distribution patterns of live planktic foraminifers as related to regional hydrography and productive systems of the mediterranean sea abstract distribution patterns of live planktic foraminifers are examined at two times of the year late summer and late winter through horizontal plankton towing along a nw se transect across the west and east mediterranean basins and in the alboran sea french oceanographic cruises vicomed i ii and iii respectively foraminiferal production is significantly different in the two sampling periods and across the west and east mediterranean foraminiferal density is higher in winter than summer e g in the western basin 3700 specimens 1000 m3 in winter against 200 600 specimens 1000 m3 in summer the production averaged for the two sampling sets is higher in the western basin than in the eastern one however in late summer peaks of maximal production are observed in the central mediterranean strait of sicily and ionian basin 1000 to 2000 specimens 1000 m3 where the assemblages are dominated by globigerinoides ruber rosea and g ruber alba in the mediterranean sea frontal regions and semipermanent eddies which are essentially controlled by regional hydrography represent a significant portion of the regional production they also elicit a higher diversity of species their influence is observed in summer as well as in winter at the end of summer the rather shallow mixed layer hosts spinose symbiont bearing species such as g ruber alba g ruber rosea o universa and g trilobus at that season in the western basin the nutrient content of the mixed layer is generally low and the surface layer is rapidly nutrient depleted summer foraminiferal production remains low at the surface with respect to the winter production in the eastern basin late summer and autumn correspond to the biological spring summer foraminiferal production in surface waters is higher than in winter but standing crops are lower than in the western basin for the same species at the same period in summer however frontal structures and eddies are generally better developed than in winter in some particular cases frontal boundaries in the western basin eddies south of cyprus nutrients from intermediate layers can be upwelled through isopycnal or diapycnal mixing to the photic zone and allow for secondary blooms in the western basin these blooms favour the development of grazers at depth globorotalia truncatulinoides g inflata south of cyprus in the eastern basin oligotrophic conditions promote the development of heterotrophic organisms and predatory foraminifers have higher standing stocks g ruber alba g ruber rosea in winter the break down of the thermocline combined with deep turbulent mixing in the northwestern basin and the deepening of the mixed layer in the alboran sea and along the north african coast result in increased phytoplankton biomass and favour reproduction and proliferation of species such as g truncatulinoides or g inflata our observations indicate that the geographic and depth distribution of live foraminiferal species cannot be entirely explained by the general temperature and salinity differences among the different mediterranean basins but that they are strongly related to regional hydrographic patterns hydrography controls the seasonality and depth of the turbulent mixing which differ between the western and the eastern basins the depth of the mixed layer and its seasonal stratification and the strength of the pycnocline nutrient supply and primary production are mostly regulated by these dynamics one may therefore expect that the species assemblages on the sea floor and in deep sea cores will also correlate to the various hydrographic parameters of the overlying water masses

solar forcing of nile discharge and sapropel s1 formation in the early to middle holocene eastern mediterranean we present high resolution records for oxygen isotopes of the planktic foraminifer globigerinoides ruber 18oruber and bulk sediment inorganic geochemistry for holocene age sediments from the southeast mediterranean our 18oruber record appears to be dominated by nile discharge rather than basin scale salinity temperature changes nile discharge was enhanced in the early to middle holocene relative to today the timing of the long term maximum in nile discharge during the early holocene corresponds to the timing of maximum intensity of the indian ocean influenced southwest indian summer monsoon sim this coincidence suggests a major influence of an indian ocean moisture source on nile discharge in the early to middle holocene while presently the atlantic ocean is the main moisture source nile discharge was highly variable on multicentennial time scale during the early to middle holocene being strongly influenced by variable solar activity this solar driven variability is also recorded in contemporaneous sim records however not observed in an atlantic ocean derived west african summer monsoon record from the holocene this supports the hypothesis that the indian ocean moisture source predominantly controlled nile discharge at that time solar driven variability in nile discharge also influenced paleoenvironmental conditions in the eastern mediterranean bulk sediment ba al and v al used as indicators for export productivity and redox conditions respectively varied both in response to solar forcing on multicentennial time scales we suggest that changes in nile discharge on these time scales have been concordant with nutrient inputs to and shallow ventilation of the eastern mediterranean

