r selected benthic foraminifera with associated bacterial colonies in upper pleistocene sediments of the ross sea antarctica implications for calcium carbonate preservation investigations on foraminifera from upper pleistocene holocene sediments cored in the continental slope of the western ross sea 2383 m water depth revealed that the record of calcareous assemblages was restricted to a limited time interval approximately 6 kyr and characterized by a dominance of phytodetritus exploiting taxa such as alabaminella weddellensis and epistominella exigua rod shaped calcified fossil bacteria infest the partially dissolved calcareous foraminiferal surfaces either as clusters or as isolated cells suggesting that significant changes from underto oversaturated conditions with respect to calcium carbonate in the chemistry of the seawater developed before the final burial of the foraminiferal tests we postulate that bacterial activity on a microenvironmental scale interface and pore water in the sea floor could influence pore water conditions in such a way as to preserve carbonate in deep marine regions where environmental conditions usually prevent the establishment of carbonate secreting communities 1999 elsevier science b v all rights reserved

continuous sampling of hydrothermal fluids from loihi seamount after the 1996 event for at least 9 years prior to july 1996 hydrothermal fluids flowed from pele s vents on loihi seamount hawaii in july august 1996 a tectonic volcanic event occurred that destroyed pele s vents creating a pit crater pele s pit and several sites with hydrothermal venting in october 1996 we deployed two new continuous water samplers osmosamplers at two of these hydrothermal sites and collected fluids using traditional sampling techniques to monitor the evolution of crustal and hydrothermal conditions after the event the samplers were recovered in september 1997 and additional discrete vent fluid samples were collected the osmosampler located along the south rift at naha vents captured a change in composition from a low chlorinity high k fluid relative to bottom seawater to a high chlorinity low k fluid these changes are consistent with the fluid cooling during ascent and being derived from several different sources which include high 330 c and low 330 c into which magmatic volatiles were added during the deployment thermal and fluid fluxes decreased at naha the transport of heat and chemicals was decoupled the chemical and thermal evolution of hydrothermal fluids after the event on loihi is consistent with previous models based on events that have occurred along mid ocean ridges the event at loihi clearly had an effect on the local hydrography however the integrated effect of chemical fluxes to global budgets from similar events is uncertain chemical fluxes from similar events may have a global impact if ratios of chemical e g co2 fe mn mg sulfate and k to thermal anomalies greatly exceed or are in the opposite direction to fluxes from mid ocean ridge hydrothermal systems

a decade of exploring a submarine intraplate volcano hydrothermal manganese and iron at lō ihi volcano hawai i 1 decadal time series observations of hydrothermal fluid emissions from l ihi volcano were initiated in 1992 using a combination of submersible and shipboard sampling strategies magmatic tectonic processes associated with a spectacular seismic event in july august 1996 led to the collapse of pele s vents 31 c near the volcano summit into a new pit crater pele s pit inundated by high temperature tmax 198 c focused and lower temperature 30 to 200 fold 1 5 months postcollapse and during the following year decreased a further twofold to threefold at pele s pit and 30 fold at east pit while a steady concentration of 400 nmol l tdfe prevailed throughout the remaining years of this study at pele s pit a gradual and threefold decrease in the concentration of dmn to about 15 nmol l was observed high temperature fluids 128 198 c 1997 1999 90 c 2001 venting simultaneously from different orifices within pele s pit had distinguishable fe mn ratios that can be attributed to different subseafloor origins fe mn ratios characteristic of fluids moderated by high temperature water rock reaction had low values in 1997 1998 1 6 0 7 increasing to about 7 in 1999 fluids moderated by magmatic degassing of co2 had much higher fe mn ratios increasing from 24 15 in 1997 1998 to 50 in 1999 and 63 87 in 2001 fe mn values of dispersing plumes at l ihi reflect an admixture of these sources and a relative fe abundance that is consistently high compared to mid ocean ridge systems the pulsed injection of mn and fe into the surrounding ocean associated with the 1996 tectonic magmatic event at l ihi was massive our decadal observations confirm that mn and fe are useful markers of the magnitude and evolution of the effects of magmatic perturbation on hydrothermal systems influenced by chronic magmatic degassing

dissolved and particulate fe in a hydrothermal plume at 9 45 n east pacific rise slow fe ii oxidation kinetics in pacific plumes production of fe iii particles in hydrothermal plumes is of fundamental importance to the long term effect of hydrothermal circulation on seawater composition to elucidate the fundamental controls on fe redox kinetics and solution particle partitioning in neutrally buoyant plumes we sampled near field 3 km plume particles at 9 45 n on the east pacific rise in 1996 returning in 1997 to sample both particulate and dissolved phases 0 40 m filter concentrations of dissolved fe varied from 320 to 20 nm in proximal 0 3 km from vent site to distal samples 1 3 km downfield constituting 85 50 of total fe respectively based on vent fluid dilution factors calculated from dissolved mn a mass balance for vent fluid fe at this site indicates that 65 of fe is lost to particulate sulfide settling in the buoyant plume and that particulate fe in distal 1 3 km samples is twice as concentrated as predicted from dilution of particles in proximal plume water these observations are consistent with a calculated fe ii oxidation half time of 3 3 h long enough that fe iii colloid production and aggregation occurs primarily in the neutrally buoyant plume at relatively high dilutions preventing generation of high particulate fe concentrations 11 56 nm observed a general investigation of fe ii oxidation rates in plumes worldwide gives fe ii oxidation half lives as short as 17 min at some atlantic sites and as long as 6 h at some pacific sites the calculations indicate that the distribution of fe particles in plumes depends chiefly on inter basin differences in ambient deep water chemistry primarily ph and dissolved o2 and on local currents driving plume dilution and to a much lesser extent on variations in primary vent fluid composition long term changes in thermohaline circulation or ocean biogeochemistry may therefore alter fe dynamics and minor element fluxes associated with global hydrothermal activity independent of variations in crustal production rates

deep sea benthic foraminiferal species diversity in the ne atlantic and nw arabian sea a synthesis abstract we present a synthesis of species diversity data fishers alpha index shannon wiener log 2 es 100 rank 1 dominance for live stained foraminifera from five bathyal 1340 m depth and abyssal 4450 4950 m depth sites in the ne atlantic and a 3400 m deep site in the arabian sea three atlantic sites porcupine seabight biotrans porcupine abyssal plain are subject to seasonal phytodetritus inputs that support low diversity populations 8 17 species in other respects the foraminifera are highly diverse the meiofaunal fractions 45 or 63 m including fragmented and phytodetritus species of abyssal atlantic samples yielded 110 and 170 species in the 0 1 cm and 0 10 cm layers respectively the arabian sea sample 0 1 cm layer only yielded 232 species in both cases values for diversity measures were very high diversity was rather lower in bathyal porcupine seabight samples 0 1 cm layer which yielded 500 m porcupine and madeira abyssal plains was also speciose 113 133 species but diversity measures were lower and dominance higher than for the meiofauna all assemblages contained numerous undescribed species many belonging to poorly known monothalamous soft bodied taxa sample diversity was influenced by several factors combining phytodetrital and sediment populations reduced diversity and increased dominance slightly the inclusion of deeper sediment layers and finer sieve fractions had the opposite effect the inclusion of fragments had more impact on macrofaunal than on meiofaunal diversity although in both cases the effect was inconsistent either positive or negative porcupine and madeira abyssal plain multicore samples 63 m fraction contained substantially more foraminiferal species than nematode species the numbers of foraminiferal species in boxcore samples 500 m fraction were comparable to or greater than literature values for macrofaunal taxa such as polychaetes and isopods few of the more abundant species at our atlantic abyssal plain and arabian sea sites are endemic this is consistent with literature evidence that many common deep sea foraminiferal species are cosmopolitan and implies that global foraminiferal diversity may be more modest than the high sample diversity might suggest calcareous foraminifera which are well known taxonomically and have a good fossil record may provide a model for diversity patterns among the deep sea benthic biota in general

