isotope data from cretaceous chalks and foraminifera environmental or diagenetic signals scanning electron microscopy of sediments microfossils and polished thin sections from the cenomanian turonian boundary section at dover england demonstrates that cement is concentrated within large pores such as foraminifera and calcispheres whereas the surrounding coccolith rich sediments are largely lacking in cement isotope analysis of single microfossils and cement samples indicates the presence of mixing lines between primary paleoceanographic compositions and cements consequently paleoceanographic and stratigraphic interpretations of these sediments and perhaps other similar sediments based on similar data may be suspect

effects of diagenesis on the isotopic record of late paleogene tropical sea surface temperatures abstract oxygen isotope records of planktonic foraminifera indicate that late eocene and oligocene tropical sea surface temperatures were as much as 8 c lower than present at a time when high latitude sea surface temperatures were higher than present using a numerical model which describes oxygen isotope exchange during burial and recrystallization of deep sea carbonate the effects of diagenesis on bulk carbonate 18 o records for the cenozoic are quantified for four tropical sites most of the observed variations in measured 18 o values at all sites can be accounted for by diagenetic effects there are no systematic trends that support substantial variations in tropical sea surface temperatures beyond diagenetic effects with the possible exception of the early eocene for which the data are consistent with slightly higher sea surface temperatures reconstructions based on oxygen isotope records of planktonic foraminifera which indicate cooler tropical sea surface temperatures for the eocene and oligocene may be artifacts of diagenetic recrystallization as such records are particularly sensitive to diagenetic effects

late cretaceous sea level changes in tunisia a multi disciplinary approach a multi disciplinary study of sea level and climate proxies including bulk rock and clay mineral compositions carbon isotopes total organic carbon toc sr ca ratios and macro and microfaunal associations reveals seven major sea level regressions in the southwestern tethys during the last 10 million years of the cretaceous late campanian c 74 2 ma 73 4 72 5 ma and 72 2 71 7 ma early maastrichtian 70 7 70 3 ma 69 6 69 3 ma and 68 9 68 3 ma and late maastrichtian 65 45 65 3 ma low sea levels are generally associated with increased terrigenous influx low kaolinite chlorite mica ratios high toc and high sr ca ratios whereas high sea levels are generally associated with the reverse conditions these sea level changes may be interpreted as eustatic as suggested by the global recognition of at least four of the seven major regressions identified 74 2 ma 70 7 70 3 ma 68 9 68 3 ma and 65 45 65 3 ma climatic changes inferred from clay mineral contents correlate with sea level changes warm or humid climates accompany high sea levels and cooler or arid climates generally accompany low sea levels

a stable isotopic record of the maastrichtian ocean climate system south atlantic dsdp site 528 abstract the upper maastrichtian interval of mid latitude south atlantic deep sea drilling project site 528 spans approximately the last 4 million years of the cretaceous the isotopic record of this sequence indicates that relatively large 0 5 1 0 late maastrichtian oxygen and carbon isotopic shifts occurred on geologically short time scales less than 100 500 kyr comparison with previous oxygen isotopic data suggests that in high and mid latitude southern oceans the multimillion year maastrichtian cooling trend largely resulted from geologically rapid climatic steps coincidence of the largest carbon and oxygen isotopic excursions suggests that relatively large and geologically rapid changes in marine and atmospheric carbon content may have directly contributed to the long term cooling of the late cretaceous greenhouse

upstream effects of mesoscale mountains abstract the alpine experiment alpex has revealed that low level air is typically diverted around the alps without reaching the mountaintop in pursuit of an understanding of the physical basis of this phenomenon and of its generality we have explored the characteristics of orographic blocking of a rotating continuously stratified quid as revealed in a simple model problem retaining full nonlinear and transient effects hydrostatic dynamics is assumed and the obstacle is taken to be an infinitely long ridge with height h x the key questions treated are the strength of the upstream deceleration of cross mountain flow and the length scale over which the decelerated region extends by means of scale analysis the controlling parameters are found to be the rossby number ro u fl and the froude number fr nhm u where u is the speed of the oncoming flow f is the coriolis parameter l the mountain half width n the brunt vaisala frequency and hm is the maximum mountain height the scale analysis also

