oxygenation episodes on the continental shelf of central peru remote forcing and benthic ecosystem response abstract the interplay between the oxygen minimum zone and remotely forced oxygenation episodes determines the fate of the benthic subsystem off the central peruvian coast we analyzed a 12 year monthly time series of oceanographic and benthic parameters at 94 m depth off callao central peru 12 s to analyze i near bottom oxygen level on the continental shelf in relation to dynamic height on the equator 095 w and ii benthic ecosystem responses to oxygen change macrobiotic infauna meiofauna and sulphide oxidizing bacteria thioploca spp shelf oxygenation episodes occurred after equatorial dynamic height increases one month before consistent with the propagation of coastal trapped waves several but not all of these episodes occurred during el ninos the benthic biota responded to oxygenation episodes by undergoing succession through three major ecological states under strong oxygen deficiency or anoxia the sediments were nearly defaunated of macro invertebrates and thioploca was scarce such that nematode biomass dominated the macro and meiobiotas when frequency of oxygenation events reduced the periods of anoxia but the prevailing oxygen range was 10 20 mol l 1 mats of thioploca formed and dominated the biomass finally with frequent and intense 40 mol l 1 oxygenation the sediments were colonized by macrofauna which then dominated biomass the thioploca state evolved during the 2002 2003 weak en while the macrofauna state was developed during the onset of the strong1997 1998 en repeated episodes of strong oxygen deficiency during the summer of 2004 in parallel with the occurrence of red tides in surface waters resulted in the collapse of thioploca mats and development of the nematode state ecological interactions may affect persistence or the transition between benthic ecosystem states

calcareous nannofossil zonation of the jurassic cretaceous boundary interval and correlation with the geomagnetic polarity timescale abstract calcareous nannofossil stratigraphy has been investigated in six european land sections and at two deep sea drilling project sites 391c and 534a ranging from the upper kimmeridgian to the lower valanginian most of the sections contain a continuous record of the jurassic cretaceous boundary interval a time of rapid increase in nannofossil abundance and diversity and allow development of a revised nannofossil zonation scheme for this period numerous nannofossil lineages have been studied in detail and the results help to increase potential stratigraphic resolution in this interval the proposed scheme consists of six zones which are units recognizable in all sections regardless of nannofossil preservation and eleven subzones determinable in all but the most poorly preserved material thirty eight additional biohorizons are proposed based on the stratigraphy of the two dsdp sites these can be accurately established only in moderately well preserved material but spotty occurrences of these taxa in other sections may be stratigraphically useful most of the sections studied have been investigated magnetostratigraphically and the results of this study allow correlation between nannofossil zonation and the geomagnetic polarity time scale magnetostratigraphy indicates that many nannofossil events can be quite precisely determined and are not significantly time transgressive finally the magnetostratigraphic definitions of two stage boundaries are refined the kimmeridgian tithonian and berriasian valanginian boundaries are placed within chrons cm22n and cm15n respectively two new genera faviconus and umbria and seven new species are described umbria granulosa rhagodiscus nebulosus cretarhabdus octofenestratus faviconus multicolumnatus nannoconus infans nannoconus compressus and nannoconus wintereri eight subspecies and three taxonomic emendations are also described

ekman modulation of the sea surface temperature on the eastern south pacific abstract nine years of data 1992 2000 were used to study the evolution of the sea surface temperature sst over the eastern south pacific our analysis shows that the variability in the sst on the interannual scale is attributed mainly to the equatorial el nino la nina events while cooling associated with the wind ekman drift is an important component of the annual cycle the anomalies at the interannual scale show up as a front that parallels the coast at the seasonal scale anomalous warming and cooling of coastal waters is strongly altered by the local effect of the wind driven ekman transport this latter effect is especially significant along the peruvian and northern chilean coast where wind induced upwelling and cooling is out of phase with other important annual forcings i e radiation and annual kelvin waves these local wind effects show up in the time latitude plots as a thinning of the warm water bands along the peruvian coast 10 s y 17 s and a thickening of the bands further south 18 s y 22 s three anomalous events that stand out clearly at the interannual scale are el nino 92 93 la nina 96 and el nino 97 98 their individual evolutions over time and along the coast are very different though the least intense of the three the 92 93 event had the longest duration the 96 event was the shortest in duration and its strongest anomaly occurred around the peruvian coast similar to the warm event of 92 93 the strongest event for the period occurred in 97 98 its warm anomaly showing strongly along the whole latitudinal extent of the study area contrary to what occurs at the seasonal scale the increase on east west ekman transport on the interannual scale seems to be in phase with other relevant cooling and warming mechanisms the interannual ekman anomalous transports are at their maximum near the peruvian northern chilean coast however they do not seem to alter the sst in a significant way a similar situation has been described for sea level data in the california current system i e interannual variability being associated mostly with variability of equatorial origin while seasonal variability is associated to both wind forced local variability and remotely forced variability j geophys res 94 1989 3159

berriasian aptian black shales of the maiolica formation lombardian basin southern alps northern italy local to global events the lower cretaceous maiolica formation represents the classic pelagic succession of the apulian margin of the tethys ocean in the southern alps it consists of white calcilutites with minor marly layers and black shales a multidisciplinary study including lithostratigraphy nannofossil assemblage composition and organic geochemistry was performed on two composite sections in order to characterise the marl shale layers that record production and storage of organic matter om and terrigenous input in the berriasian aptian interval such layers are associated with turbidite deposition and bottom current activity in the late berriasian earliest valanginian late valanginian and early aptian the uppermost hauterivian barremian black shales alternate with pelagic calcilutites forming an interval barren of redeposited layers the quantity of organic carbon increases from the berriasian to the barremian the background composition of the kerogen is continental dominated with varying proportions of marine derived om preservation of om did not necessarily occur under anoxic conditions on the contrary storage of om probably resulted from enhanced terrestrial input of nutrients siliciclastics woody and herbaceous fragments inducing mesotrophic conditions and increased primary productivity higher fertility of surface waters during the late valanginian and early aptian is reflected by distinctive decreases in abundance of oligotrophic nannoconids and increase in abundance of mesotrophic diazomatholithus in the valanginian during the barremian the rhythmic establishment of eutrophic conditions documented by the highest amounts of marine om determined high frequency fluctuations in nannoconid abundance the early aptian nannoconid crisis is interpreted as the result of a major climate change and enhanced primary productivity variations of calcareous nannofloras as well as changes of lithology and om which we describe in the lower cretaceous maiolica formation of the lombardian basin can also be recognised in coeval units from other sites of the apulian side of the tethys similar episodes of siliciclastic and terrestrial om accumulation and major changes in calcareous nannofossils are also recorded in the upper valanginian and lower aptian pelagic sediments of the tethys atlantic and partly pacific oceans such nannofossil variations are coeval with positive excursions of the 13c curve and suggest perturbations of the bio geochemical cycles at a global scale additional minor changes in siliciclastic and terrestrial om accumulation as well as in nannofloras are probably the result of local events strictly related to the physiography and evolution of the tethyan margin

fertilizing potential of volcanic ash in ocean surface water the fertilization potential of newly erupted and well preserved ash from the 2000 hekla eruption in iceland was measured for the first time by flow through experiments as previously shown 1 the north atlantic ocean including the subarctic seas surrounding iceland is the largest net sink of the world s oceans for atmospheric co 2 owing to biological drawdown during summer 2 almost complete consumption of phosphate in chlorophyll rich areas of the north atlantic ocean might limit primary production and 3 in the southern pacific ocean and parts of the equatorial pacific ocean iron might limit primary production we found through laboratory experiments that volcanic ash exposed to seawater initially releases large amounts of adsorbed phosphate 1 7 mmol g 21 h 21 iron 37 0 mmol g 21 h 21 silica 49 5 mmol g 21 h 21 and manganese 1 7 mmol g 21 h 21 dissolution of acid aerosols adsorbed to the surface of the ash caused the high initial release of major and trace elements because of the instantaneous dissolution of adsorbed components when newly erupted volcanic ash comes in contact with the ocean surface water macronutrients and bioactive trace metals are released fast enough to become available to support primary production

morphologic variability of the coccolithophorid calcidiscus leptoporus in the plankton surface sediments and from the early pleistocene abstract on a global scale morphological variability of the extant coccolithophorid calcidiscus leptoporus murray and blackman 1898 loeblich and tappan was investigated in surface sediments and plankton samples and from an early pleistocene time slice 1 8 ma to 1 6 ma in the bivariate space coccolith diameter versus number of rays in the distal shield holocene samples follow a single unimodal morphocline sample means of coccolith size and number of elements group in three clusters i ii and iii which are of biogeographic significance clusters ii and iii coccoliths mean coccolith size of 5 0 m and 20 9 elements and 6 6 m and 25 6 elements respectively are found in a tropical belt extending from 11 n to 17 s with an annual minimum sea surface temperature above 23 5 c cluster i coccoliths 5 8 m 20 7 elements are found in samples outside that belt the distribution of coccoliths in the surface sediments is tentatively interpreted to be a result of mixing to a varying degree of at least three different morphotypes small intermediate and large which were identified in the living plankton and which are separated from each other at 5 m and 8 m mean coccolith diameter respectively a comparison of the surface sediments with the early pleistocene assemblages revealed that between 1 6 ma and 1 8 ma two morphoclines a and b existed the first of which persisted until the holocene in the form of c leptoporus while the second comprises only extinct morphotypes including calcidiscus macintyrei as one end member during the early pleistocene morphocline a was more homogeneous and no clusters were evident morphocline b shows a clear bimodality with a separation of morphotypes at 9 5 m our observations suggest that morphoclines are subsets within the total stratigraphical range of a single species and represent the global variability of that species in a particular time interval morphotypes which belong to a morphocline represent the infra specific variability of that species within the biogeographic and stratigraphic limits of that species

