synergies in elemental mobility during weathering of tetrahedrite cu fe zn 12 sb as 4s13 field observations electron microscopy isotopes of cu c o radiometric dating and water geochemistry abstract tetrahedrite cu fe zn 12 sb as 4s13 is commonly present in many ore deposits and may be transferred to mining waste here we describe the behavior of all elements in tetrahedrite during oxidative dissolution in a natural oxidation zone at piesky slovakia this being a long term analogue of weathering of tetrahedrite rich mining wastes electron microprobe work identified initial early advanced and mature stages of weathering the initial stages include formation of secondary covellite and chalcocite the following stages only oxidic products divided into greenish masses and brown veinlets both of them are nanocrystalline mixtures of minerals the masses are cu sb as rich and consist of a nanocrystalline pyrochlore phase the veinlets are fe sb as rich and contain tripuhyite goethite and pyrochlores quantitative elemental budgets show that some elements zn s ni co are rapidly lost whereas others especially cu and as are retained and form copper arsenates in the mature stages of weathering about 10 as and almost 50 of sb are lost during weathering likely released into water some sb is stored in secondary minerals such as camerolaite cualstibite or tripuhyite light carbon isotopic composition 13c down to 11 1 document significant biological contribution for c in the secondary minerals copper isotopes become progressively heavier during weathering from initial 65cu of 2 45 in tetrahedrite up to 4 3 in some azurite samples but 6 3 in covellite and chalcocite documenting cyclic removal of light copper isotopes into covellite and chalcocite the observation of elemental synergies during weathering of tetrahedrite shows that the solubility and mobility of as is controlled by copper arsenates not by iron oxides in an environment rich in tetrahedrite but poor in pyrite antimony another element of environmental concern is mostly released into water and creates low concentration anomalies in stream sediments and soils

an alternative model for positive shifts in shallow marine carbonate 13c and 18o positive shifts in global seawater d 13 cdic are related to changes in the ratio of organic relative to inorganic carbon burial in oceanic basins whereas factors such as climatic cooling and the accumulation of polar ice are known to cause positive shifts in d 18 o here an alternative model is proposed for the formation of local positive isotope shifts in shallow marine settings the model involves geochemically altered platform top water masses and the effects of early meteoric diagenesis on carbonate isotopic composition both mechanisms are active on modern sub tropical carbonate platforms and result in low carbonate d 13 ca ndd 18 o relative to typical oceanic values during high amplitude transgressive events the impact of isotopically light meteoric fluids on the carbonate geochemistry is much reduced and 13 c depleted platform top water mixes with open oceanic water masses having higher isotope values both factors are recorded as a transient increase in carbonate 13 c and 18 o relative to low background values these processes must be taken into consideration when interpreting the geochemical record of ancient epeiric seas

origin of atoll dolomites distinguished by geochemistry and crystal chemistry kita daito jima northern philippine sea abstract kita daito jima is a carbonate island located at the northwestern region of the philippine sea 25 55 6 57 6 n 131 16 9 19 8 e dolomites extend from the island surface to a depth of 100 m below the ground surface mbgs strontium isotope stratigraphy indicates that subsurface units c1 0 49 7 mbgs and c2 49 7 103 4 mbgs were dolomitized at 5 5 ma and 2 0 ma respectively and that island surface dolomites are products of dolomitization at 1 6 2 0 ma x ray diffraction analysis indicates that the island surface and borehole dolomites comprise variable mixtures of four and three dolomite crystal phases respectively each of these phases is distinguished by a different ca and mg content three textural types can be recognized in the kita daito jima dolomites fabric preserving crystalline nonmimetic cnm crystalline mimetic cm and fabric preserving microsucrosic ms cnm dolomites contain more calcian phases whereas ms dolomites commonly are richer in more stoichiometric phases backscattered electron images indicate that calcian dolomite phases were precipitated earlier than the more stoichiometric dolomite phases and that there is no significant hiatus between the phases although they are diachronous both the island surface and borehole cores dolomites show linear relationships between whole rock 18o composition and mg contents and between whole rock trace element concentrations sr and na and mg contents these covariances result from phase mixing not stoichiometric effects deconvolution of whole rock isotopic and elemental compositions based on the relative abundance of phases reveals that each phase has a distinct chemical and isotopic composition oxygen isotopic compositions of the island surface and borehole dolomites suggest that all dolomite phases formed in seawater and that dolomitization primarily occurred during glacio eustatic sea level lowstands and cooler ocean temperatures

volcanism co2 and palaeoclimate a late jurassic early cretaceous carbon and oxygen isotope record a composite tethyan late jurassic early cretaceous carbon and oxygen isotope curve is presented c isotope data provide information on the evolution and perturbation of the global carbon cycle o isotope data are used as a palaeotemperature proxy in combination with palaeontological information the resulting trends in climate and in palaeoceanography are compared with biocalcification trends and oceanographic conditions favouring or inhibiting biocalcification positive c isotope anomalies in the valanginian and aptian correlate with episodes of increased volcanic activity regarded as a source of excess atmospheric carbon dioxide a major warming pulse accompanies the aptian but not the valanginian c isotope event the observed change in early aptian temperatures could have triggered the destabilization of sedimentary gas hydrates and the sudden release of methane to the biosphere as recorded as a distinct negative carbon isotope pulse preceding the positive excursion both c isotope anomalies are accompanied by biocalcification crises that may have been triggered by p co 2 induced changes in climate and in surface water chemistry elevated nutrient levels in river influenced coastal waters and in upwelling regions further weakened marine calcification these conditions contrast with normal trophic conditions prevailing in the latest jurassic and favouring biocalcification the c and o isotope curves record a stable mode of carbon cycling and stable temperatures we conclude that biocalcification is mostly triggered and inhibited by co 2 conditions in the atmosphere ocean system

carbon isotope stratigraphy in shallow water carbonates implications for cretaceous black shale deposition a barremian to albian succession on mount kanala part of a tethyan isolated carbonate platform was investigated for its 13c variations the limestone sequence is composed of a series of peritidal shallowing upward cycles with clear petrographic evidence for strong early diagenetic overprinting related to repeated subaerial exposure despite significant impact of diagenesis the observed changes in 13c can be very well correlated with deep water sections from different ocean basins and shallow water carbonate platforms in the middle east this lends further support to the applicability of 13c variations for stratigraphic purposes in shallow water limestones using the 13c signal time resolution in lower cretaceous platform carbonates can be significantly increased independent of bio zonations often hampered by ecological variability cyclostratigraphic analysis of the aptian part of the section shows that strong positive excursions of the cumulative departure from mean cycle thickness of the peritidal shallowing upward cycles coincide with global positive 13c excursions this and the fact that positive shifts in the 13c record are preserved within shallow water limestones provide evidence that black shale accumulation in the ocean basins occurred during sea level rise and flooding of platform tops integration of carbon isotope cyclo and sequence stratigraphic results from different carbonate platforms indicate that strong positive global 13c shifts and concurrent organic carbon burial during black shale deposition are ultimately caused by rapid rises of eustatic sea level hence the rate of change of eustatic sea level is considered to play a crucial role in black shale accumulation in the global ocean basins during the cretaceous

transient global cooling at the onset of early aptian oceanic anoxic event oae 1a the onset of the early aptian oceanic anoxic event oae 1a ca 120 ma coincided with a major perturbation of the carbon cycle which is reflected in the sedimentary carbon isotope record triggering mechanisms duration and climatic repercussions of this episode of accelerated organic matter burial remain poorly constrained here we present millennial scale bulk rock carbon and oxygen isotope data from a marly subtropical intrashelf basin la bedoule southeast france with unusually high sedimentation rates which track the onset of oae1a in unprecedented resolution our record reveals that the negative low amplitude delta 13 c excursion preceding oae1a lasted 100 k y implying that enhanced volcanic co 2 emission and or pulsed methane dissociation over a prolonged time span were instrumental in triggering oae1a the main positive carbon isotope shift at the onset of oae1a previously regarded as continuous occurred stepwise over an extended period of 300 k y transient climate cooling during the initial delta 13 c increase probably reflects ephemeral high latitude glaciation triggered by changes in radiative forcing and drawdown of atmospheric co 2