18 o modelling of freshwater inputs in baffin bay and canadian arctic coastal waters 18o salinity modelling of marine environments has been proposed for various areas including some arctic seas the present report concerns arctic coastal waters collected along the west coast of greenland northern baffin bay the arctic archipelago and the north shore of alaska measurements of 18o versus salinity allow the identification of three main components marine standard water continental freshwater and sea ice meltwater continental waters may be represented by either glacial meltwater western greenland land drainage mackenzie areas or both quantitative determinations of the respective parts involved in mixed coastal waters imply a precise knowledge of the isotopic characteristics of the local continental waters these determinations may be achieved either numerically or graphically

oxygen isotope exchange in a two layer model of oceanic crust abstract a numerical model is presented for the transport and exchange of oxygen isotopes in an idealized two layer oceanic crust basalt carbonate that is saturated with a non advecting pore fluid open to the overlying ocean the model allows for time varying sedimentation rate porosity chemical diffusivity and temperature dependent 18o fractionation factors reaction is modeled as solution precipitation of calcite in the carbonate sediment and as modified solution precipitation basalt dissolves smectite precipitates in the basalt layer generic models using input parameters that are typical of those measured in dsdp odp cores and constant sedimentation rates illustrate the behavior of the system sufficiently well to allow first order effects to be discerned that have important implications for paleotemperature and ocean floor weathering studies the solution precipitation reactions allow oxygen to be exchanged between the low 18o basalt layer and the high 18o carbonate sediment through the medium of the pore fluids this results in 18o increasing upwards in the basalt and decreasing downwards in the sediment pore fluid 18o values decrease with depth from zero to values of 1 to 3 at the basalt sediment interface and to values of 7 to 15 within the basalt because reaction rates are slow relative to diffusion in the pore fluid high frequency 18o variations in the solid are preserved indefinitely but the amplitude of the variations decreases as e rt where r is the reaction rate fraction reacted per unit time the results suggest that the diagenetic shifts of the 18o values of benthic and high latitude planktonic foraminifera samples younger than oligocene age are typically negligible for samples older than 50 ma diagenetic effects are typically significant and generally cause estimates of bottom and high latitude surface ocean temperatures in the cretaceous and early tertiary to be too high on the other hand the model suggests that diagenesis will shift the 18o values of low latitude planktonic foraminifera to higher values and that paleotemperature estimates of low latitude surface waters particularly in the eocene and oligocene may be too low using a synthetic 18o record for dsdp site 167 we demonstrate how numerical models can be used to correct specific measured records for diagenesis this approach could provide a means of extracting paleotemperature information from heavily altered late cretaceous and older samples and for quantifying the subtle effects of diagenesis on the 18o record at all sites

age and paleoenvironment of the maastrichtian to paleocene of the mahajanga basin madagascar a multidisciplinary approach abstract lithology geochemistry stable isotopes and integrated high resolution biostratigraphy of the berivotra and amboanio sections provide new insights into the age faunal turnovers climate sea level and environmental changes of the maastrichtian to early paleocene of the mahajanga basin of madagascar in the berivotra type area the dinosaur rich fluvial lowland sediments of the anembalemba member prevailed into the earliest maastrichtian these are overlain by marginal marine and near shore clastics that deepen upwards to hemipelagic middle neritic marls by 69 6 ma accompanied by arid to seasonally cool temperate climates through the early and late maastrichtian an unconformity between the berivotra formation and betsiboka limestone marks the k t boundary and juxtaposes early danian zone plc or pld and latest maastrichtian zones cf2 cf1 micula prinsii sediments seasonally humid warm climates began near the end of the maastrichtian and prevailed into the early danian accompanied by increased volcanic activity during the late danian zones p1d p2 a change to seasonally arid climates was accompanied by deepening from middle to outer neritic depths

sr ca variations in cretaceous carbonates relation to productivity and sea level changes abstract we present high resolution sr ca measurements on coccolith dominated pelagic carbonates of berriasian valanginian albian santonian and campanian maastrichtian age from dsdp sites and tethyan land sections carbonate sr ca varies by up to 80 over both long and short timescales and may reflect either temporal variations in seawater sr ca or variable sr partitioning in biogenic carbonates numerical models of seawater sr and ca budgets indicate that while sea level changes can cause comparably large variations in the seawater sr ca ratio the timing and pattern of predicted sr ca variations agrees poorly with the carbonate record reef crises unrelated to sea level changes may also elevate seawater sr ca and in some cases the record of reef crises corresponds to increasing carbonate sr ca changes in sr partitioning likely due to changes in calcareous nannoplankton productivity also appear to control carbonate sr ca in these records cretaceous carbonate sr ca broadly covaries with indicators of productivity derived from microfossil ecology recent studies in sediment core tops and cultures have shown that sr partitioning in coccolith carbonate is strongly influenced by changes in coccolithophorid growth and calcification rate where the effects of changing seawater sr ca can be constrained by independent geological data carbonate sr ca measurements could provide a valuable perspective on changes in the productivity of calcareous nannoplankton and variations in the carbonate and carbon cycle in the cretaceous

