detrital carbonate peaks on the labrador shelf a 13 7 ka template for freshwater forcing from the hudson strait outlet of the laurentide ice sheet into the subpolar gyre abstract the laurentide ice sheet lis was a large dynamic ice sheet in the early holocene the glacial events through hudson strait leading to its eventual demise are recorded in the well dated labrador shelf core md99 2236 from the cartwright saddle we develop a detailed history of the timing of ice sheet discharge events from the hudson strait outlet of the lis during the holocene using high resolution detrital carbonate ice rafted detritus ird 18o and sediment color data eight detrital carbonate peaks dcps associated with ird peaks and light oxygen isotope events punctuate the md99 2236 record between 11 5 and 8 0 ka we use the stratigraphy of the dcps developed from md99 2236 to select the appropriate r to calibrate the ages of recorded glacial events in hudson bay and hudson strait such that they match the dcps in md99 2236 we associate the eight dcps with h0 gold cove advance noble inlet advance initial retreat of the hudson strait ice stream hsis from hudson strait opening of the tyrrell sea and drainage of glacial lakes agassiz and ojibway the opening of foxe channel and retreat of glacial ice from foxe basin are represented by a shoulder in the carbonate data r of 350 years applied to the radiocarbon ages constraining glacial events h0 through the opening of the tyrell sea provided the best match with the md99 2236 dcps r values and ages from the literature are used for the younger events a very close age match was achieved between the 8 2 ka cold event in the greenland ice cores dcp7 8 15 ka bp and the drainage of glacial lakes agassiz and ojibway our stratigraphic comparison between the dcps in md99 2236 and the calibrated ages of hudson strait bay deglacial events shows that the retreat of the hsis the opening of the tyrell sea and the catastrophic drainage of glacial lakes agassiz and ojibway at 8 2 ka are separate events that have been combined in previous estimates of the timing of the 8 2 ka event from marine records sw iceland shelf core md99 2256 documents freshwater entrainment into the subpolar gyre from the hudson strait outlet via the labrador north atlantic and irminger currents the timing of freshwater release from the lis hudson strait outlet in md99 2236 matches evidence for freshwater forcing and lis icebergs carrying foreign minerals to the sw iceland shelf between 11 5 and 8 2 ka the congruency of these records supports the conclusion of the entrainment of freshwater from the retreat of the lis through hudson strait into the subpolar gyre and provides specific time periods when pulses of lis freshwater were present to influence climate

linking the 8 2 ka event and its freshwater forcing in the labrador sea 1 the 8 2 ka event was the last deglacial abrupt climate event a reduction in the atlantic meridional overturning circulation amoc attributed to the drainage of glacial lake agassiz may have caused the event but the freshwater signature of lake agassiz discharge has yet to be identified in 18o of foraminiferal calcite records from the labrador sea calling into question the connection between freshwater discharge to the north atlantic and amoc strength using mg ca paleothermometry we demonstrate that 3 c of near surface ocean cooling masked an 1 0 decrease in western labrador sea 18o of seawater concurrent with lake agassiz drainage comparison with north atlantic 18o of seawater records shows that the freshwater discharge was transported to regions of deep water formation where it could perturb amoc and force the 8 2 ka event

using relative sea level data to constrain the deglacial and holocene history of southern greenland this paper presents new holocene relative sea level rsl data collected from isolation basins close to the town of paamiut in south west greenland the data shows a rapid fall from a marine limit of c 52 m asl at c 10 9 cal ka bp to close to present by c 9 5 cal ka bp at rates of up to c 32 mm yr falling below present for the majority of the holocene before rising to present in the last 2000 years the elevation of the rsl lowstand is not well constrained but was at least below 3 m this pattern of rapid rsl fall during the early holocene matches the pattern seen at other southern greenland locations suggesting rapid largely simultaneous ice retreat from the area surrounding the qassimiut lobe at the start of the holocene occurring c 2000 years after the initial deglaciation of the extreme southern tip of greenland the rsl histories from this and other southern greenland locations are distinct to those recorded further north along the west coast and are in broad agreement with a pattern of vertical land motion and rsl predicted by the huy2 model simpson et al 2009 which predicts an 80 m drop in the contribution of vertical land motion to rsl at 10 cal ka bp between sisimiut and paamiut on the west coast despite this broad scale spatial agreement between the rsl data and the huy2 model it fails to satisfactorily predict the holocene rsl histories at paamiut and other southern greenland locations sensitivity tests indicate that the data model misfits are most likely due to an over estimate of the forcing during the holocene thermal maximum or the response to this forcing in southern greenland and error in the north american ice sheets component of the background deglaciation model our new data suggests that much of the southern part of the ice sheet acted differently to the area further north however rsl changes at paamiut are also largely impacted by regional and larger scale processes including a bulls eye of uplift centred on the west the impact of the holocene thermal maximum and the influence of the collapse of the north american ice sheets

new gas geothermometers for geothermal exploration calibration and application calibration of five gas geothermometers is presented three of which used co2 h2s and h2 concentrations in fumarole steam respectively the remaining two use co2h2 and h2sh2 ratios the calibration is based on the relation between gas content of drillhole discharges and measured aquifer temperatures after establishing the gas content in the aquifer gas concentrations were calculated in steam formed by adiabatic boiling of this water to atmospheric pressure to obtain the gas geothermometry functions it is shown that the concentrations of co2 h2s and h2 in geothermal reservoir waters are fixed through equilibria with mineral buffers at temperatures above 230 c epidote prehnite calcite quartz are considered to buffer co2 two buffers are involved for h2s and h2 and two functions are therefore presented for the geothermometers involving these gases for waters containing less than about 500 ppm chloride and in the range 230 300 c pyrite pyrrholite epidote prehnite seem to be involved but pyrite epidote prehnite magnetite or chlorite for waters above 300 c and waters in the range 230 300 c if containing over about 500 ppm the gas geothermometers are useful for predicting subsurface temperatures in high temperature geothermal systems they are applicable to systems in basaltic to acidic rocks and in sediments with similar composition but should be used with reservation for systems located in rocks which differ much in composition from the basaltic to acidic ones the geothermometry results may be used to obtain information on steam condensation in upflow zones or phase separation at elevated pressures measured aquifer temperatures in drillholes and gas geothermometry temperatures based on data from nearby fumaroles compare well in the five fields in iceland considered specifically for the present study as well as in several fields in other countries for which data were inspected the results of the gas geothermometers also compare well with the results of solute geothermometers and mixing models in three undrilled icelandic fields

the origin of the upper palaeozoic chanaral melange of n chile the fragmented and mixed strata of the chanaral melange extend for some 220 km from n to s in the coastal ranges of n chile 26 20 to 28 20 s the melange was produced in an accretionary wedge resulting from the ne subduction of the ancestral pacific oceanic plate beneath the gondwana land margin during carboniferous times the melange consists essentially of blocks of sandstone in a pelitic matrix these sediments were deposited as deep sea basin plain turbidites prior to their fragmentation other blocks in the melange include mafic volcanic rocks with the geochemical characteristics of oceanic island basalts and rare shallow marine limestones structures in the melange suggest an origin by two distinct deformation processes involving unlithified sediments initial boudinage and break up of the strata was apparently accomplished by intrastratal movement resulting from imbricate thrusting within the accretionary wedge the second process produced cross cutting zones of breccia which are interpreted as fluid escape conduits resulting from the high pore pressures produced during underthrusting