habitats of larger foraminifera on the upper reef slope of sesoko island okinawa japan larger foraminifera living in the upper 50 m in front of the fringing coral reef northwest off sesoko island japan show strong habitat differences this study closely examines the distributions of larger foraminifers and relates these to a number of key environmental factors using rigorous statistical methods since all larger foraminifera house symbiotic algae light attenuation by the water column is the most important limiting factor that must be dealt with wall structures water energy is also countered by test structure the local topography is responsible for different intensities of hydrodynamic forces which are expressed in various substrates mostly coral rubble and coarse grained sand the genus peneroplis very common on the reef flat clearly prefers hardgrounds of the shallowest slope parts down to 30 m while dendritina is restricted to sandy bottoms and avoids the uppermost meters of the slope it can be found down to 50 m at least alveolinella shows a similar depth distribution to dendritina but is common on hard bottom the distribution of parasorites which is restricted to sandy substrates starts at 20 m and extends to 80 m sorites on the other hand was found only on firm substrates between the reef edge and 50 m the same depth distribution was recorded for amphisorus but this genus is not correlated with specific substrates most of the amphistegina species prefer hardgrounds while amphistegina radiata is also common on sand the calcarinids capable of withstanding high water energy are abundant on firm substrates close to the reef edge only baculogypsinoides inhabits deeper parts of the slope on sandy bottom and avoids the shallowest parts sections with hard substrates are settled by heterostegina even down to 80 m although this genus was occasionally found on sandy bottoms nummulites in contrast is restricted to sands between 20 and 70 m operculina starting at 20 m also prefers sandy substrates but rare individuals were detected on coral rubble and macroids

weathering of bi bearing tennantite abstract the tennantite tetrahedrite solid solution series called fahlore cu ag 6cu4 fe zn cu hg cd 2 sb as bi te 4 s se 13 is widespread in many geological environments since it incorporates heavy metals and toxic elements a better understanding of its weathering behaviour and details of its weathering process is important to evaluate environmental risks emerging mainly from the mobilization of as sb bi and local and global metal fluxes in stream waters and oceans in this study weathering of bi rich members of this mineral group was investigated using microscopy empa sem tem la icp ms raman xrd and mla observations reveal a succession of four distinct stages of weathering during stage 1 irregular tubes within fahlore show an assemblage of nm to m sized romeite group minerals tripuhyite crystalline cu oxides and cu sulfides stage 1 textures and secondary sulfides indicate a low redox potential and a low fluid rock ratio typical of cementation zones mass balance calculations show that during this stage all zn and the majority of as and s are released to the weathering fluids bismuth is immobile in this stage and sb and fe are immobile if bi is sufficiently available from fahlore but both are partly released if the fahlore did not contain sufficient bi during stage 2 amorphous and nano crystalline arsenates replace fahlore as weathering fronts such assemblages indicate a higher redox potential than in stage 1 typical for oxidation zones mass balance calculations reveal that zn sb s and partially cu are lost arsenic and bi are immobile stage 3 occurs only locally dissolving former weathering stages and or precipitating amorphous cu arsenates silicates reflecting processes in micro compartments not characteristic for the general weathering process stage 4 is characterized by the formation of crystalline bi cu ba ca or al bearing arsenates and cu carbonates spatially independent of the precursor fahlore copper and as originate from older weathering assemblages whereas many other elements are derived externally ca ba al this stage reflects the increasing importance of the local host rock and gangue mineralogy as it is typical in near surface environments of oxidation zones or on mine dumps where elements are highly mobile and a high fluid rock ratio prevails gossan mineralization the temporal evolution of fahlore weathering textures reflects the transition from fresh ore to cementation zone oxidation zone and gossan assemblages in one hand specimen thus one fahlore grain can record the uplift and erosion and the increasing fluid rock interaction of a weathered ore deposit with time tube like textures similar to the ones observed in stage 1 have been reported from other weathering environments and from a variety of element oxide arsenide and sulfide phases they also were produced during experimental work in ilmenite this is clear evidence that the diffusive process during the first contact with alteration fluids is a basic physical process and that it is not only valid for fahlore the importance of bi to stabilize sb bearing supergene phases and thereby for the immobilization of toxic sb shown in the present work may stimulate further investigations on the environmental immobilization of toxic elements by companion metals during weathering processes

a platform to basin transition for lower aptian carbonates shuaiba formation of the northeastern jebel akhdar sultanate of oman abstract the platform to basin transition of the lower aptian shuaiba carbonate platform throughout a large part of the arabian peninsula has hitherto mainly been documented from subsurface data and has widely been regarded as having been progradational in northeastern jebel akhdar however the shuaiba platform did not prograde and was scarp bounded early lithification accounts for the rigid nature of the scarp a biological framework being nearly absent early exposure surfaces neptunian dykes sills internal breccias and other sediment features as well as the geographic coincidence of the platform scarp with older and younger scarps suggest a tectonic control of margin morphology and dynamics a contemporaneous peak of allodapic sediments and reactivation of older basement structures in adjacent basins also tends to indicate the importance of structural influence on platform margin organization

timing and magnitude of early aptian extreme warming unraveling primary δ18o variation in indurated pelagic carbonates at deep sea drilling project site 463 central pacific ocean abstract in order to elucidate early aptian marine paleotemperature evolution across the period of enhanced organic carbon corg burial oceanic anoxic event oae 1a stable isotope analyses were performed on pelagic limestones at deep sea drilling project site 463 central pacific ocean the 18o data exhibit a distinct anomaly by 2 spanning the oae 1a interval i e a 6 m thick phytoplanktonic corg rich unit constrained by magneto bio and 13c stratigraphy elucidation of paleotemperature significance of the 18o shift is made by taking account of recent sr ca evidence at the same section which revealed that geochemical signals in carbonate poor lithologies are relatively unaltered against burial diagenesis by discriminating 18o values from carbonate poor samples caco3 contents 5 30 wt it appears that an abrupt rise in sea surface temperatures ssts by 8 c 1 7 shift in 18o occurred immediately before oae 1a whereas a cooling mode likely prevailed during the peak corg burial in terms of its stratigraphic relationship as to the corg rich interval and to a pronounced negative 13c excursion as well as its timescale the observed sst rise resembles those associated with the paleocene eocene thermal maximum and more strikingly jurassic toarcian oae this observation is consistent with the hypothesis that these paleoenvironmental events were driven by a common causal mechanism which was likely initiated by the greenhouse effect via massive release of ch4 or co2 from the isotopically light carbon reservoir and terminated by a negative productivity feedback

significant increases in global weathering during oceanic anoxic events 1a and 2 indicated by calcium isotopes abstract calcium isotope ratios 44 42ca were measured in carbonate rich sedimentary sections deposited during oceanic anoxic events 1a early aptian and 2 cenomanian turonian in sections from resolution guyot mid pacific mountains coppitella italy and the english chalk at eastbourne and south ferriby uk a negative excursion in 44 42ca of 0 20 and 0 10 is observed for the two events these 44 42ca excursions occur at the same stratigraphic level as the carbon isotope excursions that define the events but do not correlate with evidence for carbonate dissolution or lithological changes diagenetic and temperature effects on the calcium isotope ratios can be discounted leaving changes in global seawater composition as the most probable explanation for 44 42ca changes in four different carbonate sections an oceanic box model with coupled strontium and calcium isotope systems indicates that a global weathering increase is likely to be the dominant driver of transient excursions in calcium isotope ratios the model suggests that contributions from hydrothermal activity and carbonate dissolution are too small and short lived to affect the oceanic calcium reservoir measurably a modelled increase in weathering flux on the order of three times the modern flux combined with increased hydrothermal activity due to formation of the ontong java plateau oae1a and caribbean plateau oae2 can produce trends in both calcium and strontium isotopes that match the signals recorded in the carbonate sections this study presents the first major element record of a weathering response to oceanic anoxic events

