rapid stepwise onset of antarctic glaciation and deeper calcite compensation in the pacific ocean the ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution is termed the calcite compensation depth at present this depth is 4 500 m with some variation between and within ocean basins the calcite compensation depth is linked to ocean acidity which is in turn linked to atmospheric carbon dioxide concentrations and hence global climate1 geological records of changes in the calcite compensation depth show a prominent deepening of more than 1 km near the eocene oligocene boundary 34 million years ago 2 when significant permanent ice sheets first appeared on antarctica3 4 5 6 but the relationship between these two events is poorly understood here we present ocean sediment records of calcium carbonate content as well as carbon and oxygen isotopic compositions from the tropical pacific ocean that cover the eocene oligocene boundary we find that the deepening of the calcite compensation depth was more rapid than previously documented and occurred in two jumps of about 40 000 years each synchronous with the stepwise onset of antarctic ice sheet growth the glaciation was initiated after climatic preconditioning7 by an interval when the earth s orbit of the sun favoured cool summers the changes in oxygen isotope composition across the eocene oligocene boundary are too large to be explained by antarctic ice sheet growth alone and must therefore also indicate contemporaneous global cooling and or northern hemisphere glaciation

antarctic mass rates from grace 1 we estimate mass trends over antarctica using gravity variations observed by the gravity recovery and climate experiment grace satellite mission during its first 3 5 years april 2002 november 2005 an image of surface mass trends is constructed from 1 1 pixels over the entire continent and shows two prominent features a region of mass loss along the coast of west antarctica and one of accumulation in east antarctica after adjusting for bias due to smoothing and to grace s limited spatial resolution and removing post glacial rebound pgr effects the rate in west antarctica is 77 14 km3 year similar to a recent estimate of ice mass loss from satellite altimetry and remote sensing data the prominent east antarctic feature in the enderby land region has a rate of 80 16 km3 year published snow ice mass rates from remote sensing measurements indicate approximate ice mass balance in this region suggesting that this feature is either from unquantified snow accumulation in this region or more likely due to unmodeled pgr

methods for inferring regional surface mass anomalies from gravity recovery and climate experiment grace measurements of time variable gravity 1 the gravity recovery and climate experiment grace will deliver monthly averages of the spherical harmonic coefficients describing the earth s gravity field from which we expect to infer time variable changes in mass averaged over arbitrary regions having length scales of a few hundred kilometers and larger to accuracies of better than 1 cm of equivalent water thickness these data will be useful for examining changes in the distribution of water in the ocean in snow and ice on polar ice sheets and in continental water and snow storage we describe methods of extracting regional mass anomalies from grace gravity coefficients spatial averaging kernels were created to isolate the gravity signal of individual regions while simultaneously minimizing the effects of grace observational errors and contamination from surrounding glacial hydrological and oceanic gravity signals we then estimated the probable accuracy of averaging kernels for regions of arbitrary shape and size

explosion contamination of the northeast siberian seismicity catalog implications for natural earthquake distributions and the location of the tanlu fault in russia russian regional seismicity catalogs including those in the annual earthquakes of the ussr are contaminated by industrial explosions in northeastern russia explosions occur in tin coal and gold mines as well as in the construction of roads railways and dams most seismically recorded mining and construction related explosions have magnitudes of about 2 0 and occur during local daytime in addition explosions in placer mining areas are concentrated from midwinter to early spring when frozen placers are broken up for the summer processing season we analyzed the temporal variation of over 87 000 events occurring in northeast russia using a newly compiled seismicity catalog to identify areas where there may be explosion contamination areas with temporal biases indicative of mining or other explosions include the yana river delta and chukotka placers the southern amur district coal mining the trace of the baikal amur railroad construction lazo quarry the south yakutian gold fields and the kolyma gold belt the locations and estimates of the level of explosion contamination of the catalog suggest that the natural seismicity may be lower and not as diffuse along the plate boundaries in northeastern russia than previously thought use of only nighttime events from the seismicity catalog which should have a minimum of explosions helps to clarify the extension of the tanlu fault into russia and may ultimately help elaborate tectonics in other areas of eastern russia