lithium isotope evidence for enhanced silicate weathering during oae 1a early aptian selli event an abrupt rise in temperature forced by a massive input of co2 into the atmosphere is commonly invoked as the main trigger for oceanic anoxic events oaes global warming initiated a cascade of palaeoenvironmental perturbations starting with increased continental weathering and an accelerated hydrological cycle that delivered higher loads of nutrients to coastal areas stimulating biological productivity the end result was widespread anoxia and deposition of black shales the hallmarks of oaes in order to assess the role of weathering as both an oae initiator and terminator via co2 sequestration during the early aptian oae 1a selli event 120 ma the isotopic ratio of lithium isotopes was analysed in three sections of shallow marine carbonates from the pacific and tethyan realms and one basinal pelagic section from the tethyan domain because the isotopic composition of lithium in seawater is largely controlled by continental silicate weathering and high and low temperature alteration of basaltic material a shift to lighter 7li values is expected to characterize oaes the studied sections illustrate this phenomenon 7li values decrease to a minimum coincident with the negative carbon isotope excursion that effectively records the onset of oae 1a a second negative 7li excursion occurs coeval with the minimum in strontium isotopes after the event the striking similarity to the strontium isotope record argues for a common driver the formation and destruction weathering of an oceanic lip could account for the parallel trend in both isotope systems the double spike in lithium isotopes is probably related to a change in weathering congruencies such a chemostratigraphy is consistent with the hypothesis that an increase in silicate weathering in conjunction with organic carbon burial led to drawdown of atmospheric co2 during the early aptian oae 1a

circulation and low frequency variability near the chilean coast remotely forced fluctuations during the 1991 92 el nino results are reported from the first long recording current meter observations over the slope off chile these observations at 308s during the 1991 92 el nino event are analyzed together with observations of currents at a local deep sea site local wind and sea level sea level from the peru and chile coasts and wind temperature and currents from the equatorial pacific mean poleward flow of 12 cm s21 was observed within the peru chile undercurrent over the slope mean flow in the depth range of antarctic intermediate water was not distinguishable from zero in the presence of strong low frequency lf variability which dominated slope currents at all depths the strongest lf fluctuations had periods of about 50 days but periods of 10 and about 5 days were also observed significant local wind forcing of slope currents was only found in the period band 6 10 days and may be related to coastal trapped waves in the atmosphere our analysis shows that free coastal trapped waves in the ocean arriving from the north dominated the lf variability over the shelf and slope off northern and central chile during the 1991 92 el nino event strong 50 day period fluctuations there started their journey about two months earlier and 15 000 km farther up the coastal equatorial waveguide near the date line in the equatorial pacific as equatorial kelvin waves forced by westerly wind events of similar period upon reaching the south american coast these waves forced coastal trapped waves which propagated along the peru coast into the study region likewise a scenario of equatorial trapped waves forcing coastal trapped waves may explain 10 day as well as 6 day and 4 5 day period coastal trapped waves off chile stemming from mixed rossby gravity and inertia gravity waves trapped at the equator since the large 50 day period coastal trapped waves may strongly modify coastal upwelling source water such remotely forced waves may have a significant influence on the pelagic ecosystem off chile at least during el nino events

correlation of early cretaceous carbon isotope stratigraphy and platform drowning events a possible link the early cretaceous carbonate carbon isotope record is marked by three positive high amplitude 1 5 excursions each covering time spans of more than 106 years they are of late valanginian hauterivian and early and late aptian age in a case study along a transect across the western tethys ocean we identified a coincidence between 13c excursions black shale formation and widespread carbonate platform drowning events we conclude that the 13c excursions reflect a change in partitioning of carbon between the organic and carbonate carbon sinks which was triggered by climate induced ecological changes in cretaceous pelagic and neritic environments episodes of intensified greenhouse climate conditions led to an increase in weathering erosion and runoff rates and to elevated nutrient transfer rates from continents into oceans the resulting increase in oceanic nutrient levels favoured marine phytoplankton production and black shale deposition while conditions for carbonate producing biotas became unfavourable partial choking of carbonate production along river influenced coasts resulted in widespread carbonate platform drowning during times of sea level rise in the valanginian and aptian widespread contemporaneous black shale deposits and drowned carbonate platforms therefore reflect the contrasting response of the marine organic and carbonate carbon pumps to nutrient enhanced phytoplankton productivity the change in marine carbon partitioning is mirrored in a shift of the 13c record towards more positive values the transition to the 13c peak values lasted up to several hundred thousand years the peaks of the excursions also covering a time span of up to several hundred thousand years reflect a new stabilisation of the carbon partitioning between carbonate and organic carbon sinks a renewed intensification of carbonate sedimentation under mesotrophic conditions was facilitated by stabilisation of the sea level rise at a high level decreasing 13c values record increasing carbonate carbon burial rates at constant or decreasing organic carbon accumulation rates these changes contributed to the stabilisation of the marine carbon budget and the global carbon cycle up to millions of years after its initial perturbation

evidence for a complex valanginian nannoconid decline in the vocontian basin south east france the early cretaceous is punctuated by widespread biocalcification crises these are characterized by decrease in the carbonate platform growth and in the pelagic realm by a decline in nannoconus relative abundance in the calcareous nannofossil assemblages the valanginian nannoconus decline started before the positive 13c excursion characterizing the weissert event the nannoconid decline is investigated in two sections of the vocontian basin la charce and vergol which are biostratigraphically well constrained and contain wellpreserved calcareous nannofossils absolute and relative abundances of nannoconus show a polyphased decline with a first decrease in the interval from the campylotoxus to the verrucosum ammonite subzones before the positive 13c shift and a second decrease from the end of the peregrinus to the base of the radiatus ammonite zones concomitant with the long term decrease in 13c these two declines are separated by an important increase in the nannoconus abundance from the verrucosum to the peregrinus ammonite subzones concomitant with a slight short term decrease of 13c biometric analysis shows size changes of n steinmannii and n kamptneri along the nannoconid decline the patterns of abundances and size changes seem to be related to paleoenvironmental changes mainly characterized by a temperature decrease and variable nutrient supply the described valanginian nannoconid recovery seems to occur during the most intense phase of the cooling event and is recorded in the vocontian basin as well as in the atlantic and tethys oceans these spatial correlations suggest a supra regional character for the valanginian nannoconid recovery event best recorded in the vocontian basin and at low latitudes

a 40 50 day oscillation in sea surface temperature along the central california coast abstract previous studies of the tropical troposphere indicate the presence of a 40 50 day quasi periodic oscillation in zonal winds spectral analysis of extensive daily sea surface temperatures ssts reveals a significant increase in variance i e a quasi periodic oscillation between 40 and 50 days along the california coast as far south as santa barbara 34 3 n and at least as far north as port arena 39 n increases in the amplitude of this oscillation at granite canyon 36 n in some cases coincide with local el nino warming episodes the local surface winds which also contain a quasi periodic oscillation between 40 and 50 days are coherent with and lead sea surface temperature by approximately 10 days consistent with local wind forcing it is suggested that the 40 50 day oscillation in sea surface temperature off central california may be related to the 40 50 day oscillation in the tropical troposphere through atmospheric teleconnections between the tropics and mid latitudes

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

a numerical study of the upwelling circulation off central chile effects of remote oceanic forcing 1 a numerical ocean model is used to study the upwelling circulation off central chile in response to local winds and remote forcing in an idealized study of equatorial forced intraseasonal variability period of 50 days a first mode coastal trapped wave ctw paddle is applied to the northern boundary with coastal sea level amplitude of 12 cm without this ctw forcing the steady seasonal winds upwell undercurrent water from depths of 250 320 m to depths of 180 250 m the subsequent formation of mesoscale and headland eddies drive this water into the gulf of arauco and to depths of 50 120 m with the ctw paddle the circulation is strongly modified the mesoscale and headland eddies reform during the ctw upwelling phase during the ctw upwelling phase the upwelling over winds and eddies is enhanced by up to 40 m on the shelf model simulations are undertaken using realistic winds and a ctw paddle modulated by observed sea level without ctw forcing included in the model the agreement with data is poor in the gulf of arauco area the variability of alongshore currents below 130 m is dominated by ctw activity above 130 m wind driven current variability dominates in agreement with the idealized ctw analysis water is found to be upwelled from depths of 320 m to 100 m or less and 10 c undercurrent water is found at the surface and within the gulf

impact of a coastal trapped wave on the near coastal circulation of the peru upwelling system from glider data alongshore velocity data from a glider repetitive section off the coast of peru 14 s are used to study the cross shore structure and temporal variability of the peru current system during a 5 week period in april may 2010 besides providing substantial information on the surface frontal jet associated with the peru coastal current and the surfacing peru chile undercurrent that flows poleward trapped on the continental shelf and slope the glider data reveal the presence of an intense deep equatorward current which transports up to 2 5 sv the dynamics of this current are investigated using an eddy resolving regional model the variability of the vertically sheared alongshore flow is shown to be related to the passage of a poleward propagating coastal trapped wave likely of equatorial origin solutions from a two dimensional linear coastal wave model suggest that the alongshore current observed vertical structure is associated with the second and third baroclinic modes of the coastal trapped wave

