growth and collapse of the reunion island volcanoes this work presents the first exhaustive study of the entire surface of the reunion island volcanic system the focus is on the submarine part for which a compilation of all multibeam data collected during the last 20 years has been made different types of submarine features have been identified a coastal shelf debris avalanches and sedimentary deposits erosion canyons volcanic constructions near the coast and seamounts offshore criteria have been defined to differentiate the types of surfaces and to establish their relative chronology where possible debris avalanche deposits are by far the most extensive and voluminous formations in the submarine domain they have built four huge submarine bulges to the east north west and south of the island they form fans 20 30 km wide at the coastline and 100 150 km wide at their ends 70 80 km offshore they were built gradually by the superimposition and or juxtaposition of products moved during landslide episodes involving up to several hundred cubic kilometers of material about 50 individual events deposits can be recognized at the surface the landslides have recurrently dismantled piton des neiges les alizes and piton de la fournaise volcanoes since 2 ma about one third are interpreted as secondary landslides affecting previously emplaced debris avalanche deposits on land landslide deposits are observed in the extensively eroded central area of piton des neiges and in its coastal areas analysis of the present day topography and of geology allows us to identify presumed faults and scars of previous large landslides the submarine bulges are dissected and bound by canyons up to 200 m deep and 40 km long filled with coarse grained sediments and generally connected to streams onshore a large zone of sedimentary accumulation exists to the north east of the island it covers a zone 20 km in width extending up to 15 km offshore volcanic constructions are observed near the coast on both piton des neiges and piton de la fournaise volcanoes and are continuations of subaerial structures individual seamounts are present on the submarine flanks and the surrounding ocean floor a few seem to be young volcanoes but the majority are probably old eroded seamounts this study suggests a larger scale and frequency of mass wasting events on reunion island compared to similar islands the virtual absence of downward flexure of the lithosphere beneath the island probably contributes to this feature the increased number of known flank failure events has to be taken into consideration when assessing hazards from future landslides in particular the probability of landslide generated tsunamis

possible electrokinetic origin of large magnetic variations at la fournaise volcano abnormal time variations of the geomagnetic field related to volcanic activity have been reported for several decades1 10 two main candidates have been considered for the source mechanism of these volcanomagnetic variations piezomagnetism and electro kinetic effects we considered both of these mechanisms in our attempts to interpret the most spectacular volcanomagnetic variations observed on piton de la fournaise volcano reunion island 11 but now new analysis of the latest data which covers a time span of more than three years leads us to think that water circulation is the main agent of the strong magnetic signals observed on the volcano in addition to the signals that we correlated with the volcano activity11 12 longer period components also exist as shown here with amplitudes and characteristics that have not been reported before we propose that these magnetic variations are generated by electrokinetic effects in which case the water circulation system into this massif would be a sensor for detecting stress changes linked to the volcano activity

pigment preservation and remineralization in oxic coastal marine sediments abstract complex mixtures of sedimentary chlorophyll degradation products were measured using high performance liquid chromatography hplc in 210 pb dated box and piston core sediments sediments were collected from dabob bay washington a coastal marine fjord conducive to studies yielding an understanding of the remineralization and diagenesis of organic carbon greater than 99 of the pheopigment flux out of the water column does not accumulate in the top 2 cm of sediment surface sediment pigment profiles indicate that pheophorbides are the dominant pheopigments observed with concentrations decreasing rapidly with depth concentrations of chlorophyll c derivatives also decrease rapidly but ratios of a c pheopigments remain within ranges reported for natural and cultured phytoplankton sharp pheopigment concentration decreases within the bioturbated surface sediments as defined by 210 pb activities were modeled using a one dimensional mixing model the in situ pheopigment decomposition rate corrected for bioturbation and sediment accumulation corresponds to an approximate half life of 40 days sedimentary humic acid fulvic acid and residual humin associated pheopigments in sediments which had been previously acetone extracted to remove the lipophilic pheopigment fraction were typed by chromic acid oxidation and release of pyrrole derived maleimides this humic associated pyrrole derived nitrogen while a small fraction of total sedimentary or humic nitrogen accounted for 16 75 of the total sedimentary pheopigment accumulation and may be significant in understanding the diagenetic fate and transformation of pheopigments to petroporphyrins

glacial interglacial variations in carbon cycling revealed by molecular and isotope stratigraphy of lake nkunga mt kenya east africa abstract the lipid content n alkanes n alkanols n alkanoic acids and the 13c values of these lipids were measured in nineteen sediment samples taken from a 21 18 m long core from lake nkunga a high altitude 1820 m a s l freshwater lake situated in the montane rain forest on mt kenya the record spans the early last glacial marine isotope stages 5a to 4 and the late holocene 1030 45 14c yr bp to the present day the intervening hiatus spans the last glacial maximum and the early to mid holocene the molecular biogeochemical results are interpreted in terms of past changes in climate vegetation and atmospheric co2 concentration three different sources of organic matter input were identified from the n alkyl lipids namely terrestrial plants aquatic plants and algae unusual distribution patterns of dominant mid chain length n alkanes c23 25 n alkanols c22 24 and n alkanoic acids c22 24 are attributed to aquatic macrophytes an 11 decrease in bulk carbon isotope values between the sediments of early glacial 17 and late holocene age 28 is also apparent in the individual homologues of the n alkyl lipids the observed isotopic shift in terrestrial higher plant biomarkers is similar to that observed in nearby sacred lake and is consistent with an expansion of c4 grasses or sedges during the early glacial the corresponding vegetation was a dry montane juniper olive forest with a grassy understorey representing cold dry conditions with lower co2

unrest signals after 46 years of quiescence at cumbre vieja la palma canary islands abstract monogenetic eruptions are the most common volcanic activity in the world however unrest monitoring data are scarce due to the long intervening quiescence periods this study analyzes unrest signals recorded in one of the largest monogenetic fields in the canary islands cumbre vieja la palma two seismic swarms were registered in october 2017 and february 2018 with b values of 1 6 0 1 and 2 3 0 2 respectively suggesting an intense magmatic fluids contribution gas and or magma both swarms were linked to changes in gas emissions increases in hydrogen concentration and r ra c up to 7 52 0 05 were recorded before the first swarm at the sampling point closest to where seismicity was located indicating a deep gas input after the second swarm increases in r ra c and thoron soil concentration were recorded at two locations this dataset is compatible with a stalled magmatic intrusion at ca 25 km depth with an estimated volume between 5 5 10 4 km3 and 3 10 2 km3

magnetotelluric monitoring of a fluid injection example from an enhanced geothermal system 1 enhanced geothermal systems egs are on the verge of becoming commercially viable for power production where advancements in subsurface characterization are imperative to develop egs into a competitive industry theory of an egs is simple pump fluids into thermally enhanced lithology and extract the hot fluids to produce energy one significant complication in egs development is estimating where injected fluids flow in the subsurface micro seismic surveys can provide information about where fractures opened but not fracture connectivity nor fluid inclusion electromagnetic methods are sensitive to conductivity contrasts and can be used as a supplementary tool to delineate reservoir boundaries in july 2011 an injection test for a 3 6 km deep egs at paralana south australia was continuously monitored by both micro seismic and magnetotellurics mt presented are the first results from continuous mt measurements suggesting transient variations in subsurface conductivity structure generated from the introduction of fluids at depth can be measured furthermore phase tensor representation of the time dependent mt response suggests fluids migrated in a ne direction from the injection well results from this experiment supports the extension of mt to a monitoring tool for not only egs but other hydraulic stimulations

deformation between 1989 and 1997 at piton de la fournaise volcano retrieved from correlation of panchromatic airborne images we processed two panchromatic airborne images in the attempt to measure deformation on piton de la fournaise volcano between 1989 and 1997 piton de la fournaise erupted three times during 1989 1997 with fissures opening near dolomieu summit crater during this period no synthetic aperture radar interferometry data were available and only few geodetic points surveyed the summit crater we therefore apply for the first time the subpixel image correlation technique on airborne images for monitoring ground deformation on piton de la fournaise volcano correlogram analysis reveals cumulative deformation in the summit area we observe ese spreading of the summit caused by the inflation deflation cycle during 1989 1997 we calculated relative ground displacement along both sides of the main eruptive fissures finding a maximum of 1 8 0 42 m opening direct comparison between deformation retrieved by correlation and available geodetic data at four locations shows qualitative agreement we demonstrate the potential of subpixel image correlation technique using panchromatic airborne images for deformation monitoring on volcanoes we also illustrate the capability of this technique for remote lava flow mapping

bounded influence magnetotelluric response function estimation author posting blackwell 2004 this article is posted here by permission of blackwell for personal use not for redistribution the definitive version was published in geophysical journal international 157 2004 988 1006 doi 10 1111 j 1365 246x 2004 02203 x

archaeal tetraether membrane lipid fluxes in the northeastern pacific and the arabian sea implications for tex86 paleothermometry the newly introduced temperature proxy the tetraether index of archaeal lipids with 86 carbon atoms tex86 is based on the number of cyclopentane moieties in the glycerol dialkyl glycerol tetraether gdgt lipids of marine crenarchaeota the composition of sedimentary gdgts used for tex86 paleothermometry is thought to reflect sea surface temperature sst however marine crenarchaeota occur ubiquitously in the world oceans over the entire depth range and not just in surface waters we analyzed the gdgt distribution in settling particulate organic matter collected in sediment traps from the northeastern pacific ocean and the arabian sea to investigate the seasonal and spatial distribution of the fluxes of crenarchaeotal gdgts and the origin of the tex86 signal transported to the sediment in both settings the tex86 measured at all trap deployment depths reflects sst in the arabian sea analysis of an annual time series showed that the sst estimate based on tex86 in the shallowest trap at 500 m followed the in situ sst with a 1 to 3 week time delay likely caused by the relatively low settling speed of sinking particles this revealed that the gdgt signal that reaches deeper water is derived from the upper water column rather than in situ production of gdgts the gdgt temperature signal in deeper traps at 1500 m and 3000 m did not show a seasonal cyclicity observed in the 500 m trap but rather reflected the annual mean sst this is probably due to a homogenization of the tex86 sst signal carried by particles as they ultimately reach the interior of the ocean our data confirm the use of tex86 as a temperature proxy of surface ocean waters

volcanomagnetic evidence of the magmatic intrusion on 13thmay 2008 etna eruption 1 during the onset of 2008 volcanic crisis at mt etna the near real time magnetic data provided a continuous updating of the volcano activity state on the northern flank on the morning of 13th may 2008 significant local magnetic field changes marked the resumption of the eruptive activity characterized by the opening of a fracture field on the northern flank and an eruptive fissure in the valle del bove in agreement with the northward propagation of seismic events magnetic signals at 5 stations in the summit area revealed a nearly nnw sse oriented magmatic intrusion which started at about 9 00 gmt propagated northward for about 2 km and stopped at 14 00 gmt before reaching the north east rift magnetic variations with amplitude ranging between 1 8 nt and 6 5 nt are consistent with those calculated from piezomagnetic models where stress induced changes in rock magnetization are produced by the magmatic intrusion