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

a comparison of early paleogene export productivity and organic carbon burial flux for maud rise weddell sea and kerguelen plateau south indian ocean 1 marine biological productivity has been invoked as a possible climate driver during the early paleogene through its potential influence on atmospheric carbon dioxide concentrations however the relationship of export productivity the flux of organic carbon c from the surface ocean to the deep ocean to organic c burial flux the flux of organic c from the deep ocean that is buried in marine sediments is not well understood we examine the various components involved with atmosphere to ocean c transfer by reconstructing early paleogene carbonate and silica production using carbonate and silica mass accumulation rates mars export productivity using biogenic barium bio ba mars organic c burial flux using reactive phosphorus p mars redox conditions using uranium and manganese contents and the fraction of organic c buried relative to export productivity using reactive p to bio ba ratios our investigations concentrate on paleocene eocene sections of sites 689 690 from maud rise and site 738 from kerguelen plateau in both regions export productivity organic c burial flux and the fraction of organic c buried relative to export productivity decreased from the paleocene early eocene to the middle eocene a shift is indicated from an early paleogene two gyre circulation in which nutrients were not efficiently recycled to the surface via upwelling in these regions to a circulation more like the present day with efficient recycling of nutrients to the surface ocean export productivity was enhanced for kerguelen plateau relative to maud rise throughout the early paleogene possibly due to internal waves generated by the plateau regardless of gyre circulation

latest eocene early oligocene climate change and southern ocean fertility inferences from sediment accumulation and stable isotope data abstract the earliest oligocene 33 5 ma is marked by a major step in the long term transition from an ice free to glaciated world the transition characterized by both cooling and ice sheet growth triggered a transient but extreme glacial period designated oi 1 high resolution isotope records suggest that oi 1 lasted for roughly 400 000 yr the duration of magnetochron 13n before partially abating and that it was accompanied by an ocean wide carbon isotope anomaly of 0 75 one hypothesis relates the carbon isotope anomaly to enhanced export production brought about by climate induced intensification of wind stress and upwelling particularly in the southern ocean to understand how this climatic event affected export production in the southern ocean biogenic silica opal and carbonate accumulation rates were computed for the sub polar indian ocean using deep sea cores from odp site 744 kerguelen plateau our findings suggest that net productivity in this region increased by several fold in response to the oi 1 glaciation in addition calcareous primary producers dominant in the late eocene were partially replaced by opaline organisms suggesting a trend toward seasonally greater surface divergence and upwelling in this sector of the southern ocean we attribute these changes to intensification of atmospheric oceanic circulation brought about by high latitude cooling and the appearance of a full scale continental ice sheet on east antarctica higher terrigenous sediment accumulation rates support the idea that wind induced changes in regional productivity were augmented by an increased supply of glacial dust and debris that provided limiting micro nutrients e g iron rich dust particles we speculate that the rapid changes in biogenic sediment accumulation in the southern ocean and other upwelling dominated regions contributed to the ocean wide positive carbon isotope anomaly by temporarily increasing the burial rate of organic carbon relative to carbonate carbon the changes in burial rates in turn may have produced a positive feedback on climate by briefly drawing down atmospheric pco2

temporal and spatial variability of hydrothermal manganese and iron at cleft segment juan de fuca ridge a unique data set for hydrothermal mn and fe was collected at cleft segment on the juan de fuca ridge between 1983 and 1991 the data set includes observations of focused and diffuse venting fluids and neutrally buoyant plumes formed by chronic and episodic venting manganese heat and iron heat ratios for plumes from the north end of the cleft segment were combined with independently determined estimates of plume heat flux to yield annually averaged chronic venting fluxes for mn of 0 36 0 17 mol s 1 and for fe of 0 61 0 34 mol s 1 over 6 years of plume measurements at north cleft segment observed episodic hydrothermal discharge accounted for 15 of the total vented mn and 35 of vented fe the chronic fluxes for mn and fe at a second venting center located at the south end of the cleft segment were estimated to be approximately equal to the fluxes at north cleft segment chronic plumes at north cleft segment are mixtures of focused and diffuse discharge that contribute heat mn and fe in variable proportions similar examination of south cleft segment data strongly suggests the presence of an as yet unobserved venting source relatively depleted in mn and fe but contributing substantially to the overall heat temporal and spatial variations in the concentrations of mn and fe and in mn heat and fe heat ratios for focused seafloor vents were difficult to resolve within complex chronic plumes manganese heat and iron heat ratios of megaplumes suggest they may have derived from reservoirs of diffuse fluids while smaller event plumes may have formed by different processes and have properties similar to chronic plumes the accurate assessment of segment scale hydrothermal fluxes of mn and fe requires coordinated measurements of representative seafloor sources and the neutrally buoyant plume that integrates all seafloor discharge

changes in benthic ecosystems and ocean circulation in the southeast atlantic across eocene thermal maximum 2 eocene thermal maximum 2 etm2 occurred 1 8 myr after the paleocene eocene thermal maximum petm and like the petm was characterized by a negative carbon isotope excursion and warming we combined benthic foraminiferal and sedimentological records for southeast atlantic sites 1263 1500 m paleodepth and 1262 3600 m paleodepth to show that benthic foraminiferal diversity and accumulation rates declined more precipitously and severely at the shallower site during peak etm2 as the sites are in close proximity differences in surface productivity cannot have caused this differential effect instead we infer that changes in ocean circulation across etm2 may have produced more pronounced warming at intermediate depths site 1263 the effects of warming include increased metabolic rates a decrease in effective food supply and increased deoxygenation thus potentially explaining the more severe benthic impacts at site 1263 in response bioturbation may have decreased more at site 1263 than at site 1262 differentially affecting bulk carbonate records we use a sediment enabled earth system model to test whether a reduction in bioturbation and or the likely reduced carbonate saturation of more poorly ventilated waters can explain the more extreme excursion in bulk 13c and sharper transition in wt caco3 at site 1263 we find that both enhanced acidification and reduced bioturbation during the etm2 peak are needed to account for the observed features our combined ecological and modeling analysis illustrates the potential role of ocean circulation changes in amplifying local environmental changes and driving temporary but drastic loss of benthic biodiversity and abundance

the response of deep water benthic foraminiferal assemblages to changes in paleoproductivity during the pleistocene last 769 2 kyr western south atlantic ocean abstract benthic foraminiferal assemblages and 18 o records in a core from santos basin western south atlantic 2220 m water depth were analyzed to investigate productivity changes during the pleistocene the sediment core recorded the last 770 kyr including marine isotope stages mis 19 to 1 the four dominant benthic foraminiferal assemblages were identified using q mode varimax factor analysis and are represented by globocassidulina crassa bolivina spp epistominella exigua and alabaminella weddellensis from 769 2 kyr mis 19 to 300 kyr mis 8 the highest values of factor 2 bolivina spp assemblage indicate increased influx of organic matter to the seafloor and a slight decrease in the oxygen concentration at the sediment water interface this condition began to change in the stage 8 288 9 kyr to 268 3 kyr and it is characterized by high values of factor 1 when the g crassa assemblage became dominant indicating an increase in oxygen concentrations and a decrease in the influx of organic matter seasonally pulsed organic matter resulting in a distinct phytodetritus layer accumulated mostly during the glacial mis 14 10 8 6 and 5 2 5 1 and in the interglacial stage 11 and the end of 9 as indicated by factor 3 e exigua assemblage and factor 4 a weddellensis assemblage the highest peak of the a weddellensis assemblage during mis 11 401 4 kyr coincides with the mid brunhes event the highest benthic foraminiferal accumulation rates occurred during mostly glacial stages indicating delivery of more organic matter to the seafloor the changes in benthic foraminifera assemblages in the glacial stages during the pleistocene indicate changes in primary productivity in surface waters increasing the amount of organic matter delivered to the seafloor amplified the benthic foraminiferal response