fluxes of planktic foraminifera in response to monsoonal upwelling on the somalia basin margin abstract sediment trap samples collected off somalia bi weekly from early june 1992 through mid february 1993 show large seasonal variations in the shell flux and species composition of planktic foraminifera these variations mirror the monsoon driven circulation which resulted in massive upwelling and offshore eddy transport in summer during the sw monsoon june september and accounted for nearly 90 of the estimated annual shell flux of planktic foraminifera g bulloides dominated the sw monsoon along with g glutinata t quinqueloba n dutertrei and t iota in a fauna rich species but with a low diversity and equitability during the autumn intermonsoon november december the ocean became stratified and the nutrient exhausted whereas during the ne monsoon january march a warm surface mixed layer developed with the nutrients entrained by deep wind mixing it was dominated by g ruber in association with g tenella g aequilateralis g trilobus g sacculifer and g menardii in a fauna poorer in species but with a higher diversity and equitability consequently the ratio in the abundance of g bulloides and g ruber follows the monsoonal cycle closely as both species persist throughout the year only the rare g theyeri seems to be restricted to the sw monsoon in october at the end of the sw monsoon the trap at 265 m above the bottom intercepted massive amounts of fine grained carbonate m resuspended from the shelf and upper slope it contained extreme fluxes of bioclastic fragments benthic foraminifera and benthic ostracods as well as enhanced fluxes of small sized planktic foraminifera m notably g rubescens integrated over the year the species composition intercepted by the trap shows a very good match with the shell fauna in a core top sediment from the same site apparently the year estimated monsoonal record of planktic foraminifera which is strongly dominated by the sw monsoon production survives burial intact consequently the species composition of planktic foraminifera and measures such as the bulloides ruber ratio can be applied as a proxy for past changes in the intensity of the sw monsoon off somalia compared to the modern condition

long and short term carbon fluctuations in the eastern mediterranean during the late holocene a high resolution record of carbon isotope changes during the late holocene was obtained in core ga 112 from the easternmost mediterranean over the past 3600 yr a gradual 13 c depletion trend shown by both planktonic and benthic foraminifera corresponds to a global rise in atmospheric co 2 the global and local trends suggest that aridification and biomass destruction in the nile basin played a major role in the global co 2 rise in the late holocene superimposed on the general 13 c trend are four mirror image cycles in 13 c of planktonic and benthic foraminifera higher planktonic 13 c values reflect periods of high productivity off the coast of israel simultaneously decrease in the benthic 13 c values occurred because of degradation of higher organic matter fluxes to the sediment therefore large differences between the two records indicate periods of high productivity the eastern mediterranean productivity fluctuations respond to a periodical replenishment of nutrients to the mixed layer via nile runoff historical data of the nile flood fluctuations for the past 1400 yr show a remarkable coincidence between high and low nile floods and high and low eastern mediterranean productivity levels which are correlated with the periodic monsoonal activity over the nile headwaters

observations and simulation of a bottom ekman layer on a continental shelf a numerical model was used to simulate the bottom ekman layer of a continental shelf region the basis for the model was the mellor and yamada level 2 turbulence closure scheme conservation equations for momentum turbulent kinetic energy and turbulent length scale were utilized in the model the model was used to simulate data taken from a cyclesonde mooring on the peruvian continental shelf in may 1976 as part of the joint ii coastal upwelling ecosystems analysis program the cyclesonde provided mean horizontal velocity temperature salinity and pressure data an intense poleward undercurrent drove the bottom flow regime the most striking feature of the data was the clockwise ekman veering of velocity vectors as the bottom was approached a 48 hour period was chosen for the model simulations the vertical profile of speed 48 hours mean simulated by the model fell within the error bars of the data the corresponding ekman spiral display of the model results also showed good agreement with the observati ons

planktic foraminiferal sedimentation and the marine calcite budget 1 the vertical flux and sedimentation rate of planktic foraminiferal tests are quantified and a global planktic foraminiferal cac0 3 budget is presented test and calcite flux rates are calculated according to the distribution of species obtained from multinet and sediment trap samples modern planktic foraminiferal population dynamics are discussed as a prerequisite for the quantification of the calcite budget highlighting the importance of ecological autecological e g reproduction and biogeochemical conditions that determine the presence or absence of species to complete the open marine particulate caco 3 inventory the contribution of coccolithophores pteropods and calcareous dinophytes is discussed based on the studied regions the global planktic foraminiferal calcite flux rate at 100 m depth amounts to 1 3 3 2 gt yr 1 equivalent to 23 56 of the total open marine caco 3 flux the preservation of tests varies on a regional and temporal scale and is affected by local hydrography and dissolution during most of the year off peak periods many tests dissolve above 700 m water depth while settling through the water column with on average only 1 3 of the initially exported caco 3 reaching the deep seafloor pulsed flux events mass dumps of fast settling particles yield a major contribution of tests to the formation of deep sea sediments on average 25 of the initially produced planktic foraminiferal test cac0 3 settles on the seafloor the total planktic foraminiferal contribution of caco 3 to global surface sediments amounts to 0 36 0 88 gt yr 1 32 80 of the total deep marine calcite budget