stable isotope toc and caco3 record across the cretaceous tertiary boundary at el kef tunisia we report the results of stable oxygen and carbon isotope analysis of carbonate fine fraction and benthic and planktic foraminifers caco3 and toc determinations of sediments across the cretaceous tertiary k t boundary at el kef tunisia we used grain size analysis of the fine fraction carbonate to determine possible compositional effects and smearslide and scanning electron microscope examinations to evaluate possible diagenetic alteration and microfossil preservation the data suggests the following sequence of events upper maastrichtian oxygen and carbon isotope signals indicate relatively warm temperatures a decreasing thermal gradient possibly related to a shallowing sea and relatively high surface water productivity a sharp cooling appears to begin just below the k t boundary the k t boundary is characterized by a sudden 2 negative shift in fine fraction 13c a slight 0 6 enrichment in benthic 13c and a reduction of about 40 in caco3 sedimentation these data imply strongly reduced surface water productivity as also observed in numerous deep sea sequences worldwide the lower danian planktic foraminiferal zones p0 p1a is marked by generally low productivity and unstable environmental conditions as indicated by generally low but fluctuating fine fraction 13c values and low 5 15 carbonate deposition at the base of subzone p1b caco3 benthic and fine fraction 13c values increase gradually and reach near pre k t boundary levels in subzone p1c indicating initial recovery after the k t boundary event about 300 000 400 000 years after the k t boundary the prolonged low productivity episode after the k t crisis and the pre k t boundary cooling associated with a major reduction in planktic foraminiferal diversity are difficult to explain by a single k t boundary bolide impact

late maastrichtian paleoclimatic and paleoceanographic changes inferred from sr ca ratio and stable isotopes abstract milankovitch scale cycles can be recognized in high resolution 13c 18o sr ca mineralogical and magnetic susceptibility data in hemipelagic sediments that span the last 700 kyr of the maastrichtian at elles tunisia oxygen isotope data reveal three cool periods between 65 50 and 65 55 ma 21 5 23 5 m 65 26 and 65 33 ma 8 11 m and 65 04 and 65 12 ma 1 5 4 m and three warm periods between 65 33 and 65 38 ma 12 16 m 65 12 and 65 26 ma 4 8 m and 65 00 and 65 04 ma 0 1 5 m the cool periods are characterized by small surface to deep temperature gradients that reflect intensive mixing of the water column the surface to deep sr ca gradient generally correlates with the oscillating t trend temperature difference between surface and bottom waters the carbon isotope composition of planktonic foraminifera indicates a continuous decrease in surface bioproductivity during late maastrichtian decreasing 13c values difference between the 13c values of surface and bottom dwelling foraminifera and the carbon isotope ratios of the planktonic species at the onset of gradual warming at 65 50 ma reflect a reduction in surface productivity as a result of decreased upwelling that accompanied global warming and possibly increased atmospheric pco2 related to deccan trap volcanism time series analysis applied to magnetic susceptibility 18o and sr ca data identifies the 20 kyr precession 40 kyr obliquity and 100 kyr eccentricity milankovich cycles

potential for southern hemisphere climate surprises climate model results suggest that future climate change in antarctica will be accompanied by continued strengthening and poleward contraction of the southern ocean westerly wind belt paleoclimate records suggest past changes in the westerly winds can be abrupt and that healing of the antarctic ozone hole could lead to poleward contraction of the westerlies and increased meridional atmospheric transport of warm air regionally into antarctica an abrupt shift to more meridional circulation could lead to notable changes in moisture availability for extra antarctic regions increased antarctic ice sheet disintegration and more rapid sea level rise copyright 2015 the authors journal of quaternary science published by john wiley sons ltd

