pronounced zonal heterogeneity in eocene southern high latitude sea surface temperatures paleoclimate studies suggest that increased global warmth during the eocene epoch was greatly amplified at high latitudes a state that climate models cannot fully reproduce however proxy estimates of eocene near antarctic sea surface temperatures ssts have produced widely divergent results at similar latitudes with ssts above 20 c in the southwest pacific contrasting with ssts between 5 and 15 c in the south atlantic validation of this zonal temperature difference has been impeded by uncertainties inherent to the individual paleotemperature proxies applied at these sites here we present multiproxy data from seymour island near the antarctic peninsula that provides well constrained evidence for annual ssts of 10 17 c 1 sd during the middle and late eocene comparison of the same paleotemperature proxy at seymour island and at the east tasman plateau indicate the presence of a large and consistent middle to late eocene sst gradient of 7 c between these two sites located at similar paleolatitudes intermediate complexity climate model simulations suggest that enhanced oceanic heat transport in the south pacific driven by deep water formation in the ross sea was largely responsible for the observed sst gradient these results indicate that very warm ssts in excess of 18 c did not extend uniformly across the eocene southern high latitudes and suggest that thermohaline circulation may partially control the distribution of high latitude ocean temperatures in greenhouse climates the pronounced zonal sst heterogeneity evident in the eocene cautions against inferring past meridional temperature gradients using spatially limited data within given latitudinal bands

multiple fluid flow events and the formation of saddle dolomite case studies from the middle devonian of the western canada sedimentary basin abstract in western canada sedimentary basin wcsb large scale and focused fluid flow that caused hydrothermal dolomitization have been suggested with different timing and intensity in this study we conducted a petrographic and geochemical comparison between the middle devonian sulphur point and slave point carbonates from northwestern alberta the results demonstrate the presence of both an early fluid flow event associated with the late devonian to mississippian antler orogeny as well as a later event coincident with the late cretaceous to early tertiary laramide orogeny early fluid flow event is characterized by high salinity fluids and high temperatures and oxygen isotopic values of marine or slightly enriched values as demonstrated in saddle dolomite from the slave point formation in contrast later fluids that caused the precipitation of saddle dolomite in the sulphur point formation are characterized by having slightly saline values comparable homogenization temperatures but more enriched 18 o values and slightly depleted 13 c signatures geochemical data indicate that this later hydrothermal fluid was mixture of middle devonian brines and radiogenic basement fluids

the origin and evolution of canadian shield brines evaporation or freezing of seawater new lithium isotope and geochemical evidence from the slave craton abstract new chemical and isotopic data for deep seated calcium chloride brine from the miramar con gold mine yellowknife n w t strongly suggest that the brine salinity is of marine origin diagnostic marine properties include uniformly elevated br cl ratios typical of seawater concentrated beyond halite saturation and li br ratios 0 0254 0 0325 and 6 li compositions 32 1 to 36 3 similar to seawater 32 3 the mean 6 li for all mine water samples of 35 1 may reflect minor uptake of li by secondary minerals this interpretation is supported by analyses of altered metabasalt from fault zones which is enriched in li but depleted in 6 li 14 7 to 15 6 relative to the unaltered metabasalt 5 4 the mechanism responsible for concentrating the hypersaline brine end member is not unequivocal as evidence exists to support both evaporative and cryogenic processes on the one hand the devonian sedimentary record in the great slave lake region in conjunction with yellowknife brine isotopic compositions 2 h and 34 s so 4 that are similar to various devonian fluids support an evaporative origin on the other hand the na cl br cl relationship in the brine strongly suggests a cryogenic mechanism regardless of the concentrative mechanism the chemical data indicate that the yellowknife parent brine was concentrated 28 to 30 fold relative to seawater the extreme depletion of mg and enrichment of ca in the brines accompanied by sr ca ratios similar to that of seawater are accounted for by dolomitization of an aragonite rich marine sediment by the brine before infiltration into the crystalline basement rocks subsequent alteration of silicate minerals in the shield added additional ca and sr to the brine as indicated by their radiogenic 87 sr 86 sr ratios up to 0 7147 based on mineral balance calculations the major mineral products of the cryogenic and evaporitic concentration and evolution paths are significantly different the cryogenic evolution results in some 15 mirabilite 60 hydrohalite and 18 dolomite whereas the major minerals formed from the evaporitic evolutionary sequence are 36 halite 8 gypsum 17 dolomite and 30 albite the great similarity between the calcium chloride brine from yellowknife and other such canadian shield brines indicates that they may share a common marine origin

eocene cooling linked to early flow across the tasmanian gateway the warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the early eocene climatic optimum 52 50 ma the early eocene climatic optimum terminated with a long term cooling trend that culminated in continental scale glaciation of antarctica from 34 ma onward whereas early studies attributed the eocene transition from greenhouse to icehouse climates to the tectonic opening of southern ocean gateways more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations e g co2 however the scarcity of field data has prevented empirical evaluation of these hypotheses we present marine microfossil and organic geochemical records spanning the early to middle eocene transition from the wilkes land margin east antarctica dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound antarctic counter current began 49 50 ma through a southern opening of the tasmanian gateway this early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling 2 4 c evidenced by biomarker and pollen based paleothermometry we interpret that the westbound flowing current flow across the tasmanian gateway resulted in cooling of antarctic surface waters and coasts which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes although atmospheric co2 forcing alone would provide a more uniform middle eocene cooling the opening of the tasmanian gateway better explains southern ocean surface water and global deep ocean cooling in the apparent absence of sub equatorial cooling

fluid compartmentalization of devonian and mississippian dolostones western canada sedimentary basin petrologic and geochemical evidence from fracture mineralization1 integrated petrographic geochemical and fluid inclusion study of fracture mineralization and associated host rock in selected mississippian and devonian carbonates extending from southeastern alb

early paleogene evolution of terrestrial climate in the sw pacific southern new zealand 1 we present a long term record of terrestrial climate change for the early paleogene of the southern hemisphere that complements previously reported marine temperature records using the mbt cbt proxy based on the distribution of soil bacterial glycerol dialkyl glycerol tetraether lipids we reconstructed mean annual air temperature mat from the middle paleocene to middle eocene 62 42 ma for southern new zealand this record is consistent with temperature estimates derived from leaf fossils and palynology as well as previously published mbt cbt records which provides confidence in absolute temperature estimates our record indicates that through this interval temperatures were typically 5 c warmer than those of today at such latitudes with more pronounced warming during the early eocene climate optimum eeco 50 ma when mat was 20 c moreover the eeco mats are similar to those determined for antarctica with a weak high latitude terrestrial temperature gradient 5 c developing by the middle eocene we also document a short lived cooling episode in the early late paleocene when mat was comparable to present this record corroborates the trends documented by sea surface temperature sst proxies although absolute ssts are up to 6 c warmer than mats although the high calibration error of the mbt cbt proxy dictates caution the good match between our mat results and modeled temperatures supports the suggestion that sst records suffer from a warm summer bias particularly during times of peak warming