rudists as gregarious sediment dwellers not reef builders on cretaceous carbonate platforms abstract it has sometimes been claimed that rudist bivalves competitively displaced corals from reef frameworks during the cretaceous this hypothesis combines two assertions 1 that the autecology of rudists was convergent with that of reef building corals and 2 that rudist formations commonly developed as reefs we dispute both assertions and thus reject the hypothesis of competitive displacement we argue instead that mobile sediments rather than frameworks dominated the margins and tops of most of the extensive carbonate platforms of the period and that it was on these non reefal biotopes that the rudists flourished definitions of reefs tend to combine two major elements 1 a robust biogenic framework with accompanying sedimentary and diagenetic components and 2 topographical relief such definitions are clearly rooted in recent coral reefs in which endosymbiotic zooxanthellae permit the extensive growth of colonial coral frameworks in shallow but relatively nutrient poor waters coralline algae and cementation may contribute significantly to the growth of rigid structures and topography is largely the legacy of pleistocene changes in sea level in rudist formations in contrast individual rudist congregations are volumetrically limited relative to sediment they are often loosely constructed and they evidently showed little if any original relief tabular and small lenticular units predominate these differences in structure and palaeoenvironmental situation between rudist and modern coralgal associations reflect the different autecologies of the constituent organisms the clonal growth of corals predisposes them to the development of frameworks projecting above the sediment surface herein termed superstratal growth by contrast the aclonal development of rudists was better suited to the opportunistic occupation of a variety of temporarily available substrata by large numbers of individuals in particular elevator rudists in which the entire commissure exhibited upward growth evidently grew with their shells largely embedded in and supported by the ambient sediment herein termed constratal growth moreover the tolerances and growth responses of rudists to such factors as water turbidity nutrients and current regime were quite different from those of the majority of reef building corals despite repeated assertions in the literature that rudists possessed zooxanthellae only a few species show any evidence for such a symbiosis and other evidence suggests that most lacked them in view of these differences in their preferred biotopes competition between rudists and corals is doubtful even though members of both groups co occur in many areas the relative decline of coral frameworks in the cretaceous was thus probably independently caused

early aptian paleoenvironmental evolution of the bab basin at the southern neo tethys margin response to global carbon cycle perturbations across ocean anoxic event 1a 1 lower aptian carbonates in the bab basin at the southern neo tethys margin record significant environmental changes across oceanic anoxic event 1a oae1a a long lasting negative shift of carbon isotope ratios 13c associated with a distinct decrease in oxygen isotope ratios 18o in orbitolinid rich carbonates characterizes the onset of oae1a livello selli supporting a hypothesis that a long lasting volcanic co2 emission is the main cause of oae1a inducing global warming a bloom of microencrusters lithocodium and bacinella across the proto bab basin occurred synchronously at the beginning of the subsequent positive 13c excursion responding to the global carbon cycle perturbations the carbonates formed during the oae1a show higher strontium isotope ratios 87sr 86sr compared with those of global seawater this was likely caused by a local influx of isotopically heavier strontium along with nutrients into the proto bab basin these biotic proliferations were triggered by an increased nutrient supply induced by intensified continental weathering due to the global warming suggested by the increase in 18o values spatial variations in the 13c values among sites in the bab basin and its surrounding platform are related to local environmental factors such as the degree of mixing of basin water with ocean water and local removal of 12c by metabolic activity at the platform top the 13c profile of the studied core indicates global removal of organic carbon of oae1a began during the early stage of the second order transgression and lasted until the early stage of the highstand after the oae1a the livello selli corresponds to the early stage of this transgression

criteria for the retention of original seawater 87sr86sr in ancient shelf limestones abstract a suite of 40 pennsylvanian and permian shelf limestones from kansas and oklahoma has been analyzed for major and trace elements and for c o and sr isotopes the chemistry and c and o isotope ratios were compared to the difference between the measured 87 sr 86 sr and original seawater ratio concentrations of mn sr and fe varied most systematically with the change in the seawater sr ratio all samples containing 700 ppm mn yielded altered ratios fe and sr contents were also found to have a less well defined correlation with the retention of the original sr ratio all limestones with 900 ppm sr and 20 of 22 samples with a sr mn 2 0 yielded correct ratios the geochemical guidelines were applied to the chemical and isotopic results from 76 shelf limestones mostly of pennsylvanian age from texas and oklahoma more than 92 of the samples that contain sr mn 2 0 yielded correct seawater ratios every sample with sr mn 2 0 retained the original seawater ratio

phosphogenesis carbon isotope stratigraphy and carbonate platform evolution along the lower cretaceous northern tethyan margin we distinguish three different stages in the evolution of the tithonian late jurassic to aptian early cretaceous northern tethyan carbonate platform 1 carbonate production in the coral oolite mode late tithonian to early valanginian early barremian to early aptian 2 carbonate production in the crinoid bryozoan mode early valanginian haute rivian late aptian and 3 platform retrogradation and destruction condensation and phosphogenesis that is platform drowning early valanginian to early hauterivian middle hauterivian late hauterivian to early barremian early to early late aptian and latest aptian to earliest albian transitions from the coral oolite mode to the crinoid bryozoan mode and consequently to platform drowning may have been driven by increases in nutrient levels on the shelf phases of relative sea level rise in times of carbonate production in the coral oolite mode are named constructive because of the observed platform regeneration following phases of widespread emersion during late sea level highstands in contrast phases of relative sea level rise in times of platform drowning are termed destructive the 13 c stratigraphies obtained from valanginian hauterivian and aptian albian hemipelagic successions beyond the platform correlate well with the early cretaceous pelagic 13 c record positive excursions in the pelagic 13 c record correspond in time to episodes of platform drowning this suggests the existence of a coupling mechanism between changes in the global carbon cycle and platform drowning in our view the early cretaceous crises in carbonate platform growth were the consequence of reinforced greenhouse conditions which may have been triggered by episodes of extensive flood basalt volcanism strong greenhouse conditions may have induced the following chain of feedback mechanisms enabling the biosphere to return to normal conditions climate warming sea level rise accelerated water cycle intensified weathering nutrient mobilization platform destruction increased productivity increased phosphogenesis and carbon burial weakened greenhouse conditions

a volcanic co2 pulse triggered the cretaceous oceanic anoxic event 1a and a biocalcification crisis the aptian oceanic anoxic event 1a oae1a ca 120 ma ago is one of the most prominent of a series of geologically brief intervals in the cretaceous characterized by the deposition of organic carbon rich sediments oaes reflect major perturbations in the global carbon cycle evidenced by sedimentary carbon isotope records however the triggering mechanisms for oaes remain controversial here we present a bulk rock and molecular marine and terrestrial bio markers c isotope record at unprecedented time resolution from the cismon section of northern italy that shows that oae1a conditions were reached over a period of several thousands of years through a stepwise perturbation of the carbon cycle the documented sequence of events is most compatible with a trigger associated with increased co 2 emissions possibly leading to a doubling of p co 2 which in turn caused larger c isotope fractionation in marine and terrestrial organisms and a major biotic crisis in the calcareous nannoplankton our data also show that a release of isotopically light carbon from partial methane hydrate dissociation probably played a minor role in the oae1a carbon cycle perturbation

evolution patterns of radiolaria and organic matter variations a new approach to identify sea level changes in mid cretaceous pelagic environments the relation between sea level changes plankton productivity and evolution as well as the occurrence of anoxic sediments provides an interesting avenue of paleooceanographic research in this context we examined mid cretaceous radiolarian faunas carbonate isotopic and organic matter type data of deep sea drilling project and ocean drilling program cores from the north atlantic and samples from outcrops of the western tethys from central and northern italy former studies indicate that an expansion of the oxygen minimum zone caused plankton extinctions at the cenomanian turonian boundary an expanded oxygen minimum zone would destroy deeper habitats of planktic foraminifera causing the extinction of deeper dwelling forms although this model is well established for the cenomanian turonian boundary not much is known about the causes of extinctions and radiations during the entire mid cretaceous aptian turonian we demonstrate that the dimension of the oxygen minimum zone which depends on the relative sea level and the corresponding nutrient supply causes the complex pattern of evolution and radiation of planktic protozoa and the sedimentation of black shales in the mid cretaceous this new depositional model allows correlation of micropaleontologic data and different types of black shales in the pelagic realm within a sequence stratigraphic framework

