recent warming in eastern canada inferred from geothermal measurements borehole temperature measurements from several sites in eastern canada were analyzed to determine recent step changes in ground surface temperature inversion of the data suggests a warming by 1 to 2 c in the last 100 years for most of the sites analyzed

anatomy of a late quaternary carbonate island constraints on timing and magnitude of sea level fluctuations west caicos turks and caicos islands bwi abstract the data set of the island of west caicos consists of a combination of high resolution lidar and digital imagery radiometric data and amino acid racemization aar d l values as well as extraordinary preservation of sedimentary and bio constructed deposits on the island together with a well established regional stratigraphic framework from the neighboring bahamian island chain and detailed field mapping the west caicos data set provides an opportunity to advance our understanding of the link between carbonate stratigraphy and the controlling parameters of sea level sediment supply tectonics and climate the exceptionally well preserved stratigraphic record of the mid late pleistocene from west caicos allows recognition of marine isotope stages mis 9 11 5e and holocene the west coast of the island provides a continuous 8 4 km exposure of the mis 5e record that enhances our understanding of the intra mis 5e bipartite succession in this region and supports a sea level lowering that occurred during the last interglacial lig west caicos accreted as a series of eolian foreshore shoreface barrier reef and fringing reef facies shoreline positions for all but the mis 7 and mis 5a c deposits are now captured in the sub meter geodetic quality topobathy lidar survey the star town unit of mis 9 11 age forms the southern margin of the island as well as the central karst modified spine with uranium thorium u th coral ages of between 368 and 365 thousand years ago ka and a d l glu average of 0 60 early mis 5e strata include the railroad ridge unit in the center of the island which was previously identified as one of the older units the railroad ridge unit is a north south linear dune ridge that has a d l glu average of 0 52 and indicates the onset of sediment sources from the east associated with a flooded central caicos platform approximately synchronously the early mis 5e south reef unit 3 75 4 m sea level elevation nucleated on the western coast of west caicos attached to the middle pleistocene star town unit the south reef corals yield an average coral u th age of 126 5 ka with an average d l glu from skeletal matrix of 0 46 this transitional barrier fringing reef is unconformably overlain by the late mis 5e boat cove unit corals in the basal transgressive phase of this upper mis 5e boat cove unit yield an average 120 6 ka u th and average d l glu of 0 45 shallow marine foreshore and eolian facies of the late mis 5e rest on a wave cut terrace that cuts the early mis 5e south reef unit by as much as 3 m down to a 0 5 m above present sea level elevation the upper mis 5e boat cove unit displays a maximum of 4 5 m elevation above present day sea level measured from the middle of the foreshore this estimate may be a minimum value as the exposures on the west coast are part of a forced regressive foreshore sequence last stages of the upper mis 5e deposition are seen in a series of regressive dune beach ridge deposits referred to as the northeast ridges unit with sea level positions ranging from 4 5 m early in the central part of west caicos to 0 5 m on the far northeast coast eventually building down below present day sea level this sea level history fits well with previously documented records in the bahamas and globally and the extensive erosion supports a short lived between 126 and 120 ka intra mis 5e relative sea level fall holocene deposition on west caicos is restricted to northern and eastern margins of the island as a combination of strandplain and dune ridge mixed skeletal oolitic units using the high resolution digital elevation model dem and linked digital geologic map makes it possible to compare areas of the different pleistocene and holocene units quantitatively and to constrain volumetric assessments and accumulation rates on the island for different units the peak sediment volume production accumulation rate between 6 5 and 8 106 m3 or between 2 2 and 2 7 106 m3 per ka is observed in the upper mis 5e unit this rate is 5 times greater than the 0 5 106 m3 per ka estimated for the holocene ooid dune ridge strandplain complex suggesting that the combination of higher sea level greater wave and wind energy and warmer ocean temperatures may have fostered the higher rate of chemically precipitated sediment supply

simulation and inversion of borehole temperature profiles in surrogate climates spatial distribution and surface coupling a heat conduction forward model driven by ground surface temperature from three 1000 year climate simulations with the state of the art echo g model has been used to simulate underground temperature perturbation profiles an inversion approach has been applied to reconstruct ground surface temperature histories from the simulated profiles and to compare them with the climate model temperatures results support the skill of borehole inversion methods to retrieve long term temperature trends and the robustness of using the present day borehole network for reconstructing sat variations

fluid geochemistry and geothermometry in the unexploited geothermal field of the vicano cimino volcanic district central italy abstract the vicano cimino volcanic district vcvd is related to the post orogenic magmatic activity of the peri tyrrhenian sector of central italy the chemical and isotopic compositions of 333 water discharges and 25 gas emissions indicate the occurrence of two main sources 1 cold ca hco 3 to ca na k hco 3 type waters from relatively shallow aquifers hosted in volcanic and sedimentary formations and 2 thermal ca so 4 hco 3 type waters located in a deep co 2 pressurized reservoir hosted in carbonate evaporite rocks and separated from the shallow aquifers by thick sequences of low permeability formations carbon dioxide is mainly produced by thermal metamorphic decarbonation within the deepest and hottest parts of the carbonate evaporite reservoir 13 c co 2 from 3 1 to 2 2 vs vpdb likely affected by a mantle rooted co 2 release of co 2 rich gases from the deep aquifer into the overlying shallow aquifers produces high co 2 springs and bubbling pools the spatial distribution of thermal waters and co 2 rich cold discharges is strongly controlled by fractures and faults located in correspondence with buried structural highs stable isotopes d and 18 o suggest that meteoric water feeds both the shallow and deep reservoirs the relatively low r r a values 0 27 1 19 indicate that he is mainly deriving from a crustal source with minor component from the mantle affected by crustal contamination related to the subduction of the adriatic plate consistently relatively high n 2 ar and n 2 3 he ratios and positive 15 n n 2 values from 0 91 to 5 7 vs air characterize the vcvd gas discharges suggesting the occurrence of a significant excess nitrogen isotopic compositions of ch 4 13 c ch 4 and d ch 4 values from 28 9 to 22 1 vs vpdb and from 176 to 138 vs vsmow respectively and composition of light alkanes are indicative of prevalent thermogenic ch 4 although the occurrence of abiogenic ch 4 production cannot be excluded the 34 s h 2 s values from 9 3 to 11 4 vs vcdt are consistent with the hypothesis of h 2 s production from thermogenic reduction of triassic anhydrites gas geothermometry in the h 2 o h 2 ar h 2 s system suggests that the vcvd gases equilibrated in a liquid phase at redox conditions controlled by interactions of fluids with the local mineral assemblage at temperatures lower 2000 m geothermal wells this confirms that secondary processes i e steam condensation gas dissolution in shallow aquifers re equilibration at lower temperature and microbial activity significantly affect the chemistry of the uprising fluids thermal water chemistry supports the occurrence in this area of an anomalous heat flow that coupled with the recent demographic growth makes this site suitable for direct and indirect exploitation of the geothermal resource in agreement with the preliminary surveys carried out in the 1970 s 1990 s for geothermal exploration purposes

temperature trends over the past five centuries reconstructed from borehole temperatures for an accurate assessment of the relative roles of natural variability and anthropogenic influence in the earth s climate reconstructions of past temperatures from the pre industrial as well as the industrial period are essential but instrumental records are typically available for no more than the past 150 years therefore reconstructions of pre industrial climate rely principally on traditional climate proxy records each with particular strengths and limitations in representing climatic variability subsurface temperatures comprise an independent archive of past surface temperature changes that is complementary to both the instrumental record and the climate proxies here we use present day temperatures in 616 boreholes from all continents except antarctica to reconstruct century long trends in temperatures over the past 500 years at global hemispheric and continental scales the results confirm the unusual warming of the twentieth century revealed by the instrumental record but suggest that the cumulative change over the past five centuries amounts to about 1 k exceeding recent estimates from conventional climate proxies the strength of temperature reconstructions from boreholes lies in the detection of long term trends complementary to conventional climate proxies but to obtain a complete picture of past warming the differences between the approaches need to be investigated in detail