correlating paleomagnetic geochemical and petrographic evidence to date diagenetic and fluid flow events in the mississippian turner valley formation moose field alberta canada abstract petrographic geochemical and paleomagnetic analyses of the mississippian turner valley formation provide constraints on diagenesis and fluid flow events in the western canada sedimentary basin paleomagnetic plugs and companion geochemical samples were taken from two drillcores with fullbore microimage log orientations dolomite from both wells yielded two magnetization directions the low temperature low coercivity direction is a drilling induced remanence rather than a viscous remanent magnetization the high temperature high coercivity remanence direction is cretaceous and there is no sign of a primary mississippian direction geochemical analyses of matrix dolomite yield 18o values ranging from 0 65 to 3 34 vpdb standard and 13c values ranging from 1 77 to 3 05 vpdb the least depleted samples have stable isotope values consistent with or only slightly depleted from postulated mississippian dolomite values the remaining sample values exhibit a negative covariant trend consistent with either mixing with another diagenetic fluid or recrystallization during burial petrographic analysis reveals the presence of a recrystallization event that caused zoning and a gradual increase size of the dolomite crystals this event is thought to have caused both the cretaceous paleomagnetic remanence and the altered geochemical values the minor enrichment in sr radiogenic isotopes relative to coeval seawater values suggests that both an extrabasinal source for any fluid and large scale fluid flow are unlikely the results also indicate that magnetic remanences are very sensitive to visually minor changes in carbonate recrystallization from heat or pressure so that great care must be taken in correlating paleomagnetic and geochemical data

paleohydrogeology of the canadian rockies and origins of brines pb zn deposits and dolomitization in the western canada sedimentary basin results of stable isotopic and fluid inclusion studies of cambrian carbonate units in the southern canadian rockies indicate that during the late devonian or early mississippian a warm brine migrated from miogeoclinal shales in the western part of the western canada sedimentary basin into the eastern carbonate sequences this fluid had a temperature of 150 25 c salinity values of 20 to 25 equivalent wt nacl and isotopic values of 18 o 7 to 0 13 c 1 2 d 70 19 and 87 sr 86 sr 0 710 the fluids formed large bodies of coarse sparry dolomite as well as pb zn magnesite and talc mineralizations in the cambrian units it is probable that this event was also responsible for the development of pb zn mineralization specifically pine point in the devonian units as well as a component of the present day basinal brines in the basin

the gas bearing devonian presqu ile dolomite of the cordova embayment region of british columbia canada dolomitization and the stratigraphic template white dolospar of the presqu ile dolomite forms the reservoir for many gas fields of northeastern british columbia within the keg river sulphur point and slave point formations along the shelf margin of the cordova embayment the embayment fill succession of the organic rich klua shale the otter park shale and marlstones equivalent to the sulphur point and slave point formations are aquicludes that blocked the upward and lateral flow of dolomitizing brines presqu ile dolomitization along the slave point shelf edge is interrupted in places where the klua shale extends shelfward underneath the slave point formation the watt mountain shale was also a regional aquiclude that prevented upward circulation of dolomitizing fluids in areas behind the slave point shelf edge flow of dolomitizing nacl cacl2 mgcl2 h2o brine solutions began in the shallow subsurface and precipitated dolomite cements type 1 at temperatures less than 50 degreesc possibly even during slave point deposition as northwestward directed shallow subsurface brine reflux from the elk point basin began this was followed by upward directed subsurface convective flow of nacl cacl2 mgcl2 h2o and nacl mgcl2 h2o brines and precipitation of dolomite cements at temperatures of about 130 degreesc during the late devonian carboniferous lower salinity brines that precipitated calcite cements and some dolomite type 2 may have interacted with connate fluids of marine origin or less likely with meteoric fluids modeling of organic maturation indicates that the muskwa shales above the slave point formation passed through the oil generation window in the permian and the onset of dry gas generation in the middle mesozoic postdolomitization calcite cements precipitated during these times contain abundant liquid hydrocarbon filled and methane filled inclusions high temperatures of close to 200 degreesc experienced by slave point strata in the mesozoic caused stretching but no leakage or refilling of fluid inclusions in all dolomite cements

new evidence for syntectonic fluid migration across the hinterland foreland transition of the canadian cordillera 1 oxygen isotope data from syntectonic veins thrust faults and wall rocks suggest that fluids infiltrated the western ranges of the rocky mountain foreland from deeper rocks of the dogtooth range during mesozoic contraction this signifies the first such evidence for kilometer scale fluid migration at the hinterland foreland transition of the canadian cordillera fluid infiltration resulted in isotopic depletion in wall rocks and isotopic disequilibrium between veins fluid and their host rocks downstream of a lithologic structural and isotopic shift between predominantly siliciclastic dogtooth range and calcareous western ranges sequences the shift corresponds with an average 18o that is 3 0 higher in the western ranges in the dogtooth range atypically low carbonate values 15 6 0 8 vsmow and the consistency with which vein signatures approach the average bulk rock 18o of individual outcrops indicate fluid buffering by a siliciclastic reservoir and outcrop scale 10 100 m fluid circulation in contrast rocks and veins in the western ranges exhibit a gradational increase in 18o that extends 14 km eastward and up section from the isotopic shift and possess values that are below or at the low end of typical carbonate compositions 16 2 20 9 vsmow furthermore veins systematically exhibit lower oxygen values than their host rocks this implies that the fluids that entered the western ranges were in modest disequilibrium with the rocks through which they flowed we use a one dimensional reactive transport model to infer that rocks in the western ranges experienced a time integrated fluid flux of 1 1 105 mol h2o cm 2 2 4 106 cm3 cm 2 and sluggish reaction kinetics during the flow event

fault controlled dolomitization at swan hills simonette oil field devonian deep basin west central alberta canada the partly dolomitized swan hills formation middle upper devonian in the simonette oil field of west central alberta underwent a complex diagenetic history which occurred in environments ranging from near surface to deep 2500 m burial five petrographically and geochemically distinct dolomites that include both cementing and replacive varieties post date stylolites in limestones depths 500 m these include early planar varieties and later saddle dolomites fluid inclusion data from saddle dolomite cements th 137 190 c suggest that some precipitated at burial temperatures higher than the temperatures indicated by reflectance data tpeak 160 c thus at least some dolomitizing fluids were hydrothermal fluorescence microscopy identified three populations of primary hydrocarbon bearing fluid inclusions and confirms that saddle dolomitization overlapped with upper cretaceous oil migration the source of early dolomitizing fluids probably was devonian or mississippian seawater that was mixed with a more 87sr rich fluid fabric destructive and fabric preserving dolostones are over 35 m thick in the swan hills buildup and basal platform adjacent to faults thinning to less than 10 cm thick in the buildup between 5 and 8 km away from the faults this plume like geometry suggests that early and late dolomitization events were fault controlled late diagenetic fluids were in part derived from the crystalline basement or palaeozoic siliciclastic aquifers based on 87sr 86sr values up to 0 7370 from saddle dolomite calcite and sphalerite cements and 206pb 204pb of 22 86 from galena samples flow of dolomitizing and mineralizing fluids occurred during burial greater than 500 m both vertically along reactivated faults and laterally in the buildup along units that retained primary and or secondary porosity

late cretaceous seasonal ocean variability from the arctic palaeoclimate records for the arctic ocean and its environs in the late cretaceous greenhouse era 65 99 million years ago are sparse using electron microscope techniques applied to cores of shallow buried cretaceous laminated sediments from the alpha ridge of the arctic ocean davies et al have obtained a seasonally resolved sediment record from the cretaceous that permits a reconstruction of the annual cycle of marine productivity and flux to the sediment they find that the period was characterized by seasonal diatom productivity in a stratified ocean with possible winter sea ice cover although the modern arctic ocean is regarded as a barometer of global change and an amplifier of global warming little is known about its state in the greenhouse period of the late cretaceous epoch 65 99 million years ago here a seasonally resolved cretaceous sedimentary record from the alpha ridge of the arctic ocean is presented evidence suggests seasonal diatom productivity in a stratified ocean with possible winter sea ice cover the modern arctic ocean is regarded as a barometer of global change and amplifier of global warming1 and therefore records of past arctic change are critical for palaeoclimate reconstruction little is known of the state of the arctic ocean in the greenhouse period of the late cretaceous epoch 65 99 million years ago yet records from such times may yield important clues to arctic ocean behaviour in near future warmer climates here we present a seasonally resolved cretaceous sedimentary record from the alpha ridge of the arctic ocean this palaeo sediment trap provides new insight into the workings of the cretaceous marine biological carbon pump seasonal primary production was dominated by diatom algae but was not related to upwelling as was previously hypothesized2 rather production occurred within a stratified water column involving specially adapted species in blooms resembling those of the modern north pacific subtropical gyre3 or those indicated for the mediterranean sapropels4 with increased co2 levels and warming currently driving increased stratification in the global ocean5 this style of production that is adapted to stratification may become more widespread our evidence for seasonal diatom production and flux testify to an ice free summer but thin accumulations of terrigenous sediment within the diatom ooze are consistent with the presence of intermittent sea ice in the winter supporting a wide body of evidence for low temperatures in the late cretaceous arctic ocean6 7 8 rather than recent suggestions of a 15 c mean annual temperature at this time9