planktonic foraminiferal biostratigraphy and mechanisms in the extinction of morozovella in the late middle eocene the muricate planktonic foraminiferal genera morozovella and acarinina were abundant and diverse during the upper palaeocene to middle eocene and dominated the tropical and subtropical assemblages a significant biotic turnover in planktonic foraminifera occurred in the latest middle eocene with a notable reduction in the acarininid lineage and the extinction of the morozovellids these genera are extensively employed as palaeoclimatic and biostratigraphic markers and therefore this turnover episode is an important event in the record of the cenozoic planktonic foraminifera sediments from the western north atlantic ocean drilling program site 1052 were examined in order to investigate these extinction events in terms of both timing and mechanisms biostratigraphic events of the middle and late eocene have been examined with a sampling resolution of approximately 3 kyr these have been calibrated to the magneto and astrochronology to accurately define the timing of key biostratigraphic events particularly the extinction of morozovella spinulosa which is a distinct biomarker for late middle eocene sediments high resolution biostratigraphy reveals that the extinctions in the muricate group occurred in a stepwise form the large acarininids acarinina praetopilensis terminate 10 kyr prior to the extinction of m spinulosa and small acarininids acarinina medizzai and acarinina echinata continue into the upper eocene high resolution stable isotope analyses have been conducted on planktonic and benthic foraminifera from the western north atlantic to reconstruct sea surface temperatures ssts and deep water temperatures and the structure of the water column around this major biotic turnover whilst the extinctions of m spinulosa and a praetopilensis occur during a long term cooling trend the biotic turnover in the muricate group does not appear to be related to significant climatic change sea surface temperatures decrease slowly prior to the extinction events and there is no evidence for a large temperature shift associated with the faunal changes the turnover event was therefore probably related to the increased surface water productivity and the deterioration of photosymbiotic partnerships with algae d 2003 elsevier b v all rights reserved

significant southern ocean warming event in the late middle eocene a prominent middle eocene warming event is identified in southern ocean deep sea cores indicating that long term cooling through the middle and late eocene was not monotonic at sites on maud rise and the kerguelen plateau a distinct negative shift in 1 8 o values 1 0 is observed ca 41 5 ma this excursion is interpreted as primarily a temperature signal with a transient warming of 4 c over 600 k y affecting both surface and middle bathyal deep waters in the indian atlantic region of the southern ocean this isotopic event is designated as the middle eocene climatic optimum and is interpreted to represent a significant climatic reversal in the midst of middle to late eocene deep sea cooling the lack of a significant negative carbon isotope excursion as observed during the paleocene eocene thermal maximum and the gradual rate of high latitude warming suggest that this event was not triggered by methane hydrate dissociation rather a transient rise in pco 2 levels is suspected possibly as a result of metamorphic decarbonation in the himalayan orogen or increased ridge arc volcanism during the late middle eocene

multiple early eocene benthic foraminiferal assemblage and δ13c fluctuations at dsdp site 401 bay of biscay ne atlantic abstract within the last decade several early eocene hyperthermals have been detected globally these transient warming events have mainly been characterized geochemically using stable isotopes carbonate content measurements or xrf core scanning yet detailed micropaleontological records are sparse limiting our understanding of the driving forces behind hyperthermals and of the contemporaneous paleoceanography here detailed geochemical and quantitative benthic foraminiferal records are presented from lower eocene pelagic sediments of deep sea drilling project site 401 bay of biscay northeast atlantic in calcareous nannofossil zone np11 several clay enriched levels correspond to negative 13c and 18o bulk rock excursions with amplitudes of up to 0 75 suggesting that significant injections of 12c enriched greenhouse gasses and small temperature rises took place coeval with several of these hyperthermal events the benthic foraminiferal record reveals increased relative abundances of oligotrophic taxa e g nuttallides umbonifera and a reduction in the abundance of buliminid species followed by an increase of opportunistic taxa e g globocassidulina subglobosa and gyroidinoides spp these short lived faunal perturbations are thought to be caused by reduced seasonality of productivity resulting in a decreased corg flux to the seafloor moreover the sedimentological record suggests that an enhanced influx of terrigenous material occurred during these events additionally the most intense 13c decline here called level gives rise to a small yet pronounced long term shift in the benthic foraminiferal composition at this site possibly due to the reappraisal of upwelling and the intensification of bottom water currents these observations imply that environmental changes during smaller hyperthermal events are also reflected in the composition of deep sea benthic communities on both short