seasonal variability of the mixed layer depth in the mediterranean sea as derived from in situ profiles a new 0 5 resolution mediterranean climatology of the mixed layer depth based on individual profiles of temperature and salinity has been constructed the criterion selected is a threshold value of temperature from a near surface value at 10 m depth mainly derived by a method applied on the global de boyer montegut et al 2004 dbm04 with respect to dbm04 the main differences reside in the absence of spatial interpolation of the final fields and in the improved spatial resolution these changes to the method are necessary to reproduce the mediterranean mixed layer s behavior in the derived climatological maps the most relevant features of the basin surface circulation are reproduced as well as the areas prone of the deep water formation are clearly identified finally the role of density in the definition of the mixed layer s differing behaviors between the oriental and the occidental regions of the basin is presented

the characterisation of saharan dusts and nile particulate matter in surface sediments from the levantine basin using sr isotopes abstract the provenance of sediments within the levantine basin of the eastern mediterranean was studied using 87 sr 86 sr isotopic ratios together with major elements measurements were made on the detrital fraction of surface sediments and the two most important sources of detrital matter to the region saharan dust was characterised by an 87 sr 86 sr isotopic ratio in the range 0 7160 0 7192 there was a small systematic decrease in 87 sr 86 sr from west to east which is interpreted as due to a change in the balance of aeolian source material the nile particulate matter had a 87 sr 86 sr isotopic ratio in the range 0 7057 0 7071 87 sr 86 sr isotopic signatures together with sr concentration were used to calculate the contributions made by saharan dust and nile particulate matter to the surface sediments of the levantine basin it was shown that nile derived sediment was dispersed widely across the levantine basin enabling the area affected by retention of sediment behind the aswan dam to be determined

globorotalia truncatulinoides in central western mediterranean sea during the little ice age abstract globorotalia truncatulinoides oscillations have been recorded from different marine sediment cores collected in the central and western mediterranean sea the abundances of this species over the last 500 yrs demonstrates its potential value as bio indicator of particular oceanographic condition during the maunder minimum mm event of the little ice age lia the comparison between the g truncatulinoides abundance patterns of the balearic basin central and south tyrrhenian sea and central and eastern sicily channel allows to highlight a similar response of this species during the mm event in the central western mediterranean sea the ecological meanings of this species and its peculiar high abundance percentages in the total assemblages suggest the development of enhanced vertical mixing conditions during mm winter season with a strong advection of nutrients from the nutrient rich deeper layers and enhances the productivity levels in the mixed layer the intensified vertical mixing could be linked to persistence of an atmospheric blocking event recorded by several authors during the mm

seasonal changes in species composition numbers mass size and isotopic composition of planktonic foraminifera settling into the deep sargasso sea abstract planktonic foraminifera recovered from six successive sediment trap samples collected over fourteen months at a depth of 3200 m near bermuda show varied responses to seasonal changes in the near surface hydrography these include changes in species composition and within species changes in number of individuals collected per unit time average size and weight of individuals and in oxygen and carbon isotopic composition a total of seventeen species were identified and eleven were sufficiently abundant for isotopic analysis in at least some of the samples the accumulations on the sea floor of some of these species can be expected to contain a strong seasonal component in their oxygen isotopic composition which may be utilized in paleoclimatic and paleo oceanographic reconstructions best suited to this purpose are those species which form their tests in isotopic equilibrium with surface water and whose abundance is confined to a portion of the year only the best examples are pulleniatina o bliguiloculata globigerinoides conglobatus and neogloboquadrina dutertrei globigerinoides ruber is a good estimator of the average surface water temperature because it occurs in rather even abundance throughout the year hastigerina pelagica though very abundant in surface water is practically eliminated even before arrival on the sea floor by partial resorption and structural weakening of the tests during gametogenesis orbulina universa globorotalia truncaltulinoides and globorotalia hirsuta show morphological and istopic evidence for contibnued calcification in deeper water after initial test formation near ther surface globigerina bulloides represents the most striking example of oxygen isotopic disequilibrium with sea water

