geochemistry of cretaceous oceanic red beds a synthesis abstract this paper summarizes the geochemistry of cretaceous oceanic red beds corbs their depositional conditions and their significance in reconstructing marine environments we report major and minor element compositions of carbonate clayey and siliceous corbs and compare these with average element compositions of carbonates deep sea carbonates deep sea clays and average shale compositions element distributions in carbonate corbs are mostly similar to average carbonate compositions in particular sr concentrations are more comparable to average carbonates than deep sea carbonate sr concentrations clayey corbs are high in al ti k and fe their minor element compositions are more similar to average shale than deep sea clay which generally has higher values in minor elements in comparison siliceous corbs have at least two times lower al but higher si concentrations than clayey corbs we further speculate on possible reactions involved in iron mobilization and corb formation

geochemistry of the thermal springs of mount taftan southeastern iran abstract thermal and cold water chemistry from the southern flank of mount taftan was investigated in order to discriminate among hydrochemical facies isotopic characteristics geothermal reservoir and identify the major geochemical processes that affect water composition the waters from both the hot and cold springs show high total dissolved solids content and are strongly to lightly acidic calcium is the dominant cation in terms of anions the taftan hot springs are cl so 4 type there is also a hco 3 type cold spring the so 4 cl ratios on an so 4 cl hco 3 diagram confirm the volcanic origin of the hot waters conservative elements indicate that the three types of analysed water have similar origin and the difference in concentration is due to dilution of thermal water with almost shallow fresh groundwater not affecting the elements proportions also the retrogressive 18 o enrichment with respect to the meteoric water line mwl confirms that thermal waters andesitic water have been diluted by shallow waters of meteoric origin comparison of the chemistry of thermal and cold springs and other evidences are indicative of an immature hydrothermal water system in taftan volcano because of waters immaturity temperatures in the geothermal reservoir in taftan region cannot be estimated accurately by applying na k k mg and quartz geothermometers

mid cretaceous oceanic red beds in the umbria marche basin central italy constraints on paleoceanography and paleoclimate abstract detailed studies of the mid cretaceous sedimentary strata in the umbria marche basin in italy revealed that aside from several well known organic rich black shale horizons that record oaes several varicolored mainly reddish horizons indicate oxic conditions at the ocean bottom eight such horizons have been identified in aptian cenomanian sequences in the umbria marche basin the dysoxic oxic beds alternate regularly but not cyclically and seem to be the result of non random processes their occurrence is not a completely random process the duration of deposition of these oceanic red beds orbs varies from 0 13 my orb4 recorded in the ticinella primula zone to 4 54 my for orb1 which spans the globigerinelloides ferreolensis zone to the ticinella bejaouaensis zone in the piobbico core mid cretaceous orbs are not a local phenomenon because they occur in the tethyan deposits in the southern and austrian alps the carpathians the northern caucasus the central north atlantic in northeastern england and in the western himalayas they provide evidence for periodic changes in redox conditions at the ocean bottom such changes could have been caused by changes in bioproductivity basin geometry sedimentation rates paleocirculation and or production of bottom waters with higher content of dissolved oxygen in response to changes in paleoclimate we suggest that the periodic inflow of colder more oxygenated bottom waters was the probable cause of orbs development either as a result of changes in the ocean bottom topography or as a result of brief cool climate periods however reliable proxies for changes in deep ocean circulation are still lacking if orbs were the result of the paleoclimate and therefore indirectly caused by changes in co2 in atmosphere they document the increased sensitivity and instability of the mid cretaceous climate thus changes in ocean dynamics were on a scale of several hundred thousand years to several million years which has not been considered by most theories of co2 cycling mid cretaceous greenhouse paleoclimate and paleocean dynamics

carbon sequestration activated by a volcanic co 2 pulse during ocean anoxic event 2 ninety four million years ago during ocean anoxic event 2 there was a marked increase in the burial of organic carbon in marine sediments measurements of stomata in fossil leaves show that the two main pulses of carbon burial were associated with a decline in atmospheric co2 levels of up to 26 the cretaceous ocean anoxic event 2 about 94 million years ago is thought to be linked to extensive volcanism which triggered a biogeochemical chain of events that eventually led to widespread marine anoxia and a remarkable increase in carbon burial in marine sediments1 2 3 it has been suggested that the event was accompanied by a substantial decrease in atmospheric co2 concentrations4 but the quantification of the drawdown remains controversial5 6 here we reconstruct atmospheric co2 concentrations throughout the ocean anoxic event from counts of the stomata in fossil leaves and use terrestrial carbon isotopes to link the reconstruction to marine records of the event7 8 we find that before the onset of ocean anoxia atmospheric co2 concentrations increased by 20 over background levels of 370 100 70 ppm this was part of a long term rise in atmospheric co2 levels presumably caused by volcanism which reached a peak of 500 400 180 ppm however two pulses of extensive carbon burial during the ocean anoxic event as indicated by positive carbon isotope excursions are associated with decreased atmospheric co2 concentrations we conclude that the sequestration of marine organic carbon led to a decrease in atmospheric co2 concentration of up to 26 during ocean anoxic event 2

chemical and isotopic characteristics of geothermal fluids from sulphur springs saint lucia abstract sulphur springs is a vigorous geothermal field associated with the active soufriere volcanic centre in southern saint lucia lesser antilles island arc the sulphur springs park is an important tourist attraction touted as the world s only drive through volcano with some of the hot pools being developed into recreational pools some 200 000 people visit the park each year since 2001 the hydrothermal fluids of sulphur springs have been sampled as part of an integrated volcanic monitoring programme for the island gas and water samples were analysed to characterise the geochemistry of the hydrothermal system and to assess the equilibrium state and subsurface temperatures of the reservoir this has also enabled us for the first time to establish baseline data for future geochemical monitoring the gases are of typical arc type composition with n2 excess and low he and ar content the dry gas composition is dominated by co2 ranging from 601 993 mmol mol with deeper magmatic sourced h2s rich vapour undergoing boiling and redox changes in the geothermal reservoir to emerge with a hydrothermal signature in the fumarolic gases fluid contributions from magmatic degassing are also evident mainly from the moderate to high contents of hcl and deeply sourced h2s gas respectively sulphur springs hydrothermal waters have acid sulphate type compositions so4 78 4008 mg l ph 3 7 and are of primarily meteoric origin which have been affected by evaporation processes based on the enrichment in both 18o and d 18o 1 to 15 and d 9 to 14 respectively in relation to the global meteoric water line gmwl these waters are steam heated water typically formed by absorption of h2s rich gases in the near surface oxygenated groundwaters reservoir temperatures calculated from the evaluation of gas equilibria in the co2 ch4 h2 system reveal higher temperatures 190 to 300 c than those derived from quartz geothermometry 95 to 169 c which appeared to be affected by dilution with meteoric waters generally no significant variations in fluid geochemistry of the hydrothermal system were observed between 2001 and 2006 and we propose that there were no changes in the state of volcanic activity during this period

turonian oceanic red beds in the eastern alps concepts for palaeoceanographic changes in the mediterranean tethys abstract several transitions of lower to middle turonian pelagic marl limestone cycles into oceanic red beds were studied at high resolution to gain a better understanding of the tethyan marine system before and during red bed initiation and development samples were analysed for mineralogy geochemistry and stable isotope composition in particular carbonate geochemistry of diagenetically largely unaltered calcite was used to explore palaeoceanographic changes in the western tethys principal component analysis of carbonate chemical data showed that the development of red coloured pelagic sediments is accompanied by a shift towards highly oligotrophic conditions in the surface ocean as well as a decrease in hydrothermal activity the formation of red beds is most likely associated with a shift towards more oxic conditions in basins with black shale deposits that eventually resulted in enrichment of thiophile elements in the entire basin depletion in nutrients most likely phosphate and red bed deposition followed the maximum flooding in the early turonian highly productive marsh areas from the proximal european shelf were reworked and supplied nutrients during transgression a gradual nutrient depletion during sea level highstand might be the cause of significantly diminished nutrient availability carbonate production in this low latitude setting was influenced by orbital variation in insolation 20 ka cycle stable carbon isotope stratigraphy reveals low sedimentation rates between 1 and 7 mm kyr and a duration of episodes of cretaceous oceanic red bed deposition between 30 and 360 kyrs

gas and water geochemistry of geothermal systems in dominica lesser antilles island arc abstract four of the nine potentially active volcanoes on the island of dominica in the lesser antilles volcanic island arc have associated active volcanic hydrothermal systems between 2000 and 2006 the gas and thermal waters from these systems were investigated to geochemically characterise the fluids gain insight into the temperature and equilibrium state of the underlying reservoirs and evaluate the feasibility of monitoring geothermal features as a volcano surveillance tool in dominica the geothermal gases are typical of those found in arc type settings with n2 excess and low amounts of he and ar the dry gas is dominated by co2 ranging from 492 to 993 mmol mol and has a hydrothermal signature with hydrogen sulphide as the main sulphurous gas the waters are predominantly acid sulphate so4 100 4200 mg l ph 4 and likely formed as a result of dilution of acidic gases in near surface oxygenated groundwater enrichment in both 18o and d with respect to the global meteoric water line gmwl confirms that the waters are of primarily meteoric origin but have been affected by evaporation processes quartz geothermometers gave equilibrium temperatures of 83 c 203 c these temperatures contrast with the higher equilibrium temperature ranges 170 c 350 c obtained for the gases using the h2 ar ch4 co2 gas ratios plot suggesting that the quartz geothermometers are affected by non attainment of equilibrium this may be a result of precipitation of the dissolved silica and or dilution by relatively cold shallow aquifers of the thermal fluids generally no significant variations in fluid gas chemistry of the hydrothermal systems were observed during the study period and we propose that there were no changes in the state of volcanic activity in this period one exception to this occurred in a feature known as the boiling lake which underwent a month long period of significant compositional temperature and water level fluctuations ascribed to a drastic decrease of hydrothermal input related to a perturbation in the lake probably seismically induced this geochemical study is part of an ongoing monitoring programme of dominica geothermal systems aimed at establishing long term geochemical observations for the purpose of volcano monitoring