dynamic dyke propagation deduced from tilt variations preceding the march 9 1998 eruption of the piton de la fournaise volcano during the hour preceding the march 9 1998 eruption of the piton de la fournaise volcano the deformation network of the observatory recorded some large deformations in the summit area a broadband seismic station of the geoscope global network rer is located about 8 km away from the summit of the volcano signals from that station may be interpreted as tilt changes the combination of the above two kinds of signals allows by using a tensile fault model to constrain the geometry as well as some characteristics volume propagation velocity of the dyke that intruded the summit area during the hour preceding the beginning of eruptive activity

location of tremor sources and estimation of lava output using tremor source amplitude on the piton de la fournaise volcano 2 estimation of lava output abstract we propose several relations for estimating the amounts of lava emitted during eruptions of the piton de la fournaise volcano based on the use of tremor source amplitude sources for eruption tremor are located in several frequency bands with a location method based on the use of seismic amplitudes corrected for recording site effects sources are usually found at shallow depth and close to the eruptive vents suggesting that tremor is directly generated by the eruptive activity simultaneously with the location of the tremor sources our program gives the source amplitude of the phenomenon we assume a linear or a quadratic relation between the lava output and the tremor source amplitude both relations are calibrated using data for the march 1998 eruption and tested using the volumes emitted during the july and september 1999 and february 2000 eruptions we found that the 5 10 hz frequency band gives lava output much higher than for lower frequencies suggesting that for that band the tremor generation depends on the eruption site in addition to the lava output or that tremor at those frequencies is not directly caused by the outflow of lava but maybe rather by gas the best estimations are obtained using the quadratic relation for frequencies below 5 hz with an agreement better than 15 with the field observations for the july and september 1999 eruptions and 30 for the february 2000 eruption our results show that the cumulative amplitude of tremor recorded during eruptions of the piton de la fournaise is directly related to the amounts of lava erupted

wet phases in the sahara sahel region and human migration patterns in north africa the carbon isotopic composition of individual plant leaf waxes a proxy for c3 vs c4 vegetation in a marine sediment core collected from beneath the plume of sahara derived dust in northwest africa reveals three periods during the past 192 000 years when the central sahara sahel contained c3 plants likely trees indicating substantially wetter conditions than at present our data suggest that variability in the strength of atlantic meridional overturning circulation amoc is a main control on vegetation distribution in central north africa and we note expansions of c3 vegetation during the african humid period early holocene and within marine isotope stage mis 3 50 45 ka and mis 5 120 110 ka the wet periods within mis 3 and 5 coincide with major human migration events out of sub saharan africa our results thus suggest that changes in amoc influenced north african climate and at times contributed to amenable conditions in the central sahara sahel allowing humans to cross this otherwise inhospitable region

bacteriohopanepolyols as tracers for continental and marine organic matter supply and phases of enhanced nitrogen cycling on the late quaternary congo deep sea fan abstract few studies have successfully identified bacteriohopanepolyols bhps in continuous sedimentary records older than 100 ka here we expand significantly on previous work and report high resolution records of a variety of fully functionalised bhps from odp site 1075 in the congo deep sea fan bhps are present throughout the core in sediments up to ca 1 2 ma including composite and unsaturated homologues although adenosylhopane a proposed tracer for soil organic matter input seems to undergo significant diagenesis with increasing depth below 65 m below the sea floor mbsf most bhps appear to be relatively resilient to degradation highlighting their potential as sedimentary tracers for past bacterial population distributions an unusual unsaturated bht cyclitol ether is present in high concentration between 500 and 600 ka and is interpreted as a possible biomarker for nitrogen fixing trichodesmium cyanobacteria this previously unrecognised ecosystem change may have been partially driven by a decrease in nutrient supply to surface waters resulting in more intense pelagic n fixation

occurrence of novel monocyclic alkenes from diatoms in marine particulate matter and sediments abstract widely occurring alkenes reported in sediments from around the globe but which previously had unknown identities and sources have now been assigned they include a novel monocyclic c 25 triene and novel c 30 monocyclic tetra and pentaenes recently these compounds have been shown to be biosynthesised by some strains of the widespread planktonic diatom rhizosolenia setigera and this appears to be the likely source of the alkenes in the marine environment the hydrocarbons were identified by comparison of the gas chromatographic retention data and mass spectra of the sedimentary alkenes isolated from the arabian sea peru upwelling region and cariaco trench with data for the pure isolated alkenes from r setigera the compounds co occur with well known diatomaceous 7 20 highly branched isoprenoid haslenes and rhizenes in all of these environments but were absent from sediments from the black sea even though 5 haslenes were abundant in the latter sediments these differences possibly reflect the different diatom species contributing alkene lipids to each sedimentary environment the newly identified compounds may be further useful biological markers of diatom inputs to sediments

temperature dependency of long chain alkenone distributions in recent to fossil limnic sediments and in lake waters distribution patterns of c37 and c38 polyunsaturated long chain alkenones lcas serve as proxies for the determination of paleotemperatures for marine surface waters we studied recent subrecent and late glacial holocene sediments from germany austria russia and the u s to test for a correspondence between lca distribution and surface water temperature in limnic systems previously reports of lca occurrence were restricted to sediments of 6 wide distributed freshwater and alkaline lakes in this study 13 of 27 investigated lakes contained lcas in surface sediments with concentrations varying between 12 to 205 g g toc late glacial to holocene sediment sequences from lake steisslingen and lake wummsee germany lake pichozero russia and brush lake u s a contained abundant lcas with averaged concentrations of 33 to 7536 g g toc for the first time we observed the occurrence of lcas within in the water column of oligotrophic lake stechlin ne germany alkenones were restricted to the zone of maximum chlorophyll concentration within the water column indicating that lcas have a biosynthetic origin and can be attributed to phototrophic micro algae attempts to identify the producing organism however were not successful culture experiments allow various phytoplankton to be excluded as producers alkenone producing algae are evidently of small size hindering microscopical identification lcas commonly occur in high concentrations in late glacial sediments mainly during the cold period of the younger dryas whereas the holocene usually is devoid of polyunsaturated alkenones the episodic occurrence of lcas restricts their utility as proxies for continuous geological records furthermore lack of microscopical verification and the episodic distribution allow for different producers of unsaturated alkenones in recent and late glacial sediments an empirical relationship between lca distribution and temperature was observed in fossil sediments from lake steisslingen there is a good correspondence between uk37 and the temperature controlled 18o isotope ratio of lake chalk comparison of lca patterns obtained from the uppermost centimetres of lake sediments with averaged summer surface water temperatures of the lakes studied demonstrates a trend of covariance r2 uk 37 0 90 uk37 0 67 n 9 hence the same mechanism that causes temperature dependence of lca patterns in marine systems might be effective in limnic settings identification of alkenone producers and their culture under controlled temperature are still mandatory before lcas can be routinely applied as paleotemperature proxy in limnic systems

a north to south transect of holocene southeast atlantic continental margin sediments relationship between aerosol transport and compound specific δ13c land plant biomarker and pollen records 1 we examined near surface late holocene deep sea sediments at nine sites on a north south transect from the congo fan 4 s to the cape basin 30 s along the southwest african continental margin contents distribution patterns and molecular stable carbon isotope signatures of long chain n alkanes c27 c33 and n alkanols c22 c32 are indicators of land plant vegetation of different biosynthetic types which can be correlated with concentrations and distributions of pollen taxa in the same sediments calculated clusters of wind trajectories and satellite aerosol index imagery afford information on the source areas for the lipids and pollen on land and their transport pathways to the ocean sites this multidisciplinary approach on an almost continental scale provides clear evidence of latitudinal differences in lipid and pollen composition paralleling the major phytogeographic zonations on the adjacent continent dust and smoke aerosols are mainly derived from the western and central south african hinterland dominated by deserts semi deserts and savannah regions rich in c4 and cam plants the northern sites congo fan area and northern angola basin which get most of their terrestrial material from the congo basin and the angolan highlands may also receive some material from the chad region very little aerosol from the african continent is transported to the most southerly sites in the cape basin as can be expected from the present position of the phytogeographic zones the carbon isotopic signatures of the n alkanes and n alkanols both become isotopically more enriched in 13c from north to south the results of the study suggest that this combination of pollen data and compound specific isotope geochemical proxies can be effectively applied in the reconstruction of past continental phytogeographic developments

automatic fuzzy logic recognition of anomalous activity on long geophysical records application to electric signals associated with the volcanic activity of la fournaise volcano reunion island abstract for the mitigation of natural hazards geophysicists install more and more sensors in the field to enlarge the monitoring networks in volcanic and seismogenic areas unambiguous results can be obtained only if many parameters are continuously recorded and processed over very long time series several years overlapping an eruption or an earthquake on the other hand recent research has led to a sharp increase in the sampling rate of the data acquisition systems therefore manual data processing with a first step visual expertise becomes more and more difficult time consuming and at the same time less objective this paper introduces an alternative to manual signal recognition it includes the development of a specific anomaly recognition algorithm called difference recognition algorithm for signals dras and its application to self potential sp records obtained on the 10 channels of the electric stations located on la fournaise volcano before during and after the eruption of march 9 1998 the algorithm starts with the construction of rectification functionals examples are energy length zero crossing rate from the data over a running characteristic time window application of fuzzy set measures over the calculated functionals allows dras to identify in particular well spaced and time organised sp oscillations observed on the volcano up to 2 weeks before the march 9 1998 eruption based on the results obtained one can conclude that electric signals in the ulf band frequency

electrical tomography of la soufriere of guadeloupe volcano field experiments 1d inversion and qualitative interpretation the soufriere of guadeloupe lava dome consists of several 3d domains of relatively unaltered massive andesite separated by major radial fractures that reach at least up to about half of the dome s height more than 20 000 geo electrical measurements made on the top and the flanks of the lava dome are used to construct the first geophysical image of the internal structure of this active volcano the main features of the apparent conductivity structure of the lava dome are high conductivity regions associated with the strongly altered material of present and fossil hydrothermal zones local 1d inversions of data subsets belonging to regions where the geological structure is supposed laterally invariant confirm the structures observed in the pseudo sections the relatively stable units lie above a basal inclined layer of highly conductive geological materials interpreted to be more altered and thus characterised by reduced internal friction and probably increased pore pressure past and current hydrothermal fluid circulation through these fractures has promoted rock alteration and particularly along the base of the dome that likely contributes to the instability of parts of the edifice