paleoceanographic significance of deep sea benthic foraminiferal species diversity at southeastern indian ocean hole 752a during the neogene abstract diversity parameters of neogene deep sea benthic foraminifera were measured at ocean drilling program odp hole 752a southeastern indian ocean water depth of 1086 3 m using information function h equitability e number of species s and sander s rarefaction values these parameters combined with population abundance of dominant benthic foraminifera bulimina macilenta nuttallides umbonifera cibicides wuellerstorfi cibicides lobatulus bolivina pusilla ehrenbergina carinata gavelinopsis lobatulus cassidulina laevigata globocassiulina subglobosa reveal significant paleoceanographic changes in the southeastern indian ocean during the neogene the values of all the diversity parameters show a decrease from 25 to 23 ma and thereafter an increase with peak values at 13 5 ma the late oligocene to earliest miocene was an interval of more unstable conditions at hole 752a dominated by species characteristic of low organic carbon well ventilated carbonate corrosive high energy conditions the highest values of diversity parameters coincide with the early middle miocene climatic optimum all these parameters show a declining trend and gradual decrease from 13 5 to 4 5 ma coinciding with the major build up of ice sheets in the antarctic region major increase in b pusilla and e carinata population during this time suggests high nutrient levels and low oxygen conditions at hole 752a this interval corresponds with the so called biogenic bloom and an intense oxygen minimum zone as observed throughout the indo pacific region deep waters were warmer from 4 5 to 3 ma marked by an increase in species diversity values coinciding with the early middle pliocene warmth the species diversity values abruptly decreased in the younger interval contemporaneous with the major northern hemisphere glaciation during this time species characteristics of high energy bottom currents and relatively cold deep water were dominant

mud volcanoes at the front of the makran accretionary complex pakistan abstract conical mounds 1 1 5 km in diameter and up to 65 m high were mapped at the foot of the active makran continental margin the mounds developed seaward of the accretionary front in a relatively planar zone where the beginning of build up of tectonic pressure initiates deformation based on shallow high resolution 4 khz sediment echosounding the sedimentary sequence in this area is generally well stratified as indicated by closely spaced horizontal reflections however in the vicinity of the mounds the sediment is characterised by many acoustically transparent zones which are 100 300 m in diameter and cut near vertically through the horizontal reflectors two sediment cores from the top of the largest cone and a neighbouring acoustically transparent zone reveal small scale post depositional deformation in a stratified sequence and methane concentrations up to 40 000 ng g this deformation and disruption of potential reflectors provides a clue to explain the acoustic transparency we interpret it as caused by the rise of charged fluids and mud leading initially to the slight disturbance of the generally good acoustic reflectors and eventually to the formation of conical mud mounds mud volcanoes mcs data showing a buried mound in an analogous structural position support the idea of tectonically induced mud fluid expulsion seaward of the accretionary front

changes in the water column structure and paleoproductivity in the western south atlantic ocean since the middle pleistocene evidence from benthic and planktonic foraminifera abstract based on an integrated approach planktonic and benthic foraminifera and stable isotopes carried out in two cores collected on continental slope of santos basin central brazil the paleoceanographic oscillations of the last 570 ka are documented benthic foraminiferal isotopic records coupled with foraminiferal assemblages analyses show 100 ky long term oscillation in the superficial productivity along the middle pleistocene these long term oscillations are interrupted by 30 ky short term changes that mark the transition periods of higher productivity 425 400 ka and 190 160 ka and lower 290 260 ka the planktonic foraminifera species allowed the recognition of changes in the water column structure and in the superficial productivity observed in the area those changes in the superficial waters promoting different organic matter export to the sea floor might have resulted in changes on the more abundant and phytodetritus opportunist benthic taxa epistominella exigua and alabaminella weddellensis

late eocene oligocene oceanographic development at southern high latitudes from terrigenous and biogenic particles a comparison of kerguelen plateau and maud rise odp sites 744 and 689 abstract detailed investigation 630 samples of clay mineral assemblages and benthic foraminifer accumulation rates bfar as a proxy for paleoproductivity has been conducted on two late eocene oligocene sequences drilled at intermediate water depths of the kerguelen plateau and maud rise southern ocean distinct changes in clay assemblages and bfar that are in general a factor two higher on the maud rise compared to the kerguelen plateau unravel a step by step evolution of marine and continental antarctic environments that eventually resulted in permanent ice coverage and dense cold water formation 1 late eocene dominance of chemical weathering was associated with intermittent erosion of antarctic soils and substrates main erosional events are recorded at 36 and 34 ma prior to the major earliest oligocene glacial event and are especially noticeable in the indian sector of the southern ocean 2 physical weathering progressed in continental areas adjacent to the maud rise and intermediate water production intensified in the indian sector of the southern ocean throughout the eocene oligocene transition as the tasmanian seaway developed environmental changes and a strong 600 kyr lasting peak of paleoproductivity seem closely associated with the earliest oligocene isotope shift and the accumulation of ice rafted detritus on the kerguelen plateau 3 aridity and physical weathering progressed in east antarctica near the maud rise site 689 at 33 2 33 15 ma as polar transfer of heat within the deep ocean increased slightly this may have prevented extensive ice development during at least part of the early oligocene 4 increased productivity vertical mixing and turnover at site 744 on the kerguelen plateau followed by a two step increase of physical weathering on the adjacent continent from 32 to 31 2 ma suggest progressive homogenization of climates and circulation as the passageway south of tasmania widened and deepened 5 physical weathering reached a maximum in east antarctic areas adjacent to the maud rise and a hiatus developed on the kerguelen plateau during the mid oligocene oi2 oi2a interval 31 26 5 ma in possible relation with opening processes of the modern drake passage and scotia sea and a further step in the development of oceanic circumpolar circulation 6 near 400 kyr cycles of productivity and clay mineral composition throughout the two sequences suggest that orbital frequencies played a role in the small scale variations of both continental and marine antarctic environments of the late paleogene

atlantic paleobathymetry paleoproductivity and paleocirculation in the late albian the benthic foraminiferal record spatial distribution patterns of benthic foraminifers in upper albian sediments from 25 dsdp odp sites and 31 onshore sections of the north and south atlantic ocean are used to generate paleobathymetric reconstructions and to identify areas of high primary production such as coastal and equatorial upwelling zones new paleobathymetric estimates are provided for dsdp odp sites and onshore locations that are not situated on oceanic crust paleobathymetric reconstructions indicate shallow water exchange between the north and south atlantic but show the existence of a deep water connection between the western and eastern tethys 2500 m through the gibraltar gateway strikingly there is no evidence for a strong latitudinal gradient in deep water benthic foraminiferal distribution during the late albian south atlantic assemblages show close affinity to north atlantic and tethyan assemblages exhibiting only a minor degree of provincialism biogeographic patterns reveal a distinct asymmetry in late albian paleoproductivity for the north atlantic as for the present day the eastern margins of the atlantic were generally more productive than the western margins and a belt of enhanced carbon aux export to the seafloor can be traced around the north african coast which probably corresponded to a zone of vigorous coastal upwelling by contrast assemblage composition in the south atlantic generally reflects mesotrophic to oligotrophic conditions benthic foraminiferal distribution patterns thus provide robust proxy data to test predictions from paleocirculation and paleobathymetric models for the mid cretaceous atlantic ocean and adjacent margins c 2001 elsevier science b v all rights reserved