conflicting isotopic and biotic evidence for tropical sea surface temperatures during the tertiary abstract the biotic evidence from a varied group of shallow water organisms including mangroves zooxanthellate corals mainly reefal and larger foraminifera suggests that sea surface temperatures at low latitudes during the tertiary from at least the early eocene to the middle miocene were subtropical to tropical in nature and similar to temperatures prevailing at low latitudes at the present day 20 28 c in a recent paper shackleton 1984 the suggestion is made on the basis of oxygen isotope studies of foraminiferal shells that low latitude sea surface temperatures during the palaeogene and much of the neogene were invariably lower than those in similar regions today with a stable temperature of around 18 c this paper discusses the conflicting evidence for sea surface temperatures obtained from palaeontological and isotopic sources and suggests that palaeotemperatures derived from some isotopic studies are too low to account for the distribution and diversity of many tertiary tropical and subtropical biotas

evolution of fluid compartmentalization in a detachment fold complex oxygen carbon and strontium isotope variations in vein filling calcite and quartz cements and their host rocks are used to elucidate the origin spatial and temporal evolution and migration pathways of fluids in the detachment nuncios fold complex northeastern mexico the folded mesozoic sedimentary sequence contains two regional paleohydrostratigraphic units separated by a unit of low permeability two main generations of cements are present in both paleohydrostratigraphic units distinct differences exist between 18 o 13 c 87 sr 86 sr and fluid inclusion temperatures of early vein filling cements in the lower and the upper units these differences together with a strong correspondence between early cement and host rock 18 o and 13 c values suggest that early diagenetic fluids were compartmentalized between the two units late vein filling cements have isotopic compositions and fluid inclusion temperatures that converge to similar values indicating a change to open fluid flow between the lower and upper units we hypothesize that the fluid history of the nuncios fold complex evolved in two main stages 1 burial diagenesis and early folding during which fluids were confined within individual units and 2 late stage folding during which increased deformation associated with fold tightening caused the expulsion of fluid from the lower unit into the upper unit

carbonate systems along nutrient and temperature gradients some sedimentological and geochemical constraints research over the past several decades has clearly demonstrated that changes in the ocean environment have had major impacts on carbonate systems changes in climate ocean circulation and seafloor spreading rates have influenced temperature and seawater chemistry including carbonate saturation state and nutrient availability and thereby have determined boundary conditions for the biota that form carbonate platforms in turn the biota determine accumulation rates and facies zonations thus controlling platform geometry and facies dynamics in the first section of this paper we examine how nutrient availability influences carbonate facies associations we first discuss the role of temperature and nutrient gradients in the modern ocean and their influence on biotic associations then we discuss how carbonate sedimentation can be characterized along nutrient gradients in the second section we review proxies currently used to reconstruct paleoproductivity in open ocean environments and discuss their applicability to neritic carbonate systems we highlight the variety of existing proxies and their limitations and suggest that multiple lines of evidence are needed for valid interpretations our short review discusses sedimentological biogenic and geochemical proxies that can be used to reconstruct past nutrient fluxes and to constrain paleoceanographic controls over the distribution of carbonate associations however it also reveals that more data and case studies are needed that integrate shallow and deep water carbonate sequences and elucidate the links between temperature vs nutrient supplies changes and facies in ancient carbonate sequences

late paleocene early eocene tethyan carbonate platform evolution a response to long and short term paleoclimatic change abstract the early paleogene experienced the most pronounced long term warming trend of the cenozoic superimposed by transient warming events such as the paleocene eocene thermal maximum petm the consequences of climatic perturbations and associated changes on the evolution of carbonate platforms are relatively unexplored today modern carbonate platforms especially coral reefs are highly sensitive to environmental and climatic change which raises the question how sub tropical reef systems of the early paleogene reacted to gradual and sudden global warming eutrophication of shelf areas enhanced co 2 levels in an ocean with low mg ca ratios the answer to this question may help to investigate the fate of modern coral reef systems in times of global warming and rising co 2 levels here we present a synthesis of tethyan carbonate platform evolution in the early paleogene 59 55 ma concentrating on coral reefs and larger foraminifera two important organism groups during this time interval we discuss and evaluate the importance of the intrinsic and extrinsic factors leading to the dissimilar evolution of both groups during the early paleogene detailed analyses of two carbonate platform areas at low egypt and middle spain paleolatitudes and comparison with faunal patterns of coeval platforms retrieved from the literature led to the distinction of three evolutionary stages in the late paleocene to early eocene tethys stage i late paleocene coralgal dominated platforms at low to middle paleolatitudes stage ii a transitional latest paleocene platform stage with coralgal reefs dominating at middle paleolatitudes and larger foraminifera dominated miscellanea ranikothalia assilina platforms at low paleolatitudes and stage iii early eocene larger foraminifera dominated alveolina orbitolites nummulites platforms at low to middle paleolatitudes the onset of the latter prominent larger foraminifera dominated platform correlates with the paleocene eocene thermal maximum the causes for the change from coral dominated platforms to larger foraminifera dominated platforms are multilayered the decline of coralgal reefs in low latitudes during platform stage ii is related to overall warming leading to sea surface temperatures in the tropics beyond the maximum temperature range of corals the overall low occurrence of coral reefs in the paleogene might be related to the presence of a calcite sea at the same time larger foraminifera started to flourish after their near extinction at the cretaceous paleogene boundary the demise of coralgal reefs at all studied paleolatitudes in platform stage iii can be founded on the effects of the petm resulting in short term warming eutrophic conditions on the shelves and acidification of the oceans hampering the growth of aragonitic corals while calcitic larger foraminifera flourished in the absence of other successful carbonate producing organisms larger foraminifera were able to take over the role as the dominant carbonate platform inhabitant leading to a stepwise tethyan platform stage evolution around the paleocene eocene boundary this szenario might be also effective for threatened coral reef sites