major palaeoenvironmental perturbation in an early aptian carbonate platform prelude of the oceanic anoxic event 1a the early aptian oceanic anoxic event oae 1a was characterized by intensified greenhouse climate conditions widespread accumulation of organic deposits in open marine settings major perturbations in the c cycle and a generalized increase in terrestrial runoff sedimentological diagenetic and chemostratigraphic analyses of lower aptian platform carbonates from the north cantabrian basin n spain illustrate the regional impact and effects of those global conditions on shallow marine environments the studied interval outlines four stages of platform evolution stage 1 earliest bedoulian is defined by an initial rapid marine transgression that led to deposition of shallow water oligotrophic photozoan skeletal assemblages and by a later interval of subaerial exposure stage 2 early bedoulian starts with a rapid transgression followed by deposition of grainstones that yield heterozoan assemblages more typical of mesotrophic conditions along with ferruginized oolites stage 3 early bedoulian is defined by the drowning of the carbonate platform and subsequent deposition of open marine marls which are thought to represent the local expression of the oae 1a finally stage 4 shows the return of shallow water photozoan carbonate sedimentation the carbonate o and c stable isotope records have revealed prominent negative excursions during deposition of the marly interval of the stage 3 which may be associated with the important global changes that occurred at the onset of the oae 1a the change in skeletal assemblages that preceded the isotopic excursions and the platform drowning documents conditions of environmental stress caused by a combination of local and global factors the global change coupled with increased basin subsidence triggered the drowning of the platform by progressive reduction of the growth potential of the carbonate factory

provenance of the north pacific sediments and process of source material transport as derived from rb sr isotopic systematics abstract rb sr isotopic systematics of 111 samples of sediments in nine cores from the north pacific of quaternary and pliocene ages have been investigated they provide information on the provenance the process of particle transport and temporal variation in the flux of source material the rb sr isotopic systematics of the core sediments show well correlated pseudo isochrons the pseudo isochrons reflect the mixing of two types of material i e the asian continental material with high 87 rb 86 sr ratios 4 5 6 5 and high 87 sr 86 sr ratios 0 723 0 727 and the volcanic material with low 87 rb 86 sr ratios and low 87 sr 86 sr ratios from island arc volcanics such as the izu ogasawara mariana and the japanese islands and oceanic islands such as the hawaiian islands 0 0 2 0 0 703 0 708 the clearness of the pseudo isochrons implies that the rb sr isotopic composition of the weathering products derived from the asian continental crust is extremely homogenized the fine fraction a few m with a high 87 rb 86 sr ratio 5 0 6 5 is widely transported into the north pacific by the middle latitude westerlies and contributes largely to pelagic sediments the coarser fraction with a lower 87 rb 86 sr ratio

lead isotopic record of barremian aptian marine sediments implications for large igneous provinces and the aptian climatic crisis we present initial isotopic ratios of lead for early cretaceous barremian aptian sections from shatsky rise pacific and gorgo a cerbara italy our pb isotopic data track an interval representing oceanic anoxic event oae 1a which is characterized by quasi global deposition of organic carbon rich black shale pb isotopic compositions of sediments from shatsky rise decrease at the end of barremian time from radiogenic continental values to unradiogenic values and subsequently remained less radiogenic until the end of early aptian time we explain the isotopic shift by a significant increase in supply rate of unradiogenic pb most likely due to massive volcanism in contrast the pb isotopic compositions from the italian section which was situated at the western end of tethys are mostly identical to those of upper continental crust showing no significant change in supply rate of unradiogenic pb the discrepancy between two sites is attributed to quiescent deep submarine eruptions of pacific large igneous provinces lips such as the ontong java plateau ojp which severely limited dispersion of pb carrying particles out of the pacific ocean published os isotopic data from the italian section indicate two episodes of massive eruptions of ojp or contemporaneous manihiki and hikurangi plateaus starting from earliest aptian time slightly later than that indicated by the sedimentary pb isotopic record from shatsky rise differences in isotopic variations between pb and os likely reflect differences in their chemical behaviors in the oceans i e pb isotopic compositions would have varied in response to local or regional changes in sediment provenances whereas large scale changes in os inputs are required to explain variations in seawater os isotopic compositions our pb isotopic data together with the published os isotopic record provide new evidence for the eruptive history of ojp together with contemporaneous pacific plateaus and its environmental consequences starting from end barremian time and extending through early aptian time

abstract sequence stratigraphic framework of shu aiba formation shaybah field saudi arabia a basis for reservoir development of an aptian carbonate ramp complex

morphological patterns of aptian lithocodium bacinella geobodies relation to environment and scale lithocodium aggregatum and bacinella irregularis are now extinct shallow marine life forms of unknown taxonomic origin forming part of the tropical platform biota during much of the mesozoic these organisms experienced bloom periods and temporarily replaced rudist coral assemblages during parts of the early aptian within the limitations of time resolution this out of balance facies is coeval with the oceanic anoxic event 1a related black shale deposition in oceanic basins but the triggering factors remain poorly understood here a platform wide comparison of lithocodium bacinella geobodies and morphotypes from the sultanate of oman is presented and placed in its environmental bathymetric and physiographic context lithocodium bacinella geobodies reach from kilometre scale superstructures to delicate centimetre sized growth forms clearly scale matters and care must be taken when drawing conclusions based on spatially limited observational data whilst the factors that cause lithocodium bacinella expansion should probably be considered in a global context regional to local factors affected growth patterns in a more predictable manner here the unresolved taxonomic relationship remains the main obstacle in any attempt to unravel the response of lithocodium bacinella to specific or interlinked environmental parameters as different organisms respond differently to changing environment acknowledging these limitations the following tentative patterns are observed i lithocodium bacinella tolerated a wide range of hydrodynamic levels and responded to differences in energy level or physiographic settings margin intrashelf basin inner platform by obtaining characteristic growth forms ii lithocodium bacinella favoured low sediment input but had the ability to react to higher sedimentation rates by enhanced upward growth a feature perhaps pointing to a phototrophic metabolism circumstantial evidence for continuous growth within the upper sediment column is debated iii the availability of accommodation space had a direct influence on the maximum size of geobodies formed iv fluctuating nutrient levels and sea water alkalinity may have affected the growth potential of lithocodium bacinella understanding the relationship between lithocodium bacinella morphogenesis on a wide range of scales and local environmental parameters allows for better prediction of the spatial distribution of reservoir properties and also results in an improved interpretation of palaeoenvironments this study might represent a useful first step in this direction

a mineralogical geochemical and microbiogical assessment of the antimony and arsenic rich neutral mine drainage tailings near pezinok slovakia the mineralogical composition of mining wastes deposited in voluminous tailing impoundments around the world is the key factor that controls retention and release of pollutants here we report a detailed mineralogical geochemical and microbiological investigation of two tailing impoundments near the town of pezinok slovakia the primary objective of this study was the mineralogy that formed in the impoundment after the deposition of the tailings so called tertiary minerals tertiary minerals include oxyhydroxides of fe sb as ca and are present as grains and as rims on primary ore minerals x ray microdiffraction data show that the iron oxyhydroxides with abundant as are x ray amorphous the limiting lowest fe as wt wt ratio in this material is 1 5 beyond this ratio the hydrous ferric oxide does not retain arsenic the grains with less as and little to moderate amounts of sb are goethite the grains where sb dominates over fe are poorly crystalline tripuhyite fesbo4 even the most heavily contaminated samples up to 29 wt as2o5 are populated with diverse communities of microorganisms including typical arsenic resistant heterotrophic species as well as iron reducers and sulfur oxidizers several recovered clones cluster within phylogenetic groups that are solely based on environmental sequences and do not contain a single cultivated species thus calling for more work on such extreme environments

toward an orbital chronology for the early aptian oceanic anoxic event oae1a 120 ma abstract the early aptian oceanic anoxic event oae1a 120 ma represents a geologically brief time interval in the mid cretaceous greenhouse world that is characterized by increased organic carbon accumulation in marine sediments sudden biotic changes and abrupt carbon isotope excursions indicative of significant perturbations to global carbon cycling the brevity of these drastic environmental changes