use of multiproxy records on the agulhas ridge southern ocean ocean drilling project leg 177 site 1090 to investigate sub antarctic hydrography from the oligocene to the early miocene 1 ocean drilling program odp site 1090 on the agulhas ridge in the south atlantic sector of the southern ocean is ideally located to capture changes in southern ocean circulation patterns using samples taken from cored sediments we construct multiproxy records of productivity biogenic barium baex opal and caco3 mass accumulation rates mars nutrient and organic carbon burial reactive phosphorus pr mars and redox conditions u and mn enrichments to investigate hydrographic conditions associated with climatic shifts from the oligocene through the early miocene orbitally induced cyclicity in u and mn enrichments 100 kyr suggests shifts in deepwater characteristics however caco3 dissolution coincident with low u and mn enrichments does not indicate low oxygen corrosive waters similar to modern conditions these observations indicate that a well developed modern type antarctic circumpolar current acc did not yet exist over the period from 30 to 20 ma with two potential consequences the southern ocean was not functioning as a silica trap permitting a broader distribution of silica that may have facilitated organic carbon burial in the ocean in general and the lack of a deeply mixing acc may have facilitated organic carbon burial in the southern ocean both the relative high opal mars coincident with low caco3 mars and absolute high pr mars burial of organic carbon suggest a powerful mechanism for pco2 drawdown

palaeoproductivity linked to monsoon variability in the northern slope of the south china sea from the last 290 kyr evidence of benthic foraminifera from core sh7b

cenozoic record of elongate cylindrical deep sea benthic foraminifera in the north atlantic and equatorial pacific oceans abstract in the late pliocene middle pleistocene a group of 95 species of elongate cylindrical deep sea lower bathyal abyssal benthic foraminifera became extinct this extinction group ext gp belonging to three families all the stilostomellidae and pleurostomellidae some of the nodosariidae was a major component 20 70 of deep sea foraminiferal assemblages in the middle cenozoic and subsequently declined in abundance and species richness before finally disappearing almost completely during the mid pleistocene climatic transition mpt so what caused these declines and extinction in this study 127 ext gp species are identified from eight cenozoic bathyal and abyssal sequences in the north atlantic and equatorial pacific oceans most species are long ranging with 80 originating in the eocene or earlier the greatest abundance and diversity of the ext gp was in the warm oceanic conditions of the middle eocene early oligocene the group was subjected to significant changes in the composition of the faunal dominants and slightly enhanced species turnover during and soon after the rapid eocene oligocene cooling event declines in the relative abundance and flux of the ext gp together with enhanced species loss occurred during middle late miocene cooling particularly at abyssal sites the overall number of ext gp species present began declining earlier at mid abyssal depths in middle miocene than at upper abyssal in late pliocene early pleistocene and then lower bathyal depths in mpt by far the most significant ext gp declines in abundance and species loss occurred during the more severe glacial stages of the late pliocene middle pleistocene clearly the decline and extinction of this group of deep sea foraminifera was related to the function of their specialized apertures and the stepwise cooling of global climate and deep water we infer that the apertural modifications may be related to the method of food collection or processing and that the extinctions may have resulted from the decline or loss of their specific phytoplankton or prokaryote food source that was more directly impacted than the foraminifera by the cooling temperatures

abyssal ne atlantic benthic foraminifera during the last 15 kyr relation to variations in seasonality of productivity abstract benthic foraminiferal faunas 63 m and stable isotopes from the last 15 kyr were studied in bengal programme high resolution temporal and spatial study of the benthic biology and geochemistry of a north eastern atlantic abyssal locality kasten core 13078 16 from the porcupine abyssal plain ne atlantic 48 49 91 n 16 29 94 w water depth 4844 m changes occurred in the accumulation rates species composition diversity and stable isotopes during the last 15 kyr today the area is strongly influenced by seasonal inputs of phytodetritus following the spring blooms in surface water primary productivity variations in the relative abundance of the two most abundant species epistominella exigua and alabaminella weddellensis which today show significant increases in abundance with the presence of phytodetritus on the sea floor are interpreted as resulting from changes in the seasonality of productivity seasonal productivity was higher during the holocene than during the last deglaciation and younger dryas probably coinciding with the retreat of the polar front to higher latitudes this hypothesis is consistent with simultaneous decreases in the percentage of the polar planktic foraminifera neogloboquadrina pachyderma s and increases in the percentage of globigerina bulloides a warmer water planktic foraminifera indicative of phytoplankton blooms and enhanced productivity the relative abundance of the phytodetritus species e exigua and a weddellensis covary between 14 7 and 8 1 kyr but not between 7 8 and 1 2 kyr major decreases in the numbers per gram and accumulation rates of planktic and benthic foraminifera occurred at 12 8 5 kyr and at 4 kyr which correspond to decreases in the sediment coarse fraction and published data on inorganic carbon contents suggesting that dissolution may have increased at these times relationships between benthic foraminiferal faunas and benthic stable isotope records suggest no simple relationship between faunal abundances and test isotope chemistry for example the abundances of phytodetritus species do not show strong correlations with either the 13c values of e exigua or the 13c e exigua p wuellerstorfi record which have previously been suggested as indicative of seasonality of productivity

high resolution record of export production in the eastern equatorial pacific across the eocene oligocene transition and relationships to global climatic records 1 understanding changes in export production through time provides insight into the response of the biological pump to global climate change particularly during periods of rapid climate change in this study we consider what role changes in export production may have had on carbon sequestration and how this may have contributed to the onset of the eocene oligocene transition eot in addition we consider if these export production variations are dominantly controlled by orbitally driven climate variability to accomplish these objectives we report changes in export production in the eastern equatorial pacific eep from site u1333 across the eot reconstructed from a high resolution record of marine barite accumulation rates bar bar fluctuations suggest synchronous declines in export production associated with the two step increases in oxygen isotopes that define the transition the reduction in productivity across the eot suggests that the biological pump did not contribute to carbon sequestration and the cooling over this transition we also report a previously undocumented peak in eep export productivity before the eot onset this peak is consistent with export production proxies from the southern ocean potentially implying a global driver for this precursor event we propose that this enhanced export production and the associated carbon sequestration in the late eocene may have contributed to the pco2 drawdown at the onset of antarctic glaciation