global climate instability reflected by eastern mediterranean marine records during the late holocene abstract extremely high sediment accumulation rates in the southeastern se mediterranean off israel make this region ideal for high resolution paleoceanographic reconstructions two cores were examined and foraminiferal oxygen and carbon isotope composition as well as physical and geochemical properties of the sediments were used to reconstruct the climatic and environmental changes of the se mediterranean basin during the late holocene 3 6 ka the 18o values of globigerinoides ruber suggest that the freshwater balance changed several times during this time interval humid phases took place between 3 5 3 0 ka bp and 1 7 1 0 ka bp the later was accompanied by enhanced preservation of terrestrial organic matter within the sediment ors event relatively more arid conditions prevailed in this area between 3 0 and 1 7 ka bp during the last millennia at ca 0 8 and 0 27 ka two climatic events occurred which are probably correlative to both the medieval warm period and the cooling global event known as the little ice age respectively a long term slight increase in planktonic foraminiferal 18o values occurs together with a gradual decrease in the 13c values of both g ruber and the benthic foraminifera uvigerina mediterranea this trend is associated with an increase in sedimentation rates ti al ratio magnetic susceptibility and color index of the sediments we suggest that this trend shown by various independent proxies seems to be related to the aridification process that started ca 7 0 ka in the mid low latitude desert belt and the se mediterranean region and continuous until the present the long term 13c decrease shown by surface and bottom water foraminifera reflects a gradual change in the 13c of the dissolved co2 of the entire se mediterranean water column this follows the global co2 rise in the late holocene as a result of the terrestrial biomass destruction during the aridification process moreover the gradual reduction of the vegetation cover in east africa led to an increased erratic flood related sediment flux via the nile river up to the present this is reflected by the general change in the local sediment composition at 3 6 ka the saharan eolian input reached 65 whereas at about 0 3 ka 70 of the se mediterranean sediment was composed of nile particulate matter

mass accumulation rates in asia during the cenozoic summary this work establishes estimates of mass accumulation rates in 18 mostly offshore sedimentary basins in asia since the beginning of the cenozoic 66 ma the estimates were derived from isopach maps cross sections and drill holes or stratigraphic columns assuming regional similarity of the strata average solid phase volumes and accumulation rates were calculated for nine epochs approximately corresponding to geological periods palaeocene 66 58 ma eocene 58 37 ma oligocene 37 30 and 30 24 ma miocene 24 17 17 11 and 11 5 ma pliocene 5 2 ma and quaternary 2 0 ma these rates shed new light on the geological history of asia since the onset of the collision of india with asia 50 ma the overall average accumulation rates curve for asian sedimentary basins since the beginning of the tertiary shows an exponential form with slow accumulation rates less than 0 5 106 km3 myr 1 until the beginning of the oligocene more than 15 myr after the onset of the collision from the oligocene onwards rates increase quickly in an exponential manner reaching their maximum values in the quaternary more than 1 5 106 km3 myr 1 from these observations we suggest that extrusion and crustal shortening are complementary processes that have been successively dominant throughout the india eurasia collision history at smaller scales one may distinguish between independent histories at the subcontinental and basin scales this permits a comparison of the relative importance of tectonic and climatic erosion processes affecting the different mountain belts of asia during the cenozoic

thirteen thousand years of southeastern mediterranean climate variability inferred from an integrative planktic foraminiferal based approach over the past 13 ka the hydrology for the southeastern mediterranean was mainly regulated by nile river runoff which in turn was controlled by climate forcing being affected by orbital forcing and the position of the intertropical convergence zone itcz planktic foraminiferal data assemblages stable isotopes and size properties indicate three major periods 1 from 13 0 to 11 5 ka the upper water column was well mixed cold and productive 2 from 11 5 to 6 4 ka hydrology and foraminifers were affected by intensified monsoonal circulation the enhanced size of globigerinoides ruber is interpreted as a response to environmental stress caused by low saline waters 3 after 6 4 ka the southward retreat of the itcz caused a decrease in freshwater discharge and hence a return to ecological equilibrium a drop in foraminifer diversity from 2 9 to 1 1 ka was related to more arid conditions and limited supply of nutrients from the nile river we suggest a link to a negative north atlantic oscillation nao marking the roman humid period in the western mediterranean and in anti phase with the southeastern mediterranean aridity because nile river runoff exerted major control on surface hydrology a connection to indian and pacific climate systems partially controlling precipitation over the nile catchment area is hypothesized from 1 1 to 0 54 ka high foraminifer diversity indicates humid conditions synchronous to the medieval climate anomaly under a positive nao state over the past 0 54 ka encompassing the little ice age another arid period is indicated by a drop in foraminifer diversity

