recently growing subaqueous flowstones occurrence petrography and growth conditions abstract subaqueous flowstones have been studied in two resurgence caves in slovak karst southern slovakia namely krasnohorska and drienovska caves the flowstones litter streambeds within the distance of several hundred meters upstream from resurgences they form laminated crusts within channels of the underground streams flowing through the caves layers composed of columnar sparry calcite alternate with those composed of microcrystalline calcite the latter are enriched in fine detrital non carbonate components which resulted in crystallization of microcrystalline calcite instead of sparry calcite the growth rate of the studied flowstones reaches 0 96 mg cm 2 day which corresponds to ca 0 3 mm per year seasonal observations conducted between november 2010 and september 2012 reveal that deposition of subaqueous flowstones in the studied caves significantly depends on the local hydrological conditions during the periods of low flow si calc values of underground stream increase and columnar sparry calcite grows conversely during peak flow periods si calc values decrease and subaqueous flowstones are subjected to destruction both by mechanical erosion and corrosion the decreasing discharge just after peak flows causes deposition of fine grained particles which results in precipitation of microcrystalline layers subaqueous flowstones grow in complete darkness and in atmosphere with elevated co 2 content similarly to typical speleothems but they are fed with turbulent stream water similarly to calcareous tufas their growth rate is higher than those of normal flowstones fed with a film of water seeping down it falls within a range of growth rate of calcareous tufas though near the lower limit of this range therefore subaqueous flowstones represent an intermediate link between other speleothems and tufas deposited outside the cave environment

effects of grand cycle cessation on the diagenesis of upper cambrian carbonate deposits in the southern appalachians u s a abstract the vertical transition from the mainly subtidal alternating shale and carbonate units or grand cycles of the conasauga group middle to upper cambrian to the peritidal dolostone of the knox group upper cambrian to lower ordovician marks a major change in the early paleozoic passive margin sedimentation of the southern appalachians the grand cycles represent an interplay between intrashelf shale basin and carbonate platform deposition the end of grand cycle deposition occurred in response to carbonate platform progradation over the infilled intrashelf basin and is associated with a prominent change in diagenetic patterns observed in the uppermost conasauga group strata the maynardville formation the maynardville records upward shallowing from subtidal shale and limestone into peritidal dolostone this change from a subtidal into a peritidal depositional regime influenced the early diagenesis of the maynardville and in conjunction with the changes in the regional facies distribution at the end of grand cycle deposition extended its influence upon the burial diagenesis of these deposits the subtidal deposits of the maynardville contain a variety of calcite cements dolomite is not abundant in these deposits where it occurs mainly as a fine crystalline ferroan phase associated with argillaceous layers and pressure dissolution features the local source for this dolomite during burial was provided by expulsion of pore fluids from interbedded shale deposits diagenesis of clay minerals and pressure dissolution of carbonates ferruginous coatings on hardgrounds in the subtidal deposits provided an additional local source of iron for the formation of replacement saddle dolomite the subtidal deposits also contain saddle dolomite cement associated with mississippi valley type mvt minerals which indicate the involvement of externally derived fluids during late burial diagenesis of these strata the peritidal deposits on the other hand are extensively dolomitized fine crystalline dolomite most likely represents early diagenetic replacement of tidal flat carbonate sediment coarse crystalline replacement dolomite formed during burial by recrystallization of early dolomite and dolomitization by warm burial brines fenestrae desiccation cracks and evaporite dissolution voids are occluded with dolomite cement which is commonly complexly zoned zoned dolomite precipitated during shallow to intermediate burial and is postdated by saddle dolomite cement saddle dolomite in pore centers dissolutional voids and tectonic fractures formed during late burial from warm fluids associated with the migration of mvt brines the effects of changes in the depositional setting on diagenesis are reflected in similar early diagenesis between the subtidal maynardville and the underlying conasauga group carbonate deposits and between the peritidal deposits of the upper maynardville and the rest of the overlying knox group the depositional environments and early diagenesis also affected the burial diagenesis the changes in regional facies distribution caused by carbonate platform progradation at the end of grand cycle deposition resulted in a decrease in the proportion of siliciclastic components this decrease was accompanied by a decline in the amount of ferroan carbonate in the peritidal deposits the maynardville is conformably overlain by carbonate deposits of the knox group this allowed the maynardville knox succession to behave as a single hydrologic unit for the migration of burial fluids in response to the formation of the ordovician foreland sevier basin to the southeast during the conversion from a passive into a convergent continental margin the nolichucky shale separates the maynardville knox succession from the carbonate deposits of the underlying conasauga group which were in contrast affected by the migration of burial fluids from the cambrian intrashelf shale basin to the west

speleothem architectural analysis integrated approach for stalagmite based paleoclimate research this work was supported by the r d i program of spain cgl2013 43257 r and the universidad complutense de madrid research group 910198

multi proxy speleothem record of climate instability during the early last interglacial in southern turkey abstract a stalagmite from dim cave in southern turkey contains a climate record documenting rapid and significant changes in amounts of precipitation between 132 ka and 128 ka during the penultimate glacial interglacial transition some u th dates have been compromised by carbonate dissolution but rigorous selection and tuning to 18o records from other speleothems has generated a robust age model growth rate was initially very slow but a rapid increase at 129 ka was accompanied by strong negative trends in 18o and 13c a combination implying the onset of much wetter conditions isotopic values at 129 ka suggest that groundwater recharge rates and biogenic activity in the soil zone exceeded those of the early holocene a significant isotopic enrichment event at 128 ka during which there was alternating aragonite and calcite deposition documents a strong drying event with a duration of 200 years a concurrent decrease in 87sr 86sr ratios indicates increased groundwater residence times and the cumulative evidence suggests amounts of rainfall fell from well above to slightly below present day levels similar 18o enrichment events are present in coeval speleothem records from southwest france and the northern alps and these together with pollen evidence from italy greece and the iberian margin of drier conditions at this time imply that a climate anomaly extended across the northern mediterranean borderlands the timing duration and structure of this episode are consistent with marine evidence of strong north atlantic cooling early in the last interglacial and there is a resemblance to the holocene 8 2 ka event recorded globally in many proxy climate archives

magnetic fabrics and fluid flow directions in hydrothermal systems a case study in the chaillac ba f fe deposits france this study presents a possible use of anisotropy of magnetic susceptibility ams to describe the mineralizing process in hydrothermal systems ba f fe rich deposits within the chaillac basin are on the southern border of the paris basin in these deposits hydrothermal textures and tectonic structures have been described in veins sinters and sandstone cemented by hydrothermal goethite 278 oriented cores from 24 sites have been collected in these formations in addition a lateritic duricrust superimposed on the hydrothermal formation has been sampled rock magnetic investigations show that the principal magnetic carrier is goethite for the hydrothermal mineralization and for the laterite level the ams measurements show distinguishable behaviors in the different mineralogical and geological contexts the k1 magnetic lineation maximum axis is strongly inclined for the vertical veins for the horizontally mineralized sinters the magnetic lineation is almost horizontal with an azimuth similar to the sedimentary flow direction the ams of goethite rich sandstone close to the veins shows strongly inclined k1 as they are probably influenced by the vertical veins however when the distance from the vein is larger than 1 m the ams presents rather horizontal k1 directions parallel to the sedimentary flow the laterite has a foliation dominance of ams with vertically well grouped k3 axes and scattered k1 and k2 axes field structural observations suggest that the ore deposit is mainly controlled by ew extension tectonics associated with ns trending normal faults combining the ams results on the deposit with vein textures and field data a model is proposed in which ams results are interpreted in terms of hydrothermal fluid flow this work opens a new investigation field to constrain hydrodynamic models using the ams method textural study combined with efficient ams fabric measurements should be used for systematic investigation to trace flow direction in fissures and in sand porosity

diagenetic salinity cycles and sea level along a major unconformity monte composauro italy abstract in shallow water carbonates position of the water table and the chemistry of early diagenetic fluids are controlled in large part by sea level and climate fluctuations these fluctuations may result in cyclic progression from marine diagenesis or sedimentation to mixing zone meteoric mixing zone and then marine diagenesis or sedimentation herein we term such a cyclic progression as a diagenetic salinity cycle this diagenetic study along a single unconformity in cretaceous limestones of monte camposauro southern apennines italy demonstrates the presence of four diagenetic salinity cycles and their link to relative changes in sea level data consist of field observations transmitted light and cathodoluminescence microscopy fluid inclusions and carbon and oxygen isotopes they show that twenty one unconformity related diagenetic features predated deposition of marine limestones above the unconformity fossiliferous internal sediments and stable isotope data from radiaxial fibrous calcite and recrystallized aragonite are used to indicate marine diagenesis fluid inclusion and stable isotope data are used to indicate precipitation of calcite cement in all mixing ratios of the mixing zone environment and in the freshwater phreatic zone paleocave morphology indicates vadose and water table dissolution and bauxite sediments support extensive vadose diagenesis in each diagenetic salinity cycle there is evidence for relative fall or rise of sea level indicated by transitions from marine sedimentation to mixing zone and freshwater phreatic diagenesis marine phreatic to freshwater vadose diagenesis vadose diagenesis to marine phreatic diagenesis and freshwater phreatic diagenesis to normal marine sedimentation during the time interval of the development of the unconformity beginning some time in the aptian and ending in the early middle cenomanian at least seven third order eustatic fluctuations have been hypothesized during an overall second order eustatic rise at a given elevation the third order eustatic fluctuations would not be able to produce four diagenetic salinity cycles without tectonic uplift of 3 5 to 8 mm ky our study illustrates that the formation and the timing of diagenetic salinity cycles are highly sensitive to paleoelevation diagenetic salinity cycles preserved along unconformities can be used to interpret relative changes of sea level and to predict the presence of depositional sequences in downdip positions conversely downdip depositional sequences tectonic history and sea level history can be used to predict some aspects of diagenetic alteration updip