palaeogene and neogene cold seep communities in barbados trinidad and venezuela an overview palaeogene and neogene fossiliferous carbonates from barbados trinidad and northern venezuela are interpreted to have formed at ancient cold seep sites the hydrocarbon seepage that fuelled these chemosymbiotic ecosystems was related to tectonic activity in the southern caribbean region particularly the subduction of the caribbean plate beneath the north atlantic plate the carbonates and fossils from the scotland district north eastern barbados are eocene miocene in age and are associated with two distinct tectonic units the sub oceanic fault zone and a diapiric melange the sub oceanic fault zone is the tectonic junction between accretionary prism sediments and over lying thrust sheets of fore arc basin sediments the loading of the thrust sheets caused methane rich fluids to be expelled from the accretionary prism sediments and channelled to the sea floor via the sub oceanic fault zone where it supported chemosymbiotic invertebrate communities containing vesicomyid lucinid thyasirid solemyid and nuculanid bivalves a variety of gastropods and possibly vestimentiferan tube worms the diapiric melange is considered to represent sediment that failed under pressure in the accretionary prism and was remobilised as a diapir that extruded onto the sea floor providing a conduit for methane and other hydrocarbons that sustained a chemosynthesis based community of vesicomyid lucinid and nuculanid bivalves and various gastropods the geological setting of fossiliferous carbonates known as freeman s bay limestone in southwest trinidad has been less fully investigated the freeman s bay limestone is a member of the miocene lengua formation which is believed to have formed in a fore deep basin on lapping onto an accretionary prism formed by the subduction of proto caribbean crust beneath the south american plate the carbonates and fossils of the fbl including the bivalves pleurophopsis unioides van winkle 1919 and thyasira adoccasa van winkle 1919 lucinids nuculanids and bathymodiolins and provannid and other gastropods are interpreted to have formed at palaeo seep sites on the accretionary prism little is currently known about the geological setting of the fossils collected from the miocene huso member of the pozon formation from northern venezuela but a seep origin is strongly suspected based on the taxa present like the fossil assemblages from barbados and trinidad the venezuelan material is dominated by vesicomyid bivalves together with lucinid thyasirid bathymodiolin and solemyid bivalves and various gastropods these taxa are characteristics of modern cold seep communities most comparisons between the fossil caribbean and modern seep fauna are necessarily at the generic or family level although in some cases individual species are found at both ancient and modern seep sites for example the gastropod cataegis meroglypta is found in seep carbonate from the sofz of barbados and the fbl of trinidad as well as at modern seeps on the barbados prism at the generic level this study has revealed the first fossil occurrences of abyssochrysos and provanna in the caribbean such temporal and spatial links further the understanding of both local and global patterns of biogeographic distribution of cold seep fauna

the use of mixing models and chemical geothermometers for estimating underground temperatures in geothermal systems abstract application of various chemical geothermometers and mixing models indicate underground temperatures of 260 c 280 c and 265 c in the geysir hveravellir and landmannalaugar geothermal fields in iceland respectively mixing of the hot water with cold water occurs in the upflow zones of all these geothermal systems linear relations between chloride boron and 18o constitute the main evidence for mixing which is further substantiated by chloride silica and sulphate relations in the geysir and hveravellir fields a new carbonate silica mixing model is proposed which is useful in distinguishing boiled and non boiled geothermal waters this model can also be used to estimate underground temperatures using data from warm springs this model as well as the chloride enthalpy model and the na li and co2 gas geothermometers invariably yield similar results as the quartz geothermometer sometimes also does by contrast the na k and the na k ca geothermometers yield low values in the case of boiling hot springs largely due to loss of potassium from solution in the upflow the results of these geothermometers are unreliable for mixed waters due to leaching subsequent to mixing

eddy covariance measurements of hydrothermal heat flux at solfatara volcano italy abstract the first measurements of volcanic hydrothermal water vapor and heat flux using eddy covariance ec were made at solfatara crater italy june 8 25 2001 deployment at six different locations within the crater allowed areas of focused gas venting to be variably included in the measured flux turbulent ec fluxes of water vapor varied between 680 and 11 200 g h2o m 2 d 1 heat fluxes varied diurnally with the solar input and the volcanic component of sensible heat ranged from 25 to 238 w m 2 the highest measurements of both sensible and latent heat flux were made downwind of hot soil regions and degassing pools and during mid day the ratio of average volcanic heat both latent and sensible to co2 flux resulted in an equivalent h2o co2 flux ratio of 2 2 by weight which reflects the deep source h2o co2 gas ratio the amount latent heat flux evaporation was determined to be consistent both with what would be expected from the magnitude of co2 fluxes and the fumarolic h2o co2 ratio as well as with observed surface temperatures and wind speeds given a moist soil this suggests that the water vapor that condenses in the shallow subsurface is remobilized at the soil atmosphere interface through variable evaporation dependent on the deep heat flux and surface temperature the results suggest that ec provides a quick and easy method to monitor average h2o co2 ratios continuously in volcanic regions providing another important tool for volcanic hazards monitoring

abrupt holocene climate transitions in the northern north atlantic region recorded by synchronized lacustrine records in iceland abstract two high sediment accumulation rate icelandic lakes the glacial lake hvitarvatn and the non glacial lake haukadalsvatn contain numerous tephra layers of known age which together with high resolution paleomagnetic secular variations allow synchronization with a well dated marine core from the shelf north of iceland a composite standardized climate record from the two lakes provides a single time series that efficiently integrates multi proxy data that reflect the evolution of summer temperatures through the holocene the first order trends in biogenic silica bsi 13c and c n rise relatively abruptly following deglaciation reaching maximum values shortly after 8 ka following a complex minimum between 8 7 and 8 0 ka the holocene thermal maximum htm in the lakes is marked by all proxies with a sharp transition out of the 8 ka cold event into peak summer warmth by 7 9 ka and continuing warm with some fluctuations until 5 5 ka decreasing summer insolation after the htm is reflected by incremental cooling initially 5 5 ka with subsequent cold perturbations recorded by all proxies 4 3 to 4 0 ka and 3 1 to 2 8 ka the strongest disturbance occurred after 2 ka with initial summer cooling occurring between 1 4 and 1 0 ka followed by a more severe drop in summer temperatures after 0 7 ka culminating between 0 5 and 0 2 ka following each late holocene cold departure bsi re equilibrated at a lower value independent of the sediment accumulation rate some of the abrupt shifts may be related to icelandic volcanism influencing catchment stability but the lack of a full recovery to pre existing values after the perturbation suggests increased periglacial activity decreased vegetation cover and glacier growth in the highlands of iceland the similarity in timing direction and magnitude of our multi proxy records from glacial and non glacial lakes and from the adjacent marine shelf suggests that our composite record reflects large scale shifts in ocean atmosphere circulation throughout the northern north atlantic

holocene environmental variability in southern greenland inferred from lake sediments abstract sediments from qipisarqo lake provide a continuous holocene paleoenvironmental record from southern greenland following deglaciation and glacio isostatic emergence of the basin from the sea 9100 cal yr b p proxies of lake paleoproductivity including biogenic silica and organic matter increased markedly until 6000 cal yr b p and thereafter remained stable over the ensuing warm three millennia subsequent decreases in these proxies most dramatically between 3000 and 2000 cal yr b p show the lake s responses to initial neoglacial cooling intervals of ameliorated limnological conditions occurred between 1300 and 900 and between 500 and 280 cal yr b p briefly interrupting the decreasing trend in productivity that culminated in the little ice age increased lake productivity during the latter half of the 20th century which reflects the limnological response to circum arctic warming still has not reached peak holocene values the neoglacial climate of the last 2000 yr includes the most rapid high amplitude environmental changes of the past nine millennia the norse thus migrated around the north atlantic ocean region in the most environmentally unstable period since deglaciation lacustrine sediment records provide a context with which to consider future environmental changes in the labrador sea region in particular any future warming will be superposed on a regional climate system that is currently exhibiting highly unstable behavior at submillennial timescales