ammonoid and nannoplankton abundance in valanginian early cretaceous limestone marl successions from the southeast france basin carbonate dilution or productivity a quantification of calcareous nannofossil and ammonoid absolute abundance was carried out in the valanginian limestone marl alternations of the vergol section drome located in the epicontinental vocontian basin southeast france this section is characterised by four centimetric organic carbon rich layers barrande layers b1 b4 the aim of this work is to reconstruct changes in the distribution of nutrients in the water column on the base of the analysis of fossil organisms at different levels of the food chain calcareous nannofossil abundance correlates negatively with carbonate content thus calcareous nannoplankton probably did not produce the bulk of carbonates in the valanginian of the studied section nannofossil abundance was more likely controlled by carbonate mud produced and exported from shallow platform environments to the basin variations of carbonate export controlled by climate and hydrodynamics are responsible for the limestone marl alternations the levels of highest abundance of nannoplankton are interpreted as mainly linked to a reduced accumulation rate and to a minor extent to variations in primary production a dilution by allochthonous carbonate mud is further evidenced by the relationship between total organic carbon toc and calcium carbonate caco3 toc content decreases with increasing caco3 content except for one of the organic carbon rich layers b4 both taphonomy and dilution factors may have partly controlled the variations in macrofauna abundance these can be more likely interpreted as a response to palaeoenvironmental changes of the various taxa with different palaeoecological affinities the high abundance and dominance of bochianitids orthocone ammonoids in the layer b4 can be explained by their opportunistic behaviour and their deep nektonic possibly nektobenthic mode of life their great capacity for vertical mobility may have permitted brief feeding incursions to the bottom waters when the trophic resources were higher in depth than in the surface waters high trophic levels at the sea bottom may have also benefited the bivalves and gastropods which are very abundant in layer b4 the mode of life of different ammonoid families is also discussed

high sea surface temperatures during the early cretaceous epoch the early cretaceous epoch about 145 100 million years ago is generally thought of as a greenhouse period with high atmospheric co2 concentrations1 and high global mean temperatures2 but evidence for episodes of cooler conditions and even transient glaciations has been proposed3 4 5 6 7 8 9 here we present sea surface temperature records spanning the period from 142 to 128 million years ago berriasian barremian ages from low and mid latitudes reconstructed using the tex86 palaeotemperature proxy during this period we find sea surface temperatures exceeding 32 c at 15 20 n and averaging 26 c at 53 s these temperatures substantially exceed modern temperatures at equivalent latitudes and are incompatible with the notion of consistently cooler conditions in the earliest cretaceous moreover we find little variability in the sea surface temperature records even during the valanginian carbon isotope excursion 138 135 million years ago which was thought to be associated with marked temperature fluctuations5 we conclude that the earliest cretaceous was characterized by a warm stable climate with a lower meridional temperature gradient than today

propagation and forcing of high frequency sea level variability along the west coast of south america tide and wind data from coastal and island stations from buenaventura colombia 4 n to callao peru 12 s have been analyzed for the 1979 1984 time period to determine the propagation and forcing characteristics of coastal sea level variability at periods of days to weeks as well as how they vary either with season or between the 1982 1983 el nino southern oscillation enso period and non enso years during four non enso years the ensemble averaged cross spectra between coastal sea level height slh and local winds show weak evidence of local forcing during the whole year without significant differences between the austral summer and winter seasons other than a greater energy in the wind fluctuations at talara during summer cross spectra between slh series from neighboring stations show evidence of poleward phase propagation during winter seasons at speeds of about 2 0 m s 1 between la libertad and talara at periods of a week or more and about 2 7 m s 1 between talara and callao at periods of 5 11 days but no propagation is found during summers during the 1982 1983 enso there is a large increase in slh energy at most frequencies at all coastal stations but especially in the 8 to 11 day band where energies are enhanced by as much as an order of magnitude above non enso levels the cross spectra between adjacent slh stations indicate a nondispersive poleward propagation of events during the 1982 1983 enso with phase speeds of 2 2 3 5 m s 1 from la libertad to talara periods of a week or more and 3 4 3 6 m s 1 from talara to callao 3 5 days or more as with the slh energy the coherence and phase propagation were much stronger along the peru coast in 1982 1983 than during non enso periods especially in the 8 to 11 day band the one third increase in phase speeds during the enso over the non enso speeds is found to be consistent with the anomalous depression of the density structure during el nino comparisons between coastal slh and the local alongshore wind suggest that locally forced slh variability was obscured during the 1982 1983 enso by the noncoastally forced but energetic propagating fluctuations which probably originated in the equatorial waveguide

further evidence for coastal trapped waves along the peru coast abstract time series of coastal sea level during 1976 77 from 2 12 s to 17 s along the west coast of south america show that low frequency 0 25 cycles per day cpd fluctuations propagate poleward with the phase speed of baroclinic kelvin waves 2 3 m s 1 the alongshore coherence is highest in the frequency band 0 1 0 2 cpd computing the frequency domain empirical orthogonal functions eof for alongshore current from an army of current meters extending from 5 s to 15 s during march may 1977 gives 70 of the variance in the 0 1 0 2 cpd frequency band to an eof mode with poleward phase propagation at 2 75 m s 1 the vertical structure of the alongshore current fluctuations 0 1 0 2 cpd over the continental slope at 5 s and 15 s is consistent with a first mode baroclinic kelvin wave the current and sea level fluctuations are coherent and propagate poleward through latitudes where their frequency equals the local inertial frequency the fluctuations are not significantly coherent with coastal

a diverse ecosystem response to volcanic aerosols unexpectedly high aluminium concentrations beside fluoride and essential elements are released from metal salts adsorbed to volcanic ash through simulation of the mixing of pristine volcanic ash leachate with fresh water and seawater using phreeqc we found an increased potential toxicity in fresh waters through the combination of high aluminium and fluoride concentrations owing to the mixing of acid ash leachate with fresh water aluminofluoride complexes alfx 3 x persist in aqueous systems with low turnover rates and could be toxic to both plants and animals in contrast due to the well buffered and relatively high ph in seawater the speciation of the ash leachate seawater mixture shows that complexes of fluoride and aluminium i e alfx 3 x will not dominate in a well mixed marine system instead al oh x 3 x species will occur at greatest concentration consequently compared with fresh water environments the mixing of ash leachate with seawater indicates reduced toxic effects due to decreased formation of alfx 3 x complexes and the low solubility of al hydroxides in addition the deposition of volcanic aerosols may enhance biological activity in the marine environment by providing micronutrients as some oceanic phytoplankton species tolerates extreme concentrations of fluoride f

the valanginian isotope event a complex suite of palaeoenvironmental perturbations abstract the valanginian records a severe crisis of carbonate systems both on platforms and in the pelagic realm this crisis is roughly concomitant with the weissert event characterized by a positive 13c excursion of about 2 in marine carbonates however it is unclear if the response of these two carbonate systems to the global perturbations is contemporaneous or if they react differently for this purpose accumulation rates of pelagic carbonates produced by nannofossils and of platform derived carbonates have been quantified in a hemipelagic environment the vocontian basin se france that has the potential to record the reaction of both shallow water and pelagic carbonate production to a major perturbation of the carbon cycle testified by the isotope excursion also changes through time of clay input have been measured in order to evaluate variations in continental weathering rates and thus in continent derived nutrient input and climatic conditions in terms of humidity aridity accumulation rates of pelagic carbonates of platform derived carbonates and of clays were calculated on the basis of nannofossil absolute abundance and species specific masses of weight percent carbonate content of rocks and a high resolution timescale given by cyclostratigraphy the onset of the positive 13c excursion and the demise of the platforms testify for a synchronous but inverse response of the shallow water and pelagic carbonate systems to an increase in nutrient influx to marine waters as carbonate production by nannofossils decreased during the late valanginian in time of still low platform production the low temperature of marine waters coeval to a still high nutrient input recorded in the latest late valanginian possibly could explain that both platform and pelagic carbonate production contemporaneously decreased

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

intraseasonal oscillations in sea level along the west coast of the americas abstract hourly observations of coastal sea level at stations from peru to british columbia are analyzed for low frequency content a space time contour plot of sea level from four years of data during the 1971 75 period shows the meridional structure of the seasonal cycle and interannual variability associated with the 1972 73 el nino oscillations with intraseasonal periods of 36 73 days are also evident coherent over alongshore distances of several thousand kilometers further investigation using spectral methods and empirical orthogonal function analysis in the frequency domain reveals in particular that intraseasonal sea level variability has a peak in spectral density along the coasts of south america central america and mexico with high coherence from near the equator tumaco 2 n north to central california 34 n and south to at least callao 12 s phase propagation north of the equator is poleward at 150 200 kilometers day atmospheric pressure alongshore wind stress and wind stress cu

modes of covariability between sea surface temperature and wind stress intraseasonal anomalies along the coast of peru from satellite observations 2000 2008 1 the tropical rainfall measuring mission microwave imager sea surface temperature sst and quikscat wind stress satellite data are used to investigate the intraseasonal upwelling variability along the coat of peru over the period 2000 2008 two regions of peak variance correspond to the central peru region pisco region 15 s and the northern peru region piura region 5 s a covariance analysis reveals a significant coherency between winds and sst anomalies off pisco consistent with ekman pumping and transport dynamics the upwelling cell consists in a meridionally extended fringe of colder warmer water extending as far as 250 km from the coast at 15 s in the piura region the intraseasonal covariability pattern is represented by two modes one relevant to the direct ekman dynamics and the other one associated with the remote forcing of intraseasonal oceanic kelvin wave two regimes of variability are evidenced a low period regime 10 25 days is the signature of ekman transport pumping dynamics and is remotely forced by the migratory atmospheric disturbances across the southeastern pacific anticyclone a high period regime 35 60 day band is associated with the combined forcing of oceanic equatorial kelvin waves and migratory atmospheric disturbances in the midlatitudes in particular the modes of covariability exhibit a prominent 50 day period energy peak it is shown that this period arises from the impact of the first two baroclinic modes kelvin wave with the second baroclinic mode kelvin wave being more influential on the piura region