structure of reunion island indian ocean inferred from the interpretation of gravity anomalies abstract reunion is a volcanic edifice whose origin is related to a hot spot in the indian ocean only 3 of its volume is emergent many geological and geophysical studies were carried out on reunion island during the 1980 s but few of them allow study of the internal structure of the edifice several gravity surveys have been carried out on the island since 1976 and we have compiled the available data set the lack of data on the western side of the island led us to conduct a regional survey in 1993 to obtain a more homogeneous distribution of the stations computation of bouguer anomalies for different correction densities accounts for the variable density of the rocks constituting the edifice and provides a distribution of gravity anomalies interpreted as dense bodies of intrusive rocks inside the edifice two very large intrusive complexes can be unambiguously recognised one beneath piton des neiges and one beneath the grand brule area both have been penetrated by geothermal exploration drill holes and the first is also known from outcrop observations 2 5d simple models were constructed to reveal the geometry and extent of the buried intrusives they are deeply rooted extending several kilometres below sea level and extensive 20 25 km long and 10 13 km wide for the piton des neiges complex 12 15 km long and some kilometres wide for the grand brule complex the development of such complexes implies that the activity of the two volcanic centres was long lasting and remained stable while the volcanoes were growing the grand brule complex has been interpreted as relics of an old volcano named alizes volcano the interpretation of the gravity maps suggests the presence of a ridge of dense rocks to the north of the axis joining the centres of piton des neiges and piton de la fournaise volcanoes by analogy with the other structures 2 5d models show that this structure would culminate between 0 and 1 km below sea level and be 15 km wide this complex induces a maximum anomaly in takamaka valley and we thus propose to name it takamaka volcano no geological evidence of the nature of these dense rocks is available but the ridge coincides with structures revealed by magnetic and seismic data interpretation of the bouguer anomaly maps suggests that the inner gravity structure of piton de la fournaise is not characterised by the presence of a voluminous dense body but probably by more restricted concentrations of dense rocks some structures can be recognised along the present ne and se rift zones and in the previous central part of piton de la fournaise to the west of the present summit the recent eastward migration of the centre of activity of piton de la fournaise accounts for the lack of a large positive anomaly beneath the active craters

resistivity and self potential changes associated with volcanic activity the july 8 2000 miyake jima eruption japan abstract the miyake jima volcano abruptly erupted on july 8 2000 after 17 years of quiet and gave birth to a crater 1 km in diameter and 250 m deep this expected unrest was monitored during the years 1995 2000 by electromagnetic methods including dc resistivity measurements and self potential sp surveys beneath the 2500 yr old hatcho taira summit caldera audio magnetotelluric soundings made in 1997 98 identified a conductive medium 200 500 m thick within the 50 m isoline located at a few hundred metres depth it was associated with the active steady state hydrothermal system centred close to the 1940 cone and extending southward a dc resistivity meter set in a schlumberger array with 600 1000 and 1400 m long injection lines evidenced strong resistivity changes between september 1999 and july 3 2000 in the vicinity of the newly formed crater the apparent resistivity has reached about three times its initial values on the 1400 m long line and has lowered to about 20 on the 600 m line just prior to the july 8 2000 eruption sp mapping made inside the summit hatcho taira caldera revealed negative anomalies where positive ones had occurred during the previous tens of years the largest negative anomaly 225 mv in amplitude mainly took place above the 1940 cone which collapsed in the crater formation a permanent 1 km long sp line across the caldera suggests accelerating changes during the 3 months preceding the eruption on a larger scale the comparison between 1995 and 2000 surveys has shown a global increase of the hydrothermal activity beneath the volcano its source could have been 250 m to the south of the crater these observations suggest that the hydrothermal system was slowly disturbed in the months preceding the eruption while drastic changes have occurred during the 2 weeks before the summit collapse when tectonic and volcanic swarms have appeared

sedimentary pigments as markers for environmental change in an antarctic lake abstract fossil pigments were identified in a sediment core from kirisjes pond a small lake in the larsemann hills east antarctica using reversed phase hplc and lc ms ms chlorophyll a and b derived components indicate the presence of oxygenic primary producers steryl chlorin esters provide evidence of grazing while shifts in their esterifying sterol composition record changes in the primary producer community bacteriochlorophyll c and d derived components indicative of photic zone anoxia were identified with structural variations including extensive alkylation in the macrocycle up to c 6 the pigment distribution reveals a change from oxygenated freshwater to a stratified water body with development of photic zone anoxia this coincides with a marine incursion identified from diatom records and is followed by re isolation and reversion to oxygenated freshwater conditions

long chain alkenones in qinghai lake sediments abstract long chain methyl and ethyl alkenones c 37 c 40 containing two to four double bonds have been detected in sediments from qinghai lake china this is the first report of the alkenones in lake sediments deposited under a variety of salinity conditions where the lake has not encountered any marine incursions the presence of the alkenones suggests the presence of prymnesiophyceae in the lake which may have reached the lake via eolian transportation or seabirds sediment samples from the more saline areas of the lake contained higher concentrations of the more highly unsaturated compounds widespread use of these compounds as paleotemperature indicators in marine sediments introduces the possibility of extrapolating this approach to lacustrine environments if appropriate calibrations can be undertaken

abrupt holocene climate change as an important factor for human migration in west greenland west greenland has had multiple episodes of human colonization and cultural transitions over the past 4 500 y however the explanations for these large scale human migrations are varied including climatic factors resistance to adaptation economic marginalization mercantile exploration and hostile neighborhood interactions evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of holocene temperature derived from ice cores atop the greenland ice sheet here we present high resolution records of temperature over the past 5 600 y based on alkenone unsaturation in sediments of two lakes in west greenland we find that major temperature changes in the past 4 500 y occurred abruptly within decades and were coeval in timing with the archaeological records of settlement and abandonment of the saqqaq dorset and norse cultures which suggests that abrupt temperature changes profoundly impacted human civilization in the region temperature variations in west greenland display an antiphased relationship to temperature changes in ireland over centennial to millennial timescales resembling the interannual to multidecadal temperature seesaw associated with the north atlantic oscillation

major changes in glacial and holocene terrestrial temperatures and sources of organic carbon recorded in the amazon fan by tetraether lipids the amazon basin is a major component of the global carbon and hydrological cycles a significant natural source of methane and home to remarkable biodiversity and endemism reconstructing past climate changes in the amazon basin is important for a better understanding of the effect of such changes on these critical functions of the basin using a novel biomarker proxy based on the membrane lipids of soil bacteria with a new regional calibration we present a reconstruction of changes in mean annual air temperatures for the amazon catchment during the last 37 kyr b p biomarkers were extracted from ocean drilling program sediment core odp942 recovered from the amazon fan the amazon fan is a major depository for terrestrial sediments with the advantage that the terrestrial material captured reflects a regional integration of the whole river catchment the reconstructed tropical amazonian temperatures were similar to 5 degrees c cooler at the last glacial maximum similar to 21 degrees c compared to modern values similar to 26 degrees c this is in agreement with previous estimates of tropical continental temperatures in the tropical amazon basin and tropical africa during the last glacial maximum moreover we also illustrate how the soil bacterial membrane lipid record reveals major changes in basin dynamics and sediment provenance during the glacial holocene transition impacting the biomarker reconstructions from similar to 11 kyr onward

possible algal origin of long chain odd n alkanes in immature sediments as revealed by distributions and carbon isotope ratios a pliocene oil shale pula hungary a c3 plant triticum aestivum and a c4 plant zea mays were compared using isotopic composition of bulk organic matter along with distributions and individual carbon isotope ratios of n alkanes from organic extracts the microalga botryococcus braunii a race was thus shown to be the main source of the predominant 27 29 and 31 n alkanes of pula sediment therefore the dominance of odd carbon numbered n alkanes in the range c25 35 in extracts from immature sediments shall not be systematically assigned to higher plant contribution but algal input is also possible in fact the long chain n alkanes with an odd predominance previously observed in extracts of various immature sediments are likely to be derived at least partially from algae

constraints on the application of the mbt cbt palaeothermometer at high latitude environments svalbard norway abstract branched glycerol dialkyl glycerol tetraethers gdgts are membrane lipids of unknown bacteria that are ubiquitous in soil and peat two indices based on the distribution of these lipids in soils the cyclization of branched tetraethers cbt and the methylation of branched tetraethers mbt indices have been shown to correlate with soil ph and mean annual air temperature mat and soil ph respectively and can be used to reconstruct mat in palaeoenvironments to verify the extent to which branched gdgts in marine sediments reflect the distribution pattern on land and whether these proxies are applicable for palaeoclimate reconstruction in high latitude environments with a mat of

3 d modeling of the deep electrical conductivity of merapi volcano central java integrating magnetotellurics induction vectors and the effects of steep topography we derive a 3 d model of the electrical conductivity structure of merapi volcano in central java from magnetotelluric mt sounding curves and geomagnetic induction vectors topography has been considered explicitly in the model the overall magnitude of the conductivities is constrained by mt measurements while lateral variations are mainly derived from geomagnetic induction vectors the resulting model is consistent with both the mt transfer functions apparent resistivities and phases and the magnetic transfer functions induction vectors the final model consists of two 3 d structures i e a central conductor and a second conductor lying to the southwest of the summit the high conductivity material is probably hot saline water as suggested by position and lateral extent of the high conductivity material

mapping the geometry of volcanic systems with magnetotelluric soundings results from a land and marine magnetotelluric survey performed during the 2018 2019 mayotte seismovolcanic crisis abstract a major seismovolcanic crisis has afflicted the islands of mayotte comoros archipelago since may 2018 although the origin is debated magnetotellurics mt which is sensitive to hydrothermal and or magmatic fluids and can map the subsurface electrical resistivity structure can provide insight by revealing the internal structure of the volcanic system in this paper we report the results of a preliminary land and shallow marine mt survey performed on and offshore the island nearest the crisis the 3d inversion derived electrical resistivity model suggests that the island is underlain by a shallow 500 m thick conductive layer atop a deeper more resistive layer possibly associated with a high temperature geothermal system at depths of 15 km the resistivity drops by almost two orders of magnitude possibly due to partial melting further petrophysical and geophysical studies are underway for confirmation and to map the geometry and evolution of the volcanic system

inferring paleotemperature from the d h ratio of lacustrine organic matter abstract linking the d h d records of the kerogen from bulk organic matter in lake sediments to known temperature d of precipitation relationships may offer new possibilities in paleoclimate studies here we examine the hydrogen isotope ratio obtained from a radiocarbon dated lake core from wisconsin situated in the midwestern part of the united states to infer paleo surface temperatures paleotemperatures were estimated by converting the d values of the organic fraction to the d values of the lake water and by implication to that of local precipitation the temperature estimates show that the middle holocene from 7000 to 5000 years before present bp was warmer by about 3 c in general agreement with speleothem data from the midwestern united states our study shows the usefulness of the d h rations of kerogen from bulk sediment as a climate proxy that can compliment compound specific hydrogen isotope studies

coherence between tropical east african and south american records of the little ice age 1 comparison of high resolution paleoclimate records from lake malawi and the cariaco basin reveals a consistent tropical behavior during the little ice age these records which are interpreted to represent southward excursions of intertropical convergence zone position over southern tropical east africa and northeastern south america are characterized by subcentennial variability superimposed on a ramp of increasing intensity from ce 1400 to 1800 this response appears similar to that of cold episodes during the late glacial the synchrony of these records suggests a teleconnection in tropical climate that may be a manifestation of persistent enso like conditions