geochemistry of water and gas discharges from the mt amiata silicic complex and surrounding areas central italy abstract the mt amiata volcano in central italy is intimately related to the post orogenic magmatic activity which started in pliocene times major trace elements and isotopic composition of thermal and cold spring waters and gas manifestations indicate the occurrence of three main reservoir of the thermal and cold waters in the mt amiata region the deepest one is located in an extensive carbonate reservoir buried by thick sequences of low permeability allochthonous and neo autochthonous formations thermal spring waters discharging from this aquifer have a neutral ca so4 composition due to the presence of anhydrite layers at the base of the carbonate series and possibly to absorption of deep derived h2s with subsequent oxidation to so42 in a system where ph is buffered by the calcite anhydrite pair marini and chiodini 1994 isotopic signature of these springs and n2 rich composition of associated gas phases suggest a clear local meteoric origin of the feeding waters and atmospheric o2 may be responsible for the oxidation of h2s the two shallower aquifers have different chemical features one is ca hco3 in composition and located in several sedimentary formations above the mesozoic carbonates the other one has a na cl composition and is hosted in marine sediments filling many post orogenic nw se trending basins strontium ba f and br contents have been used to group waters associated with each aquifer although circulating to some extent in the same carbonate reservoir the deep geothermal fluids at latera and mt amiata and thermal springs discharging from their outcropping areas have different composition na cl and ca so4 type respectively considering the high permeability of the reservoir rock the meteoric origin of thermal springs and the two different composition of the thermal waters self sealed barriers must be present at the boundaries of the geothermal systems the complex hydrology of the reservoir rocks greatly affects the reliability of geothermometers in liquid phase which understimate the real temperatures of the discovered geothermal fields more reliable temperatures are envisaged by using gas composition based geothermometers bulk composition of the 67 gas samples studied seems to be the result of a continuous mixing between a n2 rich component of meteoric origin related to the ca so4 aquifer and a deep co2 rich component rising largely along the boundaries of the geothermal systems nitrogen rich gas samples have nearly atmospheric n2 ar 83 and 15 n 14 n 0 ratios whereas co2 rich samples show anomalously high 15n values up to 6 13 likely related to n2 from metamorphic schists lying below the carbonate formations on the basis of average 13 c 12 c isotopic ratio 13c around 0 co2 seems to originate mainly from thermometamorphic reactions in the carbonate reservoir and or in carbonate layers embedded in the underlying metamorphic basement distribution of 3 he 4 he isotopic ratios indicates a radiogenic origin of helium in a tectonic environment that in spite of the presence of many post orogenic basins and mantle derived magmatics can presently be considered in a compressive phase

hydrogeochemistry and strontium isotopes in the arno river basin tuscany italy constraints on natural controls by statistical modeling summary in this paper the chemistry of major and trace elements and for the first time strontium isotopic ratios measured in running waters from the arno river basin tuscany central northern italy and thermal springs discharging in the same hydrographic system are presented and discussed classical graphical methods e g mixing diagrams have here been improved to identify in a correct statistical sample space extreme chemical compositions attributable to the action of geochemical processes and or inherited from specific lithologies namely contributions or components 1 2 and 3 to be used in inverse modeling procedures due to the absence of clear end members a linear least squares problem with non negativity constraints and distances as required for compositional data convex linear mixing was solved by considering the contribution of the most discriminant variables given by the 87 sr 86 sr isotopic ratios and the concentration of ca 2 mg 2 sr and rb following such approach it can be assumed p 2 mg 2 hco 3 radiogenic rich 87 sr 86 sr 0 71274 rb sr 0 039 represents a dominant feature at basin scale with a weight ranging from 69 to 100 much lower percentages are related to component 2 represented by a ca 2 mg 2 so 4 2 facies with intermediate 87 sr 86 sr 0 70874 and low rb sr 2 8 10 4 ratios and component 3 identified by ca 2 hco 3 facies with less radiogenic 87 sr 86 sr 0 70827 and low mg 2 ca 2 0 011 ratios these components are mainly dominated by the dissolution of evaporitic rocks and or mixing with thermal waters in the southern part of the arno river basin and by dissolution of the carbonatic fraction kinetically favored with respect to that of the silicatic minerals in the upper reaches of the main course and its tributaries respectively

chemistry of thermal springs in the larderello travale geothermal region southern tuscany italy abstract thirty two thermal spring eleven cold spring and six steam condensates in the larderello travale geothermal region have been studied from a geochemical point of view the aim of this work was to delineate the relation between the chemical composition of the natural thermal manifestations and the thermal anomaly which is among the best known in the world the larderello spring both hot and cold are characterized by low salinity total dissolved solids generally lower than 1000 mg kg and alkaline earth bicarbonate composition in contrast an alkaline earth sulfate composition characterizes the thermal springs of the travale area this difference is due to the fact that the underground pathways of the larderello hot springs are only in shallow flyschoid caprock formations whereas at travale the paths are longer and in carbonate anhydritic mesozoic rocks which constitute the main reservoir formations in both the larderello and travale areas the thermal character of larderello springs is therefore mainly due to rock conduction whereas in travale it is mostly due to inflows of hot fluid phases from the geothermal reservoir comparison between ammonia li and b in fluid phases both steam condensates and hot springs in the larderello area suggests that in some of them their temperatures might be partly due to direct vapor inflows

borehole climate reconstructions spatial structure and hemispheric averages 1 ground surface temperature gst reconstructions determined from temperature profiles measured in terrestrial boreholes when averaged over the northern hemisphere estimate a surface warming of 1 k during the interval ad 1500 2000 other traditional proxy based estimates suggest less warming during the same interval mann et al 2003a have raised two issues with regard to borehole based reconstructions the first focuses on the need for spatial gridding and area weighting of the ensemble of borehole based gst reconstructions to yield an average hemispheric reconstruction the second asserts that application of optimal detection techniques show that the gst only weakly displays the spatial structure of the surface air temperature sat we demonstrate the consistency of gst warming estimates by showing that over a wide range of grid element area and occupancy weighting schemes the five century gst change falls in the range of 0 89 1 05 k we examine the subhemispheric spatial correlation of gst and sat trends at various spatial scales in the 5 degree grid employed for optimal detection we find that the majority of grid element means are determined from three or fewer boreholes a number that is insufficient to suppress site specific noise via ensemble averaging significant spatial correlation between sat and gst emerges in a 5 degree grid if low occupancy grid elements are excluded and also in a 30 degree grid in which grid element means are better determined through higher occupancy reconstructions assembled after excluding low occupancy grid elements show a five century gst change in the range of 1 02 1 06 k index terms 1645 global change solid earth 1699 global change general or miscellaneous 3309 meteorology and atmospheric dynamics climatology 1620 3322 meteorology and atmospheric dynamics land atmosphere interactions 3344 meteorology and atmospheric dynamics paleoclimatology keywords boreholes paleoclimate spatial analysis surface temperature

high resolution mapping of uranium and other trace elements in recrystallized aragonite calcite speleothems from caves in the pyrenees france implication for u series dating abstract aragonite and calcite speleothems were sampled in the cave of pierre saint martin pyrenees atlantiques france these speleothems contain significant amounts of uranium and strontium which were measured spatially and chemically by nuclear microprobe analysis sr and u distributions are highly varied with a marked contrast between aragonite and calcite because the aragonite concentrates sr and u on the other hand zn is preferentially located in calcite and in layers of organic matter trapped in caco 3 sr contents ranged from 440 to 1100 g g in the calcite and 4900 to 18 500 g g in the aragonite u concentrations show remarkably high values from 11 to 19 g g in the calcite and 89 to 350 g g in the aragonite these u and sr concentrations are amongst the highest measured in supergene speleothems deposited by infiltrating meteoric waters x ray absorption experiments with synchrotron radiation suggested that uranium was incorporated in its hexavalent oxidation state in both aragonite and calcite recrystallization from aragonite into calcite was indicated by micromorphological observations for some of the samples this recrystallization process may explain the uranium loss in neogenic calcite deposits and consequently the opening of the geochemical system which can lead to errors in age dating with the u series dating method uranium loss in recrystallized calcite is one of the important aspects to be considered in u series dating and more generally for u geochemical stability in caco 3

fluid geochemical transect in the northern apennines central northern italy fluid genesis and migration and tectonic implications chemical and isotopic characteristics of natural gas and thermal water discharges from the western back arc tyrrhenian sea across the apennine thrust belt to the po valley and adriatic coast foredeep basins in the northern apennines central northern italy reveal a large scale fluid motion in the upper crust both vertically and horizontally on the basis of gas compositions two different domains of rising fluids have been distinguished 1 co2 rich he poor 3he 4he high domain in the western peri tyrrhenian extensional sector 2 ch4 rich he rich 3he 4he low domain in the eastern adriatic compressional sector such gases rising from various depths are crossed by a huge lateral n2 rich water flow in the peri tyrrhenian sector of ca so4 hco3 meteoric derived waters that move in a regional wide aquifer hosted in a quite thick mesozoic carbonate series morphologically the co2 vents consist of mud basins with high gas rate emission where the rising fluids move upwards through diatremes on the other hand ch4 emissions seep out from typical mud volcanoes with a reduced gas flow rate where the fluid motion is likely related to saline diapir extrusions and the methane is mostly carried to the surface by the associated mud the two rising mechanisms described locate southwest and northeast of the apennine watershed respectively from a seismic point of view the ch4 domain in the thrust belt and foredeep areas is characterized by a large number of earthquakes indirectly pointing to a different rheological behavior of the terrains with respect to the more internal peri tyrrhenian area owing to the quite high thermal gradient of the latter the boundary of the brittle ductile crust in the peri tyrrhenian sector can be located at a 10 km shallow depth although the presence of several post orogenic basins would suggest widespread extensional tectonics in all areas west of the apennine watershed those located in the easternmost part display gas vents with typical crustal 3he 4he ratios as this ratio is very sensitive to deep fluids rising from the mantle we hypothesize that such basins at the foot of the apennines are not due to tensive stress as suggested by their morphological shape they are piggy back thrust top basins developed and evolved in a still acting compressive tectonic regime

