abstract a systematic geochemical investigation on the thermal manifestations of the volcanic area of phlegrean fields started in 1980 with the aim of obtaining useful information about the changes possibly occurring at the same time of vertical ground movements termed as bradyseismic which frequently interested this area the attention was initially given to the fumaroles and the boiling pools of solfatara and pisciarelli then subsequently extended to thermal springs dug wells and crater lakes analytical data pertaining to a period preceding the last crisis of 1982 1984 were then available as well as other data collected during the previous crisis of 1970 a comprehensive picture of the variations observed before during and after the acceleration of vertical movement has been drawn according to the results obtained the intrusion of a magmatic body as the trigger of the observed ground deformation is considered unrealistic the whole area appears now in a quiet stage and no further perturbation is expected without previous significant tectonic activity chemical precursors appear suitable for an early detection of changes occurring at depth to forecast possible consequences to be expected in the surface environment

tracking aquatic change using chlorin specific carbon and nitrogen isotopes the last glacial interglacial transition at lake suigetsu japan joint carbon and nitrogen isotope measurements were made from chlorins chlorophyll a phaeophytin a and pyrophaeophytin a extracted from the last glacial interglacial transition sediments of lake suigetsu central japan these data highlight both the potential and difficulty of using chlorin specific isotopes to track aquatic change from lake sediments 13c and 15n of the three chlorins show coherent patterns with time supporting the theory that phaeophytin a and pyrophaeophytin a are early diagenetic products of chlorophyll a and that despite this transition their isotopic signatures remain intact however our data suggest that the isotopic composition of phaeophytin a and pyrophaeophytin a can be imprecise proxies for the isotope composition of chlorophyll a possibly owing to the complex array of factors which affect the synthesis transformation and sedimentation of these phaeopigments in nature the total accumulation of organic matter in lake suigetsu appears to be controlled by the balance of allocthonous and authocthonous material as reflected by the c n ratio however both bulk organic and chlorin specific 13c show similar changes suggesting that the first order variability in bulk organic 13c reflects aquatic change by contrast there is no similarity between chlorin and bulk 15n suggesting that interpretation of bulk 15n in this setting is compromised by diagenetic alteration the isotopic composition of chlorins are interpreted to reflect the response of aquatic primary productivity to post glacial environmental change however further research into the synthesis and transformation of chlorins in the modern environment is required in order to facilitate a more rigorous approach to interpreting isotope ratios in chlorins extracted from sediments

new aspects on the formation of hydrocarbon source rocks episodic volcanism favors as shown by examples from europe the usa and brazil the formation of organic rich sediments hydrocarbon source rocks the examples examined from europe comprise the lower carboniferous oil shale group scotland upper carboniferous coal measures western germany upper jurassic kimmeridge shale north sea area lower cretaceous blattertonstein northwest germany and eocene messel oil shale rheingraben examples from the usa are devonian mississippian gas shales permian phosphoria shale middle cretaceous mowry shale eocene green river shale and miocene monterey shale examples from brazil are permian irati oil shale and oligocene paraiba valley oil shale volcanism is reflected during sedimentation 1 by exhalation of so2 and or co2 2 volcanic ashfalls 3 by generation of anoxia and preservation of organic matter and 4 by halmyrolytic alteration of volcanic ashes into highly surface active clay minerals montmorillonite

diffuse soil emission of hydrothermal gases co2 ch4 and c6h6 at solfatara crater campi flegrei southern italy abstract measurements of soil fluxes of hydrothermal gases with special emphasis on c 6 h 6 as well as chemical composition of mono aromatic compounds in fumaroles and air were carried out in april 2012 at the solfatara crater campi flegrei southern italy to investigate the distribution and behavior of these species as they migrate through the soil from their deep source to the atmosphere soil fluxes of co 2 ch 4 and c 6 h 6 exhibit good spatial correlation suggesting that diffuse degassing is mainly controlled by local fractures the calculated total output of diffuse c 6 h 6 from solfatara is 0 10 kg day 1 whereas fluxes of co 2 and ch 4 are 79 10 3 and 1 04 kg day 1 respectively a comparison between soil gas fluxes and fumarole composition reveals that within the crater soil ch 4 is significantly affected by oxidation processes which are more efficient for low gas fluxes being dependent on the residence time of the uprising hydrothermal gases at shallow depth benzene degradation mainly proceeding through oxidation via benzoate seems to be strongly controlled by the presence of a shallow so 4 2 rich aquifer located in the central and southwestern sectors of the crater suggesting that the process is particularly efficient when so 4 2 acts as terminal electron acceptor so 4 reduction relatively high c 6 h 6 c 7 h 8 ratios typical of hydrothermal fluids were measured in air close to the main fumarolic field of solfatara crater here c 6 h 6 concentrations whose detection limit is 0 1 g m 3 are more than one order of magnitude higher than the limit value for ambient air 5 g m 3 this suggests that hydrothermal fluids have a strong impact on air quality in the immediate surroundings of the fumarolic vents significant concentrations of endogenous mono aromatics were also detected in air samples collected from the northern and western sides of the crater where these gas compounds are mostly fed by diffuse degassing through the crater bottom soil

fluid geochemistry of hydrothermal systems in the arica parinacota tarapaca and antofagasta regions northern chile we investigate the chemical and isotopic composition of water and gas thermal discharges from six hydrothermal systems in the tarapaca and antofagasta regions northern chile surire puchuldiza tuja pampa lirima pampa apacheta el tatio and torta de tocorpuri to determine the chemical physical conditions at the fluid source the chemical facies of the thermal discharges vary from na cl el tatio puchuldiza tuja and part of surire where so42 rich waters also occur to na ca2 cl so42 pampa lirima ca2 so42 hco3 torta de tocorpuri and ca2 so42 pampa apacheta the gas seeps are characterized by the dominance of co2 h2s and ch4 with n2 ar ratios that occasionally are up to 450 significant amounts of so2 and hcl are present at pampa apacheta water and gas geothermometry suggests that el tatio and puchuldiza tuja fluid reservoirs have relatively high reservoir equilibrium temperature up to 270 c gases from pampa apacheta apparently equilibrated at unusually high temperature for hydrothermal fluids up to 350 c being likely related to an active magmatic system as testified by the presence of highly acidic gas compounds such as so2 and hcl on the contrary low equilibrium temperatures were calculated for the surire fluids 200 c suggesting interactions of deep originated fluids with meteoric water at shallow depth shallow low temperature aquifers mask any signal of deep fluids in the pampa lirima and torta de tocorcupi thermal discharges despite the variations in temperatures he isotopic compositions and redox conditions of the fluid reservoirs consistently indicate a significant contribution from magmatic degassing although geophysical studies are necessary to better constrain the geothermal potential of northern chile the geothermometric estimations carried out in the present study indicate that el tatio pampa apacheta surire and puchuldiza tuja can be regarded as the most promising areas and deserve more detailed geological investigations