organic carbon burial following the middle eocene climatic optimum in the central western tethys we present trace metal geochemistry and stable isotope records for the middle eocene alano di piave section ne italy deposited during magnetochron c18n in the marginal tethys ocean we identify a sim 500 kyr long carbon isotope perturbation event we infer to be the middle eocene climatic optimum meco confirming the northern hemisphere expression and global occurrence of meco interpreted peak climatic conditions are followed by the rapid deposition of two organic rich intervals le 3 toc and contemporaneous positive delta 13 c excursions these two intervals are associated with increases in the concentration of sulphur and redox sensitive trace metals and low concentrations of mn as well as coupled with the occurrence of pyrite together these changes imply low possibly dysoxic bottom water o 2 conditions promoting increased organic carbon burial we hypothesize that this rapid burial of organic carbon lowered global it p co 2 following the peak warming and returned the climate system to the general eocene cooling trend

extinction and recovery of benthic foraminifera across the paleocene eocene thermal maximum at the alamedilla section southern spain abstract a complete succession of lower bathyal upper abyssal sediments was deposited across the paleocene eocene thermal maximum petm at alamedilla betic cordillera southern spain where the benthic foraminiferal turnover and extinction event associated with the negative carbon isotope excursion cie across the petm have been investigated detailed quantitative analyses of benthic foraminifera allowed us to distinguish assemblages with paleoecological and paleoenvironmental significance pre extinction fauna extinction fauna survival fauna including disaster and opportunistic fauna and recovery fauna these assemblages have been associated with significant parts of the 13 c curve for which a relative chronology has been established the correlation between the benthic turnover the 13 c curve the calcite and silicate mineral content and sedimentation rates allowed us to establish the sequence of events across the petm at alamedilla the benthic extinction event bee affected 37 of the species and it has been recorded over a 30 cm thick interval that was deposited in c a 10 ky suggesting a gradual but rapid pattern of extinction the beginning of the bee coincides with the onset of the cie 0 ky and with an interval with abundant calcite and it has been recorded under oxic conditions at the seafloor as inferred from the benthic foraminiferal assemblages and the reddish colour of the sediments we conclude that dissolution and dysoxia were not the cause of the extinctions which were probably related to intense warming that occurred before the onset of the cie the bee is immediately overlain by a survival interval dominated by agglutinated species the glomospira acme the low calcite content recorded within the survival interval may result from the interaction between dilution of the carbonate compounds by silicicate minerals as inferred from the increased sedimentation rates and the effects of carbonate dissolution triggered by the shoaling of the ccd we suggest that glomospira species disaster fauna may have bloomed opportunistically in areas with methane dissociation in and around the north atlantic the disaster fauna was rapidly replaced by opportunistic taxa which point to oxic and possibly oligotrophic conditions at the seafloor the ccd gradually dropped during this interval and calcite preservation improved towards the recovery interval during which the 13 c values and the calcite content recovered c a 71 25 to 94 23 ky and stabilized 94 23 ky coeval with a sharp decrease in sedimentation rates

a benthic foraminiferal record of paleocene sea level and trophic redox conditions at gebel aweina egypt we quantitatively analyzed benthic foraminiferal assemblages in order to reveal biotic and paleoenvironmental trends in the paleocene section of gebel aweina egypt on the southern tethyan shelf the first correspondence axis ranks taxa along an empirically derived bathymetric gradient with neritic taxa e g discorbis duwi and haplophragmoides walteri opposed to bathyal taxa e g nuttallides truempyi and gavelinella beccari ormis the estimated paleodepth as reflected by the various assemblages was mostly 200 m but varied between 50 m p3a np4 and 300 m p4 n p8 the resultant four relative sea level cycles appear to be at least of regional extent and may in part be eustatically controlled the second correspondence axis reflects trends in trophic and redox development low food high oxygen conditions prevailed during biochrons plc p3b np4 np5 and late p4 np8 when assemblages were mostly dominated by cibicidoides spp most oligotrophic conditions coincided with maximum paleodepth intermediate trophic levels were established during middle p4 np6 and early p5 np9 from the level of the latest paleocene benthic extinction event bee middle p5 and np9 onwards until biochron p6a np10 assemblages dominated by buliminids marked increased trophic levels and reduced ventilation probably resulting from enhanced surface productivity enhanced surface productivity along the southern tethyan margin started during biochron p4 and at least on some shelves intensified after the bee increasing productivity during the latest paleocene contrasts with global trends this may be expected during climatic warming and an expanding trophic resource continuum leading to regionally intensified eutrophy and oligotrophy high productivity through upwelling along the southern tethyan provides support for gcm predictions of intense wind stress in this region during the warm late to latest paleocene 1998 elsevier science b v