ground temperature histories for central and eastern canada from geothermal measurements little ice age signature deep borehole temperature profiles have been analyzed to determine ground temperature histories in central and eastern canada clear signs of a cold period between 1500 and 1800 a d corresponding to the little ice age have been found a warming trend after 1800 a d was detected throughout eastern and central canada temperature profiles from western ontario are consistent and were inverted simultaneously to yield a regional ground temperature history the recent warming appears to be correlated with the increase of atmospheric co2 reported for a greenland ice core

climate from borehole data energy fluxes and temperatures since 1500 1 variations in the earth s surface energy balance are recorded in the ground as perturbations of the subsurface thermal regime here i apply singular value decomposition svd inversion methods to 826 temperature depth profiles distributed world wide in order to reconstruct ground surface temperature histories gsth and surface heat flux histories shfh from the temperature and heat flux anomalies detected in the shallow subsurface inversions yielded a mean ground surface temperature and surface heat flux histories for the earth s continents for the last 500 years results indicate that the global average ground temperature and ground heat flux have increased an average of 0 45 k and 18 0 mwm2 respectively over the last 200 years and 0 9 k in the last five centuries

hydrogeochemistry of the campania region in southern italy abstract a geochemical study of thermal springs cold springs stream waters and natural gas emissions has been carried out in the campania region of southern italy this region hosts four quaternary volcanic areas and thermal springs and gas emissions occur in three of them most thermal springs discharge na cl composition waters of connate origin derived from post orogenic volcanic and sedimentary formations although high enthalpy systems are present in two of the four volcanic areas there appear to be no magmatic contributions to the thermal springs solute geothermometers are unreliable as spring waters are strongly affected by mixing with shallow brines before discharging thermal springs and gas emissions also occur in non volcanic areas where an extensive carbonate unit acts as a regional aquifer for cold low salinity bicarbonate waters thermal features in these areas occur in fractured zones associated with active faults their compositions are determined only by the type of rock encountered by solutions before surface discharge as in other areas of north central italy the widespread occurrence of hot and cold co2 rich springs and gas emissions in both volcanic and non volcanic zones suggests a deep origin for the co2

deep soil temperature as proxy for surface air temperature in a coupled model simulation of the last thousand years 1 the relationship between terrestrial deep soil temperature tdst and surface temperature sat at interannual and centennial timescales has been investigated in a simulation of the last millennium with a three dimensional climate model driven by estimations of historical external forcing tdst is loosely related to borehole temperature profiles which have been recently used to reconstruct long term temperature trends in the last centuries recently questions about the validity of boreholes based reconstructions have been raised in the simulation at interannual time scales the connection between tdst and sat is stable being stronger in the summer half year than in the winter half year at long timescales annual tdsl is a good proxy for annual sat and their variations are almost indistinguishable from each other both tdsl and terrestrial sat overestimate the variations of global mean sat this may be a source for the disagreement between statistical reconstructions of global sat and terrestrial borehole measurements

impact of strong easterly trade winds on carbonate petroleum exploration relationships developed from caicos platform southeastern bahamas abstract brisk persistent easterly trade wind influences define holocene patterns of carbonate sedimentation across the caicos platform southeastern bahamas resultant predictive sedimentary facies models based on trade wind influences are more widely applicable to the exploration for subsurface carbonate plays than are existing models based on the northern bahamas facies patterns which are characterized by gentle trade winds and strong platform margin related oceanic processes swells and tidal currents the caicos platform relationships may be more applicable because many ancient shallow carbonate depositional environments were within the trade wind belts and commonly within broad intracratonic seas that were little influenced by oceanic processes the grainstone dominated caicos platform exhibits reservoir potential over much of its surface in contrast to northern bahamian platforms where oceanic tidal currents or swells and gentle easterly trade winds confine higher energy environments with reservoir potential to platform margins strong easterly trade winds across caicos platform promote widespread holocene platform interior oolitic skeletal and grapestone grainstone bodies on this platform orientations of ooid sand bodies vary depending on preexisting topography water depth and bottom energy shallow subtidal ooid sand shoals orient parallel to these winds ooid sands developed along older shorelines orient parallel to the shorelines but prograde perpendicular into these winds deeper platform interior oolitic sands exist as widespread sheet like deposits these trade winds allow reefs and ooids to coexist in many settings permit isolated linear reefs to flourish on certain leeward platform margins and promote effective off bank transport of carbonate sands that create onlapping grainstone wedges these relationships are very applicable to the rock record strong trade wind influences such as seen on caicos platform better explain the occurrence of cretaceous reef and or oolitic grainstone reservoirs developed well in from platform margins fairway field in east texas black lake field in louisiana than do existing northern bahamian models depositional models based on conditions in the northern bahamian models would predict low energy facies in these platform interior settings a trade wind driven depositional model characterized by strong persistent easterlies also better explains the origin of the onlapping wedge of skeletal grainstones at poza rica oilfield in mexico the caicos platform easterly trade wind driven depositional model should generally apply to any ancient shallow carbonate environment that developed 5 22 north or south of the paleoequator whether or not a platform margin was near by future carbonate exploration or exploitation should always factor in not only geological age but also physiographic latitudinal and climatic setting at a global and local scale

north american climate of the last millennium underground temperatures and model comparison general circulation models gcms are currently able to provide physically consistent simulations of millennial climate variability in which estimations of external forcing factors are incorporated as boundary conditions climate reconstruction attempts to recover as faithfully as possible past climate variability using a variety of independent and climate sensitive sources of information by deriving strategies of comparison between gcm simulations and proxy data or directly recorded data such as subsurface thermal profiles the agreement between model and observations can be assessed thermal profiles obtained from the boreholes of north america were grouped into eight geographically discrete ensembles and averaged to form robust representative profiles the gridded output from the three distinct integrations of the gcm echo g were similarly averaged by region these simulated millennial paleoclimatic histories were then forward modeled to arrive at the subsurface thermal profiles that would result from the temperature trends at the surface these forward modeled profiles were then compared with the borehole average thermal anomaly profile in each region in most of the regions studied the externally forced runs from echo g are in better agreement with underground temperature anomalies than with the control run suggesting that boreholes are sensitive to external forcing not only do echo g simulations demonstrate better agreement with borehole data when considering variable external forcing factors but echo g also appears to broadly describe qualitative aspects of long term climatic trends at a regional scale

evolution of the latera geothermal system ii metamorphic hydrothermal mineral assemblages and fluid chemistry abstract the latera field vulsini volcanic complex latium italy is one of the geothermal areas of the peri tyrrhenian belt along which a regional high thermal anomaly has been detected so far nine deep wells have been drilled within the latera caldera and four of them have been productive the geothermal reservoir is located within the fractured carbonatic rocks of the tuscan nappe the overlying volcanic units sealed by hydrothermal minerals mainly calcite and anhydrite act as an impervious cover the fluid produced by the wells comes from a deep aquifer about 1000 1500 m depth which at present is not connected with the shallow aquifer in the volcanoclastic units fluid temperatures range between 200 and 230 c in hole temperatures as high as 343 c at 2775 m depth have been measured in dry wells the study of the newly formed mineral assemblages from both volcanic and sedimentary units as sampled from the geothermal wells can be used to reconstruct the thermal evolution of the geothermal field the intrusion of a syenitic melt up to a depth of about 2000 m dated 0 86 ma represents the major thermal event for the units in the area and is assumed to represent the first step in the geothermal evolution of the latera system the above mentioned newly formed mineral assemblages can be divided into three groups a contact metasomatic calcite anhydrite diopsidic pyroxene grossularitic garnet phlogopite wollastonite or monticellite b high temperature hydrothermal calcite anhydrite k feldspar vesuvianite melanitic garnet tourmaline amphibole epidote sulphides c low temperature hydrothermal calcite anhydrite k feldspar clay minerals sulphides group a minerals are now relics part of b and all of c group are still in equilibrium with the existing conditions in different parts of the geothermal system thermodynamic calculations on the observed mineral assemblages permitted estimates of the p t conditions and gas fugacities

transient lateral heat flow due to land use changes subsurface temperatures have been shown to be useful for obtaining robust reconstructions of climatic changes for the last five centuries recently interest has focused on determining the effects of land use changes on ground surface temperatures gst which could potentially create a bias on these records and should thus be considered in the interpretation of gst reconstructions to date studies have focused on the one dimensional effect of land use changes on heat flow in this study temperature anomalies resulting from lateral heat flow were assessed for different scales of land use change numerical simulations indicate that land use changes over large areas may cause significant changes in subsurface temperatures reaching beyond the extent of the affected area at the surface we provide guidelines for future surveys and for correcting existing data d 2005 elsevier b v all rights reserved