constraints on the vital effect in coccolithophore and dinoflagellate calcite by oxygen isotopic modification of seawater in this study we show that there are independent controls of 18o 16o and 13c 12c fractionation in coccolithophore and dinoflagellate calcite due to the contrasting kinetics of each isotope system we demonstrate that the direction and magnitude of the oxygen isotope fractionation with respect to equilibrium is related to the balance between calcification rate and the replenishment of the internal pool of dissolved inorganic carbon dic as such in fast growing cells such as those of emiliania huxleyi and gephyrocapsa oceanica forming the so called heavy group calcification of the internal carbon pool occurs faster than complete isotopic re adjustment of the internal dic pool with h2o molecules hence coccoliths reflect the heavy oxygen isotope signature of the co2 overprinting the whole dic pool conversely in large and slow growing cells such as coccolithus pelagicus ssp braarudii complete re equilibration is achieved due to limited influx of co2 leading to coccoliths that are precipitated in conditions close to isotopic equilibrium equilibrium group species exhibiting the most negative oxygen isotope composition such as calcidiscus leptoporus light group precipitate coccolith under increased ph in the coccolith vesicle as previously documented by the carbonate ion effect we suggest that for the carbon isotope system any observed deviation from isotopic equilibrium is only apparent as the carbon isotopic composition in coccolith calcite is controlled by a rayleigh fractionation originating from preferential incorporation of 12c into organic matter therefore species with low pic poc ratios as e huxleyi and g oceanica are shifted towards positive carbon isotope values as a result of predominant carbon fixation into the organic matter by contrast cells with higher pic poc as c braarudii and c leptoporus maintain to some extent the original negative isotopic composition of the co2 the calcareous dinoflagellate thoracosphaera heimii exhibits different behaviour for both isotopic systems in particular with respect to its very negative carbon isotope composition owing to coeval intra and extracellular biomineralisation in this group in this study we also investigate the sensitivity of 18o 16o fractionation to varying ambient oxygen isotope composition of the medium for inorganic coccolithophore and dinoflagellate calcite precipitated under controlled laboratory conditions the varying responses of different taxa to increased oxygen isotope composition of the growth medium may point to a potential bias in sea surface temperature reconstructions that are based on the oxygen isotopic compositions of sedimentary calcite especially during times of changing seawater oxygen isotopic composition overall this study represents an important step towards establishing a mechanistic understanding of the vital effect in coccolith and dinoflagellate calcite and provides valuable information for interpreting the geochemistry of the calcareous nannofossils in the sedimentary record at both monospecific and interspecies levels

shale basins sulfur deficient ore brines and the formation of exhalative base metal deposits abstract the massive sulfide deposits of the iberian pyrite belt are interbedded with felsic volcanic rocks and shale and underlain by several thousand meters of siliciclastic sedimentary rocks known as the pq group isotope geochemistry and regional geology are both consistent with equilibration of the ore forming fluids with the pq group prior to ore deposition near the former seafloor the average cu zn pb ratio of the pq group rocks ca 26 55 19 is similar to the weighted average of all the massive sulfide orebodies combined ca 25 52 23 the genetic relationship between massive sulfide deposits and a siliciclastic sedimentary metal source is explained here by a thermodynamic model proposing that mildly reducing redox conditions imposed by equilibration with the sedimentary rocks are most critical for the formation of an effective ore forming fluid relatively metal rich but organic poor pyrite bearing shale undergoing dewatering of saline pore fluids is an effective source for the generation of sulfur deficient but relatively iron and base metal rich brines thus we propose that the giant deposits of the iberian pyrite belt owe their existence not to exceptionally metal enriched e g magmatic fluids but to the existence of a fairly ordinary but large metal source in reactive siliciclastic sediments combined with an underlying igneous heat source and a particularly efficient mechanism of sulfide precipitation by mixing with h 2 s rich fluids at or near the seafloor essentially similar mineral equilibria are imposed when saline fluids are buffered by typical continental basement rocks leaching of retrograde minerals and possibly residual salts from their magmatic or metamorphic prehistory is expected to generate similar variably metal rich but relatively sulfide deficient fluids thus the existence of mildly reducing rocks can be the dominant chemical control in the source of fluids generating many volcanogenic irish type or sedex deposits many of which are known to precipitate their metal load in response to biogenic sulfide addition at the ore deposition site

evaluating new fault controlled hydrothermal dolomitization models insights from the cambrian dolomite western canadian sedimentary basin fault controlled hydrothermal dolomitisation in tectonically complex basins can occur at any depth and from different fluid compositions including deep seated crustal or basinal brines nevertheless many studies have failed to identify the actual source of these fluids resulting in a gap in our knowledge on the likely source of magnesium of hydrothermal dolomitisation with development of new concepts in hydrothermal dolomitisation the study aims in particular to test the hypothesis that dolomitising fluids were sourced from either seawater ultramafic carbonation or a mixture between the two by utilising the cambrian mount whyte formation as an example here the large scale dolostone bodies are fabric destructive with a range of crystal fabrics including euhedral replacement rd1 and anhedral replacement rd2 since dolomite is cross cut by low amplitude stylolites dolomitisation is interpreted to have occurred shortly after deposition at a very shallow depth 1 km at this time there would have been sufficient porosity in the mudstones for extensive dolomitisation to occur and the necessary high heat flows and faulting associated with cambrian rifting to transfer hot brines into the near surface while the 18owater and 87sr 86sr ratios values of rd1 are comparable with cambrian seawater rd2 shows higher values in both parameters therefore although aspects of the fluid geochemistry are consistent with dolomitisation from seawater very high fluid temperature and salinity could be suggestive of mixing with another hydrothermal fluid the very hot temperature positive eu anomaly enriched metal concentrations and cogenetic relation with quartz could indicate that hot brines were at least partially sourced from ultramafic rocks potentially as a result of interaction between the underlying proterozoic serpentinites and co2 rich fluids this study highlights that large scale hydrothermal dolostone bodies can form at shallow burial depths via mixing during fluid pulses providing a potential explanation for the mass balance problem often associated with their genesis

equable climates during earth history eocene and cretaceous climate model experiments demonstrate that regardless of conditions of warm polar oceans differences in pole to equator surface temperature gradient or topography above freezing surface temperatures in winter for continental interiors at middle to high latitudes cannot be maintained continental interiors will have cold winter temperatures even during globally warm periods unless currently unrecognized forcing factors influenced past climates if model simulations of eocene and cretaceous climates are accurate the term equable as it applies to paleoclimate should be reconsidered

warm not super hot temperatures in the early eocene subtropics the early eocene ca 55 48 ma encompasses one of the warmest intervals of the past 65 m y and is characterized by an unusually low equator to pole thermal gradient recent proxy studies suggest temperatures well in excess of 30 c even at high latitudes but confl icting interpretations derived from different types of data leave considerable uncertainty about actual early eocene temperatures a robust comparison among new paleotemperature proxies may provide insight into possible biases in their temperature estimates and additional detail on the spatial distribution of temperatures will further resolve the early eocene meridional temperature gradient we use a suite of paleotemperature proxies based on the chemistry of bivalve shell carbonate and associated sedimentary organic matter from the united states gulf coastal plain to constrain climate at a subtropical site during this key interval of earth history oxygen isotope and clumped isotope analyses of shell carbonate and two tetraether lipid analyses of sedimentary organic carbon all yield temperatures of 27 c high resolution intraannual oxygen isotope data reveal a consistent large range of seasonal variation but clumped isotope data suggest that seasonality is due primarily to precipitation not to temperature these paleotemperature estimates are 2 3 c warmer than the northern gulf of mexico today and generally consistent with early eocene temperature estimates from other low and mid latitude locations but are signifi cantly cooler than contemporaneous estimates from high southern latitudes

zebra dolomitization as a result of focused fluid flow in the rocky mountains fold and thrust belt canada discordant zebra dolomite bodies occur locally in the middle cambrian cathedral and eldon formations of the main ranges of the canadian rocky mountains fold and thrust belt they are characterized by alternating dark grey a and white b bands forming an abba diagenetic cyclicity these bands developed parallel to both bedding and cleavage dark grey a bands consist of fine 300 m non planar crystalline impure dolomite the white b bands are composed of coarse up to several millimetres milky white pure saddle dolomites b1 which are often covered by pore lining zoned dolomite b2 the b phases often possess a saddle shaped morphology in contrast to the replacement origin of the a dolomite the zoned b2 dolomite rims are interpreted as a cement formed in open cavities the b1 dolomite is interpreted as the result of recrystallization with diagenetic leaching of non carbonate components all the zebra dolomites studied are nearly stoichiometric and are characterized by enriched na and depleted sr concentrations fe and mn concentrations in these dolomites differ depending on the sample locality fluid inclusion data indicate that the dolomites formed from relatively hot th 130 200 c saline 20 23 wt cacl2 eq fluids a diagenetic high temperature origin is also supported by depleted 18o values 20 to 14 vpdb a contribution of 87sr enriched fluids is reflected in the 87sr 86sr values 0 7091 0 7123 zebra dolomite development is explained by focused fluid flow which exploited areas of structural weaknesses e g basin platform rim areas faults etc expulsion of hot basinal brines in a tectonically active regime generated overpressures which explains the development of secondary porosity during zebra dolomitization as well as the intra zebra fracturing at decimetre to micrometre scale