microfacies biostratigraphy and geochemistry of the hemipelagic barremian aptian in north central tunisia influence of the oae 1a on the southern tethys margin upper barremian lower upper aptian hemipelagic deposits of the hamada formation in the djebel serdj area north central tunisia were studied in detail with regard to microfacies biostratigraphy 13 c stratigraphy and geochemistry our data provide insights into the palaeoenvironmental evolution and sea level fluctuations of the tunisian shelf the unusually expanded deposits consist of mud wacke and packstones which reflect mid and outer ramp depositional environments planktonic foraminifer and 13 c stratigraphy allowed us to establish a detailed time frame and the recognition of the lower aptian oceanic anoxic event 1a oae 1a as well as time equivalent deposits of shallowmarine carbonate platform drowning based on our microfacies studies we subdivide the studied sections into four genetic intervals a pre oae 1a interval an oae 1a and platform drowning equivalent interval and a post platform drowning interval we present a 3rd order sea level curve for the tunisian shelf deriving from the results of our microfacies studies deposits of the oae 1a in the sections investigated are characterised by bioclastic wacke and packstones with high abundances of poorly preserved radiolarians and moderately to well preserved planktonic foraminifers suggesting a transgression and an eutrophication of the upper water column scarceness of benthic macrofossils low abundances of small benthic foraminifers and ostracods possibly suggest dysoxic conditions at the seafloor mudstones of the platform drowning time equivalent deposits directly overlying the oae 1a are partly showing a pronounced drop in carbonate content and are scarce of macrofossils 2008 elsevier b v all rights reserved

depletion of 13c in seawater σc02 on modern carbonate platforms significance for the carbon isotopic record of carbonates seawater co2 from modern carbonate platforms bahama banks and florida is depleted in 13c by as much as 4 relative to open ocean water depletion in 13c is caused by isotopically light co2 input from respiration of marine and terrestrial organic matter during water mass residence on the bank as such depletion in 13c is related to changes in water chemistry driven by evaporation freshwater discharge and caco3 withdrawal deviation of modern platform seawater 13c values away from those of surface seawater suggests that 13c values of ancient cratonic carbonate must be cautiously interpreted initial depositional environment as well as alteration during diagenesis must be considered in extracting valid secular trends for oceanic 13c variation

palaeoceanographic significance of the tethyan livello selli early aptian from the hybla formation northwestern sicily biostratigraphy and high resolution chemostratigraphic records high resolution micropalaeontological and chemostratigraphic records for the hauterivian aptian succession outcropping at calabianca nw sicily provide new insight into the palaeoclimatic and palaeoceanographic evolution of the tethys ocean calcareous nannofossil and planktonic foraminiferal biostratigraphy together with 13c chemostratigraphy allowed the identification of a hiatus in the barremian and a major one including most of the upper aptian the entire lower albian and part of the middle albian the livello selli equivalent was identified on the basis of lithology and well constrained by calcareous plankton biostratigraphy as well as by the 13c curve the multi proxy record from the calabianca section is consistent with previous documentation of tethyan sections and others worldwide early aptian global events such as black shale deposition nannoconid crisis c isotopic negative spike and positive excursion associated with the oae1a increase in abundance of leupoldinids and clavate hedbergellids are superimposed on local regional events being strictly related to climate changes and increased run off based on micropalaeontological results and geochemical proxies ba p v ni the livello selli equivalent is interpreted as a high productivity event associated with variable but overall anoxic dysoxic conditions in the lower water column the onset of new physical chemical and biological conditions in the oceans and of the mid cretaceous greenhouse climate are interpreted as consequences of the superplume episode

the early cretaceous drowning unconformities of the apulia carbonate platform gargano promontory southern italy local fingerprints of global palaeoceanographic events drowning successions which cap carbonate platforms and flanks bear palaeoenvironmental information which is useful for genetic stratigraphy they constitute predictive key markers in regional to global correlations an early cretaceous platform to basin transition has been investigated in apulia southern italy and two drowning unconformities dated as early valanginian and late early aptian have been documented they occur at the base of thick pelagic tongues wedging toward the platform and mark the base of two depositional sequences showing distinct transgressive regressive cycles timing of drowning processes based on biostratigraphy and dynamic stratigraphy allows the correlation of unconformities with global scale palae oceanographic events marked among others by positive spikes of well established 13c curves drowning signatures in the apulia carbonates fit the stratigraphic palaeoecological and possibly geochemical evidence found in global records at the same stratigraphic levels moreover it is proposed that the observed drowning events were caused by palaeoceanographic crises affecting factory productivity

mobility and chemical fate of antimony and arsenic in historic mining environments of the kantishna hills district denali national park and preserve alaska article the kantishnahills miningdistrictofinterioralaska usa locatedwithin denalinational parkandpreserve con tains a number of antimony lode deposits including alaska s historically largest antimony producer the stam pede mine oxidative weathering of sulfidic tailings and waste rock associated with historic mining operations has impacted water quality in the region in the stampede and slate creek watersheds antimony and arsenic concentrations instream waters were as high as 720 g l and 239 g l respectively antimony inall watersam plesispredominantlypresentassb v whereasarsenicwasdetectedinvaryingratiosofas iii andas v based onx rayabsorptionspectroscopy xas measurementsreducedas iii andsb iii wereidentifiedinminewaste materials whereas predominantly oxidized forms as v and sb v were found in downstream sediments elevated antimony concentrations extend for more than 8 km downstream from the antimony lodes whereas arsenic quickly attenuates within 1 5 km the difference between antimony and arsenic aqueous phase specia tion suggests that antimony oxidation is more rapid than arsenic within this system a high correlation is ob served between antimony arsenic and iron concentrations in fine fraction streambed sediments downstream of the source lodes this suggests that sorption and co precipitation with iron hydr oxides are important path ways for the attenuation of antimony and arsenic in these interior alaska watersheds further xas characteriza tion of the downstream sediments corroborates these observations and indicates that antimony is adsorbed to fe oxide phases as inner sphere bi dentate edge and corner sharing complexes the trace element redox states as well as downstream partitioning are mainly controlled by iron speciation based on the strong correlation be tween redox potentials calculated from iron fe ii fe iii and arsenic as iii as v

terrestrial record of methane hydrate dissociation in the early cretaceous reconstruction of changing c isotopic composition of early cretaceous atmospheric co2 from fossilized c3 vascular land plant tissue revealed a brief and striking negative excursion d 25 in atmospheric d 13 c followed by a rapid positive compensation d 15 during the aptian ca 117 ma mass balance calculations show that dissociation of a small amount of methane gas hydrate is the most tenable cause of the negative excursion this would also result in an increased co2 o2 mixing ratio as o2 is consumed during ch4 oxidation to co2 spurring the exponential phase of angiosperm biogeographic expansion

barrier holes and trench application to reduce blast induced vibration in seyitomer coal mine in this research experimental applications have been performed to reduce blast induced vibrations in open pit mines for this purpose artificial discontinuity zones such as barrier holes and trench were opened in a dragline panel of seyitomer lignite enterprise kutahya turkey peak particle velocities in front of and behind them were measured by seismographs in this way their effect against vibration was observed and compared barrier holes were opened 24 m deep through 3 parallel lines and aligned at 1 m spacing on the other hand the trench had 8 m depth and 4 m width during the research 209 measurements were taken belonging to 105 explosions twenty eight explosions were carried out in the barrier holes experiments and 77 explosions were carried out in the trench experiments a decrease in vibration of 14 3 18 5 was obtained behind the barrier holes while a decrease of 24 8 58 1 was provided by the trench

calcareous nannoplankton response to surface water acidification around oceanic anoxic event 1a ocean acidification induced by atmospheric co2 may be a major threat to marine ecosystems particularly to calcareous nannoplankton we show that during the aptian 120 million years ago oceanic anoxic event 1a which resulted from a massive addition of volcanic co2 the morphological features of calcareous nannofossils traced the biological response to acidified surface waters we observe the demise of heavily calcified nannoconids and reduced calcite paleofluxes at the beginning of a pre anoxia calcification crisis ephemeral coccolith dwarfism and malformation represent species specific adjustments to survive lower ph whereas later abundance peaks indicate intermittent alkalinity recovery deepwater acidification occurred with a delay of 25 000 to 30 000 years after the dissolution climax nannoplankton and carbonate recovery developed over 160 000 years under persisting global dysoxia anoxia

a fuzzy logic approach for the estimation of facies from wire line logs a method based on fuzzy logic inference can be used to identify lithological and depositional facies from wire line logs fuzzy logic is inherently well suited to characterizing vague and imperfectly defined knowledge a situation encountered in most geological data it can thus yield models that are simpler and more robust than those based on crisp logic the method is simple easy to comprehend and robust it also generates several confidence measures that can be used to assess the quality of the analysis several enhancements including static and dynamic constraints are discussed the technique is tested here by applying it to predict the depositional facies of a cored well in a marine carbonate environment and comparing the output with the facies derived from core analysis the two show considerable agreement which indicates that this method can be an effective means of predicting the facies of uncored wells from their logs the method has advantages when contrasted with other techniques that rely on multivariate statistics and neural networks compared to those techniques this method is simpler easier to retrain more reproducible noniterative and more computer efficient