stable isotope and foraminiferal changes across the cretaceous tertiary boundary at stevns klint denmark arguments for long term oceanic instability before and after bolide impact event abstract stable isotope and planktic and benthic foraminiferal analyses of the k t boundary transition at stevens klint denmark indicate a 100 500 kyr long period of instability in oceanic bottom water temperature and sea level during the latest maastrichtian from 2 7 m below and up to the k t boundary bottom water temperatures gradually cooled about 1 5 c as surface water temperatures remained constant at the k t boundary bottom water temperatures decreased additionally 3 c and then returned to pre boundary values just above the boundary interval coincident with the onset of the first temperature decrease there was a prominent sea level fall estimated between 50 100 m as observed in benthic and planktic foraminiferal assemblages as well as in a decreasing surface to bottom 13 c gradient about 40 cm below the iridium rich k t boundary clay sea level began to rise poor preservation of foraminifera above the k t boundary allows only tentative interpretation of danian events at stevns klint however sea level generally continued to rise interrupted by short sea level falls associated with the observed sea level changes are three important hiatuses at the contact between the white chalk and overlying grey white bryozoan chalk about 2 7 m below the k t boundary at or near the top of the fish clay zone pla parvularugoglobigerina eugubina missing and at the contact of the cerithium limestone and overlying bryozoan limestone about 60 cm above the k t boundary part of zone plc missing these unconformities are coeval with hiatuses observed in many continental shelf sections and indicate a global eustatic rather than regional isostatic response notable is that at stevns klint the episode of oceanic instability is registered over approximately the same stratigraphic interval in which supposed extraterrestrial amino acids occur a circumstance that may indicate a connection a gradual positive shift in 13 c is registered in both benthic and planktic foraminiferal assemblages in the upper maastrichtian at stevns klint the positive shift is followed by a prominent negative 13 c shift 1 3 at the k t boundary an upper maastrichtian positive 13 c excursion followed by a negative 13 c anomaly at or near the k t boundary has previously been observed in deep sea cores from the pacific ocean and the weddell sea antarctica implying a global event previous suggestions of a relation between the uppermost maastrichtian positive 13 c excursion and sea level variation are not supported by the data for stevns klint

trace elements stable isotopes and clay mineralogy of the elles ii k t boundary section in tunisia indications for sea level fluctuations and primary productivity abstract trace elements and stable isotopes in bulk rocks and foraminifera bulk rock and clay mineral compositions are used as palaeoproxies to evaluate sea level fluctuations climatic changes and variations in primary productivity across the k t transition at elles ii in tunisia from 1 m 33 kyr below to 1 m 70 kyr above the k t boundary results on clay minerals major and trace elements stable isotopes in bulk rock samples e g ca cu zn rb sr zr ba 13c and 18o and in foraminifera sr ca 13c 18o indicate that the latest maastrichtian last 33 kyr in tunisia was marked by a relatively warm but humid climate and a rising sea level the transgressive surface is marked by deposition of a foraminiferal packstone just below the k t boundary followed by maximum flooding across the k t boundary red layer and black clay layer humid warm conditions accompanied the maximum flooding along with increased total organic carbon values and rapidly decreasing primary productivity at the k t boundary an impact event ir anomaly ni rich spinels spherules exacerbated already stressed environmental conditions leading to the mass extinction of tropical planktic foraminifera increasingly more humid conditions prevailed within the lowermost danian zone p0 50 kyr culminating in a sea level lowstand near the top of p0 a slow recovery of the ecosystem in zone p1a coincided with a rising sea level and gradually less humid climatic conditions

decline of the maastrichtian pelagic ecosystem based on planktic foraminifera assemblage change implication for the terminal cretaceous faunal crisis an outer shelf upper slope tropical tethyan pelagic environment existed over southern israel during maastrichtian time planktic foraminifera in the 63 and 149 m size fractions from four sections in this area were studied quantitatively for a high resolution ecostratigraphic analysis of the pre cretaceous tertiary k t paleoenvironment during the maastrichtian 41 of the planktic foraminifera species became extinct mostly keeled globotruncanidae which also became quantitatively reduced near the end of the maastrichtian from as much as 35 to only 5 of the planktic foraminifera population evolutionary replacement of extinct species by new forms nearly ceased in that interval two major opportunistic blooms of guembelitria took place associated with reduced abundances of keeled forms and the dominant species heterohelix globulosa the first bloom occurred within the upper gansserina gansseri to lower abathomphalus mayaroensis zones and the second within the plummerita hantkeninoides zone the extinctions concomitant changes in faunal dominance and opportunist blooms indicate that the pelagic ecosystem in the negev area experienced multiple stresses during the maastrichtian the planktic foraminiferal assemblages were taxonomically impoverished and in decline prior to the k t boundary crisis