local and remote forcing of sea surface temperature in the coastal upwelling system off chile an analysis is presented of records of sea surface temperature sst sea level and winds collected during the period 1991 1995 along the coast of northern and central chile sea level also from the peru coast in 1991 1994 and of sst from remote sensing during the austral summers of 1991 and 1992 off northern chile large interannual fluctuations of sst and sea level off northern chile are linked to vertical displacements of the equatorial thermocline during el nino la nina events in the intraseasonal 50 day band sst and sea level are intimately related all along the coast whereby sst anomalies lag sea level perturbations by about 12 days such sea level fluctuations are due to free coastal trapped waves ultimately forced via equatorial kelvin waves by 50 day wind events in the western and central tropical pacific these results and those of the remote sensing analysis suggest significant remote forcing of sst fluctuations in the coastal zone off chile by the action of the coastal trapped waves off central chile sst is also related to local wind stress in the intraseasonal band simulations with a simple local wind driven upwelling entrainment model capture rather well observed synoptic and intraseasonal oscillations of sst there off northern chile however this simple model is not successful in simulating observed sst an attempt to include effects of coastal trapped waves into this simple one dimensional model did not improve model fit to data at either location an explanation for the apparent strong influence of these waves on sst along this coast should therefore be sought in other effects not considered by this model such as cross shelf and alongshore advection

long duration 4 ma and steady state volcanic activity in the early cretaceous parana etendeka large igneous province new palaeomagnetic data from namibia there is long standing correlation between large igneous provinces lips and major mass extinction events in the geological record postulated to be due to the emission of large quantities of volcanic gases over a geologically short period of time causing major climatic perturbations within the earth system the 135 ma parana etendeka volcanic province of brazil and namibia represents something of an enigma amongst lips despite an erupted volume 1 mkm3 comparable to other lips associated with mass extinctions such as the siberian or deccan traps it is not linked to a known mass extinction event this suggests that the parana etendeka volcanic province was emplaced over longer timescales than other lips and or emitted a lower concentration of volatiles directly or indirectly during its emplacement we present a new detailed magnetostratigraphy for the etendeka portion of the province that suggests emplacement took place over longer timescales 4 ma than those associated with other lips palaeomagnetic analysis of 893 specimens from 99 sites in sections that encompass nearly the complete etendeka stratigraphy yielded high quality data from 70 sites 612 specimens these record 16 individual polarity intervals which can be correlated with chrons 15 to 11 of the geomagnetic polarity time scale gpts while also providing two new high quality palaeopoles for south africa at 130 135 ma our magnetostratigraphy reveals a minimum period of volcanic activity in excess of 4 myrs and importantly we find no evidence for major changes in the rates of volcanic activity through that time period in contrast to other lips where volcanism seems to be concentrated in major pulses this suggests that the anomalously feeble environmental impact of parana etendeka volcanism may be due to lower effusion rates reducing the atmospheric loading due to volcanogenic volatiles

the equatorial source of propagating variability along the peru coast during the 1982 1983 el nino using data obtained from tide gages in south america current meters along the equator and the peru coast and an array of pressure gages and inverted echo sounders within and around the galapagos archipelago we have analyzed the equatorial origin of coastal trapped waves observed by cornejo rodriquez and enfield this issue along the peru coast during the intense 1982 1983 el nino the propagating fluctuations along the coast were much stronger at that time than either before or after the el nino and the variability was not locally forced by coastal winds we find that the coastal variability was also more energetic during previous el nino occurrences at periods of 1 2 weeks the meridional component of currents on the equator is up to an order of magnitude more energetic than the zonal fluctuations and is consistently associated with sea level that fluctuates antisymmetrically between hemispheres at periods longer than 2 weeks the zonal velocity component is more energetic and the cross equatorial sea level variability is symmetric the meridional and zonal phase structures of cross spectra involving the currents and sea level establish the 1 to 2 week equatorial fluctuations as mixed rossby gravity yanai waves of low wave number with infinite phase speed standing oscillations in the middle of the band 10 days the corresponding structures for longer periods are consistent with nondispersive kelvin waves frequency domain eof modes of the sea level and current data establish the mixed rossby gravity waves as the principal source of the strong trapped wave variability in the 1 to 2 week band along the ecuador peru coast during the 1982 1983 el nino episode

the intraseasonal oscillation in eastern pacific sea levels how is it forced abstract daily sea level and surface winds at eastern pacific shore locations and equatorial islands together with gridded five day averages of 850 mb winds have been analyzed for the 1979 84 period to determine how the 40 60 day intraseasonal oscillation of eastern pacific sea levels is forced as described by spillane et al for 1971 75 the oscillation was also present in 1980 84 from callao peru to san francisco with maximum energy near 52 57 days and band limits of 43 and 65 days during 1980 84 there was no evidence for forcing of the large scale oscillation in the eastern pacific although a local contribution of forcing was superimposed on the remote signal at the california stations interannual fluctuations in amplitude were evident in the sea level time series consistent with those of the corresponding wind oscillation in the western equatorial pacific the oscillation was best developed in both variables in 1980 82 and became weak or nonexistent during the recovery phase of the 1982 83 e

calcareous nannofossil response to the weissert episode early cretaceous implications for palaeoecological and palaeoceanographic reconstructions abstract the causal link between changes in calcareous nannofossil abundances their size and the palaeoenvironmental conditions in the tethyan realm across the valanginian weissert episode was examined through high resolution quantitative analyses of the genera nannoconus and micrantholithus from the angles section vocontian basin se france a set of published mineralogical micropalaeontological and geochemical data from numerous european localities including nannofossil data from italy france and romania and from the atlantic and pacific oceans allows us to propose a coherent palaeoecological and palaeoceanographic model and to discuss the possible forcing factors behind the palaeoenvironmental changes that occurred during the valanginian in the vocontian basin the genus nannoconus appears to be particularly sensitive to global fertility conditions and local continental input while micrantholithus is clearly associated with salinity levels during the first phase of the weissert episode a global increase in nutrients together with a breakdown of the upper water column stratification explains the nannoconid decline elevated freshwater fluxes into the vocontian basin under warmer and more humid conditions account for pentalith decreases low resolution data on pco 2 and ocean ca 2 concentrations cannot highlight large magnitude rapid fluctuations in pco 2 and oceanic ca 2 if they exist however relatively low pco 2 levels and high oceanic ca 2 concentrations probably helped the recovery of nannoconus and micrantholithus from the aftermath of the weissert episode to the early hauterivian the long term changes observed in the valanginian nannolith distribution are consistent with increased hydrothermal activity that influenced fertility levels low to mid latitudinal monsoonal circulation probably contributed to their short term changes by the way of rapid changes in the chemical weathering pattern that triggered significant fluctuations in turbidity fertility and salinity conditions

latitudinal temperature trends in the northern hemisphere during the early cretaceous valanginian hauterivian abstract we present the first detailed stable isotope record 13c 18o for the valanginian lower cretaceous of the southern boreal realm the observations are based on the geochemical analysis of 286 belemnite rostra from stratigraphically well dated sections in northwest germany a major positive carbon isotope excursion cie of 2 in the early late valanginian documents a perturbation of the carbon cycle this positive cie which is well known as the weissert event in the tethys is also displayed in composite carbon isotope records based on published and own data from three different palaeolatitudes 35 39 65 north these findings suggest that the environmental changes indicated by the cie in the early late valanginian are synchronous thereby pointing to a global control the combined oxygen isotope data sets show long term fluctuations of up to 7 c with a cooling in the late valanginian for both the southern and the arctic part of the boreal realm whilst tethyan data document only a ca 1 c cooling based on a reliable bio and chemostratigraphic correlation between the different realms this study highlights the amplitude of the environmental perturbations in the valanginian and supports the idea that a combination of regional and global factors caused such shifts

high temperatures in the late cretaceous arctic ocean to understand the climate dynamics of the warm equable greenhouse world of the late cretaceous period it is important to determine polar palaeotemperatures the early palaeoceanographic history of the arctic ocean has however remained largely unknown because the sea floor and underlying deposits are usually inaccessible beneath a cover of floating ice a shallow piston core taken from a drifting ice island in 1970 fortuitously retrieved unconsolidated upper cretaceous organic rich sediment from alpha ridge a submarine elevated feature of probable oceanic origin a lack of carbonate in the sediments from this core has prevented the use of traditional oxygen isotope palaeothermometry here we determine arctic palaeotemperatures from these upper cretaceous deposits using tex86 a new palaeothermometer that is based on the composition of membrane lipids derived from a ubiquitous component of marine plankton crenarchaeota from these analyses we infer an average sea surface temperature of approximately 15 degrees c for the arctic ocean about 70 million years ago this calibration point implies an equator to pole gradient in sea surface temperatures of approximately 15 degrees c during this interval and by extrapolation we suggest that polar waters were generally warmer than 20 degrees c during the middle cretaceous approximately 90 million years ago

lithium isotope evidence for enhanced weathering during oceanic anoxic event 2 the ocean anoxic event 2 oae2 about 93 5 million years ago was marked by high atmospheric co2 concentration rapid global warming and marine anoxia and euxinia the event lasted for about 440 000 years and led to habitat loss and mass extinction the marine anoxia is thought to be linked to enhanced biological productivity but it is unclear what triggered the increased production and what allowed the subsequent rapid climate recovery here we use lithium isotope measurements from carbonates spanning the interval including oae2 to assess the role of silicate weathering we find the lightest values of the li isotope ratio 7li during oae2 indicating high levels of weathering and therefore atmospheric co2 removal which we attribute to an enhanced hydrological cycle we use a geochemical model to simulate the evolution of 7li and the ca sr and os isotope tracers our simulations suggest a scenario in which the eruption of a large igneous province led to high atmospheric co2 concentrations and rapid global warming which initiated oae2 the simulated warming was accompanied by a roughly 200 000 year pulse of accelerated weathering of mafic silicate rocks which removed co2 from the atmosphere the weathering also delivered nutrients to the oceans that stimulated primary productivity we suggest that this process together with the burial of organic carbon allowed the rapid recovery and stabilization from the greenhouse state