absence of major vegetation and palaeoatmospheric pco2 changes associated with oceanic anoxic event 1a early aptian se france the deposition of organic rich sediments during the late early aptian oceanic anoxic event oae 1a has been interpreted to result in a major decrease of palaeoatmospheric co2 concentrations accompanied by significant changes in the terrestrial flora in order to test this hypothesis the oae 1a interval in the vocontian basin se france has been studied with a combined approach including stable carbon isotopes organic geochemistry and palynology to estimate changes in palaeoatmospheric co2 levels across the oae 1a the 13c composition of presumed algal biomarkers low molecular weight n alkanes steranes and of bulk carbonate carbon are used our results yield estimated early aptian carbon dioxide partial pressure pco2 values three to four times the preindustrial level and only a moderate drop across the black shale event this moderate drop in pco2 is supported by palynological results the frequency patterns of climate sensitive sporomorphs incl pteridophyte spores bisaccate pollen and classopollis spp display only minor fluctuations throughout the studied section and indicate relatively stable patterns of terrestrial vegetation during and after formation of the oae 1a black shale the occurrence of a characteristic early aptian carbon isotope pattern across the oae 1a interval permits accurate chemostratigraphic correlation with the well studied livello selli interval of the cismon record n italy the contemporaneous formation of individual black shale layers at both sites indicates that transient episodes of dysoxic anoxic bottom waters prevailed over large areas in the w tethys ocean independent of depositional setting comparison of the palynological data from the two locations displays significant differences in the frequency patterns of bisaccate pollen the contrasting pollen spectra are interpreted to reflect prominent changes in the palaeoceanographic current patterns and or selective sorting due to sea level rise rather than latitudinal shifts of the major floral belts

new constraints upon isotope variation during the early cretaceous barremian cenomanian from the pacific ocean carbon and oxygen isotope data from a succession of cretaceous barremian cenomanian age recovered from the pacific ocean dsdp site 463 are presented the carbon isotope curve reveals a large isotope excursion within the early aptian where 1 3 c values reach 4 8 in the l cabri g ferreolensis foraminifera zone a decrease in 1 3 c values is observed at the base g algerianus zone before a return to more positive values at the top of the g algerianus t bejaouaensis zone the pronounced early aptian positive event is preceded by a large negative isotope excursion confined to the g blowi zone synchronous with this excursion are increased total organic carbon values and increases in mn and fe concentrations integrated biostratigraphic and magnetostratigraphic data together with the carbon isotope profile suggest that the organic rich units of site 463 are correlatable with oceanic anoxic event la the input of isotopically light volcanic co 2 in concert with the intensification and upwelling of intermediate water enriched in 1 2 c could account for the observed trends a potential trigger may have been the destabilization of the water column and the prodigious co 2 emissions associated with hydrothermal activity and the emplacement of the ontong java plateau coupled with faunal evidence the subsequent positive carbon isotope excursion is interpreted to be resulting from high but decreasing productivity and possibly increasing ocean stratification resulting in strong carbon isotopic gradients and 1 3 c enriched surface waters the decrease in 1 3 c within the g algerianus zone is coincident with more positive 1 8 o values if these are interpreted in terms of temperature this interval may be characterized by a period of cooling and possibly a waning of c o r g cycling a return to lower 1 3 c values during the middle albian is considered to be related to the increased influence of upwelling as opposed to a waning of c o r g cycling upwelling introduced isotopically light carbon to the surface arresting the stratified oceanic conditions

impact of early aptian carbon cycle perturbations on evolution of a marine shelf system in the basque cantabrian basin aralar n spain abstract the aptian oceanic anoxic event 1a oae1a ca 120 ma ago is one of the most prominent of a series of geologically brief intervals in the cretaceous reflecting a major perturbation in the global carbon cycle this carbon cycle perturbation is recorded in the c isotope stratigraphy in this study we present a new carbonate and organic carbon isotope record across oae1a from expanded shallow marine sections igaratza and iribas in the basque cantabrian basin n spain the sediments studied were accumulated on a mixed carbonate siliciclastic and carbonate shelf the 13 c carb and 13 c org curves obtained show a pronounced negative spike in the deshayesites weissi zone and a subsequent positive excursion within the newly described d deshayesi d furcata transition zone approximately equivalent to the upper d deshayesi zone of other sections specific changes in facies patterns and a reduction in neritic carbonate production predate the negative c isotope perturbation these changes coincide with global carbonate crises in neritic and pelagic environments corresponding with the beginning of oae1a selli level a condensed interval rich in ammonites is observed this horizon is linked to a major transgression with high biodiversity the ammonite bloom suggests enhanced primary productivity in the surface waters of the basque cantabrian basin at improving environmental conditions for selected biocalcifiers the ultimate recovery of shelf carbonate deposition occurred after oae1a and it coincided in time with the most positive values of the carbon isotope excursion based on carbon isotope stratigraphy it has been deduced that black shales corresponding to selli level are missing in aralar so that anoxia is not recorded in the studied sections of the marine shelf environment an organic rich interval aparein level postdates the early aptian major positive excursion the aparein event should be considered in the future research of oaes

influence of hardpan layers on arsenic mobility in historical gold mine tailings abstract hardpans or cemented layers form by precipitation and cementation of secondary minerals in mine tailings and may act as both physical and chemical barriers precipitation of secondary minerals during weathering of tailings can sequester metal loid s thereby limiting their release to the environment at montague gold mines in nova scotia tailings are partially cemented by the fe arsenate mineral scorodite feaso4 2h2o previous studies have shown that the formation of scorodite can effectively limit aqueous as concentrations due to its relatively low solubility

response of early cretaceous carbonate platforms to changes in atmospheric carbon dioxide levels during the late barremian and early aptian about 120 million years ago intense volcanic degassing and extremely rapid release of methane hydrates contained in marine sediments added high amounts of carbon to the ocean and atmosphere and resulted most probably in rising atmospheric carbon dioxide pressure in order to document the response of the shallow water carbonate producing communities to this pronounced disturbance of the carbon cycle we studied a late barremian to early aptian neritic carbonate succession deposited on the northern tethyan shelf swiss alps the sedimentological and stable carbon and oxygen isotope records of two sections located along a n s transect from proximal to more distal shelf environments were investigated the sediments correspond to outer mid and inner ramp deposits of a homoclinal carbonate ramp vertical facies variations within the two studied sections feature three progradation phases of the platform a highly resolved correlation of the shelf sediments with a pelagic succession from the southern alps northern italy is based on both 13c stratigraphy and biostratigraphy and indicates that the drowning of the helvetic carbonate platform coincided with a pronounced calcification crisis of calcareous nannofossils the biocalcification crisis started before but culminated during the aptian methane event recorded in a negative carbon isotope spike we propose that increased carbon dioxide concentrations in oceans and atmosphere related to volcanic activity and to sudden methane release reduced the marine calcium carbonate oversaturation and the calcification potential of benthic and planktonic organisms carbonate producing shallow water communities on platforms and ramps suffering from additional environmental stress such as extreme temperatures or high nutrient levels could not survive during times of rising sea level and as a consequence carbonate platforms drowned

drastic change in the geographical distribution of the cold water nannofossil coccolithus pelagicus wallich schiller at 2 74 ma in the late pliocene with special reference to glaciation in the arctic ocean abstract we reconstruct the late pliocene to quaternary paleoceanography of the pacific and atlantic oceans based on the geographical distribution of coccolithus pelagicus wallich schiller which has been regarded as a typical cold water species at 2 74 ma the distribution of c pelagicus defines a biogeographical boundary in the marginal seas of mid to high latitude regions of the pacific such as near the japanese islands kuril islands kamchatca peninsula aleutian islands alaska and the northeastern pacific off canada the relative abundance of c pelagicus is greater than 80 in these marginal sea areas in the north pacific and japan sea on the basis of characteristics of the nannofossil assemblages and recent nannoplankton biogeography in the norwegian greenland sea the change in the relative abundance of c pelagicus at 2 74 ma is thought to be the result of the southward migration of most species except c pelagicus with the onset of heavy glaciation the results also indicate that the geographical distribution of c pelagicus changed in three steps at 2 75 1 65 and 1 2 ma and it became rare to barren in low latitude regions