the 1976 1982 strombolian and phreatomagmatic eruptions of white island new zealand eruptive and depositional mechanisms at a wet volcano white island is an active andesitic dacitic composite volcano surrounded by sea yet isolated from sea water by chemically sealed zones that confine a long lived acidic hydrothermal system within a thick sequence of fine grained volcaniclastic sediment and ash the rise of at least 106 m3 of basic andesite magma to shallow levels and its interaction with the hydrothermal system resulted in the longest historical eruption sequence at white island in 1976 1982 about 107 m3 of mixed lithic and juvenile ejecta was erupted accompanied by collapse to form two coalescing maar like craters vent position within the craters changed 5 times during the eruption but the vents were repeatedly re established along a line linking pre 1976 vents the eruption sequence consisted of seven alternating phases of phreatomagmatic and strombolian volcanism strombolian eruptions were preceded and followed by mildly explosive degassing and production of incandescent blocky juvenile ash from the margins of the magma body phreatomagmatic phases contained two styles of activity a near continuous emission of gas and ash and b discrete explosions followed by prolonged quiescence the near continuous activity reculted from streaming of magmatic volatiles and phreatic steam through open conduits frittering juvennile shards from the margins of the magma and eroding loose lithic particles from the unconsolidated wall rock the larger discrete explosions produced ballistic block aprons downwind lobes of fall tephra and cohesive wet surge deposits confined to the main crater the key features of the larger explosions were their shallow focus random occurrence and lack of precursors and the thermal heterogeneity of the ejecta this white island eruption was unusual because of the low discharge rate of magma over an extended time period and because of the influence of a unique physical and hydrological setting the low rate of magma rise led to very effective separation of magmatic volatiles and high fluxes of magmatic gas even during phreatic phases of the eruption while true strombolian phases did occur more frequently the decoupled magmatic gas rose to interact with the conduit walls and hydrothermal system producing phreatomagmatic eruptions the form of these wet explosions was governed by a delicate balance between erosion and collapse of the weak conduit walls if the walls were relatively stable fine ash was slowly eroded and erupted in weak near continous phreatomagmatic events when the walls were unstable wall collapse triggered larger discrete phreatomagmatic explosions

holocene climate changes in southern greenland evidence from lake sediments a holocene lake sediment record is presented from lake n14 situated on angissoq island 15 km off the main coast of southern greenland the palaeoclimatic development has been interpreted on the basis of flux and percentage content of biogenic silica clastic material organic material and sulphur as well as sedimentation rate moss content and magnetic susceptibility a total of 43 radiocarbon dates has ensured a reliable chronology it is argued that varying sediment composition mainly reflects changing precipitation by analogy with the present meteorological conditions in southern greenland holocene climate development is inferred between 11550 and 9300 cal yr bp temperature and precipitation increase markedly but this period is climatically unstable from 9300 yr bp conditions become more stable and a holocene climatic optimum characterised by warm and humid conditions is observed from 8000 to 5000 cal yr bp from 4700 cal yr bp the first signs of a climatic deterioration are observed and from 3700 cal yr bp the climate has become more dry and cold superimposed on the climatic long term trend is climate variability on a centennial time scale that increases in amplitude after 3700 cal yr bp a climatic scenario related to the strength and position of the greenland high pressure cell and the iceland low pressure cell is proposed to explain the holocene centennial climate variability a comparison of the lake n14 record with a terrestrial as well as a marine record from the eastern north atlantic ocean suggests that the centennial climate variability was uniform over large areas at certain times less

heat flux from magmatic hydrothermal systems related to availability of fluid recharge abstract magmatic hydrothermal systems are of increasing interest as a renewable energy source surface heat flux indicates system resource potential and can be inferred from soil co 2 flux measurements and fumarole gas chemistry here we compile and reanalyze results from previous co 2 flux surveys worldwide to compare heat flux from a variety of magma hydrothermal areas we infer that availability of water to recharge magmatic hydrothermal systems is correlated with heat flux recharge availability is in turn governed by permeability structure lithology rainfall topography and perhaps unsurprisingly proximity to a large supply of water such as the ocean the relationship between recharge and heat flux interpreted by this study is consistent with recent numerical modeling that relates hydrothermal system heat output to rainfall catchment area this result highlights the importance of recharge as a consideration when evaluating hydrothermal systems for electricity generation and the utility of co 2 flux as a resource evaluation tool

diffuse volcanic degassing and thermal energy release from hengill volcanic system iceland we report the first detailed study of spatial variations on the diffuse emission of carbon dioxide co2 and hydrogen sulfide h2s from hengill volcanic system iceland soil co2 and h2s efflux measurements were performed at 752 sampling sites and ranged from nondetectable to 17 666 and 722 g m 2 day 1 respectively the soil temperature was measured at each sampling site and used to evaluate the heat flow the chemical composition of soil gases sampled at selected sampling sites during this study shows they result from a mixing process between deep volcanic hydrothermal component and air most of the diffuse co2 degassing is observed close to areas where active thermal manifestations occur northeast flank of the hengill central volcano close to the nesjavellir power plant suggesting a diffuse degassing structure with a ssw nne trend overlapping main fissure zone and indicating a structural control of the degassing process on the other hand h2s efflux values are in general very low or negligible along the study area except those observed at the northeast flank of the hengill central volcano where anomalously high co2 efflux and soil temperatures were also measured the total diffuse co2 emission estimated for this volcanic system was about 1 526 160 t day 1 of which 453 t day 1 29 7 are of volcanic hydrothermal origin to calculate the steam discharge associated with the volcanic hydrothermal co2 output we used the average h2o co2 mass ratio from 12 fumarole samples equal to 88 6 range 9 4 240 2 as a representative value of the h2o co2 mass ratios for hengill fumarole steam the resulting estimate of the steam flow associated with the gas flux is equal to 40 154 t day 1 the condensation of this steam results in thermal energy release for helgill volcanic system of 1 07 1014 j day 1 or to a total heat flow of 1 237 mwt

petrology of the bitumen manjak deposits of barbados hydrocarbon migration in an accretionary prism abstract bitumen manjak deposits in barbados are located particularly along fracture planes including faults and also in calcite veins as veinlets vug fillings and bedding parallel seams in sandstones and as matrix to diagenetic carbonates they occur particularly near the margins of the diapiric joes river formation and in immediately adjacent rocks reflecting the role of diapirism in the migration of hydrocarbon bearing fluids the larger bitumen veins trend between e w and ne sw following the strike of fault bounded packets of the accretionary prism the predominant fabric in the basal complex of barbados that is hydrocarbon migration followed the structural grain petrographic relationships of bitumen with chemosynthetic diagenetic carbonates suggest that hydrocarbon migration was a multi stage process the host sediments to the bitumens were not well consolidated and appear to have been in an overpressured state hydrocarbon generation may have contributed to overpressuring and buoyancy enhanced diapirism the association of bitumens with faults and decollement surfaces suggests that the lubricating action of the bitumen helped to accommodate deformation during diapirism and other processes related to the evolution of the accretionary prism widespread impregnation of sandstones in the joes river formation suggests that hydrocarbon migration was primarily by intergranular flow in a state of low confining pressure and did not depend on migration along the fault planes which may be of a later date