decoupling of p and corg burial following early cretaceous valanginian hauterivian platform drowning along the nw tethyan margin during the hauterivian three important phases of platform drowning phosphogenesis and mesotrophic carbonate deposition along the northern margin of the tethys are not mirrored by positive n 13 ccarb excursions such as during the valanginian and aptian but rather by decreasing to stable trends the aim of this study is to understand the decoupling of organic carbon and phosphorus burial during the hauterivian for this purpose po4 concentrations were determined from biogenic limestones from eight sections along a platform to basin transect integration with a previously obtained dataset for the valanginian leads to a biostratigraphically calibrated high resolution phosphorus accumulation rate mg cm 2 kyr curve based on 575 data points from the late valanginian to early hauterivian phosphorus accumulation rates increased nearly threefold from 0 75 mg cm 2 kyr to 2 1 mg cm 2 kyr the phosphorus accumulation rate increase obtained in this study correlates well with a compilation based on odp and dsdp records indicating that phosphorus accumulation rates along the northern margin of the tethys reflect global changes in p in and output a global rise in continental p input is thought to have resulted from intensified greenhouse climate conditions leading to increased riverine runoff coeval sea level rise led to re arrangement of circulation and oxygenation of bottom waters which meant that p was increasingly well retained by means of fe and mnoxyhydroxides furthermore the nw margin of the tethys may have been especially susceptible to phosphogenesis as it was influenced by cold water exchange with the boreal realm and prone to coastal upwelling the late hauterivian witnessed sea level fall more sluggish circulation along the nw tethyan margin and also globally lower weathering and erosion rates leading to generally lower phosphorus accumulation rates increased regeneration of phosphorus might have occurred as circulation stagnated and bottom water oxygen levels decreased increased phosphorus input into early hauterivian oceans did not lead to the production of organic carbon rich rocks but rather to increased carbonate carbon burial also seen in a decoupling between the n 13 ccarb record decreasing and phosphorus accumulation rates increasing decoupling of these records reflects the ecological recovery of the carbonate system after a prolonged phase of reef destruction during the late early and late valanginian carbonate production in the

atmospheric transport of iron and its deposition in the ocean the atmospheric transport of continental weathering products is responsible for much of the mineral material and fe entering the open ocean and is probably the dominant source of nutrient fe in the photic zone in regions where other nutrients are present in high concentrations the flux of fe from the atmosphere may be a limiting factor in primary productivity due to the larger source regions for dust north of the equator 8 times more atmospheric fe is deposited in the northern hemisphere than in the southern hemisphere the mineral aerosol and fe transport and deposition are highly variable due to the episodic nature of dust generation and its transport and deposition processes between 10 and 50 of the total atmospheric fe entering the world ocean appears to dissolve i e it will pass through a 0 4 m pore size filter rapidly when the mineral matter enters the ocean much of the atmospheric fe is present as fe ii apparently produced as a result of photochemical reduction reactions taking place during atmospheric transport this readily soluble fe ii should be available immediately for use as a nutrient by phytoplankton atmospheric transport from the continents is estimated to supply 3 times as much dissolved fe to the oceans as that delivered via rivers

interdecadal sea surface temperature sea level pressure coupled variability in the south pacific ocean 1 the main coupled sea surface temperature sst sea level pressure slp variability at interdecadal timescale in the south pacific is studied by means of correlation and combined complex empirical orthogonal function cceof analyses the sst slp coupled variability presents a bidecadal cycle from mid 1950s to 1970s and a decadal cycle from 1980s to early 1990s reproducing the enso like interdecadal oscillation particularly the first sst slp cceof mode describes the bidecadal cycle characterized by westward progression of sst and slp anomalies along the tropical pacific while the second sst slp cceof mode shows the decadal cycle with eastward development during both bidecadal and decadal cycles the sst fluctuations in the eastern equatorial pacific and along the western coast of south america are primarily forced by equatorial zonal wind variability specially during the bidecadal cycle the alongshore sst variability south of 30 s is maintained and reinforced by meridional coastal wind fluctuations associated with a stationary slp pattern off southern chile this stationary slp pattern appears connected to sst fluctuations in the central tropical pacific

size variations of coccoliths in cretaceous oceans a result of preservation genetics and ecology abstract biometric studies of coccoliths the remains of coccolithophores offer the opportunity to survey single species instead of entire assemblages we obtained and analyzed size data of three common species biscutum constans zeugrhabdotus erectus and watznaueria barnesiae in a stratigraphically very well defined interval of early aptian age 126 ma cretaceous material is derived from four sites lower saxony basin north sea western tethys mid pacific covering nearshore to open oceanic paleosettings length and width measurements of 1986 specimens were evaluated the recorded size patterns show a larger data spread for b constans and w barnesiae in the western tethys and the mid pacific than in the north sea and the lower saxony basin the latter two sites are dominated by small coccoliths of b constans while coccoliths of w barnesiae show similar sizes at all four sites solely small specimens of z erectus characterize the samples from the north sea and the lower saxony basin while only large ones are present in the samples of the western tethys and mid pacific for explaining the recorded size patterns three theories are discussed in detail these include 1 preservation of nannofossils 2 genetics and 3 paleoecology 1 intense dissolution or overgrowth of the nannofossils may have altered the original coccolith sizes particularly when biometric data from different sites with potentially varying states of preservation are compared due to its delicate morphology z erectus appears most prone to dissolution probably explaining its size pattern 2 if the recorded size data of the remaining two species represent original patterns these can be interpreted by new findings in recent coccolithophore genetics it has been shown that size variations within a single cryptic species are only minor shifts of coccolith sizes both in recent and fossil taxa can be related to genotypic variation the varying size ranges recorded for b constans and w barnesiae may therefore reflect diversity changes of cryptic species at the different sites 3 these cryptic species may have preferred different depth habitats depending on geographically controlled factors such as sea surface temperatures light availability or trophic load

front eddy influence on water column properties phytoplankton community structure and cross shelf exchange of diatom taxa in the shelf slope area off concepcion 36 37 s in eastern boundary current systems ebcss submesoscale to mesocale variability contributes to cross shore exchanges of water properties nutrients and plankton data from a short term summer survey and satellite time series january february 2014 were used to characterize submesoscale variability in oceanographic conditions and phytoplankton distribution across the coastal upwelling and coastal transition zones north of punta lavapie and to explore cross shelf exchanges of diatom taxa a thermo haline front frn 1 flanked by a mesoscale anticyclonic intrathermocline eddy ite 1 or mode water eddy persisted during the study period and the survey was undertaken during a wind relaxation event at the survey time ite 1 contributed to an onshore intrusion of warm oceanic waters southern section and an offshore advection of cold coastal waters northern section with the latter forming a cold high chlorophyll a filament in situ phytoplankton and diatom biomasses were highest at the surface in frn 1 and at the subsurface in ite 1 whereas values in the coastal zone were lower and dominated by smaller cells diatom species typical of the coastal zone and species dominant in oceanic waters were both found in the frn 1 and ite 1 interaction area suggesting that this mixture was the result of both offshore and onshore advection overall front eddy interactions in ebcss could enhance cross shelf exchanges of coastal and oceanic plankton as well as sustain phytoplankton growth in the slope area through localized upward injections of nutrients in the frontal zone combined with ite induced advection and vertical nutrient inputs to the surface layer

tropical warming and intermittent cooling during the cenomanian turonian oceanic anoxic event 2 sea surface temperature records from the equatorial atlantic oceanic anoxic event 2 oae 2 occurring during the cenomanian turonian c t transition is evident from a globally recognized positive stable carbon isotopic excursion and is thought to represent one of the most extreme carbon cycle perturbations of the last 100 myr however the impact of this major perturbation on and interaction with global climate remains unclear here we report new high resolution records of sea surface temperature sst based on tex86 and 18o of excellently preserved planktic foraminifera and stable organic carbon isotopes across the c t transition from black shales located offshore suriname french guiana demerara rise ocean drilling program leg 207 site 1260 and offshore senegal cape verde basin deep sea drilling project leg 41 site 367 at site 1260 where both sst proxy records can be determined a good match between conservative sst estimates from tex86 and 18o is observed we find that late cenomanian ssts in the equatorial atlantic ocean 33 c were substantially warmer than today 27 29 c and that the onset of oae 2 coincided with a rapid shift to an even warmer 35 36 c regime within the early stages of the oae a marked 4 c cooling to temperatures lower than pre oae conditions is observed however well before the termination of oae 2 the warm regime was reestablished and persisted into the turonian our findings corroborate the view that the c t transition represents the onset of the interval of peak cretaceous warmth more importantly they are consistent with the hypotheses that mid cretaceous warmth can be attributed to high levels of atmospheric carbon dioxide co2 and that major oaes were capable of triggering global cooling through the negative feedback effect of organic carbon burial led co2 sequestration evidently however the factors that gave rise to the observed shift to a warmer climate regime at the onset of oae 2 were sufficiently powerful that they were only briefly counterbalanced by the high rates of carbon burial attained during even the most extreme interval of organic carbon burial in the last 100 myr

macrobenthic zonation caused by the oxygen minimum zone on the shelf and slope off central chile abstract the relationship between macrobenthic 300 m zonation and the oxygen minimum zone omz o2