latitudinal temperature gradients and high latitude temperatures during the latest cretaceous congruence of geologic data and climate models a major challenge in paleoclimatology is disagreement between data and models for periods of warm climate data generally indicate equable conditions and reduced latitudinal temperature gradients while models generally produce colder conditions and steeper latitudinal gradients except when using very high co2 here we show congruence between temperature indicators and climate model output for the cool greenhouse interval of the latest cretaceous maastrichtian using a global database of terrestrial and marine indicators and fully coupled simulations with the community climate system model version 3 in these simulations we explore potential roles of greenhouse gases and properties of pre anthropogenic liquid clouds in creating warm conditions our model simulations successfully reproduce warm polar temperatures and the latitudinal temperature gradient without overheating the tropics best fits for mean annual temperature are simulations that use 6 preindustrial levels of atmospheric co2 or 2 preindustrial levels of atmospheric co2 and liquid cloud properties that may reflect pre anthropogenic levels of cloud condensation nuclei the siberian interior is problematic but this may relate to reconstructed elevation and the presence of lakes data and models together indicate tropical sea surface temperatures 5 c above modern an equator to pole temperature difference of 25 30 c and a mid latitudinal temperature gradient of 0 4 c per 1 latitude similar to the eocene modified liquid cloud properties allow successful simulation of maastrichtian climate at the relatively low levels of atmospheric co2 indicated by proxies and carbon cycle modeling this supports the suggestion that altered properties of liquid clouds may be an important mechanism of warming during past greenhouse intervals

geochemical and isotopic evidence for a genetic link between canadian shield brines dolomitization in the western canada sedimentary basin and devonian calcium chloridic seawater hypersaline brines of marine origin deep within fractured crystalline rocks of the canadian shield are characterized by calcium chloride compositions with relatively low concentrations of magnesi

simulation of the last glacial maximum climate over east asia with a regional climate model nested in a general circulation model abstract the east asian climate at the last glacial maximum lgm 21 000 years b p has been simulated using a regional climate model regcm2 nested in an atmospheric general circulation model of the institute of atmospheric physics iap agcm boundary conditions for the lgm simulations are consistent with the paleoclimate modelling intercomparison project pmip the results show that the nested regional model reproduces well the colder lgm climates over east asia the simulated annual mean surface temperature is 2 c 4 c colder than the present over the east asian continent with the coldest anomaly of about 8 c in the vicinity of current coastal areas where land is exposed due to lowering sea level at the lgm the precipitation changes are complex with general features of drier conditions over eastern china and its neighborhood and wetter conditions over western china than the present compared with the driving iap agcm the regcm2 results display better agreement with geological reconstructions over east asia especially in the mideastern and southern china the simulated warming changes by the iap agcm disagree with cooling in paleodata whereas the regcm2 reproduces realistic cooler lgm climate thus the current work proves that the high resolution regcm2 can capture additional regional details in the lgm simulation produced by improved representation of topography and physics

early paleogene temperature history of the southwest pacific ocean reconciling proxies and models we present a new multiproxy tex86 18o and mg ca marine temperature history for canterbury basin eastern new zealand that extends from middle paleocene to middle eocene including the paleocene eocene thermal maximum petm and early eocene climatic optimum eeco in light of concerns that proxy based sea surface temperature sst estimates are untenably warm for the southwest pacific during the eocene we review the assumptions that underlie the proxies and develop a preliminary paleo calibration for tex86 that is based on four multiproxy eocene records that represent an sst range of 15 34 c for the southwest pacific paleogene we show that tex86l exhibits the best fit with the eocene paleo calibration ssts derived from related proxies tex86h 1 tex86 exhibit a systematic warm bias that increases as tex86 values decrease a warm bias of 4 7 c where tex86 0 7 the tex86l proxy indicates that southwest pacific sst increased by 10 c from middle paleocene to early eocene with sst maxima of 26 28 c tropical during the petm and eeco and an sst minimum of 13 16 c cool warm temperate at the middle late paleocene transition 58 7 ma the base of the eeco is poorly defined in these records but the top is well defined in canterbury basin by a 2 5 c decrease in sst and bottom water temperature bwt in the latest early eocene 49 3 ma bwt falls from a maximum of 18 20 c in the eeco to 12 14 c in the middle eocene overall cooler temperatures are recorded in the mid waipara section which may reflect a deeper 500 m water depth and less neritic depositional setting compared with hampden and odp 1172 200 m water depth the high ssts and bwts inferred for the petm and eeco can be reconciled with eocene coupled climate model results if the proxies are biased towards seasonal maxima and the likely effect of a proto east australian current is taken into account

late laramide dolomite recrystallization of the husky rainbow a hydrocarbon devonian reservoir northwestern alberta canada paleomagnetic and geochemical evidence the rainbow field is in reefal carbonates of the middle devonian keg river formation in the western canada sedimentary basin alternating field and thermal step demagnetization was done on specimens from unoriented core from a vertical an inclined and a horizontal well core in the dolomite reservoir although they had no viscous remanent magnetization component to use for orientation most specimens had a well defined characteristic remanent magnetization chrm that resides in single to pseudosingle domain magnetite by rotating the mean chrm direction around its core axis a small circle can be generated for each core and the small circles intersect in the true chrm direction of d 168 i 73 5o 95 5 8 k 32 2 its paleopole of 164 e 83 n a95 10 defines a tertiary age with one sigma limits of middle eocene to middle miocene age petrographic examination defines four generations of dolomite matrix dolomite has 60 100 m diameter crystals that were later recrystallized to 200 400 m

geochemical constraints on the origin of the kicking horse and monarch mississippi valley type lead zinc ore deposits southeast british columbia canada two mississippi valley type mvt ore deposits kicking horse and monarch have been studied with the aim of comparing the ores at the two localities and to characterize the origin of the mineralizing fluids and the ore formation process es both deposits are hosted by the middle cambrian cathedral formation carbonate host rocks kicking horse on the north and monarch on the south flank of the kicking horse valley near field se british columbia the ore bodies are situated at the transition of western basinal to eastern shallow water strata of the paleo pacific passive margin succession in the cordilleran foreland province of the western canada sedimentary basin both deposits are related spatially to normal faults in both localities the ore minerals are dominated by pyrite sphalerite and galena dolomite minor quartz and calcite are also present in close association with the ores the salinity 21 30 wt nacl eq and homogenization temperatures 63 182 c measured in fluid inclusions in carbonate quartz and sphalerite lie within the typical range of mvt fluid conditions the good stoichiometry 50 53 mol caco3 low 18o values 21 to 14 vienna peedee belemnite and relatively high homogenization temperatures 95 c of the dolomite suggest the dolomites were formed under burial diagenesis the ore forming fluids probably interacted with siliciclastic units based on elevated li contents and 87sr 86sr ratios which are highest in the dolomite type after the main ore stage we propose that the ores formed from the mixing of a downward infiltrating sulfur bearing halite dissolution fluid with an upward migrating metal rich evaporated seawater fluid which had already undergone minor mixing with a dilute fluid