changes in southern ocean bottom water environments associated with the middle eocene climatic optimum meco abstract the middle eocene climatic optimum meco was a 650 kyr long interval of pronounced warmth superimposed on the long term eocene cooling trend we investigate benthic foraminiferal assemblage and fossil fish tooth cerium anomaly variability from ocean drilling program odp site 738 in the indian sector of the southern ocean southern kerguelen plateau to assess changes in bottom water chemistry and effects on benthic foraminiferal ecosystems the studied section spans 41 9 to 38 4 ma encompassing the meco as well as extensive pre meco and post meco intervals we report a marked faunal turnover at 40 4 ma 200 kyrs after the onset of the meco at 40 6 ma from an assemblage dominated by epifaunal benthic foraminifera to an infaunal dominated assemblage the infaunal domination persisted until the termination of the meco at 39 95 ma thereafter the pre meco assemblage returned this change is attributed to an increase in export productivity associated with the warming possibly caused by an increase in continental runoff or the influence of a more eutrophic surface water mass superimposed on the change in tropic state the ce ce record shows a positive excursion during the 100 kyrs long meco peak warming at around 40 05 ma indicative of a decrease in bottom water oxygen content synchronously infaunal benthic foraminifera drop briefly in abundance hence we suggest that the peak warming is associated with bottom water oxygen depletion potentially caused by elevated productivity and or a transient influence of an older oxygen depleted water mass

new biostratigraphic magnetostratigraphic and isotopic insights into the middle eocene climatic optimum in low latitudes the middle eocene climatic optimum meco was a warming event that interrupted the long term eocene cooling trend while this event is well documented at high southern and mid latitudes it is poorly known from low latitudes and its timing and duration are not well constrained because of problems of hiati microfossil preservation and weak magnetic polarity in key sedimentary sections here we report the results of a study designed to improve the bio magneto and chemostratigraphy of the meco interval using high resolution records from two low latitude sections in the atlantic ocean ocean drilling program odp sites 1051 and 1260 we present the first detailed benthic foraminiferal stable isotope records of the meco from the low latitudes as well as the biostratigraphic counts of orbulinoides beckmanni and new magnetostratigraphic results our data demonstrate a 750 kyr long duration for the meco characterized by increasing 13c and decreasing 18o with minimum 18o values lasting 40 kyr at 40 1 ma coincident with a short lived negative 13c excursion thereafter 18o and 13c values recover rapidly the shift to minimum 18o values at 40 1 ma is coincident with a marked increase in the abundance of the planktonic foraminifera o beckmanni consistent with its inferred warm water preference o beckmanni is an important eocene biostratigraphic marker defining planktonic foraminiferal zone e12 with its lowest and highest occurrences lo and hos our new records reveal that the lo of o beckmanni is distinctly diachronous appearing 500 kyr earlier in the equatorial atlantic than in the subtropics 40 5 versus 41 0 ma we also show that at both sites the ho of o beckmanni at 39 5 ma is younger than the published calibrations increasing the duration of zone e12 by at least 400 kyr in accordance with the tropical origins of o beckmanni this range expansion to higher latitudes may have occurred in response to sea surface warming during the meco and subsequently disappeared with cooling of surface waters