evidence from chlorin nitrogen isotopes for alternating nutrient regimes in the eastern mediterranean sea abstract nitrogen isotopes of chlorins degradation products of chlorophyll reflect the isotopic composition of nutrient n utilized by marine phytoplankton communities here we show that in sediments of the eastern mediterranean pleistocene and holocene values of 15n for chlorins and total nitrogen vary in concert with a consistent offset of 5 reflecting the fractionation imparted during chlorophyll biosynthesis samples from the integrated ocean drilling program sites 964 and 969 were analyzed at a sampling resolution of 4 10 cm clustered around sapropel events 2 3 4 and 5 100 170 ka in low organic content sediments chlorin values of 0 coincident with total nitrogen values of 5 indicate that the latter reflects the original biomass and is not a consequence of diagenetic isotope enrichment in sapropel horizons the chlorin and total nitrogen values are 5 more negative 5 and 0 respectively resembling previously reported modern day water column particulates 0 we suggest that nutrient conditions in the eastern mediterranean correspond to three scenarios and that the similarity between sapropel and modern day bulk 15n is coincidental organic poor marl sediments formed under oligotrophic conditions where surface productivity resulted from upwelling of atlantic sourced nitrate sapropels were characterized by enhanced diazotrophy that was likely fueled by increased riverine p fluxes to surface waters present day conditions are dominated by anthropogenic n sources these scenarios agree with a model of sapropel formation in which stratification caused by increased fresh water inputs led to n fixation due to p n nutrient imbalance enhanced production combined with stratification promoted and maintained anoxic deep waters consequently increasing organic matter preservation such a model may be relevant to interpreting other episodes of intense organic matter deposition in past oceans

varying responses to indian monsoons during the past 220 kyr recorded in deep sea sediments in inner and outer regions of the gulf of aden although the climate in the arabian sea is controlled primarily by the southwest monsoon the southwest monsoon has little influence in the gulf of aden to examine the different responses to monsoons between the gulf of aden and areas outside the gulf a comprehensive data set of bulk organic and inorganic geochemistry sea surface temperature and 15n of pheopigments was obtained from deep sea sediment cores recovered from inner and outer regions of the gulf the results indicated that during the past 220 kyr the influence of the southwest monsoon was stronger in the outer region of the gulf than in the inner region which implies that the southwest monsoon trajectory has not changed substantially during that time period furthermore influxes of o2 depleted water from the southern ocean and the lateral advection of upwelled seawater also had limited influence in the inner region in contrast concentrations of lithogenic materials transported by the southwest monsoon were similar in the two regions 15n of pheopigments indicated that during the last glacial maximum the southwest monsoon was weaker and the northeast monsoon was stronger than at present a stronger southwest monsoon during interglacials enhanced primary productivity and may have caused anoxic conditions to develop in the arabian sea as indicated by redox proxies in the outer region anoxic conditions also formed during mis 3 but no increase in the primary productivity is indicated therefore another mechanism such as an influx of o2 depleted water from the southern ocean may have been the cause

interpretation of the nitrogen isotopic composition of precambrian sedimentary rocks assumptions and perspectives nitrogen isotope compositions in sedimentary rocks d 15 n sed are routinely used for reconstructing cenozoic n biogeochemical cycling and are also being increasingly applied to understanding the evolution of ancient environments here we review the existing knowledge and rationale behind the use of d 15 n sed as a proxy for the precambrian n biogeochemical cycle with the aims of i identifying the major uncertainties that affect analyses and interpretation of nitrogen isotopes in ancient sedimentary rocks ii developing a framework for interpreting the precambrian d 15 n sed record iii testing this framework against a database of precambrian d 15 n sed values compiled from the literature and iv identifying avenues of focused research that should increase confidence in interpreting precambrian d 15 n sed data this review highlights the intrinsic complexity of the d 15 n sed proxy and the significant effort that remains to realize its potential specifically it is crucial to gain a better understanding of how and when diagenesis and metamorphism affect the d 15 n of bulk and kerogen bound nitrogen ultimately more data are required to apply statistics to interpreting d 15 n sed variability within given geological time intervals finally numerical modeling of the d 15 n sed variability expected in different environments under varying redox scenarios is necessary to establish a predictive template for interpreting the ancient nitrogen isotope record in spite of the challenges facing the application of this proxy to the precambrian the existing d 15 n sed record shows several features possibly related to the stepwise oxygenation of the surface environment underlining the potential for nitrogen isotopes to reveal clues about the evolution of early earth

the influence of the inventory on the determination of the rainfall induced shallow landslides susceptibility using generalized additive models abstract data driven methodologies are widely used for the reconstruction of shallow landslide susceptibility maps the outputs of these models strictly depend on the type of landslide inventories used for the modelling thus this work performed a deep analysis of the role of different inventories on the definition of shallow landslide susceptibility of a particular area modeled through a data driven technique generalized additive model distinct shallow landslide inventories referred to the same rainfall event or to different rainfall events can produce different maps of susceptibility distribution for the same area despite a similar predictive capability the models built for the same area produced different susceptibility maps as estimated by low values of the cohen s kappa coefficient 0 13 0 46 if inventories obtained using different landslide detection methods are available the models of susceptibility will be affected by the position and shape of the phenomena that could be detected by each tool an inventory created integrating the visual interpretation of high resolution images with field surveys allows to obtain more accurate inventories to derive a better representation of the proneness of the territory towards shallow landsliding in the case of inventories related to the same rainfall event carried out with different criteria the susceptibility distribution is influenced by the choices adopted as regards in particular the type and the mapping criteria of phenomena included in the inventory for shallow landslide inventories triggered by different rainfall events in the same area the classification of the territory in terms of susceptibility is strictly connected to each specific rainfall event and reflects the relative shallow slope stability of a region only under similar rainfall conditions shallow landslide susceptibility obtained with a multi temporal inventory grouping landslides occurred in few years during more events provides a more accurate estimation of the predisposition to shallow landsliding in consequence of the typical rainfall triggering patterns of an area

geogenic and atmospheric sources for volatile organic compounds in fumarolic emissions from mt etna and vulcano island sicily italy 1 in this paper fluid source s and processes controlling the chemical composition of volatile organic compounds vocs in gas discharges from mt etna and vulcano island sicily italy were investigated the main composition of the etnean and volcano gas emissions is produced by mixing to various degrees of magmatic and hydrothermal components vocs are dominated by alkanes alkenes and aromatics with minor though significant concentrations of o s and cl f substituted compounds the main mechanism for the production of alkanes is likely related to pyrolysis of organic matter bearing sediments that interact with the ascending magmatic fluids alkanes are then converted to alkene and aromatic compounds via catalytic reactions dehydrogenation and dehydroaromatization respectively nevertheless an abiogenic origin for the light hydrocarbons cannot be ruled out oxidative processes of hydrocarbons at relatively high temperatures and oxidizing conditions typical of these volcanic hydrothermal fluids may explain the production of alcohols esters aldehydes as well as o and s bearing heterocycles by comparing the concentrations of hydrochlorofluorocarbons hcfcs in the fumarolic discharges with respect to those of background air it is possible to highlight that they have a geogenic origin likely due to halogenation of both methane and alkenes finally chlorofluorocarbon cfc abundances appear to be consistent with background air although the strong air contamination that affects the mt etna fumaroles may mask a possible geogenic contribution for these compounds on the other hand no cfcs were detected in the vulcano gases which are characterized by low air contribution nevertheless a geogenic source for these compounds cannot be excluded on the basis of the present data