the impact of calcareous nannofossils on the pelagic carbonate accumulation across the jurassic cretaceous boundary abstract calcareous nannofossils were important producers of pelagic carbonates in mesozoic oceans in order to better understand the origin of mesozoic pelagic carbonates we studied upper jurassic to lower cretaceous sediments in the central atlantic ocean dsdp sites 105 367 534a with respect to their content of calcareous nannofossils the interval under investigation is characterized by a significant increase in the deposition of carbonate rich sediments a trend that goes along with the rapid radiation of calcareous nannofossils the assemblage composition and the size variation of common taxa were analyzed and subsequently the contribution of this phytoplankton group to the pelagic carbonate accumulation was calculated results reveal two long term changes of the nannofossil assemblage composition 1 the early tithonian coccolith assemblages are of low diversity watznaueria spp cyclagelosphaera spp zeugrhabdotus spp whilst the mid to late tithonian assemblage is dominated by nannoliths conusphaera mexicana polycostella beckmannii nannoconus spp and large sized watznaueria 2 the early berriasian is characterized by a shift from the late tithonian nannolith rich assemblage to a highly diverse coccolith assemblage morphometric studies of the placolith genus watznaueria show for all three dsdp sites large sized forms of this genus in the mid and late tithonian followed by a decrease of up to 2 m for the mean size in the earliest berriasian at dsdp site 105 the studied nannolith taxa show an increase in size during the mid tithonian to berriasian interval the records of both nannofossil carbonate estimates and the measured bulk rock carbonate reveal two periods of increase in the nannofossil carbonate record of dsdp site 105 a first significant increase of the carbonate accumulation is observed in the mid and late tithonian probably caused by mass occurrences of strongly calcified taxa c mexicana p beckmannii nannoconus spp watznaueria cf manivitae this interval is here named nannofossil calcification event nce the second carbonate maximum in the late berriasian is related to a rise in absolute abundances of nannofossils this peak is amplified by an overall increase of the sedimentation rate the calculated accumulation rates of nannofossils nannofossil carbonate and bulk rock carbonate for the late berriasian are on the same scale as values from recent ocean surface sediments a comparison of nannofossil carbonate values with the bulk rock carbonate content shows that on average only 27 of the total carbonate can be explained by our nannofossil carbonate estimates this discrepancy is most likely caused by the high amount of unidentifiable micrite and fragments of calcareous nannofossils other factors contributing to the error are possible inaccuracies in the determination of absolute abundances and nannofossil volume calculations the nce occurs during a long term sea level fall dry climate and presumed low pco 2 levels a decline in abundance of strongly calcified nannofossils coincides with the opening of the pacific atlantic seaway via central america which may have had a substantial impact on the palaeoceanographic situation in the central atlantic ocean these changes are here considered to have at least partly caused the shifts in abundance size and assemblage composition of calcareous nannofossils observed across the jurassic cretaceous boundary interval

early diagenesis of redox sensitive trace metals in the peru upwelling area response to enso related oxygen fluctuations in the water column pore water and solid phase data for redox sensitive metals mn fe v mo and u were collected on a transect across the peru upwelling area 11 s at water depths between 78 and 2025 m and bottom water oxygen concentrations ranging from 0 to 93 m by comparing authigenic mass accumulation rates and diffusive benthic fluxes we evaluate the respective mechanisms of trace metal accumulation retention and remobilization across the oxygen minimum zone omz and with respect to oxygen fluctuations in the water column related to the el nino southern oscillation enso sediments within the permanent omz are characterized by diffusive uptake and authigenic fixation of u v and mo as well as diffusive loss of mn and fe across the benthic boundary some of the dissolved mn and fe in the water column re precipitate at the oxycline and shuttle particle reactive trace metals to the sediment surface at the lower and upper boundary of the omz at the lower boundary pore waters are not sufficiently sulfidic as to enable an efficient authigenic v and mo fixation as a consequence sediments below the omz are preferentially enriched in u which is delivered via both in situ pre cipitation and lateral supply of u rich phosphorites from further upslope trace metal cycling on the peruvian shelf is strongly affected by enso related oxygen fluctuations in bottom water during periods of shelf oxygenation surface sediments receive particulate v and mo with metal oxyhydr oxides that derive from both terrigenous sources and precipitation at the retreating oxycline after the recurrence of anoxic conditions metal oxyhydr oxides are reductively dissolved and the hereby liberated v and mo are authigenically removed this alternation between supply of particle reactive trace metals during oxic periods and fixation during anoxic periods leads to a preferential accumulation of v and mo compared to u on the peruvian shelf the decoupling of v mo and u accumulation is further accentuated by the varying susceptibility to re oxidation of the different authigenic metal phases while authigenic u and v are readily re oxidized and recycled during periods of shelf oxygenation the sequestration of mo by authigenic pyrite is favored by the transient occurrence of oxidizing conditions our findings reveal that redox sensitive trace metals respond in specific manner to short term oxygen fluctuations in the water column the relative enrichment patterns identified might be useful for the reconstruction of past omz extension and large scale redox oscillations in the geological record

the valanginian δ13c excursion may not be an expression of a global oceanic anoxic event abstract marine and terrestrial sediments of the valanginian age display a distinct positive 13 c excursion which has recently been interpreted as the expression of an oceanic anoxic episode oae of global importance here we evaluate the extent of anaerobic conditions in marine bottom waters and explore the mechanisms involved in changing carbon storage on a global scale during this time interval we asses redox sensitive trace element distributions rste uranium vanadium cobalt arsenic and molybdenum and the quality and quantity of preserved organic matter om in representative sections along a shelf basin transect in the western tethys in the polish basin and on shatsky rise om rich layers corresponding in time to the 13 c shift are generally rare in the tethyan sections and if present the layers are not thicker than several centimetres and total organic carbon toc contents do not surpass 1 68 wt palynological observations and geochemical properties of the preserved om suggest a mixed marine and terrestrial origin and deposition in an oxic environment in the polish basin om rich layers show evidence for an important continental component rste exhibit no major enrichments during the 13 c excursion in all studied tethyan sections rste enrichments are however observed in the pre 13 c excursion om rich barrande levels of the vocontian trough in addition all tethyan sections record higher mn contents during the 13 c shift indicating rather well oxygenated bottom waters in the western tethys and the presence of anoxic basins elsewhere such as the restricted basins of the north atlantic and weddell sea we propose that the valanginian 13 c shift is the consequence of a combination of increased om storage in marginal seas and on continents as a sink of 12 c enriched organic carbon coupled with the demise of shallow water carbonate platforms diminishing the storage capacity of 13 c enriched carbonate carbon as such the valanginian provides a more faithful natural analogue to present day environmental change than most other mesozoic oaes which are characterized by the development of ocean wide dysaerobic to anaerobic conditions

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 guide to phanerozoic cold polar climates from high latitude ice rafting in the cretaceous the high latitude extent of warm climate indicators at certain times in earth history has been considered as evidence that the globe was ice free for long intervals despite theoretical considerations and results from numerical modelling experiments1 2 indicating that this was unlikely one of the warmest periods the cretaceous displays faunal and floral evidence for cool temperate to sub tropical conditions very near to the poles however our studies of lower cretaceous mudstones of central australia that contain outsized exotic blocks have led to the conclusion that the blocks were emplaced by ice rafting implying that high latitude ice was present at sea level strata of a similar origin of mid jurassic to mid cretaceous age occur on other continents that were positioned between 65 and 78 palaeolatitude indeed there is a record of high latitude ice rafting throughout the phanerozoic suggesting that ice was present on earth for much of its history and that ice free conditions could have been at most only episodic over the past 600 myr

trace metal suites in antarctic pre industrial ice are consistent with emissions from quiescent degassing of volcanoes worldwide abstract trace metals are more abundant in atmospheric load and deposition material than can be due to rock and soil dusts and ocean salt in pre industrial ice from coastal west antarctica dust and salt account for only a few percent of the lead cadmium and indium that is present in most samples less than half in any sample for these trace metals the deposition rate to the pre industrial ice is approximately matched by the output rate to the atmosphere by quiescent non explosive degassing of volcanoes worldwide according to a new estimate the basis of the match is the masses and proportions of the metals and the proportions of pb isotopes in ice and in volcano emissions the isotopic compositions of pb in ice are similar to those of a suite of ocean island volcanoes mostly in the southern hemisphere the natural baseline values for pre industrial atmospheric deposition fluxes of trace metal suites at taylor dome and the worldwide quiescent volcano emissions fluxes to which they are linked constitute a reasonably well constrained baseline component for deposition fluxes of metals in modern times

seasonal variability of coastal upwelling and the upwelling front off central chile 1 we analyze sea surface temperature sst and chlorophyll a chl a satellite data to study the seasonal variability of the upwelling off central chile data from an oceanographic cruise are used to illustrate the vertical characteristics of the upwelling front and the geostrophic flow the mean offshore extension of the sst front in summer is 110 km there sst changes from 13 5 c near the coast to 14 5 15 c offshore hydrographic data show that the thermocline becomes progressively shallower toward the coast but that at a certain distance it abruptly bends to form a horizontal front that extends until 50 m depth satellite data show that the chl a decays exponentially offshore and a concentration of 1 mg m 3 indicates the offshore limit of the frontal region the sst front observed most of the year is absent in winter when the coastal water is only slightly colder than the oceanic one however relatively higher chl a values remain present near the coast during winter northwest of punta lavapie 37 15 s the frontal region is located progressively farther offshore suggesting that a branch of an equatorward surface jet separates from the coast to form a meander which is associated with a filament of cold water and an anticyclonic eddy observed frequently in this zone during summer hydrographic data show that isotherm and current disturbances related to mesoscale eddies can extend several hundreds of meters below the surface in contrast the coastal jet is quite shallow extending until 150 m depth

the pacific south american modes and tropical convection during the southern hemisphere winter abstract atmospheric circulation features and convection patterns associated with two leading low frequency modes in the southern hemisphere sh are examined in multiyear global reanalyses produced by ncep ncar and nasa dao the two leading modes referred to as the pacific south american psa modes are represented by the first two eof patterns the two patterns are in quadrature with each other and are dominated by wavenumber 3 in midlatitudes with large amplitudes in the pacific south american sector in the pacific anomalies in the subtropics and in the midlatitudes are opposite in phase taken together the two psa modes represent the intraseasonal oscillation in the sh with periods of roughly 40 days the evolution of the psa modes shows a coherent eastward propagation a composite analysis was conducted to study the evolution of tropical convection and the corresponding circulation changes associated with the psa modes outgoing longwave radiation olr anomaly composites during the mature phase