formation of calcite in the presence of dissolved organic matter partitioning fabrics and fluorescence abstract dissolved organic matter dom is omnipresent in natural waters and is commonly incorporated into carbonates records of dom from speleothems secondary carbonates found in caves have often been interpreted to reflect groundwater dom concentrations however the fidelity of these records is largely untested an understanding of the relationship between dripwater and speleothem dom is thus required to allow speleothems to be reliably used as archives of dom concentration we precipitated calcite caco3 crystals from weak solutions of nh4 2co3 cacl2 and nh4cl these solutions also contained peat dom from 0 to 15 mgc l fluorescence 3d excitation emission matrix 3d eem analysis showed a strong positive correlation between dom in the parent solution and dom in the calcite calcite precipitation was reduced at high dom concentrations potentially indicating inhibition of crystallisation partition coefficient values showed that domaq was subtly preferentially incorporated into calcite scanning electron microscope images indicated that the crystal structures were heavily influenced by dom adsorption with finer smooth faced rhombohedral crystals forming in growth solutions with low aqueous dom 0 5 mgc l and prismatic impure crystals produced at high aqueous dom 10 and 15 mgc l overall our results indicate that authigenic carbonates are likely to faithfully record variations in aqueous dom within the natural range of dom concentrations in representative freshwater systems caves soil water and that crystal habits are altered by aqueous dom within their growth solutions we also applied our findings to three flowstones collected from three new zealand caves which vary in climatic vegetation and hydrological regimes we conclude that differences in initial aqueous dom do indeed control incorporation of dom into calcite and thus 3d eem fluorescence can be used to reconstruct original aqueous dom from authigenic carbonates

marine carbonate cements biofilms biomineralization and skeletogeneis some bivalves do it all recent years have seen a growing interest in the direct and indirect roles of organisms and more explicitly of organic matter in the crystallization of minerals in sediments two bivalve genera form extensive biofilms that are apparently responsible for the growth of a variety of isolated crystals together with a marine cement granicorium indutum and samarangia quadrangularis are infaunal species that cover their shells with a cemented coating of sand sculpted to mimic the surface ornament typical of many bivalves granicorium has an exceptionally mobile mantle margin that produces large volumes of mucus harboring a diverse microbial community the sand grains surrounding both species are initially bound by a biofilm that provides structural integrity but also acts like others as a template for the crystallization of a variety of carbonate polymorphs these include varied prismatic crystals rice grain and wheatsheaf forms and more importantly large volumes of acicular crystals indistinguishable from typical marine cements the distribution of these crystals is related to positions accessible to the mantle of the animal and in samarangia appears to result from the active emplacement of grains and mucus several times a year summing the evidence it seems that these species are responsible not only for the biomineralization involved in the formation of their shells but also for crystallization mediated through biofilms and for the generation of cements that are morphologically indistinguishable from typical marine cements the boundaries between these three strategies may be closer than we think

holocene and eemian climatic optima in the korean peninsula based on textural and carbon isotopic records from the stalagmite of the daeya cave south korea abstract textural and stable isotopic records from the absolute dated stalagmite of the daeya cave dy 1 provide new insights into the climatic evolution of the korean peninsula during the holocene and eemian climatic optima the stalagmite yielded ages of 8572 227 to 5907 158 and 1 23 456 535 to 1 19 837 1089 years which coincide with the holocene and eemian climatic optima respectively the stalagmite s 13 c record closely resembles previously reported chinese speleothem 18 o data thus it can be suggested that textural and geochemical results of the dy 1 reflect east asian monsoon intensity which is forced by summer insolation patterns in the northern hemisphere lighter carbon isotopic compositions well developed fibrous calcite crystals and their relatively faster growth rate in the stalagmite sample are interpreted to reflect the warmest and wettest climate conditions of the holocene and eemian interglacials both climatic optima took place when insolation was decreasing from its maximum level temperature in greenland was highest and sea level approached its maximum level these climatic optima also coincide with decreasing antarctic temperatures compared the dy 1 data to other proxies it is suggested that the holocene and eemian climatic optima developed through a balance among boreal insolation monsoon intensity and sea level also continental ice volume which are the main climatic forcing factors in the northern hemisphere these trends also follow the bi polar seesaw mechanism as previously described

physicochemical characteristics of drip waters influence on mineralogy and crystal morphology of recent cave carbonate precipitates speleothems are one of the most intensively explored continental archives for palaeoclimate variability the parameters however that control speleothem petrography and its changes with time and space specifically calcite crystal morphology and carbonate mineralogy are still poorly understood in order to shed light on processes and their products precipitation experiments of recent carbonate crystals on watch glasses and glass plates were performed in seven selected caves drip water sites were analysed for their fluid mg ca molar ratio ph degree of saturation for calcite and aragonite and drip rates corresponding precipitates were analysed with respect to their mineralogy calcite crystal morphology and mg ca molar ratio of calcite the following results are found high fluid mg ca ratios are found only for caves situated in dolostone thus the hostrock lithology indirectly controls the carbonate mineralogy and calcite crystal morphology of speleothems the precipitation of aragonite in place of calcite occurred only in dolostone caves and is bound to very specific conditions these are high fluid mg ca ratios 0 5 high fluid ph 8 2 and low fluid saturation indices for calcite 0 8 these specific conditions are induced by slow drip rates of 0 2 ml min as often under more arid conditions causing the precipitation of calcite aragonite prior to reaching the stalagmite top due to this fluid chemistry is altered which in turn leads to changes in carbonate mineralogy and geochemistry on the stalagmite top calcite growth is inhibited at high fluid mg ca ratios and hence aragonite precipitation is kinetically stabilised an increase of the drip water mg ca ratio leads to an increased incorporation of mg2 into the calcite crystal lattice and thus to a change in calcite crystal morphology four distinctive changes occur with increasing mg2 incorporation i development of new forms steeper rhombohedra and base pinacoid at the edges and corners of the crystal seed ii crystal habit tend to elongate along 0 0 1 due to slower growth of faces with high mg2 densities iii reconstitution of crystal faces with low mg2 densities and iv occurrence of calcite crystals with bended faces and edges due to very high mg2 mg ca ratios of 0 009 0 051 incorporation growth rates and possibly also organic compounds however may also affect the morphology of calcite crystals based on the data shown here the relation of mg2 incorporation and the resulting changes in calcite crystal morphologies as well as the conditions of aragonite precipitation are now clearly better understood further work should aim at linking the calcite crystal morphology of watch glass precipitates with calcite crystal fabrics in speleothems in order to exploit the petrographic archive of speleothem deposits

diagenesis and sea level change lessons from moruroa french polynesia an inclined borehole through the margin of moruroa atoll french polynesia in which the ages of units are constrained by radiometric dates provides a unique opportunity to examine the relationship between sea level change and diagenetic history the oldest rocks encountered are dated at 355 840 yr bp and the overlying succession records five cycles of deposition and emergence culminating in the deposition of the holocene sequence successive intervals of emergence provided the driving force for diagenetic change promoting the through flow of chemically aggressive fresh waters that were at times either pervasive or confined within relatively isolated pathways on a millimetre to metre scale these locally varying flows and flow rates defined restricted zones characterized by differences in water chemistry and diagenetic signatures in contrast to some sequences elsewhere the upper part of the moruroa atoll succession is typified by alternations of intervals in which either several generations of cement growth are represented or only one or two cements are present three distinct diagenetic signatures can be recognized as follows i fresh water phreatic zones are reflected in neomorphism and the deposition of cements that occluded porosity thus preventing the deposition of later cements and conferring relative stability ii vadose zones are characterized by more complex diagenetic sequences reflecting multiple phases of dissolution and cement growth attesting to the relative duration of exposure and the conditions of ground water flow and iii deep in the core sequences reflect lowstand deposits that suffered sub sea diagenesis generating pores in which multi layered marine cements apparently formed at more frequent intervals than those subject to subaerial processes all cements appear to be of narrowly constrained ages these results highlight the contentious issue of whether the distributions of former diagenetic environments can be related to specific sea level stands and erosion surfaces it seems that in the moruroa core some cycles of sea level change are reflected in distinctive packages of diagenetic features that have not been overprinted by cement growths during later sea level stands

calcite and aragonite precipitation under controlled instantaneous supersaturation elucidating the role of caco3 saturation state and mg ca ratio on calcium carbonate polymorphism abstract for many decades researchers have attempted to clarify the factors controlling the precipitation of calcium carbonate polymorphs and the incorporation of mg into calcite precipitating in natural systems in this study a novel experimental approach delineates the role of instantaneous supersaturation and solution mg ca ratio in calcium carbonate mineralogy and composition the results of this study show that in solutions with different mg ca ratios the transition between the aragonite and the calcite aragonite precipitation fields is controlled by a combination of the saturation state of the solution with respect to caco3 and the mg ca ratio in solution the data show that for increasing solution mg ca ratios progressively higher supersaturation level is required for calcite precipitation the predominance of aragonite at high solution mg ca and low supersaturations is attributed to a relative decrease in calcite growth rates as a result of increasing incorporation of mg2 in the calcite lattice at higher solution mg ca ratios as suggested by abundant experimental work increasing solution mg ca decreases the growth rate of calcite while aragonite growth rates stay unaffected our experiments do demonstrate that despite decreased growth rate the percentage of mgco3 in calcite increases with increasing solution mg ca ratio as calcite growth rates decrease aragonite growth rates stay constant and it becomes the dominant mineral phase in solutions with high mg ca ratio and low supersaturations these findings are relevant to present day mineralogical distributions in carbonate systems and might be the key to elucidate the environmental conditions responsible for mineralogic changes through geologic time the observed dependence of calcium carbonate mineralogy on solution composition and supersaturation suggests that carbonate mineralogy is controlled by kinetics of growth