fumarolic activity of avachinsky and koryaksky volcanoes kamchatka from 1993 to 1994 volcanic gas and condensate samples were collected in 1993 1994 from fumaroles of koryaksky and avachinsky basaltic andesite volcanoes on the kamchatka peninsula near petropavlovsk kamchatsky the highest temperature fumarolic discharges 220 c at koryaksky and 473 c at avachinsky are water rich 940 985 mmol mol of h2o and have chemical and isotopic characteristics typical of kamchatka kurile high and medium temperature volcanic gases the temperature and chemical and water isotopic compositions of the koryaksky gases have not changed during the past 11 years they represent an approximate 2 1 mixture of magmatic and meteoric end members low temperature near boiling point discharges of avachinsky volcano are water poor 880 mmol mol their compositions have not changed since the 1991 eruption and are suggested to be derived from partially condensed magmatic gases at shallow depth based on a simple model involving mixing and single step steam separation low water and high co2 contents as well as the observed cl concentration and water isotopic composition in low temperature discharges are the result of near surface boiling of a brine composed of the almost pure condensed magmatic gas high methane content in low temperature avachinsky gases and the 220 c koryaksky fumarole low c isotopic ratio in co2 at koryaksky 11 8 and water isotope data suggest that the meteoric end member contains considerable amounts of the regional methane rich thermal water discovered in the vicinity of both volcanoes

late cretaceous chronology of large rapid sea level changes glacioeustasy during the greenhouse world we provide a record of global sea level eustatic variations of the late cretaceous 99 65 ma greenhouse world ocean drilling program leg 174ax provided a record of 11 14 upper cretaceous sequences in the new jersey coastal plain that were dated by in tegrating sr isotopic stratigraphy and biostratigraphy backstripping yielded a late cre taceous eustatic estimate for these sequences taking into account sediment loading com paction paleowater depth and basin subsidence we show that late cretaceous sea level changes were large 25 m and rapid k1 m y suggesting a glacioeustatic control three large d 18 o increases are linked to sequence boundaries others lack sufficient d 18 o data consistent with a glacioeustatic cause and with the development of small 10 6 km 3 ephemeral ice sheets in antarctica our sequence boundaries correlate with sea level falls recorded by exxon production research and sections from northwest europe and russia indicating a global cause although the exxon record differs from backstripped estimates in amplitude and shape

paleo co2 variation trends and the cretaceous greenhouse climate the cretaceous was one of the most remarkable periods in geological history with a greenhouse climate and several important geological events reconstructions of atmospheric co2 using proxies are crucial for understanding the cretaceous greenhouse in this paper we summarize the major approaches for reconstructing co2 based on paleobotanical or geochemical data and synthesize the co2 variations throughout the cretaceous the results show that atmospheric co2 levels remained relatively high throughout the cretaceous but were lower in the early cretaceous highest in the mid cretaceous and gradually declined during the late cretaceous however this overall trend was interrupted by several rapid changes associated with ocean anoxic events oaes and the end cretaceous catastrophic event new data on paleo co2 levels from paleobotanical and paleosol evidences support not only the overall trends indicated by geochemical models but provide more precise records of the short term fluctuations related to brief episodes of climate change temporal resolution within the long quiet magnetic period in the middle cretaceous is one of the obstacles preventing us from a more comprehensive understanding of the co2 climate linkage but new paleo co2 determinations and climatic data from stratigraphic sections of sediments intercalated with datable volcanic rocks will allow a better understanding of the relationships between fluctuations of atmospheric co2 climate change and geological events

early telychian silurian marine siliciclastic red beds in the eastern yangtze platform south china distribution pattern and controlling factors the distribution pattern of early telychian turriculatus crispus graptolite biozone red beds in the eastern yangtze platform of south china is reconstructed based on regional geologic data the red beds are developed in three areas which are separated by regions without red deposition the distribution pattern indicates that the cathaysian oldland was the provenance of sediment rich in ferric oxides which are essential for the formation of red beds silurian marine siliciclastic red beds both in china and worldwide tended to develop during times of relatively low sea level coeval hematitic oolites that formed far from the coast may record a change from reducing to oxidizing conditions in the ocean furthermore it is likely that a fall in global sea level a transition from reducing to oxidizing conditions in the ocean and a cooling climate all of which were closely related to the early telychian valgu event promoted the global development of marine red beds during this period

development of a sequential extraction procedure for iron implications for iron partitioning in continentally derived particulates abstract the development of a sequential extraction procedure for iron in modern and ancient sediments is presented the scheme recognizes seven operationally derived iron pools 1 carbonate associated fe fe carb including siderite and ankerite 2 easily reducible oxides fe ox1 including ferrihydrite and lepidocrocite 3 reducible oxides fe ox2 including goethite hematite and akaganeite 4 magnetite fe mag 5 poorly reactive sheet silicate fe fe prs 6 pyrite fe fe py and 7 unreactive silicate fe fe u as such this is the first extraction scheme specifically developed to allow the separate identification of magnetite and the first to allow a complete evaluation of fe carbonate phases such as siderite and ankerite the scheme was developed following tests on pure mineral phases to evaluate the minerals solubilized by each technique and to determine optimum extraction times further tests on mixtures of pure minerals and on grain size separated sediments from two major us rivers and two glacial meltwaters validate the specificity of the scheme for different pools of iron minerals and demonstrate a high degree of reproducibility for each analytical stage the data obtained for the riverine and glacial sediments are additionally discussed in relation to the dominant modes of transport of different iron minerals in fine grained continental sediments

new oxygen isotope evidence for long term cretaceous climatic change in the southern hemisphere a new composite 18 o record generated from calcareous fine fraction and bulk sediments from the exmouth plateau details long term cretaceous climatic change at mid latitudes in the southern hemisphere assessment of new and previously published 18 o data indicates that a mid cretaceous global climatic optimum was achieved sometime between the time of the cenomanian turonian boundary and the middle turonian when surface ocean paleotemperatures were the highest of the past 115 m y periods of cooling and warming that reversed the general patterns were superimposed on long term aptian turonian warming and turonian maastrichtian cooling trends respectively extrapolation of southern hemisphere paleotemperature trends to maastrichtian paleotemperature data from a low latitude pacific guyot implies that maximum mid cretaceous low latitude paleotemperatures could have been in excess of 33 c

the late cretaceous western interior seaway as a model for oxygenation change in epicontinental restricted basins abstract deoxygenation is a critical problem facing the ocean as the world warms and has the potential to effect coastal upwelling zones shelf areas influenced by high runoff and nutrification and restricted and semi restricted basins the mechanisms that drive deoxygenation in these diverse environments are still not fully understood in part because the modern record of redox change is short and anoxia is still relatively rare in the modern ocean here we address this problem of scale by studying deoxygenation in the geologic past we summarize decades of individual studies of benthic foraminifera to generate a record of bottom water oxygen change in the cretaceous western interior sea wis of north america over 13 myr cenomanian campanian spanning two major sea level cycles the wis was prone to major changes in dissolved oxygen content throughout its long history sometimes directly antiphase to trends in the global ocean presented as maps our data show that bottom water oxygen within the wis was controlled by a combination of water mass source and mixing moderated by sea level and basin restriction areas flooded by cool boreal northern sourced waters in the northern and western parts of the seaway were better oxygenated than the eastern and southern portions of the seaway which were flooded by warmer tethyan southern sourced waters beyond east west differences explained by water mass the entire seaway was better oxygenated during periods of transgression and more poorly oxygenated to anoxic during periods of peak transgression highstand and regression we suggest that this pattern was due to the formation and downwelling of western interior intermediate water by the mixing of tethyan and boreal waters during transgressions an increasing volume of these watermasses entered the seaway mixed and downwelled well oxygenated surface water to the seafloor during late transgression highstand partial stratification and the encroachment of low oxygen waters from the open ocean caused dissolved oxygen levels to drop at the seafloor but continued downwelling prevented anoxia during the subsequent regression a decline in the volume of outside watermasses entering the seaway caused a reduction in mixing and weakened downwelling which led to stratification and seafloor anoxia as a model for other semi restricted basins the trends observed in the wis show that local changes in relative sea level mixing and circulation are critical in controlling oceanic deoxygenation in these environments in clear contrast to continental margins impinged by oxygen minimum zones like the contemporaneous demerara rise in the southern caribbean although the wis is larger than most semi restricted basins it is characterized by quasi estuarine circulation driving the interaction of normal marine and brackish watermasses and thus serves a model for similar shallow epicontinental basins of any size understanding how these processes vary in different environments is key to predicting susceptibility of regional water bodies to deoxygenation in the future with a warming world

evolution of mid cretaceous radiolarians in response to oceanic anoxic events in the eastern tethys southern tibet china abstract oceanic anoxic events oaes are well known from their widespread black shale and carbon isotopic excursions in the western and eastern tethys and atlantic ocean however the weakest link in the studies of the oaes is biological evolution sedimentological biostratigraphical and geochemical data from albian to coniacian strata in southern tibet recorded turnover events and fluctuations in diversity of the radiolarian fauna within the eastern tethys during oae 1d and oae 2 abundant radiolarian fossils were obtained from the gyabula formation with 93 species from 43 genera identified and assigned to the mid to upper cretaceous acaeniotyle umbilicata archaeospongoprunum tehamaensis crucella cachensis alievium superbum and dictyomitra formosa zones the association of carbon isotopic excursions black shale and radiolarian turnover indicates extensive changes in the ocean climate system nutrients are made increasing available to the marine plankton through submarine volcanic activity and rising sea level which were a likely cause of radiolarian turnover at or near the oaes active submarine tectonism volcanism leads to the expansion of the hypoxic zone and may cause many deeper dwelling forms to become extinct whereas most of the shallower dwelling radiolarians survive radiolarian evolution thus provides a useful record with which to seek understand relationships between climate paleoceanographic processes and plankton evolution