isotope signatures associated with early meteoric diagenesis the environments in which carbonate diagenesis proceeds have been documented in previous studies of holocene and late pleistocene sediments and limestones on barbados west indies variations in the carbon and oxygen isotopic composition of limestones produced during early freshwater diagenesis have been observed in this study to occur in specific patterns six potentially useful patterns emerge when one views stable isotope data within a stratigraphic framework 1 the subaerial exposure surface is characterized by strongly 12c enriched limestones 13c compositions of underlying limestones grow progressively heavier with increasing depth 2 the subaerial exposure surface may also be marked by slight 18o enrichment 3 an abrupt shift in 18o values may differentiate sediments above the exposure surface from those below 4 sediments altered in the marine meteoric mixing zone may be characterized by positive covariance between their 18o and 13c compositions 5 the vadose phreatic boundary may be marked by a sharp increase in 13c values in the seaward portions of a fresh groundwater system and 6 samples contemporaneously altered in a single fresh groundwater system within an areally restricted region should display a narrow range of 18o and a wide range of 13c compositions analysis of samples from five palaeozoic and mesozoic formations which contained petrographic evidence of early freshwater diagenesis showed that isotope patterns similar to those observed in barbados limestones have been preserved in rocks as old as mississippian these isotope patterns could prove to be useful for identifying diagenetically induced porosity trends in carbonate rocks they might be used to identify limestones diagenetically altered in meteoric environments to identify mixing zone cements and dolomites and to trace the regional and vertical distributions of early meteoric groundwater systems in ancient carbonate formations

mineralogical controls on antimony and arsenic mobility during tetrahedrite tennantite weathering at historic mine sites spania dolina piesky and ľubietova svatodusna slovakia the legacy of copper cu mining at spania dolina piesky and ubietova svatodusna central slovakia is waste rock and soil surface waters and groundwaters contaminated with antimony sb arsenic as cu and other metals copper ore is hosted in chalcopyrite cufes 2 and sulfosalt solid solution tetrahedrite tennantite cu 6 cu 4 fe zn 2 sb 4 s 13 cu 6 cu 4 fe zn 2 as 4 s 13 that show wide spread oxidation characteristic by olive green color secondary minerals tetrahedrite tennantite can be a significant source of as and sb contamination synchrotron based xrd xrf and xanes combined with electron microprobe analyses have been used to determine the mineralogy chemical composition element distribution and sb speciation in tetrahedrite tennantite oxidation products in waste rock our results show that the mobility of sb is limited by the formation of oxidation products such as tripuhyite and romeite group mineral containing 36 54 wt sb for samples where the primary mineral chemical composition is close to tetrahedrite end member antimony k edge xanes spectra of these oxidation products indicate that the predominant sb oxidation state is 5 arsenic and cu are also hosted by amorphous phases containing 6 23 wt sb on average and these are intergrown with tripuhyite and romeite antimony in this environment is not very mobile meaning it is not easily released from solid phases to water especially compared to as cu and s for samples where the primary sulfosalt is close to tennantite composition the oxidation products associated with tennantite relicts contain 2 43 wt sb and are amorphous the variable solubility of the secondary minerals that have been identified is expected to influence mobility of sb and as in near surface environment

changes in sedimentary patterns of coastal and deep sea successions from the north atlantic portugal linked to early cretaceous environmental change coastal mixed carbonate siliciclastic and carbonate deposits of late barremian to early aptian age from the lusitanian basin portugal are compared with a deep sea succession odp 641 off the coast of portugal the coastal deposits show an abrupt cessation of rudist dominated carbonate deposition marked by an emersion horizon and followed by the deposition of orbitolinid rich marls during the early aptian the subsequent development of the carbonate platform during the late aptian is masked by a hiatus for this time interval shallow water debris deposits of the deep sea succession odp 641 indicate that carbonate production in shallow water areas resume in the early late aptian carbon isotope stratigraphy in combination with available biostratigraphic data is used for intrabasinal correlation and for the correlation of the portuguese with shallow water successions from switzerland france oman and the pacific the correlation reveals that during the early aptian similar changes in their sedimentary patterns occur at the beginning of a marked negative shift of carbon isotope values associated with the global deposition of organic rich black shales in the deep sea oae 1a in all compared sections rudist dominated carbonate deposition is stopped and followed either by orbitolinid rich deposits the deposition of microbial carbonates or by the drowning of the carbonate platform the comparison shows that the deterioration for carbonate platform growth conditions during the early aptian occurred essentially simultaneously at the various localities during this episode the ocean waters were in a preconditioned state of acidification stressing biocalcifying organisms sea level change combined with local effects like elevated nutrient levels and higher temperatures were probably determining the nature of sedimentary change in shallow water environments during the carbonate crisis in the sections studied in portugal the high abundance of orbitolinids overlying rudist limestones indicates that increased nutrient input may have played an important local role among the factors that caused an overall deterioration for carbonate producers during the late early aptian

orbitolina episodes in carbonate platform evolution the early aptian model from se spain abstract among the orbitolininae palorbitolina lenticularis blumenbach is a common facies marker in upper barremian lower aptian shallow water mesogean deposits and was hitherto ascribed to specific but contrasting paleoenvironments within the carbonate platform facies suites the albacete prebetic area se spain illustrates a model in which the palorbitolina facies spread over the whole platform system the development of the palorbitolina sediments coincided with a transgressive trend at the end of an important terrigenous period this model could also be applied to similar middle crotaceous orbitolina facies

application of sr isotopes to geochemical mapping and provenance analysis the case of aichi prefecture central japan abstract geochemical maps expressing areal distributions of chemical elements in the earth s land surface have been published in several countries in relation to various global environment issues the authors have applied a radiogenic isotope ratio 87 sr 86 sr to geochemical mapping in order to understand the geological origin transportation and dispersion system of chemical elements in the earth s land surface the sr isotope ratio is a useful tracer for distinguishing the geological origin of surficial deposits especially in areas where surface exposure of bedrocks is low because it is not significantly altered by the processes of weathering and transportation most bedrocks in the japanese islands are covered by plants soils and urban areas in this study 142 of 1219 stream sediments 87 sr 86 sr values and the above average presence of granitic rocks in the study area compared with the surface exposure of the japan arc the first factor controlling the distribution of sr isotope ratios is the bedrock distributed around the sampling points regional variation in the 87 sr 86 sr value shows that it is higher in the western and southeastern parts where sedimentary rocks and metamorphic rocks are distributed and that it is lower mainly in the central part where granitic rocks are distributed the 87 rb 86 sr 87 sr 86 sr plot for stream sediments more clearly reveals the differences and similarities of bedrocks in some locations the distribution of sr isotope ratios does not correspond to that of bedrocks on the geological map one reason is the existence of unmapped bedrock for example small intrusive masses of granite the other is fluvial transportation and dispersion the distribution of the isotope ratios suggests that some stream sediments include surficial deposits from a few km upstream application of the sr isotope ratio to geochemical mapping is useful for revealing both the distribution of unexposed bedrocks and the transportation of surficial deposits information on unexposed bedrocks will be expected to contribute to the improvement of geological mapping

estimation of lithologies and depositional facies from wire line logs we approach the problem of identifying facies from well logs through the use of neural networks that perform vector quantization of input data by competitive learning the method can be used in either an unsupervised or supervised manner unsupervised analysis is used to segregate a well into distinct facies classes based on the log behavior supervised analysis is used to identify the facies types present in a certain well by making use of the facies identified from cores in a nearby well the method is suitable for analyzing lithologies and depositional facies of horizontal wells which are almost never cored especially if core data is available for nearby vertical wells both modes are implemented and used for the automatic facies analysis of horizontal wells in saudi arabia in addition to the identification of facies the method is also able to calculate for each analysis confidence measures that are indicative of how well the analysis procedure can identify those facies given uncertainties in the data moreover we can apply constraints derived from human experience and geologic principles to guide the inference process