weathering effects on the geotechnical properties of argillaceous sediments in tropical environments and their geomorphological implications outcrops of young sedimentary argillaceous rocks with well developed fabric display rapid changes in their properties when subject to tropical weathering the change in the materials is often accompanied by mass movement activity and the geomorphological consequence in terms of landforms is usually the development of badlands topography detailed field and laboratory studies have been undertaken on the joe s river formation barbados and the lichi melange taiwan both are sedimentary mudrocks with well developed scaly fabrics physical and geotechnical laboratory tests have been conducted on samples collected from type site locations to elucidate associations between material properties earth surface processes and landform development while the inherent physical properties show little or no difference in the transition from unweathered to highly weathered materials by applying the critical state model the mudrock geotechnical properties can be shown to change significantly as weathering commences material strength surprisingly increases only after a period of more extensive weathering do mechanical properties confirm increasingly incompetent materials the initial strength increase appears to be due to weathering induced modification of the fabric the subsequent strength drop is a product of weathering induced modification of both the fabric and the in situ intact sediment it is suggested that by applying the critical state model a greater consideration can be gained of the geotechnical response of the sediments to weathering

anomalously mild younger dryas summer conditions in southern greenland the first late glacial lake sediments found in greenland were analyzed with respect to a variety of environmental variables the analyzed sequence covers the time span between 14400 and 10500 calendar yr b p and the data imply that the conditions in southernmost greenland during the younger dryas stadial 12800 11550 calendar yr b p were characterized by an arid climate with cold winters and mild summers preceded by humid conditions with cooler summers climate models imply that such an anomaly may be explained by local climatic phenomenon caused by high insolation and fohn effects it shows that regional and local variations of younger dryas summer conditions in the north atlantic region may have been larger than previously found from proxy data and modeling experiments

soil co2 emissions as a proxy for heat and mass flow assessment taupō volcanic zone new zealand the quantification of heat and mass flow between deep reservoirs and the surface is important for understanding magmatic and hydrothermal systems here we use high resolution measurement of carbon dioxide flux co2 and heat flow at the surface to characterize the mass co2 and steam and heat released to the atmosphere from two magma hydrothermal systems our soil gas and heat flow surveys at rotokawa and white island in the taup volcanic zone new zealand include over 3000 direct measurements of co2 and soil temperature and 60 carbon isotopic values on soil gases carbon dioxide flux was separated into background and magmatic hydrothermal populations based on the measured values and isotopic characterization total co2 emission rates co2 of 441 84 t d 1 and 124 18 t d 1 were calculated for rotokawa 2 9 km2 and for the crater floor at white island 0 3 km2 respectively the total co2 emissions differ from previously published values by 386 t d 1 at rotokawa and 25 t d 1 at white island demonstrating that earlier research underestimated emissions by 700 rotokawa and 25 white island these differences suggest that soil co2 emissions facilitate more robust estimates of the thermal energy and mass flux in geothermal systems than traditional approaches combining the magmatic hydrothermal sourced co2 emission constrained using stable isotopes with reservoir h2o co2 mass ratios and the enthalpy of evaporation the surface expression of thermal energy release for the rotokawa hydrothermal system 226 mwt is 10 times greater than the white island crater floor 22 5 mwt

neodymium and strontium isotopic constraints on soil sources in barbados west indies abstract neodymium and strontium isotopic compositions and sm nd ratios are used to constrain the sources of silicate rich soils developed on uplifted pleistocene coral reef limestones on barbados west indies the geographic and geologic setting of barbados facilitates the application of these tracers to the evaluation of the following soil sources 1 pleistocene reef limestone regolith 2 tertiary carbonate rocks sandstones and mudstones that are exposed in northeastern barbados 3 volcanic ash erupted from the lesser antilles arc 4 saharan dust transported by trade winds and 5 fertilizer the soils have nd values that range from 6 6 to 1 9 87 sr 86 sr values of 0 70890 to 0 71067 and sm nd ratios of 0 223 0 260 the pleistocene limestone component is the most significant source of sr in the soils and a negligible source of nd comparison of sm and nd concentrations and neodymium isotopic compositions of soil samples that are weathered to varying extents indicates that sm and nd are relatively unfractionated and retained in the soils during weathering nd and sm nd variations in the soils therefore primarily reflect the compositions and proportions of the silicate sources mass balance calculations based on sm nd systematics require that the silicate soil components contain between 30 85 volcanic ash with the remaining silicate fraction comprised of old continentally derived sediment in contrast to sm and nd sr is mobilized and removed from the soils during weathering strontium from volcanic and carbonate sources is preferentially removed relative to continental silicate sources the strontium isotopic compositions of the soils therefore reflect the combined effects of the degree of weathering and the compositions and proportions of the soil sources mass balance calculations indicate that at least 35 60 of the initial sr in the soils has been removed by weathering these results illustrate 1 the utility of radiogenic isotopes in identifying and quantifying soil sources and weathering processes 2 the compositional influence of numerous sources on soils even those developed in a relatively isolated area such as barbados and 3 the domination of barbados soil sm nd systematics by nonregolith eolian components

quartzose turbidites of the accretionary complex of barbados ii variations in bedding styles facies and sequences abstract barbados provides the only subaerial exposures of the barbados ridge an accretionary complex lying outboard of the lesser antilles volcanic arc within nine measured sections of quartzose turbidites five major types of sequences are recognized 1 1 progradational sequences basin plain outer fan of uniformly fine grained flat based base absent turbidites that thicken upward and gradually become coarser grained and base present at the top of the sequence 2 2 a single rejuvenation rapid progradational sequence was identified as an abrupt progradational sequence above abandoned lobe deposits and is not characterized by stacked well developed upward thickening successions as many progradational sequences are 3 3 channelized successions of coarse grained base present turbidites arranged in packets 5 20 or 50 140 m thick which are midfan and inner fan deposits respectively the distinction between predominance of base present and base absent turbidites seems to correspond with the interpreted change from midfan channelized to outer fan sheet flow deposition 4 4 one example of a major retrogradational sequence of midfan deposits above inner fan sandstones has been found on barbados minor sequences of facies retrogradation are relatively common in the outer fan environment where upward thinning sandstone beds overlie upward thickening units to define symmetric sequences 5 5 abandonment successions are major as indicated by massive accumulations of mudstone minor as indicated by abrupt reversals of upward thickening trends in outer fan lobe deposits and cryptic where indicated by thick 4 m bioturbated zones of massive sandstone

source rock and maturation evaluation of the barbados accretionary prism abstract organic material in specimens from surface and downhole sites and samples of oil and gas from barbadian wells were studied for source potential and maturation history the study involved 1 visual examination of the kerogen 2 measurement of total organic carbon content 3 determination of vitrinite reflectance 4 rock eval pyrolysis assay 5 geochemical measurement of pooled and extracted bitumens including carbon isotopic ratios 13 c and 6 gas chromatographic analysis of saturated gaseous hydrocarbons two types of kerogen occur in barbados terrestrial presumably of south american origin and marine planktonic the two types are mixed in most samples the terrestrial kerogens are dominant and occur in all wells in the basal complex and most of its outcrops the planktonic organic matter occurs in exposed melange hemipelagic rocks and rarely in terrigenous turbidites the well specimens do not show significant maturation within the drilled depths suggesting that pooled hydrocarbons originated from deeper levels of the prism and accumulated as a result of migration faults bounding the intraprism thrust sheets probably provided migratory paths for hydrocarbons and water juxtaposed rocks of variable maturity assisted in alteration and biodegradation and led to the formation of structural traps the composition of gases indicates that maturation conditions for gas generation may exist at great depths within the barbados accretionary prism