hydrogen isotope ratios of palmitic acid in lacustrine sediments record late quaternary climate variations the rich paleoclimate information preserved in lacustrine sedimentary organic matter can be difficult to extract because of the mixed terrestrial and aquatic inputs herein we demonstrate that compound specific hydrogen isotope analysis of palmitic acid pa a ubiquitous compound in lacustrine sediments captures the d signals of lake water samples collected across a diverse range of 33 north american lakes show a strong correlation between water and dpa values at crooked pond massachusetts the dpa changes in a 14 k y sediment record parallel temperature trends inferred from fossil pollen downcore changes reveal differences between climatic trends in new england and in greenland that are consistent with important regional differences in climate controls

internal structure of piton de la fournaise volcano from seismic wave propagation and earthquake distribution abstract arrival times of seismic waves from local earthquakes are inverted for both locating the source and defining the 3 d velocity heterogeneity of piton de la fournaise the lateral heterogeneity of the 2632 m high edifice is resolved as a high velocity plug 1 5 km in diameter surrounded by a low velocity ring which may be interpreted as due to the construction of fournaise on the flank of the older volcano piton des neiges wave mode conversion detected on three component seismograms provides evidence for boundaries of contrasted velocities pre eruptive swarm earthquakes cluster in the high velocity zone under the dolomieu summit crater low strength and cohesion of the surrounding material account for the lack of seismicity for the final 1 3 km radial flow of magma to the vents in enclos fouque beneath the high velocity plug the existence of a body with low velocity for p and even for s waves is well constrained however the walls and base are poorly defined because of the lack of deep earthquakes for sampling the few earthquakes that are located in this depth region usually occur at a depth of around 1 5 km below sea level in the region of the cone this can be considered providing the upper constraint on the lower limit of the aseismic part of the low velocity body the coincidence in time of their occurrence with the swarms above sea level and the eruptions suggests magmatic activation of the low velocity aseismic volume 1 5 km below sea level under the high velocity plug of the cone further down the concentration of seismicity in two swarms between 2 and 4 km under the eastern flank does not allow the structure to be sampled effectively

magma transport and storage at piton de la fournaise la reunion between 1972 and 2007 a review of geophysical and geochemical data abstract since the middle of the 20th century improvement in volcano monitoring techniques has provided large data sets that can be used to evaluate the evolution of magma plumbing systems at piton de la fournaise volcano abundant eruptive activity and a dense monitoring network are especially conducive to such research analysis of the extensive set of geophysical and geochemical data associated with the last 35 years of activity provides new insights into magma transport and storage at piton de la fournaise two periods of frequent eruptions separated by 6 years of inactivity can be distinguished 1972 1992 and 1998 2007 considering these two periods we show evidence of major changes in the shallow plumbing system in 2000 during 1972 1992 and 1998 2000 lava compositions and weak long term eruptive precursors lasting few days to three weeks characterized by no significant summit inflation and about ten volcano tectonic earthquakes per day suggest that eruptions were fed by the progressive drainage of an occasionally recharged shallow magma reservoir geophysical evidence of shallow magma reservoir recharge was only recorded in 1986 and 1998 in contrast from 2000 to 2007 geophysical data highlight the appearance of long term precursors 1 to 5 months of summit inflation and strong seismicity up to one hundred events per day preceding cycles of successive eruptions each cycle of eruptions was characterized by a sequence 3 to 10 months in duration of summit and near summit proximal eruptions and ended with a distal low altitude oceanite olivine abundances 20 vol eruption on the eastern flank of the volcano within each of these eruptive cycles lavas became progressively more magnesian over time the preferential motion of the eastern flank caused by continuous recharging of the shallow reservoir since 2000 would favour the occurrence of distal eruptions towards this flank at the end of a cycle

an interpretive analysis of magnetotelluric data a simple analysis to determine the dimensionality of magnetotelluric resistivity variations to separate the near surface resistivity variation from the variations at depth and to find the relative resistivity variations with depth is described parameters derived from the magnetotelluric impedance tensor are mapped in pseudosection and planar view for two dimensional 2 d model data and for survey data from montana these data illustrate procedures that can qualitatively map complex resistivity structures in the lateral distance frequency domain or equivalently the lateral distance scaled vertical distance domain phase dependent parameters have better vertical resolution than parameters related to scalar apparent resistivity but the latter allow estimates of the resistivities encountered phase parameters for the montana data provide a semiquantitatively accurate cross section of a geologically known anticlinal structure this suggests a means of subsurface structural mapping with magnetotelluric data the use of these parameters with sufficiently dense and accurate data provides a first order indication of structure for subsequent quantitative modeling

magnetic and electric field observations during the 2000 activity of miyake jima volcano central japan magnetic and electric field variations associated with the 2000 eruption of miyake jima volcano are summarized for about 1 week prior to the july 8 phreatic explosion significant changes in the total intensity were observed at a few stations which indicated uprising of a demagnetized area from a depth of 2 km towards the summit this nonmagnetic source can be regarded as a vacant space itself electric and magnetic field variations were observed simultaneously associated with the tilt step event which was the abrupt v50 s inflation at a few km depth within the volcano followed by gradual recovery vseveral hours the electric field is ascribed to the electrokinetic effect most probably due to forced injection of fluids from the source while the magnetic field to the piezomagnetic effect due to increased pressure large magnetic variations amounting to a few tens of nt were observed at several stations since july 8 and they turned almost flat after the august 18 largest eruption magnetic changes are explained mostly by the vanishing of magnetic mass in the summit and additionally by the thermal demagnetization at a rather shallow depth a large increase in the self potential by 130 mv was also observed near the summit caldera associated with the august 18 eruption which suggests that the hydrothermal circulation system sustained within the volcano for the past more than 10 years was destroyed by this eruption 9 2002 published by elsevier science b v

lipid geochemistry of lake sediments from semi arid spain relationships with source inputs and environmental factors the lipid geochemistry of lake sediments can provide information on past environmental change detailed interpretation is however often hampered by a limited understanding of the provenance of many compounds and the multiple factors influencing their distributions in modern lake sediments we have quantified the solvent extractable lipid compositions of modern surface sediments from fifty four spanish lakes covering a range of hydrochemical fresh to hypersaline and hydrological shallow ephemeral to deep permanent conditions lipid compositions across the dataset are dominated by carboxylic acids up to 86 total solvent extractable lipids alkanols up to 63 and sterols up to 58 with smaller relative proportions of alkanes alkenes ketones including long chain alkenones and hopanols here we employ the distributions of these dominant compounds to explore relationships between lipid composition source inputs and lake type source input is the major factor influencing the lipid composition but there are also some indicators of early stages of lipid diagenesis in these surface sediments multivariate data analysis non metric multidimensional scaling ordination and cluster analysis of normalised lipid concentrations shows a distinction between compounds originating primarily from algal bacterial macrophyte or terrestrial plant sources this statistical technique enables sites to be grouped according to their dominant lipid compositional characteristics as well as enabling us to identify broad trends in groups of sites in terms of their environmental features e g shallow or deep lakes this modern training set study provides insight into patterns of contemporary lipid distributions and lipid source and site relationships across diverse lacustrine environments which can then be useful in environmental monitoring and palaeoenvironmental studies using sediment cores

variability of unusual distributions of alkenones in the surface waters of the nordic seas 1 samples of filtered particulate organic matter pom were obtained during the summers of 1999 and 2000 from the surface waters of the nordic seas to monitor the spatial distribution of long chain alkenones the aim of the study was to appraise existing alkenone based climatic proxies in northern high latitudes unusually high percentages of the tetraunsaturated alkenone were measured in the polar waters of the east greenland current with c37 4 of up to 77 in 80 of sea ice cover values of percent c37 4 across the nordic seas showed a strong association with water mass type analysis of coccoliths in filters indicated that calcified emiliania huxleyi could not be discounted as the biological precursor of alkenones in all the water masses a combined data set of 69 samples of pom revealed a stronger correlation of percent c37 4 to sea surface salinity sss r2 0 72 than to sea surface temperature sst r2 0 50 values of percent c37 4 in sea surface pom were much higher than those in surficial sediments of the northern north atlantic to explain the discrepancy in sedimentary and surface water column percent c37 4 we propose that the alkenone contents in surface sediments underlying arctic and polar waters are a combination of autochthonous and allochthonous inputs of alkenones our results show that percent c37 4 can be used to reconstruct the relative extension of arctic polar water masses in the north atlantic however the results prevent confirmation of percent c37 4 as a paleo sss proxy in the nordic seas given its multivariate nature in our data set and the decoupling between its range of values in surface waters and sediments

a review of molecular organic proxies for examining modern and ancient lacustrine environments molecular organic geochemical proxies are increasingly being utilized to reconstruct past environmental conditions as new tools continue to be discovered and developed to date organic geochemical proxies have been developed mainly for use in marine systems and are widely used in paleoceanography in contrast organic proxies have been less commonly used on lacustrine sedimentary records one reason for this is that the wide range in the physical and chemical properties of lakes complicates application of some organic geochemical proxies in lacustrine settings furthermore in comparison to marine studies presently only a small number of studies have conducted or are currently conducting fundamental research aimed at developing organic geochemical proxies for use in lacustrine settings despite this an increasing number of paleo limnological studies are currently applying organic geochemical techniques to examine present and past environmental conditions in this manuscript we review the use of a number of commonly utilized organic geochemical and isotopic proxies and discuss their potential for environmental reconstruction in quaternary lacustrine deposits

an experimental field study to test the stability of lipids used for the tex86 and uk 37 palaeothermometers abstract we report a one year field experiment to study sedimentary degradation of isoprenoid glycerol dialkyl glycerol tetraethers gdgts and long chain alkenones lipids used for the tex86 and u 37 k sea surface temperature sst proxies respectively homogenised surface sediments from the namibian upwelling region were set out on moorings in oxic oder bay and arkona bay baltic sea and sub oxic to anoxic gottland basin baltic sea waters and in oxic atlantic waters off cape blanc for one year to assess the influence of oxygen exposure on gdgts and alkenones no selective degradation effect on both tex86 and u 37 k proxies was evident under anoxic and sub oxic conditions under oxic conditions gdgt concentrations and the tex86 did not significantly change as well however selective degradation of alkenones occurred at all oxic sites resulting in a small but significant increase of the u 37 k index by up to 0 06 units corresponding to a temperature increase of up to 1 8 c our results demonstrate that selective alkenone degradation is a relatively fast process and complement earlier evidence for selective degradation of alkenones in the laboratory water column and sediments in contrast our results suggest that the tex86 is relatively resistant to selective oxic degradation at least on relatively short years time scales