origin of platy calcite crystals in hot spring deposits in the kenya rift valley abstract platy calcite crystals which have their c axis parallel to their shortest length axis are common components of travertine deposits found around some hot springs in the kenya rift valley they are composite crystals formed of numerous paper thin subcrystals individual plates allowed to grow without obstruction develop a hexagonal motif the kenyan crystals typically form in hot 75 c waters that have a low ca content 1 a high co2 content and a high rate of co2 degassing at chemurkeu aggregates of numerous small platy crystals collectively form lattice crystals that superficially resemble ray crystals the walls of the lattice crystals are formed of large platy crystals that have their long and intermediate length axes aligned parallel to the plane of the long axis of the lattice crystal internally the lattice crystals are formed of small platy calcite crystals arranged in a box like pattern that creates the appearance of a lattice when viewed in thin section lattice crystals are highly porous with each pore being enclosed by platy crystals at lorusio travertines are mainly formed of pseudodentrites that are constructed by numerous small platy crystals attached to a main stem which is a large platy crystal that commonly curves along its long axis the pseudodentrites are the main construction blocks in ledges and lilypads that form in the vent pool and spring outflow channels where the water is too hot for microbes other than hyperthermophiles the platy calcite crystals in the kenyan travertines are morphologically similar to platy calcite crystals that form as scale in pipes in the geothermal fields of new zealand and hydrothermal angel wing calcite from the la fe mine in mexico comparison of the kenyan and new zealand crystals indicates that platy calcite crystals form from waters with a low ca2 content and a high co3 ca ratio due to rapid rates of co2 degassing

calcite fabrics growth mechanisms and environments of formation in speleothems from the italian alps and southwestern ireland five fabrics were identified in alpine and irish caves on the basis of morphological and microstructural characteristics and re lated to growth mechanisms and growth environment columnar and fibrous fabrics grow when speleothems are continuously wet and from fluids at near equilibrium conditions low supersaturation sicc 0 35 through the screw dislocation mechanism the highly defective microcrystalline fabrics form at the same supersaturation range as co lumnar fabric but under variable discharge and the presence of growth inhibitors dendritic fabrics which have the highest density of crystal defects develop in disequilibrium conditions high supersaturation un der periodic very low flow regime periods that result in prolonged out gassing cave calcareous tufa forms in disequilibrium conditions only the calcite crystals of fabrics formed at low supersaturation seem to precipitate near isotopic equilibrium conditions

speleothems and climate a special issue of the holocene speleothems cave dripstones are formed as a part of the meteoric water cycle and therefore vari ations in their growth rate and composition reflect environmental changes on the land surface above the cave since they are continental deposits and possess a remarkably accurate dating potential using tims u series techniques speleothems are important palaeoclimatic archives for the terrestrial environment complementing the marine and ice core records the climatic proxies that can be deciphered from speleothems are growth rate stable isotope composition d18o d13c organic humic matter and trace element composition as well as luminescent laminae which may display annual rhythms the nine papers in this special issue oftheholocene present the latest results in palaeoclimatic analysis from speleothems

mineral precipitation and dissolution at two slag disposal sites in northwestern indiana usa slag is a ubiquitous byproduct of the iron and steel refining industries in northwestern indiana and northeastern illinois slag has been deposited over more than 52 km2 of land surface despite the widespread use of slag for fill and construction purposes little is known about its chemical effects on the environment two slag disposal sites were examined in northwestern indiana where slag was deposited over the native glacial deposits at a third site where slag was not present background conditions were defined samples were collected from cores and drill cuttings and described with scanning electron microscopy and electron microprobe analysis ground water samples were collected and used to assess thermodynamic equilibria between authigenic minerals and existing conditions differences in the mineralogy at background and slag affected sites were apparent calcite dolomite gypsum iron oxides and clay minerals were abundant in native sediments immediately beneath the slag mineral features indicated that these minerals precipitated rapidly from slag drainage and co precipitated minor amounts of non calcium metals and trace elements quartz fragments immediately beneath the slag showed extensive pitting that was not apparent in sediments from the background site indicating chemical weathering by the hyperalkaline slag drainage the environmental impacts of slag related mineral precipitation include disruption of natural ground water flow patterns and bed sediment armoring in adjacent surface water systems dissolution of native quartz by the hyperalkaline drainage may cause instability in structures situated over slag fill or in roadways comprised of slag aggregates

erratum to reply to the comment on physical and stable isotope evidence for formation of secondary calcite and silica in the unsaturated zone yucca mountain nevada by y v dublyansky s e smirnov and g p palyanova applied geochemistry 19 2004 1879 1889

polycyclic aromatic hydrocarbons in stalagmites occurrence and use for analyzing past environments this article presents a preliminary investigation into the value of polycyclic aromatic hydrocarbons pahs as markers for interpreting past environments in karst areas we analyzed a core sample representing the last 400 years growth from a massive stalagmite in the chevaline cave vercors france together with the soil overlying the karst directly above the stalagmite during the last millennium this area has been profoundly affected by human activities such as slash and burn agriculture charcoal burning and forestry these activities may have induced changes in pah production in the soil and thus in the pah record in the stalagmite pahs were extracted using both the soxhlet method and the ultrasonic method in order to compare extraction yields the ultrasonic method in conjunction with classic hplc fluo analysis was adopted for the analyses as it gave the greater yields pah distributions were obtained for the stalagmite and for the overlying soils the sum of the pah measured in the stalagmite ranges from 18 to 30 ng g furthermore the more soluble and labile pahs lighter than anthracene dominated the pah distribution in the stalagmite about 90 of low molecular weight pah however we did not find any obvious source fingerprints in the soil or the stalagmite and we observed an unexpected discrepancy between the pah distributions in the stalagmite and its stratigraphy which is controlled by mineral and organic inclusions although pah analyses can provide valuable data about the transfer of organic compounds in the karst it is difficult to extract meaningful paleoenvironmental information from pahs in stalagmites over the time scale of this study

influence of mg2 on the kinetics of calcite precipitation and calcite crystal morphology abstract the kinetics of calcite growth in the presence of mg2 has been studied by both a ph free drift method and by visual observation our experiments show that the calcite growth rate is reduced by the presence of mg2 the higher the mg ca ratio in the solution the lower the growth rate in a caco3 supersaturated solution the inhibition of calcite growth by the presence of mg2 is caused by mg2 being incorporated into the original calcite seed surfaces and developing new crystal surfaces the mg2 distribution on the calcite surfaces is not uniform as there is likely to be different mg2 densities on the newly developed surfaces than on the original surfaces of the calcite seeds this causes the calcite crystal morphology to change the significance of creating error in using the initial rate data rather than the equilibrium rate data for the prediction of the calcite precipitation kinetics is discussed

concretion morphology classification and genesis abstract a discussion of the most relevant morphological features of concretionary bodies and the different classifications and the criteria involved in these classifications is presented together with suggestions for improvements to the various classification schemes the meaning of syngenetic diagenetic and epigenetic related to the relative timing and environment of growth of concretionary bodies is also reviewed and discussed the replacement of mixed morphogenetic classifications which lead to conflicting results by classification categories based on textural features is proposed because the identification of the genetic environment of a concretionary body tells little about its history i recommend defining growth patterns in which the successive steps associated with changes in composition and or texture and the development of new structures are recorded a new path is presented that accounts for the contradiction between textural and isotope features which suggests respectively syngenetic and diagenetic or even epigenetic signatures this new path is characterized by the preservation of large porosities over very long time spans and down to depths that are somewhat greater than expected due to the inhibition of normal compaction caused by early overpressuring this overpressuring is the result of the development of hydraulic seals since approximately the syngenetic phase times the concepts of force of crystallization and displacive growth are also reviewed it is being suggested to discard some controversial interpretations of their actual importance for true concretionary displacive growth under epigenetic conditions in accordance with other authors the conclusion is reached that displacive growth is only possible if the shear strength of the host is very low and the stress field within the host is almost hydrostatic a new model the symcompactional concretionary growth model is proposed which explains how a concretionary body generally a nodule can grow while its host thins down by compaction this overpressured undercompacted model will be useful for the interpretation of an assemblage of features such as injection dikes hydraulic breccias cone in cone structures among others that are thought to be representative of the former presence of overpressured horizons these overpressured horizons could serve as detachment planes in paleotectonically active basins seals that could have controlled the movement of brines and hydrocarbons during the diagenetic evolution of the basin can also be assessed this is relevant for the identification of maturation conditions the potential development of secondary fracture permeability due to hydraulic fracturing in buried areas of the basin can also be evaluated based on the identification of formerly overpressured horizons in outcrops the origin of concretions is generally a geological puzzle clifton 1957