high frequency moderate to high amplitude sea level oscillations during the late early aptian insights into the mid aptian event galve sub basin spain abstract this paper presents a field based stratigraphic architecture research from the aptian of spain in which high frequency 7 cycles ma moderate to high amplitude 8 127 m sea level oscillations are evidenced by the repeated incision of palaeovalleys in a carbonate platform developed during the late early aptian in a rift setting global eustacy tectonic uplift and mantle dynamic topography are considered as potential mechanisms to explain the observed relative sea level record glacioeustacy is interpreted as the most reliable mechanism to drive the observed sea level oscillations however other mechanisms as oscillations of the groundwater capacity of sedimentary basins and sudden flooding of major a basin as the south atlantic rift are also considered a major cooling event is proposed to occur during the late early aptian as a response to a large scale episode of ignimbritic volcanism increased burial of organic carbon during the aptian oae 1a and a significant demise of carbonate platforms this cooling event is interpreted as the origin for glacioeustatic sea level oscillations during the mid aptian

geochemical and climatic effects of increased marine organic carbon burial at the cenomanian turonian boundary perhaps the most significant event in the cretaceous record of the carbon isotope composition of carbonate1 2 other than the 1 2 5 negative shift in the carbon isotope composition of calcareous plankton at the cretaceous tertiary boundary3 is the rapid global positive excursion of 2 13c enrichment which took place between 91 5 myr and 90 3 myr late cenomanian to earliest turonian c t boundary event 1 4 5 this excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon tdc reservoir resulting from an increase in rate of burial of 13c depleted organic carbon which coincided with a major global rise in sea level5 during the so called c t oceanic anoxic event oae 6 here we present new data from nine localities which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the c t boundary7 8 is nearly synchronous with that for carbonate and is widespread throughout the tethys and atlantic basins fig 1 as well as in more high latitude epicontinental seas the postulated increase in the rate of burial of organic carbon may have had a significant effect on co2 and o2 concentrations in the oceans and atmosphere and consequent effects on global climate and sedimentary facies

mid cretaceous albian santonian sea surface temperature record of the tropical atlantic ocean paleoclimate records of geologic time periods characterized by extreme global warmth such as the mid cretaceous are important for a better understanding of the earth9s climate system operating in an exceptionally warm mode here we applied an organic geochemical proxy tex 86 on organic matter rich albian santonian sediments recovered from ocean drilling program leg 207 sites 1258 and 1259 on demerara rise to reconstruct sea surface temperatures ssts in the western equatorial atlantic preceded by a stepwise cenomanian warming trend 31 35 c the onset of the cretaceous thermal maximum coincided here with the cenomanian turonian boundary event once established this extreme warm climate regime characterized by averaged tropical ssts close to 35 c lasted up to the turonian coniacian transition two pronounced cooler intervals 2 3 c interrupt this otherwise remarkably stable record providing the first 18 o independent evidence for middle turonian cooling that previously has been attributed to glacioeustatic sea level lowering coniacian ssts decline stepwise reaching a minimum in the santonian 32 33 c where cooling is most pronounced presumably concomitant with the first progressive opening of a deep water passage through the equatorial atlantic gateway

isotopic evidence for glaciation during the cretaceous supergreenhouse the turonian 93 5 to 89 3 million years ago was one of the warmest periods of the phanerozoic eon with tropical sea surface temperatures over 35 c high amplitude sea level changes and positive 18 o excursions in marine limestones suggest that glaciation events may have punctuated this episode of extreme warmth new 18 o data from the tropical atlantic show synchronous shifts 91 2 million years ago for both the surface and deep ocean that are consistent with an approximately 200 000 year period of glaciation with ice sheets of about half the size of the modern antarctic ice cap even the prevailing supergreenhouse climate was not a barrier to the formation of large ice sheets calling into question the common assumption that the poles were always ice free during past periods of intense global warming

environmental magnetism principles and applications 1 in environmental magnetism rock and mineral magnetic techniques are used to investigate the formation transportation deposition and postdepositional alterations of magnetic minerals under the influences of a wide range of environmental processes all materials respond in some way to an applied magnetic field and iron bearing minerals are sensitive to a range of environmental processes which makes magnetic measurements extremely useful for detecting signals associated with environmental processes environmental magnetism has grown considerably since the mid 1970s and now contributes to research in the geosciences and in branches of physics chemistry and biology and environmental science including research on climate change pollution iron biomineralization and depositional and diagenetic processes in sediments to name a few applications magnetic parameters are used to routinely scan sediments but interpretation is often difficult and requires understanding of the underlying physics and chemistry thorough examination of magnetic properties and of the environmental processes that give rise to the measured magnetic signal is needed to avoid ambiguities complexities and limitations to interpretations in this review we evaluate environmental magnetic parameters based on theory and empirical results we describe how ambiguities can be resolved by use of combined techniques and demonstrate the power of environmental magnetism in enabling quantitative environmental interpretations we also review recent developments that demonstrate the mutual benefit of environmental magnetism from close collaborations with biology chemistry and physics finally we discuss directions in which environmental magnetism is likely to develop in the future

iron rich carbonate tidal deposits angepena formation south australia a redox stratified cryogenian basin abstract the cryogenian angepena formation ca 650 ma of south australia records deposition in a peritidal environment equivalent to and landward of the balcanoona reef complex and offers valuable insights into shallow marine chemistry during the nonglacial interlude between two global ice ages the sedimentary facies comprise an iron rich marine red bed succession and include red mudcracked dolomitic shales tepee dolostone crossbedded intraclastic ooid grainstone and tepee related sheet cavities with marine cements these facies are interpreted to have been deposited in a cryogenian tidal flat to subtidal setting that is laterally equivalent to the reefal and back reef environments of the balcanoona formation marine cements from this environment are characterized by well preserved non and bright cathodoluminescent zoning and strong negative to slightly positive cerium ce anomalies ce ce we suggest that the angepena formation is indicative of intermittent synsedimentary iron oxide precipitation in an oxidized peritidal environment in an otherwise strongly ferruginous and anoxic oceanic setting large negative ce anomalies develop over a narrower depth range when compared to modern oxic marine settings highlighting the importance of dissolved mn and fe concentrations in controlling the magnitude of the negative ce anomalies overall coupled sedimentological and geochemical evidence suggest a neoproterozoic shallow marine system at the interface of an oxidizing atmosphere and an anoxic ferruginous marine system

origin of red pelagic carbonates as an interplay of global climate and local basin factors insight from the lower devonian of the prague basin czech republic abstract red pelagic sediments are relatively common in the phanerozoic they are often interpreted as products of sea bottom oxidation during greenhouse climate showing a conspicuous alternation with black shales and thus carrying important palaeoceanographic information the lower devonian pragian carbonate strata of the prague basin czech republic praha formation contain a marked band of red pelagic carbonate up to 15 m thick which can be correlated for several tens of km we investigated seven sections 17 to 255 m thick of the prague basin using the methods of facies analysis outcrop gamma ray logging diffuse reflectance spectroscopy optical microscopy element geochemistry magneto mineralogy and electron microprobe analysis the aim was to find the mineral carriers of the red colour investigate the stratigraphic context of the red carbonates and evaluate the local and global prerequisites for their formation the red pigmentation represents enrichment by hematite with respect to goethite approximately 31 of the total reflectance falling in the red colour band represents a threshold for red coloration the red pigmentation is carried by submicronic hematite dispersed in argillaceous pelagic calcilutite and or inside skeletal allochems gamma ray log correlation indicates that the red carbonate band developed in stratigraphic levels with low sedimentation rates typically from 1 to 7 1 mm kyr which are comparable to the mesozoic rosso ammonitico facies the red beds and the whole praha formation pragian to early emsian are characterized by low toc values

sources of iron for pyrite formation in marine sediments more than two hundred aerobic continental margin aerobic deep sea dysaerobic and anaerobic euxinic sediments have been examined for their variations in different operationally defined iron fractions each of which represents a different reactivity towards dissolved sulfide aerobic continental margin deep sea and dysaerobic sediments contain similar contents of highly reactive iron dithionite soluble iron plus pyrite iron poorly reactive iron iron soluble in hcl less that soluble in dithionite and unreactive iron total iron less that soluble in hcl by contrast non turbidite euxinic samples from the black sea as well as euxinic samples from the cariaco basin and framvaren are enriched in highly reactive iron these sediments contain a small lithogenous fraction and a large biogenous organic c rich fraction which decays by sulphate reduction in an iron rich water column to form pyrite rich sediment other anaerobic euxinic samples from the black sea orca basin and kau bay contain lower concentrations of biogenous sediment and are not therefore enriched in highly reactive iron degrees of pyritization dop for all the aerobic dysaerobic and anaerobic euxinix samples except those low in biogenous material are consistent with analogous ancient sediments and indicate that most pyrite formation occurs form the highly reactive iron fraction