variability of the large scale general circulation of the mediterranean sea from observations and modelling a review abstract in this paper we present an overview of the most recent findings about the mediterranean sea present day circulation structure both historical observations and numerical model simulations are presented outlining the differences and agreement the model simulations are presented for both an eddy resolving and a coarse resolution numerical model and the results are intercompared the importance of the mesoscales in modifying the large scale flow field is elucidated the critical point is the discovery of the large amplitude interannual variability of the circulation and water mass structure associated with the anomalies of atmospheric forcing over the basin the seasonal variability can be strictly related to changes in heat and momentum fluxes while the interannual variability has a component which is related to the mesoscale field the latter is very intense in the algerian current region and levantine basin but different in structure in the two regions results are shown which confirm the importance of wind driving in establishing the kinetic energy of the flow field by comparing the current transport at the strait of corsica with observations in conclusion the essential characteristics of the present day circulation are associated with the atmospheric forcing and the basin topographic structure results from palaeoceanographic simulations for the last 20 000 years show that changing the atmospheric forcing can cause large changes in the circulation structure which may have affected sapropel formation

sediment trap and deep sea coretop sediments as tracers of recent changes in planktonic foraminifera assemblages in the southeastern ultra oligotrophic levantine basin abstract sediment trap and core top sediments were used to study the seasonal and longer term variability in the distribution and assemblage composition of planktonic foraminifera pf in the ultra oligotrophic eastern mediterranean levantine basin lb a continuous time series of particulate flux sampled every 11 12 days were retrieved from a sediment trap deployed at 1300 m between may 2017 and may 2018 the core top sediments were collected close to the sediment trap mooring site at 1500 m water depth the average annual planktonic foraminiferal pf flux was 93 shells m 2 d 1 the lowest value yet recorded among traps located in tropical subtropical oligotrophic regions a bimodal increase in pf flux is observed with highest numbers of 452 shells m 2 d 1 occurring in winter february responding directly to maxima in particulate mass flux a lower flux occurs in late summer from mid august to mid september with up to 197 shells m 2 d 1 ten species were found in the trap the majority were symbiont bearing spinose species that contribute 96 of the total flux globigerinoides ruber white predominate the assemblage composition during the winter peak together with globoturborotalita rubsecens and globigerinella calida during the subordinate summer peak the dominating species were g ruber white orbulina universa and globigerinoides ruber pink the relative abundance of g bulloides and g ruber pink is much lower in the sediment trap samples compared to their abundance in nearby coretop sediments this trend seems to indicate a recent drop in their numbers at the same time g rubescens and globoturborotalita tenella occur in higher numbers in the sediment trap compared with the coretop samples these opposite trends may reflect the current adjustment of certain pf species to the ongoing sea surface warming and decrease in food availability in the lb

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

microplankton response to environmental conditions in the alboran sea western mediterranean one year sediment trap record abstract the present work analyses the seasonal evolution of planktonic assemblages and particle fluxes through the water column in the eastern alboran sea western mediterranean at 35o55 47 n 01o30 77 w a sediment trap was deployed below the influence of the almeria oran front aof a semi permanent geostrophic front during july 1997 to june 1998 overall the temporal variability of coccolithophore planktonic foraminifer diatom benthic and wind carried biogenic particle fluxes is linked to the seasonal evolution of sea surface hydrological structures maximum planktonic fluxes were found during high productivity periods and wind induced upwelling following a trimodal pattern with maximum fluxes in july 1997 november december 1997 and april may 1998 these periods were characterized by vertical mixing and the full development of anticyclonic gyres in the alboran sea the annual flux of coccolithophores was dominated by the small gephyrocapsa group and emiliania huxleyi whereas turborotalita quinqueloba and globigerina bulloides dominated the foraminiferal fluxes and chaetoceros resting spores rs were predominant in the diatom assemblage benthic specimens were also collected with the sediment trap suggesting a variable influence of bottom water activity wind driven particles phytoliths and fresh water diatoms were collected along the year but their fluxes followed the local wind regime the high sea surface temperature sst during fall due to weaker than usual westerly winds and the pressure anomaly prevailing in the alboran sea during early winter were reflected in the planktonic assemblages by the proliferation of warm lower photic layer inhabitants and or oligotrophic taxa of coccolithophores florisphaera profunda planktonic foraminifers globigerinoides ruber and globorotalia inflata and diatoms leptocylindrus danicus these unusual climatic conditions in the eastern alboran sea must have been caused by the 1997 1998 enso event