columnar calcites as testimony of diagenetic overprinting at the boundary between upper tournaisian dolomites and limestones belgium multiple origins for apparently similar features in topographic flat areas sedimentary settings may vary from one outcrop to another in these settings calcite precipitates may yield macroscopically similar columnar features although they are products of different sedimentary or diagenetic processes three columnar calcite crystal fabrics i e rosettes palisade crusts and macro columnar crystal fans have been differentiated near and at the contact between upper tournaisian dolomites and limestones along the southern margin of the brabant wales palaeohigh their petrographic characteristics and geochemical and fluid inclusion data provide information on the dia genetic processes involved rosettes composed of non luminescent columnar calcite crystal fans 1 5 cm in diameter developed on top of one another forming discrete horizons in repetitive sedimentary cycles the cycles consist of three horizons i a basal horizon with fragments from the underlying horizon ii a micrite microspar horizon with incipient glaebules iii an upper horizon consisting of calcite rosettes with desiccation features the petrographical features and 18o signatures of 10 0 to 5 5 and 13c values of 5 5 to 3 2 support either evaporative growth an evaporative pedogenic origin or overprinting of marine precipitates palisade crusts composed of a few to 10 mm long nonluminescent calcite crystals coat palaeokarst cavities successive palisade growth stages occur which are separated by thin laminae of micrite or detrital quartz displaying a geopetal arrangement palisade crusts are interpreted as intra mississippian speleothems this interpretation is supported by their petrographic characteristics and isotopic signature 18o 8 7 to 6 5 and 13 4 8 to 2 5 macro columnar crystals 1 50 cm long developed mainly perpendicular to cavity walls and dolomite clasts crystal growth stages in the macro columnar crystals are missing 18o values vary between 6 4 and 6 8 and 13c values between 5 2 and 0 9 these features possibly support a late diagenetic high temperature precipitation in relation to hydrothermal karstification 2005 international association of sedimentologist

laboratory investigation of the bruun rule and beach response to sea level rise abstract rising sea levels are expected to cause widespread coastal recession over the course of the next century in this work new insight into the response of sandy beaches to sea level rise is obtained through a series of comprehensive experiments using monochromatic and random waves in medium scale laboratory wave flumes beach profile development from initially planar profiles and a 2 3 power law profile exposed to wave conditions that formed barred or bermed profiles and subsequent profile evolution following rises in water level and the same wave conditions are presented experiments assess profile response to a step change in water level as well as the influence of sediment deposition above the still water level e g overwash a continuity based profile translation model ptm is applied to both idealised and measured shoreface profiles and is used to predict overwash and deposition volumes above the shoreline quantitative agreement with the bruun rule and variants of it is found for measured shoreline recession for both barred and bermed beach profiles there is some variability between the profiles at equilibrium at the two different water levels under these idealised conditions deviations between the original bruun rule the modification by rosati et al 2013 and the ptm model predictions are of the order of 15 and all these model predictions are within 30 of the observed shoreline recession measurements of the recession of individual contour responses such as the shoreline may be subject to local profile variability therefore a measure of the mean recession of the profile is also obtained by averaging the recession of discrete contours throughout the active profile the mean recession only requires conservation of volume not conservation of profile shape to be consistent with the bruun rule concept and is found to be in better agreement with all three model predictions than the recession measured at the shoreline

reassessment of carbonate ages by dating both carbonate and organic material from an etosha pan namibia stromatolite evidence of humid phases during the last 20ka abstract previous research on lacustrine stromatolites from etosha pan in namibia obtained ages on carbonate close to or beyond the limits of radiocarbon dating these ages suggested that the basin was likely not subject to extensive flooding during the last ca 40 ka this study shows that ams radiocarbon ages for the carbonate of a stromatolite from poacher s point are 15 21 ka older than ages for organic material in the stromatolite structure calibrated ages range from 30 to 40 ka for carbonate and 3 19 ka for the organic residue the new ages together with petrographic and isotopic data for the stromatolite have provided important new information on past flooding of etosha pan including evidence of prolonged lacustrine conditions during the holocene climatic optimum

fossil water in large stalagmite voids as a tool for paleoprecipitation stable isotope composition reconstitution and paleotemperature calculation the deuterium content of macroscopic fluid inclusions several millimetres large observed on two stalagmite polished sections has been measured with high accuracy f0 5x although several recent studies have already focused on the stable isotope content of microscopic fluid inclusions this is the first time that such measurements have been made on large inclusions by direct injection of the water in the spectrometer eliminating technical problems due to the extraction of water from microscopic inclusions crushing and heating the first results from four fluid inclusions of two stalagmites of south western and southern france demonstrate that 1 for the same stalagmite and the same age the deuterium content is similar 2 the fluid inclusion deuterium content difference between the sites is in agreement with the present day dripping water 3 calculated paleotemperatures at 100 ka are in the range of those derived from pollen marine and ice core records despite the fact that macroscopic fluid inclusions have rarely been observed it appears that they can give precious data for paleoclimatologists on the stable isotope content d 18 o dd and deuterium excess d of the past cave dripping water which is a proxy of the rainfall water and that it can be accurately dated by the tims u th method on the host calcite up to 500 ka d 2002 elsevier science b v all rights reserved

microbial kinetic controls on calcite morphology in supersaturated solutions recognizing microbial imprints in the morphology of calcium carbonate minerals that form in very supersaturated solutions containing a high level of dissolved inorganic carbon dic is challenging to better define criteria for this purpose we have analyzed the influence of sulfate reducing bacterium desulfovibrio desulfuricans strain g20 on the morphology of calcite in such solutions g20 does not induce large shifts of ph or alkalinity under these conditions but its uptake of millimolar sulfate and lactate decreases the number of anhedral crystals and stimulates growth of subhedral spar crystals relative to the abiotic controls in addition organic compounds associated with the basal growth medium purified exopolymeric substances produced by g20 and lypopolysaccharide stimulate the growth of anhedral crystals and crystals with rounded edges at low supersaturation index si of calcite the effect of organic compounds is reduced at higher si where rhombohedral habits dominate our results suggest that the local production and uptake of kinetic inhibitors within microbial biofilms may be an important control on calcite morphology in supersaturated solutions

laminated carbonate deposits in roman aqueducts origin processes and implications carbonate deposits in roman aqueducts of patara and aspendos southern turkey were studied to analyse the nature of their regular layering optical microscopy and electron backscattered diffraction results show an alternation of dense coarsely crystalline translucent laminae composed of bundles and fans of elongate calcite crystals with their c axes parallel to the long axis and porous fine grained laminae with crystals at near random orientation the 18o and 13c data show a strong cyclicity and anti correlation whereby high and low 18o values correspond to dense columnar and porous fine grained laminae respectively geochemical analyses show similar cyclic changes in carbonate composition electron microprobe and laser ablation inductively coupled mass spectrometry analyses show that porous fine grained laminae are enriched in elements associated with detrital material fe mg k al and si whereas the dense columnar laminae are nearly pure calcite the gradient in major and trace element distribution regular changes in crystal type and in oxygen and carbon isotope composition from porous fine grained to dense columnar laminae reflect changes in water chemistry discharge temperature and biological activity because of the strong bimodal cyclicity of the mediterranean climate in southern turkey the observed laminae can be attributed to calcite deposition during the dry porous fine grained and wet season dense columnar respectively this observation implies that with proper geochemical and microstructural control lamination in carbonate deposits in roman aqueducts can be used for relative dating of aqueduct construction and maintenance and to obtain data on external factors that influenced the aqueducts such as palaeoclimate and natural hazards carbonate deposits in roman aqueducts show properties of both flowstone speleothems and riverine fresh water tufa as many aqueducts of nearly identical channel geometry are present in different climate zones and with different source water characteristics they can be used as natural experiment setups to test and improve existing models of how laminated fresh water carbonates record climate on time scales ranging from seasonal to millennial

oil generation induces sparry calcite formation in lacustrine mudrock eocene of east china abstract sparry calcite is common in sedimentary rocks in mudrocks it has been reported to occur as veins in bedding parallel oblique and vertical fractures tectonic forces were traditionally suggested to be responsible for the calcite vein formation some recent studies showed that hydrocarbon generation could be responsible for forming bedding parallel calcite veins of fibrous sparry calcite however the process of sparry calcite formation by hydrocarbon generation is not well understood sparry calcite is common in the eocene mudrocks of the zhanhua and dongying sags of the bohai bay basin and the biyang sag of the nanxiang basin east china in this study the petrology carbon and oxygen isotopes minor geochemistry fluid inclusion and drill stem testing characteristics of sparry calcite and or sparry calcite bearing intervals in mudrocks were investigated oil generation could lead to overpressure inducing accommodation space for the precipitation of sparry calcite while organic acids a by product of oil generation promoted the dissolution of micrite providing an ion source for diagenetic sparry calcite growth structureless mudstone can experience elastic deformation before fracture generation forming equant and dispersed sparry calcite laminated shale on the other hand easily reaches the yield point because of its anisotropic nature an upward seepage force by fluid overpressure can induce bedding parallel fractures resulting in three stages of sparry calcite formation characterized by 1 discrete and equant sparry calcite 2 horizontally intergrown and equant sparry calcite and 3 horizontally intergrown and fibrous sparry calcite thus oil generation can be responsible for sparry calcite formation establishing some new characteristics for this process in mudrocks including 1 sparry calcite could also form during the process of elastic deformation as well as fracturing in mudrock and 2 fibrous sparry calcite began its growth from equant sparry calcite

preliminary paleoclimate reconstruction based on a 12 500 year old speleothem from vancouver island canada stable isotopes and u th disequilibrium dating abstract a combination of 13 c and 18 o analyses with u th disequilibrium dating on a stalagmite and groundwater from the deep and extensive arch cave network on northeastern vancouver island has produced a preliminary 12 200 y paleoclimatic profile speleothem depositional rates vary from 6 to 41 mm ka and are consistent with the hendy test for speleothem deposition under high humidity equilibrium conditions relative to present day conditions warmer periods are indicated at the end of the younger dryas during the holocene maximum a possible medieval warming event with the warmest period represented by a narrow peak at 8000 y bp relatively cooler periods are recorded at 3500 8200 9300 and 11 500 y bp with indications of minor cooling during the little ice age and indications of relatively dry conditions during the earlier part of the younger dryas followed by warmer wetter conditions the profile shows excellent agreement with other paleoclimatic indicators locally most notably some partial speleothem records from vancouver island and oregon and some high resolution global records such as the greenland ice cores and speleothems from the hulu cave china