inference of ground surface temperature history from subsurface temperature data interpreting ensembles of borehole logs ground surface temperature histories gsths inferred from borehole temperaturedepth t z data are often degraded to a various extent by random or systematic noise in thet z data and in the measurements of thermophysical properties of the earth to minimize the effects of noise and hence improve the fidelity of the inferred gsth a plausible approach is to perform a simultaneous inversion of thet z logs in a region or alternatively to invert the individualt z logs and then average the resulting gsths averaging and simultaneous inversion are conceptually different whereas an averaging can always be peformed a simultaneous inversion is predicated on the assumption of a common transient component of the gsth in all thet z logs in this work we examine and compare the two approaches using a time domain inverse formulation based on the method of least squares we consider a set of scenarios a multiplet z logs from a single borehole b multiple boreholes from a single site c multiple boreholes in similar climatological settings and d multiple boreholes in different climatological settings we show that for a b and c averaging and simultaneous inversion yield nearly identical results for boreholes in different settings the assumption of a common transient gsth may be invalid and averaging and simultaneous inversion give divergent results

chemical composition of thermal springs cold springs streams and gas vents in the mt amiata geothermal region tuscany italy abstract a geochemical study of thermal and cold springs stream waters and gas emissions has been carried out in the mt amiata geothermal region the cold springs and stream waters do not seem to have received significant contribution from hot deep fluids on the contrary the thermal springs present complex and not clearly quantifiable interactions with the hot fluids of the main geothermal reservoir the liquid dominated systems in the mt amiata area like most of the high enthalpy geothermal fields in the world are characterized by saline nacl fluids the nature of the reservoir rock carbonatic and anhydritic and its widespread occurrence in central italy favor a regional circulation of ca sulfate thermal waters which discharge from its outcrop areas waters of this kind which have been considered recharge waters of the known geothermal fields dilute disperse and react with the deep geothermal fluids in the mt amiata area preventing the use of the main chemical geothermometers for prospecting purposes the temperatures obtained from the chemical geothermometers vary widely and are generally cooler than temperatures measured in producing wells other thermal anomalies in central italy apart from those already known might be masked by the above mentioned circulation a better knowledge of deep fluid chemistry could contribute to the calibration of specific geothermometers for waters from reservoirs in carbonatic rocks

a bayesian partition modelling approach to resolve spatial variability in climate records from borehole temperature inversion summary collections of suitably chosen borehole profiles can be used to infer large scale trends in ground surface temperature gst histories for the past few hundred years these reconstructions are based on a large database of carefully selected borehole temperature measurements from around the globe since non climatic thermal influences are difficult to identify representative temperature histories are derived by averaging individual reconstructions to minimize the influence of these perturbing factors this may lead to three potentially important drawbacks the net signal of non climatic factors may not be zero meaning that the average does not reflect the best estimate of past climate the averaging over large areas restricts the useful amount of more local climate change information available and the inversion methods used to reconstruct the past temperatures at each site must be mathematically identical and are therefore not necessarily best suited to all data sets in this work we avoid these issues by using a bayesian partition model bpm which is computed using a trans dimensional form of a markov chain monte carlo algorithm this then allows the number and spatial distribution of different gst histories to be inferred from a given set of borehole data by partitioning the geographical area into discrete partitions profiles that are heavily influenced by non climatic factors will be partitioned separately conversely profiles with climatic information which is consistent with neighbouring profiles will then be inferred to lie in the same partition the geographical extent of these partitions then leads to information on the regional extent of the climatic signal in this study three case studies are described using synthetic and real data the first demonstrates that the bayesian partition model method is able to correctly partition a suite of synthetic profiles according to the inferred gst history in the second more realistic case a series of temperature profiles are calculated using surface air temperatures of a global climate model simulation in the final case 23 real boreholes from the united kingdom previously used for climatic reconstructions are examined and the results compared with a local instrumental temperature series and the previous estimate derived from the same borehole data the results indicate that the majority 17 of the 23 boreholes are unsuitable for climatic reconstruction purposes at least without including other thermal processes in the forward model

fluid geochemistry and geothermometry in the western sector of the sabatini volcanic district and the tolfa mountains central italy abstract a geochemical survey of 197 fluid discharges cold and thermal waters and bubbling pools and 15 gas emissions from the western sector of the sabatini volcanic district and the tolfa mountains latium central italy was carried out in 2007 2008 the chemical and isotopic compositions of the fluid discharges indicate the occurrence of two main sources 1 relatively shallow aquifers with ca na k hco 3 and ca mg hco 3 compositions when trapped in volcanic and sedimentary formations respectively and 2 a deep reservoir which is hosted in the mesozoic carbonate sequence rich in co 2 and having a ca so 4 hco 3 composition dissolution of a co 2 rich gas phase into the shallow aquifers produces high tds and high pco 2 cold waters while oxidation of deep derived h 2 s to so 4 2 generates low ph the 13 c co 2 values for gas emissions from 2 8 to 2 7 vs vpdb suggest that the origin of co 2 associated with the deep fluids is mainly related to thermo metamorphic reactions within the carbonate reservoir although significant mantle contribution may also occur however r r a values 0 37 0 62 indicate that he is mainly produced by a crustal source with a minor component from a crust contaminated mantle on the basis of the 13 c ch 4 and d ch 4 values from 25 7 to 19 5 vs vpdb and from 152 to 93 4 vs vsmow respectively ch 4 production is associated with thermogenic processes possibly related to abiogenic co 2 reduction within the carbonate reservoir the 34 s h 2 s values from 9 3 to 10 4 vs vcdt are consistent with the hypothesis of a sedimentary source of sulfur from thermogenic reduction of triassic sulfates geothermometric evaluations based on chemical equilibria co 2 ch 4 and separately h 2 s suggest that the reservoir equilibrium temperature is up to 300 c the d and 18 o data indicate that water recharging both the shallow and deep aquifers has a meteoric origin fluid geochemistry coupled with gravimetric data and tectonic lineaments supports the idea that significant contributions from a deep seated geothermal brine are present in the stigliano thermal fluid discharges exploration surveys investigated this area during 70 s 90 s for geothermal purposes nevertheless presently the area is still under exploited the presence of thermal waters and anomalous heat flow together with the demographic growth of the last years makes this site a suitable location for direct applications of the geothermal resource

ground temperature history in central europe from borehole temperature data summary ground temperature histories gth are inferred from temperature measurements in several boreholes of south eastern germany and western bohemia czech republic the gths that can be extracted from these boreholes ranging in depth between 150 and 700m cover the past 250yr both data sets were inverted separately and yield consistent gths they were also inverted jointly to yield a regional gth of the past 250yr for this part of europe the results indicate two main episodes in the mean ground temperature with 1 a cooling period from 1750 1800 to 1930 1950 followed by 2 short colder and warmer periods until now the same trends are found in the meteorological records at four nearby weather stations bayreuth jena munchen and praha but the meteorological record in berlin is clearly distinct the gth for this part of europe is also markedly different from one obtained in central france these differences are consistent with the spatial variability of climatic trends

geothermal resources within carbonate reservoirs in western sicily italy a review abstract low to medium temperature fluid reservoirs hosted in carbonate rocks are some of the most promising and unknown geothermal systems western sicily is considered a key exploration area this paper illustrate a multidisciplinary and integrated review of the existing geological geochemical and geophysical data mainly acquired during oil and gas explorations since the 1950s specifically re analyzed for geothermal purposes has led to understanding the western sicily geothermal system as a whole and to reconstructing the modalities and particular features of the deep fluid circulation within the regional reservoir the data review suggests the presence of wide groundwater flow systems in the reservoir beneath impervious cap rocks we identified the main recharge areas reconstructed the temperature distribution at depth recognized zones of convective geothermal flow and depicted the main geothermal fluid flow paths within the reservoir we believe that our reconstruction of geothermal fluid circulation is an example of the general behavior of low to medium enthalpy geothermal systems hosted in carbonate units on a regional scale due to the recent technological developments of binary plants these systems have become more profitable not only for geothermal direct uses but also for power production

hydrogeochemistry of the volcanic district in the tolfa and sabatini mountains in central italy abstract a geochemical study on 26 thermal springs and 5 samples from thermal wells t 20 c 19 cold springs 11 cold gas pools and 14 stream samples from the tolfa and sabatini mountains volcanic district about 1300 km2 has clarified their genesis and evolution meteoric waters infiltrate the more permeable exposed rocks carbonates and or volcanites and percolate down into two main aquifers one is deep and located in mesozoic anhydritic carbonate formations and is the regional geothermal reservoir that feeds springs that emerge at the margins of the carbonate series either exposed or barely covered its waters display typical bicarbonate sulfate alkaline earth composition the other aquifer s is shallower consisting of waters that circulate primarily in volcanic deposits the chemical characteristics of these shallow waters are heavily influenced by lithology and by a gas phase mainly co2 originating at depth temperature estimates obtained with sio2 and gas geothermometers which seem to be the most reliable under these conditions indicate the widespread occurrence of deep fluids at temperatures higher than 110 c under the area covered by the sabatini volcanites in some areas manziana trevignano nepi and cesano the subsurface waters reach temperatures within the range characteristic of medium to high enthalpy systems 120 160 c