local glaciers record delayed peak holocene warmth in south greenland abstract local glaciers and ice caps gics respond sensitively and quickly on the scale of decades to centuries to climate variations continuous records of past fluctuations in gic size provide information on the timing and magnitude of holocene climate shifts and a longer term perspective on 21st century glacier retreat although there is broad scale agreement on millennial scale trends in holocene climate variability and fluctuations in local gics in greenland regional variations are only loosely constrained here we present three holocene proglacial lake sediment records from south greenland an area with abundant local glaciers but few holocene length paleoclimate records in addition we use geospatial analysis to model past equilibrium line altitudes elas and thereby constrain the magnitude of ablation season temperature change during the warmest and coolest periods of the holocene physical and geochemical sedimentary characteristics show that two of the proglacial lakes continued to receive glacial meltwater input until 7 3 and 7 1 ka bp the survival of local glaciers implies that south greenland remained relatively cool and that summer temperatures gradually warmed but did not warm well beyond 1 2 c above present in the early holocene in the mid holocene from 7 1 to 5 5 ka bp organic sedimentation at these two sites indicates that local glaciers became very small or more likely melted away completely the glaciers within the third lake s catchment melted away prior to 5 2 ka bp as sediments deposited earlier in the holocene could not be dated at this site we estimate that summer temperatures increased by at least 1 2 1 8 c above present by 7 3 7 1 ka bp our results are consistent with other observations that suggest a north to south gradient in the timing of holocene thermal maximum conditions with southern greenland experiencing a delayed warming relative to other regions in greenland as summer temperatures cooled in the neoglacial our records show that sustained glacier regrowth began 3 1 ka bp with glaciers in the southernmost catchment which at present receive the most precipitation in the other two catchments which host smaller glaciers in a drier environment regrowth began at 1 3 and 1 2 ka bp the timing of which is in agreement with other glacial records from the arctic atlantic region local glaciers reached their maximum late holocene extents during a cooler second phase of the little ice age lia 0 2 0 1 ka bp that we estimate was at least 0 4 0 9 c cooler than present overall these findings improve understanding of the spatio temporal dynamics of holocene glacier and climate change in greenland potentially yielding valuable information about their future response

surface heat flow and co2 emissions within the ohaaki hydrothermal field taupo volcanic zone new zealand abstract carbon dioxide emissions and heat flow have been determined from the ohaaki hydrothermal field taupo volcanic zone tvz new zealand following 20 a of production 116 mw e soil co 2 degassing was quantified with 2663 co 2 flux measurements using the accumulation chamber method and 2563 soil temperatures were measured and converted to equivalent heat flow w m 2 using published soil temperature heat flow functions both co 2 flux and heat flow were analysed statistically and then modelled using 500 sequential gaussian simulations forty subsoil co 2 gas samples were also analysed for stable c isotopes following 20 a of production current co 2 emissions equated to 111 6 7 t d observed heat flow was 70 6 4 mw compared with a pre production value of 122 mw this 52 mw reduction in surface heat flow is due to production induced drying up of all alkali cl outflows 61 5 mw and steam heated pools 8 6 mw within the ohaaki west thermal area ohw the drying up of all alkali cl outflows at ohaaki means that the soil zone is now the major natural pathway of heat release from the high temperature reservoir on the other hand a net gain in thermal ground heat flow of 18 mw from 25 mw to 43 3 5 mw at ohw is associated with permeability increases resulting from surface unit fracturing by production induced ground subsidence the ohaaki east ohe thermal area showed no change in distribution of shallow and deep soil temperature contours despite 20 a of production with an observed heat flow of 26 7 3 mw and a co 2 emission rate of 39 3 t d the negligible change in the thermal status of the ohe thermal area is attributed to the low permeability of the reservoir beneath this area which has limited production mass extraction and sheltered the area from the pressure decline within the main reservoir chemistry suggests that although alkali cl outflows once contributed significantly to the natural surface heat flow 50 they contributed little 2 emissions due to the loss of 99 of the original co 2 content due to depressurisation and boiling as the fluids ascended to the surface consequently the soil has persisted as the major 99 pathway of co 2 release to the atmosphere from the high temperature reservoir at ohaaki the co 2 flux and heat flow surveys indicate that despite 20 a of production the variability in location spatial extent and magnitude of co 2 flux remains consistent with established geochemical and geophysical models of the ohaaki field at both ohw and ohe carbon isotopic analyses of soil gas indicate a two stage fractionation process for moderate flux 60 g m 2 d 1 sites boiling during fluid ascent within the underlying reservoir and isotopic enrichment as co 2 diffuses through porous media of the soil zone for high flux sites 300 g m 2 d 1 the 13 co 2 signature 7 4 0 3 ohw and 6 5 0 6 ohe is unaffected by near surface soil zone fractionation processes and reflects the composition of the boiled magmatic co 2 source for each respective upflow flux thresholds of 2 d 1 for purely diffusive gas transport between 30 and 300 g m 2 d 1 for combined diffusive advective transport and 300 g m 2 d 1 for purely advective gas transport at ohaaki were assigned 13 co 2 values and cumulative probability plots of co 2 flux data both identified a threshold of 15 g m 2 d 1 by which background atmospheric and soil respired co 2 may be differentiated from hydrothermal co 2

white island new zealand volcanic hydrothermal system represents the geochemical environment of high sulfidation cu and au ore deposition the white island volcanic hydrothermal system new zealand is thought to closely represent the chemical conditions that lead to the formation of high sulfidation cu au ore deposits the amounts of cu and au produced over a 10 ka period of activity largely from degassing magma are calculated to be 106 and 45 t respectively altered andesite blocks ejected from recent vents contain alunite anhydrite and pyrite their s isotopic composition indicates vein filling at 380 c at this temperature cu and au are highly soluble in acid solutions which may explain the depletion of cu and absence of au in the ejecta mass balance calculations however suggest that cu and au are precipitated in cooler zones before the acid solutions discharge at the surface

soil diffuse degassing and thermal energy fluxes from the southern lakki plain nisyros greece two diffuse soil co2 flux surveys from the southern lakki plain show that co2 is mainly released from the hydrothermal explosion craters the correspondence between high co2 fluxes and elevated soil temperatures suggests that a flux of hot hydrothermal fluids ascends towards the surface steam mostly condenses near the surface and the heat given off is conductively transferred to the atmosphere through the soil accompanied by a large co2 flux it was calculated that 68 t d 1 of hydrothermal co2 are released through the total surveyed area of 1 3 km admitting that a steam flux of 2200 t d 1 accompanies this co2 flux the thermal energy released through steam condensation amounts to 58 mw

diffuse emission of co2 and convective heat release at nisyros caldera greece abstract the diffuse emission of co2 from the south east sector of nisyros caldera lakki plain has been measured during a detailed survey 1400 soil co2 flux measurements performed in october 2018 the gas emissions are fed by hydrothermal sources and in minor part by the soil biogenic activity whose mean co2 flux 4 g m 2 d 1 is here estimated for the first time the total amount of hydrothermal co2 reaches 92 8 t d a value that is slightly higher than that estimated with the same method between 1999 and 2001 74 7 t d the gas is emitted by different diffuse degassing structures ddss including volcanic hydrothermal structures craters and domes and ne sw and nw se trending tectonic lineaments even if the total co2 emission is not particularly high at nisyros close to the median of co2 emissions measured in volcanoes worldwide the process is very energetic the thermal energy associated with the shallow condensation of the steam in the ddss reaches 60 mw while we estimate at 134 270 mw the total amount of thermal energy involved in the convective rising of the deep geothermal liquids that transport the gas from the depth toward the surface this large flux of energy could dramatically increase during future earthquakes by addition of heat and mass from a deep hydrothermal reservoir potentially triggering hydrothermal explosions as it happened several times in the past few centuries