pleistocene speleothems of mallorca implications for palaeoclimate and carbonate diagenesis in mixing zones the pleistocene speleothems of sa bassa blanca cave mallorca are excellent indicators of palaeoclimate variations and are samples that allow evaluation of the products and processes of mixing zone diagenesis in an open water cave system integrated stratigraphic petrographic and geochemical data from a horizontal core of speleothem identified two main origins for speleothem precipitates meteoric marine mixing zone and meteoric vadose zone mixing zone precipitates formed at and just below the water air interface of cave pools during interglacial times when the cave was flooded as a result of highstand sea level mixing zone precipitates include bladed and dendritic high mg calcite microporous bladed calcite with variable mg content and acicular aragonite their presence suggests that calcium carbonate cementation is significant in the studied mixing zone system fluid inclusion salinities 13c and 18o compositions of the mixing zone precipitates suggest that mixing ratio was not the primary control on whether precipitation or dissolution occurred rather the proximity to the water table and degassing of co2 at the interface were the major controls on precipitation thus simple two end member mixing models may apply only in mixing zones well below the water table meteoric vadose speleothems include calcite and high mg calcite with columnar and bladed morphologies vadose speleothems precipitated during glacial stages when sea level was lower than present progressive increase in 13c and 18o of the vadose speleothems resulted from cooling temperatures and more positive seawater 18o associated with glacial buildup such covariation could be considered as a valid alternative to models predicting invariant 18o and highly variable 13c in meteoric calcite glacio eustatic oscillations of sea level are recorded as alternating vadose and mixing zone speleothems short term climatic variations are recorded as alternating aragonite and calcite speleothems precipitated in the mixing zone fluid inclusion and stable isotope data suggest that aragonite as opposed to calcite precipitated during times of reduced meteoric recharge

reconstructing water level in hoyo negro quintana roo mexico implications for early paleoamerican and faunal access abstract the skeletal remains of a paleoamerican naia hn5 48 and extinct megafauna were found at 40 to 43 mbsl in a submerged dissolution chamber named hoyo negro hn in the sac actun cave system yucatan peninsula mexico the human remains were dated to between 12 and 13 ka making these remains the oldest securely dated in the yucatan twelve sediment cores were used to reconstruct the holocene flooding history of the now phreatic cave passages and cenotes ich balam oasis that connect to hn four facies were found 1 bat guano and seed sf 2 lime mud mf 3 calcite rafts crf and 4 organic matter calcite rafts om crf which were defined by their lithologic characteristics and ostracod foraminifera and testate amoebae content basal radiocarbon ages ams of aquatic sediments sf combined with cave bottom and ceiling height profiles determined the history of flooding in hn and when access was restricted for human and animal entry our results show that the bottom of hn was flooded at least by 9850 cal yr bp but likely earlier we also found that the pit became inaccessible for human and animal entry at 8100 cal yr bp when water reaching the cave ceiling effectively prevented entry water level continued to rise between 6000 and 8100 cal yr bp filling the cave passages and entry points to hn cenotes ich balam and oasis analysis of cave facies revealed that both holocene sea level rise and cave ceiling height determined the configuration of airways and the deposition of floating and bat derived om guano and seeds calcite rafts which form on the water surface are also dependent on the presence of airways but can also form in isolated air domes in the cave ceiling that affect their loci of deposition on the cave bottom these results indicated that aquatic cave sedimentation is transient in time and space necessitating extraction of multiple cores to determine a limit after which flooding occurred

the role of carbonate complexes and crystal habit on rare earth element uptake in low temperature calcite in fractured crystalline rock abstract this study focuses on rare earth element ree geochemistry of low temperature calcite coatings occurring on the walls of fractures throughout the upper kilometer of crystalline rocks of the baltic shield fifty one calcite coatings were sampled from cores drilled with the triple tube technique which successfully preserved the fragile calcite coatings on the fracture walls the calcites which based on geological and isotopic evidence were precipitated over the last 10 million years had highly variable ree concentrations 0 61 2276 ppm that decreased weakly with the depth the calcite was sampled from when normalized to shale and host rock the ree concentrations of habits with c axis a axes and the closely associated c axis a axes the most abundant crystal morphologies in the system decreased strongly and smoothly across the series in contrast the rees of habits with c axis a axes identified only in fractures in the uppermost 260 m of the bedrock were flatter and occasionally expressed a weak middle ree enrichment by using calcite water partition coefficients derived for rees in previous laboratory experiments the la yb of the paleogroundwater from which the calcites precipitated was back calculated and found to be overall similar range 0 15 452 overlap to the corresponding ratio of the present groundwater range 2 1 36 4 in terms of ree ca the values for the back calculated paleogroundwater la ca 9 9 10 11 3 9 10 7 yb ca 1 5 10 10 2 2 10 7 were similar to those of laco3 ca 4 5 10 10 8 5 10 7 and ybco3 yb co3 2 ca 5 4 10 11 1 8 10 8 respectively in the present groundwater these patterns indicate that the lree to hree and ree to ca ratios in the groundwater at the site are broadly similar to those existing when the calcites precipitated and that carbonate complexes present in the paleogroundwater played a crucial role in sequestration and fractionation of rees in calcite the findings have implications for bedrock storage of high level radioactive waste which contains actinides for which the rees can be used as natural analogues

carbonate botryoids in lower devonian amygdaloidal basalts evidence for precipitation of high magnesium calcite from heated and volcanic co 2 buffered marine waters abstract amygdaloidal basalts are found in the lower devonian upper gaspe limestones in the gaspe peninsula these basalts were extruded on a distal outer shelf as evidenced by field relationships embedded fragments of metazoans and high vacuole content the lava flows were fractured and brecciated the network of fractures allowed connections of some vesicles with seawater vesicles in the nonfractured basalt are filled by silicates whereas those opened to seawater are filled by carbonates the latter comprise in stratigraphic order geopetal micrite botryoidal calcite and coarse anhedral calcite petrographic attributes including microdolomite inclusions and trace element distribution in the botryoids indicate former high magnesium calcite mineralogy the d18opdb 9 2 to 10 0 and d13cpbd 3 0 to 5 3 ratios support botryoid precipitation from heated marine waters that were contaminated by magmatic co2 volatiles high radiogenic sr values originated from compaction waters expelled from the host succession submarine high magnesium calcite agrees with the aragonite inhibiting stage for the early devonian the botryoid fabric should be the norm for early calcite in such an odd diagenetic setting

calcite precipitation in synthetic veins implications for the time and fluid volume necessary for vein filling although calcite is a common vein filling mineral in rocks there has been little understanding of the kinetics of vein filling that gives a quantitative estimation of the fluid volume and time needed for calcite vein formation in subsurface fracture systems a new experimental system capable of simulating calcite precipitation in veins was used to determine the influences of flow velocity and initial solution saturation state on the quantitative precipitation pattern of calcite in synthetic veins results are in relatively good agreement with the model predictions use of a mn2 tracer indicated that even at low concentrations manganese can have a substantial effect on the morphology of the calcite precipitate our model predicts that an extremely large volume of fluid is required to produce calcite veins in nature typically 105 to 106 for a fluid calcite volume ratio for formation of thin short veins the model also predicts the time necessary for vein filling is thousands to millions of years and is highly variable depending on factors such as fluid saturation state flow velocity vein dimension and the precipitation kinetics that can differ under subsurface conditions

a stepwise screening system to select storm sensitive stalagmites taking a targeted approach to speleothem sampling methodology a stepwise stalagmite sample screening process was applied in order to select a stalagmite as a sensitive recorder of recent tropical cyclone rainfall events near belize field and laboratory criteria were combined in series to screen out candidate stalagmites whose characteristics indicated lower sensitivity to stormwater infiltration the approach described here was designed to increase the likelihood that selected stalagmites would increase the signal noise ratio of the target phenomenon in the resulting proxy records this four stage method for sample selection may be an important methodological consideration for researchers attempting to use speleothems for stable isotope paleotempestology hallmarks of this approach include 1 establishing a priori scientific targets 2 applying sample criteria in the form of contra indicators and 3 organizing the sample screening protocol into a series of practical stages the overall approach to stalagmite selection presented here supports cave conservation and can be adapted readily by others in support of different scientific goals it is hoped that other investigators will also publish field and laboratory sample selection schemes as increased transparency will provide new information invaluable to replication efforts and to advancing the field of speleothem paleo environmental studies

calcite veining and feeding conduits in a hydrothermal system insights from a natural section across the pleistocene golemezli travertine depositional system western anatolia turkey abstract linking the architecture of structural conduits with the hydrothermal fluids migrating from the reservoir up to the surface is a key factor in geothermal research a contribution to this achievement derives from the study of spring related travertine deposits but although travertine depositional systems occur widely their feeding conduits are only rarely exposed the integrated study carried out in the geothermal golemezli area nearby the well known pamukkale area denizli basin western anatolia turkey focused on onyx like calcite veins banded travertine and bedded travertine well exposed in a natural cross section allowing the reconstruction of the shallower part of a geothermal system the onyx like veins represent the thickest vein network 150 m so far known new field mapping and structural kinematic analyses allowed to document a partially dismantled travertine complex bedded travertine formed by proximal fissure ridges and distal terraced pools depositional systems the banded calcite veins wnw trending and up to 12 m thick developed within a 200 m thick damaged rock volume produced by parallel fault zones th u dating indicates a long lasting middle late pleistocene fluids circulation in a palaeo geothermal system that due to its location and chemical characteristics can be considered the analogue of the nearby still active pamukkale system the isotopic characteristics of the calcite veins together with data from fluid inclusions analyses allow the reconstruction of some properties i e temperature salinity and isotopic composition and processes i e temperature variation and intensity of degassing that characterized the parent fluids and the relation between degassing intensity and specific microfabric of calcite crystals elongated microsparite micrite bands controlled by changes fluctuations of the physico chemical fluid characteristics