an extended and revised lake suigetsu varve chronology from 50 to 10 ka bp based on detailed sediment micro facies analyses abstract lake suigetsu japan is a key site for radiocarbon 14c calibration and palaeo environmental reconstruction in east asia here we present a description of the sediment micro facies which in combination with a new approach to varve interpolation allows construction of a revised varve based chronology that extends the previous 2012 varve based chronology by 10 ka back to 50 ka bp challenges in varve counting and interpolation which were previously discussed in detail only for the last glacial interglacial transition are described here back to 50 ka bp furthermore the relative merits of varve counting by xrf scanning and by thin section microscopy are discussed facies analysis reveals four facies zones their transitions driven by both local and climatic controls the lamination quality of the sediment is highly variable and varve interpolation reveals that in the analysed time interval on average only 50 of the annual cycles are represented by seasonal layers in the remaining years seasonal layers are indistinguishable i e either did not form or were not preserved for varve interpolation an advanced version of the varve interpolation program was used which enabled the construction of the longest purely varve dated chronology published despite long intervals of poor lamination quality the calculated interpolation uncertainty is 8 9 and 4 6 which is well within expectations considering the high degree of interpolation and the length of the record

factors controlling 13c contents of sedimentary organic compounds principles and evidence the carbon isotopic composition of any naturally synthesized organic compound depends on 1 the carbon source utilized 2 isotope effects associated with assimilation of carbon by the producing organism 3 isotope effects associated with metabolism and biosynthesis and 4 cellular carbon budgets these factors are reviewed and quantitative considerations summarized particularly with regard to active and passive modes of carbon assimilation by phytoplankton and the existence of discernible regularities in isotope effects associated with lipid biosynthesis it is concluded that n alkyl lipids are in general depleted in 13c by about 1 5 relative to polyisoprenoid lipids produced by the same organism the effects of biological reworking on isotopic compositions of organic carbon are examined and it is suggested that enrichment of 13c in sedimentary organic carbon may result from loss of ch4 from zooplanktonic gut communities isotopic methods for estimation of ancient co2 levels are considered and a hyperbolic form favored for the relationship between concentrations of dissolved co2 and isotopic fractionation

origin of light hydrocarbons in gases from mud volcanoes and ch4 rich emissions abstract this paper presents new chemical data of hydrocarbon rich gases discharged from mud volcanoes and ch4 rich emissions located in different areas of italy northern apennines and sicily the determination of c5 c10 alkanes cyclics and aromatics was carried out by gc ms while the main gas species and c1 c4 hydrocarbons were analyzed by gc tdc and gc fid respectively methane is by far the most abundant component of all the investigated gas emissions with the exception of part of those discharging close to mt etna volcano which are co2 rich the gas samples collected from the emilia apennine and sicily show d ch4 and 13c ch4 values typical of thermogenic gases most gases from the romagna apennine discharge methane with a biogenic isotopic signature non methane hydrocarbons of biogenic gases are almost exclusively c2 c4 alkanes with minor amounts fraction of mol mol of c4 compounds including few aromatics and cyclics likely deriving from minor thermogenic contribution not evidenced by the 13c ch4 and d ch4 values the etnean gases whose r ra and 13c co2 values indicate a strong contribution from a hydrothermal fluid source related to the nearby volcanic system show a significant enrichment of aromatics compounds up to 36 of the non methane organic gas fraction which is likely produced by catalytic reforming processes such as dehydrocyclization of alkanes the thermogenic gases from the apennines and southwestern sicily are characterized by the presence of more than 20 different cyclic compounds with concentrations up to several mol mol cyclic compounds are likely formed by i thermal cracking and ii uncompleted aromatization of alkanes occurring at depth 3 km and temperatures not exceeding 120 150 c

seasonally specific responses of the east asian monsoon to deglacial climate changes the deglacial meltwater pulse in the north atlantic that induced the younger dryas event also prompted climate cooling in east asian monsoon regions such as japan and coastal mid latitude china however very little is understood about the mechanism that can transmit changes in the north atlantic to the far east here we show that the shutdown of the north atlantic thermohaline circulation brought about significantly lower temperatures and higher precipitation in the japanese winter whereas the change in the japanese summer climate was considerably smaller the cooling of the siberian air mass seems to have caused an increased pressure gradient between siberia and the west pacific in winter intensifying the winter monsoon the mongolian high pressure system and the westerly jet stream played an important role in the teleconnection in contrast the warming at the onset of the late glacial interstadial gi 1 bolling allerod in the west pacific did not have season specific features implying that the principal driving mechanism of this warming event may lie in a pan hemispheric or global factor such as insolation changes

molecular evidence for basin scale photic zone euxinia in the permian zechstein sea abstract previous studies of maleimides 1 h pyrrole 2 5 diones oxidative degradation products of chlorophylls and bacteriochlorophylls and aromatic compounds derived from certain carotenoids i e isorenieratene indicate that photic zone euxinia pze occurred at least intermittently during deposition of the german kupferschiefer late permian however that work was restricted to a stratigraphic profile through the kupferschiefer of the lower rhine basin a shallow lagoon setting and it was not established if photic zone euxinia prevailed in the larger and deeper basins of the permian zechstein sea here we present maleimide and porphyrin distributions in sediments from the northern and southern permian basins in samples from both basins methyl iso butyl me i bu maleimide was recovered from the free extractable fraction and upon oxidation of vanadyl and nickel alkyl porphyrins on structural grounds me i bu maleimide derives ultimately from bacteriochlorophyll bchl c d or e and is thus indicative of the presence of green sulfur bacteria in the ancient zechstein sea consistent with this c 34 and c 35 porphyrins apparently derived from bacteriochlorophyll d were also identified in the northern basin samples because green sulfur bacteria require both light and free h 2 s these results indicate that photic zone euxinia occurred at least periodically during the early history of the zechstein sea

chemical variations in fumarolic gases at vulcano island southern italy seasonal and volcanic effects abstract because of increasing in fumarolic activity at vulcano since september 1987 regular sampling and analysis is conducted on the well known f5 crater fumarole t 330 5 c significant chemical variations have been recorded over the period 1987 1989 variations of water vapour in the fumarolic fluid follow seasonal pattern and can be related to both external seasonal and internal volcanic influences suggesting a control by a shallow water aquifer significant variations of h 2 o and of some species in the anhydrous gas phase h 2 so 2 hcl hf n 2 he probably result from chemical or dynamic changes in the feeding system at depth several mechanism are considered for explaining the chemical trends results in relationship to the recent increase in activity a growing input of deep magmatic fluids is not supported by the low co content and the apparent constancy of the 3 he 4 he ratio apparent equilibrium temperatures close to the fumarolic outlet temperature 350 400 c were calculated suggesting isothermal expansion of the gas from a shallow equilibration zone comparison with the fumaroles at sea level porto di levante suggests that these latter may be fed a different hydrothermal systems variable interaction between both systems may account for some of the chemical variations observed at f5 fumarole