a complete record of holocene glacier variability at austre okstindbreen northern norway an integrated approach arctic glaciers are currently undergoing major changes but accurate knowledge about how they varied during the entire holocene is still scarce here we present a new complete glacier record from austre okstindbreen in nordland northern norway this reconstruction is based on a number of short and long cores retrieved from several downstream basins which have been analyzed by a suite of methods including geochemical elements xrf rock magnetic properties dry bulk density dbd and loss on ignition loi lake sediment distribution was surveyed and mapped prior to coring by the use of ground penetrating radar gpr independently lichen dated marginal moraines and historical information about the glacier frontal positions from old photographs and maps have made it possible to link the moraine sequence to the 210pb dated lake sediment chronology this integrated approach reveals that austre okstindbreen is the first known glacier in scandinavia to possibly have survived the holocene thermal optimum it also brackets the four largest glacier advances to c 7400 7000 1400 1200 900 700 and 300 150 years before ad 2000 b2k in contrast to most reconstructed glaciers in scandinavia the largest glacier advance was not associated with the little ice age but rather to an earlier period centred at 1300 b2k both the moraine chronology and the lacustrine records document this neoglacial advance compared to other glacier reconstructions from the northern hemisphere we identify near synchronous glacier advances occurring roughly at 4000 b2k 2700 b2k 1300 b2k and during the little ice age these correlative advances across the northern hemisphere suggest that these observed centennial scale events are a shared feature regardless of the large geographical distances separating them some minor discrepancies between different geographical areas may be caused by lack of precise dating but local climatic conditions may play a role as well

volume loss and defluidization history of barbados the basal complex of barbados island is a tectonic amalgam of eocene strata accreted at an outer deformation front at the end of eocene time the structures and porosity depth function of such sediments give clues to the succession of pore volume loss episodes each of which must have been accompanied by defluidization the basal complex evolved as a perpetually shallow low temperature mass which underwent little or no unroofing in its 36 m y history in the accretionary prism in its early phase of deformation the accretionary structure formed by thrust imbrication perhaps with little concurrent volume loss burial compaction followed tectonic thickening during accretion causing probable large pore volume loss within limits of 0 70 of the initial volume of the imbricate stack a late phase of tectonics has affected barbados and a wide region of the structural high since 20 ma such tectonics reactivated faults in the basal complex which acted as channelways for deep seated and perhaps shallow fluids to emerge from the structural high the late stage tectonics also caused local basins for deposition of sediment cover and emplacement of thrust nappes of forearc basin strata above the basal complex such top loading caused a renewed phase of burial compaction and loss of about 37 or more of the pore volume that existed at the onset of late stage tectonics

mud diapirism and subcretion in the barbados ridge accretionary complex the role of fluids in accretionary processes mud diapirism has recently been recognized in several modern accretionary wedges it provides an important means of dewatering accretionary wedges and should be regarded as an important process for producing the melanges found in both modern and ancient accretionary terranes mud diapirism affects a large area of the barbados ridge accretionary complex the distribution of the mud diapirs appears to be primarily controlled by the presence of underconsolidated terrigenous submarine fan deposits that are being accreted to the complex the frequency of diapir occurrence decreases northward as the fan becomes thinner mud diapirs are absent from the very eastern most part of the complex formed from sediments accreted at its toe with the exception of a few mud volcanoes on the ocean floor in front of the complex the initiation of diapirism appears to be spatially coincident with the onset of subcretion or underplating of sediment to the base of the complex at a ramp between two levels of decollement it is proposed that the release of mud and pore water from the subcreted sediments is a direct or indirect cause of most of the mud diapirism in the accretionary complex there is a range of diapiric form dependent on the viscosity of the mud from mud volcanoes fed by low viscosity mud to higher viscosity mud ridges the diapirs in the eastern areas of the complex are generally mud volcanoes with narrow conduits feeding a surface mound mud ridges are prominent in the western parts of the complex this is interpreted as reflecting a general westward decrease in the fluid content of the accretionary complex bottom simulating seismic reflectors formed by gas hydrate are commonly developed in the areas of mud volcano occurrences the presence of the hydrate indicates that large volumes of methane are being generated at depth in these regions the generation of methane may be contributing to zones of overpressuring in the wedge methane may also be partly responsible for driving the diapiric material to the surface to form mud volcanoes ridges in the subducting oceanic crust beneath the accretionary complex locally enhance diapirism above their crests and southern flanks faults formed later in the development of the complex are more commonly associated with diapirism than those resulting from accretion at the toe of the wedge these later faults play an important role in controlling the sites of individual mud volcanoes chains of mud volcanoes and mud ridges

spatial and temporal variability of holocene temperature in the north atlantic region the early holocene climate of the north atlantic region was influenced by two boundary conditions that were fundamentally different from the present the presence of the decaying laurentide ice sheet lis and higher than present summer solar insolation in order to assess spatial and temporal patterns of holocene climate evolution across this region we collated quantitative paleotemperature records at sub millennial resolution and synthesized their temporal variability using principal components analysis pca the analysis reveals considerable spatial variability most notably in the time transgressive expression of the holocene thermal maximum htm most of the region but especially areas peripheral to the labrador sea and hence closest to the locus of lis disintegration experienced maximum holocene temperatures that lagged peak summer insolation by 1000 3000 years many sites from the northeastern north atlantic sector including the nordic seas and scandinavia either warmed in phase with maximum summer insolation 11 000 9000 years ago or were less strongly lagged than the baffin bay labrador sea region these spatially complex patterns of holocene climate development which are defined by the pca resulted from the interplay between final decay of the lis and solar insolation forcing

barbados maturation source rock potential and burial history within a cenozoic accretionary complex abstract a number of diagenetic properties were studied in sedimentary rocks exposed along a 25 km across strike transect on barbados the crest of the barbados accretionary complex the island of barbados consists of three structural levels a lower mostly eocene or undated basal complex composed of quartzose turbidites hemipelagites and melange an intermediate level eocene to miocene of nappes composed mostly of calcareous pelagite and a pleistocene coral cap diagenetic studies concentrated on the basal complex although preliminary data from the nappes are also presented the following subjects were studied 1 clay mineralogy illite interlayers in mixed layer clays 2 vitrinite reflectance 3 organic type and maturation by rock eval pyrolysis 4 thermal alteration index of spores and pollen 5 dry bulk density 6 silica mineralogy taken together the data can be interpreted to indicate maximum temperatures attained during diagenesis of less than 80 c based on a uniform palaeogeothermal gradient of 15 c km 1 and a temperature at the sediment water interface of 10 c maximum burial depths of basement complex rocks were about 2 5 km minimum possible burial depths are 1 and are immature organic matter was derived mostly from terrigenous or oxidized sources type iii kerogens although some marine planktonic sources are indicated locally type ii kerogens organic matter is therefore primarily gas prone

diffuse emission of co2 from the fossa crater vulcano island italy numerous measurements of co2 degassing from the soil carried out with the accumulation chamber method indicate that in the period april july 1995 the upper part of the fossa cone released a total output of 200 t d 1 of co2 which corresponds to approximately 1000 t d 1 of steam these large amounts of fluids are of the same order of magnitude as those released by the high temperature fumarolic field located inside the crater the spatial distribution of soil gas fluxes shows that the main structures releasing co2 are the inner slopes of the crater and a nw se line located ne of the crater rim which correspond to the main direction of vulcano island active faults the comparison of the co2 maps with the soil temperature distribution derived from both direct measurements and airborne infrared images indicates the occurrence of extensive condensation of fumarolic steam within the upper part of the fossa cone whose total amount is comparable to the rainfall budget part of the condensate which originates from this process contributes to the recharge of the phreatic aquifer of porto plain modifying the chemical and isotopic composition of the groundwater