dolomite occurrence evolution and economically important associations abstract dolomite is not a simple mineral it can form as a primary precipitate a diagenetic replacement or as a hydrothermal metamorphic phase all that it requires is permeability a mechanism that facilitates fluid flow and a sufficient supply of magnesium dolomite can form in lakes on or beneath the shallow seafloor in zones of brine reflux and in early to late burial settings it may form from seawater from continental waters from the mixing of basinal brines the mixing of hypersaline brine with seawater or the mixing of seawater with meteoric water or via the cooling of basinal brines bacterial metabolism may aid the process of precipitation in settings where sulfate reducing species flourish and microbial action may control primary precipitation in some hypersaline anoxic lake settings dolomite is a metastable mineral early formed crystals can be replaced by later more stable phases with such replacements repeated a number of times during burial and metamorphism each new phase is formed by the partial or complete dissolution of an earlier dolomite this continual re equilibration during burial detracts from the ability of trace elements to indicate depositional conditions and resets the oxygen isotope signature of the dolomite at progressively higher temperatures because subsurface dolomite evolves via dissolution and reprecipitation a bed of dolomite can retain or create porosity and permeability to much greater burial depths and into higher temperature realms than a limestone counterpart dolomitization also creates new crystals with new rhomb growth following the dissolution of less stable precursors repetition of this process without complete pore cementation can generate intercrystalline porosity a number of times in the rock s burial history intercrystalline porosity is a highly interconnected style of porosity that gives dolomite reservoirs their good fluid storage capacity and efficient drainage the fact that many dolomite reservoirs formed via brine reflux means that they sit beneath an evaporite seal in both platform and basinwide evaporite settings the same association of evaporites sulfate source and entrained hydrocarbons means that burial conditions are also suitable for thermochemical sulfate reduction and the precipitation of base metals this tends to occur at higher temperatures 60 c 80 c and so the resulting dolomites tend to be ferroan and consist of saddle shaped crystals

the paint pots kootenay national park canada a natural acid spring analogue for mars1 2 the paint pots are a natural fe so4 acid spring system along the kicking horse rim a major geological feature that has controlled fluid flow and mineralization over geologic time the very low ph 3 and extremely high trace metal concentrations of the springs are anomalous and greatly exceed health limits zn 35 8 mg l pb 0 461 mg l as 82 7 ppb sulphur isotopes 34s and 18o in sulphate equal to 11 4 and 12 1 respectively are consistent with sulphide oxidation mass balance calculations indicate that the springs must have derived their acidity and metal content from natural weathering of a pyrite rich ore deposit in the vicinity several ore deposit types occur along the kicking horse rim with the mississippi valley type mvt style being the most consistent with the source of the spring waters at the spring outlet fe rich waters oxidize forming large cone features of fe o precipitates predominantly goethite a diverse microbial community has been identified in the site that is di

solute chemistry of inclusion fluids from sparry dolomites and magnesites in middle cambrian carbonate rocks of the southern canadian rocky mountains middle cambrian carbonate rocks of the southern canadian rocky mountains are host to widespread units of white sparry hydrothermal replacement and open space filling dolomite contained within the dolomites are occurrences of talc and mississippi valley type pb zn the former kicking horse and monarch mines mineralization and economic concentrations of magnesite mount brussilof mine results of studies of solute chemistry of saline 18 25 equivalent wt nacl inclusion fluids reveal distinctly low na br 55 220 and cl br 95 340 values these values indicate that the brines which formed the dolomite originated from seawater that had deposited large amounts of halite in an evaporitic environment low i br ratios for the dolomite magnesite inclusion fluids are consistent with their derivation from seawater and contrast sharply with the high i br ratios of laramide age fluids which formed veins throughout the rocky mountains variations in f br ratios between texturally early and late magnesites i

changing atmospheric co2 concentration was the primary driver of early cenozoic climate the early eocene climate optimum eeco which occurred about 51 to 53 million years ago was the warmest interval of the past 65 million years with mean annual surface air temperature over ten degrees celsius warmer than during the pre industrial period subsequent global cooling in the middle and late eocene epoch especially at high latitudes eventually led to continental ice sheet development in antarctica in the early oligocene epoch about 33 6 million years ago however existing estimates place atmospheric carbon dioxide co2 levels during the eocene at 500 3 000 parts per million and in the absence of tighter constraints carbon climate interactions over this interval remain uncertain here we use recent analytical and methodological developments to generate a new high fidelity record of co2 concentrations using the boron isotope 11 b composition of well preserved planktonic foraminifera from the tanzania drilling project revising previous estimates although species level uncertainties make absolute values difficult to constrain co2 concentrations during the eeco were around 1 400 parts per million the relative decline in co2 concentration through the eocene is more robustly constrained at about fifty per cent with a further decline into the oligocene provided the latitudinal dependency of sea surface temperature change for a given climate forcing in the eocene was similar to that of the late quaternary period this co2 decline was sufficient to drive the well documented high and low latitude cooling that occurred through the eocene once the change in global temperature between the pre industrial period and the eocene caused by the action of all known slow feedbacks apart from those associated with the carbon cycle is removed both the eeco and the late eocene exhibit an equilibrium climate sensitivity relative to the pre industrial period of 2 1 to 4 6 degrees celsius per co2 doubling 66 per cent confidence which is similar to the canonical range 1 5 to 4 5 degrees celsius indicating that a large fraction of the warmth of the early eocene greenhouse was driven by increased co2 concentrations and that climate sensitivity was relatively constant throughout this period

ecology of extant nummulitids and other larger benthic foraminifera applications in palaeoenvironmental analysis abstract larger benthic foraminifera lbf are important contributors to modern and ancient tropical shallow marine sediments over the past 30 years a substantial body of literature has built up on the ecology of modern lbf especially in terms of their environmentally sensitive depth distribution reproductive strategy and morphology and the symbiotic relationship between many larger foraminifera and photosynthetic algae over the same period the extinct genus nummulites which is abundant in eocene sediments of southern europe north africa and the arabian peninsula has increasingly been studied principally because significant volumes of hydrocarbons have been discovered reservoired within nummulitic limestones offshore tunisia and libya the modern ecological studies of lbf provide a powerful tool with which to develop palaeoecological models for fossil nummulites and other symbiont bearing larger foraminifera in the rock record

benthic carbonate factories of the phanerozoic marine carbonate precipitation occurs in three basic modes abiotic or quasi abiotic biotically induced and biotically controlled on a geologic scale these precipitation modes combine to form three carbonate production systems or factories in the benthic environment 1 tropical shallow water factory dominated by biotically controlled mainly photo autotrophic and abiotic precipitates 2 cool water factory dominated by biotically controlled mainly heterotrophic precipitates and 3 mud mound factory dominated by biotically induced mainly microbial and abiotic precipitates sediment accumulations of the factories differ in composition geometry and facies patterns and some of these differences appear prominently in seismic data thus facilitating subsurface prediction the characteristic accumulation of the tropical factory is the flat topped often reef rimmed platform in cool water systems reefs in high energy settings are scarce and hydrodynamic influence dominates producing seaward sloping shelves and deep water sediment drifts often armored by skeletal framework the typical accumulation of the mud mound factory is groups of mounds in deeper water where the mud mound factory expands into shallow water it forms rimmed platforms similar to the tropical factory the tropical factory is most productive the mud mound factory reaches 80 90 and the cool water factory 20 30 of the tropical growth rate the three factories represent end members connected by transitions in space transitions in time are linked to biotic evolution