predicting the landslides triggered by the 2009 96e ida tropical storms in the ilopango caldera area el salvador ca optimizing mars based model building and validation strategies the main topic of this research was to evaluate the effect in the performance of stochastic landslide susceptibility models produced by differences between the triggering events of the calibration and validation datasets in the caldera ilopango area el salvador mars multivariate adaptive regression splines based susceptibility modeling was applied using a set of physical environmental predictors and two remotely recognized landslide inventories one dated at 2003 1503 landslides which was the result of a normal rainfall season and one which was produced by the combined effect of the ida hurricane and the 96e tropical depression in 2009 2237 landslides both the event inventories included shallow debris flow or slide landslides which involved the weathered mantle of the pyroclastic rocks that largely outcrop in the study area to this aim different model building and validation strategies were applied self validation forward and backward chrono validations and their performances evaluated both through cutoff dependent and independent metrics all of the tested models produced largely acceptable auc area under curve values albeit a loss in the predictive performance from self validation to chrono validation was observed besides in terms of positive negative predictions some critical differences arose using the 2009 extreme landslide inventory for calibration resulted in higher sensitivity but lower specificity conversely using the 2003 normal trigger landslide calibration inventory led to higher specificity but lower sensitivity with relevant increase in type ii errors these results suggest the need for investigating the extent of such effects taking multitrigger intensities inventories as a standard procedure for susceptibility assessment in areas where extreme events potentially occur

improving transferability strategies for debris flow susceptibility assessment application to the saponara and itala catchments messina italy abstract debris flows can be described as rapid gravity induced mass movements controlled by topography that are usually triggered as a consequence of storm rainfalls one of the problems when dealing with debris flow recognition is that the eroded surface is usually very shallow and it can be masked by vegetation or fast weathering as early as one two years after a landslide has occurred for this reason even areas that are highly susceptible to debris flow might suffer of a lack of reliable landslide inventories however these inventories are necessary for susceptibility assessment model transferability which is based on calibrating a susceptibility model in a training area in order to predict the distribution of debris flows in a target area might provide an efficient solution to dealing with this limit however when applying a transferability procedure a key point is the optimal selection of the predictors to be included for calibrating the model in the source area in this paper the issue of optimal factor selection is analysed by comparing the predictive performances obtained following three different factor selection criteria the study includes i a test of the similarity between the source and the target areas ii the calibration of the susceptibility model in the training source area using different criteria for the selection of the predictors iii the validation of the models both at the source self validation through random partition and at the target transferring through spatial partition areas the debris flow susceptibility is evaluated here using binary logistic regression through a r scripted based procedure two separate study areas were selected in the messina province southern italy in its ionian itala catchment and tyrrhenian sides saponara catchment each hit by a severe debris flow event in 2009 and 2011 respectively the investigation attested that the best fitting model in the calibration areas resulted poorly performing in predicting the landslides of the test target area at the same time the susceptibility models calibrated with an optimal set of covariates in the source area allowed us to produce a robust and accurate prediction image for the debris flows activated in the saponara catchment in 2011 exploiting only the data known after the itala 2009 event

hydrothermal systems of the karymsky volcanic centre kamchatka geochemistry time evolution and solute fluxes abstract karymsky volcanic centre kvc at the middle of the frontal volcanic chain of the kamchatka arc consists of two joined calderas akademii nauk and karymsky volcano and hosts two hydrothermal systems akademii nauk an and karymsky k the an is a typical boiling system with na cl waters tds 1 g l low gas content co2 n2 with deep calculated temperatures of 200 c in contrast springs of the k system have lower temperatures up to 42 c strong gas bubbling tds 2 5 g l and are enriched in hco3 and so42 with mg2 as the main cation there are two intriguing characteristics of the k field i their co2 rich gas 97 mol has the highest 3he 4he ratios ever measured for hydrothermal systems in kamchatka of 8 ra where ra 1 4 10 6 and ii their thermal waters have an unusual cation composition mg na ca after the 1996 sublimnic eruption within an caldera new hot springs appeared close to the eruption site in this paper we synthesize all published and new geochemical data sets the karymsky lake and post 1996 new thermal springs demonstrate exponential decreases in their main dissolved species with a characteristic time of 5 to 8 years the chemistry of an and k springs did not change after the eruption however the concentration of chloride in the lake water approached 35 mg l compared with a background of 8 11 mg l revealing a possible new source of hot water within the karymsky lake all thermal fields of the kvc are drained by the karymsky river with an outflow rate at the source of 2 m3 s flowing out from karymsky lake and at the exit from the karymsky caldera of 4 5 m3 s using the measured solute fluxes at the source an springs and at the exit an k springs the natural heat flux from the two systems can be estimated as 67 mw and 120 mw respectively and 20 t d for the chloride output from both systems

assessment of susceptibility to earth flow landslide using logistic regression and multivariate adaptive regression splines a case of the belice river basin western sicily italy abstract in this paper terrain susceptibility to earth flow occurrence was evaluated by using geographic information systems gis and two statistical methods logistic regression lr and multivariate adaptive regression splines mars lr has been already demonstrated to provide reliable predictions of earth flow occurrence whereas mars as far as we know has never been used to generate earth flow susceptibility models the experiment was carried out in a basin of western sicily italy which extends for 51 km 2 and is severely affected by earth flows in total we mapped 1376 earth flows covering an area of 4 59 km 2 to explore the effect of pre failure topography on earth flow spatial distribution we performed a reconstruction of topography before the landslide occurrence this was achieved by preparing a digital terrain model dtm where altitude of areas hosting landslides was interpolated from the adjacent undisturbed land surface by using the algorithm topo to raster this dtm was exploited to extract 15 morphological and hydrological variables that in addition to outcropping lithology were employed as explanatory variables of earth flow spatial distribution the predictive skill of the earth flow susceptibility models and the robustness of the procedure were tested by preparing five datasets each including a different subset of landslides and stable areas the accuracy of the predictive models was evaluated by drawing receiver operating characteristic roc curves and by calculating the area under the roc curve auc the results demonstrate that the overall accuracy of lr and mars earth flow susceptibility models is from excellent to outstanding however auc values of the validation datasets attest to a higher predictive power of mars models auc between 0 881 and 0 912 with respect to lr models auc between 0 823 and 0 870 the adopted procedure proved to be resistant to overfitting and stable when changes of the learning and validation samples are performed in conclusion the highly acceptable predictive skill of the statistical models confirms the reliability of the procedure adopted to reconstruct the pre failure topographic conditions such a method solves the conceptual problem arising when post failure elevation data are the only source of topographic information available to model landslide susceptibility furthermore with respect to other solutions proposed in the past which identify as unstable the conditions of landslide surroundings our approach allows for more accurate measurement of those variables e g curvature convergence index topographic position index that depend on the relative position of a cell with respect to its nearby pixels

susceptibility assessment of earthquake triggered landslides in el salvador using logistic regression abstract this work has evaluated the probability of earthquake triggered landslide occurrence in the whole of el salvador with a geographic information system gis and a logistic regression model slope gradient elevation aspect mean annual precipitation lithology land use and terrain roughness are the predictor variables used to determine the dependent variable of occurrence or non occurrence of landslides within an individual grid cell the results illustrate the importance of terrain roughness and soil type as key factors within the model using only these two variables the analysis returned a significance level of 89 4 the results obtained from the model within the gis were then used to produce a map of relative landslide susceptibility

origin of fumarolic fluids from tupungatito volcano central chile interplay between magmatic hydrothermal and shallow meteoric sources tupungatito is a poorly known volcano located about 100 km eastward of santiago chile in the northernmost sector of the south volcanic zone this 5 682 m high volcano shows intense fumarolic activity it hosts three crater lakes within the northwestern portion of the summit area chemical compositions of fumarolic gases and isotopic signatures of noble gases 3he 4he and 40ar 36ar are up to 6 09 ra and 461 respectively and steam 18o and d suggest that they are produced by mixing of fluids from a magmatic source rich in acidic gas compounds so2 hcl and hf and meteoric water the magmatic hydrothermal fluids are affected by steam condensation that controls the outlet fumarolic temperatures 200 c and redox conditions are consistent with those inferred by the presence of the so2 h2s redox pair typical of fluids that have attained equilibrium in magmatic environment a comprehensive conceptual geochemical model describing the circulation pattern of the tupungatito hydrothermal magmatic fluids is proposed it includes fluid source regions and re equilibration processes affecting the different gas species due to changing chemical physical conditions as the magmatic hydrothermal fluids rise up toward the surface