original oxygen isotopic composition of planktic foraminifers preserved in diagenetically altered pleistocene shallow marine carbonates abstract the original stable isotopic composition of low mg calcitic planktic foraminifer tests is preserved in pleistocene shallow marine carbonates in the ryukyu group okinawa japan that have been altered by meteoric diagenesis whole rock analyses indicate depleted isotopic values for both 13 c 1 9 to 5 4 and 18 o 2 9 to 5 2 as well as carbonate mineralogy exclusively composed of low mg calcite however analysis of carefully extracted planktic foraminifer tests globigerinoides sacculifer that were separated from these whole rock samples yield heavier 13 c values 0 4 to 1 9 and 18 o values 3 2 to 1 0 the foraminiferal values themselves and comparison of values of various components suggest that the low mg calcite tests preserve the original stable isotopic values subsequently the downcore 18 o change of planktic foraminifers recorded in the ryukyu group results from middle pleistocene glacial interglacial change by comparison isotopic measurements based on whole rock samples can be obtained diagenetic environmental signals but misleading with regard to paleoclimatic inferences

terminal cretaceous warming event in the mid latitude south atlantic ocean evidence from poleward migration of contusotruncana contusa planktonic foraminifera morphotypes abstract spatial and temporal patterns in test size and shape test conicity and spiral roundness and absolute abundance accumulation rate of the planktonic foraminifer contusotruncana contusa were studied in the south atlantic ocean dsdp sites 356 516 525 and 527 during an interval corresponding to the last 800 kyr of the cretaceous the variation in absolute abundance of c contusa was characterised by alternating periods of high and low abundance some of these periods were traceable across the entire mid latitude south atlantic ocean while the mean spiral roundness did not show any interpretable patterns a sudden increase of the mean test size and mean test conicity occurred between 65 3 and 65 2 ma based on linear interpolation within the cretaceous part of subchron c29r at all sites studied indicating a poleward migration followed by rapid withdrawal of the low latitude c contusa morphotypes from the mid latitude south atlantic ocean we suggest that this event was caused by a short period of surface water warming in the southern mid latitudes corresponding to the brief high latitude warming event and associated faunal migrations in the boreal and austral realms

reconstructing past sea surface temperatures correcting for diagenesis of bulk marine carbonate abstract a numerical model which describes oxygen isotope exchange during burial and recrystallization of deep sea carbonate is used to obtain information on how sea surface temperatures have varied in the past by correcting measured 18o values of bulk carbonate for diagenetic overprinting comparison of bulk carbonate and planktonic foraminiferal 18o records from odp site 677a indicates that the oxygen isotopic composition of bulk carbonate does reflect changes in sea surface temperature and 18o at odp site 690 we calculate that diagenetic effects are small and that both bulk carbonate and planktonic foraminiferal 18o records accurately reflect paleogene warming of high latitude surface oceans biased from diagenesis by no more than 1 c the same is likely to be true for other high latitude sites where sedimentation rates are low at dsdp sites 516 and 525 the effects of diagenesis are more significant measured 18o values of eocene bulk carbonates are more than 2 lower at deeply buried site 516 than at site 525 consistent with the model prediction that the effects of diagenesis should be proportional to sedimentation rate model corrections reconcile the differences in the data between the two sites the resulting paleotemperature reconstruction indicates a 4 c cooling of mid latitude surface oceans since the eocene at low latitudes the contrast in temperature between the ocean surface and bottom makes the carbonate 180 values particularly sensitive to diagenetic effects most of the observed variations in measured 18o values are accounted for by diagenetic effects rather than by sea surface temperature variations we show that the data are consistent with constant equatorial sea surface temperatures through most of the cenozoic with the possible exception of the early eocene when slightly higher temperatures are indicated we suggest that the lower equatorial sea surface temperatures for the eocene and oligocene reported in other oxygen isotope studies are artifacts of diagenetic recrystallization and that it is impossible to reconstruct accurately equatorial sea surface temperatures without explicitly accounting for diagenetic overprinting