late quaternary variability of sedimentary nitrogen isotopes in the eastern south pacific ocean 1 we present high resolution bulk sedimentary 15n data from the southern edge of the present day oxygen minimum zone of the eastern south pacific the record is interpreted as representing changes in water column nitrogen removal during the last 70 000 years we found significant fluctuations in the isotopic signal that suggest major reorganizations of the oxygen minimum zone at millennial timescales these fluctuations were not related to other millennial scale changes like the northern hemisphere s dansgaard oeschger climate swings or local changes in primary productivity so appear to be dictated by the southern hemisphere s climate rhythm this is preliminarily corroborated by an overall agreement between our 15n data and the sedimentary proxy of ice sheet dynamics in patagonia which is in turn correlated with surface water properties at the midlatitude subduction region of the eastern south pacific intermediate waters finally potential implications on late quaternary changes in atmospheric co2 concentrations are discussed

seasonal and interannual variability of currents and temperature off central chile results are reported for continuous 6 year records of current and temperature from a continental slope station at 308s off chile these observations for november 1991 to november 1997 span the moderate weak and strong el nino events of 1991 1992 1994 and 1997 and the la nina event of 1995 1996 results for current and temperature are analyzed together with observations of wind along the south american coast from the ers 1 and 2 satellite scatterometers wind from a local coastal site sea level from northern and central chile sea surface temperature anomalies from the south pacific region and traditional el nino indices mean poleward flow of 12 8 cm s 21 was observed for the 6 year period in the core of the peru chile undercurrent 220 m mean flow in the depth range of antarctic intermediate water 750 m was equatorward at 1 1 cm s 21 intraseasonal scale variability associated with coastal trapped waves was weaker during the austral winter greatest during el nino events and weakest during the la nina event winds adjacent to the coast showed a strong annual cycle with a southward progression of maximum equatorward upwelling favorable winds alongshore flow over the slope exhibited strong semiannual and weaker annual variations poleward flow in the undercurrent was strongest in the austral spring and fall and weakest in the winter near the bottom 750 m seasonal scale variability was less intense but led that higher up in the water column 220 m by 1 month strong interannual variability of alongshore current and temperature was found at all depths over the slope whereby changes at depth led changes higher up a rapid warming event was observed at the end of 1996 beginning of 1997 over the slope this event also seen in sea level and sea surface temperature off chile led el nino indices by several months and may be best explained by local wind anomalies coupled to atmospheric teleconnections from the western tropical pacific at the onset of el nino some aspects of our current and temperature observations are consistent with results from eastern boundary current models our results indicate that both ocean and atmosphere pathways from the equatorial pacific contribute significantly to interannual scale variability of alongshore flow and thermocline depth off chile

elemental abundance anomalies in the late cenomanian extinction interval a search for the source s elemental abundances have been measured by neutron activation methods across the cenomanian turonian late cretaceous extinction interval in samples collected from sixteen sites in the western interior basin of north america and from twelve widely separated locations around the globe including six odp dsdp sites in most western interior basin sites in colombia and in western europe weaker two closely spaced elemental abundance peaks occur in the upper cenomanian 92 m y spanning the ammonite zones ofsciponoceras gracile throughneocardioceras juddii elements with anomalously high concentrations include sc ti v cr mn co ni ir pt and au the lower peak coincides with the disappearance extinction of the foraminiferrotalipora cushmani in north american sectionsr greenhornensis also disappears at or just below this horizon but in europe it disappears considerably earlier thanr cushmani a series of molluscan extinction and speciation or migration events also begins near the stratigraphic level of the lower elemental abundance peak the well documented positive 13c excursion begins just before the extinctions and the elemental anomalies and continues into the lower turonian well above the upper anomaly this carbon isotope excursion has been observed in east european sections where we find little or no evidence of the elemental anomalies suggesting that the two phenomena may not be tightly coupled elemental abundance ratios in the anomalies closely resemble those of mid atlantic ridge basalt or hawaiian lava tholeiitic but not those of c1 chondrite black shale average crustal rocks or lamproite and kimberlite of roughly similar age in southeastern kansas the excess ir and other siderophiles hint at possible large body impact s for the source however we have not located microspherules other than biogenic calcispheres or shocked mineral grains in any of our samples furthermore sc ti v and mn are not enriched in differentiated solar system bodies although the weak geochemical signal from comet impact s could be masked by the strong terrestrial like overprint these anomalies more likely resulted either from intense seafloor spreading activity or merely from increased circulation of deep metal rich water associated with the large late cenomanian through early turonian eustatic rise and deep water opening of the south atlantic the flooding of continental seaways and margins also could have contributed to the anomalies by preventing much continental detritus from diluting the normal background marine geochemical component

accumulation of organic carbon rich sediments in the late jurassic and cretaceous atlantic ocean a synthesis abstract organic carbon rich sediments black shales were deposited at some 40 deep sea drilling project dsdp sites in the atlantic ocean during late jurassic and cretaceous times in order to reconstruct the depositional environments of black shale formation we have studied in detail changes in the occurrence of black shales as well as the type and amount of organic matter in relation to changes in paleogeography paleooceanic circulation and paleoclimate we have calculated accumulation rates of marine and terrigenous organic carbon and combined these with organic carbon content sedimentation rate relationships to obtain information about paleoenvironments main factors causing the preservation and accumulation of organic carbon are 1 the supply of terrestrial organic matter 2 the supply of marine organic matter 3 the oxygenation of the deep water and 4 the bulk sedimentation rate changes in the importance of these different factors and changes in the interrelationships among them determine the complex system of black shale formation and their cyclic variations increased supply of terrestrial organic matter due to increased river discharge and humid climate in northeast america southwest europe and south africa were important in the hauterivian albian northwest and northern northeast atlantic and in the late jurassic aptian south atlantic in the latter anoxic deep water conditions due to restricted circulation in the nascent largely isolated basin as well as higher oceanic productivity may have reinforced the high preservation rates of marine organic matter during that time off northwest africa higher flux rates of marine organic matter were recorded in areas of higher productivity which may have been caused by fluvial nutrient supply during the hauterivian and by intensified upwelling during albian turonian times in general the depositional environment was oxygenated and the content of marine organic matter was a function of the sedimentation rate furthermore at some places redeposition by turbidity currents or slumps may have been important for the accumulation of organic matter in the deep sea basins the only episode of widespread anoxia in the western and eastern basins of the north atlantic may have occurred in the cenomanian turonian when high amounts of marine organic matter were also preserved in areas of low productivity and low sedimentation rates

a comparison of long coastal trapped wave theory with observations off peru abstract the agreement between coastal trapped wave theory and observation is studied for the case of observations made off peru during the 1977 cuea joint ii experiment wave properties are calculated using a numerical model with realistic horizontally uniform stratification and realistic bottom topography these properties are then explored as a function of the ratio of the first internal rossby radius of deformation to the shelf slope width the agreement of observed and calculated first mode free wave phase speeds 230 cm s 1 is excellent while modal structures agree more poorly a forced wave calculation using observed winds and currents as input is used to hindcast alongshore currents and sea level in the frequency band where smith 1978 observed free coastal trapped waves during 1977 the model suggests that most of the observed sea level and alongshore velocity fluctuations in the 5 10 day period band are due to free waves originating equatorward of 5 deg s while winds between 5 deg s and

climate and paleoceanography controlled size variations of calcareous nannofossils during the valanginian weissert event early cretaceous abstract strata of valanginian age early cretaceous 139 8 132 9 ma record a 1 5 positive carbon isotope excursion cie the weissert event it coincides with volcanic activity of the parana etendeka large igneous province unlike the mesozoic oceanic anoxic events oaes no organic rich deposits documenting widespread perturbation of the marine carbon cycle are associated with the weissert event to study the impact of paleoceanographic changes in the valanginian on calcareous nannofossils this study analyzes coccolith size data of three species biscutum constans watznaueria barnesiae zeugrhabdotus erectus from northern germany and the western north atlantic further it presents a new valanginian carbon isotope record of organic material 13corg from northern germany the dataset records the weissert event cie in the late valanginian at both locations biometric analyses reveal size decreases of b constans coccoliths during the weissert event a size reduction of 1 m has been observed for northern germany 37 n and of 0 4 m for the north atlantic 23 n the different magnitudes of size decrease possibly reflect the different paleogeographic positions of the sites and the paleoceanographic response to the late valanginian climate variations proxy data support a link between a humid climate with increased weathering and the observed coccolith size variations this impacted nannoplankton communities either through the availability of light or by eutrophication and possibly nutrient limitation in addition to increased terrigenous input emissions of the parana etendeka volcanism possibly acted fertilizing furthermore widely dispersed volcanic emissions possibly caused increased concentrations of toxic trace metals in the surface ocean which affected marine primary producers

an exchange window for the injection of antarctic intermediate water into the south pacific antarctic intermediate water aaiw occupies the intermediate horizon of most of the world oceans formed in the southern ocean it is characterized by a relative salinity minimum with a new denser in situ national oceanographic data center dataset the authors have reanalyzed the export characteristics of aaiw from the southern ocean into the south pacific ocean these new data show that part of the aaiw is exported from the subpolar frontal region by the large scale circulation through an exchange window of 10 width situated east of 90 w in the southeast corner of the pacific basin this suggests the origin of this water to be in the antarctic circumpolar current a set of numerical modeling experiments has been used to reproduce these observed features and to demonstrate that the dynamics of the exchange window is controlled by the basin scale meridional pressure gradient the exchange of aaiw between the southern and pacific oceans must therefore be understood in the context of the large basin scale dynamical balance rather than simply local effects