a co2 decrease driven cooling and increased latitudinal temperature gradient during the mid cretaceous oceanic anoxic event 2 article i nfo the mid cretaceous is thought to be a greenhouse world with significantly higher atmospheric pco2 and sea surface temperatures as well as a much flatter latitudinal thermal gradient compared to the present this time interval was punctuated by the cenomanian turonian oceanic anoxic event oae 2 93 5 myr ago an episode of global massive organic carbon burial that likely resulted in a large and abrupt pco2 decline however the climatic consequences of this pco2 drop are yet poorly constrained we determined the first high resolution sea surface temperature sst record across oae 2 from a deep marine sedimentary sequence at ocean drilling program odp site 1276 in the mid latitudinal newfoundland basin nw atlantic by employing the organic palaeothermometer tex86 we found that ssts across the oae 2 interval were extremely high but were punctuated by a remarkably large cooling 5 11 c which is synchronous with the 2 5 5 5 c cooling in sst records from equatorial atlantic sites and the plenus cold event because this global cooling event is concurrent with increased organic carbon burial it likely acted in response to the associated pco2 drop our findings imply a substantial increase in the latitudinal sst gradient in the proto north atlantic during this period of global cooling and reduced atmospheric pco2 suggesting a strong coupling between pco2 and latitudinal thermal gradients under greenhouse climate conditions

stable isotopes and geochemistry of a campanian maastrichtian pelagic succession mudurnu goynuk basin nw turkey implications for palaeoceanography palaeoclimate and sea level fluctuations this study focuses on the palaeoclimatic evolution and relative sea level fluctuations of the northern branch of neotethys during the late campanian early danian the studied succession ismailler section is located in the mudurnu goynuk basin nw turkey and dominated by apparently continuous pelagic muddy deposits stable isotopic and elemental compositions of the mudrocks are investigated in order to evaluate the palaeoceanographic conditions as well as broad tectonic reconstruction of the basin the mudrock geochemistry suggests a tectonic reorganization during late campanian as reflected by a distinct shift from felsic to mafic sediment provenance in the ismailler section five 13c events are identified four or which are well correlatable with major events in other records around the world such as the late campanian event lce campanian maastrictian boundary cmb and the late maastrichtian event lme the relative sea level variations in the basin typically match both short and long term global sea level fluctuations the remaining globally uncorrelatable 13c event does coincide with tectonic uplift and the abrupt negative 13c shift and is inferred to be the result of regional factors the dominance of worldwide events in the records of the relatively restricted ocean branch reflects the strength of global factors

warming or cooling in the pragian sedimentary record and petrophysical logs across the lochkovian pragian boundary in the spanish central pyrenees abstract high resolution petrophysical correlation methods were applied for the first time to mid paleozoic rocks of the pyrenees the methods included magnetic susceptibility measurements ms gamma ray spectrometry grs and alignment of ms logs using the dynamic time warping dtw algorithm conodont biostratigraphy provided the basic framework necessary for work with the grs and ms logs despite differences in the sediment patterns and accumulation erosion rates the logs from two selected sections in the spanish central pyrenees show a striking symmetry that correlates well with the previously published logs from the barrandian area in the czech republic the high similarity between the petrophysical records from paleogeographically related but distant areas has the potential to contribute to the current discussions about the eustatic and climatic changes that took place in the overall greenhouse settings where evidence for any polar ice sheets is still absent in addition to the extant evidence of a major lochkovian pragian offlap combined with sea level lowering known from the north america evidence about a major sea level fall and drastic reconstruction of the climatic system in the pragian is now expanding over significant parts of the peri gondwanan belt the data from spain provide many new details about this change including the phenomenon of a stratigraphically condensed upper lochkovian a dramatically different type of sedimentation in the pragian and a grs th and ms anomalous stratigraphic interval in the middle pragian the multifaceted evidence allows us to determine the essential parts of the pragian as a still hot and humid period even with the strong differences from the possibly extremely hot lochkovian

cretaceous oceanic red beds corbs different time scales and models of origin abstract the cretaceous oceanic red bed corb is a newly opened window on global oceanic and climate changes during the cretaceous greenhouse world as a result of the international geoscience programmes 463 494 and 555 2002 2010 corbs have been documented in many places by numerous publications the principle goal of this paper is to summarize scientific advances on corbs including chronostratigraphy sedimentology mineralogy elemental and isotopic geochemistry and their relationship to oceanic anoxic events oaes palaeoclimate and palaeoceanography we propose a new geochemical classification of the corbs using cao al 2 o 3 and sio 2 values which lithologically refer to marly clayey and cherty corbs respectively detailed mineralogical studies indicate that hematite goethite and mn 2 bearing calcite are the minerals imparting the red color of corbs hematite clusters of several to tens of nanometers in the calcite structure are the main cause of the red coloring of limestones and the mn 2 bearing calcite gives additional red color goethite was thought to form originally with hematite and was subsequently transformed to hematite during late diagenesis chronostratigraphic data allow the distinction of two groups of corbs by their durations short term corbs are generally less than 1 myr in duration and seem to be on the scale of milankovitch cycles during the deposition of cretaceous reddish intervals from odp cores 1049 and 1050 low primary productivity and relatively high surface temperature resulted in low organic carbon flux into the sediments which reduced oxygen demand and produced oxidizing early diagenetic conditions in such an oxic environment iron oxides formed imparting the reddish color the long term corbs depositional events lasted longer than 4 myr and may be a possible consequence of the oaes enhanced amounts of organic carbon and pyrite burial during and after the oaes would have resulted in a large and abrupt fall in atmospheric co 2 concentration which probably induced significant global climatic cooling during and after the oaes global cooling would have enhanced formation of cold deep water increasing its oxidizing capacity due to the greater content of dissolved oxygen and would promote formation of oceanic red beds sedimentological mineralogical and geochemical data indicate that corbs were deposited under highly oxic oligotrophic conditions probably at a low sedimentation rate the cretaceous red and white limestones from italy have similar compositions of terrestrial input sensitive elements al ti k mg rb zr higher contents of fe 2 o 3 and depleted redox sensitive elements v cr ni and u and micronutrient elements cu zn indicating similar provenance sources but red limestones were deposited under more oxic conditions at the sediment water interface than white limestones the cretaceous red shales such as those from the north atlantic and tibet have similar mineralogy and geochemistry as the late cenozoic red clays in the pacific ocean and the environment where both are formed was well oxidizing at a very low sedimentation rate we compiled seventeen published stratigraphic examples of phanerozoic oceanic red beds including the late cenozoic red clays in the pacific different hypotheses explain the origin of red pigmentation of limestones and shales including 1 detrital origin of iron derived from continental weathering 2 iron bacterial mediation at the time of sedimentation and 3 iron oxidation in oligotrophic highly oxic environment additional research on phanerozoic oceanic red beds is needed in order to better document their origin and palaeoceanographic and palaeoclimatic significance

hydrothermal indications of early cretaceous red beds in lacustrine successions north yellow sea basin eastern china abstract controversies over the origin of globally distributed cretaceous red beds have mainly focused on climate vs weathering with potential hydrothermal influence in comparison to cretaceous oceanic red beds cretaceous lacustrine red beds exhibit chronological inconsistencies and their diverse tectonic settings suggest differing genetic mechanisms in this paper early cretaceous red beds in the north yellow sea basin one of mesozoic rift basins in eastern china that are associated with multi phase magmatic activities was chosen to document potential hydrothermal impact geological and geochemical analyses show that these red beds were syndepositional products developed in shallow to moderately deep lacustrine environments and that they were influenced by hydrothermal activity major and trace elements including enhanced al 2 o 3 normalized fe 2 o 3 and fe 2 o 3 total values al al fe mn and fe mn ti ratios ni co zn and fe mn ni co cu 10 ree la yb the concentrations of hydrothermally related ions invalid redox indicators of trace elements abnormally high fe 2 o 3 total content positive eu anomaly correlation of fe 2 o 3 total and eu anomaly and vitrinite reflectance ro vs total organic carbon toc all show strong hydrothermal fluid influence and heating effects by integrating and comparing data from previous studies we propose a hydrothermally affected sedimentation model for cretaceous red beds and associated sediments in magma activated lacustrine basins and conclude that the enriched metallic ions introduced by the hydrothermal fluids may be the most significant reason for the deposition of the red beds and the flushed ferric ions accompanied by hydrothermal fluid are the main ions that are hosted inside hematite causing the red sediment this model can be applied to similar lacustrine basins that experience strong magmatic activity

paleogeography as geological heritage developing geosite classification abstract geological heritage sites geosites are sites that contain information about the state and the dynamics of the earth paleogeographical paleoenvironmental geosites preserve paleoenvironments paleoecosystems and other relevant phenomena however the value of these sites can only be fully understood through professional interpretation of the observed features description of paleogeographical geosites in terms of the paleospace and the geologic time they encompass is challenging partially because of many uncertainties in the interpretations of a given geosite and in the paleogeographical paleobiogeographical and stratigraphical nomenclature these geosites can be classified on the basis of facies paleoecosystems ichnological value taphonomic patterns major events and catastrophes and geoarcheological potential that they exhibit some geosites comprise several subtypes and some are especially important for construction of paleogeographical maps moreover the paleogeographical geosite type always associates with other types of geosites 20 in total these combinations form complex geosites that contribute to geodiversity if information about the earth s past is especially valuable for a given complex geosite then the paleogeographical type is dominant