intergranular aragonite cement as evidence for widespread cryogenic brine formation during quaternary glaciation in the mcmurdo sound region antarctica abstract briny groundwater is present below the extremely cold and dry surface of the mcmurdo dry valleys and below the seafloor of the adjacent mcmurdo sound in antarctica the lack of reliable groundwater samples in the region however has long limited understanding of its origin nature and spatial distribution in this regard intergranular carbonate cements widespread in subsurface cenozoic strata and recently recognized as brine precipitates provide an indirect means of solving these issues this study examines the petrography and isotope geochemistry of intergranular aragonite cement phases that occur in subsurface pliocene quaternary sedimentary sections that formed in the lower taylor valley cores dvdp 10 11 and in offshore mcmurdo sound core and 1b aragonite cement in the coastal taylor valley sections is characterized by very low 18o values 26 9 to 19 4 vpdb compared to values in the offshore section 12 5 to 2 7 vpdb these differences are interpreted to reflect two settings for cryogenic brine formation which produced isotopically distinct brines during quaternary glaciation in the coastal region seawater meltwater mixtures were isolated and cryogenically concentrated in an ice dammed lake setting that formed in response to the expansion of the east and west antarctic ice sheets into the lower taylor valley in mcmurdo sound cryogenic concentration of seawater occurred in a semi isolated flexural trough that was deepened by lithospheric depression of volcanic edifices and the expanded west antarctic ice sheet aragonite cement phases serve as excellent proxies for tracing the extents of subsurface brine bodies along the continental margin of antarctica given the propensity for cryogenic brine formation in glaciomarine settings the likelihood of brine cements in rock records from other analogous high latitude cold settings must not be overlooked

floating rafts of calcite crystals in cave pools central texas u s a crystal habit vs saturation state abstract calcite precipitation at the air water interface in cave pools in central texas u s a produces floating rafts of interconnected low mg calcite crystals with individual crystal habits that range from equant length to width 1 1 to prismatic 4 1 saturation state for the waters ranges from 0 19 to 1 35 sic log iap k equant crystals precipitate from waters with a lower saturation index sic and form rafts with a fused fabric whereas prismatic crystals precipitate from higher sic waters and form rafts with an interlaced fabric the pools contain low magnesium molal mg ca 0 6 calcium bicarbonate and calcium bicarbonate nitrate type waters with temperatures that range from 13 8 c to 20 7 c and ph readings from 6 7 to 8 4 equant euhedral crystals precipitate from water with saturation states close to equilibrium visible defects in the equant crystals include incomplete edges between faces and nearly circular mean diameter 9 m to angular holes in faces the holes apparently result from crystallite growth around foreign objects on the crystal surface such as gas bubbles prismatic crystals precipitate from supersaturated water faces of these subhedral crystals are smaller in area than the faces of the equant crystals no intrafacial circular holes are seen but trigonal intercrystallite pores are common in the prismatic crystals the variety in crystal habits from equant to prismatic is due to preferential growth along one crystallographic axis thus in these cave pools crystal habit is related to the saturation state of the water

speleothem deposition at the glaciation threshold an attempt to constrain the age and paleoenvironmental significance of a detrital rich flowstone sequence from entrische kirche cave austria abstract proxy records from high altitude locations predating the last glacial maximum are rare but could provide invaluable insights into the response of alpine catchments to the rapid climate fluctuations which characterized the last glacial period here we present a detrital rich flowstone record from entrische kirche cave an inneralpine cave situated close to the accumulation area of the pleistocene ice stream network of the european alps that expanded repeatedly into the lowlands during glacial maxima u th dating of this calcite is challenging due to high detrital th however petrographic and stable isotope analyses in conjunction with associated clastic cave sediments provide useful insights into the climatic boundary conditions during speleothem formation and into the paleoenvironmental processes which operated in the 2000 m high catchment above the cave our data show that millennial scale temperature fluctuations had a first order control on the periglacial activity and vegetation in the catchment which strongly influenced the formation and infiltration of detritus into the karst aquifer the brown laminated and brown dendritic fabrics that compose much of the detrital rich flowstone succession reflect these environmental processes the temperature dependence of periglacial and permafrost processes allows to constrain the amount of cooling relative to the present day mean annual air temperature that is required to initiate detrital rich calcite formation in entrische kirche cave i e 2 5 c minimum to 6 c maximum respectively white inclusion poor calcite that is intercalated with the detrital rich calcite indicates warm interstadial conditions and geomorphological stability in the catchment area one such phase has been u th dated to 88 3 6 9 ka i e greenland interstadial 21 or 22

inorganic calcite morphology roles of fluid chemistry and fluid flow abstract evaluation of calcite crystal habits and fabric and their relation to precipitating fluids in spelean environments indicates that habit variations are controlled primarily by degree of supersaturation at less than 6 times supersaturation crystal habits are limited to those with shallow to steep rhombohedral forms i e 1011 4041 with increasing supersaturation scalenohedrons extremely steep rhombohedrons pinacoids and hexagonal prisms are developed slight elongation due to differences in crystal dimensions of these forms may arise i e scalenohedrons versus shallow rhombohedrons at extreme supersaturation 12 times curvature of crystal faces or curved surfaces appear the development of fibrous versus equant fabrics is the result of changes or modification of reactant supply rates and the number of crystallites nuclei present under rapid flow conditions growth rates are accelerated and greater numbers of nuclei are present thus compromise boundaries parallel to c axis and perpendicular to flow and substrate are rapidly attained in the absence of flow fewer crystallites are present and larger well developed crystals or branching forms dictated by saturation conditions arise in the absence of flow at low supersaturation elongate composite crystals and hence fibrous fabrics may result from migration of the fluid crystal interface as a result of changing or oscillating water levels a flow control mechanism can be applied to numerous geological conditions in which transitions from fibrous to equant crystal morphologies are observed

calcite cemented concretions in cretaceous sandstone wyoming and utah u s a abstract spheroidal cannon ball calcite cemented concretions some of gigantic size were studied from three cretaceous shelf sandstone units ferron frontier and second frontier the concretions have diameters between 2 cm and 6 m those larger than 40 cm in diameter in the ferron and frontier have septarian structure rare concretions in the second frontier with cone in cone also have septaria the pattern of carbon and oxygen isotopic data and intergranular volume igv data across concretions indicate that concretion growth was complex not all concretions grew progressively from their centers toward their edges in many concretions displacive fascicular optic high mg calcite foc precipitated simultaneously throughout the concretions pervasive growth pattern although the earliest cementation was concentrated in and near their centers remaining pores were subsequently filled by poikilotopic calcite of lower mg content displacive foc cement in the bodies of concretions and in cone in cone structure and the large igv values indicate that these carbonate phases formed at burial depths no greater than tens of meters igv values indicate that spar cement continued to depths of at least 50 m and possibly deeper the association of organic matter and microbial structures or microbial byproducts with displacive foc and cone in cone calcite raises the possibility that biogenic processes were responsible for the apparently rapid growth of the displacive calcite the oxygen isotope composition of pore waters was fairly uniform in the range of 18o of 4 to 6 smow during 80 of concretion growth but became even more depleted in 18o during the last stage of growth and during septarian fracture filling ranging into values as depleted as 14 smow 13c in calcite is negative 4 to 18 v pdb but variable reflecting a range of microbial processes under both oxidizing and reducing conditions earlier calcites fall mostly in the range of 10 to 16 v pdb relatively later calcite in veins and on concretion margins is more enriched in 13c fe and mn concentrations in calcites have a rough positive correlation with higher 13c values the concentration of mg derived from seawater and altered volcanic rock fragments covaries positively with the degree of meteoric influence lower mg contents correlate positively with relatively depleted 18o values 87sr 86sr values are typical of sr derived from coeval seawater or marine skeletal debris growth of concretions 4 to 6 m in diameter apparently in 5 my requires some spatial localization of growth sites by a self organization process and probably a large supply of carbonate shells in the original sediment elongation of larger concretions in the plane of bedding suggests that advective rather than diffusive supply of cement components dominated late in concretion growth history concretions formed close to the tops of parasequence boundaries

chemistry of waters from selected caves in slovakia a reconnaissance study the chemical composition of water samples was studied from different caves in slovakia the water samples were collected from caves of two karst regions 1 the demanovsk cave system dcs situated in the low tatra mountains northern slovakia which is mainly formed of limestone and dolomites and 2 the slovakian karst to the southeast is formed of limestone a considerable difference between water from the two regions was shown the waters from the dcs that were controlled by vadose water percolating through different types of host rocks contained more mg ions than those from the slovakian karst caves whereas the concentration of so4 was controlled by the dissolution of displacive gypsum and or oxidation of pyrite the distribution of no3 in the studied samples was random hence nitrates probably derived from few pollution sources the total mineralization of the water was covariant with calcite and aragonite saturation indices in general both parameters are higher in the slovakian karst caves than in the dcs it is controlled probably by differences in climatic conditions soil and plant covers between these two regions the main goal of this article is to characterize the major ion water chemistry within the studied caves as well as some microelements the results have confirmed the dominant role of the bedrock petrography in forming the general chemistry of cave waters