petrology of 1977 to 1998 eruptions of piton de la fournaise la reunion island abstract geochemical and petrological variations in 35 historical eruptions from the april 1977 eruption to the march september 1998 eruption at piton de la fournaise have been analyzed for their major elements abundances mineralogical compositions and oxygen isotopes during these 21 years samplings were repeated several times during eruptions as well as temperature measurements since the end of 1977 to 1998 all erupted lavas except 1998 hudson basalt belong to the group of the steady state basalts however evidences for small degrees of differentiation can be observed during a single eruption the earliest lava emitted contains less phenocrysts and has almost always a lower mgo mgo mgo feot than the lavas emitted later suggesting that it is more differentiated from one eruption to the next between 1977 and 1998 bulk compositions are more and more differentiated towards the first lava of 1998 a process of low pressure fractional crystallisation involving small proportions of olivine clinopyroxene and plagioclase allows to explain this evolution a major result of our study is to show that this evolution does not correspond to a unique fractionation trend over the considered period different types of magmas have been distinguished the first magma type erupted from october 1977 to november 1987 was richer in potassium 0 82 wt in average than the second one and apparently derived from the liquid of the 1977 oceanite the second magma type erupted from february 1988 to september 1998 was poorer in k 2 o 0 69 wt in average in march 1998 a third magma type hudson basalt erupted simultaneously with the second one hudson basalt has undergone a wehrlitic fractionation and is supposed to come from a deeper magma reservoir than other erupted magmas for this period from 1977 to 1998 the 18 o of lavas progressively decreases with time together with the increasing chemical differentiation of the magmas by low pressure fractional crystallisation this variation agrees with the hypothesis of magma contamination at shallow level in the altered volcanic edifice vlastelic i deniel c bosq c telouk p boivin p bachelery p famin v staudacher t 2009 this issue pb isotope geochemistry of piton de la fournaise historical lavas journal of volcanology and geothermal research 184 63 78 this issue overall petrological variations are in good agreement with a model of a shallow reservoir discontinuously supplied between 1977 and 1998 the speed of the variations the coexistence of different liquids the chemical evolution of the lavas during the same eruption lead us to favour a model of chemically stratified reservoir constituted by a complex of dykes sills and laccoliths close to the surface and located above larger magma bodies

wet and arid phases in the southeast african tropics since the last glacial maximum plant leaf wax carbon isotopes provide a record of c 3 versus c 4 vegetation a sensitive indicator of aridity from the southeast african tropics since the last glacial maximum wet and arid phases in southeast africa were in phase with conditions in the global tropics from 23 to 11 ka but at the start of the holocene these relationships ended and an antiphase relationship prevailed the abrupt switch from in phase to out of phase conditions may partially be attributed to a southward displacement of the intertropical convergence zone itcz during the last glacial southward displacements of the itcz are also linked to arid conditions in southeast africa during the younger dryas and the little ice age

applicability and calibration of the tex86 paleothermometer in lakes abstract we have conducted a global survey of archaeal glycerol dialkyl glycerol tetraether gdgt lipids in lake sediments in order to develop the tex86 paleotemperature proxy for application in continental systems surface sediments of 46 globally distributed lakes were analyzed for gdgt but isoprenoid gdgt derived from aquatic crenarchaeota were only unambiguously detected in 20 of the 46 lakes analyzed aquatic crenarchaeotal gdgt were detected mainly in sediments from large lakes 4000 km2 and hydrothermal or volcanic lakes suggesting that in some mostly smaller lakes either aquatic crenarchaeota are present at low abundance resulting in sedimentary lipids below levels of detection or they are absent branched gdgt thought to be derived primarily from soil bacteria were identified in all lake sediments analyzed correlation of the tex86 in those lakes with sufficient amounts of putative crenarchaeotal gdgt with annual mean lake temperature is reasonably good r2 0 68 n 20 in order to reduce the influence of soil derived isoprenoid gdgt on the tex86 lake temperatures we have applied a filter based on relative soil derived inputs as determined by the bit branched and isoprenoid tetraether index which results in a calibration relationship with r2 0 86 n 12 and an estimated temperature error of 3 6 c our results suggest that the tex86 should be applied only in lakes with sufficient production of gdgt by aquatic crenarchaeota relative to isoprenoid gdgt derived from soil in the watershed or other aquatic sources

molecular fossil evidence for anaerobic ammonium oxidation in the arabian sea over the last glacial cycle anaerobic ammonium oxidation anammox has been recognized as an important process converting fixed nitrogen to n2 in many marine environments thereby having a major impact on the present day marine nitrogen cycle however essentially nothing is known about the importance of anammox in past marine nitrogen cycles in this study we analyzed the distribution of fossil ladderane lipids derived from bacteria performing anammox in a sediment core from the northern arabian sea concentrations of ladderane lipids varied between 0 3 and 5 3 ng g 1 sediment during the past 140 ka with high values observed during the holocene intervals during the last glacial and during the penultimate interglacial maxima in ladderane lipid abundances correlate with high total organic carbon 4 6 and elevated 15n 8 values anammox activity therefore seems enhanced during periods characterized by an intense oxygen minimum zone omz low concentrations of ladderanes 0 5 ng g 1 sediment indicating low anammox activity coincide with periods during which the omz was severely diminished since anammox activity covaried with omz intensity it may play an important role in the loss of fixed inorganic nitrogen from the global ocean on glacial interglacial timescales which was so far attributed only to heterotrophic denitrification

distributions of branched gdgts in a tropical lake system implications for lacustrine application of the mbt cbt paleoproxy branched glycerol dialkyl glycerol tetraether gdgt lipids are abundant and ubiquitous in lake sediments potentially allowing for a paleolimnological application of the so called mbt cbt proxy methylation index of branched tetraethers cyclization ratio of branched tetraethers to investigate the origin and characteristics of these compounds in lacustrine environments we examined the distributions of gdgts in soils river sediments and lake sediments from lake towuti on the island of sulawesi indonesia we found significant differences in the degree of methylation and cyclization expressed by way of the mbt and cbt indices between the soil samples and the aquatic samples suggesting that there may be in situ production of gdgts in the aquatic environment based on these findings we urge caution in the application of the mbt cbt paleoproxy to lake sediments and encourage more rigorous study of these compounds in freshwater environments

distribution and significance of long chain alkenones as salinity and temperature indicators in spanish saline lake sediments abstract we investigated relationships between sedimentary solvent extractable long chain alkenone lca concentration and composition and environmental factors in a suite of endorheic lakes from inland spain lcas were found in 14 of the 54 lakes examined with concentrations comparable with those from previously published lacustrine settings the composition of lcas in our sites however contrast from the majority of those previously reported from lake environments in our study the tri unsaturated component is the most abundant component at most sites where lcas are detected and c38 3 is the most abundant lca in the majority of sites lca occurrence appears to be restricted to brackish hypersaline sites and c37 lcas are absent above a salinity of 40 g l 1 suggesting a salinity control on lca producing organisms in these sites low concentrations of c37 lca components means u 37 k and u 37 k temperature indices are generally not applicable instead we find good relationships between c38 components and in particular mean autumn temperature and the strongest lca temperature relationships are found when using a combination of all c37 and c38 compounds we propose a new alkenone temperature index for lakes with elevated salinity and where the c38 components dominate the lca distributions this is expressed as u 3738 k 0 0464 mautat 0 867 r2 0 80 n 13 in this paper we provide the first account of sedimentary lca distributions from lakes in inland spain extending the range of environments within which these compounds have been found and highlighting their significance as indicators of both salinity and temperature in saline endorheic lake environments this has important implications for extending the potential role of lcas as palaeoclimatic indicators in lacustrine environments

a large hydrothermal reservoir beneath taal volcano philippines revealed by magnetotelluric resistivity survey 2d resistivity modeling taal volcano located in the southwestern part of luzon island philippines has frequently experienced catastrophic eruptions from both the main crater on volcano island and flank eruptions these eruptions have been magmatic phreatomagmatic and hydrothermal with the latter implying the existence of a large scale hydrothermal system beneath the volcano we conducted an electrical resistivity survey using the magnetotelluric method in order to identify the location and geometry of the hydrothermal reservoir and sealing cap rock two dimensional inversion using the observed data indicates four similar resistivity sections the structure at shallow depths corresponds to volcanic deposits and an aquifer below 1 km the structure features a relatively resistive zone beneath the main crater surrounded by a conductive shell we interpreted these to be a large hydrothermal reservoir with an impermeable cap rock sealing it recent ground deformation detected by gps measurements suggests that the hydrothermal reservoir is active the interpreted cap rock thins just beneath the main crater and could easily be destroyed by an imbalance in the hydrothermal system we conclude that this hydrothermal reservoir plays a significant role in driving catastrophic eruptions that begin with a hydrothermal explosion at the main crater

electromagnetic outline of the solfatara pisciarelli hydrothermal system campi flegrei southern italy abstract we describe the results from a combined controlled source audio magnetotelluric csamt and natural source magnetotelluric mt survey carried out in the solfatara pisciarelli s p area located in the central part of the campi flegrei cf composite caldera west of naples southern italy the s p area represents the most active zone within the cf caldera in terms of hydrothermal manifestations and local seismicity since 1969 the cf caldera is experiencing ground deformation seismicity and geochemical fluid changes which are particularly evident in the s p area a 1 km long nearly w e directed csamt mt profile crossing the fumarole field was carried out in the s p area with the aim of deducting a resistivity model of the structural setting of the hydrothermal system in the first 3 km depth an interpretation of the modelled section across the profile is given in this paper taking advantage from already existing seismic gravity and geochemical data in the same area three well distinct zones have been outlined the first zone is a very shallow electrically conductive body localized beneath the westernmost segment of the profile which within a short distance of about 100 m dips westwards from near surface down to some hundred metres in depth mostly accounting for the very low resistivity 1 10 m and the exceedingly high values of v p v s 4 this shallow zone has been ascribed to a water saturated high pressurized geothermal reservoir the second zone which has been localized below the west central portion of the csamt mt transect appears as a composite body made up of a nearly vertical plumelike structure that escapes at about 2 25 km depth from the top edge of the east side of a presumably horizontal platelike body the plumelike structure rises up to the free surface in correspondence of the fumarole field whereas the platelike structure deepens at least down to the 3 km of maximum exploration depth the combined interpretation of resistivity 50 100 m body wave velocity ratio v p v s 3 and geochemical data indicates that the plumelike portion can likely be associated with a steam gas saturated column and the platelike portion with a high temperature 300 c over pressurized gas saturated reservoir finally the third zone which has been localized beneath the eastern half of the transect from about 1 2 km down to about 3 km of depth is also characterized by very low resistivity values 1 10 m jointly interpreted with seismic v p v s 0 g cm 3 data this last electrically conductive structure appears to be associated with a hydrothermally mineralized clay rich body