trends in caribbean paleoproductivity related to the neogene closure of the central american seaway abstract this study tests the hypothesis that the late miocene to early pliocene constriction and closure of the central american seaway cas connecting the tropical atlantic and east quatorial pacific eep caused a decrease in productivity in the caribbean due to decreased coastal upwelling and an end to the connection with high productivity tropical pacific waters the present study compared paleoceanographic proxies for the interval between 8 3 and 2 5 ma in 47 samples from south caribbean odp site 999 with published data on eep dsdp site 503 proxies for site 999 include the relative abundance of benthic foraminiferal species representing bottom current velocity and the flux of organic matter to the sea floor the ratio of infaunal epifaunal benthic foraminiferal species and benthic foraminifer accumulation rates bfars in addition we calculated resistant planktic foraminifers species and used the previously published sand fraction and benthic carbon isotope values from site 999 during early shoaling of the isthmus 8 3 7 9 ma the caribbean was under mesotrophic conditions with little ventilation of bottom waters and low current velocity the pre closure interval 7 6 4 2 ma saw enhanced seasonal input of phytodetritus with even more reduced ventilation and enhanced dissolution between 6 8 and 4 8 ma during the post closure interval 4 2 2 5 ma in the caribbean paleoproductivity decreased current velocity was reduced and ventilation improved while the seasonality of phytodetrital input was reduced dramatically coinciding with the establishment of the atlantic pacific salinity contrast at 4 2 ma our data support the hypothesis that late miocene constriction of the cas at 7 9 ma and its closure at 4 2 ma caused a gradual decrease in paleoproductivity in the caribbean consistent with decreased current velocity and seasonality of the phytodetrital input

ne atlantic benthic foraminifera modern distribution patterns and palaeoecological significance microfaunal evidence is presented from a region in the ne atlantic ocean characterized by well constrained and very uniform physiochemical water mass properties but a significant gradient in surface ocean productivity notable changes in the species composition of benthic foraminiferal assemblages can be directly related to surface productivity and particulate organic matter supply to the deep ocean floor because of the labile nature of much organic matter as it reaches the sea floor it is argued that benthic foraminifera which exhibit a high preservation potential in most marine sediments provide a better proxy for estimating past fluxes than bulk sediment organic carbon oc content three distinct assemblage groups are recognized a cassidulina laevigata group which is dominated by infaunal species and a relatively high sediment oc content a rhizammina spp group which is also dominated by infaunal species and an epistominella exigua group dominated by epifaunal taxa and falling sediment oc content significant faunal assemblage changes appear to be independent of grain size

neogene and quaternary paleoceanographic changes in the southern south china sea site 1143 the benthic foraminiferal record deep sea benthic foraminiferal assemblages from ocean drilling program odp site 1143 located in the southern south china sea scs were investigated to evaluate the relationship between faunal composition patterns and paleoceatiographic changes during the last 6 million years late miocene to holocene we used multivariate statistics correspondence analysis to analyze carbon flux related changes in assemblage composition of benthic foraminifers additional proxies for carbon flux and deep water ventilation include delta 13 c records of epifaunal cibicidoides wuellerstoifi and infaunal uvgefina peregrina var dirupta and melonis pompilioides benthic foraminiferal accumulation rates bfarss diversity indices and relative abundances of indicator species we observe three significant benthic faunal changes in the southern south china sea during the last 6 million years strong fluctuations in bfar and relative abundance of productivity indicator species between glacial and inter glacial stages after the mid pleistocene revolution mpr at approximately 0 9 ma indicating stronger seasonal carbon flux fluctuations are accompanied by the extinction of such species as stilostomella spp increases in carbon flux indicator species are coupled with an overall deer ease in benthic foraminifer diversity around 3 0 ma in the late pliocene this may indicate increasing carbon flux in a period of productivity maximum caused by enhanced offshore upwelling from intensified winter monsoon wind strength c 2004 elsevier b v all rights reserved

biodiversity and distribution patterns of deep sea fauna along the temperate nw pacific abstract the deep nw pacific has been intensively analyzed in the last decade during an international collaboration between german and russian scientists which has resulted in a vast unique collection of material from previously unexplored areas until now the environmental forces that could be driving species richness patterns in the deep nw pacific have not been explored widely therefore in this paper we utilize new species distribution data from four deep sea expeditions to the nw pacific 2010 2016 which include the sea of japan sea of okhotsk the abyssal plain adjacent to the kuril kamchatka trench kkt and the kkt to better understand species connectivity biodiversity patterns and distribution ranges in deep sea benthos in this region to determine the best environmental predictors driving these deep sea species richness patterns we applied generalized additive gams and linear models glms we calculated the total number of geographic distribution records alpha total number of species per 10 000 km2 hexagonal cells and gamma species richness total number of species per 1 latitudinal bands and expected number of species rarefaction es15 our highest number of distribution records and gamma species richness during the last decade peaked at intermediate latitudes 42 44 n along the mesopelagic zone 500 1000 m of the sea of japan and abyssopelagic zone 4000 6000 m of the nw pacific and kkt when sampling bias was accounted for the alpha species richness in bathypelagic zone 1000 4000 m of sea of okhotsk and abyssopelagic zone 4000 6000 m of the nw pacific and kkt were as high as mesopelagic zone of the sea of japan the similarity cluster analysis of species presence absence in lower bathyal hadal 3000 8500 m revealed three distinct geographic regions including sea of japan sea of okhotsk and kkt in the nw pacific the eastern sector of the sea of okhotsk and western kkt had c 50 of species in common several species of deep sea bivalves such as dacrydium rostriferum and vesicomya pacifica had the greatest latitudinal distribution ranges among all species echinoderm ophiura leptoctenia had instead the broadest bathymetric distribution ranges compared to all other collected species gam models indicated that dissolved oxygen was the best explanatory variable for predicting numbers of species closely followed by the model including all environmental variables plus topography however the glm models of species richness with latitudinal intervals of 1 and 5 found that the topography and temperature were the best predictors of number of species glm model outputs indicated that a model that contains only the number of distribution records is for all practical purposes as good as any model that contains an environmental predictor this study provides new insights on the nw pacific deep sea species richness patterns where dissolved oxygen might play an important role especially when considering the oxygen minimum zones omzs in the deep nw pacific

factors influencing the distribution patterns of recent deep sea benthic foraminifera east of new zealand southwest pacific ocean abstract this study investigates which combination of environmental factors most strongly influences the distribution patterns of benthic foraminferal tests 0 63 m in a region bisected by the subtropical front east of new zealand seafloor sample sites extend from outer shelf 90 m to abyssal 4700 m depths across substrates ranging from biogenic terrigenous gravelly sand to hemipelagic mud and occur under the influence of antarctic intermediate water aaiw and circumpolar deep waters as well as receiving detritus from both subtropical and subantarctic surface water masses elevated values of the planktic foraminiferal fragmentation index and reworked small paleogene planktic foraminifera at outer shelf and bathyal depths coincide with areas of strong bottom currents q mode cluster analysis on the census counts of 398 benthic species clusters the 66 samples into three large groups shallow bathyal abyssal and at a lower level 10 mappable associations are recognised a combination of canonical correspondence analysis and a correlation coefficient matrix was used to relate the faunal data to a set of measured environmental proxies these analyses show that factors that have a relationship with depth are the most significant in determining foraminiferal distribution the principal environmental factors which appear to most strongly influence this benthic foraminiferal distribution are dissolved oxygen content in bottom waters sustainability of organic carbon flux rates seasonality of food supply lateral advection of water masses bottom water carbonate corrosiveness energetic state at the benthic boundary layer grain size composition of substrate salinity and temperature of the bottom waters shallow water associations 90 1250 m dominated by cassidulina carinata and trifarina angulosa occur within coarse substrates under well oxygenated high energy regimes and sustained food input the occurrence of the bathyal associations 230 2840 m dominated by c carinata alabaminella weddellensis and abditodentrix pseudothalmanni closely mirrors the distribution of aaiw within a region of variable food supply the sustainability of food supply combined with bottom water type and associated ventilation and dissolution strongly influence the composition of abyssal associations 1200 4700 m mostly dominated by epistominella exigua and a weddellensis