interactions between environmental change and shallow water carbonate buildup along the northern tethyan margin and their impact on the early cretaceous carbon isotope record 1 the evolution of the early cretaceous northern tethyan carbonate platform was not only influenced by changes in sea level detrital influx and surface water temperature but also by changes in trophic levels we distinguish between phases of carbonate production dominated by oligotrophic photozoan communities and by mesotrophic and eventually colder water heterozoan communities superimposed on this bimodal trend in platform evolution were phases of platform demise for which we provide improved age control based on ammonite biostratigraphy the initial phase of these episodes of platform demise corresponds in time to episodes of oceanic anoxic events and environmental change in general on the basis of a comparison between the temporal changes in an early cretaceous ammonite calibrated d 13 c record from southeastern france and coeval changes in the platform record we suggest that the history of carbon fractionation along the northern tethyan margin was not only influenced by changes in the oceanic carbon cycle such as in the rate of production and preservation of organic and carbonate carbon and in the size of the oceanic dissolved inorganic carbon reservoir but it was also influenced by the above mentioned changes in the ecology and geometry of the adjacent carbonate platform phases of photozoan carbonate production induced positive trends in the hemipelagic carbonate d 13 c record phases of heterozoan carbonate production pushed the d 13 c system toward more negative values platform drowning episodes implied an initial increase in d 13 c values followed by a longerterm decrease in d 13 c values

new perspective on aptian carbon isotope stratigraphy data from δ13c records of terrestrial organic matter carbon isotope analyses were performed on detrital woody materials in aptian mid cretaceous marine sediments of central hokkaido northern japan a positive 13cwood excursion from 25 4 to 21 8 following a remarkable negative isotope shift is recognized in the early aptian and a small positive anomaly is also found in the latest aptian this 13cwood profile is exactly in phase with the 13ccarbonate curve from a pacific guyot when the age of the guyot carbonates is revised using published sr isotope stratigraphies the highly conformable 13c profiles of pacific and hokkaido sections suggest that 13c compositions of aptian marine and terrestrial carbon reservoirs changed simultaneously by the same amplitude within the ocean atmosphere biosphere system fluctuation patterns of tethyan 13ccarbonate curves are slightly different from those of pacific and hokkaido sections such differences in 13c profiles may be attributed to the local paleoceanographic setting of the aptian mediterranean tethys

carbon and oxygen isotopic compositions of modern brachiopod shells from a warm temperate shelf environment sagami bay central japan this study presents carbon 13c and oxygen 18o isotopic compositions of shells of an articulated brachiopod laqueus rubellus living in a warm temperate shelf environment in japan high resolution three dimensional samplings were conducted 1 to clarify variations in the isotopic compositions within a single shell 2 to evaluate offset of the compositions from those of the calcite precipitated in isotopic equilibrium with ambient seawater equilibrium calcite and 3 to specify shell portions that reflect the isotopic compositions of ambient seawater the 13c and 18o values of samples from the secondary shell layer which constitutes the main body of the brachiopod shell are in and or out of those of the equilibrium calcite the isotopic compositions of samples from the outermost part of the secondary shell layer outer surface of the secondary shell layer correlated well with growth rates positive correlations are recognized between the 13c and 18o values of these samples which can be ascribed to a kinetic fractionation effect although limited data on 13c of total dissolved inorganic carbon dic and 18o of seawater at the brachiopod sample site enable only approximate estimates of the 13c and 18o of the equilibrium calcite they are comparable with those of the brachiopod shell the 18o values of samples from the outermost part of the secondary layer along a growth axis of laqueus rubellus are a reliable environmental proxy because they mostly fall in the 18o range for the equilibrium calcite although samples from the inner series of l rubellus are depleted partially enriched in 13c 18o by 0 8 0 3 relative to the equilibrium calcite both isotopic variations are quite small therefore the isotopic compositions in this series would also be useful if the offsets are corrected this study clearly illustrates that although the 13c and 18o of modern brachiopod shells are influenced by the kinetic fractionation effect appropriate selection of species and shell portions reflecting the isotopic compositions of ambient seawater enables the reconstruction of secular variations in 13c or 18o in the oceans throughout geologic time

interpreting carbon isotope excursions carbonates and organic matter abstract variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time but changes in atmospheric pco2 as well interpretations of these types of data are typically rather qualitative a quantitative basis is required to develop a better understanding of changes in the carbon cycle for this purpose we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations each lasting 500 ky i e much longer than the residence times of carbon and phosphorus in the ocean atmosphere system in addition to standard considerations of carbon mass and isotopic fluxes to the ocean atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate carbon to sediments the model incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pco2 the inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial a series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon b with constant b a 50 increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions however the same simulation with b responsive to pco2 changes produces an initial parallel 13 c increase but this is followed by an even greater 13 c enrichment in organic carbon because pco2 falls in response to increased organic carbon burial the counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in 13 c org in addition we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50 increase in volcanic co2 outgassing a 50 increase in weathering rate with coupled phosphate and riverine carbon flux responses a 50 decrease in shale associated organic carbon weathering a 50 decrease in silicate weathering rate and the possible effects of the rise in abundance of c4 plants in the late miocene to recent we compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate and organic carbon records to illustrate how these records might be interpreted in light of the model response

orbital tuning as an inverse problem chronology of the early aptian oceanic anoxic event 1a selli level in the cismon apticore 1 orbital tuning the process of fitting sedimentary cycles to orbital periodicities can estimate with high resolution the timing and duration of key events in the geological record we formulate here orbital tuning as the inverse problem of finding the variation in sedimentation rate that matches sediment cycles with orbital periodicities instead of obtaining a single best estimate we apply a bayesian formulation and define a probability distribution of sedimentation rate variations that result in powerful orbital periodicities by sampling this distribution with a monte carlo method we quantify the uncertainty in the inferred sedimentation rates due to uncertainties in the tuning periods and to components of the sedimentary signal that are unrelated to orbital cycles the method is applied to the chronology of a 30 m interval in the cismon apticore borehole southern alps italy that includes the early aptian oceanic anoxic event 1a selli level estimated to last 1 11 0 11 ma 95 interval the 13c record shows a sudden negative shift of about 1 at the base of the selli level 22 47 ka followed by a recovery to preshift values in 240 ka consistent with a scenario where light carbon is quickly added and then flushed out of the ocean atmosphere system

nannofossils and superplumes the early aptian nannoconid crisis a group of calcareous nannoplankton named nannoconids experienced a crisis in the early aptian and recovered only later in the late aptian after a period of virtual absence although no extinctions occurred the widespread nature of the nannoconid crisis suggests a global causal factor this crisis is recorded within the chiastozygus litterarius nannofossil and globigerinelloides blowi planktonic foraminiferal zones postdates magnetic chronozone m0 by approximately 300 kyr and precedes the oceanic anoxic subevent 1a and associated 13c anomaly by some 40 100 kyr selective dissolution and anoxia cannot explain the crisis because nannoconids are dissolution resistant forms and their crisis clearly precedes the deposition of anoxic sediments at least 1 m y prior to the nannoconid crisis the onset of a nannoplankton speciation event may be the response of nannofloras to a major rise in relative sea level the nannoconid crisis seems to be synchronous with the early aptian volcanic eruptions in the pacific ocean hence calcareous nannoplankton were severely affected by the superplume volcanic episode the coccolithophorid bloom nannoconid crisis was possibly induced by the excessive co2 levels in the atmosphere and or caused by changes in nutrient content of oceanic surface waters fertility was enhanced by rapid turnover of nutrients due to the abnormal volcanic activity and accelerated transfer of nutrients from the continents into the oceans under warm and humid conditions of the mid cretaceous greenhouse climate the nannoconid crisis may represent a competition between phytoplankton groups for nutrients or more likely competition between different calcareous nannoplankton the biologic affinity and mode of life of nannoconus are unknown because there is no modern analog of this genus however comparison of lower cretaceous nannofossil assemblages with modern nannoplankton cummunities suggests that nannoconids like extant florisphaera profunda possibly inhabited the lower photic zone concentrations of nutrients in the upper euphotic zone may have triggered blooms of coccolithophorids and nannoconid depletion this model implies that the nannoconid crisis is the result of an abrupt major change in the structure of surface waters caused directly or indirectly by the superplume the adjustments of the biosphere to the new paleoceanographic and climatic conditions required some 40 100 kyr before changing into abnormally high primary productivity and deposition of organic carbon rich sediments with dinoflagellates outcompeting nannoplankton