early eocene environmental development in the northern peri tethys aktulagay kazakhstan based on benthic foraminiferal assemblages and stable isotopes o c abstract the aktulagay section in kazakhstan provides an expanded northern tethyan record of the middle ypresian calcareous nannoplankton zones np11 13 54 50 ma including the early eocene climatic optimum eeco the marl sequence features a series of sapropel beds observed throughout the peri tethys indicative of the basin wide occurrence of episodic hypoxic events in order to unravel the paleoenvironmental evolution at aktulagay during this period of global warming we investigated the benthic foraminiferal record by means of a detailed multivariate analysis of the 63 m fraction as well as through stable isotopic c o investigations on excellently preserved benthic foraminiferal specimens the alashen formation np11 to lower np12 54 to 52 5 ma in the lower part of the sequence contains a diverse assemblage of deep outer neritic 200 250 m benthic foraminifera with common pulsiphonina prima and paralabamina lunata the seafloor conditions are interpreted as initially 54 ma well ventilated and oligo to mesotrophic gradually changing to more eutrophic and oxygen limited culminating in more permanent low oxygen conditions and eutrophy in the sapropel bearing aktulagay b1 unit middle np12 52 5 52 ma the latter conclusion is corroborated by the dominance of anomalinoides acutus and bulimina aksuatica and the lower diversity also the upward migration of endobenthic species to the sediment water interface as suggested by rising 13cendobenthic values supports this interpretation a transgression which flooded lowlands might have caused this development in the aktulagay b2 unit top np12 np13 52 50 ma benthic foraminiferal assemblages dominated by epistominella minuta suggest an oligotrophic environment with transient pulses of phytodetritus and moderate ventilation the aktulagay b2 unit coincides with the peak temperature interval of the eeco as indicated by its position close to the base of np13 and rising 13cepibenthic values large river plumes episodically reaching the area in a monsoonal climatic context might explain this basin development although it is not unlikely that some of the observed patterns are related to long term climate change it can currently not be excluded that changing paleogeography and variable connections to the tethys atlantic and the arctic ocean were responsible for the long term period with dysoxia and anoxia during deposition of the sapropel beds at the peri tethyan seafloor the evolution of the basin as observed in aktulagay shows similarities to the evolution of the north sea basin as observed in denmark suggesting that these basins were connected during the early eocene

a model for orbital pacing of methane hydrate destabilization during the palaeogene the early eocene was marked by a series of abrupt warming events numerical modelling suggests that the events were the result of nonlinear interactions between orbital forcing ocean circulation and the carbon cycle a series of transient global warming events1 2 occurred during the late palaeocene and early eocene about 59 to 50 million years ago the events although variable in magnitude were apparently paced by orbital cycles2 3 4 and linked to massive perturbations of the global carbon cycle5 6 however a causal link between orbital changes in insolation and the carbon cycle has yet to be established for this time period here we present a series of coupled climate model simulations that demonstrate that orbitally induced changes in ocean circulation and intermediate water temperature can trigger the destabilization of methane hydrates we then use a simple threshold model to show that progressive global warming over millions of years in combination with the increasing tendency of the ocean to remain in a more stagnant state can explain the decreasing magnitude and increasing frequency of hyperthermal events throughout the early eocene our work shows that nonlinear interactions between climate and the carbon cycle can modulate the effect of orbital variations in this case producing transient global warming events with varying timing and magnitude

long and short term postseismic gravity changes of megathrust earthquakes from satellite gravimetry using monthly satellite gravimetry data we studied time variable gravity field after three m9 class earthquakes the 2004 sumatra andaman 2010 chile maule and 2011 tohoku oki earthquakes the observations showed that the gravity typically 1 decreases coseismically 2 continues to decrease for a few months and 3 increases over a longer period therefore postseismic gravity changes have two components with different time constants and polarities the mechanisms of short and long term postseismic gravity changes are not as clear as coseismic changes at the moment but might be explained to some extent with afterslip and the maxwell viscoelasticity respectively these two components are difficult to discriminate with surface velocity measurements because the forearc area moves trenchward at both stages they appear in different polarities in gravity making satellite gravimetry a unique tool to separate them