gas geochemistry of the magmatic hydrothermal fluid reservoir in the copahue caviahue volcanic complex argentina abstract copahue volcano is part of the caviahue copahue volcanic complex ccvc which is located in the southwestern sector of the caviahue volcano tectonic depression argentina chile this depression is a pull apart basin accommodating stresses between the southern liquine ofqui strike slip and the northern copahue antinir compressive fault systems in a back arc setting with respect to the southern andean volcanic zone in this study we present chemical inorganic and organic and isotope compositions 13c co2 15n 3he 4he 40ar 36ar 13c ch4 d ch4 and d h2o and 18o h2o of fumaroles and bubbling gases of thermal springs located at the foot of copahue volcano sampled in 2006 2007 and 2012 helium isotope ratios the highest observed for a southern american volcano r ra up to 7 94 indicate a non classic arc like setting but rather an extensional regime subdued to asthenospheric thinning 13c co2 values from 8 8 to 6 8 vs v pdb 15n values 5 3 to 5 5 vs air and co2 3he ratios from 1 4 to 8 8 109 suggest that the magmatic source is significantly affected by contamination of subducted sediments gases discharged from the northern sector of the ccvc show contribution of 3he poor fluids likely permeating through local fault systems despite the clear mantle isotope signature in the ccvc gases the acidic gas species have suffered scrubbing processes by a hydrothermal system mainly recharged by meteoric water gas geothermometry in the h2o co2 ch4 co h2 system suggests that co and h2 re equilibrate in a separated vapor phase at 200 220 c on the contrary rock fluid interactions controlling co2 ch4 production from sabatier reaction and c3h8 dehydrogenation seem to occur within the hydrothermal reservoir at temperatures ranging from 250 to 300 c fumarole gases sampled in 2006 2007 show relatively low n2 he and n2 ar ratios and high r ra values with respect to those measured in 2012 such compositional and isotope variations were likely related to injection of mafic magma that likely triggered the 2000 eruption therefore changes affecting the magmatic system had a delayed effect on the chemistry of the ccvc gases due to the presence of the hydrothermal reservoir however geochemical monitoring activities mainly focused on the behavior of inert gas compounds n2 and he should be increased to investigate the mechanism at the origin of the unrest started in 2011

estimating the quality of landslide susceptibility models we present a landslide susceptibility model for the collazzone area central italy and we propose a framework for evaluating the model reliability and prediction skill the landslide susceptibility model was obtained through discriminant analysis of 46 thematic environmental variables and using the presence of shallow landslides obtained from a multi temporal inventory map as the dependent variable for statistical analysis by comparing the number of correctly and incorrectly classified mapping units it is established that the model classifies 77 0 of 894 mapping units correctly model fitting performance is investigated by comparing the proportion of the study area in each probability class with the corresponding proportion of landslide area we then prepare an ensemble of 350 landslide susceptibility models using the same landslide and thematic information but different numbers of mapping units this ensemble is exploited to investigate the model reliability including the role of the thematic variables used to construct the model and the model sensitivity to changes in the input data by studying the variation of the model s susceptibility estimate the error associated with the susceptibility assessment for each mapping unit is determined this result is shown on a map that complements the landslide susceptibility map prediction skill of the susceptibility model is then estimated by comparing the forecast with two recent event inventory maps the susceptibility model is found capable of predicting the newly triggered landslides a general framework for testing a susceptibility model is proposed including a scheme for ranking the quality of the susceptibility assessment

exploiting maximum entropy method and aster data for assessing debris flow and debris slide susceptibility for the giampilieri catchment north eastern sicily italy this study aims at evaluating the performance of the maximum entropy method in assessing landslide susceptibility exploiting topographic and multispectral remote sensing predictors we selected the catchment of the giampilieri stream which is located in the north eastern sector of sicily southern italy as test site on 1 october 2009 a storm rainfall triggered in this area hundreds of debris flow avalanche phenomena causing extensive economical damage and loss of life within this area a presence only based statistical method was applied to obtain susceptibility models capable of distinguishing future activation sites of debris flow and debris slide which where the main source of failure mechanisms for flow or avalanche type propagation the set of predictors used in this experiment comprised primary and secondary topographic attributes derived by processing a high resolution digital elevation model corine land cover data and a set of vegetation and mineral indices obtained by processing multispectral aster images all the selected data sources are dated before the disaster a spatially random partition technique was adopted for validation generating 50 replicates for each of the two considered movement typologies in order to assess accuracy precision and reliability of the models the debris slide and debris flow susceptibility models produced high performances with the first type being the best fit the evaluation of the probability estimates around the mean value for each mapped pixel shows an inverted relation with the most robust models corresponding to the debris flows with respect to the role of each predictor within the modelling phase debris flows appeared to be primarily controlled by topographic attributes whilst the debris slides were better explained by remotely sensed derived indices particularly by the occurrence of previous wildfires across the slope the overall excellent performances of the two models suggest promising perspectives for the application of presence only methods and remote sensing derived predictors copyright 2016 john wiley sons ltd

isotope composition of rain water well water and fumarole steam on the island of vulcano and their implications for volcanic surveillance abstract water samples from eight wells in the vulcano porto area and fumarole steam from the crater of vulcano southern italy were collected at monthly intervals over a two year period from february 1987 to january 1989 samples of bulk precipitation were also collected in three points at vulcano porto and vulcano piano island of vulcano and castroreale tyrrhenian coast of sicily again at monthly intervals the weighted mean isotopic composition of rain water on vulcano is d 32 and d 18 o 6 4 results for well waters tend to support the existence of at least two water bodies one of purely meteoric water and the other of brackish thermal water an intermediate water body probably the result of mixing of the other two was also recognized the isotope composition of fumarolic steam from the crater suggests the mixed contribution of both sea and rain waters although mixing is not the only process occurring the existence of a deep marine brine body is inferred characterized by d and 18o values more positive than those of mediterranean sea water a close relationship indicating common source effects is shown by temporal isotopic variations at some wells and the fumarolic steam wich may be used for volcano survey at distance from the active crater

spatial domain analysis of carbon dioxide from soils on vulcano island implications for co2 output evaluation abstract the carbon dioxide emissions of volcanoes have been targeted as effective contributors of co 2 to the atmosphere however different sources can be effective and active at the same time in the generation and release of co 2 in volcanic zones since isotopic fingerprinting of co 2 allows the precise identification of different sources coupling carbon isotope and co 2 flux measurements enables the evaluation of the mass contribution of each source to the carbon dioxide emissions this paper accounts for the first extensive spatial analysis of coupled measurements of carbon isotopologues of co 2 in the soil gases and co 2 fluxes discharged by soils on vulcano island an innovative method has been designed tested and fine tuned in the laboratory to measure 13 c co 2 values directly in field using a new type of laser based isotopologues analyzer namely a deltaray thermo fisher scientific the method can be used to determine the carbon isotope composition across the full range of co 2 concentrations in the soil gases 0 100 vol these data have been combined with measurements of the co 2 contents in the soil gases to distinguish co 2 from deep origins from co 2 of biogenic origin in the inhabited area of vulcano porto the method of evaluating the amount of deep origin co 2 in the soil gases is widely applicable in volcanic and geothermal zones for evaluation and monitoring purposes for both gas and volcanic hazards