multibeam study of the flores backarc thrust belt indonesia using the seamarc ii seafloor mapping tool in conjunction with closely spaced seismic reflection profiles we have mapped a segment of the flores back arc thrust zone structural irregularities along the deformation front of the thrust zone result from changing stratigraphy and basement structure of the lower plate ne trending faults cutting the outer slope of the flores basin are easily mapped because they truncate dense drainage patterns obliquely mud diapirs probably indicating elevated fluid pressures have formed throughout the accretionary wedge but appear to be concentrated as do back arc thrust earthquakes at the ends of thrust faults the overall orientation of the deformation front of the accretionary wedge is 100 suggesting a nne sense of thrust motion and supporting an origin of the thrust zone by collision of the arc with australia rather than by magmatic forcing or gravitational sliding or spreading orientations of faults and folds close to the arc are not consistent with the trends of the frontal thrusts however and the difference may be due to either different initial orientations or to later rotations of structural features as the accretionary wedge grew

the tectonic fabric of the barbados ridge accretionary complex abstract a map showing near surface structure and other surficial geological features on the barbados ridge accretionary complex has been constructed from gloria long range side scan sonographs detailed bathymetric surveys using seabeam and single and multichannel seismic reflection sections the map shows major variations in the size orientation and style of structures across the accretionary complex that are principally related to the increasing thickness of the complex and the sediment drape upon it and variations along the complex that derive from the northward thinning of sediment accreted from the ocean floor and the effects of ridges in the oceanic basement the development of crossfaulting is mainly associated with basement ridges mud diapirism is abundant in the southern part of the complex and is characteristic of that part of the complex into which turbidites from the orinoco submarine fan are accreted slumping on a variety of scales is another feature of the complex the map is presented at a scale of 1 1063415 4 inches per degree of longitude and also shows bathymetry at 200 m contour intervals

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

geothermal mineral equilibria the dominant reaction determining the chemistry of fluids in a geothermal system of the new zealand type consists of the conversion of primary plagioclase by co2 to calcite and clays with log pco2 15 26 7850 t 273 2 temperature t in c subsequent reactions involving secondary minerals control relative co2 h2s contents the distribution of mineral phases throughout a geothermal system reflects the stepwise conversion of thermodynamically unstable primary phases through a series of intermediate metastable phases to a thermodynamically stable secondary assemblage the relative stabilities of these phases was evaluated on the basis of their solubilities the least soluble aluminiumsilicate representing the thermodynamically most stable phase under a given set of conditions observed assemblages of secondary minerals in geothermal systems represent indicators allowing mineral fluidinteraction conditions to be evaluated on the basis of multi component mineral stability diagrams

mass balance and equilibrium line altitudes of glaciers in high mountain environments abstract the mass balance characteristics of glaciers in high mountain environments complicate the relationship between glacier equilibrium line altitudes elas and climatic variables such as precipitation and air temperature therefore methods of ela reconstruction employed in low relief environments are commonly not applicable in high mountains or require some modification we review the concept of the ela with reference to the mass balance of a range of glacier types found in high mountain regions we examine the applicability of several commonly used methods of ela reconstruction for different glacier types and propose some general principles to guide the choice of appropriate methods

the lacustrine sedimentary sequence in sygneskardvatnet western norway a continuous high resolution record of the jostedalsbreen ice cap during the holocene abstract two lacustrine sediment cores from sygneskardvatnet sunndalen confirm that at least the northern part of the jostedalsbreen ice cap melted away during the atlantic chronozone between 6475 and 5300 14 c yr bp 7340 and 6150 cal bp possibly interrupted for short intervals of glacier activity around 6000 and 5800 14 c yr bp 6900 and 6700 cal bp prior to this periods of glacier expansion culminated at ca 8500 8400 8200 7750 7600 and 7400 cal bp the 8400 8200 cal bp advances are correlated with the widespread 8200 event finse event recorded in greenland ice cores lacustrine and proglacial sites and marine sediments during the early part of the holocene periods of glacier contraction culminated at ca 8450 8300 7900 7500 and 6250 cal bp of which the last represents climatic optimum conditions lowest supply of minerogenic sediments and or highest organic production the sedimentary record also shows that the ice cap has existed continuously since 5300 14 c yr bp 6150 cal bp neoglaciation involved three main phases 1 6150 4500 cal bp 2 4500 2700 cal bp 3 2700 cal bp to the present and a series of low amplitude glacier advances which occurred at 6000 5800 5700 5600 5500 5200 5100 4900 4800 4700 4550 4450 4300 4200 4150 4050 4000 3900 3800 3550 3300 2550 2450 2350 2250 2150 2000 1800 1700 1600 1400 1300 1150 1050 and the 1000 cal bp including the little ice age loss on ignition analyses indicate however that episodes of less glacier activity occurred during the mid and late holocene at around 5900 5800 5550 5450 5300 5050 4850 4750 4500 4400 4100 3950 3700 3450 3100 2650 2500 2400 2300 2200 1850 1700 1550 1350 1250 1050 1000 cal bp and during the twentieth century altogether the lacustrine record from sygneskardvatnet indicates that the holocene has been interrupted by 41 periods of increased glacier activity mean return period of ca 150 years and by 36 events of glacier contraction mean return period of 210 years spectral analysis of the loi data show peaks at periods of about 50 85 110 250 285 500 and 2000 calendar years the mean time resolution in core sygneskardvatnet 2 is ca 20 yr cm 1 while the mean sedimentation rate is 0 5 mm yr 1

the fluid geochemistry of icelandic high temperature geothermal areas abstract icelandic high temperature geothermal systems are considered to number thirty three thereof three are submarine and seven subglacial all are briefly described but the chemistry of fluids from twenty four of them is considered the fluid in the three submarine areas and those four on land that are closest to the sea are relatively saline but to a differing extent mixed with groundwater the rest contain dilute fluids the fluids of the central highland systems are mostly locally derived but may in some instances be quite old whereas those in the northerly krafla area which is inland and the oxarfjor ur area which is close to the sea appear to be a mixture of local and central highland water but those in the inland hengill geysir namafjall and theistareykir areas appear to have travelled relatively long distances from the central highlands the gas observed is magmatic except in the northerly oxarfjordur area close to the sea where it is apparently derived from organic sediments

a new present day temperature parameterization for greenland near surface air temperature 2 m over the greenland ice sheet gris is parameterized using data from automatic weather stations located on land and on the ice sheet the parameterization is expressed in terms of mean annual temperatures and mean july temperatures both depending linearly on altitude latitude and longitude the temperature parameterization is compared to a previous study and is shown to be in better agreement with observations the temperature parameterization is tested in a positive degree day model to simulate the present 1996 2006 mean melt area extent of the gris the model accounts for firn warming rainfall and refreezing of meltwater with different degree day factors for ice and snow under warm and cold climate conditions the simulated melt area extent is found to have reasonable agreement with satellite derived observations