review and revision of cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale planktonic foraminifera are widely utilized for the biostratigraphy of cretaceous and cenozoic marine sediments and are a fundamental component of cenozoic chronostratigraphy the recent enhancements in deep sea drilling recovery multiple coring and high resolution sampling both offshore and onshore has improved the planktonic foraminiferal calibrations to magnetostratigraphy and or modified species ranges this accumulated new information has allowed many of the planktonic foraminiferal bioevents of the cenozoic to be revised and the planktonic foraminiferal calibrations to be reassessed we incorporate these developments and amendments into the existing biostratigraphic zonal scheme in this paper we present an amended low latitude tropical and subtropical cenozoic planktonic foraminiferal zonation we compile 187 revised calibrations of planktonic foraminiferal bioevents from multiple sources for the cenozoic and have incorporated these recalibrations into a revised cenozoic planktonic foraminiferal biochronology we review and synthesize these calibrations to both the geomagnetic polarity time scale gpts of the cenozoic and astronomical time scale ats of the neogene and late paleogene on the whole these recalibrations are consistent with the previous work however in some cases they have led to major adjustments to the duration of biochrons recalibrations of the early middle eocene first appearance datums of globigerinatheka kugleri hantkenina singanoae guembelitrioides nuttalli and turborotalia frontosa have resulted in large changes in the durations of biochrons e7 e8 and e9 we have introduced upper oligocene zone o7 utilizing the biostratigraphic utility of paragloborotalia pseudokugleri for the neogene period major revisions are applied to the fohsellid lineage of the middle miocene and we have modified the criteria for recognition of zones m7 m8 and m9 with additional adjustments regarding the globigerinatella lineage to zones m2 and m3 the revised and recalibrated datums provide a major advance in biochronologic resolution and a template for future progress of the cenozoic time scale

foraminiferal turnover across the eocene oligocene transition at fuente caldera southern spain no cause effect relationship between meteorite impacts and extinctions we studied planktic and small benthic foraminifera from the fuente caldera section southern spain across the eocene oligocene transition benthic foraminifera indicate lower bathyal depths for the late eocene and earliest oligocene detailed highresolution sampling and biostratigraphical data allowed us to date precisely layers with evidence for meteorite impact ni rich spinel which occur in the lower part of the planktic foraminiferal globigerapsis index biozone and in the middle part of the small benthic foraminiferal cibicidoides truncanus bb4 biozone middle priabonian late eocene major turnovers of foraminifera occur at the eocene oligocene boundary only the impact did not occur at a time of planktic or benthic foraminiferal extinction events and the late eocene meteorite impacts did thus not cause extinction of foraminifera the most plausible cause of the eocene oligocene boundary extinctions is the significant cooling which generated glaciation in antarctica and eliminated most of the warm and surface dwelling foraminifera d 2005 elsevier b v all rights reserved

multiple early eocene hyperthermals their sedimentary expression on the new zealand continental margin and in the deep sea the paleocene eocene thermal maximum petm ca 55 5 ma was a geologically brief interval characterized by massive influx of isotopically light carbon extreme changes in global climate and profound variations in earth system processes an outstanding issue is whether it was an isolated event or the most prominent example of a recurring phenomenon recent studies of condensed deep sea sections support the latter but this finding remains uncertain here we present and discuss lithologic and carbon isotope records across two lower eocene outcrops on south island new zealand the petm manifests as a marl rich horizon with a significant negative carbon isotope excursion cie above in sediment deposited between 54 and 53 ma are four horizons with similar though less pronounced expressions marl beds of all five horizons represent increased terrigenous sedimentation presumably linked to an accelerated hydrological cycle five corresponding clay rich horizons and cies are found in deep sea records although the lithologic variations represent carbonate dissolution rather than siliciclastic dilution the presence of five intervals with similar systemic responses in different environments suggests a mechanism that repeatedly injected large masses of 13 c depleted carbon during the early eocene

closure of the budget of global sea level rise over the grace era the importance and magnitudes of the required corrections for global glacial isostatic adjustment abstract the budget of global sea level rise includes contributions from several distinct factors including thermosteric effects the wasting of small ice sheets and glaciers and the loss of mass by the great polar ice sheets and by the continents due to desiccation since the former contribution may be estimated on the basis of both hydrographic survey data and more recently using argo float data the second may be estimated on the basis of mass balance measurements on existing ice fields and the latter on the basis of modern grace based time dependent gravity field measurements the inputs to the globally averaged rate of sea level rise may be directly constrained since grace also provides a measurement of the rate at which mass is being added to the oceans we are now in a position to ask whether this rate of mass addition to the oceans matches the rate at which mass is being removed from the continents as demonstrated herein the mass component of the budget of global sea level is closed within the observational errors when the mass derived contribution is added to the thermosteric contribution it is furthermore shown that the inference of the net rate of global sea level rise by the altimetric satellites topex poseidon and jason 1 is also reconcilable over the grace era it is noted those individual terms in the budget especially the contribution from small ice sheets and glaciers remains insufficiently accurate it is demonstrated that the lingering influence of the late quaternary ice age upon sea level is profound and that closure of the budget requires an accurate model of its impact