combined dna and lipid analyses of sediments reveal changes in holocene haptophyte and diatom populations in an antarctic lake preserved ribosomal dna of planktonic phototrophic algae was recovered from holocene anoxic sediments of ace lake antarctica and the ancient community members were identified based on comparative sequence analysis the similar concentration profiles of dna of haptophytes and their traditional lipid biomarkers alkenones and alkenoates revealed that fossil rdna also served as quantitative biomarkers in this environment the dna data clearly revealed the presence of six novel phylotypes related to known alkenone and alkenoate biosynthesizing haptophytes with isochrysis galbana uio 102 as their closest relative the relative abundance of these phylotypes changed as the lake chemistry particularly salinity evolved over time changes in the alkenone distributions reflect these population changes rather than a physiological response to salinity by a single haptophyte using this novel paleo ecological approach of combining data from lipid biomarkers and preserved dna we showed that the post glacial development of ace lake from freshwater basin to marine inlet and the present day lacustrine saline system caused major qualitative and quantitative changes in the biodiversity of the planktonic populations over time

estimation of electric fields in the conducting earth s crust for oscillating electric current dipole sources and implications for anomalous electric fields associated with earthquakes abstract electromagnetic radiation possibly associated with earthquake occurrences in the earth s crust can be treated as a problem of electromagnetic induction within a conducting half space representing the crust we estimated the magnitude of the electric field near the earth s surface for oscillating electric current dipole sources located at various depths this shows that the electric field highly attenuates as expected and the source must be stronger than 10 5 a m even if it is located at a depth of several kilometers for practically detecting signals at frequencies in the ulf ultra low frequency range we also examined the electric field near the earth s surface for a box car type source in uniform and non uniform crust models we found that the wave form of the source is rather well preserved in both models but signal amplitudes are very small and unlikely to be drastically enhanced even in a non uniform crustal structure although this discussion is based only on a specific non uniform model

a study of the alkenone tex86 and planktonic foraminifera in the benguela upwelling system implications for past sea surface temperature estimates suspended particulate matter from seawater and core top sediments were collected during 2003 meteor cruise m57 1 in january february from the continental margin off western south africa for analysis of alkenones glycerol dibiphytanyl glycerol tetraether gdgt lipids and planktonic foraminifera alkenone analysis of suspended particulates in seawater and core top sediments indicates that u37k temperatures were representative of annual mean sea surface temperature in contrast gdgt analysis suggests that tex86 temperatures are cold biased due to upward transports of gdgts produced below the mixed layer the analysis of plankton tow samples revealed that the 18o of globorotalia inflata in core top sediments could be biased toward lower temperatures due to subsurface calcification accordingly our study shows that each paleotemperature proxy may record different temperature signals in the benguela upwelling system emphasizing the general need to constrain potential biases in each proxy for better interpreting paleoclimate records

alkenone distributions in the north atlantic and nordic sea surface waters 1 the c37 c39 alkenones were quantified in suspended particulate matter obtained from the surface waters of the north atlantic including the nordic seas over a temperature range of 4 20 c u37k values were linearly correlated to temperature over the entire range covered by our data set i e 4 20 c u37k 0 027t 0 036 r2 0 97 the compilation of water column data from the atlantic pacific and southern ocean and mediterranean sea suggests that the linear model may not be the best function for fitting u37k and in situ temperature values it also shows that suspended matter data from warm waters t 20 c are still needed to constrain the equation of the global curve high abundances of c37 4 were found in the coldest polar waters around 4 c c37 4 represented up to 35 a value that dropped to zero at temperatures above 10 c values of c37 4 were linearly correlated to temperature c37 4 3 7t 43 7 r2 0 50 and salinity c37 4 48 1s 1691 r2 0 78 further investigations from other oceanic basins are necessary to confirm these findings

a study of the tex86 paleothermometer in the water column and sediments of the santa barbara basin california 1 particulate organic matter collected during a 2 year period as part of an ongoing sediment trap study and a high resolution sediment record from 1850 to 1987 a d from the santa barbara basin were analyzed for tex86 a temperature proxy based on marine crenarchaeotal membrane lipids highest fluxes of crenarchaeotal lipids in the water column were found in may june 1996 and from october 1996 to january 1997 and in general showed a good correlation with mass fluxes tex86 reconstructed temperatures from the sediment trap series ranged from 8 to 11 c and were usually substantially lower than sea surface temperatures sst indicating that unlike in previous studies the tex86 corresponds to subsurface temperatures likely between 100 and 150 m tex86 temperature variations observed in trap samples were not coupled to changes in sst or deep water temperatures and only to some degree with crenarchaeotal lipid fluxes this suggests that a complex combination of different depth origins and seasonal growth periods of crenarchaeota contributed to the variations in tex86 signal during the annual cycle tex86 temperatures in the two sediment cores studied 8 13 c were also substantially lower than those of instrumental sst records 14 17 5 c confirming that tex86 records a subsurface temperature signal in the santa barbara basin this result highlights the importance of performing calibration studies using sediment traps and core tops before applying the tex86 temperature proxy in a given study area

decoupling of bio and geohopanoids in sediments of the benguela upwelling system bus abstract geohopanoids derive from bacteriohopanepolyol bhp precursors however knowledge of the specific sources and diagenetic fate of both compound classes in marine sediments is fragmentary we studied the relationship between bhps and geohopanoids in a sediment core from the central benguela upwelling system bus including deposits over the last 75 ka the bus is a palaeo oceanographically stable setting where primary production is largely controlled by variation in upwelling intensity and therefore nutrient supply marine production in the bus was generally higher during glacial than during interglacial times as reflected in the levels of sedimentary total organic carbon geohopanoids at the study site consisted mainly of extractable hopanes and hopanols and occurred in the highest amounts during glacial periods a minor but still considerable fraction of geohopanoids was sulfur linked to geomacromolecular organic matter among these s bound hopane moieties 17 h 21 h trishomohopane c33 was the predominant compound suggesting a diagenetic overprint of bhps before linkage among the bhps a rare bacteriohopanetetrol with likely 22s configuration was observed this structural feature was lacking in the geohopanoids which all had the 22r configuration different behaviour of bhp and geohopanoid concentrations as well as 13c discrepancies indicate a decoupling of bio and geohopanoids geohopanoids most likely reflect laterally transported fossil organic matter whereas bhps are indigenous to the upper water column of the study site and may relate to past upwelling intensity nutrient levels hence care has to be taken using geohopanoids and other biomarkers for palaeoreconstruction in settings where sedimentation processes are not fully understood

eruptive mechanism on piton de la fournaise volcano associated with the december 4 1983 and january 18 1984 eruptions from ground deformation monitoring and photogrammetric surveys abstract two photogrammetric aerial surveys were carried out over the summit area of the basaltic shield volcano piton de la fournaise indian ocean one survey in 1981 and the second one in 1984 during this time only two eruptions occurred both the december 4 1983 and the january 18 1984 eruptions opened fissures on the southwestern part of the summit because of the slight and erratic ground deformation measured on the dry tilt network by continuous tilt stations and within the geodetic network between 1981 and november 1983 and between february 1984 and june 1984 ground deformations revealed by the two photogrammetric surveys can be essentially associated with the two eruptions large displacement vectors were obtained up to 40 cm horizontal displacement vectors indicate a northeastward ground deformation of the southwestern part of the cone where the effusive vents opened a more diffuse uplift along the main fracture zones that cut the volcanic edifice was observed while east of these fractures only slight less than 10 cm and opposite displacements were observed this displacement field can be associated with the main geological structures of the dome of piton de la fournaise volcano some consequences of the observed displacement field may be outlined for the volcanic observational ground deformation networks to estimate the displacement field revealed by the photogrammetric surveys a simple model of dyke intrusion has been computed this model is based on dislocations and takes into account the main fracture zones good agreement is observed between computed and observed data in the area of the effusive vents some disagreement remains in the northwestern part of the survey area where horizontal deformations are small and erratic and also in the northern part where an uplift was observed that can be associated with the northern active fracture zones

simulation of co2 concentrations temperature and stratification in lake nyos for different degassing scenarios 1 a large gas cloud erupted unexpectedly in 1986 from lake nyos the larger of the two cameroonian killer lakes with devastating consequences regular monitoring subsequently revealed that the deep water of the lake was gradually recharged with co2 to preclude a similar event in the future a degassing pipe was installed in the lake in 2001 in the present study a one dimensional model is used to predict the effects of this pipe and other degassing options on the co2 concentrations and the stratification within the lake for the next 50 years the results of the simulations show that without degassing total co2 content would reach the preeruption value within a few decades the presently installed pipe is sufficient to reduce co2 pressures in the entire water column above the pipe inlet to 5 bar within 10 years and a steady state is reached within 50 years depending on the assessment of the risk due to the gas currently remaining in the lake and the costs involved the installation of additional pipes could be considered 1 to remove the gas more quickly and 2 as a backup for long term failures and maintenance once the steady state is reached degassing with one pipe is a practicable long term solution which can also be used for monitoring the approximate deep water co2 concentrations by nonprofessionals assuming a doubled deep water input in the future as an upper limit of the expected source strength the pipe is still able to prevent a co2 accumulation as a side effect the degassing operation strongly changes the stratification in the lake it transforms the lake from a meromictic to an oligomictic system and gradually removes the dissolved salts from the lake

selective preservation of soil organic matter in oxidized marine sediments madeira abyssal plain in ocean margin sediments both marine and terrestrial organic matter om are buried but the factors governing their relative preservation and degradation are not well understood in this study we analysed the degree of preservation of marine isoprenoidal and soil derived branched glycerol dialkyl glycerol tetraethers gdgts upon long term oxygen exposure in om rich turbidites from the madeira abyssal plain by analyzing gdgt concentrations across oxidation fronts relative to the anoxic part of the turbidites ca 7 20 of the soil derived branched gdgts were preserved in the oxidized part while only 0 2 3 of the marine isoprenoid gdgt crenarchaeol was preserved due to these different preservation factors the branched isoprenoid tetraether bit index a ratio between crenarchaeol and the major branched gdgts that is used as a tracer for soil derived organic matter substantially increases from 0 02 to 0 4 split flow thin cell splitt separation of turbidite sediments showed that the enhanced preservation of soil derived carbon was a general phenomenon across the fine particle size ranges 38 m calculations reveal that despite their relatively similar chemical structures degradation rates of crenarchaeol are 2 fold higher than those of soil derived branched gdgts suggesting preferential soil om preservation possibly due to matrix protection

geophysical and hydrogeological experiments from a shallow hydrothermal system at solfatara volcano campi flegrei italy response to caldera unrest 1 integration of high resolution geophysical and hydrogeological investigations at solfatara volcano campi flegrei italy allowed us to 1 image the shallow and intermediate subsurface to the crater 2 elucidate patterns in the shallow subsurface degassing and 3 refine and upgrade volcano monitoring strategies for this dynamic area our results show that the subsurface to the crater can be divided roughly into two zones a dry outcropping layer overlying a horizon saturated by hydrothermal fluids within this saturated zone intersections of dominant nw and ene striking structural lineaments act as preferential escape conduits for the fluids which generate high microseismic noise amplitudes in the southeastern part of the crater hydrogeological data suggest an uprising of the isotherms below solfatara crater and a marked increment of fluid degassing over the last 40 years sudden variations of both seismic noise level and noise cycling are positively correlated with early stages of ground inflation during the ad 2000 uplift we believe therefore that monitoring of seismic noise can be used for upgrading early warning strategies in this sector of the campi flegrei volcanic system