structure of the accretionary complex of barbados ii bissex hill this is the second of a series concerning the accretionary complex that is exposed on the island of barbados and is thought to represent the lesser antilles fore arc at its structural high two principle tectonostratigraphic elements are present in the bissex hill area a basal complex composed of east northeast striking generally steeply dipping fault bound packages of terrigenous sandstones and mudstones mostly turbidites hemipelagic rocks and melange that complex is overlain by the bissex hill nappe composed of calcareous pelagic rocks crystalline limestone and foraminiferal arenite also present in the basal complex are smaller fault bound packages termed micropackets composed of brecciated basal complex lithologies basal complex faults are cut by the bissex hill nappe except on the southern margin of the bissex hill nappe where melange and hemipelagic lithologies apparently have been faulted over the nappe rocks this youngest faulting may be driven by holocene and older melange diapirism structural evolution of terrigenous and probably hemipelagic rocks in basal complex fault packages is characterized by coaxial deformation about southwest trending axes melange packages possibly experienced greater strain as evidenced by girdled fold axes and axial planes and foliations of constant orientation packet bounding faults probably developed during early folding and probably represent surfaces against which packet contents contracted micropackets are the result of motions after the assembly of major packets and are formed through fault imbrication and or diapiric injection rocks of the bissex hill nappe experienced folding first about a north trending axis followed by folding about a southwest trending axis and gentle folding on the entire nappe about an east northeast trending axis deformation in the basal complex is thought to have occurred by progressive accretion of sediment packets the bissex hill nappe is thought to represent a fore arc basin complex thrust over the accretionary complex quartzose sandstones present in the bissex hill nappe that probably had their source in the basal complex indicate that the accretionary complex probably shoaled by the miocene

co 2 flux geothermometer for geothermal exploration abstract a new geothermometer tco2 flux is proposed based on soil diffuse co2 flux and shallow temperature measurements made on areas of steam heated thermally altered ground above active geothermal systems this co2 flux geothermometer is based on a previously reported co2 geothermometer that was designed for use with fumarole analysis the new geothermometer provides a valuable additional exploration tool for estimating subsurface temperatures in high temperature geothermal systems mean tco2 flux estimates fall within the range of deep drill hole temperatures at wairakei new zealand tauhara new zealand rotokawa new zealand ohaaki new zealand reykjanes iceland and copahue argentina the spatial distribution of geothermometry estimates is consistent with the location of major upflow zones previously reported at the wairakei and rotokawa geothermal systems tco2 flux was also evaluated at white island new zealand and reporoa new zealand where limited sub surface data exists mode tco2 flux at white island is high 320 c the highest of the systems considered in this study however the geothermometer relies on mineral water equilibrium in neutral ph reservoir fluids and would not be reliable in such an active and acidic environment mean tco2 flux at reporoa 310 c is high which indicates reporoa has a separate upflow from the nearby waiotapu geothermal system an outflow from waiotapu would not be expected to have such high temperature

holocene fluctuations of bregne ice cap scoresby sund east greenland a proxy for climate along the greenland ice sheet margin abstract the greenland ice sheet is a major component of the arctic cryosphere and the magnitude of its response to future climate changes remains uncertain longer term records of climate near the ice sheet margin provide information about natural climate variability and can be used to understand the causes of past changes in the greenland ice sheet as a proxy for holocene climate near the ice sheet margin we reconstruct the fluctuations of bregne ice cap in the scoresby sund region of central east greenland bregne is a small ice cap 2 5 km 2 in area and responds sensitively to summer temperatures we employ a multi proxy approach to reconstruct the ice cap fluctuations using geomorphic mapping 10 be ages of boulders and bedrock and lake sediment records past extents of bregne ice cap are marked by moraines and registered by sediments in downvalley lakes 10 be ages of bedrock and boulders outboard of the moraines indicate that bregne ice cap was within 250 m of its present day limit by at least 10 7 ka multi proxy data from sediments in two move lake located downvalley from bregne ice cap indicate that the ice cap likely completely disappeared during early and middle holocene time increasing magnetic susceptibility and percent clastic material from 6 5 to 1 9 cal ka bp in two move lake sediments suggest progressively colder conditions and increased snow accumulation on the highlands west of the lake laminated silt deposited at 2 6 cal ka bp and 1 9 cal ka bp to present registers the onset and persistence of bregne ice cap during the late holocene 10 be ages of boulders on an unweathered unvegetated moraine in the bregne ice cap forefield range from 0 74 to 9 60 ka the youngest 10 be age 0 74 ka likely represents the age of the moraine whereas older ages may be due to 10 be inherited from prior periods of exposure this late holocene moraine marks the second largest advance of the ice cap since deglaciation of the region at the end of the last ice age the oldest moraine in the forefield dates to 2 6 cal ka bp the fluctuations of bregne ice cap were likely influenced by northern hemisphere summer insolation throughout the holocene and abrupt late holocene cold events

fission track evidence for the source of accreted sandstones barbados a part of the accretionary wedge associated with the lesser antilles arc system is exposed in an area of approximately 50 km in northeastern barbados zircon separates from sandstones collected from the scotland district barbados w i were analyzed using the fission track technique in order to assess the spectrum of source areas from which these terrigenous sediments were derived and to better constrain the timing of deposition results yielded a mixture of ages with strong groupings from 25 80 ma 200 350 ma and greater than 500 ma the youngest population indicates that some of the scotland beds previously dated by paleontologic methods as eocene may actually be as young as late oligocene possible source areas include the lesser antilles arc the netherlands venezuelan antilles arc and the caribbean mountains of venezuela the 200 350 ma population may reflect partially annealed cratonic material an andean component and or material associated with a triassic rifting event the oldest zircons 500 ma and metamict zircons were likely derived from the south american craton detrital feldspars separated from sandstone at the base of chalky mount were analyzed by the 40ar 39ar age spectrum technique results yield what is interpreted to be a slow cooling gradient from 1350 ma to 925 ma and provides additional evidence of a cratonic source for the accreted sediments based on results from this study and paleogeographical constraints it is proposed that source areas for the scotland sandstones of barbados may have included the guayana shield central cordillera uplifted areas of coastal south america and the lesser antilles volcanic arc we speculate that in late oligocene time an immense proto orinoco river system flowed in a northeasterly direction from the shield through the northern venezuelan mountain system cordillera de la costa and araya paria finally emerging into the caribbean sea in the area now occupied by unare depression sediments comprising this deltaic complex and deep sea fan were either deposited directly into the trench or onto the sea floor where they were soon after caught up in the accretionary wedge of the lesser antilles arc system this article contains supplementary material

carbon dioxide diffuse emission and thermal energy release from hydrothermal systems at copahue caviahue volcanic complex argentina abstract the north western sector of caviahue caldera argentina close to the active volcanic system of copahue is characterized by the presence of several hydrothermal sites that host numerous fumarolic emissions anomalous soil diffuse degassing of co2 and hot soils in march 2014 measurements of soil co2 fluxes in 5 of these sites namely las maquinas las maquinitas i las maquinitas ii anfiteatro and termas de copahue allowed an estimation that 165 t of deeply derived co2 is daily released the gas source is likely related to a relatively shallow geothermal reservoir containing a single vapor phase as also suggested by both the geochemical data from the 3 deep wells drilled in the 1980s and gas geoindicators applied to the fumarolic discharges gas equilibria within the h c o gas system indicate the presence of a large probably unique single phase vapor zone at 200 210 c feeding the hydrothermal manifestations of las maquinas las maquinitas i and ii and termas de copahue a natural thermal release of 107 mw was computed by using co2 as a tracer of the original vapor phase the magmatic signature of the incondensable fumarolic gases the wide expanse of the hydrothermal areas and the remarkable high amount of gas and heat released by fluid expulsion seem to be compatible with an active magmatic intrusion beneath this portion of the caviahue caldera