temperature control on the incorporation of magnesium strontium fluorine and cadmium into benthic foraminiferal shells from little bahama bank prospects for thermocline paleoceanography surface sediments from little bahama bank lbb intersecting the subtropical thermocline were used to assess the influence of temperature on the incorporation of mg sr f and cd into shells of benthic foraminifera samples were obtained from twelve cores along the southern slope of lbb covering a temperature range of 18 4 5 c between 301 and 1585 m we studied the composition of ten calcitic and one aragonitic species which are often used in paleochemical reconstructions mg ca ratios decrease with increasing water depth in all benthic species both with calcitic and aragonitic mineralogy showing a strong correlation with water temperature similar decrease is seen in sr ca but with no correlation with temperature none of the benthic species studied here exhibits a depth or temperature related change in f ca similar trends are observed when using an ocean wide dataset which includes shallow and deep core tops 300 5000 m we suggest that temperature is the primary control on the mg content of benthic foraminifera based on inorganic precipitation experiments and thermodynamic considerations presented here a 30 40 decrease in the mg distribution coefficient in calcite may be expected as a result of a temperature change from 25 c to 5 c which is about half the observed change in lbb a calibration curve applied to c pachyderma data from core tops along the slope of little bahama bank suggests that water temperature may be inferred from mg ca ratios with an uncertainty of about 0 8 c therefore the mg content of benthic foraminifera may provide a new independent temperature proxy for studying shallow waters paleoceanography the linear decrease in sr ca with increasing depth is not correlated with temperature the trend is constant from the ocean surface down to 5 km suggesting that pressure related effects on the calcification process are a more likely explanation than post depositional dissolution mg ca ratios in aragonitic shells of h elegans covary with temperature in accord with recent observations from corals in contrast the sr and f chemistry of h elegans is very different than that of corals and inorganically precipitated aragonites the disparities between the elemental composition of biogenic and inorganic phases and the large intergeneric and interspecific differences observed both in planktonic and benthic foraminifera implicate temperature related physiological processes in regulating the coprecipitation of elements in foraminiferal shells our work demonstrates that cd ca ratios of shallow calcitic species reflect the vertical distribution of nutrients no significant influence of temperature on the partitioning of cd into the shells was found our data extend the previous deep water calibration boyle 1992 thereby allowing for the reconstruction of the nutrient chemistry of shallow thermocline waters

magnesium and strontium compositions of recent benthic foraminifera from the coral sea australia and prydz bay antarctica analyses of the mg ca and sr ca ratios of the modern benthic foraminifera cibicides wuellerstorfi epifaunal and uvigerina species infaunal from the coral sea and cibicides refulgens epifaunal and trifarina angulosa infaunal from prydz bay antarctica revealed relationships with temperature that have possible applications for reconstructions of bottom water paleotemperatures a positive relationship exists between the mg ca and sr ca ratios of cibicides wuellerstorfi and cibicides refulgens and ambient temperatures at least within the range of 2 and 6 c for the correlation between mg ca compositions and temperature the r2 values range from 0 78 c wuellerstorfi alone to 0 88 c wuellerstorfi and c refulgens together at present the mg ca temperature relationship must be regarded as tentative because of significant overlap of standard error values the relationship between the sr ca compositions of c wuellerstorfi and bottom water temperature yields an r2 value of 0 95 these results indicate that sr ca and possibly mg ca ratios of cibicides wuellerstorfi may provide useful information for the assessment of paleotemperature single species data are presently insufficient to assess the influence of ambient temperature on trace element compositions of uvigerina species trifarina angulosa may have mg ca compositions which are positively related to temperature but sr ca values seem unaffected by temperature this may be due to pore water influences on infaunal tests or to vital effects although more modern data are needed our present results suggest that sr ca ratios and possibly mg ca ratios of some benthic foraminifera have the potential to be useful paleothermometers at least within a temperature range of 2 to 6 c

gradual mass extinction species survivorship and long term environmental changes across the cretaceous tertiary boundary in high latitudes stable isotope and planktic foraminiferal analyses across the cretaceous tertiary k t boundary transition at nye klov indicate longterm oceanic instability associated with global sea level fluctuations a gradual mass extinction and decreased magnitude of the 13 c shift in high latitudes oceanic instability which began at least 100 kyr before the k t boundary and continued for about 300 kyr into the tertiary was accompanied by a gradual faunal turnover the maximum sea level lowstand during latest maastrichtian is recorded about 75 cm below the k t boundary a sea level rise first in evidence at 20 cm to 40 cm below the boundary continued into zone p0 boundary clay this sea level rise was accompanied by 2 c of cooling in surface and bottom waters prior to the k t boundary 13 c values remained relatively stable up to 10 cm below the k t boundary a negative shift of 0 5 to 1 0 per mil occurred in the boundary clay in both planktic and benthic foraminifera the surface to deep 13 c gradient remained nearly unchanged in contrast to low latitudes where this gradient is virtually eliminated no sudden mass extinction occurred in this cosmopolitan high latitude fauna and nearly all cretaceous taxa thrived well into the tertiary when they gradually disappeared shallow seas dominated by cretaceous survivor taxa and a well developed oxygen minimum zone prevailed during the earliest tertiary short term sea level lowstands are marked by hiatuses at the top of zones p0 and p1a about 50 kyr and 230 kyr after the k t boundary respectively rising sea level reestablished normal marine conditions about 300 kyr to 350 kyr after the k t boundary coincident with the first post k t boundary recovery of the tertiary fauna and extinction of cretaceous survivors during this time high latitude regions temporarily acted as centers of origin and dispersal for planktic foraminifera long term oceanic instability gradual faunal turnover absence of a sudden mass extinction and greatly diminished 13 c shift in high latitudes suggest that a k t boundary bolide impact was not the primary cause for the k t boundary faunal transition moreover these data strongly imply that the destructive effects of the bolide impact would have been greatest in low latitudes and negligible in high latitudes