lipids of aquatic organisms as potential contributors to lacustrine sediments ii abstract the relationship between the lipid composition of organisms in the water column of an eutrophic lake and the lipid composition of underlying sediments previously examined for n alkanols and steroids is now reported for hydrocarbons ketones and carboxylic acids the n c7 alkane and alkenoic acids from two primary sources are rapidly metabolized in the water column and surficial sediment bacterial biomarkers including hopenes and i ai branched fatty acids were detected in the photosynthetic bacterial layer occurring just above the sediment water interface within the sediment the apparent conversion of free n alkanes alkan 2 ones and hydroxy acids to the corresponding bound form is noted microbiological oxidation of n alkanes to alkan 2 ones is supported by the detection of the intermediate alkan 2 ols with a distribution similar to that of the ketones the geochemistry of sediment deposited c 1900 prior to biological study of the site was interpreted from stable biomarkers and the diagenetic changes recognised in the study of contemporary deposition a qualitative difference in algal input to the older sediment is inferred from the low 7 sterol content and presence of 2 6 10 trimethyl 7 3 methylbutyl dodecane however there was still significant dinoflagellate input as indicated by the presence of 4 methylsterols a difference in higher plant input to the older sediment indicated from the n alkane alkene and triterpenoid ketone distributions is consistent with the recent development of tree cover

carbon isotope composition of lower cretaceous fossil wood ocean atmosphere chemistry and relation to sea level change the carbon isotope composition of fossil wood fragments collected through a biostratigraphically well constructed aptian lower cretaceous shallow marine siliciclastic succession on the isle of wight southern britain shows distinct variations with time the results indicate that the stratigraphic signature of delta sup 13 c sub wood through the aptian was influenced primarily by fluctuations in the isotopic composition of co sub 2 in the global ocean atmosphere system as registered in marine carbonates elsewhere and was not governed by local paleoenvironmental and or paleoecological factors negative and positive excursions in delta sup 13 c sub wood through the lower aptian occur in phase with inferred transgressions and regressions respectively a pattern that contrasts with that observed in many previous studies for different time intervals the relationship between delta sup 13 c variations and relative sea level change is tentatively interpreted as a response to various climatic and eustatic factors relating to rapid sea floor spreading thermal uplift of ocean floor emplacement of plateaus volcanic co sub 2 emissions weathering and sedimentary rate

rapid sulfurisation of highly branched isoprenoid hbi alkenes in sulfidic holocene sediments from ellis fjord antarctica samples of particulate organic matter from the water column and anoxic holocene sediment layers from the small meromictic basin smb in ellis fjord eastern antarctica were analyzed to study the early incorporation of reduced inorganic sulfur species into highly branched isoprenoid hbi alkenes hbis were not detected in the water column samples taken during austral winter whereas compounds containing the c25 hbi skeleton were abundant in all analyzed holocene sediment layers the structure of the c25 2 hbi alkene and its enriched stable carbon isotopic composition suggest that it is produced by a diatom or diatoms probably belonging to the navicula genus in the sea ice which covers the area most of the year within just 500 years of deposition all of the hbi alkene was sulfurised a mixture of products was formed including components tentatively identified as a c25 hbi thiane and three s containing dimers composed of two c25 1 hbi skeletons linked together by a sulfide bond most was however converted to polar s containing compounds the reaction rate for sulfurisation of the c25 2 hbi alkene is the highest observed so far in natural systems sterols and other lipids known to be prone to sulfurisation were not sulfurised the reason for this is unclear

determination of sediment provenance at drift sites using hydrogen isotopes and unsaturation ratios in alkenones the large 20 hydrogen isotopic gradient in surface waters of the northwest atlantic ocean is exploited to track changes in the source of alkenones to the bermuda rise sediment drift cultures of the predominant alkenone producing coccolithophorid e huxleyi were grown in deuterium enriched seawater and shown to possess alkenones with a d h ratio that closely tracked the water d h ratio r 2 0 999 n 5 isotopic enrichments with a fractionation factor between 0 732 and 0 775 a hydrogen isotopic depletion of 193 3 n 9 was measured in alkenones from suspended particles relative to seawater in the subpolar and subtropical northwest atlantic ocean this value was used to calculate the water d values in which alkenones from bermuda rise sediment were synthesized and by extension the water mass in which they were produced applying this technique we find that 60 to 100 of the alkenones in late holocene bermuda rise sediment were produced in deuterium depleted subpolar water to the northwest of the drift to reconcile values of the alkenone unsaturation ratio u k 37 a widely used proxy for sea surface temperature with the d values of alkenones in late holocene sediments from the bermuda rise at least three sources of sediment must be invoked a cold very isotopically depleted source almost certain to be the scotian margin a warm moderately isotopically depleted source likely to be the northwestern edge of the subtropical gyre and a cold isotopically enriched source which we hypothesize to be the subpolar waters overlying the main branch of north atlantic deep water flowing southwest from the nordic seas copyright 2005 elsevier ltd paleoclimate records with sufficient length and temporal resolution to study the occurrence and causal mechanisms of abrupt climate change are exceedingly rare rapidly deposited ocean sediments provide the best archive for studying these events through geologic time but such sites in the open ocean are limited to sediment drift deposits such as the bermuda rise in the northwest atlantic using multiple climate proxies in a single core is becoming more common in high resolution pa leoclimate investigations but a major potential concern for this approach arises from the possibility that the fine fraction of sediment e g 63 m and the climate proxies within it may represent conditions far from the deposition site here we propose and test the hypothesis that hydrogen isotope ratios of alkenones a class of lipids from phytoplankton may provide insight into the source of fine grained sediment because of their restricted sources broad geographic distri bution and excellent preservation properties alkenones are of particular interest in the emerging field of compound specific hydrogen isotopic analysis the sedimentary abundances ex tents of unsaturations and isotopic compositions of alkenones provide quantitative and near continuous records we isolated alkenones from cultured unicellular algae haptophyte emil iania huxleyi surface ocean particulate material and open ocean sediments to determine the extent and variability of hydrogen isotopic fractionation in the di tri and tetraunsat urated c37 compounds we then compared the d values of the alkenones in surface sediments between the bermuda rise and the scotian margin above which a large 20 d gradient exists we determined the fractionation between alkenones from suspended particulate samples and the water in which the phytoplanton lived and examined the variability of alkenone d values during the medieval warm period little ice age climate transition cf keigwin 1996 at the bermuda rise

δd values of individual n alkanes from terrestrial plants along a climatic gradient implications for the sedimentary biomarker record abstract the compound specific hydrogen isotope composition d of sedimentary n alkanes is increasingly used as a palaeoclimate proxy to explore the origin of the hydrogen isotope signal of n alkanes from higher terrestrial plant biomass in sedimentary organic matter of small lakes we have analysed the n alkane composition and d values of 31 plant biomass samples birch betula beech fagus oak quercus alder alnus hornbeam carpinus and myrtle myrtus as well as non stomata containing sphagnum cladonia and moss from 14 sites along a climatic gradient from northern finland to southern italy eleven of the sites were previously investigated for the n alkane d values in adjacent lake sediments and are compared to the leaf wax n alkane d values the distribution of terrestrial n alkanes in lake sediments was not found to be characteristic of the dominant vegetation around the lake evidently n alkane distributions within the same species at different sites were found to be variable these findings complicate the use of certain n alkane distributions in sediments as a palaeoenvironmental indicator d values of plant biomass n alkanes show a significant positive correlation with the precipitation d values biomass n alkane d values are in general less negative than the associated sedimentary n alkanes of terrestrial origin possibly due to the stronger evapotranspiration during the summer when sampling took place this suggests that n alkanes in leaves show seasonal variations and the sedimentary organic matter receives the lighter isotope signal of the autumn when most leaves are incorporated into the sediment the variability of the d values from non stomata containing plants is much higher than for broadleaf trees since stomata can regulate water loss through evapotranspiration the average chain length acl of n alkanes from deciduous tree leaves increases from north to south with increasing acl the hydrogen isotopic fractionation e between source water and n alkanes also increases our results prove that terrestrial n alkane d values record the d value of precipitation modified by the amount of isotope enrichment in the leaf water due to plant anatomy stomata vs no stomata and site specific meteorological conditions such as evapotranspiration relative humidity and soil moisture therefore terrestrial n alkanes in lake sediments can deliver information on changes in these parameters over geological timescales in lake sediments where aquatic n alkanes such as n c 17 record the lake water d value the isotopic difference between terrestrial and aquatic n alkanes could therefore be used to reconstruct changes in evapotranspiration

occurrence of long chain n alkenols diols keto ols and sec alkanols in a sediment core from a hypereutrophic freshwater lake abstract long chain mid chain diols and keto ols have been reported mainly in marine environments but only rarely in lacustrine sediments in this work exceptionally high abundances and diversity of keto ols diols and structurally related long chain n alkenols and secondary alkanols were detected in sediments from a hypereutrophic freshwater lake lake valencia venezuela the maximum concentrations are 241 g g toc for n alkenols 75 g g toc for diols 367 g g toc for keto ols and 8 7 g g toc for secondary alkanols eleven keto ol isomers were identified which is the highest diversity yet reported for sediments the presence of five keto ol isomers namely 1 12 c 30 keto ol 1 14 c 31 keto ol 1 15 c 33 keto ol 1 16 c 33 keto ol and 1 18 c 35 keto ol is reported for the first time the mass spectra for osmium tetroxide derivatives from long chain n alkenols confirmed the double bond location at carbons 13 14 or 15 the carbon isotope compositions were substantially enriched in 13 c for n alkenols diols and keto ols 13 c 22 0 2 2 relative to the corresponding long chain n alkanols 29 6 0 8 suggesting an autochthonous aquatic microbial origin rather than from a terrestrial i e fern source although a strong predominance of cyanobacteria was reported for in the lake s plankton community 90 and relatively low abundance of sedimentary sterols suggests cyanobacteria as a potential source eustigmatophytes a major reported producer of diols and keto ols cannot be excluded because eustigmatophytes are easily confused with other microalgae and may have been overlooked in previous studies n alkenols and keto ols displayed similar historical patterns over the past 10 000 years but there were distinct differences from the diol patterns this result suggested that n alkenols and keto ols may be derived from the same sources while diols either undergo different environmental diagenesis or have different sources a keto ol index coincides well with the hydrological changes of lake valencia over the last 10 000 years and corroborates its validity as a paleo indicator