precise chronology of the last interglacial period 234u 230th data from fossil coral reefs in the bahamas a detailed study of 238 u 234 u 230 th ages was made for different coral species from two bahamian reefs to determine the time scale of the sea level high during the last interglacial period using recently developed mass spectrometric techniques for the measurement of u and th isotopes thirty seven coral samples were analyzed in replicate typical errors at 125 ky are 1 5 ky 2 and 3 ky time intervals appear to be well resolved this high precision permits detailed chronologic study with time resolution adequate to define stages of the reef s history these data demonstrate that the time between transgression and regression of the ocean in the last interglacial was about 12 ky after which sea level fell rapidly at more than 2 m ky the high sea level stand began possibly by 132 ky and certainly by 129 ky ago when sea level reached 6 m above present mean low sea level high sea level was sustained until 120 ky and then fell rapidly this time period covers the milankovitch insolation peak at 65 n but is not sharply defined and the sea level high lasted from about 4 ky before the insolation peak to 8 ky after it we find no evidence for a double peak of sea level rise in the last interglacial episode that is high stands at both 125 and 142 ky there appears to be some discrepancy between this precise chronology for a coral reef on a tectonically stable platform and the chronology assigned to deep sea sediments the present results show that the duration of the last interglacial led to a 12 ky period of high sea level stand which is much longer than the insolation peak the study area consists of two sizeable bank barrier coral reefs of sangamon age that crop out along the coast northwest of cockburn town on san salvador island and at devil s point on great inagua island the initial stage of reef development is not revealed at either site but the main parts of both reefs are well preserved at cockburn town the beginning of the reef was marked by colonization of acropora palmata on hardground areas and possibly other corals at 132 ky ago patch reefs at the southeastern flank of the developing reef were growing by 129 to 126 ky ago by 126 to 123 ky ago the crest of the reef was formed by the frame building coral a palmata and associated patch reefs flourished along its flanks a palmata coral heads grew upward to a mean low sea level 6 m above the present one the reef began to decline as sea level dropped at about 123 to 120 ky ago near two measured profiles at devil s point the top of a rubblestone dominated by a cervicornis and patch reef corals preserved in growth position have been beveled off and represent an ancient wave cut surface 230 th ages on corals below and above this surface indicate that it was cut at about 125 1 ky ago

five millennia of paleotemperature from tree rings in the great basin usa the instrumental temperature record is of insufficient length to fully express the natural variability of past temperature high elevation tree ring widths from great basin bristlecone pine pinus longaeva are a par ticularly useful proxy to infer temperatures prior to the instrumental record in that the tree rings are annually dated and extend for millennia from ring width measurements integrated with past treeline elevation data we infer dec adal to millennial scale temperature variability over the past 4 500 years for the great basin usa we find that twentieth century treeline advances are greater than in at least 4 000 years there is also evidence for substantial volcanic forcing of climate in the preindustrial record and considerable covariation between high elevation tree ring widths and temperature estimates from an atmosphere ocean general circulation model over much of the last millennium a long term temperature decline of 1 1 c since the mid holocene underlies substantial volcanic forcing of climate in the preindustrial record

a 2000 yr reconstruction of air temperature in the great basin of the united states with specific reference to the medieval climatic anomaly abstract a sediment core representing the past two millennia was recovered from stella lake in the snake range of the central great basin in nevada the core was analyzed for sub fossil chironomids and sediment organic content a quantitative reconstruction of mean july air temperature mjat was developed using a regional training set and a chironomid based wa pls inference model r 2 jack 0 55 rmsep 0 9 c the chironomid based mjat reconstruction suggests that the interval between ad 900 and ad 1300 corresponding to the medieval climate anomaly mca was characterized by mjat elevated 1 0 c above the subsequent little ice age lia but likely not as warm as recent conditions comparison of the stella lake temperature reconstruction to previously published paleoclimate records from this region indicates that the temperature fluctuations inferred to have occurred at stella lake between ad 900 and ad 1300 correspond to regional records documenting hydroclimate variability during the mca interval the stella lake record provides evidence that elevated summer temperature contributed to the increased aridity that characterized the western united states during the mca

stable isotope and noble gas isotope compositions of inclusion fluids from larderello geothermal field italy constraints to fluid origin and mixing processes noble gas and n 2 compositions have been determined in paleofluids of core samples from geothermal wells in the larderello area italy the results were coupled with hydrogen and carbon isotope compositions of similar fluids from an independent batch of samples to provide constraints on the origin of the fluids the fluids trapped during early stage hydrothermal circulation are characterized by relatively high 4 0 ar 3 6 ar and n 2 ar ratios 332 4 0 ar 3 6 ar 564 and 248 n 2 ar 4197 respectively and indicate the presence of radiogenic 4 0 ar and excess n 2 when compared to air asw air saturated water the fluid inclusions related to late stage hydrothermal activity show low n 2 ar and 4 0 ar 3 6 ar ratios 309 4 0 ar 3 6 ar 354 and 47 n2 ar 66 respectively similar to present day geothermal fluids the 6d values of the inclusion fluids range from 53 to 85 indicating that the fluids were derived from mixing of water rich components probably from a shallow reservoir similar in composition to present day meteoric waters and fluids from a deeper reservoir the r r a ratios up to 3 2 of the paleofluids and present day fluids suggest a deep he contribution at larderello the 1 3 c values for co 2 trapped during early stage activity 3 8 o to 0 5 o were produced by carbonate country rock volatilisation 1 3 c values as low as 17 were measured in inclusion fluids related to late stage circulation and were likely produced by oxidation of organic matter at shallow depths

natural and anthropogenic changes in atmospheric co2 over the last 1000 years from air in antarctic ice and firn a record of atmospheric co2 mixing ratios from 1006 a d to 1978 a d has been produced by analysing the air enclosed in three ice cores from law dome antarctica the enclosed air has unparalleled age resolution and extends into recent decades because of the high rate of snow accumulation at the ice core sites the co2 data overlap with the record from direct atmospheric measurements for up to 20 years the effects of diffusion in the firn on the co2 mixing ratio and age of the ice core air were determined by analyzing air sampled from the surface down to the bubble close off depth the uncertainty of the ice core co2 mixing ratios is 1 2 ppm 1 preindustrial co2 mixing ratios were in the range 275 284 ppm with the lower levels during 1550 1800 a d probably as a result of colder global climate natural co2 variations of this magnitude make it inappropriate to refer to a single preindustrial co2 level major co2 growth occurred over the industrial period except during 1935 1945 a d when co2 mixing ratios stabilized or decreased slightly probably as a result of natural variations of the carbon cycle on a decadal timescale

topographic and vegetative controls on calcrete formation turks and caicos islands british west indies abstract vegetation and topography of the limestone islands on caicos platform british west indies are decisive factors in controlling the morphologic petrographic and geochemical characteristics of calcretes forming on pleistocene exposure surfaces valley calcretes form in low areas as a result of vegetative and soil forming processes which penetrate downward and reconstitute host limestone valley calcretes vary in degree of maturity which is expressed petrographically and geochemically enrichment in fe and al in valley calcretes is caused by gradual concentration of aerosol derived material in topographically low and therefore stable settings ridge caleretes form on ridge crests and slopes and are associated with downward penetrating roots but they undergo a cycle of formation and destruction ridge calcrete cycle which prevents them from achieving the progressive maturity seen in valley calcrete profiles the vegetative role in the calcrete cycle is twofold first root mats spreading out laterally within the host limestone enhance dissolution of limestone and subsequent reprecipitation of carbonate cements these processes result in well indurated calcrete layers second once formed these indurated layers are uprooted by downward and laterally displacive rooting and subjected to physical and chemical erosion recognition of the two different modes of calcrete formation in the rock record can yield valuable information about paleotopography and erosional history

twentieth century paleoclimatic modeling of borehole temperatures in western and central anatolia regions turkey understanding the change in the climate at the regional scale during the industrial period is essential for future climate projections among various proxy methods temperatures from thermally conductive boreholes offer a direct method of determination of surface temperatures changes in time in this study we use temperature depth data from six boreholes in western and central anatolia regions of turkey and present reconstructions of the surface temperatures during the last century the boreholes are located in rural areas where urban heat island effects are minimal regionally averaged gst models give cooling of 0 33 c and 0 42 c between 1900 and 1990 and warming of 1 47 c and 1 66 c between 1990 and 2010 for the western and central anatolian sites respectively the overall changes in the surface temperatures since the beginning of the twentieth century are calculated to be 1 14 c and 1 13 c in each region the instrumental sat records in these regions which are available from 1950 show a general agreement with the gst models the rate of recent warming since the early 1990 s is calculated to be 5 7 c per 100 year for both regions this value is within the range proposed by regional climate projections for the eastern mediterranean region