paleoecology of the cretaceous tertiary mass extinction in planktonic foraminifera abstract paleobiogeographic patterns of the cretaceous tertiary k t mass extinction in planktonic foraminifera in tunisia spanning environments from open marine upper bathyal to shelf and shallow marginal settings indicate a surprisingly selective and environmentally mediated mass extinction this selectivity is apparent in all of the environmental proxies used to evaluate the mass extinction including species richness ecological generalists ecological specialists surface and subsurface dwellers whether based on the number of species or the relative percent abundances of species the following conclusions can be reached for shallow to deep environments about three quarters of the species disappeared at or near the k t boundary and only ecological generalists able to tolerate wide variations in temperature nutrients salinity and oxygen survived among the ecological generalists heterohelicids guembelitrids hedbergellids and globigerinellids only surface dwellers survived ecological generalists which largely consisted of two morphogroups of opportunistic biserial and triserial species also suffered selectively biserials thrived during the latest maastrichtian in well stratified open marine settings and dramatically declined in relative abundances in the early danian triserials thrived only in shallow marginal marine environments or similarly stressed ecosystems during the latest maastrichtian but dominated both open marine and restricted marginal settings in the early danian this highly selective mass extinction pattern reflects dramatic changes in temperature salinity oxygen and nutrients across the k t boundary in the low latitude tethys ocean which appear to be the result of both long term environmental changes e g climate sea level volcanism and short term effects bolide impact

recent change of hydrographic features in the cheju strait southeastern yellow sea korea contrast between planktonic and benthic foraminifera isotope composition abstract ams 14 c dates on a 260 cm long gravity core npc 2 collected from the cheju strait southeastern yellow sea revealed that the core sediments were deposited only during the last 1200 yr b p under such relatively rapid sediment deposition about 2 mm yr of sedimentation rate the 18 o and 13 c compositions of planktonic globigerionoides bulloides and benthic ammonia beccarii s l foraminifera provide a new information on the evolution of surface and bottom water masses in the study area the discrepancies of 18 o and 13 c values between planktonic and benthic foraminifera were consistent between the bottom and 50 cm downcore whereas both values diverged gradually in the upper 50 cm of core and the difference reaches at maximum at the top of core in accordance with the linear covariances between 18 o and 13 c values of both planktonic and benthic foraminifera a common principal factor to govern the isotopic composition of foraminiferal calcite may be judged considering not only temperature fractionation of calcite but gradients of salinity to 18 o w of seawater the isotopic variation and excursion in the upper part of core npc 2 suggest that the contribution from the gradual decreasing salinity be emphasized in contrast with increasing temperatures at the surface layer the low salinity waters have accumulated greatly during the last 250 yr part of which is likely to result from the divergence of huanghe river mouth thus the modern hydrographic changes are recorded as the negative shift of 18 o and 13 c values in the shallow yellow sea

evidence for glacial control of rapid sea level changes in the early cretaceous lower cretaceous bulk carbonate from deep sea sediments records sudden inputs of strontium resulting from the exposure of continental shelves strontium data from an interval spanning 7 million years in the berriasian valanginian imply that global sea level fluctuated about 50 meters over time scales of 200 000 to 500 000 years which is in agreement with the exxon sea level curve oxygen isotope measurements indicate that the growth of continental ice sheets caused these rapid sea level changes if glaciation caused all the rapid sea level changes in the cretaceous that are indicated by the exxon curve then an antarctic ice sheet may have existed despite overall climatic warmth