the eocene oligocene boundary and the psychrospheric event in the tethys as recorded by deep sea ostracods from the massignano global boundary stratotype section and point central italy abstract latest eocene earliest oligocene deep water ostracods from the massignano global boundary stratotype section and point gssp central italy were studied from a palaeoecological perspective to investigate the psychrospheric event in the tethys although quantitative analyses were hampered by the low incidence of fauna the high resolution sampling used in this study 148 samples distributed over a 23 m thick succession spanning 3 m y allowed the following inferences 1 overall features e g abundance diversity composition of the assemblages suggest a middle lower bathyal environment with no significant palaeobathymetrical changes 2 today a similar fauna notably characterised by the common occurrence of the genus agrenocythere would likely be encountered in upper psychrospheric conditions water masses beneath the permanent thermocline with a temperature range of 4 10 c 3 although no noticeable faunal turnover has been recognised throughout the succession minor faunal changes seem to occur in the first part of the section probable appearance of legitimocythere presequenta and to a lesser extent also across the eocene oligocene boundary the presumed appearance of l presequenta latest eocene correlates quite well in timing and possible significance with the faunal changes observed in other microfossil groups foraminifers and dinocysts this event is possibly linked to a cooling pulse which might have been caused by the arrival or increasing advection of cold bottom waters in the study area faunal evolution across the eocene oligocene boundary is thought to be consistent with an intensification of the cooling trend and an increase of primary productivity which fits fairly well with the 13c record relationships between the subtle ostracod faunal changes observed in the massignano gssp and the main late eocene early oligocene psychrospheric event can be only speculative nevertheless we found no evidence that precludes the possibility of interpreting the massignano ostracod pattern as a subdued local expression of this major event although speculative this is a reasonable hypothesis because the investigated area is situated in western tethys far from the main circulation of deep ocean waters

benthic foraminiferal abundance and stable isotope changes in the indian ocean sector of the southern ocean during the last 20kyr paleoceanographic implications abstract benthic foraminiferal faunas and benthic stable isotopes during the last 20 kyr were investigated in core md02 2488 46 28 8 s 88 01 3 e 3420 m water depth from the southeast indian ocean sector of the southern ocean in order to document paleoceanographic changes from the last glacial through deglaciation and into the holocene variations occurred in the accumulation rates species composition diversity and stable isotopes during the last 20 kyr the benthic 18o and 13c records during the last 28 kyr show that no significant deep water circulation changes took place before 15 6 calendar kyr ka the 13c increase at 15 6 ka is interpreted as reflecting the arrival of better ventilated deep waters at the site and is associated with the progressive increase in of miliolids from 15 ka to 0 ka an interval 16 15 ka of low benthic foraminiferal accumulation rates bfars and an increase in the relative abundance of stainforthia complanata deep waters were 2 2 0 4 c colder during the last glacial than at present carbonate dissolution proxies indicate that carbonate dissolution was higher during the last glacial than during the last deglacial and holocene bfars and the percentage of species indicative of high productivity suggest that the flux of organic matter resulting from surface water productivity was generally higher between 20 and 13 ka than between 12 and 0 ka consistent with the observed higher proportion of biosiliceous sediment at 20 14 ka and published records the combined percentages of the two most abundant species alabaminella weddellensis and epistominella exigua phytodetritus species suggest that seasonality of productivity intermittency of primary productivity fluctuated over the last 20 kyr and was higher during the last glacial and deglaciation 20 10 ka compared with the holocene 10 0 ka the relative abundances of a weddellensis and e exigua do not covary over the last 20 kyr an observation also reported from other areas

temporal variability in living deep sea benthic foraminifera a review the deep ocean environment is disturbed by various processes many of which involve episodic inputs of organic matter some inputs e g phytodetritus at mid high latitudes in the north atlantic and northeast pacific are seasonally pulsed others e g falls of whale carcasses are irregular and unpredictable but together they evoke a variety of responses from the benthic biota in the case of deep sea foraminifera only those responses arising from seasonal food pulses have been fairly well documented the population dynamics of deep sea benthic foraminifera total live populations and individual species appear to be controlled largely by two inversely related parameters the flux of organic matter to the seafloor and concentrations of oxygen in the sediment porewater organic matter food inputs are most intense along bathyal continental margins and their oxidation often leads to the depletion of oxygen in surface sediments under these conditions foraminiferal faunas are dominated by low oxygen tolerant infaunal species the abundance of which fluctuate in response to seasonally varying amounts of food and oxygen at some sites e g sagami bay off japan species migrate up and down in the sediments tracking critical oxygen concentrations where oxygen concentrations are consistently low less than about 0 5 ml l 1 as in parts of the california borderland foraminifera may undergo population increases solely in response to food pulses in the abyssal north atlantic and in some continental margin areas of this ocean organic matter inputs are weaker and do not lead to oxygen depletion within surface sediments these systems are food limited and seasonal population fluctuations reflect the availability of food phytodetritus rather than oxygen here the species which respond to phytodetritus are mainly epifaunal or shallow infaunal opportunists which represent a small proportion of highly diverse communities 2 or 3 out of 120 species per core of 25 5 cm2 surface area seasonal phytodetrital pulses to the deep seafloor and hence foraminiferal population dynamics are not entirely predictable being dependent on climatic and upper ocean processes they vary in intensity from year to year and occasionally e g at the porcupine abyssal plain pap in 1997 fail to materialise foraminiferal responses to irregular non seasonal organic matter inputs are poorly known however there is some evidence that whale falls turbidite deposits hydrothermal vents and seeps are exploited by species typical of organically enriched low oxygen environments rather than by a specialised fauna fossil foraminiferal assemblages from bathyal and abyssal environments may provide evidence for an increase or decrease in the seasonality of surface production as well as for longer term changes in palaeoproductivity however the accurate interpretation of this record depends on filling the many gaps which remain in our understanding of relations between benthic foraminiferal ecology and seasonal phenomena in the deep ocean

benthic foraminiferal diversity response to the climate induced changes in the eastern arabian sea oxygen minimum zone during the last 30kabp abstract a high resolution record of deep sea benthic foraminiferal diversity variations in the eastern arabian sea for the last 30 ka bp was obtained from two sediment cores sk17 and md131 retrieved from the present day oxygen minimum zone omz in the indian margin off goa the benthic foraminiferal diversity is represented in terms of sander s rarefaction number s 100 shannon wiener index h s equitability e and alpha index records of diversity indices exhibit millennial scale changes during the late glacial and deglacial periods corresponding to the northern hemisphere climatic events we compared the faunal diversity with proxy records of primary productivity c org and bottom water oxygen low o 2 taxa we suggest that benthic foraminiferal diversity in the eastern arabian sea omz is largely controlled by the primary productivity induced organic carbon flux and strength of bottom water oxygenation the less diverse fauna along with increased percentages of c org and low o 2 taxa during the last glacial maximum 18 22 5 ka bp suggest eutrophic and oxygen poor benthic environment attributed mainly to a strong omz associated with intense winter monsoon wind induced productivity and a weak deep ocean circulation the intervals of distinct increase in diversity closely correspond with north atlantic cold heinrich events when eastern arabian sea experienced significant declines in monsoon driven productivity and better deep sea ventilation due to enhanced inflow of antarctic intermediate water aaiw