transient thermal effects below complex topographies abstract the topographical perturbation of steady state subsurface temperature fields has been an important issue in geothermal interpretations throughout the past century this paper reports a numerical study which considers the possible influence of terrain topography on transient temperature signals typical morphological situations over wide areas in central europe affect most likely that same depth range which also contains the temperature signals resulting from the most interesting ground surface temperature changes i e during the last 200 years the evaluation of the interaction is performed on a synthetic sinusoidal topography with varying wavelength and amplitude vertical profiles i e temperature logs were extracted from these numerical forward 2 d calculations thereby the error could be estimated by comparing ground surface temperature time histories inverted from temperature logs both with and without topographic correction the results show that a topographic correction of temperature data is absolutely necessary to achieve a consistent inversion result even rather flat topographies with 20 km wavelengths and 100 m amplitudes may introduce topographical effects which confuse the inversion process on the other hand the palaeoclimatically induced temperature signal persists even in rough topographies and will show correct inversion results when data are adequately treated only extreme situations cause a lateral interference of these transient signals with depth the results from such 2 d synthetic models have been confirmed by an analysis of a real situation the example chosen is the area surrounding the german continental deep drilling ktb project the area is situated in a moderately undulating surface topography with maximum altitude variations of the order of 250 m the additional 3 d simulation demonstrates that a strong topography dependent variation of the transient temperature signal can occur even at greater depths the introduction of corrections for topography influence reduces apparent differences in profiles from different locations in the surroundings of the ktb site to a maximum of 0 2 k

comparison of observed and general circulation model derived continental subsurface heat flux in the northern hemisphere received 8 september 2009 revised 9 february 2010 accepted 19 february 2010 published 18 june 2010 1 heat fluxes in the continental subsurface were estimated from general circulation model gcm simulations of the climate of the last millennium and compared to those obtained from subsurface geothermal data since gcms have bottom boundary conditions bbcs that are less than 10 m deep and thus may be thermodynamically restricted in the continental subsurface we used an idealized land surface model lsm with a very deep bbc to estimate the potential for realistic subsurface heat storage in the absence of bottom boundary constraints results indicate that there is good agreement between observed fluxes and gcm simulated fluxes for the 1780 1980 period when the gcm simulated temperatures are coupled to the lsm with deep bbc these results emphasize the importance of placing a deep bbc in gcm soil components for the proper simulation of the overall continental heat budget in addition the agreement between the lsm surface fluxes and the borehole temperature reconstructed fluxes lends additional support to the overall quality of the gcm echo g paleoclimatic simulations citation macdougall a h h beltrami j f gonzalez rouco m b stevens and e bourlon 2010 comparison of observed and general circulation model derived continental subsurface heat flux in the northern hemisphere j geophys res 115 d12109 doi 10 1029 2009jd013170

spatial patterns of ground heat gain in the northern hemisphere 1 variations in the earth s surface energy balance are recorded in the subsurface as perturbations of the steady state thermal field here we invert 558 temperature depth profiles in the northern hemisphere nh in order to estimate the energy balance history at the continental surface from heat flux anomalies in the subsurface the heat gain is spatially variable and does not appear to have been persistent for the last 200 years at all locations but overall continental areas have absorbed energy in the last 50 years results indicate a mean surface heat flux of 20 6 mwm 2 over the last 200 years the total heat absorbed by the ground is 4 8 1021j and 13 3 1021j for the last 50 and 200 years respectively we suggest that our results may be useful for state of the art general circulation model gcm validation and for land surface coupling schemes

geothermometry on fluids circulating in a carbonate reservoir in north central italy the peri tyrrhenian belt of north central italy is a site of large scale fluid circulation in mesozoic carbonate anhydritic formations of thermal waters with ca sulfate composition these carbonate formations are the principal geothermal reservoir of the known italian geothermal fields owing to differences in the regional structure these carbonate rocks may have an intrinsic high or low hydraulic continuity the ca sulfate springs that surface at the periphery of these formations have circulated in the unconfined parts of the carbonate aquifer the high salinity na chloride geothermal fluids discharge from the confined parts of the same reservoir rocks these fluids are somewhat separated from fluids generated in the unconfined parts by possible barriers of low permeability they are also diluted with the ca sulfate waters and have re equilibrated at lower temperature because of these conditions the assessment of the deep reservoir temperatures cannot be made using rapidly re equilibrating geothermometers such as the sio2 geothermometer the latter reveals the temperature of the unconfined aquifer at best the study of the geohydrological nature of the reservoir rocks the composition of liquid and gas phases and the statistical behavior of the main chemical geothermometers applied to the shallow cold waters of the principal italian geothermal areas has shown that the geothermometer based on nali ratio seems to be the most reliable to evaluate the deep temperatures inside the confined parts of the carbonate reservoir

penetrative calcretes and their stratigraphic implications multiple calcrete horizons previously considered representative of true subaerial exposures may in fact be false penetrative calcretes related to only one subaerial exposure event individual subaerial exposure periods can produce a true surficial calcrete plus a series of penetrative calcretes although penetrative calcrete horizons are not laterally traceable over long distances they are very similar to surficial calcretes are commonly found at sequence and or lithologic boundaries permeability anomalies and can be easily misinterpreted in core borings as representing individual exposure events recent penetrative calcretes are common on elevated limestone ridges of the caicos islands where roots penetrate downward seeking ground water moisture in glacial times penetrative calcretes may have been present throughout carbonate platforms as ground water levels were much lower penetrative and surficial calcretes can be differentiated by the lower concentrations of insoluble al and fe in penetrative calcretes

climate change on the colorado plateau of eastern utah inferred from borehole temperatures temperature profiles from boreholes on the colorado plateau of southeastern utah have been examined for evidence of climate change because these boreholes penetrate layered sedimentary rocks with different thermal conductivities bullard plots temperature versus integrated thermal resistance are used to estimate background heat flow and surface temperature intercepts reduced temperatures which represent departures from a constant heat flow condition are inverted for a surface ground temperature history at each borehole site using a singular value decomposition algorithm singular value cutoffs are selected by analyzing the spectral energy and the standard deviation of the model fit to the data as a function of the number of eigenvalues solutions are constructed from areas of large spectral energy and a cutoff where additional eigenvalues fail to improve the solution significantly the solution is parameterized in terms of 13 time steps increasing in duration and going back 400 years eight of nine borehole sites indicate between 0 4 and 0 8 c 0 2 c warming over the past 200 years with some evidence for accelerated warming in this century one borehole indicates local cooling over the same time period the amplitude of the warming inferred from borehole temperatures is less than that deduced from analysis of 100 year surface air temperature records at four of the five weather stations surrounding the borehole sites

simultaneous inversion of borehole temperature data for determination of ground surface temperature history summary recent variations of the ground surface temperature recorded in the earth s subsurface can be inverted from borehole temperature data the resolution of the inversion of borehole temperature logs is poor even when the noise level is low this report concerns the potential improvement in the resolution of ground surface temperature history when temperature logs from several boreholes are inverted simultaneously for an inversion algorithm based on singular value decomposition the singular values obtained for simultaneous inversion of several boreholes do not decrease as rapidly as the singular values for a single borehole with the same value of the cut off or of the damping parameter more eigenvectors remain in the solution and give higher resolution for several boreholes than for one tests conducted with synthetic data for 15 boreholes show that the improvement in resolution is real but not spectacular these tests indicate that borehole temperature logs should have approximately the same sampling interval temperature profiles over different depth ranges can be inverted if the reference heat flows and ground temperatures are included in the parameters determined by the inversion tests also show that no consistent ground temperature history gth is obtained when inverting data from boreholes that have experienced different surfacetemperature variations simultaneous inversion can be applied to 1 obtain a local gth for a single site with several boreholes having identical surface conditions or 2 obtain regional averages with data from different sites that have experienced the same variations in ground temperature temperature profiles measured in four boreholes near belleterre in eastern canada appear to have recorded the same perturbation inversion of the temperature data from individual boreholes yields similar but not identical gths the gth obtained by simultaneous inversion of these four boreholes indicates a cool period with minimum temperatures at ca 1800 ad followed by warming above the reference level it is consistent with other analyses indicating recent warming in eastern canada

temperature pressure and redox conditions governing the composition of the cold co2 gases discharged in north latium central italy abstract gases rich in co2 are produced over the northern latium area by metamorphic reactions involving carbonate formations or by magma degassing the gas migrates towards the surface and accumulates in sedimentary permeable structures which act as gas traps in that environment the pco2 is a variable externally fixed and the redox conditions at which the gases equilibrate are governed by the c co2 buffer temperature in the interval 100 180 c and pco2 from few bar to tens of bar have been estimated by means of the ratios between the redox sensitive gas species and co2 the composition of gases from two geothermal wells located in the study area and of other hydrothermal fluids suggest that the redox potential of low medium temperature carbonate hosted hydrothermal systems may be fixed by the c co2 buffer