a critical look at iron paleoredox proxies new insights from modern euxinic marine basins enrichments in reactive iron occur under euxinic marine conditions that is where dissolved sulfide is present in the water column these enrichments result primarily from the export of remobilized iron from the oxic shelf which is scavenged from the euxinic water column during syngenetic pyrite formation and deposited in the underlying sediments strongly elevated ratios of highly reactive iron to total iron fehr fet and total iron to aluminum fet al and high degrees of pyritization dop are each products of this enrichment process these paleoredox proxies are among the most faithful recorders of ancient euxinia contrary to previous arguments iron enrichment is decoupled from biogenic sediment inputs but it does appear to be a uniquely euxinic phenomenon in other words we can rule out a major contribution from preferential physical transport of fehr rich detrital sediment to the deep basin which could also operate under oxic conditions furthermore enrichment via the shuttling of iron remobilized from oxic shelves appears to be limited by inefficient transport and trapping processes in deep oxic basins elevated fet al ratios in the euxinic sediments also cannot be a product of internal enhancement of the reactivity of the detrital iron pool without net fehr addition these conclusions are supported by observations in the modern black sea orca basin and effingham inlet fet al ratios are unambiguous recorders of paleoredox even in sediments that have experienced high degrees of metamorphic alteration however this study suggests that high siliciclastic accumulation rates can swamp the enrichment mechanism resulting in only intermediate dop values for euxinic sediments and fet al ratios that mimic the oxic shelf such dilution effects are well expressed in black sea basinal turbidites and rapidly accumulating muds on euxinic basin margins under conditions of persistent euxinia varying extents of fehr enrichment can illuminate spatial and temporal gradients in siliciclastic sedimentation the magnitude of enrichment is a function of the source shelf to sink ocean basin areal ratio suggesting that iron proxies can also record ocean scale paleoenvironmental properties through muted enrichments at times of very widespread euxinia for the first time manganese data are interpreted in light of the redox shuttle model as for the iron data the black sea orca basin and effingham inlet show enrichments in total manganese in the deep euxinic basin suggesting export from the suboxic porewaters of the oxic shelf and scavenging and burial in the basin the black sea data reveal iron and manganese enrichment across the broad deep euxinic basin suggesting efficient lateral transport and deep water mixing tied to the physical properties of the water column

chemical and isotopic compositions of fluids at cumbal volcano colombia evidence for magmatic contribution we present chemical and isotopic data for fumarolic vapor and thermal spring discharges from cumbal volcano sw colombia in 1988 cumbal showed signs of apparent reactivation gases and steam condensates were sampled from summit fumaroles 83 375 c of cumbal in 1988 1996 and discharges from thermal springs 15 37 c on its flanks in 1995 1996 based on relative co2 total s h2s so2 and hcl contents fumarolic discharges are principally magmatic in composition fumarolic steam condensates 1993 1996 have 18o values of 11 4 to 2 5 and d values of 91 to 43 18o and d compositions indicate mixing between local meteoric and magmatic waters 3he 4he ratios in 1993 1996 samples 5 3 7 9 rcor are consistent with addition of mantle derived helium 13cco2 values for 1996 samples 6 7 to 5 0 likely indicate contribution of marine carbonate organic sediment and mantle derived co2 34sstotal compositions 4 6 to 5 6 of 1988 1996 fumarolic discharges have magmatic signatures and may reflect cycles of deposition and remobilization of native sulfur thermal waters are acid sulfate or bicarbonate in composition relative concentrations of chemical constituents of thermal waters imply that the composition of waters is controlled by absorption of magmatic volatiles into shallow ground and surface waters dilution with meteoric waters along flow paths and dissolution of host rocks 18o and d compositions are consistent with a meteoric origin of waters 34sstotal values for thermal spring gas discharges 9 6 10 5 suggest deposition of 34s depleted sulfur minerals along flow paths chemical and isotopic compositions of 1988 1995 fumarolic discharges provide evidence for input of magmatic volatiles into the cumbal hydrothermal system from 1995 to 1996 geochemical data show increasing hydrothermal signatures suggesting a decline in magmatic volatile input

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

planktonic and benthic foraminiferal extinction events during the last 100 m y abstract five major planktonic and benthic foraminiferal extinction events occurred during the past 100 m y at the cenomanian turonian c t boundary at the cretaceous tertiary k t boundary in the latest paleocene in the late eocene and in the early middle miocene to clarify the character of the five events i estimated 1 paleo waterdepths and paleoenvironments where foraminifera were affected 2 the duration of each extinction event and 3 evaluated possible causes for each extinction event on the basis of recent literature these extinction events can be classified into three fundamentally different types 1 the mass extinction event at the k t boundary was abrupt and concentrated among surface dwelling species 2 extinctions at the c t boundary and during the latest paleocene were abrupt and mainly affected intermediate and deep water taxa over short periods 3 the late eocene and early middle miocene events affected surface and deep water species and involved stepwise or gradual extinctions over a long period 4 m y i attributed the extinction events to 1 a bolide impact for the k t event 2 a decrease in dissolved oxygen in intermediate and deep waters due to climatic warming for the c t and latest paleocene events and 3 long term global cooling for the late eocene and early middle miocene events the following relationships exist between the causes and types of extinction events 1 large extraterrestrial impacts strongly affected surface dwelling organisms in short term extinction events 2 intermediate and deep water low oxygen conditions induced by climatic warming have severely affected intermediate and deep water organisms over medium and short terms

the low temperature geochemical cycle of iron from continental fluxes to marine sediment deposition suspended sediments from 34 major rivers geographically wide spread and 36 glacial meltwater streams have been examined for their variations in different operationally defined iron fractions fehr iron oxides soluble in dithionite fepr iron soluble in boiling hcl but not in dithionite and feu total iron less that soluble in boiling hcl river particulates show a close association between fehr and total iron fet reflecting the effects of chemical weathering which derive oxide iron from and retain it in close association with total iron consistent with this continental scale average fehr fet ratios vary with runoff ratios average river runoff per unit area average precipitation per unit area by contrast the diminished effects of chemical weathering produce no recognizable association of fehr with fet in glacial particulates and instead both fepr and feu are closely correlated with fet reflecting essentially pristine mineralogy a comparison of the globally averaged compositions of riverine particulates and marine sediments reveals that the latter are depleted in fehr fepr and fet but enriched in feu the river and glacial particulate data are combined with estimates of authigenic hydrothermal atmospheric and coastal erosive iron fluxes from the literature to produce a global budget for fehr f e pr f e u and fet this budget suggests that the differences between riverine particulates and marine sediments can be explained by i preferentially removing fehr from the riverine particulate flux by deposition into inner shore reservoirs such as floodplains salt marshes and estuaries and ii mixing the resulting riverine particulates with fehr depleted glacial particulates preliminary measurements of inner shore sediments are consistent with i above phanerozoic and modern normal marine sediments have similar iron speciation characteristics which implies the existence of a long term steady state for the iron cycle this steady state could be maintained by a glacioeustatic feedback where fehr enriched riverine particulates are either more effectively trapped when sealevel is high small ice masses diminished glacial erosion or are mixed with greater masses of fehr depleted glacial particulates when sealevel is low large ice masses enhanced glacial erosion further important controls on the steady state for fehr operate through the formation of euxinic sediments and ironstones which also provide sealevel dependent sinks for fehr enriched sediment

cretaceous oceanic red beds as possible consequence of oceanic anoxic events article i nfo oceanic anoxic events oaes represent brief periods of burial of large amounts of organic carbon in the oceans during cretaceous time burial of organic carbon which preferentially sequestered isotopically lighter carbon during oaes resulted in positive 13 c excursions of 2 3 recognizable in global ocean these deposits are typically dark grey to black shales considered to be the result of interaction between extreme warm climate ocean circulation high bioproductivity and organic carbon preservation less interest has been given to periods between oaes when oxic deep sea deposits such as red marls and red shales were deposited during mid and late cretaceous the latter deposits are associated with very low content of organic carbon and oxic depositional environments which dominated western tethys in post turonian time up to the early eocene feedbacks among geochemical cycles in response to decreasing global temperatures increasing deep ocean circulation forced by high latitude deep water formation along the antarctic margin and widening and deepening of the interconnections between the oceanic basins may have been responsible for the major paleoceanographic change from deposition of organic carbon rich black shales during mid cretaceous to world wide deposition of cretaceous oceanic red beds corbs in the late cretaceous the presence of corbs sandwiched between mid cretaceous oaes may reflect major climate and paleoceanographic changes in a contrast to extremely warm climates during the oaes the corbs suggest cold periods and therefore oscillating climate shifts that have seldom been considered during modeling of cretaceous

possible atmospheric co2 extremes of the middle cretaceous late albian turonian 1 atmospheric carbon dioxide co2 estimates for the middle cretaceous mk have a range of 4000 ppm which presents considerable uncertainty in understanding the possible causes of warmth for this interval this paper examines the problem of mk greenhouse forcing from an inverse perspective we estimate upper ocean water temperatures from oxygen isotope measurements of well preserved late albian turonian planktonic foraminifera and compare these against temperatures predicted by general circulation model gcm experiments with co2 concentrations of 500 7500 ppm at least 4500 ppm co2 is required to match maximum temperatures inferred from well preserved planktonic foraminifera approximately 900 ppm co2 produces a good match between the model and the minimum temperature estimates for the mk an ocean model forced by these two extremes in surface conditions brackets nearly all available bottom water temperature estimates for this interval the climate model results support nearly the entire range of mk co2 estimates from proxy data the ocean model suggests possible mk oceanographic changes from deep water formation in the high latitude region of one hemisphere to the other hemisphere in response to changes in atmospheric temperatures and hydrologic cycle strength we suggest that rather than contradicting one another the various proxy co2 techniques especially those with high temporal resolution may capture true variability in co2 concentrations and that mk co2 could have varied by several thousand ppm through this interval

cool cretaceous climates new data from the albian of western australia although previous geological palaeobotanical and geochemical data from the albian of australia have suggested the possibility of cool palaeoclimates there are few well constrained stable isotope palaeotemperatures studies from this region in this paper we present the results of stable isotope analyses of dimitobelid belemnites from the albian gearle siltstone carnarvon basin western australia oxygen isotope values for diagenetically least altered samples give values ranging between 18 o 0 02 and 0 85 pdb which equate to a mean palaeotemperature of 10 08 c assuming w of 1 2 smow this value is broadly consistent with recently published isotope data from the albian antarctic and with estimates for mid cretaceous latitudinal temperature gradients implying that cool palaeoclimates occurred during a period of 9greenhouse9 earth