isotopic and morphological features of fracture calcite from granitic rocks of the tono area japan a promising palaeohydrogeological tool this study aimed to develop a methodology for assessing the hydrochemical evolution of a groundwater system using fracture filling and fracture lining calcite fracture calcite in deep to ca 1000 m granitic rocks of the tono area central japan was investigated by optical and electron microscopy and chemical and isotopic analysis coupled with geological evidence these new data imply 3 main origins for the waters that precipitated calcite 1 relatively high temperature hydrothermal solutions precipitating calcite distinguished by 18osmow from 3 to ca 10 and with 13cpdb from ca 18 to 7 2 seawater probably partly of miocene age which precipitated calcite distinguished by 13cpdb of ca 0 and 18osmow ca 20 3 fresh water with a variable 13cpdb composition but which precipitated calcite distinguished by 13cpdb that was significantly ca 17 data for 14c suggest that at least some of the fresh water calcite formed within the last 50 ka the present day hydrogeological regime in the tono area is also dominated by fresh groundwater however the marine calcite of probable miocene age found at depth has shown no evidence for dissolution and many different calcite crystal forms have been preserved studies of other groundwater systems have correlated similar crystallographic variations with variations in the salinity of coexisting groundwaters when this correlation is applied to the tono observations the calcite crystal forms imply a similar range of groundwater salinity to that inferred from the isotopic data thus the present study suggests that even in presently low salinity groundwater systems calcite morphological variations may record the changing salinity of coexisting groundwaters it is suggested that calcite morphological data coupled with isotopic data could provide a powerful palaeohydrogeological tool in such circumstances

palaeo climate reconstruction from stable isotope variations in speleothems a review abstract speleothems are now regarded as valuable archives of climatic conditions on the continents offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores they are ideal materials for precise u series dating yielding ages in calendar years thereby circumventing the radiocarbon calibration problems associated with most other continental records stable isotope studies in speleothems have shifted away from attempting to provide palaeo temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major o isotope defined climatic events characterised by high signal to noise ratios e g glacial interglacial transitions dansgaard oeschger oscillations the 8200 year event unlike the marine records speleothem data sets are not tuned and their independent chronology offers opportunities to critically assess leads and lags in the climate system that in turn can provide important insights into forcing and feedback mechanisms improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide in the near future a much enhanced basis for the quantitative interpretation of o isotope ratios in speleothem calcite the latter developments open up once again the tantalising prospect of palaeo temperature estimates but more importantly perhaps provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the water isotopes the literature is reviewed briefly to provide for the reader a sense of the current state of the art and to provide some pointers for future research directions

petrography strontium barium and uranium concentrations and strontium and uranium isotope ratios in speleothems as palaeoclimatic proxies soreq cave israel the reconstruction of the palaeoclimate of the eastern mediterranean region for the last 60 ka bp is based on the 18o and 13c variations of speleothems from soreq cave israel climatic conditions during most of the time interval between 60 and 17 ka bp the period equivalent to the last glacial were relatively cold and dry while they were warmer and wetter from 17 ka bp to the present at 17 ka bp there was a major climatic change with a sharp increase in annual rainfall and temperature and a very wet period occurring between 8 5 and 7 0 ka bp during the colder and drier period large detritus free preferentially oriented calcite crystals were deposited from slow moving water as a result of a sharp change in the hydrological regime at 17 ka bp fast moving water started entrainment of the soil and carrying detrital material into the cave and the calcite crystals deposited became small and anhedral coinciding with the petrographic and isotopic changes a sharp drop occurred in the concentration

relict landslide development as inferred from speleothem deformation tectonic data and geoelectrics abstract the direct dating of pre and postfaulting dislocated calcite speleothems afforded new insight into slope failure in the tatra mountains in southern poland a multi approach study of the karstic kalacka cave non crevasse type enabled us to infer the slope deformation structure which had been poorly preserved in ground surface topography using combined methods including geomorphological and structural mapping of cave and ground surfaces paleostress analysis near surface electrical resistivity tomography ert and induced polarization methods ip uranium series dating 234u 230th calcite microtexture analysis and stable isotope 18o and 13c analysis here slope deformation began with dilation between 280 7 ka and 265 8 ka and proceeded as deep seated gravitational slope deformations the final stage consisted of dilation rejuvenation and rockfall during the latest pleistocene or holocene post 35 4 ka additionally some dilations are evident beyond the extent of the landslide detected by ert indicating further progradation of slope failure since this failure was initiated during the climatic transition from mis 9 to mis 8 stable isotope analysis of calcite flowstone layers was applied to test climate factors the correlation of calcite microtexture and 18o and 13c compositional changes with the interval of dilation activity indicates that regional environment factors chiefly an increase in precipitation probably contributed to slope destabilization

origin and reservoir characteristics of upper ordovician trenton black river hydrothermal dolomite reservoirs in new york in the past decade more than 20 new natural gas fields have been discovered in laterally discontinuous dolomites of the upper ordovician black river group in south central new york the dolomites form around basement rooted wrench faults that are detectable on seismic data most fields occur in and around elongate fault bounded structural lows interpreted to be negative flower structures away from these faults the formation is composed of impermeable limestone and forms the lateral seal for the reservoirs in most cases the faults die out within the overlying trenton limestone and utica shale most porosity occurs in saddle dolomite coated vugs breccias and fractured zones matrix porosity is uncommon in the black river cores described for this study the patchy distribution around basement rooted faults and geochemical and fluid inclusion analyses supports a fault related hydrothermal origin for the saddle and matrix dolomites this play went for many years without detection because of its unconventional structural setting i e structural lows versus highs using the appropriate integrated structural stratigraphic diagenetic model more hydrothermal dolomite natural gas reservoirs are likely to be discovered in the black river of new york and in carbonates around the world

bacterial shrubs crystal shrubs and ray crystal shrubs bacterial vs abiotic precipitation hot water travertine deposits commonly contain shrub like morphologies on the centimeter to meter scale that range from highly irregular forms bacterial shrubs to features that display regular geometric patterns crystal shrubs and ray crystal crusts the bacterial shrubs have been previously recognized as the product of bacterially induced precipitation whereas the ray crystal crusts have been described as due to dominantly abiotic precipitation the bacterial shrubs have a highly irregular morphology similar to woody plants in contrast end member crystal shrubs display distinct crystal habits and regular repeating morphologies i e they commonly have attributes of noncrystallographic as well as crystallographic dendrites there is a complete gradational relationship between the bacterial shrubs and crystal shrubs ray crystal crusts are large fan shaped features composed of subparallel extremely coarse bladed crystals of calcite all three types bacterial shrubs crystal shrubs and ray crystal crusts contain either a dense tangle of bacterial body fossils and or micron sized pores the micropores are bacterial molds the immediately enveloping spar crystals around all three morphologic types are devoid of bacterial body fossils and micropores the bacterial shrubs crystal shrubs and ray crystal crusts are to differing degrees the product of bacterially induced precipitation as well as abiotic mineral precipitation the differences in morphology are due to the relative contribution of bacterially induced precipitation as compared with that of abiotic mineral precipitation bacterially induced precipitates can form in environments too chemically harsh or otherwise inhospitable for other taxa to thrive epiphyton and renalcis commonly formed in occult environments under conditions inhospitable to other taxa consideration of the published descriptions and interpretations concerning epiphyton and renalcis and by analogy the origin of bacterial shrubs have led to the conclusion that epiphyton and renalcis also are bacterially induced precipitates

uranium series chronology and environmental applications of speleothems an increasing number of scientists recognize the value of speleothems1 as often extremely well preserved archives of information about past climate vegetation hydrology sea level nuclide migration water rock interaction landscape evolution tectonics and human action well constrained data are required to document past changes reconstruct past patterns and predict future responses of the earth system at a wide range of spatial and temporal scales speleothems are particularly useful in this regard because they can be found in many locations of the globe sampled at high resolution and reliably dated using high precision uranium series techniques speleothems are bodies of mineral material formed in caves as the result of chemical precipitation from groundwater flowing or dripping in a cave most speleothems are composed of calcite formed by slow degassing of co2 from supersaturated groundwater but aragonite and gypsum forms are also common particularly near cave entrances where evaporative effects are important a host of different speleothem types decorate the walls ceilings and floors of caves and their mineralogy and morphology is a function of fluid flow and chemistry of waters feeding a particular location as well as the ambient conditions temperature chemistry light in the air or water filled void subaerial forms include the familiar stalagmites stalactites draperies flowstones subaqueous forms include rimstone pools rafts mammillary calcite wall coatings and dog tooth spar for an extensive review of the types of speleothem that have been observed see hill and forti 1997 speleothems are used in a multitude of ways to explore past environmental conditions perhaps the most fundamental of which is their very presence or absence deposition of speleothems relies on sufficient water supply and soil co2 to enable dissolution and transport of reactants in the vadose zone to underlying caves in arid or glacial times conditions may not have been favorable for speleothem formation

textural elemental and isotopic characteristics of pleistocene phreatic cave deposits jabal madar oman abstract two main types of karst formation are commonly known the surficial meteoric one and the subsurface hypogenic karst which can be related to both carbonic h2co3 and sulfuric h2s acids this paper documents evidence for a third co2 regime related type of karst that is less commonly described petrographic and geochemical properties of exhumed pleistocene phreatic cave deposits from the diapiric jabal madar dome in northern oman are documented and discussed in a process oriented context these calcites form at the interface between two fundamentally different diagenetic and hydrogeological domains the deep seated hydrothermal and the near surficial meteoric vadose one four calcite phases are recognized i acicular ii blocky to stubby elongated iii proto palisade and iv macro columnar calcites the macro columnar calcites forming the last stage of precipitation are conspicuous due to their cyclical red zonation and they form the main geochemical focus of this study fluid inclusion data point to fluid temperatures of between 30 to 50 c monophase liquid inclusions and elevated salinities 1 6 to 7 3 wt nacl equivalent low carbon isotope data 8 to 9 are in agreement with the influx of soil zone co2 whereas decreasing 18o 15 values might point to mixing of saline hydrothermal and 18o depleted meteoric freshwater i e two fluid sources trace element and stable isotope data shift between the different cement phases and vary cyclically across the red zoning in macro columnar calcites with respect to the intra crystal variability these patterns are perhaps best explained in the context of redox potential two interpretations are presented the one favored here suggests that the cyclical red zoning in macro columnar calcites is controlled by pleistocene monsoonal climate patterns