a 23000 year old record of paleoclimatic and environmental changes from the eastern arabian sea abstract climate of the eastern arabian sea is highly influenced by both global climate and indian monsoon we produced multi proxy records of benthic foraminiferal biofacies and stable isotope ratio 13c and 18o planktic foraminifera and total organic carbon wt content of sediments from core sk291 gc11 in the upper continental shelf off mangalore off eastern arabian sea eas to decipher paleoenvironmental and paleoclimatic changes during the past 23 000 years the monsoon was weak during the last glacial maximum 23 000 18 000 calibrated years before present cal yr bp when sea level was lower globigerinoides ruber populations fluctuate from 30 to 60 in the studied interval with a maximum during 6000 5000 cal yr bp and a minimum during 19 000 17 000 cal yr bp the 18o values of benthic foraminifer ammonia gaimardii suggest pronounced cooling phases during 23 000 18 000 cal yr bp and a short term cooling at 6000 cal yr bp several intervals of high organic productivity and low oxygen conditions were identified based on benthic foraminiferal biofacies during 23 247 682 cal yr bp wind induced surface mixing was intense during 3200 530 cal yr bp as evidenced by high globigerina bulloides abundances the core was affected by moderate chemical weathering and solar variability appears to have been an important forcing factor in shaping climate of the region

attenuation site effects and source parameters in the three gorges reservoir area china the temporal and spatial characteristics of 1924 post impoundment earthquakes m l 0 3 to 3 1 recorded by 26 temporary stations from 16 march 2009 to 14 july 2010 in the three gorges reservoir area hubei province china are investigated in this paper the epicenters are mainly concentrated in three clusters and located along the yangtze river within the range of 10 km from the reservoir waterfront the hypocentral depths range from 0 to 15 km and appear to increase with the epicenters approaching the dam source parameters for 97 selected reservoir induced earthquakes of m l 1 5 were estimated after applying corrections for geometrical spreading frequency dependent q and site effects the results show that the seismic moments m are between 3 96 1011 and 4 07 1013 n m whereas static stress drops are 0 01 0 26 mpa we find the static stress drops in this area vary with seismic moment for our data range approximately as graphic 1 apparent stresses we obtained lie between 0 0019 and 0 049 mpa and also increase with increasing seismic moment indicating that large earthquakes radiate more energy per seismic moment than smaller ones in the three gorges reservoir area and do so more efficiently our results show that reservoir induced earthquakes appear to have systematically lower stress drop with respect to natural tectonic earthquakes by about one order of magnitude this may be attributed to the high pore pressures of the underground medium and the presence of water decreasing the coefficient of friction 1 embed inline graphic 1 gif

benthic foraminifera across the cretaceous paleogene boundary in the southern ocean odp site 690 diversity food and carbonate saturation abstract the impact of an asteroid at the cretaceous paleogene k pg boundary triggered dramatic biotic biogeochemical and sedimentological changes in the oceans that have been intensively studied paleo biogeographical differences in the biotic response to the impact and its environmental consequences however have been less well documented we present a high resolution analysis of benthic foraminiferal assemblages at southern ocean odp site 690 maud rise weddell sea antarctica at this high latitude site late maastrichtian environmental variability was high but benthic foraminiferal assemblages were not less diverse than at lower latitudes in contrast to those of planktic calcifiers also in contrast to planktic calcifiers benthic foraminifera did not suffer significant extinction at the k pg boundary but show transient assemblage changes and decreased diversity at site 690 the extinction rate was even lower 3 than at other sites the benthic foraminiferal accumulation rate varied little across the k pg boundary indicating that food supply to the sea floor was affected to a lesser extent than at lower latitude sites compared to maastrichtian assemblages danian assemblages have a lower diversity and greater relative abundance of heavily calcified taxa such as stensioeina beccariiformis and paralabamina lunata this change in benthic foraminiferal assemblages could reflect post extinction proliferation of different photosynthesizers thus food for the benthos than those dominant during the late cretaceous therefore changes in the nature rather than in the amount of the organic matter supplied to the seafloor however severe extinction of pelagic calcifiers caused carbonate supersaturation in the oceans thus might have given competitive advantage to species with large heavily calcified tests this indirect effect of the k pg impact thus may have influenced the deep sea dwellers documenting the complexity of the effects of major environmental disturbance

diverse basalt types from loihi seamount hawaii loihi seamount is the southeasternmost active volcano in the hawaiian emperor volcanic chain the seamount is considered representative of the early phase of hawaiian volcanism because of its youth small size and location near the melting anomaly seventeen dredge stations recovered transitional basalt alkalic basalt and basanite in addition to the expected tholeiitic basalt four flows of alkalic basalt contain common small dunite xenoliths the recovered samples have thin palagonite rinds and almost no manganese on the glassy surfaces we estimate that the lavas are less than about 4 000 yr old and many are less than 1 000 yr old loihi seamount is apparently in a transitional growth phase between the early eruption of alkalic lavas and the commonly observed subaerial tholeiitic eruptive phase previously thought to dominate hawaiian volcanism from inception until the postcaldera collapse alkalic stage

response of abyssal benthic foraminifera to mid oligocene glacial events in the eastern equatorial pacific ocean odp leg 199 abstract we investigated oligocene and early miocene benthic foraminiferal faunas 105 m in size from ocean drilling program leg 199 site 1218 4826 m water depth and 3300 to 4000 m paleo water depth and site 1219 5063 m water depth and 4200 to 4400 m paleo water depth to understand the response of abyssal benthic foraminifera to mid oligocene glacial events in the eastern equatorial pacific ocean two principal factor assemblages were recognized the factor 1 assemblage common nuttallides umbonifer is related to either an influx of the southern component water scw possibly carbonate undersaturated or a decrease in seasonality of the food supply from the surface ocean the factor 2 assemblage is characterized by typical deep sea taxa living under variable trophic conditions possibly with a seasonal component in food supply the occurrence of abyssal benthic foraminifera faunas during the mid oligocene depends on either the effect of scw or the seasonality of food resources the factor 1 assemblage was most common near 76ol c11r 73ol c10rn and 67ol c9n ca 30 2 29 1 and 26 8 ma respectively by palike et al 2006 this indicates that the effect of scw increased or the seasonal input of food from the surface ocean to benthic environments was weakened close to these glacial events in contrast the huge export flux of small biogenic carbonate particles close to these glacial events might be responsible for carbonate rich sediments buffering carbonate undersaturation changes in deep water masses or the periodicity of food supply from the surface ocean and variation in surface carbonate production affected by orbital forcing had an impact on the mid oligocene faunas of abyssal benthic foraminifera around the intervals of glacial events in the eastern equatorial pacific ocean the factor 1 assemblage decreased sharply at 30 ma 29 8 ma by palike et al 2006 30 0 ma by ck95 and returned to dominance after 29 ma 28 6 ma by palike et al 2006 28 8 ma by ck95 it is likely that the effect of scw possibly carbonate undersaturated has intensified since the late oligocene the faunal transition of benthic foraminifera in the eastern equatorial pacific ocean at 29 ma might be attributable to the influence of northern component water ncw input to the southern ocean and the subsequent formation of scw at about that time