vent temperature trends at the vulcano fossa fumarole field the role of permeability between 1994 and 2010 we completed 16 thermal surveys of vulcano s fossa fumarole field aeolian islands italy in each survey between 400 and 1 200 vent temperatures were collected using a thermal infrared thermometer from distances of 1 m the results show a general decrease in average vent temperature during 1994 2003 with the average for the entire field falling from 220 c in 1994 to 150 c by 2003 however between 2004 and 2010 we witnessed heating with the average increasing to 190 c by 2010 alongside these annual scale field wide trends we record a spatial re organisation of the fumarole field characterised by shut down of vent zones towards the crater floor matched by rejuvenation of zones located towards the crater rim heating may be expected to be associated with deflation because increased amounts of vaporisation will remove volume from the hydrothermal system gambino and guglielmino j geophys res 113 b07402 2008 however over the 2004 2010 heating period no ground deformation was observed instead the number of seismic events increased from a typical rate of 37 events per month during 1994 2000 to 195 events per month during 2004 2010 as part of this increase we noticed a much greater number of high frequency events associated with rock fracturing we thus suggest that the heating event of 2004 2010 was the result of changed permeability conditions rather than change in the heat supply from the deeper magmatic source within this scenario cooling causes shut down of lower sectors and re establishment of pathways located towards the crater rim causing fracturing increased seismicity and heat flow in these regions this is consistent with the zone of rejuvenation which lies towards and at the rim being the most favourable location for fracturing given the stress field of the fossa cone schopa et al j volcanol geotherm res 203 133 145 2011 it is also the most established zone having been active at least since the early twentieth century our data show the value of deploying multi disciplinary geophysical campaigns at degassing fumarolic hydrothermal systems this allows more complete and constrained understanding of the true heat loss dynamics of the system in the case study presented here it allows us to distinguish true heating from apparent heating phases while the former are triggered from the bottom up i e they are driven by increases in heat supply from the magmatic source the latter are triggered from the top down i e by changing permeability conditions in the uppermost portion of the system to allow more efficient heat flow over zones predisposed to fracturing

light hydrocarbons in hydrothermal and magmatic fumaroles hints of catalytic and thermal reactions volcanic gaseous mixtures emitted from active volcanoes frequently show variable amounts of saturated alkanes unsaturated alkenes and aromatic volatile hydrocarbons three major patterns of distributions can be recognized apparently related to the chemical physical environment of formation of the gas exhalations alkane rich low temperature gas emissions from recently active volcanic areas aromatic rich hydrothermal manifestations and alkene rich magmatic fumaroles on active volcanoes thermodynamic data together with theoretical and practical findings from the petroleum industry point to two main types of reactions occurring in these volcanic environments cracking and reforming cracking processes mainly caused by thermal effects occur when hydrocarbon bearing hydrothermal fluids enter and mix with a hot and dry rapidly rising magmatic gas phase the most probable products are light alkenes with carbon numbers decreasing with increasing reaction temperatures the presence of aromatic species in hydrothermal fluids can be linked to reforming processes catalysed by several possible agents such as smectites and zeolites generally present in the hydrothermally altered volcanic terranes and facilitated by long residence times in a hydrothermal envelope

identification of the changbaishan millennium b tm eruption deposit in the lake suigetsu sg06 sedimentary archive japan synchronisation of hemispheric wide palaeoclimate archives the b tm tephra dispersed during the highly explosive changbaishan millennium eruption ca 940 950 ce and a key marker layer within the greenland ice cores has now been identified in the lake suigetsu sg06 sedimentary sequence central japan the major element geochemistry of the volcanic glasses within this tephra layer are compared to a new glass dataset from the distal type locality tomakomai port hokkaido and other published millennium eruption b tm deposits to verify this correlation the discovery of the b tm tephra in the lake suigetsu record provides to date the most southerly identification of this ash and crucially the first direct tie point between this high resolution mid latitude palaeoclimate archive and the greenland ice cores these findings present significant encouragement for on going research into the tephrostratigraphy of east asia focusing on the identification of widely dispersed tephra layers which can facilitate the synchronisation of disparate palaeoclimate archives and thus enable the assessment of spatio temporal variations in past climatic change

exploring the effect of absence selection on landslide susceptibility models a case study in sicily italy abstract a statistical approach was employed to model the spatial distribution of rainfall triggered landslides in two areas in sicily italy that occurred during the winter of 2004 2005 the investigated areas are located within the belice river basin and extend for 38 5 and 10 3 km 2 respectively a landslide inventory was established for both areas using two google earth images taken on october 25th 2004 and on march 18th 2005 to map slope failures activated or reactivated during this interval geographic information systems gis were used to prepare 5 m grids of the dependent variables absence presence of landslide and independent variables lithology and 13 dem derivatives multivariate adaptive regression splines mars were applied to model landslide susceptibility whereas receiver operating characteristic roc curves and the area under the roc curve auc were used to evaluate model performance to evaluate the robustness of the whole procedure we prepared 10 different samples of positive landslide presence and negative landslide absence cases for each area absences were selected through two different methods i extraction from randomly distributed circles with a diameter corresponding to the mean width of the landslide source areas and ii selection as randomly distributed individual grid cells a comparison was also made between the predictive performances of models including and not including the lithology parameter the models trained and tested on the same area demonstrated excellent to outstanding fit auc 0 8 on the other hand predictive skill decreases when measured outside the calibration area although most of the landslides occur where susceptibility is high and the overall model performance is acceptable auc 0 7 the results also showed that the accuracy of the landslide susceptibility models is higher when lithology is included in the statistical analysis models whose absences were selected using random circles showed a significantly better performance when learning and validation samples were extracted from the same area whereas conversely no significant difference was observed when testing the models outside the training area

sg06 a fully continuous and varved sediment core from lake suigetsu japan stratigraphy and potential for improving the radiocarbon calibration model and understanding of late quaternary climate changes abstract the high potential of the varved sediments of lake suigetsu central japan to provide a purely terrestrial radiocarbon calibration model and a chronology of palaeoclimatic changes has been widely recognised for the last two decades however this potential has not been fully realised since the only available long sediment core from the lake sg93 was extracted from a single bore hole and was therefore interrupted by gaps of unknown duration between successive core sections in the summer of 2006 a new sediment core sg06 was recovered from the lake four separate boreholes were drilled and the parallel sets of cores recovered were found to overlap completely without gaps between segments this new record provides the ability to test existing atmospheric radiocarbon calibration models as well as to assess the scale of inter regional leads and lags in palaeoclimatic changes over the last glacial interglacial cycle multi disciplinary analyses from sg06 are still ongoing but a reliable description of the sedimentary sequence needs to be provided to the wider science community before major outputs from the project are released thereby allowing fully informed critical evaluation of all subsequent releases of data based on the sg06 record in this paper we report key litho stratigraphic information concerning the sg06 sediment core highlighting changes in the clarity of annual laminations varves with depth and possible implications for the mechanism of the climate change we also discuss the potential of the sg06 record to meet the fundamental goals of the inqua intimate project