crystallization in flow i palaeocirculation track by texture analysis and magnetic fabrics summary in order to better define the dependence of the mineral texture on flow anisotropy of magnetic susceptibility ams and microscopic observations have been performed on calcite rich precipitations occurring in a horizontal pipe where the flow direction is clearly defined a total of 65 cubes were cut from five slices magnetic studies identified pseudo single domain magnetite as the major ams carrier horizontal foliation characterizes the magnetic fabrics and the lineation is parallel to the pipe axis that is the flow direction the origin of this lineation is discussed and is interpreted to be mainly the consequence of elongated pseudo single domain magnetite to complete the magnetic fabric studies shape preferred orientation statistics were performed on 563 calcite sections in the 0001 calcite plane it shows elongated shapes with a general orientation parallel to the pipe axis the mean shape orientation is the average of two distinct subpopulations that deviated slightly from the pipe axis observation on calcite shapes and the direction of the magnetic lineation are coherent suggesting that it is possible to track hydrothermal palaeocirculation using magnetic lineation and petrographic fabrics

the great barrier reef a 700 000 year diagenetic history a deep borehole through ribbon reef 5 in the great barrier reef off north eastern australia has identified a variety of cements including epitaxial radial prismatic and spherular aragonite together with blocky prismatic and fibrous calcite these cements are discontinuously arranged within the sequence that consists predominantly of grainstones but locally includes clotted muddy and filamentous textures that may be of microbial origin calcite cements vary in morphology with groups of crystals that include acute scalenohedral rhombohedral and flattened concordant terminations these show varying densities of inclusions that locally define growth zones and in some terminations divide in the manner of split crystals to form fibrous fringes morphological changes in calcite are inferred to reflect changes in water chemistry and crystal growth rates at the time of growth allied to their relationship to the palaeo water table and linked in turn to changes in sea level neomorphism and dissolution are widespread and variations in the severity of both imply response to the degree of undersaturation of pore waters that at times were probably balanced within very narrow limits a total of 10 depositional units are identified those units at the base of the borehole reflect deposition and diagenesis within a marine environment the influence of meteoric waters indicated by stable isotopes is first apparent at the top of unit 1 and in unit 2 184 to 155 m below sea floor petrographic evidence of vadose conditions appears at the tops of unit 3 131 to 99 m below sea floor units 4 to 8 all deposited under marine conditions provide isotopic evidence of meteoric or mixing zone waters and petrographic indicators of vadose conditions typically at the top of the units evidence indicates that in unit 5 the water table was mobile and units 6a 6b 7 and 8 all characterized by ultraviolet fluorescent cements are capped by sub aerial erosion surfaces unit 9 the holocene reflects the recent re establishment of marine conditions the extent of alteration of the entire sequence reflects the substantial and pervasive influence of meteoric waters this effect is interpreted as a result of a greater rainfall and river flow from the mainland during early and late stages of interstadial periods the study reflects progress in the ability to recognize the diagenetic signal generated by sea level change however whereas the isotopic results reflect the changing relationships between vadose and phreatic zones in groundwater systems beneath successive emergent surfaces their correspondence with petrographic features is expressed only weakly and commonly lacks the systematic sequential overprinting implied by the distribution of cathodoluminescent zones of cements in many ancient limestones

morphological and speleothemic development in brujas cave southern andean range argentine palaeoenvironmental significance abstract brujas cave in the southern andean range is a well known endokarstic site in argentina however the origin and evolution of this cave system are poorly known based on morphological cave features as well as characteristics of cave deposits we propose a meteogene drawdown cave genesis including a change from phreatic to vadose conditions related to the high rate of fluvial downcutting in the area during the vadose period various cave related deposits including authogenic calcite and gypsum speleothems allogenic volcanic ash and external tufas were deposited gypsum crusts are the oldest cave deposits identified 90 2 64 3 ky bp their origin deduced from isotopic characteristics 34 s 9 6 is related to the oxidation of pyrite contained in the jurassic limestone bedrock as well as the dissolution of overlying jurassic triassic evaporite formations gypsum crust deposition is associated with evaporation of water flowing and seeping into the cave during arid environmental conditions calcite deposits precipitated from flowing water under equilibrium conditions represent the main speleothem growth period 67 6 34 ky bp in age their stable isotope values 13 c 3 to 5 and 18 o 9 to 11 may indicate slightly humid and warm conditions related to the regional minchin lacustrine phase and global oxygen isotope stage 3 following this stage a seismic event is evidenced by accumulations of broken stalactites seepage calcite speleothems covering cave walls were deposited under disequilibrium conditions by evaporation probably during holocene time finally another more recent gypsum deposition period represented by gypsum balls has been differentiated micromorphological as well as isotopic 34 s 5 6 data indicate that these gypsum forms are related to cyclic processes solution deposition from water seeping into the cave under arid conditions in addition intense volcanic activity in the area during holocene time is deduced from allogenic volcanic ash and lapilli located mainly at the entrance cave at present limited hydrological activity is observed in the cave and small tufa deposits at karstic discharge points are evidenced we conclude that the geomorphological evolution of brujas cave was controlled by climatic changes wet and dry stages under semiarid environmental conditions in a very active tectonic and volcanic setting during late quaternary time

reply to the comment on physical and stable isotope evidence for formation of secondary calcite and silica in the unsaturated zone yucca mountain nevada by y v dublyansky s e smirnov and g p palyanova

abiotic versus biotic controls on the development of the fairmont hot springs carbonate deposit british columbia canada the relict fairmont hot springs deposit formed largely of carbonates covers an area of 0ae 5k m 2 and is up to 16 m thick the triangle shaped discharge apron which broadens down valley is divided into a proximal part with beds dipping at 10 and a distal part with beds dipping at 10 to 15 the deposit is formed of the 1 basal macrophyte 2 lower carbonate 3 middle clastic 4 upper carbonate and 5 upper clastic sequences two charcoal samples embedded in the lower carbonate sequence yielded dates of 8690 90 and 8270 70 cal yr bp indicating that much of the deposit formed post glacially during the early to mid holocene deposit aggradation ceased in the mid to late holocene when the fairmont creek valley was incised the lower and upper carbonate sequences which are the thickest sequences are composed of nearly equal parts of travertine abiotic and tufa biotic with feather dendrite travertine radiating dendrite travertine and stromatolite tufa dominating competition between calcite precipitation rates and biotic growth rates controlled the distribution of tufa and travertine across the discharge apron calcite and biotic growth rates were controlled largely by flow velocity across the apron which in turn was controlled by topography and regular fluctuations in spring water discharge volume during times of high spring discharge slow sheet flow over the proximal part of the apron promoted stromatolite growth whereas fast turbulent flow on the distal part of the apron induced rapid feather dendrite formation during times of low spring discharge quiescent shallow evaporative pools conducive to radiating dendrite formation formed on the proximal part of the apron whereas slow flow on the distal part promoted stromatolite growth facies with high calcite supersaturation experienced rapid abiotic dendrite growth that precluded most biotic growth

ordovician oxygen isotopes and paleotemperatures abstract valid marine 18o proxies have been defined from three ordovician units and with previously estimated sea water 18o values we have calculated paleotemperatures for low latitude settings during a greenhouse climatic era valid marine proxies include marine equant bladed and translucent fibrous calcite these cements are interpreted to be valid marine proxies based on cathodoluminescence minor element content abundance of microdolomite and stable isotopic both altered marine and non marine calcite phases values valid marine proxies from the chickamauga alabama holston tennessee and kullsberg sweden formations have an overall range of 18o values in each unit that is confined to within 1 unlike altered marine cements which exhibit significantly wider ranges of 18o values we suggest a likely non glacial ordovician sea water value of 2 1 smow from which paleotemperatures can be calculated calculated paleotemperatures are broadly consistent with crowley and baum s 1995 late ordovician paleoclimatic model

deccan volcanism at the cretaceous tertiary boundary the accuracy with which one can claim that deccan trap volcanism occurred at the cretaceous tertiary boundary ktb over a very short time interval is of key importance in deciding whether a volcanic origin of the ktb events should be taken seriously in the two years since paleomagnetic paleontological and geodynamic evidence was published further data have become available and the case now appears to be well constrained the ar 40 ar 39 results from six labs have yielded some 24 reliable plateau ages that narrow the age range to 65 to 69 ma moreover it appears that a significant part of this range results from inter lab spread and possible minor alteration paleontology demonstrates that volcanism started in the maestrichtian more precisely in the a mayaroensis zone paleomagnetism shows that volcanism spanned only 3 chrons and only one correlation remains possible that of the main central reversed chron with 29r therefore whereas ar 40 ar 39 is able only to restrict the duration of volcanism to some 4 ma paleomagnetism restricts it to 0 5 ma using some geochemical indicators such as c 13 as proxy it is suggested that volcanism actually consists of a few shorter events of unequal magnitude extrusion rates may be as high as 100 cu km yr and fissure lengths as long as several 100 km such a scenario appears to be at least as successful as others in accounting for most anomalies observed at the ktb particularly important are iridium and other platinum group elements pge profiles sr 87 sr 86 c 13 0 18 other exotic geochemical signatures spherules soot shocked minerals selective and stepwise extinctions the environmental impact of co2 possibly released during explosive phases of volcanism and so2 released during effusive phases and the ability of volcanism to ensure worldwide distribution of ktb products are now all addressed in conclusion the case for a causal link between internal hotspot activity birth of the reunion hotspot itself as the deccan and ktb events appears to rest on an increasingly stronger basis