tex86 and stable δ18o paleothermometry of early cretaceous sediments implications for belemnite ecology and paleotemperature proxy application abstract recent studies have cast doubt on the unadjusted usage of jurassic and cretaceous 18 o paleotemperature data derived from belemnites since the latter data often reflect cooler paleotemperature estimates than would be expected in this study we address this problem by analysing rocks of barremian to early aptian age from two outcrops in northern germany using tex 86 paleothermometry along with 142 belemnite guards studied for their stable isotope 13 c 18 o and trace element composition magnesium strontium iron and manganese both tex 86 and 18 o bel indicate very warm water temperatures for a distinctive black shale sequence of late early barremian age hauptblatterton with temperatures of up to 29 c and 23 c respectively we observe a constant offset of tex 86 temperatures versus the 4 to 5 c cooler 18 o belemnite signal for this interval the late barremian sequence shows an increase of the 18 o bel values from 1 to 0 reflecting temperatures around 16 to 12 c while the contemporaneous tex 86 temperatures vary between 26 and 32 c the common occurrence of belemnites in the anoxic sediments of the early barremian implies however clearly a nektonic way of life similar to that of recent teuthids rather than a nektobenthic one like sepia this in turn suggests that the belemnites investigated here genera praeoxyteuthis aulacoteuthis oxyteuthis and neohibolites were active swimmers which inhabited a deeper habitat below the thermocline in an epicontinental sea of perhaps 100 to 250 m water depth the offset of the tex 86 and 18 o bel data is therefore interpreted to reflect temperature signals from two different depth habitats i e the tex 86 is selectively derived from warm sea surface waters and the belemnites likely occupied deeper and cooler waters with relative increasing salinities in the late barremian this study stresses the importance that the taxonomy paleobiology and ecology of the belemnite taxa genera species used for paleotemperature reconstructions must be considered before the 18 o bel signal can be further interpreted the variation of the 18 o signature gained from one belemnite population of 22 specimens by 1 1 suggests that the 18 o data of individual belemnites should be used with caution for reconstructing long termed paleotemperature trends

integrated stratigraphy of lower cretaceous sediments ryazanian hauterivian from north east greenland abstract the reconstruction of past climates and oceanography requires a solid stratigraphic framework ideally applicable on a global scale the earliest cretaceous however was a time of strong faunal provincialism making supra regional correlation of biostratigraphical zonations difficult the step by step correlations between neighbouring provinces subprovinces that are commonly utilized bear the risk of loosing accuracy in every step here we present 87sr 86sr and stable isotope data 13c 18o from belemnite rostra of the rodryggen section in north east greenland the integrated stratigraphy based on sr isotope ratios ammonite and calcareous nannofossil biostratigraphy offers the opportunity for a direct comparison of the different stratigraphic zonations these are complemented by 13cbel data recording the positive carbon isotope excursion of the valanginian weissert event which is a reliable stratigraphic event the geochemical data furthermore allow a reliable correlation of tethyan and boreal strata the stratigraphic range of the rodryggen section resulting from sr isotope stratigraphy ryazanian barremian is in agreement with the biostratigraphic findings mismatches regarding stage substage boundaries demand a reconsideration of the nannofossil biostratigraphy of the boreal lower cretaceous our findings suggest stratigraphic ranges for two nannofossil index species sollasites arcuatus micrantholithus speetonensis different from published ranges the new observations imply changes in the boreal ryazanian valanginian nannofossil zonation scheme specifically the base of calcareous nannofossil zone bc3 originally defined as uppermost ryazanian is shifted to the lower valanginian based on these new stratigraphic interpretations a decrease in the abundance of nannoconids observed in the rodryggen section can now be identified as the valanginian nannoconid crises this nannoconid decline has been observed in tethyan sections along with the weissert event a positive trend in the 18obel data agrees with a late valanginian cooling that has been postulated based on independent proxies from the boreal realm and the tethys

deposition of atmospheric heavy metals to the greenland ice sheet from the 1783 1784 volcanic eruption of laki iceland abstract in order to assess better the influence of major volcanic events on the large scale atmospheric cycles of heavy metals greenland ice dated from the time of the fallouts from the great 1783 1784 eruption of laki volcano in iceland has been analysed for pb cd cu zn and sulphate the concentrations of the four heavy metals investigated are found to be greatly enhanced in the ice layers which correspond to the fallouts from the eruption confirming that such events do modify the atmospheric cycles of heavy metals cumulative fallout of heavy metals to the whole greenland ice cap from the 1783 1784 laki eruption ranges from 1 t for pb and cd to 40 t for zn for cd cu and zn it represents a few percent of the cumulative anthropogenic fallout to the ice cap from the industrial revolution to the present

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

trace element abundances in the rock canyon anticline pueblo colorado marine sedimentary section and their relationship to caribbean plateau construction and oxygen anoxic event 2 1 rapid eruption of submarine lava flows during formation of the caribbean plateau correlates closely with ocean anoxic event 2 oae2 which bracketed the cenomanian turonian boundary 93 5 ma these events also correspond with a positive excursion in carbon isotopic composition of seawater hydrothermal activity associated with large scale submarine volcanism may have been responsible for this abrupt change in ocean chemistry we determined the distribution of major minor and trace element abundances in the rock canyon marine sedimentary section pueblo colorado after normalizing element concentrations to zr to remove the variable contribution of terrigenous material to these sediments we detected an interval of concentrated metal abundance anomalies that coincides with the abrupt beginning of the positive 13c isotope excursion the metal abundance anomalies indicate that intermittent hydrothermal activity in the form of both water rock exchange and magmatic degassing introduced large concentrations of trace metals into the cretaceous ocean at the same time that extinctions of benthic species turnover in plankton communities and increases in isotopically light organic carbon burial occurred the stratigraphic position of this interval of trace metal anomalies matches events associated with oae2 and indicates that intermittent hydrothermal activity on a massive scale triggered abrupt changes in carbon burial and deep ocean oxygen contents

reconstructing nutricline dynamics of mid cretaceous oceans evidence from calcareous nannofossils from the niveau paquier black shale se france abstract a high resolution calcareous nannofossil record is presented from the lower albian niveau paquier black shale from the vocontian basin se france the niveau paquier black shale represents the regional equivalent of the supraregionally distributed oceanic anoxic event 1b oae 1b to reconstruct surface water fertility a nutrient index based on zeugrhabdotus erectus discorhabdus rotatorius high fertility indicators and watznaueria barnesae low fertility indicator was established using principal component analysis in addition the distribution of nannoconus spp and absolute abundances of coccoliths coccoliths per gram were used for reconstructing nutricline dynamics of the surface waters high surface water fertility coincides with low percentages of nannoconids and vice versa moreover high percentages of nannoconids correlate with low absolute abundances of all other coccoliths based on the observed nannoplankton distribution pattern and a suggested similarity in ecological requirements between nannoconids and the modern taxon florisphaera profunda a model is proposed that couples nannoconid abundances with dynamics of the nutricline time series analyses of the nutrient index show fluctuations within the precessional band the precession controlled fluctuations of the surface water fertility may represent a monsoonal signal with the nutrient supply in the surface waters depending on the strength of monsoonal activity during periods of enhanced monsoonal activity which were characterized by humid conditions and stronger winds mixing of the upper water column was enhanced during that time the abundance of nannoconids decreased as a consequence of enhanced wind stress that improved vertical mixing and led to an entrainment of nutrients into the surface waters this resulted in an increase of primary production during periods of reduced monsoonal activity marked by drier conditions and reduced wind stress the surface waters were depleted in nutrients as a result of a deep nutricline and a reduced nutrient supply to the upper photic zone in a stratified water column percentages of nannoconids increased according to the mechanisms outlined above fluctuations of the nutrient index and nannoconid percentages have been used as a proxy for reconstructing the physical structure of mid cretaceous oceans steered by precession forced monsoonal activity the results of the study show that the formation of the lower albian oae 1b from the vocontian basin occurred under strongly fluctuating surface waters fertility

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

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

metal emissions from kilauea and a suggested revision of the estimated worldwide metal output by quiescent degassing of volcanoes abstract measurements of a large suite of metals pb cd cu zn and several others and sulfur at kilauea volcano over an extended period of time has yielded a detailed record of the atmospheric injection of ordinarily rare metals from this quiescently degassing volcano representative of an important type we have combined the kilauea data with data of recent studies by others emissions from volcanoes in the indonesian arc the large laki eruption of two centuries ago etna estimates of total volcanic emissions of sulfur to form the basis for a new working estimate of the rate of worldwide injection of metals to the atmosphere by volcanoes the new estimate is that volcanoes inject a substantially smaller mass of ordinarily rare metals into the atmosphere than was stated in a widely cited previous estimate j o nriagu a global assessment of natural sources of atmospheric trace metals nature 338 1989 47 49 our estimate which is an upper limit is an annual injection mass of about 10 000 tons of the metals considered versus the earlier estimate of about 23 000 tons also the proportions of the metals are substantially different in our new estimate

160 m y record of marine sedimentary phosphorus burial coupling of climate and continental weathering under greenhouse and icehouse conditions a compilation of all meaningful phosphate data published in the proceedings of the deep sea drilling project and the ocean drilling program is used here for the extraction of a 160 m y marine burial record of bulk phosphorus all sediment types 5648 measurements and a 100 m y marine burial record of biogenic phosphorus pelagic biogenic sediment types 1754 data these records serve as estimates for total and dissolved bioavailable phosphorus flux rates which in turn are highly dependent on total and chemical continental weathering rates respectively the similarity of both records indicates that in the past 100 m y changes in total weathering rates may have been tracked by changes in chemical weathering rates prior to 32 ma phosphorus burial and long term sea level change are positively correlated from 32 ma to the present this correlation is inverse this points to a fundamental change in feedback mechanisms between continental weathering phosphorus and climate which was probably linked to the onset of major glaciation