high amplitude redox changes in the late early triassic of south china and the smithian spathian extinction abstract the early triassic was a time of remarkably high temperatures large carbon cycle perturbations and episodes of widespread ocean anoxia the sediments in the nanpanjiang basin of south china provide superb opportunities to examine the sedimentary response to these extreme conditions especially during the crisis interval at the smithian spathian s s boundary we have investigated a deep water section at jiarong and a shallower water section at mingtang these contain a range of facies including black shales micritic limestone units and rudaceous carbonate event beds that include flat pebble conglomerates and breccia debrites that bear similarities to the hybrid event beds seen in clastic turbidite successions redox proxies pyrite framboids and trace metals reveal that widespread anoxia in the late smithian persisted into the novispathodus pingdingshanensis zone of the early spathian before a sharp transition to highly oxygenated griotte facies red marine strata in the icriospathodus collinsoni zone that records an oxic rebound benthic faunas are locally common but of low diversity and dominated by thin shelled bivalves and ostracodes with small foraminifers and exceptionally rare fish remains bioturbation was intense only in the early middle spathian i collinsoni conodont zone griotte facies anoxia and extremely high temperatures probably played a role in severely restricting the abundance of fish and the small sizes of marine invertebrates at this time the presence of ooids and seafloor fan cements in our study sections indicates highly saturated conditions rather than acidification at the end of the smithian

sharks and rays chondrichthyes from the upper cretaceous red beds of the south central pyrenees lleida spain indices of an india eurasia connection abstract six chondrichthyan taxa are recorded in late cretaceous maastrichtian red beds of the south central pyrenees tremp formation lleida spain indicating marine influence in the palaeoenvironment two ray species found in spain have been previously described in india one ray species conforms to the gondwanan genus igdabatis and the endemic indian species igdabatis indicus prasad and cappetta 1993 prasad g v r cappetta h 1993 late cretaceous selachian from india and the age of the deccan traps palaeontology 36 1 231 248 the other ray from the tremp formation is also close to the indian material assigned to rhombodus sp 2 the limited dispersal abilities of benthic rays points to a shallow trans tethyan connection between eurasia and india at the end of the cretaceous the data increase the evidence of a biogeographical relationship between eurasia and gondwanan continents at the cretaceous tertiary boundary

mid cretaceous desert system in the simao basin southwestern china and its implications for sea level change during a greenhouse climate abstract paleoclimatic indicators suggest that the mid cretaceous was one of the warmest intervals of the phanerozoic the period of the mid cretaceous super greenhouse also experienced an equator to pole temperature gradient much lower than that of the present day implying greater meridional heat transport by the atmosphere and or oceans however reconstructions of cretaceous atmospheric circulation have been hindered by a lack of relevant datasets based on reliable proxies or direct geological evidence aeolian deposits provide direct information about paleoclimate as well as the direction and intensity of paleo wind in the interiors of continents using petrologic and sedimentologic observations this study reassesses the terrestrial deposits of the mid cretaceous mangang formation in the simao basin of southwestern china originally considered to be aqueous deposits we reinterpret these strata as representing aeolian transport in a desert environment we suggest that the development of aeolian deposits in the mangang formation and coeval strata in adjacent basins was a local response to the prevailing desert climate in the mid to low latitudes of the northern hemisphere during the mid cretaceous which were dominated by subtropical high pressure systems on a planetary scale in addition with the closure of the mesotethys ocean the intermontane basins of the south china simao and indochina blocks became more isolated from atmospheric circulation bidirectional subduction of the bangong nujiang oceanic crust and the izanagi plate beneath east asia led to the development of andean type margins which created a rain shadow effect in continental east asia these factors caused the development of a tropical desert climate characterized by aeolian dunes and evaporite deposition we speculate that the severe depletion of groundwater reservoirs via the desertification of east asia may represent a previously unrecognized trigger for short term sea level changes during the ice free cretaceous greenhouse interval

deep sea paleotemperature record of extreme warmth during the cretaceous oxygen isotope analyses of well preserved foraminifera from blake nose 30 n paleolatitude north atlantic and globally distributed deep sea sites provide a long term paleotemperature record for the late albian maastrichtian interval that is difficult to reconcile with the existence of significant cretaceous ice sheets given reasonable assumptions about the isotopic composition of cretaceous seawater our results suggest that middle bathyal water temperatures at blake nose increased from 12 c in the late albian through middle cenomanian to a maximum of 20 c during the latest cenomanian and earliest turonian bottom waters were again 12 c during the middle campanian and cooled to a minimum of 9 c during the maastrichtian correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from blake nose comparison of global bottom water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late albian through late cenomanian to a hot greenhouse phase during the latest cenomanian through early campanian then to cool greenhouse conditions during the mid campanian through maastrichtian

glendonites as a paleoenvironmental tool implications for early cretaceous high latitude climates in australia glendonites calcite pseudomorphs after the metastable mineral ikaite caco3 6h2o occur in the late aptian interval of the bulldog shale in the eromanga basin australia and in other early cretaceous basins at high paleolatitudes ikaite precipitation in the marine environment requires near freezing temperatures not higher than 4 c high alkalinity increased levels of orthophosphate and high pco2 the rapid and complete transformation of ikaite to calcite at temperatures between 5 and 8 c provides an upper limit on the oxygen isotopic composition of the pore waters 2 6 w 3 4 smow if it is assumed that these pore waters are representative of the shallow eromanga basin the calculated w can be used to reassess belemnite fossil oxygen isotopic paleotemperatures temperature recorded by fauna living in the basin at the time of ikaite precipitation data previously reported as 11 to 16 c assuming w 0 0 smow yield paleotemperatures ranging from 1 to 5 c squarely in the range of ikaite stability the low w indicates hyposaline conditions most likely caused by mixing high latitude meteoric waters with seawater the 18o depleted low temperature waters suggest that the region was at least seasonally colder than previously accepted

the cenomanian turonian extinction and oceanic anoxic event evidence from southern tibet deep shelf locations on the perigondwanan margin of southern tibet record a major extinction of foraminifera and calcareous nannoplankton in the latest cenomanian top of the rotalipora cushmani zone this is followed by a low diversity survival interval that straddles the cenomanian turonian boundary whiteinella archaeocretacea zone during which only low diversity surface water dwelling foraminifera and nannoplankton and microfilaments are present rapid recovery in the early turonian saw the appearance of new species the reappearance of many lazarus species and the reestablishment of a diverse community of planktonic foraminifera that included a range of shallow to deep water column dwellers the extinction and survival intervals coincide with the development of dysaerobic facies characterised by small sized burrows and moderately large sized framboid pyrite populations at no time does the water column appear to have become sulfidic this study indicates that the end cenomanian oceanic anoxic and extinction events were also manifested in moderately high southerly palaeolatitudes on the southern margin of the tethyan ocean thereby increasing the known extent of this global event albeit with the proviso that the anoxic event was a dysoxic one

timing of diagenetic haematite growth in red pelagic limestones from gubbio italy abstract magnetite haematite and to a minor extent maghaemite are recognised in the cretaceous and paleocene red pelagic limestones at gubbio the magnetite is detrital or biological whereas the haematite grew during diagenesis from a goethitic precursor thermal and af demagnetization of samples collected from close to reversal boundaries indicate that the various magnetization components do not record the polarity reversal at exactly the same stratigraphic level in the few tens of centimetersbelow a recorded geomagnetic reversal defined by the magnetite magnetization some of the haematite grains are magnetized in the post reversal field the blocking temperature spectra of this haematite fraction with post reversal magnetization are found to shift toward higher temperatures as the reversal boundary is approached the blocking temperature spectra reflect the grain size spectra of the haematite which we interpret as arising by the continual nucleation of grains down to a certain burial depth where the conditions are no longer conducive to further haematite growth the depth below reversal boundaries to which haematite with post reversal magnetization can occur is estimated to be about 60 cm after compaction and is equivalent to a time of about 105 years for these particular sediments a detailed study of the magnetization components at reversal boundaries indicates that the first diagenetic growth of haematite through the single domain critical volume occurs prior to the mechanical fixation of the detrital or biological magnetite subsequently the diagenetic haematite grains do not rotate in response to the ambient geomagnetic field polarity as easily as the magnetite because of their occurrence as pigmentary coatings on larger non magnetic grains

geochemistry of hydrothermal fluids from an intraplate ocean island everman volcano socorro island mexico abstract socorro island mexico still volcanically active is an alkaline and peralkaline volcanic island in the eastern pacific ocean located on a mid ocean ridge spreading center that was abandoned at 3 5 ma gas and water samples collected on the island in 1999 from the dome fumaroles and hot springs of everman volcano have been analyzed for major components h o c s he and ar isotopic composition and noble gas abundances the boiling point temperature steam vents and low salinity thermal springs discharge cl free meteoric water and are typical surface manifestations of a high temperature hydrothermal system high h 2 and ch 4 contents up to 14 and 3 5 vol in dry gas respectively and an enrichment of ch 4 in 13 c 13 c ch 4 18 may suggest that these reduced gases were at least partially produced by the interaction of ultramafic rocks with water inside volcanic edifice due to serpentinization of olivine the 3 he 4 he ratios 6 0 6 6 r a which are lower than the morb values and the high he ne ratios 4000 and he ar ratios up to 4 indicate a contribution of radiogenic he from the oceanic crust or shallow magma chamber like at a low 3 he hot spot the maximum of the 40 ar 36 ar values 311 is close to the maximum value found in the socorro volcanic rocks noble gas abundances are close to values for the partially degassed air saturated water however with some excess ne concentrations an enrichment in 132 xe or depletion in 84 kr of the least air contaminated gas sample he ne 4000 relative to air saturated water can be related to the contribution of noble gases from a non atmospheric source probably oceanic crustal component assimilated in a shallow magma reservoir