theoretical geothermometers andpco2 indicators for aqueous solutions coming from hydrothermal systems of medium low temperature hosted in carbonate evaporite rocks application to the thermal springs of the etruscan swell italy in order to derivet pco2 geoindicators suitable for thermal waters coming from the hydrothermal systems of medium low temperature which are hosted in carbonate evaporite rocks the theoretical concentration of ca mg hco3 so4 f and their complexes in aqueous solutions in equilibrium with a mineral assemblage made up of calcite dolomite anhydrite and fluorite has been calculated at temperatures between 0 and 150 c atpco2 in the 0 1 100 bar interval and for total molality of mobile species na and ci ranging between 0 0001 and 0 3 the results of such calculations indicated that 1 the ca mg s04 and f contents and thes04 f 2 andcamg ratios are potential geothermometers 2 the hc03 2so4 ratio is a pco indicator 3 thehc03f ratio and the hc03 content arc indicators of bothpco2 andt a first geothermometric and geobarometric evaluation of the thermal springs of the etruscan swell generally shows equilibrium temperatures in the interval 50 100 c and pco from about 1 bar to bars these estimations are consistent with the general knowledge of the hydrothermal systems of medium low temperature present in the region

reconstruction of cave air temperature based on surface atmosphere temperature and vegetation changes implications for speleothem palaeoclimate records abstract cave temperature is a parameter of major importance for palaeoclimate studies based on speleothems since most proxies used are temperature dependent the general assumption that cave temperature reflects the mean annual surface atmosphere temperature sat over the cave is based on a limited number of specific studies and detailed mechanisms supporting this link are not properly described eagle cave in spain was used to understand the detailed mechanisms connecting sat and cave temperature a monitoring programme conducted from 2009 to 2011 allows the characterization of the thermal dynamics in the cave air in the studied karstic environment thermal conduction is the main mechanism responsible for transferring the ground temperature signal to the cave the calculated thermal diffusion coefficient is 0 756 10 6 0 013 m 2 s 1 the sat signal is recorded at the cave with a delay ranging from 3 to 11 yr depending on the thickness of the bedrock over the ceiling 5 18 m a cave cooling of 2 c has been recorded since mid 1970s when cave temperature measurements were made the application of a model exclusively based on thermal conduction of sat does not reproduce the observed thermal changes however vegetation cover over the cave was modified dramatically during recent decades this impacts ground temperature due to the changes in exposure to insolation and the modification of soil properties which is eventually recorded in the cave the incorporation of changes in vegetation cover in the model provides a realistic thermal reconstruction the impact of vegetation cover was much more significant than sat in order to explain the large thermal change in the cave over past decades thus the cooling in eagle cave during past decades is mainly controlled by a variable decoupling from mean annual sat as a result of the afforestation over the cave the effect of this thermal decoupling on speleothem 18 o records is potentially significant and should be considered when performing accurate palaeoclimate reconstructions

isotopic and chemical assessment of geothermal potential of the colli albani area latium region italy abstract the chemical and isotopic compositions of low temperature mineral waters discharged over the colli albani region south of rome italy are those of highly immature waters of essentially meteoric origin formed through absorption of gases emanating from greater depth followed by cation leaching of country rock at shallow levels the composition of the gases discharged points to the presence at depth of a co2 producing high temperature system in its waning stage low h2 and unsaturated hydrocarbon contents as well as relative he ar and n2 contents indicate long residence time for the rising gas phase of the order of 1 ma on the basis of these findings temperatures higher than 120 c appear unlikely to exist at shallow depth

uranium series dating of quaternary deposits abstract this is a review of u series dating methods as applicable to terrestrial sedimentary materials alpha counting techniques allow the dating of carbonates and phosphates with a precision of 5 to 10 over the time range from 1 ka to 350 ka atom counting methods mass spectrometry and ams substantially increase precision and may increase the range problems of contamination and open system behavior are discussed correction for detrital contaminant is demonstrated in the dating of speleothem from a cave in italy

comments on anatomy of a late quaternary carbonate island constraints on timing and magnitude of sea level fluctuations west caicos turks and caicos islands bwi by kerans et al quat sci rev 205 2019 193 223 abstract we comment on interpretations of the evolution of late pleistocene geology on west caicos island caicos platform b w i by kerans et al 2019 which omits our documentation of the interrelationship of carbonate facies in outcrop and in boreholes dravis and wanless 2017 we further disagree with their geochronological dating assumptions results that are the basis for interpreting late quaternary sea level fluctuations

tracing deep fluid source contribution to groundwater in an active seismic area central italy a combined geothermometric and isotopic δ13c perspective abstract an understanding of the origin and migration pathways of geofluids in an active seismic area is of paramount importance in terms of societal challenges such as mitigation of seismic hazards this study investigates the relationship between the stable isotope ratio 13c 12c of deep co2 and geothermometry in selected groundwater samples located close to extensional faults in central italy the temperature range is inferred from an equation based on the na li ratio and chemical geothermal modelling 113 130 c globally the calculated temperature range agrees with that resulting from deep boreholes in the northern apennines an alternative method is also included to better evaluate the difference in isotopic composition between the aqueous and gaseous 13c co2 at deep condition a review of previously published data shows that monitoring of the isotopic composition of the dissolved inorganic carbon dic in springs fed by meteoric origin located in seismically active areas must take into account mass and isotopic balance to correctly evaluate the component and the role of deep fluid during seismic events in particular the coupled and corrected isotope and geothermometrical monitoring of the springs could help to distinguish between deep gas or deep fluid contributions to shallow aquifers the results of this study indicate that faults play a crucial role in controlling the migration of crustal fluids in addition they reveal that possible evaluation of potential seismic precursors mandatorily requires a long period of monthly monitoring

diagenetic effects on uranium isotope fractionation in carbonate sediments from the bahamas abstract uranium isotope variations 238u recorded in sedimentary carbonate rocks are a promising new proxy for the extent of oceanic anoxia through geological time however the effects of diagenetic alteration on the u isotopic composition in carbonate sediments which are crucial to understand the accurate reconstruction of marine 238u are currently poorly constrained here we examine the effects of the aragonite to calcite transition in the pleistocene key largo limestone of south florida and assess the effects of vadose meteoric phreatic meteoric and phreatic marine diagenesis on u isotope fractionation in carbonate sediments from the bahamas transect including the well studied clino unda and odp site 1006 drill cores our results suggest that early diagenetic processes in bahamas carbonate sediments fractionate u isotopes by an average of 0 27 0 14 1 sd heavier than contemporaneous seawater downcore variations of 238u in slope and basin sediments display little if any correlation with u concentration and common geochemical indicators of diagenesis 13c 18o mn sr mg ca sr ca enrichments of redox sensitive elements or rare earth elements anomalies we propose two possible mechanisms to interpret the positive change in the 238u during carbonate diagenesis authigenic enrichment of isotopically positive u iv in carbonates and preferential incorporation of isotopically positive aqueous u vi species into carbonates these processes likely operate during early syndepositional diagenesis on the banktop further diagenesis during deeper burial is limited by the low solubility of u iv under reducing pore water conditions the early diagenetic behavior of u isotopes in bahamas carbonate sediments is likely broadly representative of carbonate diagenesis in the geological past we suggest that the mean diagenetic offset determined in this study be applied when reconstructing seawater 238u from ancient carbonates furthermore early diagenesis induces significant statistical variability in sediment 238u values pointing to the need for large high resolution data sets in order to average out stochastic variations in individual bulk sediment samples