planktonic foraminifers as tracers of ocean currents in the eastern south atlantic the standing stock of planktonic foraminifers collected at 16 stations by multinet plankton tow has been examined in five discrete depth intervals 0 25 m 25 50 m 50 100 m 100 150 m and 150 300 m the assemblages document the status of populations in the surface and subsurface waters of the southeast atlantic during february march 1988 standing crops document hydrographic conditions in the coastal and geostrophic branch of the benguela current the angola current the tropical cyclonic gyre and the south equatorial current standing stocks are highest when primary production is intermediate very high primary production reduces foraminiferal crops significantly eleven species occur abundantly average 10 of the total standing stock a few species g glutinata g quinqueloba g clarkei are abundant at each station whereas the occurrence of other species g ruber g sacculifer g scitula g menardii g crassaformis n incompta n dutertrei is spatially restricted g ruber g rubescens and g glutinata are abundant in high salinity surface water also g ruber is abundant within the equatorial undercurrent water when this water is brought to the surface high concentrations of n incompta and g bulloides are observed in the angola benguela front when nutrient concentration is moderately elevated in surface and subsurface water upper part of the thermocline g crassaformis becomes abundant in the subsurface water of the angola benguela front this species is restricted to lower oxygenated subsurface water and traces incursions of water transported by the angola current g menardii is considered as an indicator for the equatorial undercurrent below the mixed layer whereas g scitula most probably points to an admixture of water transported by the northward flowing benguela current high abundances of g quinqueloba g clarkei in the surface and subsurface waters reflect favorable nutrient conditions like those present in the geostrophic benguela current and in the equatorial divergence zone g falconensis n dutertrei and g siphonifera appear to trace the southern equatorial current

stable isotopic composition of pedogenic carbonates of the early cretaceous shimonoseki subgroup western honshu japan abstract abundant pedogenic carbonate nodules are present in the shimonoseki subgroup in the kanmon basin of kyushu and honshu japan the oxygen isotope compositions of these pedogenic carbonates range from 20 1 to 22 8 pdb which is 7 lower than those of the septarian crystallaria in the carbonate nodules the meteoric water composition estimated from the oxygen isotope composition of the soil water in equilibrium with the carbonates is much depleted compared with the estimate from other sources this suggests that the oxygen isotope compositions of the shimonoseki pedogenic carbonates were modified during diagenesis the carbon isotopic compositions of the shimonoseki carbonates range from 5 4 to 7 0 pdb with an average of 6 7 pdb suggesting carbonate formation in soils dominated by c 3 type of vegetation an analysis of these values using cerling s model cerling t e wright v p vanstone s d 1992 further comments on using carbon isotopes in paleosols to estimate the co 2 content of the palaeo atmosphere j geol soc london 148 1991 945 947 149 673 676 indicates that the partial pressure of co 2 in the early cretaceous shimonoseki atmosphere was about 1700 3200 ppmv