evidence for late cretaceous late turonian climate cooling from oxygen isotope variations and palaeobiogeographic changes in western and central europe trends of stable oxygen isotope data through four european sections of middle upper turonian sediments show three phases of synchronous variations each phase having a duration of about 250 ka the isotopic variations are independent of local facies sedimentary thickness and diagenetic history two positive 18 o shifts are associated with a southward spread of northern macrofaunas this coincidence of geochemical and palaeontological data implies that the 18 o trends reflect a southward shift of cooler water masses this southward extension of cooler waters was caused by changes in ocean circulation and was associated with a major regression in the early late turonian

integrated stratigraphy magneto bio and chronostratigraphy and geochronology of the palaeogene pelagic succession of the umbria marche basin central italy

onset and demise of cretaceous oceanic anoxic events the coupling of surface and bottom oceanic processes in two pelagic basins of the western tethys

midlatitude shelf seas in the cenomanian turonian greenhouse world temperature evolution and north atlantic circulation 1 an 8 million year record of subtropical and midlatitude shelf sea temperatures derived from oxygen isotopes of well preserved brachiopods from a variety of european sections demonstrates a long term cenomanian temperature rise 16 20 c midlatitudes that reached its maximum early in the late turonian 23 c midlatitudes superimposed on the long term trend shelf sea temperatures vary at shorter timescales in relation to global carbon cycle perturbations in the mid cenomanian and the late turonian two minor shelf sea cooling events 2 3 c coincide with carbon cycle perturbations and times of high amplitude sea level falls although this evidence supports the hypothesis of potential glacioeustatic effects on cretaceous sea level the occurrence of minimum shelf sea temperatures within transgressive beds argues for regional changes in shelf sea circulation as the most plausible mechanism the major carbon cycle event in the latest cenomanian oceanic anoxic event 2 is accompanied by a substantial increase in shelf sea temperatures 4 5 c that occurred 150 kyr after the commencement of the 13c excursion and is related to the spread of oceanic conditions in western european shelf sea basins our oxygen isotope record and published 18o data of pristinely preserved foraminifera allow the consideration of north atlantic surface water properties in the cenomanian along a transect from the tropics to the midlatitudes on the basis of fossil derived 18o estimated w ranges and modeled salinities temperature salinity density ranges were estimated for tropical subtropical and midlatitude surface waters accordingly the cenomanian temperate shelf seas waters have potentially the highest surface water density and could have contributed to north atlantic intermediate to deep waters in the preopening stage of the equatorial atlantic gateway

early triassic oceanic red beds coupled with deep sea oxidation in south tethys abstract carbonate oceanic red beds orbs are unusual in phanerozoic shelf settings but can be widespread during discrete intervals several scenarios have been invoked to explain the origin of these orbs but there remains uncertainty about the process by which the red pigmentation of orbs forms here we propose that the occurrence of orbs at intermediate water depths in shelf regions is controlled by fluctuations in the redox state of deeper waters we have examined early triassic peri gondwana shelf sections in south tibet which show the development of spathian late early triassic orbs at intermediate water depths the red color of these orbs is imparted by randomly dispersed hematite crystals that are microns in size showing weak alteration by late burial diagenesis widespread anoxia in both shelf seas and the oceanic realm was well developed in the early triassic synchronous occurrence of spathian orbs in deep shelf regions is closely related to the improved oxidation in deeper settings from anoxia to dysoxia based on changes in the redox proxy of pyrite framboid sizes it is therefore inferred that prolonged deep water anoxia might serve as source of fe ii for the formation of orbs when intensified upwelling develops the global occurrence of early triassic orbs is coincident with the significant rebound of biodiversity after the permian triassic mass extinction indicating the occurrence of orbs marks the terminal stage of an oceanic anoxic event and orbs can serve as an indicator of the ameliorated marine ecosystem

reactive iron in marine sediments abstract a combined field laboratory study has been undertaken to explore the mineralogy concentrations and reactivity towards sulfide of iron in marine sediments also considered is the importance of bacterial fe liberation in regulating pore water chemistry two contrasting marine environments are included one is the relatively fe poor foam site and the other is the fe rich sediment of the subaqueous mississippi delta results show that oxide minerals are the most important fe phases in early diagenetic pyrite formation however viewed separately lepidocrocite and ferrihydrite are more reactive towards sulfide than goethite and hematite when fe oxides are present in relatively high concentrations dissolved sulfide is nearly absent from sediment pore waters with concomitant high concentrations of dissolved fe even in the presence of active sulfide production by sulfate reduction a combination of experimental results and diagenetic modelling shows that in some sediments pore water fe finds it origin in the bacterial reduction of iron oxides this seems the case even though greater amounts of fe are reduced by reaction of sulfide with iron oxides it appears that distinct microenvironments may exist in marine sediments where in one microenvironment sulfide reacts with fe oxides locally precipitating fe sulfide minerals in another fe reduced and solubilized by microorganisms migrates freely into solution

composition and depositional environment of major eastern canadian oil shales abstract in eastern canada following the acadian orogeny two lithologically and chronologically distinct sequences of oil shale were deposited in the late devonian carboniferous maritimes basin the oldest sequence occurs within the moncton subbasin a transcurrent and asymmetric basin 200 km in length in southeastern new brunswick the oil shales are largely confined to the medial part of the 165 1800 m thick early carboniferous tournaisian albert formation the oil shales range from massive slightly organic rich dolostone to carbonate rich lamosite with an organic fraction of 1 30 toc and comprising mainly alginite with locally abundant liptodetrinite and vitrinite rock eval and chromatography data indicate mostly type i and type ii kerogens lamalginite fluorescent spectra indicate immature to mature sediments in agreement with surface oil shows and the presence of a small oil and gas field sourced from albert oil shales the oil shale composition reflects deposition in a chemically stratified lacustrine setting characterized by slightly saline and alkaline waters and deltaic sedimentation the younger sequence occurs within the stellarton basin a 6 18 km pull apart basin situated in northern nova scotia the oil shales form part of the 2600 m thick late westphalian b early westphalian d coal bearing stellarton formation a total of 60 oil shale beds 1 45 m thick some transitional to coal have been documented the oil shale lithotypes are silicate rich and include fissile shale minor blocky cannel shale and lesser stellarite boghead shale with an organic fraction depending upon lithotype of 1 41 toc comprising variable amounts of liptinitic groundmass material telalginite and vitrinite rock eval petrography and gas chromatography data indicate mature type ii and locally type i and type iii kerogens extract chromatography and carbon isotope data indicate that the coals of the formation rather than the oil shales are the most probable source of the hydrocarbon shows within the stellarton formation the composition of the oil shales and the transition of some oil shales to coal reflects deposition in a nearshore to open lacustrine environment bordered by peat swamps the principal causes for compositional differences between the albert and stellarton oil shales are 1 the influence of basin size and paleogeographic setting on sediment supply to the albert and stellarton lakes 2 the hydrological conditions closed versus open of the albert and stellarton lakes 3 the influence of swamps on the ph and organic content of the stellarton lakes and 4 climate

early turonian pelagic sedimentation at moria umbria marche italy primary and diagenetic controls on lithological oscillations abstract the upper cretaceous of the umbria marche basin italy consists of an alternation of calcareous and siliceous fine grained sedimentary rocks in which the calcareous lithologies are predominant the cenomanian succession is dominated by white micritic limestones and contains a black shale horizon bonarelli level in its uppermost part which is the regional expression of oceanic anoxic event 2 in the turonian the rocks gradually become red upwards and are referred to as cretaceous oceanic red beds the lithological variability in the succession reflects the local response of sedimentary systems to varying local and global environmental conditions in this study local processes behind the transition from black shale to red bed deposition and in particular behind lithological oscillations within the lowermost turonian are studied and placed in their global context sediment colour composition geochemistry and nannofossil content were studied using samples of the scaglia formation at moria umbria marche basin the results show that following the cenomanian turonian boundary terrigenous input decreased and its composition was different in calcareous and siliceous oozes organic productivity was high during the deposition of siliceous ooze due to upwelling and varied on orbital timescales the alternation between the siliceous and calcareous ooze was further controlled by carbonate dissolution small fluctuations in the calcite compensation depth ccd had a significant impact on sediment composition because depositional depth was between the lysocline and the ccd diagenesis resulted in the segregation of carbonate and silica in the concentration of terrigenous material in smarl interbeds and in the enhancement of bedding after the earliest turonian ocean circulation patterns changed seawater temperatures declined slowly and seawater became better oxygenated productivity and terrigenous input also declined and the resulting combination of oxygen demand in the sediments and sedimentation rates favoured the formation of authigenic haematite in the sediments which led to their reddening

formation of holocene sedimentary laminae in the black sea and the role of the benthic flocculent layer holocene black sea sediments recovered in 1988 and 1993 from box cores and gravity cores were analyzed geochemically microscopically and with backscattered electron imagery bsei in order to determine the temporal geochemical and sedimentological relationships between the benthic flocculent layer often referred to as the fluff layer and the formation of underlying laminated unit i sediments existence of a permanent benthic fluff layer in the black sea basin is suggested acting as a geochemical transition layer within which all sedimentary particles are hydraulically sorted and particles subject to dissolution or organic remineralization are altered prior to accumulation we propose that particle residence time within the benthic fluff layer is a key factor in determining sedimentary microfabric and geochemical composition of laminated unit i sediments we present a schematic model depicting the above relationships and use it to propose a paleoflux scenario for laminae formation in the unit ii sapropel