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

repeat temperature measurements in boreholes from northwestern utah link ground and air temperature changes at the decadal time scale 1 borehole temperature profiles provide a record of ground surface temperature gst change at the decadal to centennial time scale gst histories reconstructed from boreholes are particularly useful in climate reconstruction if changes in gst and surface air temperature sat are effectively coupled at decadal and longer time periods and it can be shown that borehole temperatures respond faithfully to surface temperature changes we test these assumptions using three boreholes in northwestern utah that have been repeatedly logged for temperature over a time span of 29 years we report 13 temperature depth logs at the emigrant pass observatory borehole gc 1 eight at borehole si 1 and five at borehole dm 1 acquired between 1978 and 2007 systematic subsurface temperature changes of up to 0 6 c are observed over this time span in the upper sections of the boreholes below approximately 100 m any temperature transients are within observational noise we difference the temperature logs to highlight subsurface transients and to remove any ambiguity resulting from steady state source of curvature synthetic temperature profiles computed from sat data at nearby meteorological stations reproduce both the amplitude and pattern of the transient temperature observations fitting the observations to within 0 03 c or better this observational confirmation of the strong coupling between surface temperature change and borehole temperature transients lends further support to the use of borehole temperatures to complement sat and multiproxy reconstructions of climate change

thermal springs in italy their relation to recent tectonics the large scale circulation of thermal waters in italy is reviewed from both a chemical and an isotopic point of view two main areas are recognized one in the alpine region and the other in the central southern apennine region the alps are an area of very high hydraulic heads and low thermal gradients where hot deep seated waters of meteoric origin rapidly reach the surface along active boundary fault systems the apennines in contrast are characterized by lower hydraulic heads and higher thermal gradients all thermal springs in italy including those in active volcanic areas originate essentially from meteoric waters and most follow long pathways in mesozoic carbonate anhydritic aquifers before emerging as indicated by relations among present hydrothermal activity in central southern italy deep crustal structures and pco2 content in thermal waters

karst springs as natural pluviometers constraints on the isotopic composition of rainfall in the apennines of central italy abstract this paper describes an indirect method to calculate the isotopic composition of rainfall by using the isotopic composition of karst springs fed by waters circulating in the most important regional aquifer of central italy i e the mesozoic limestone sequence that forms the backbone of the apennines by using 18o and d data and the 18o and or d average gradient for elevation evaluated through the use of literature rainfall data and new measurements from a typical alpine valley in northern italy the altitude of precipitation of their parent water has been re calculated vertical descents of more than 2000 m from recharge to discharge have been assessed in some high flow rate cold springs in the morphologically steep adriatic sector of central italy a clear correlation between the vertical descents and more negative isotopic compositions at their relative emergence elevations is highlighted in contrast in the tyrrhenian sector lower karstic drops generally lower than 500 m correlate with less negative isotopic composition of recharge areas the 18o iso contour map of the recalculated parent rainfall in central italy is more detailed than any possible isotopic map of rainfall made using pluviometers unless large number of rainfall collectors were deployed on mountaintops the data also show that the isotopic composition of rainfall depends on the source of the storm water in particular precipitation is isotopically heavier when originating in the mediterranean sea and lighter when formed in the atlantic ocean consequently the collision between air masses with such a different isotopic signature results in a relatively small latitudinal fractionation effect the peninsular part of central italy is very narrow with several mountains and massifs more that 2000 m high and any latitudinal variation in the isotopic composition between rainfall sourced in the atlantic ocean and in the mediterranean sea is much lower than that due to the isotopic fractionation due to elevation

u sr and mg in holocene and pleistocene corals a palmata and m annularis abstract mg sr and u concentrations are reported for living holocene dead and pleistocene montastrea annularis and acropora palmata in an effort to characterize starting materials and identify diagenetic effects in unrecrystallized skeletal aragonite the data indicate that skeletogenesis of minor elements is a taxa specific process yielding different mg sr and u values for each species during diagenesis sr concentrations increase and mg concentrations decrease in both species u diagenesis appears to be affected by skeletal structure establishment of u concentration ranges for modern corals provides a criterion for selecting samples for dating concentration changes in mg and sr during diagenesis limit their usefulness as paleo environmental indicators

simulating heat transport of harmonic temperature signals in the earth s shallow subsurface lower boundary sensitivities across the bottom boundary at depths that usually range between 2 and 10 m boundary conditions at these depths however change the behavior of propagating temperature signals in a way that is not representative of the actual behavior in the earth s subsurface here we explore how the choice and depth of a lower boundary condition influences the subsequent evolution of subsurface temperatures given a simple harmonic surface temperature function 3 two studies that have investigated how the depth of the lower boundary condition affects subsurface temperature evolution are lynch stieglitz 1994 and sun and zhang 2004 lynch stieglitz 1994 investigated the behavior of annual signals in a land surface model with a zero flux lower boundary condition imposed at 2 3 m and noted that the annual signal was attenuated less and phase shifted more with depth than what was expected that is the model formulation yielded subsurface temperatures that were warmer in summer and colder in winter with maximums occurring later in the year than what was expected in realworld conditions sun and zhang 2004 provided an additional investigation of the finite boundary effect again focusing on the annual signal they demonstrated behavior similar to that noted by lynch stieglitz 1994 and concluded that land surface models should place lower boundaries between 6 and 15 m depending on the thermophysical properties of the modeled subsurface 4 both of the above mentioned studies used numerical land surface models to elucidate the impact of the lowerboundary condition on simulations of subsurface heat transport and focused only on the annual signal we take an alternative approach to this problem and employ analytic solutions of the one dimensional thermal diffusion equation this approach allows a more general and transparent understanding of how the depth of the lower boundary condition impacts simulations of heat transport across a wide range of frequencies

geochemical characteristics of greek thermal springs abstract a systematic sampling of all known thermal springs and gas emissions of continental greece has been carried out the main gas and water composition and some trace elements in liquid phase sio 2 h 3 bo 3 nh 4 and li have been determined the chemical composition of most thermal springs analyzed is typical of deep na hco 3 rising hot waters which circulate in co 2 rich silicic formations and which acquire progressively a na cl composition by admixing of colder shallower saline connate waters housed in the rock matrix of marine post orogenic tertiary quaternary sediments on the whole the thermal manifestations of continental greece can be fitted in a tectonic framework where high hydraulic gradients enable waters in hot deep aquifers to reach the surface rapidly along fault systems at the boundary of n s and e w trending tertiary basins equilibration temperatures of 80 120 c in the main storage zone 130 150 c max in the nestos xanthi basin have been assessed for most of the study area high n 2 and low h 2 and h 2 s content in gas emissions associated to water samples are consistent with temperatures assessed by using geothermometers in liquid phase

ground warming patterns in the northern hemisphere during the last five centuries abstract changes in the earth s surface energy balance recorded underground were used to reconstruct the temperature of the ground surface for the last 500 years in the northern hemisphere we reconstructed ground surface temperature histories gsths from temperature versus depth profiles measured at 558 sites distributed between 30 and 60 n in the northern hemisphere we show that the ground has warmed about 0 5 k in the last 100 years spatial analysis reveals that spatial variability is important and that the weighted average northern hemisphere gsth shows some consistency with multiproxy and meteorological records reconstructions for the last two centuries

a combined geochemical and isotopic study of the fluids discharged from the montecatini thermal system nw tuscany italy abstract the thermo mineral fluids discharges of montecatini terme northern apennines tuscany italy have been exploited since the roman times and despite the fact that this thermal complex is one of the biggest in europe the most recent geochemical investigations were published almost 40 years ago to fill this gap in this paper a detailed geochemical and isotopic investigation on the main thermal springs and wells from the montecatini thermal system mts is presented the chemical and isotopic features of the montecatini waters suggested that they are mainly controlled by water rock interaction processes between meteoric water permeating at depth from the surrounding reliefs up to 800 m a s l and the triassic evaporites burano formation belonging to the tuscan sedimentary series the local stratigraphic and tectonic framework favors an efficient recharge of the hydrothermal reservoir by the meteoric precipitation from a large catchment area and this aspect plays a fundamental role for the longevity of the montecatini thermal spas notwithstanding the huge amount of thermal water exploited the 3h values indicated that the thermal waters are likely related to a relatively long 50 years fluid circulation pattern approaching the surface thermal and saline waters mix with cold and low tds total dissolved solids waters hosted in short shallow aquifer s whose chemistry is dictated by the interaction of rain waters with silico clastic rocks of low solubility geothermometric estimations in the f so42 hco3 system suggested the occurrence of a main fluid reservoir at t 80 95 c and pco2 0 5 bars such co2 pressure is consistent with values estimated for other thermal springs from central southern tuscany being co2 basically supplied by a deep source nevertheless 13c co2 and 13c tdic values were lower than those expected for a mantle thermometamorphic co2 source this can be explained by i isotopic fractionation occurring during calcite precipitation and or ii mixing with biogenically derived gases occurring at relatively shallow depth

the chemistry and isotopic composition of waters in the low enthalpy geothermal system of cimino vico volcanic district italy abstract geothermal energy exploration is based in part on interpretation of the chemistry temperature and discharge rate of thermal springs here we present the major element chemistry and the d 18o 87sr 86sr and 11b isotopic ratio of groundwater from the low enthalpy geothermal system near the city of viterbo in the cimino vico volcanic district of west central italy the geothermal system hosts many thermal springs and gas vents but the resource is still unexploited water chemistry is controlled by mixing between low salinity hco3 rich fresh waters

ground temperature histories in eastern and central canada from geothermal measurements evidence of climatic change abstract inverse and direct methods have been used to analyze a large number of borehole temperature logs in order to infer past climatic changes results indicate a warming of 1 2 c in eastern and central canada during the past 150 years a period of cooling between 500 and 200 years before present corresponding to the time of the little ice age has also been identified in the same areas a regional ground temperature history is estimated for eastern and central canada from the simultaneous inversion of several temperature logs the inferred temperature changes appear correlated with the concentration of atmospheric carbon dioxide as reported from a greenland ice core and agree with existing meteorological and dendrochronological records for the area