electrical resistivity tomography study of taal volcano hydrothermal system philippines taal volcano 311 m in altitude is located in the philippines 14 n 121 e and since 1572 has erupted 33 times causing more than 2 000 casualties during the most violent eruptions in march 2010 the shallow structures in areas where present day surface activity takes place were investigated by dc resistivity surveys electrical resistivity tomography ert lines were performed above the two identified hydrothermal areas located on the northern flank of the volcano and in the main crater respectively due to rough topography deep valleys and dense vegetation most measurements were collected using a remote method based on a laboratory made equipment this allowed retrieval of information down to a depth of 250 m erts results detail the outlines of the two geothermal fields defined by previous self potential co2 soil degassing ground temperature and magnetic mapping harada et al japan acad sci 81 261 266 2005 zlotnicki et al bull volcanol 71 29 49 2009a phys chem earth 34 294 408 2009b hydrothermal fluids originate mainly from inside the northern part of the main crater at a depth greater than the bottom of the crater lake and flow upward to the ground surface furthermore water from the main crater lake infiltrates inside the surrounding geological formations the hydrothermal fluids outlined by gas releases and high temperatures cross the crater rim and interact with the northern geothermal field located outside the main crater

aging of marine organic matter during cross shelf lateral transport in the benguela upwelling system revealed by compound specific radiocarbon dating organic matter accumulation and burial on the namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers much of the material deposited in depo centers on the slope ultimately derives from the shelf supply of organic matter from the shelf involves selective transport of organic matter we studied these selective transport processes by analyzing the radiocarbon content of co occurring sediment fractions here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity phytoplankton derived alkenones membrane lipids of pelagic crenarchaeota crenarchaeol and calcareous microfossils of planktic foraminifera in core top and near surface sediment samples the samples were collected on the namibian margin along a shelf slope transect 85 to 1040 m at 24 s and from the upper slope depo center at 25 5 s in core top sediments alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth crenarchaeol while younger than alkenones also increased in age with distance offshore it was concluded that the observed ages were a consequence of cross shelf transport and associated aging of organic matter radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied pre aged material present in a sample highlighting the importance of nepheloid transport for the sedimentation of organic matter over the namibian margin

role of the structural inheritance of the oceanic lithosphere in the magmato tectonic evolution of piton de la fournaise volcano la reunion island la reunion island is located east of madagascar on the eastern rim of the tectonically inactive mascarene basin this island is composed of three shield volcanoes of which only piton de la fournaise is currently active although the magmatic activity is restricted to piton de la fournaise a scattered seismicity occurs on the whole 200 km wide volcanic edifice and in the underlying oceanic crust we carried out a multiscale analysis to understand 1 the origin of the seismicity in the geodynamic context and 2 the role of the oceanic lithosphere in the deformation of piton de la fournaise and la reunion island analysis of the magmatic system suggests that the magma ascent is controlled by large n25 30 and n125 130 fracture zones located below the enclos depression we also show that the orientation difference between the eruptive fissures and the related dykes result from a rotation of the main principal stress s 1 from vertical to downslope through the surface combining a digital elevation model dem analysis field observations and the geophysical data reveals that the volcano is affected by large fault zones the fault distribution indicates the predominance of a main n70 80 trend magnetic data show the same n80 orientation characterizing the remnant part of the alizes volcano such parallel alignment suggests a control exerted by the underlying alizes volcano on piton de la fournaise furthermore the alignment between the crustal orientations and the structures determined on the island suggests a control of the crustal structures in la reunion s volcano tectonic activity contrary to several volcanic islands such as hawaii and tenerife la reunion volcanoes lie on an upbending crust then we interpret the reactivation of the crustal faults as resulting from a crustal uplift related to the thermal erosion of the base of the lithosphere and or to strong underplating the upward deformation may prevent the spreading of the volcanoes as no evidence of such a mechanism is observed in the bathymetry and the seismic data around the island

occurrence and abundance of soil specific bacterial membrane lipid markers in the tet watershed southern france soil specific bhps and branched gdgts recently four bacteriohopanepolyols bhps adenosylhopane and structurally similar adenosylhopane type 1 2 methyl adenosylhopane and 2 methyl adenosylhopane type 1 have been suggested to be characteristic of soil microbial communities and therefore can serve as molecular markers for soil organic matter om supply in river lake and marine sediments in this study we analyzed bhps in peats and soils collected in the tet watershed southern france and compared them with branched glycerol dialkyl glycerol tetraethers gdgts a more established molecular tracer of soil om adenosylhopane type i is identified in all of the samples from the study area except one collected near the tet river mouth with up to three of the related compounds also frequently present particularly in the surface samples the concentrations of soil specific bhps in peat environments have been shown to increase with lower delta 15 n values providing evidence that n 2 fixing bacteria are probably a major source of soil specific bhps in acidic environments it seems likely that soil ph is a major factor controlling bhp occurrence based on statistical analysis of environmental parameters and bhp concentration data the comparison of the soil specific bhp concentrations with those of branched gdgts shows no clear relationship in the tet river system supporting the concept that these two groups of soil specific compounds are synthesized by different microbial organisms living in different niches in the soil profile e g oxic top versus anoxic deep

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

resistivity variations related to the large march 9 1998 eruption at la fournaise volcano inferred by continuous mt monitoring abstract the 2645 m high la fournaise volcano located in the southwest of reunion island indian ocean is a shield basaltic volcano where effusive eruptions generally occur along long fissures starting from the summit alongside major fractures that characterize the eruptions dynamism and effusivity between 1992 and 1998 the volcano underwent a quiet period during which few earthquakes were recorded minor seismic activity returned after 1997 and picked up in march 1998 during the 35 h preceding the march 9 eruption from 1996 two autonomous stations csv and bav were installed on the volcano csv was located inside the enclos fouque caldera while bav was positioned 8 2 km nw of the volcano summit horizontal components of the electric and magnetic fields were sampled every 20 s continuous time series were available from 1996 to 1999 at csv and from 1997 to march 1998 at bav data have been processed using both single station and remote reference processing both results show apparent resistivity variations synchronous to the eruption time lapse impedance estimates are computed on overlapping time windows of about two days at both stations the only major decrease of the observed impedance coincides with the march 1998 eruption at csv the resistivity started to drop about five days before the eruption reached several local minima until april and then slowly increased as the volcanic crisis reduced in activity after the end of the crisis in september 1998 the apparent resistivity recovered its pre crisis value the time lapse results also show variability in directionality sharp and elongated phase tensor ellipse residuals appear during the eruption with a n105 orientation suggesting the emergence of an almost ns striking dyke a 1d background model built from mt soundings performed during the quiet period 1996 to february 1998 on which a 3d ns striking dyke was added shows a good agreement with phase tensor residuals and spatial distribution of the resistivity variations observed during the eruption

the biomarker record of lake albano central italy implications for holocene aquatic system response to environmental change abstract a study of lipid biomarkers in predominantly laminated organic carbon rich sediments in lake albano central italy has been used to reconstruct changes in the aquatic system variations and changes in the lake catchment area during the holocene biomarkers of aquatic organic matter such as dinosterol isoarborinol tetrahymanol diplopterol and diploptene reflect two major changes in the mixing behaviour and the biological assemblages of lake albano at around 6 5 and 3 8 ky bp respectively biomarkers for higher land plants such as friedelin long chain n alkanes amyrenone and amyrenone display different distribution patterns indicating changes in the lake s catchment at 6 5 and 5 0 ky bp resulting from soil erosion and changes in the local vegetation analogously the recognised changes in the water column structure and biological components are coherent with previous reconstructions based on independent parameters the new data highlight the importance of multiproxy studies to better characterize palaeoenvironmental changes that are in turn the first step towards elucidating their trigger mechanisms i e climate vs human induced

a radiocarbon based assessment of the preservation characteristics of crenarchaeol and alkenones from continental margin sediments crenarchaeotal glycerol dibiphytanyl glycerol tetraether gdgt lipids and alkenones are two types of biomarkers derived from planktonic marine microorganisms which are used for reconstruction of sea surface temperature we determined the radiocarbon contents of the archaeal gdgt crenarchaeol and of alkenones isolated from continental margin sediments systematic differences were found between the two biomarkers with higher radiocarbon content in crenarchaeol than in the phytoplankton derived alkenones these differences can be explained by variable contributions of pre aged laterally advected material to the core sites crenarchaeol appears to be more efficiently degraded during transport in oxygen replete environments than alkenones whether this reflects the influence of chemical structure or mode of protection e g particle association is not known

millennial scale sea surface temperature changes in the eastern mediterranean nile river delta region over the last 27 000 years 1 in this study we utilize two organic geochemical proxies the u37k index and tex86 to examine past sea surface temperatures sst from a site located near the nile river delta in the eastern mediterranean em sea the u37k and tex86 records generally are in agreement and indicate sst ranges of 14 c 26 c and 14 c 28 c respectively during the last 27 cal ka during the holocene tex86 based sst estimates are usually higher than u37k based sst estimates which is likely due to seasonal differences between the timing of the haptophyte and crenarchaeota blooms in the em and is related to the onset of the modern flow regime of the nile river both records show that sst varied on centennial to millennial timescales in response to global climate events i e cooling during the last glacial maximum lgm heinrich event 1 h1 and the younger dryas yd and warming during the bolling allerod and in the early holocene during deposition of sapropel s1 the h1 cooling was particularly severe and is marked by a drop in sst of 4 5 c in comparison to pre h1 sst with temperatures 1 c cooler than during the lgm in contrast to high latitude and western mediterranean records which indicate both an abrupt onset and termination of the yd event the transition from the yd to the holocene was much more gradual in the em

unusual distributions of long chain alkenones and tetrahymanol from the highly alkaline lake van turkey long chain c37 to c40 alkenones with di tri and tetra unsaturation are very abundant in sediment trap material and holocene to late pleistocene core samples from the earth s largest soda lake lake van turkey thus the known distribution range of these typical biomarkers for haptophyte microalgae is extended to highly alkaline environments the observed unsaturation patterns differ strikingly from those found in open marine haptophytes and sediments by an enhanced relative abundance of the tetra unsaturated compounds especially the c37 4 methyl ketone their preponderance is suggested to be a facies marker pattern for lacustrine and marginal marine areas of sedimentation using published u37k calibrations no reliable absolute temperatures were obtained for the lake van samples accordingly marine sea surface temperature determinations based on long chain alkenones should be applied with caution when a contribution of these compounds from coastal or nonmarine sources can not be excluded the presence of tetrahymanol and gammacer 3 one in the lake van materials is attributed to organic matter contributions of ciliates the relative abundance of long chain alkenones and of tetrahymanol gammacer 3 one is considered to reflect changes in the environmental conditions in particular in the hydrological setting we suggest that times of pronounced stagnation are recognised by very high tetrahymanol gammacer 3 one concentrations together with drastically increased stanol stenol ratios and intervals of enhanced convection or of high freshwater input are characterised by high alkenone contributions