late cretaceous campanian carbon isotope events sea level change and correlation of the tethyan and boreal realms abstract carbon stable isotope stratigraphy provides unique insights into environmental change during the campanian the longest 83 5 71 3 ma but least well understood stage of the late cretaceous a new carbon isotope 13c profile for a 500 m thick campanian basal maastrichtian tethyan pelagic hemipelagic section near el kef northern tunisia is calibrated using data from a biostratigraphically well constrained succession at kalaat senan the general shapes of the tunisian 13c reference curve and published tethyan 13c profiles from elles tunisia and bidart sw france and a boreal curve for the trunch borehole eastern england are remarkably similar in all three areas a positive carbon isotope event of 0 2 13c in the mid campanian dated at 78 7 ma and a negative excursion of 0 4 in the upper campanian at 74 8 ma can be correlated between tunisia and england a positive excursion of 0 3 at 83 7 ma spans the santonian campanian boundary these isotope events enable precise inter regional correlations that are consistent with published nannofossil data review of campanian sea level data from north africa the middle east and northern europe indicates that major shifts in 13c profiles coincide with changes in eustatic sea level relatively stable 13c values in the lower campanian and their long term fall through the upper campanian reflect high and then falling eustatic sea levels and increased carbonate production short term 600 kyr positive excursions record greater organic productivity and or organic matter preservation and decreased carbonate fluxes during periods of rapid sea level rise and the drowning of carbonate platforms excursions were terminated by falling nutrient supply and increased carbonate deposition associated with epicontinental sea expansion and renewed carbonate platform growth during the late transgression and highstand negative excursions are linked principally to reworking of marine and terrestrial organic matter during rapid sea level fall carbon isotope stratigraphy is a powerful tool for correlation which can be used to test the validity of campanian global biostratigraphic frameworks and improve our understanding of the nature and timing of late cretaceous sea level change

astronomical constraints on global carbon cycle perturbation during oceanic anoxic event 2 oae2 abstract oceanic anoxic event 2 oae2 was a major disturbance in global carbon cycling and transient climate disruption triggered by a pulse of volcanic co2 although this well studied perturbation to the ocean atmosphere system offers a unique opportunity to better understand abrupt climate change in response to co2 forcing the origin evolution and duration of the event are still debated due in large part to the temporal resolution of existing oae2 records and uncertainty over the duration of the overall perturbation and c cycle shifts within it here we report coupled magnetic susceptibility ms and carbon isotope time series of 2 5 to 5 0 5 kyr resolution from an expanded oae2 interval from southern tibet china ms cyclicity indicates short eccentricity modulation permitting the construction of a high precision orbital timescale which when integrated with the high resolution 13 c carb record fully constrains the timing and nature of onset through recovery of oae2 revealing finer scale structure than previously recognized abrupt coupled shifts in 13 c carb and ms and changing phase relationships in step with transitions between high and low long eccentricity indicate orbitally linked changes in marine carbon cycling and monsoon dynamics superimposed on repeated wholesale oceanographic changes in particular the high resolution tibetan record reveals dynamic shifts in the phasing relationship of ms and 13 c which suggests that the initiation of ocean anoxia was probably not orbitally forced this finding is in sharp contrast with the paradigm of orbitally forced ocean anoxia conversely the new record suggests that termination of anoxia was likely orbitally forced and superimposed on a dramatic oceanographic change

the qualibou caldera st lucia west indies abstract recent geological geophysical and hydrogeochemical studies conducted in the qualibou area of st lucia west indies provide new data for reevaluation of the geothermal resource and recommendation of sites for renewed drilling activities this work supports the original hypothesis of tomblin that the qualibou depression is a caldera precaldera volcanic activity was concentrated along faults associated with regional ne and nw trending structures basaltic lavas dated at 5 5 ma crop out along the western coast and are overlain by andesitic composite cones dated at 1 2 and 0 9 ma which form the highest ridges of the island superimposed upon the andesitic cones are dacitic domes 0 25 ma the eroded plugs of two of these form the spectacular pitons the major event in this volcanic field was the intermittent eruption of the choiseul pumice concurrent with the formation of the qualibou caldera 32 000 to 39 000 yrs ago about 6 km3 dense rock equivalent of lithic crystal andesitic tephra was erupted mainly as nonwelded to welded pyroclastic flows and surges some of these tuffs have been identified in geothermal drill holes within the 12 km2 caldera postcaldera eruption of dacitic tephra and dome lava 20 000 to 32 000 yrs ago occurred from vents within the caldera and appear to be a result of magmatic resurgence a 5 2 km long dipole dipole dc resistivity survey measured along a north south trending line through the caldera gave apparent resistivity results similar to those obtained in previous studies these results are compatible with a caldera substructure where low apparent resistivities analysis and interpretation of hydrogeochemical data from the qualibou caldera indicate that a geothermal reservoir underlies the sulphur springs area and consists of three layers 1 an upper steam condensate zone 2 an intermediate two phase vapor zone and 3 a lower brine zone measured temperatures at depth of 212 c are complemented by estimated temperatures of 250 c in the brine layer the water chemistry of various thermal springs indicates upwelling primarily near the caldera center at sulphur springs which feeds steam to steamcondensate hot springs along the northern caldera wall

fluid geochemistry of hydrothermal systems in the arica parinacota tarapaca and antofagasta regions northern chile we investigate the chemical and isotopic composition of water and gas thermal discharges from six hydrothermal systems in the tarapaca and antofagasta regions northern chile surire puchuldiza tuja pampa lirima pampa apacheta el tatio and torta de tocorpuri to determine the chemical physical conditions at the fluid source the chemical facies of the thermal discharges vary from na cl el tatio puchuldiza tuja and part of surire where so42 rich waters also occur to na ca2 cl so42 pampa lirima ca2 so42 hco3 torta de tocorpuri and ca2 so42 pampa apacheta the gas seeps are characterized by the dominance of co2 h2s and ch4 with n2 ar ratios that occasionally are up to 450 significant amounts of so2 and hcl are present at pampa apacheta water and gas geothermometry suggests that el tatio and puchuldiza tuja fluid reservoirs have relatively high reservoir equilibrium temperature up to 270 c gases from pampa apacheta apparently equilibrated at unusually high temperature for hydrothermal fluids up to 350 c being likely related to an active magmatic system as testified by the presence of highly acidic gas compounds such as so2 and hcl on the contrary low equilibrium temperatures were calculated for the surire fluids 200 c suggesting interactions of deep originated fluids with meteoric water at shallow depth shallow low temperature aquifers mask any signal of deep fluids in the pampa lirima and torta de tocorcupi thermal discharges despite the variations in temperatures he isotopic compositions and redox conditions of the fluid reservoirs consistently indicate a significant contribution from magmatic degassing although geophysical studies are necessary to better constrain the geothermal potential of northern chile the geothermometric estimations carried out in the present study indicate that el tatio pampa apacheta surire and puchuldiza tuja can be regarded as the most promising areas and deserve more detailed geological investigations

calcareous nannofossils and mesozoic oceanic anoxic events abstract twenty five years ago mesozoic oceanic anoxic events oaes were documented and formalised as intervals of widespread to global deposition of organic matter the toarcian early aptian oae1a and latest cenomanian oae2 oaes are truly global in nature commonly carbonate poor and typically represented by organic carbon rich black shales in some areas these oaes are also characterised by abundant radiolarian sands and silts they are associated with negative and positive excursions in the 87sr 86sr record in addition to large global carbon isotope anomalies in carbonate and or organic matter caused by a major perturbation of the global carbon budget increased rates of volcanism during the formation of the ontong java and manihiki and caribbean plates and the karoo ferrar traps are believed to have caused the geological responses associated with oae1a oae2 and the toarcian oae respectively excess volcanogenic co2 in the atmosphere most probably turned the climate into a greenhouse mode accelerating continental weathering and increasing nutrient content in oceanic surface waters via river run off higher fertility in the global ocean was also probably triggered directly by submarine igneous events that introduced enormous quantities of biolimiting metals within hydrothermal plumes because mesozoic oaes are often represented by carbonate poor sediments quantitative studies of calcareous nannofossils have been applied to explore a the causes and effects of igneous tectonic events and climate changes relative to nannofloral increases and crises as well as b dissolution events and c diagenetic modifications characterization of calcareous nannofloras in oae intervals can improve our understanding of the marine ecosystem and biological processes such as photosynthesis biological pump and biomineralisation carbonate pump that affect the organic and inorganic carbon cycle as well as adsorption of atmospheric co2 in the oceans types and rates of nannoplankton production and evolution are interpreted to trace the impact of major palaeoceanographic and palaeoclimatic events in selected sections it has been documented that calcareous nannofloras rapidly reacted to new conditions of fertility and higher pco2 by drastically reducing calcification as in the modern oceans during oaes the increase of nutrients and atmospheric co2 induced higher abundances of nannoplankton producing small placoliths and inhibited the deep photic zone nannoconids and schizosphaerellids similarly to the nannoconid crisis preceding deposition of the early aptian oae1a black shales a schizosphaerellid crisis is detected prior to the toarcian oae both oaes are further characterised by a rapid nannofloral speciation beginning approximately 1 5 myr before the oae but without extinctions global changes during the latest cenomanian oae 2 exerted different influences on calcareous nannoplankton that experienced a turnover due to most extreme environmental conditions this event in fact was a time of extinctions followed by originations within calcareous nannofossils precise timing of the events before during and after oae1a oae2 and the toarcian oae indicates that they were intervals of enhanced oceanic productivity and that anoxia dysoxia post dated biotic changes