geochemistry of syntectonic crustal fluid regimes along the lithoprobe southern canadian cordillera transect in conjunction with the lithoprobe southern canadian cordillera program an extensive examination of geochemical indicators of origins movement chemical evolution and economic significance of paleocrustal fluids was conducted the study area covers approximately 360 000 km2from the canadian rockies to vancouver island research incorporated petrological mineralogical fluid inclusion 18o d 13c and rb sr studies of samples of quartz carbonate veins and other rock types the results of the study document a variety of pre syn and postorogenic crustal fluid events in the rockies a major pre laramide hydrothermal event was identified which was comprised of a west to east migration of warm saline brines this was followed by a major circulation of meteoric water in the rockies during laramide uplift in the southern omineca extensional zone convecting surface fluids penetrated to the brittle ductile transition at 350 450 c and locally into the underlying more ductile rocks a principal c

carbon and oxygen isotope study of hydrothermal carbonates in the zinc lead deposits of the san vicente district central peru a quantitative modeling on mixing processes and co2 degassing abstract carbon and oxygen isotope studies of the host and gangue carbonates of mississippi valley type zinc lead deposits in the san vicente district hosted in the upper triassic to lower jurassic dolostones of the pucara basin central peru were used to constrain maiels of the ore formation a mixing model between an incoming hot saline slightly acidic radiogenic pb sr fluid and the native formation water explains the overall isotopic variation 13 c 11 5 to 2 5 relative to pdb and 18 o 18 0 to 24 3 relative to smow of the carbonate generations the dolomites formed during the main ore stage show a narrower range 13 c 0 1 to 1 7 and 18 o 18 7 to 23 4 which is explained by exchange between the mineralizing fluids and the host carbonates combined with changes in temperature and pressure this model of fluid rock interaction explains the pervasive alteration of the host dolomite i and precipitation of sphalerite i the open space filling hydrothermal white sparry dolomite and the coexisting sphalerite ii formed by prolonged fluid host dolomite interaction and limited co 2 degassing late void filling dolomite iii or calcite and the associated sphalerite iii formed as the consequence of co 2 degassing and concomitant ph increase of a slightly acidic ore fluid widespread brecciation is associated to co 2 outgassing consequently pressure variability plays a major role in the ore precipitation during the late hydrothermal events in san vicente the presence of native sulfur associated with extremely carbon light calcites replacing evaporitic sulfates e g 13 c 11 5 altered native organic matter and heavier hydrothermal bitumen from 27 0 to 23 0 13 c points to thermochemical reduction of sulfate and or thiosulfate the 13 c and 18 o values of the altered host dolostone and hydrothermal carbonates and the carbon isotope composition of the associated organic matter show a strong regional homogeneity these results coupled with the strong mineralogical and petrographic similarities of the different mvt occurrences perhaps reflects the fact that the mineralizing processes were similar in the whole san vicente belt suggesting the existence of a common regional mineralizing hydrothermal system with interconnected plumbing

a salt diapir related mississippi valley type deposit the bou jaber pb zn ba f deposit tunisia fluid inclusion and isotope study the bou jaber ba f pb zn deposit is located at the edge of the bou jaber triassic salt diapir in the tunisia salt diapir province the ores are unconformity and fault controlled and occur as subvertical column shaped bodies developed in dissolution collapse breccias and in cavities within the late aptian platform carbonate rocks which are covered unconformably by impermeable shales and marls of the fahdene formation late albian cenomanian age the host rock is hydrothermally altered to ankerite proximal to and within the ore bodies quartz as fine grained bipyramidal crystals formed during hydrothermal alteration of the host rocks the ore mineral assemblage is composed of barite fluorite sphalerite and galena in decreasing abundance the ore zones outline distinct depositional events sphalerite galena barite ankerite and fluorite fluid inclusions commonly oil rich have distinct fluid salinities and homogenization temperatures for each of these events sphalerite galena 17 to 24 wt nacl eq and th from 112 to 136 c ankerite barite 11 to 17 wt nacl eq and th from 100 to 130 c fluorite 19 to 21 wt nacl eq th from 140 to 165 c the mean temperature of the ore fluids decreased from sphalerite 125 c to barite 115 c and increased during fluorite deposition 152 c then decreased to 110 c during late calcite precipitation laser ablation inductively coupled plasma mass spectrometry la icp ms analyses of fluid inclusions in fluorite are metal rich hundreds to thousands ppm pb zn cu fe but the inclusions in barite are deficient in pb zn cu fe inclusions in fluorite have cl br and na br ratios of several thousand consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a br enriched brine derived from evaporation plus a component of halite dissolution the salinity of the barite hosted fluid inclusions is less than obtained simply by the evaporation of seawater to halite saturation and requires a dilution of more than two times by meteoric water the higher k na values in fluid inclusions from barite suggest that the brines interacted with k rich rocks in the basement or siliciclastic sediments in the basin carbonate gangue minerals ankerite and calcite have 13c and 18o values that are close to the carbonate host rock and indicate fluid equilibrium between carbonate host rocks and hydrothermal brines the 34s values for sphalerite and galena fall within a narrow range 1 to 10 with a bulk value of 7 5 indicating a homogeneous source of sulfur the 34s values of barite are also relatively homogeneous 22 with 6 higher than the 34s of local and regional triassic evaporites 15 the latter are believed to be the source of sulfate temperature of deposition together with sulfur isotope data indicate that the reduced sulfur in sulfides was derived through thermochemical sulfate reduction of triassic sulfate via hydrocarbons produced probably from late cretaceous source rocks the 87sr 86sr ratio in the bou jaber barite 0 709821 to 0 711408 together with the lead isotope values of bou jaber galena 206pb 204pb 18 699 to 18 737 207pb 204pb 15 635 to 15 708 and 208pb 204pb 38 321 to 38 947 show that metals were extracted from homogeneous crustal source s the tectonic setting of the bou jaber ore deposit the carbonate nature of the host rocks the epigenetic style of the mineralization and the mineral associations together with sulfur and oxygen isotope data and fluid inclusion data show that the bou jaber lead zinc mineralization has the major characteristics of a salt diapir related mississippi valley type mvt deposit with superimposed events of fluorite and of barite deposition field relations are consistent with mineral deposition during the eocene miocene alpine orogeny from multiple hydrothermal events 1 zn pb sulfides formed by mixing of two fluids one fluid metal rich but reduced sulfur poor and a second fluid reduced sulfur rich 2 barite precipitation involved the influx of a meteoric water component that mixed with a barium rich fluid and 3 fluorite precipitated from a highly saline fluid with higher temperatures

subglacial recharge into the western canada sedimentary basin impact of pleistocene glaciation on basin hydrodynamics brine springs discharging from devonian carbonates of the western canada sedimentary basin have distinct water chemistry from brines in laterally equivalent units deeper in the basin stable isotope data suggest that the brine springs originated as pleistocene meltwater these waters are interpreted to originate as an influx of subglacial meltwater related to a reversal of the basin scale flow system caused by the overriding ice sheet esker distribution shows a notable relationship between shield and sedimentary rocks an integrated sedimentary basin ice sheet model supports the interpretation that high permeability carbonate units acted as preferential subglacial drains that in turn affected esker development the fluid flow history of the western canada sedimentary basin is characterized by back and forth movement through geological time in response to changing boundary conditions modern day flow systems may not then be indicative of historic movement of economic fluids through the basin