palaeoprecipitation record using o isotope studies of the himalayan foreland basin sediments nw india abstract the himalayan foreland basin sediments were deposited during a crucial time period in the himalayan orogeny this period in the tertiary has become major focus of research because of the large scale uplift of the himalayan range which has greatly modified the climate of the asian continent the present south asian monsoonal climate is believed to be a consequence of himalayan uplift during this period also the himalayan orogeny comprises a major regional tectonic event of the earth hence the study of these himalayan foreland basin sediments are not only significant in revealing the palaeoclimatic history of the asian continent but also paves a way for understanding of the effects of himalayan orogeny on global climate here we report a palaeoprecipitation history of the ramnagar sub basin since miocene times and its regional correlation to other sub basins of the himalayan mountain belt an attempt has been made to use oxygen isotope ratios of pedogenic carbonates in siwalik palaeosols as proxy palaeo recorders to deduce the palaeoclimatic history of the jammu region in the ramnagar sub basin for the first time a total of 141 pedogenic carbonates have been analyzed from three siwalik sections covering a lateral stretch of approximately 40 50km along strike the 18 o values vary from 12 31 to 5 89 and when plotted against age indicate that 18 o values on average become 2 enriched from the oldest to the youngest analyzed sediments except for largely depleted 18 o values around 10 ma 5 ma and 1 8 ma this 2 increase in calculated 18 o values could have been possible by an 3 c increase in mean annual air temperature conversely the largely negative 18 o values indicate periods of intense rainfall or stronger monsoonal conditions an increase of 2 6 in 18 o values has been found from the 10 ma rainfall event to that at 1 8 ma which indicates a reduction of 173 mm in rainfall intensity and amount hence precipitation reconstructions indicate a progressive increase in aridity from 12 ma to recent excluding a short term increases in rainfall or monsoon intensity at around 10 ma 5 ma and 1 8 ma this pattern of palaeoprecipitation change is similar to the changes documented in other sub basins of the himalayan mountain range further monsoon intensification at around 10 ma 5 ma and 1 8 ma is also observable in various other proxy records thereby suggesting the role of significant regional tectonism in the evolution and intensification of the present south asian monsoon climate our results indicate that from the mid miocene to recent except for the periods of largely depleted 18 o values the average 18 o value increased by 2 the general increase in average 18 o values from lower to upper siwalik sediments can be explained by changes in both continentality and latitude of the moisture source it seems likely that this long term increase in 18 o values was due to the uplift of the himalayas and the tibetan plateau in the north which acted as a barrier to the passage of airmasses from central asia in the north thereupon with time restricting the source of airmasses to the south from the indian ocean

regional paleoprecipitation records from the late eocene and oligocene of north america abstract the marine 18o record indicates precipitous cooling or significant expansion of antarctic ice volume across the eocene oligocene epoch boundary at 33 7 ma this climatic step is also found in estimates of decreased paleoprecipitation from paleosols in oregon montana and nebraska but is only a part of a long term decline across the eocene oligocene transition rather than a sudden shift this suggests that climate was driven by a gradual process rather than a single perturbation paleoprecipitation levels stabilized during the oligocene coincident with a stabilization in 18o values possibly indicating a new climatic steady state

regional and interannual productivity of biogenic components and planktonic foraminiferal fluxes in the northwestern pacific basin abstract time series sediment trap experiments at subtropical wct 1 and subarctic wct 2 stations in the northwestern pacific indicate seasonal latitudinal and depth variations in total particulate biogenic and foraminiferal fluxes at the subtropical station the average total mass flux was 19 4 mg m 2 day 1 in the shallow trap 1060 m and 21 5 26 1 mg m 2 day 1 in the deep trap 3930 m during the sampling period at subarctic station these values were 91 5 176 9 mg m 2 day 1 in the shallow and 68 6 112 3 mg m 2 day 1 in the deep trap we recognized 12 and 15 planktonic foraminiferal species at station wct 1 and station wct 2 respectively the planktonic foraminiferal flux and species turnover are related to seasonal and interannual changes in source water and water column conditions at both stations at station wct 1 the highest flux was recorded during the summer with a peak in mid to late june associated with similar flux patterns of the dominant species globigerinoides ruber and globigerinita glutinata the total flux of foraminiferal tests at the shallow and deep traps is similar in numbers and magnitude at station wct 2 the peaks of total flux of foraminiferal tests at the two trap depths differ in number and their magnitude in the deep trap is almost half of that in the shallow trap a distinctive seasonal pattern occurred in the shallow and the deep trap with a peak in total foraminiferal flux in mid june to mid july globigerina quinqueloba neogloboquadrina pachyderma and neogloboquadrina dutertrei dominate the planktonic population throughout the year subtropical station wct 1 was characterized by low total foraminiferal fluxes and low total mass flux which is dominated by calcium carbonate and depleted in opal whereas high foraminiferal fluxes and a high total mass flux dominated by high biogenic opal and less calcium carbonate and organic matter characterize subarctic station wct 2 the foraminiferal carbonate that reaches the seafloor accounts for an average 20 27 and 22 23 of the total calcium carbonate at station wct 1 and station wct 2 respectively the primary reason for the difference in flux at both stations thus lies in the different contributions of siliceous and calcareous planktonic assemblages the seasonal variation in biogenic particulate flux at both stations implies that temporal changes in biological productivity are governed by large scale seasonal climatic variability and local hydrography