volatile organic compounds vocs in soil gases from solfatara crater campi flegrei southern italy geogenic source s vs biogeochemical processes the chemical composition of volatile organic compounds vocs in soil gases from the solfatara crater campi flegrei italy was analyzed to investigate the effects of biogeochemical processes on gases discharged from the hydrothermal reservoir and released into the atmosphere through diffuse degassing the chemistry of fluids from fumarolic vents which represent preferential pathways for fluid uprising was also reported for comparison oxidation reduction and hydration dehydration reactions as well as microbial activity strongly affected the composition of c4 c9 alkanes alkenes s bearing compounds and alkylated aromatics especially in those sites where the soil showed relatively low permeability to uprising fluids other endogenous organic compounds such as benzene phenol and hydrofluorocarbons were able to transit through the soil almost undisturbed independently on the gas emission rate products of voc degradation mainly consisted of aldehydes ketones esters ethers and subordinately alcohols cyclic compounds revealed the occurrence of vocs produced within sedimentary formations overlying the hydrothermal reservoir whereas the presence of chlorofluorocarbons cfcs was likely related to air contamination the results of the present study highlighted the strict control of biogeochemical processes on the behavior of hydrothermal vocs that at least at a local scale may have a significant impact on air quality this information could be improved by laboratory experiments conducted at specific chemical physical conditions and in presence of different microbial populations

origins of etioporphyrins in sediments evidence from stable carbon isotopes abstract in samples of the julia creek and condor oil shales australia albian and early tertiary respectively etioporphyrin iii is significantly depleted in 13 c 4 relative to porphyrins derived from chlorophylls this isotopic difference suggests a large contribution from some independent source the haem group found in cytochromes derived from microbial sources is the most likely candidate

deep gases discharged from mud volcanoes of azerbaijan new geochemical evidence abstract this paper presents new geochemical data of hydrocarbon rich gases released from some mud volcanoes of azerbaijan methane is considerably the most abundant component of all the sampled gases which show d ch 4 and 13 c ch 4 values likely related to a dominant thermogenic source these gases are characterized by the presence of more than 20 different cyclic compounds with concentrations up to several mol mol a similar gas composition has recently been found to characterize many mud volcanoes of the northern apennines and sicily italy the data of the azerbaijan mud volcanoes corroborate the notion that cyclic compounds can be considered reliable tracers for hydrocarbon gas production at considerable depths and temperatures up to 120 150 c which correspond to a 6 5 8 3 km depth range assuming an average geothermal gradient of 18 c km this depth interval is consistent with both the depth of potential source rocks imaged seismically beneath some mud volcanoes and the results of previous estimates that used the 13 c 12 c values of methane and ethane such deep sourced gases and material fluidized clayey mass and rock fragments ascend into the core of anticlines and accumulate at shallower reservoirs where fold parallel outer arc faults or fold orthogonal fractures may penetrate and transfer the fluids to the surface finally the basically equivalent composition of the different hydrocarbon groups c 2 c 10 alkanes aromatics and cyclic determined in the gases sampled in both azerbaijan and italy manifests the lack of evident relationships between the chemistry of light hydrocarbons and the type of source rock

onset and termination of the late glacial climate reversal in the high resolution diatom and sedimentary records from the annually laminated sg06 core from lake suigetsu japan high resolution diatom sediment and pollen analyses of two sections from the annually laminated sg06 core from lake suigetsu were used to study the onset and termination of the late glacial climate reversal in central japan its broadly recognised counterpart is the younger dryas or greenland stadial 1 ca 12 85 11 65 cal kyr bp based on the ngrip ice core records our study suggests that accumulation of the analysed late glacial sediments occurred in a deep and relatively cold water meso eutrophic lake with a strong mixing regime and relatively high silica content combining these results together with available pollen based environmental reconstructions we suggest that climate cooling together with an intensified winter monsoon and thicker snow cover could influence changes in regional vegetation sedimentation processes and trophic status of the lake during the transition from the last interstadial to stadial around lake suigetsu a decrease in total pollen concentration and increase in fagus pollen percentage indicate local vegetation stress disturbances and suggest that cooling started at least 2 3 decades prior to the major shift in the inorganic sediment accumulation of detrital layers and in diatom assemblages change from aulacoseira ambigua to aulacoseira subarctica dominance which took about 10 years the transition from the last stadial to the holocene again shows that vegetation in the lake catchment area reacted first to the regional climate change i e to the weakening of the winter monsoon and decrease in winter snow accumulation the increase in the vegetation cover density and reduced volume of surface runoff associated with the decrease in melt water supply is likely responsible for the reduced soil erosion activity which caused the cessation in detrital layer accumulation and consequent decrease in the amount of nutrients brought to the lake and lowering of the water nutrient status the latter process finally influenced changes in the diatom assemblages including the return to dominance of a subarctica ca 30 years after the virtual disappearance of detrital layers from the sediment our results demonstrate the rapid response of the lake suigetsu system to the global cooling and subsequent warming and allow clear definition of the onset and termination of the late glacial climate reversal despite the fact that the lake system shows a more abrupt shift from the warm to cold and cold to warm environments than terrestrial records of vegetation demonstrate we do not see any delayed response of local vegetation to the climate change this last conclusion is of particular importance for application of the sg06 pollen record for quantitative climate reconstruction

preservation of organic matter and alteration of its carbon and nitrogen isotope composition during simulated and in situ early sedimentary diagenesis abstract the carbon and nitrogen isotope composition of organic matter has been widely used to trace biogeochemical processes in marine and lacustrine environments in order to reconstruct past environmental changes from sedimentary organic matter it is crucial to consider potential alteration of the primary isotopic signal by bacterial degradation in the water column and during early diagenesis in the sediments in a series of oxic and anoxic incubation experiments we examined the fate of organic matter and the alteration of its carbon and nitrogen isotopic composition during microbial degradation the decomposition rates determined with a double exponential decay model show that the more reactive fraction of organic matter degrades at similar rates under oxic and anoxic conditions however under oxic conditions the proportion of organic matter resistent to degradation is much lower than under anoxic conditions within three months of incubation the 13c of bulk organic matter decreased by 1 6 with respect to the initial value the depletion can be attributed to the selective preservation of 13c depleted organic compounds during anoxic decay the 15n values continuously decreased to about 3 below the initial value the decrease probably results from bacterial growth adding 15n depleted biomass to the residual material in the oxic experiment 15n values increased by more then 3 before decreasing to a value indistinguishable from the initial isotopic composition the dissimilarity between oxic and anoxic conditions may be attributed to differences in the type timing and degree of microbial activity and preferential degradation in agreement with the anoxic incubation experiments sediments from eutrophic lake lugano are on average depleted in 13c 1 5 and 15n 1 2 with respect to sinking particulate organic matter collected during a long term sediment trap study