micropalaeontological evidence for the late oligocene oi 2b global glaciation event at the zarabanda section spain abstract we present an integrated micropalaeontological study using smaller and larger benthic foraminifera planktonic foraminifera and calcareous nannofossils of the late oligocene from the zarabanda section western tethys in order to reconstruct the palaeoenvironmental turnover and to precisely establish the chronology of the palaeoclimatic events planktonic foraminifera show that the zarabanda section is apparently continuous and spans the planktonic foraminiferal zones o5 upper part o6 and o7 and the calcareous nannofossil zones cp19b and cn1a lower part the quantitative analysis of smaller benthic foraminiferal assemblages enabled us to determine a middle lower bathyal depth of deposition for most part of the section the smaller benthic foraminifera show a bloom of neritic species an increase in the percentages of cool water species a decrease of the planktonic benthic ratio generic richness heterogeneity and diversity all around a 10 m thick succession of calcarenites in the lower part of the planktonic foraminifera o6 zone and the middle part of the calcareous nannofossil cp19b zone these changes coincide with the major turnover in the larger benthic foraminiferal assemblages the last occurrence of eulepidina dilatata and the first occurrence of nephrolepidina morgani these variations in the smaller and larger benthic foraminiferal assemblages may be associated with the major expansion of the antarctic ice sheet at approximately 26 7 ma which is known as the oi 2b global glaciation event

eocene bartonian benthic foraminifera and paleoenvironmental changes in the western tethys abstract the eocene was a period of intense climate variability and the response of deep sea biota is still poorly understood especially across certain understudied intervals from the middle eocene we present new benthic foraminiferal data from a bartonian marine sequence deposited in the western tethys ocean torre cardela section spain and determine the biotic and paleoenvironmental turnover the assemblages indicate a middle to lower bathyal depth of deposition and they contain allochthonous taxa e g asterigerinids that were transported from shallower settings a detrended correspondence analysis dca performed on the total assemblage differentiates the autochthonous and allochthonous taxa supporting the idea of different provenience we suggest that the latter were likely transported downslope by currents quantitative analyses of the autochthonous assemblages show a strong dominance of calcareous infaunal taxa mainly bolivinids which point to a high flux of organic matter to the seafloor bolivinoides crenulata the most common species is associated with inputs of refractory organic matter and high energy environments five intervals were differentiated based on changes in the relative abundance of taxa two intervals b and d show the highest percentages of allochthonous taxa and b crenulata we suggest that enhanced current activity not only transported allochthonous taxa but also brought in refractory organic matter to the seafloor which was consumed by opportunistic taxa during these two intervals we conclude that benthic foraminiferal assemblages at torre cardela were strongly controlled by the amount and type of organic matter reaching the seafloor which were in turn affected by sedimentary and ultimately by climatic factors

coupled greenhouse warming and deep sea acidification in the middle eocene 1 the middle eocene climatic optimum meco is an enigmatic warming event that represents an abrupt reversal in long term cooling through the eocene in order to further assess the timing and nature of this event we have assembled stable isotope and calcium carbonate concentration records from multiple deep sea drilling project and ocean drilling program sites for the time interval between 43 and 38 ma revised stratigraphy at several sites and compilation of 18o records place peak warming during the meco event at 40 0 ma chron c18n 2n the identification of the 18o excursion at sites in different geographic regions indicates that the climatic effects of this event were globally extensive the total duration of the meco event is estimated at 500 ka with peak warming lasting 100 ka assuming minimal glaciation in the late middle eocene 4 6 c total warming of both surface and deep waters is estimated during the meco at the study sites the interval of peak warming at 40 0 ma also coincided with a worldwide decline in carbonate accumulation at sites below 3000 m depth reflecting a temporary shoaling of the calcite compensation depth the synchroneity of deep water acidification and globally extensive warming makes a persuasive argument that the meco event was linked to a transient increase in atmospheric pco2 the results of this study confirm previous reports of significant climatic instability during the middle eocene furthermore the direct link between warming and changes in the carbonate chemistry of the deep ocean provides strong evidence that changes in greenhouse gas concentrations exerted a primary control on short term climate variability during this critical period of eocene climate evolution