high stress late maastrichtian paleoenvironment inference from planktonic foraminifera in tunisia high resolution v5 10 kyr planktonic foraminiferal analysis at elles tunisia reveals major changes in the structure of the tethyan marine ecosystem during the upper maastrichtian during the first 1 5 myr of the late maastrichtian 68 3 66 8 ma relatively stable environmental conditions and cool temperatures are indicated by diverse planktonic foraminiferal populations with abundant intermediate and surface dwellers a progressive cooling trend between v66 8 65 45 ma resulted in the decline of globotruncanid species intermediate dwellers this group experienced a further decline at the climax of a rapid warm event about 300 kyr before the k t boundary at the same time relative abundances of long ranging dominant species fluctuated considerably reflecting the high stress environmental conditions times of critical high stress environments during the late maastrichtian and particularly at the k t boundary are indicated by low species diversity and blooms of the opportunistic genus guembelitria at warm cool transition intervals during the last 100 kyr of the maastrichtian rapid cooling is associated with accelerated species extinctions followed by the extinction of all tropical and subtropical species at the k t boundary fl 2002 elsevier science b v all rights reserved

a biomineralization model for the incorporation of trace elements into foraminiferal calcium carbonate measurements of srca of benthic foraminifera show a linear decrease with water depth which is superimposed upon significant variability identified by analyses of individual foraminifera new data for cdca support previous work in defining a contrast between waters shallower and deeper than 2500 m measured element partition coefficients in foraminiferal calcium carbonate relative to sea water d have been described by means of a one box model in which elements are extracted by rayleigh distillation from a biomineralization reservoir that serves for calcification with a constant fractionation factor such that d 1 f 1 f where f is the proportion of ca remaining after precipitation a modification to the model recognises differences in element speciation the model is consistent with differences between dsr dba and dcd in benthic but not planktonic foraminifera depth variations in d for sr and ba are consistent with the model as are differences in depth variation of dcd in calcitic and aragonitic benthic foraminifera the shallower depth variations may reflect increasing calcification rates with increasing water depth to an optimum of about 2500 m observations of unusually lower dcd for some deep waters not accompanied by similar dsr or dba may be because of dissolution or a calcification response to a lower carbonate saturation state

the oxygen and carbon isotope distribution in the mediterranean water masses abstract the oxygen and carbon stable isotope compositions of the present day mediterranean waters have been measured in order to evaluate their variability which is related to the specific climatic and hydrological conditions within the basin the experimental equation between the 18 o value and the salinity of water based on 300 measurements on surface intermediate and deep waters sampled during the vicomed 2 and 3 cruises in the western central and eastern mediterranean has a slope of 0 27 a value which is significantly lower than the slope of 0 45 as defined in the northeast atlantic ocean this difference in the 18 o salinity relationship which occurs immediately in the alboran basin is basically a characteristic of the climatic regime of the mediterranean i e of an excess evaporation over fresh water input the largest variations of these two parameters 18 o of water and 13 c of co 2 are observed in the surface waters mostly in the western mediterranean this evolution mirrors the progressive eastward restriction which separates the less evaporated and more productive western basins from the more evaporated and less productive eastern basins the intermediate waters constitute a homogeneous layer however their 18 o values decrease eastward by 0 35 at maximum due to progressive dilution by mixing with overlying and underlying water masses their 13 c values decrease also eastward by 0 35 at maximum due to an increasing input of nutrients issued from the regeneration of sinking organic particles the deep waters have similar 18 o values but slightly higher 13 c values often by less than 0 1 than the overlying intermediate waters indicating generally well ventilated conditions due to active winter convection

temperature dependence of the strontium distribution coefficient in calcite an experimental study from 408 degrees to 2008 degrees c and application to natural diagenetic calcites abstract the temperature dependence of sr coprecipitation with calcite was determined experimentally in solutions with sr ca ratios and ionic strengths closely resembling marine pore fluids aragoniteto calcite and dolomite to calcite transformations were conducted over a temperature range from 40 to 200 c temperature dependence of the distribution coefficient of strontium in calcite dcsr is significant dcsr in aragonite to calcite experiments varied from 0 046 at 40 c to 0 068 at 200 c dcsr in dolomite to calcite experiments varied from 0 034 at 40 c to 0 062 at 200 c experimental values of dcsr are somewhat dependent on the precursor phase the experimental results are applied to natural diagenetic and hydrothermal calcites recovered from the sediment covered middle valley part of the juan de fuca ridge spreading center ocean drilling program holes 857c and 858d low mg calcites from hole 858d have sr contents appropriate for their present day in situ temperatures and pore water sr values in contrast high mg calcites from hole 858d that precipitated from supersaturated pore waters at inferred high growth rates have elevated sr contents relative to calculated equilibrium values the sr contents of calcites from hole 857c are close to predicted equilibrium values in some instances but are substantially different in others deviations from predicted equilibrium sr contents especially in nodules are attributed to the formation of mixed generations of carbonate precipitating with increasing burial depths and temperatures through pore waters with variable sr composition