evidence for seasonality in early eocene high latitude sea surface temperatures abstract specific challenges still exist in our understanding of past greenhouse climate states whilst climate model simulations using atmospheric co2 concentrations consistent with proxy estimates broadly align with lower latitude proxy temperature estimates they struggle to reproduce the warming implied by proxies at higher latitudes especially in the marine realm this inconsistency has often led to the conclusion that climate models are insufficiently sensitive here we analyse the distribution of photozoan and heterozoan carbonates which provide important constraints for latitudinal sea surface temperature sst gradients to assess data model mismatches for the early eocene climatic optimum the carbonate facies distribution is compared against quantitative geochemical proxy temperature estimates 18 o mg ca clumped isotopes and tex86 and a new hadcm3l climate simulation good correspondence exists between the simulated cold month ssts and photozoan carbonates indicating hadcm3l is effectively reconstructing meridional temperature gradients into mid latitudes whilst there is good agreement between simulated mean annual ssts and geochemical proxy estimates in low latitudes the 18 o mg ca and tex86 estimates instead align with warm month ssts at higher latitudes in light of the carbonate facies evidence and consistency between our simulation and available terrestrial proxy temperature estimates this study supports previous claims that a warm season bias exists in many middle and high latitude sst estimates this helps resolve the discrepancy between climate simulations and marine proxies and shows that climate models and data might be more closely aligned than is appreciated further we demonstrate that simple and widely available proxies can play a fundamental role in contextualising wider paleoclimate uncertainties

zebra and boxwork fabrics in hydrothermal dolomites of northern canada indicators for dilational fracturing dissolution or in situ replacement zebra and boxwork fabrics in manetoe and presqu ile hydrothermal dolomites provide critical data for discrimination between hypotheses for their origin in a unique occurrence sets of weakly imbricated decimetre sized curvilinear lenticles of white dolospar are developed within sub metre sized tongues of greyish white dolomitized crinoidal packstone and grainstone this nascent zebra fabric has developed along wavy to nodular intra bed sedimentary partings primary bedding can be traced through dolomitized masses containing these fabrics into the surrounding undolomitized limestone all zebra and boxwork fabrics are confined within single beds consistent with an early burial time of origin no change in bed thickness occurs across zebra or boxwork fabrics within beds this indicates a dissolutional rather than a dilational origin for the creation of pore space partly cemented with white dolospar the dolomitized groundmass displays an abruptly gradational or sharp transition to centripetal saddle dolomite cement which partially to nearly completely occludes vugs circulation of geothermally heated hypersaline devonian elk point basinal sea water brines led to dissolution and replacive dolomitization of limestone adjacent to vugs and near contemporaneous precipitation of white dolospar within dissolutional vugs consistent with geochemical simulations the presence of downward extending galleries of white dolospar cemented solution collapse breccia provides further support for an interpretation of regional thermally driven convection of hydrothermal evaporative sea water brines across a broad area of northern canada the absence of gases under pressure in vacuoles within fluid inclusions from manetoe and presqu ile dolospars is also more consistent with a dissolutional and contemporaneous dolomitization origin for these fabrics rather than an origin involving dilational fracturing for space creation and dolospar precipitation the ubiquitous presence of zebra and boxwork fabrics in hydrothermal dolomite reservoirs indicates that they are not confined fault zones and instead occur wherever precursor limestones had relatively greater porosity and permeability prior to dolomitization

seasonal variability in arctic temperatures during early eocene time abstract as a deep time analog for today s rapidly warming arctic region early eocene 52 53 ma rock on ellesmere island in canada s high arctic 79 n preserves evidence of lush swamp forests inhabited by turtles alligators primates tapirs and hippo like coryphodon although the rich flora and fauna of the early eocene arctic imply warmer wetter conditions than at present the quantification of eocene arctic climate has been more elusive by analyzing oxygen isotope ratios of biogenic phosphate from mammal fish and turtle fossils from a single locality on central ellesmere island we infer early eocene arctic temperatures including mean annual temperature mat of 8 c mean annual range in temperature of 16 5 19 c warm month mean temperature of 19 20 c and cold month mean temperature of 0 3 5 c our seasonal range in temperature is similar to the range in estimated mat obtained using different proxies in particular relatively high estimates of early eocene arctic mat and sst by others that are based upon the distribution of branched glycerol dialkyl glycerol tetraether gdgt membrane lipids in terrestrial soil bacteria and isoprenoid tetraether lipids in marine crenarchaeota fall close to our warm month temperature suggesting a bias towards summer values from a paleontologic perspective our temperature estimates verify that alligators and tortoises by way of nearest living relative based climatic inference are viable paleoclimate proxies for mild above freezing year round temperatures although for both of these reptilian groups past temperature tolerances probably were greater than in living descendants

δ18o seasonality of planktonic foraminifera from southern ocean sediment traps latitudinal gradients and implications for paleoclimate reconstructions abstract the oxygen isotopic record obtained from globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s was analysed for 5 sediment traps moored in the southern ocean and southwest pacific the traps extend from subtropical to the polar frontal environments providing the first analysis of seasonal foraminiferal 18 o records from these latitudes comparison between the foraminiferal records and various equations for predicted 18 o of calcite reveals that the predicted 18 o is best captured by the equations of epstein et al 1953 epstein s buchsbaum r lowenstam h a urey h c 1953 revised carbonate water isotopic temperature scale geological society of america bulletin 64 1315 1326 and kim and o neil 1997 kim s t o neil j r 1997 equilibrium and non equilibrium oxygen isotope effects in synthetic carbonates geochimica et cosmochimica acta 61 3461 3475 the epstein equation shows a constant offset from the 18 o of g bulloides and n pachyderma s across the full range of latitudes the seasonal range in 18 o values for these two species implies a near surface habitat across all sites while g inflata most likely dwells at 50 m depth a significant finding in this study was that offsets from predicted 18 o for g bulloides do not correlate to changes in the carbonate ion concentration this suggests that co 3 2 in and of itself may not capture the full range of carbonate chemistry conditions in the marine system this sediment trap deployment also reveals distinct seasonal flux patterns for each species comparison between flux weighted isotopic values calculated from the sediment traps and the isotopic composition of nearby surface sediments indicates that the sedimentary records retain this seasonal imprint at the 51 s site g bulloides has a spring flux peak while n pachyderma s is dominated by summer production the imprint of these differing seasonal production patterns on the flux weighted 18 o values results in more depleted 18 o for n pachyderma s than for g bulloides interpretations of n pachyderma s isotopic composition as a record of subsurface conditions may therefore need to be refined with implications for interpretation of depleted glacial 13 c for this species sigman boyle 2000 sigman d m boyle e a 2000 glacial interglacial variations in atmospheric carbon dioxide nature 407 859 869

fracture controlled paleohydrology in a map scale detachment fold insights from the analysis of fluid inclusions in calcite and quartz veins abstract this study uses fluid inclusions in quartz and calcite veins to characterize the fracture controlled paleohydrology of a map scale evaporite cored detachment fold in the sierra madre oriental of northeastern mexico field observations indicate that the veins are tectonic in origin and that they formed in a general sequence that corresponds to four broad stages of progressive folding we collected samples from each vein stage in various structural and stratigraphic positions across the fold after determining the mineral paragenesis and origin of inclusions in each sample we used standard microthermometric techniques to measure the homogenization temperatures t h salinities and eutectic temperatures of the available two and three phase aqueous inclusions neither t h salinity nor eutectic temperature varied systematically with inclusion origin or mineral type the data are also not significantly correlated with structural position or vein type but are strongly partitioned by stratigraphy suggesting that the area was a vertically stratified hydrologic system consisting of three regional paleohydrostratigraphic units an upper unit comprised the indidura formation through difunta group and is characterized by t h near 150 c and salinity t h near 150 c and salinities near 12 or 22 wt nacl equivalent the lower unit comprised the zuloaga and la casita formations and is characterized by an average t h near 225 c and salinities in three groups near 12 22 or 36 wt nacl equivalent the preservation of multiple distinct fluid types in many veins suggests that fracture development during folding and uplift created a second paleohydrologic system that overprinted the vertically stratified system fracture controlled fluid migration in this second system occurred in periodic repeated and spatially variable pulses