biological and physical modification of carbonate system parameters along the salinity gradient in shallow hypersaline solar salterns in trapani italy abstract we investigated changes in the chemical characteristics of evaporating seawater under the influence of microbial activity by conducting geochemical analyses of the brines and evaporite sediments collected from solar salterns in trapani italy the microbial activity had a substantial effect on the carbonate system parameters dissolved inorganic carbon dic was substantially removed from the brine during the course of evaporation from the seawater to the point where calcium carbonate precipitates with an accompanying decrease in its carbon isotopic composition 13 c dic to as low as 10 6 although the removal of dic was due to calcium carbonate precipitation photosynthesis and the degassing of co 2 aq induced by evaporation the presence of 13 c depleted 13 c dic in ponds where calcium carbonate precipitates can be attributed to the dissolution of atmospheric co 2 because of intensive co 2 aq uptake by photosynthesis and or mineralization of organic matter by sulfate reduction in contrast 13 c dic increased up to 7 2 in the salinity range where halite precipitates which can be ascribed to the domination of the effect of degassing of co 2 aq under conditions with reduced microbial activity a gradual decrease in microbial activity was also reflected in compound specific 13 c of photosynthetic pigments isotopic fractionation associated with dic assimilation increased linearly as the evaporation proceeded indicating dic limited conditions within the microbial mats and gypsum crusts because of restricted dic diffusion from the overlying brine and or suppression of primary production at higher salinity

fumarolic gases at mombacho volcano nicaragua presence of magmatic gas species and implications for volcanic surveillance mombacho is a deeply dissected volcano belonging to the quaternary volcanic chain of nicaragua the southern historic collapse crater el crater currently hosts a fumarolic field with a maximum temperature of 121 c chemical and isotopic data from five gas sampling field campaigns carried out in 2002 2003 and 2005 highlight the presence of high temperature gas components e g so2 hcl and hf which indicate a significant contribution of juvenile magmatic fluids to the hydrothermal system feeding the gas discharges this is strongly supported by the mantle derived helium and carbon isotopic signatures although the latter is partly masked by either a sedimentary subduction related or a shallow carbonate component the observed chemical and isotopic composition of the mombacho fluids seems to indicate that this volcanic system although it has not experienced eruptive events during the last centuries can be considered active and possibly dangerous in agreement with the geophysical data recorded in the region systematic geochemical monitoring of the fumarolic gas discharges coupled with a seismic and ground deformation network is highly recommended in order to monitor a possible new eruptive phase

organic and inorganic geochemistry of low temperature gas discharges at the baia di levante beach vulcano island italy abstract discharge from subaereal and submarine gas vents of the baia di levante beach gases from the vulcano island were sampled for major and trace gas components in may and november 1995 chemical compositions and equilibrium calculations suggest three different groups of co 2 rich gas emissions depending on their distance from the la fossa crater 1 gas vents close to the faraglione area are characterised by high h 2 s contents high calculated equilibrium temperatures based on inorganic species and relatively high proportion of alkene compounds 2 gas vents close to vulcanello are characterised by low calculated equilibrium temperatures and low amounts of alkenes and 3 pontile sample has the highest equilibrium co 2 pressure up to 68 bars which may account for the observed absence of benzene the relative large variability of h 2 s in the baia di levante beach gas discharge may be attributed to either different interactions between iron sulphides and weakly acid waters or catalytic effect of elemental sulphur on the de hydrogenation of cyclo hexane thermodynamic calculations suggest that the main inorganic species and ch 4 may have re equilibrated at relatively shallow depth 10 200 m b s l and 30 600 m b s l for a lithostatic and hydrostatic pressure respectively the slow kinetics of reactions in the c n h 2 n c n h 2 n 2 systems with respect to that of ch 4 co co 2 may explain the observed propene propane ratios which can only be reached at reaction temperatures of 300 350 c this low speed of reactions can also explain the observed disequilibrium of c1 c4 alkanes

quantitative analysis of land surface topography land surface topography significantly affects the processes of runoff and erosion a system which determines slope aspect and curvature in both the down slope and across slope directions is developed for an altitude matrix also the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix a fortran 66 program performs the analysis

fossil pigments in paleoecology and paleolimnology abstract for the past several decades scientists have been examining the nature of sedimentary chlorophylls and carotenoids from freshwater lakes for their value in paleoecology and paleolimnology unaltered chlorophyll molecules are rarely preserved for long periods but the pheo derivatives and chlorophyllides are common throughout lake sedimentary columns carotenoids tend to preserve largely unaltered from their conditions in living plant membranes but degrade quickly to colorless derivatives when oxidized measurements of sedimentary pigment concentrations ratios of chlorophyll derivatives to carotenoids and diversity especially as regards prokaryote carotenoids are most commonly published this paper assesses the value of using sedimentary pigment data to provide paleoecological information on lake evolution and changing patterns of aquatic primary productivity factors that promote pigment preservation are contrasted to those that alter and cause destruction of organic molecules the value of fossil pigments is considered in ascertaining the sources of organic matter to sediments and for providing clues to the changing diversity of aquatic flora both rooted and planktonic consideration is given to recent investigations that have sought information from sedimentary pigments on the onset and intensity of cultural eutrophication both in individual lakes and on a regional basis and in the monitoring of progress toward lake restoration a special case is made for the value of sampling meromictic lakes in addition this review provides information on the limitations of the sampling procedures laboratory techniques and interpretation of results discussion is made of the most valuable and easily obtainable data that can provide reliable comparable and reproducible results special consideration is given to the value of the pigment data in supplementing additional paleoecological indicators such as sedimentary pollen grains zooplankton and various other sedimentary bio and geochemical products

chemical composition of fumarolic gases and spring discharges from el chichon volcano mexico causes and implications of the changes detected over the period 1998 2000 abstract since the march april 1982 eruption of el chichon volcano intense hydrothermal activity has characterised the 1 km wide summit crater this mainly consists of mud and boiling pools fumaroles which are mainly located in the northwestern bank of the crater lake during the period 1998 2000 hot springs and fumaroles discharging inside the crater and from the southeastern outer flank agua caliente were collected for chemical analyses the observed chemical fluctuations suggest that the physico chemical boundary conditions regulating the thermodynamic equilibria of the deep rock fluid interactions have changed with time the chemical composition of the lake water characterised in the period 1983 1997 by high na cl ca 2 and so 4 2 contents experienced a dramatic change in 1998 1999 turning from a na cl to a ca 2 so 4 2 rich composition in june 2000 a relatively sharp increase in na and cl contents was observed at the same time so 2 h 2 s ratios and h 2 and co contents in most gas discharges increased with respect to the previous two years of observations suggesting either a new input of deep seated fluids or local variations of the more surficial hydrothermal system migration of gas manifestations enhanced number of emission spots and variations in both gas discharge flux and outlet temperatures of the main fluid manifestations were also recorded the magmatic hydrothermal system of el chichon is probably related to interaction processes between a deep magmatic source and a surficial cold aquifer an important role may also be played by the interaction of the deep fluids with the volcanic rocks and the sedimentary limestone and evaporites basement the chemical and physical changes recorded in 1998 2000 were possibly due to variations in the permeability of the conduit system feeding the fluid discharges at surface as testified by the migration of gas and water emanations two different scenarios can be put forward for the volcanic evolution of el chichon 1 build up of an infra crater dome that may imply a future eruption in terms of tens to hundreds of years 2 minor phreatic phreatomagmatic events whose prediction and timing is more difficult to constrain this suggests that unlike the diminished volcanic activity at el chichon after the 1982 paroxistic event the volcano hydrothermal fluid discharges need to be more constantly monitored with regular and more frequent geochemical sampling and at the same time a permanent network of seismic stations should be installed

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research