the middle eocene climatic optimum meco a multiproxy record of paleoceanographic changes in the southeast atlantic odp site 1263 walvis ridge the middle eocene climatic optimum meco 40 ma was a transient period of global warming that interrupted the secular cenozoic cooling trend we investigated the paleoceanographic paleoenvironmental and paleoecological repercussions of the meco in the southeast atlantic subtropical gyre ocean drilling program site 1263 tex86 and 18o records support an 4 c increase in surface and deepwater temperatures during the meco there is no long term negative carbon isotope excursion cie associated with the early warming consistent with other sites and there is no short term negative cie 50 kyr during the peak of the meco in contrast to what has been observed at some sites this lack of a cie during the peak of the meco at site 1263 could be due to poor sediment recovery or geographic heterogeneity of the 13c signal benthic and planktic foraminiferal mass accumulation rates markedly declined during meco indicating a reduction of planktic foraminiferal production and export productivity vertical 13c gradients do not indicate major changes in water column stratification and there is no biomarker or micropaleontological evidence that hypoxia developed we suggest that temperature dependency of metabolic rates could explain the observed decrease in foraminiferal productivity during warming the kinetics of biochemical reactions increase with temperature more so for heterotrophs than for autotrophs steady warming during meco may have enhanced heterotroph i e foraminiferal metabolic rates so that they required more nutrients these additional nutrients were not available because of the oligotrophic conditions in the region and the lesser response of primary producers to warming the combination of warming and heterotroph starvation altered pelagic food webs increased water column recycling of organic carbon and decreased the amount of organic carbon available to the benthos

a middle eocene carbon cycle conundrum a 500 000 year long period of warmth in the middle eocene was marked by high atmospheric carbon dioxide concentrations and prolonged dissolution of carbonate in the deep oceans numerical simulations attempting to capture these features identify gaps in our understanding of the causes of this and similar perturbations

episodes of intensified biological productivity in the subtropical atlantic ocean during the termination of the middle eocene climatic optimum meco the middle eocene climatic optimum meco is an 500 kyr interval of pronounced global warming from which the climate system recovered in 50 kyr the deep sea sedimentary record can provide valuable insight on the marine ecosystem response to this protracted global warming event and consequently on the ecological changes during this time here we present new benthic foraminiferal assemblage data from ocean drilling program site 1051 in the subtropical north atlantic spanning the meco and post meco interval 41 1 to 39 5 ma we find little change in the species composition of benthic foraminiferal assemblages during the studied interval suggesting that the rate of environmental change was gradual enough that these organisms were able to adapt however we identify two transient intervals associated with peak warming higher productivity interval hpi 1 40 07 39 96 ma and shortly after the meco hpi 2 39 68 39 55 ma where benthic foraminiferal accumulation rates increase by an order of magnitude these hpis at site 1051 appear to coincide with intervals of strengthened productivity in the tethys southern ocean and south atlantic and we suggest that an intensified hydrological cycle during the climatic warmth of the meco was responsible for eutrophication of marine shelf and slope environments

an early eocene carbon cycle perturbation at 52 5 ma in the southern alps chronology and biotic response an early eocene carbon cycle perturbation at 52 5 ma from the southern alps chronology and biotic response

benthic foraminifera as proxies of organic matter flux and bottom water oxygenation a case history from the northern arabian sea abstract benthic foraminifera have been quantified in two sediment cores from a topographic high murray ridge in the northern arabian sea one core is from a station within the present day oxygen minimum zone omz the other from a station below the omz changes in the intensity of the omz linked to monsoonal climate variability had a strong impact on benthic foraminiferal composition and accumulation rates at the shallower omz station 920 m an intensification of the omz resulted in lower diversities and high dominances of low oxygen tolerant species the deeper station 1470 m was far less affected though at least once during the last 225 000 years the benthic faunal composition and accumulation rates show evidence for a deepening of the base of the omz to a level close to or even below 1470 m we suggest that percentages of miliolids can be used for rapid reconstruction of periods of increased ventilation in the northern arabian sea and are a promising proxy for tracing changes in bottom and pore water oxygenation in general omz conditions are characterised by high abundances of deep infaunal species and increased burial efficiency of organic matter the proportion of deep infaunal species appears to be a measure for the anoxic burial efficiency of organic matter and not a direct measure for the arriving flux at the seabed results furthermore show that benthic foraminiferal accumulation rates cannot be used as a proxy for surface water productivity under the prevalence of severe dysoxia