sea level rise and coastal circulation controlled holocene groundwater development in bermuda and caused a meteoric lens to collapse 1600 years ago abstract the recent report from working group ii of the intergovernmental panel on climate change ipcc called for an increased understanding of how groundwater interacts with the ocean atmospheric system this remains a prerequisite to better understand how groundwater will respond to climate change however achieving this goal is hampered by several problems including 1 our minimal understanding of how current groundwater conditions evolved and responded to previous climatic perturbations and 2 the scarcity of techniques available for evaluating prehistoric groundwater subfossil benthic foraminifera in underwater caves are an overlooked method of evaluating prehistoric groundwater on coastal carbonate terrain because they provide a proxy for groundwater salinity and circulation twelve radiocarbon dates and foraminiferal paleoecology from two sediment cores obtained from green bay cave gbc bermuda provide the first holocene scale groundwater reconstruction first the cave floor 20 7 mbsl was flooded at 7 7 ka as north atlantic sea level and groundwater rose in near synchrony over the holocene groundwater conditions salinity circulation and degree of oxygenation shifted a minimum of five times primarily in response to sea level rise most importantly we provide evidence that a prehistoric meteoric lens collapsed at 1 6 ka as sea level rise breached a local sill and completely altered bermudian coastal circulation the complete loss or retreat of a groundwater mass associated with a minor sea level change validates some numerical predictions that small changes in sea level can destabilize coastal groundwater resources when coastal geometry and circulation are considered

paleoceanographic changes during the past 1 9 myr at dsdp site 238 central indian ocean basin benthic foraminiferal proxies abstract deep sea benthic foraminifera have been quantitatively analyzed in samples 125 m size fraction from ocean drilling program odp site 238 to understand paleoceanographic changes in the central indian basin over the past 1 9 myr factor and cluster analyses of the 25 highest ranked species made it possible to identify five biofacies characterizing distinct deep sea environmental settings the environmental interpretation of each biofacies is based on the ecology of recent deep sea benthic foraminifera the benthic faunal record indicates fluctuating deep sea conditions in environmental parameters including oxygenation surface productivity and organic food supply these changes appear to be linked to indian summer monsoon variability the main climatic feature of the indian ocean region the benthic assemblages show a major shift at 0 7 to 0 6 ma marked by major turnovers in the relative abundances of species coinciding with an increased amplitude of glacial cycles these cycles appear to have influenced low latitude monsoonal climate as well as deep sea conditions in the central indian ocean basin

geochemistry of diverse basalt types from loihi seamount hawaii petrogenetic implications the wide variety of basalt types tholeiitic to basanite dredged from loihi seamount have minor and trace element abundances that are characteristic of subaerial hawaiian basalts thereby confirming that loihi seamount is a manifestation of the hawaiian hot spot within the loihi sample suite there are well defined positive correlations among abundances of highly incompatible elements p k rb ba nb light ree and ta and moderately incompatible elements sr ti zr and hf and between mgo ni and cr however within the loihi suite abundance ratios of geochemically similar elements zr hf nb ta and la ce vary by factors of 1 2 1 5 and abundance ratios of highly incompatible elements such as p ce p th k rb ba th and la nb vary by factors of 1 2 2 5 these abundance ratios are not readily changed by different degrees of fractionation and melting therefore we conclude that these samples are not genetically related by different degrees of melting of a compositionally homogeneous source on the basis of k p k ti p ce zr nb th p and la sm abundance ratios the twelve samples studied in detail can be divided into six geochemical groups samples within each group are similar in 87sr 86sr 1 and intra group compositional variations may reflect low pressure fractionation and different degrees of melting in addition crossing chondrite normalized ree patterns within the alkalic basalt groups reflect equilibration of the magmas with garnet in ratio ratio plots involving abundance ratios of highly incompatible elements e g la p nb p k p rb p ba p and th p the geochemical groups define linear arrays suggestive of mixing however these data combined with the isotopic data are not consistent with two component mixing

late early oligocene deep sea benthic foraminifera and their faunal response to paleoceanographic changes in the eastern equatorial pacific abstract we documented new data on the late early oligocene benthic foraminifera and sediment geochemistry in the eastern equatorial pacific ocean eep from integrated ocean drilling program exp 320 site u1334 paleo water depth 3650 to 3850 m with some published data on those from ocean drilling program leg 199 sites 1218 3850 to 4000 m and 1219 4270 to 4370 m in order to understand the response of abyssal benthic foraminifera to paleoceanographic conditions during the interval 32 28 ma the relative abundances of nuttallides umbonifer were distinctly different between sites 1218 and 1219 during 31 0 to 29 9 ma although other major taxa e g globocassidulina subglobosa cibicidoides spp and oridorsalis umbonatus showed no marked changes the characteristics e g shannon wiener h of the benthic foraminiferal fauna are affected by the abundance of a few dominant species rather than by the change in the number of species in the eep based on multi dimensional scaling mds two mds axes were recognized mds axis 1 characteristic taxa n umbonifer and cibicidoides sp a and mds axis 2 characteristic taxa g subglobosa and bolivina huneri the tendency of both mds axes 1 and 2 showed a distinct depth gradient among the three sites after 28 6 ma whereas the tendency was different from 31 0 to 28 6 ma especially at site 1218 increased abundance of n umbonifer in the eep after 29 ma was similar to that in the atlantic ocean after the expanded distribution of this species to shallower depths was finished the faunal change at 28 6 ma might be related to the change of deep water circulation possibly with the influences of the southern component water scw and or northern component water in the south atlantic ocean in contrast the faunal change at 31 0 ma might be related to the formation of the scw and or meridional overturning circulation in the southern ocean in particular mds axis 1 exhibited the opposite tendency between sites 1218 and 1219 around the oi 2 event whereas the depth gradient was clearly observed among the sites around the oi 2 event the opposite tendency of mds axis 1 around the oi 2 event might be explained by the varying influences of the scw on different depths of the eep especially in terms of carbonate undersaturation the influence of the scw on benthic foraminifera in the eep was different among the depths of the three sites in the oi 2 event however the depth gradient of the scw influence was gradually intensified in the oi 2 event and the 28 6 28 0 ma interval

factors influencing the distribution of subantarctic deep sea benthic foraminifera campbell and bounty plateaux new zealand abstract we investigate the combination of environmental factors that influence the distribution patterns of benthic foraminiferal tests 63 m in a topographically varied region crossed by both the subtropical and subantarctic fronts south east of new zealand seafloor sample sites extending from outer shelf 50 m to abyssal 5000 m depths are bathed by five different water masses and receive phytodetritus from subtropical subantarctic and circumpolar surface water masses eight mappable associations are recognised by q mode cluster analysis of the benthic foraminiferal census data similar associations are identified using cluster analysis based solely on the presence or absence of species canonical correspondence analysis and a correlation coefficient matrix were used to relate the faunal data to a set of environmental proxies these show that factors related to water depth especially decreasing food supply with increasing depth are the most significant in determining the overall foraminiferal distribution other contributing factors include surface water productivity and its seasonality bottom water ventilation energetic state of the benthic boundary layer and resulting substrate texture and bottom water carbonate corrosiveness three shallow water associations 50 700 m dominated by cassidulina carinata trifarina angulosa globocassidulina canalisuturata gavelinopsis praegeri and bolivina robusta occur in coarse substrates on the continental shelf and on the crests and upper slopes of four seamounts under well oxygenated high energy regimes and high food input three mid bathyal to upper abyssal associations 500 3300 m dominated by alabaminella weddellensis c carinata and epistominella exigua occur in biopelagic sandy mud beneath a region of strongly seasonal food supply with their composition influenced by total food flux ventilation oxygen minimum zone and bottom current strength an unusual lower bathyal association 1200 2100 m dominated by t angulosa and ehrenbergina glabra occurs in a belt of coarser sandy substrate that runs along the crest of the submarine plateaux slopes beneath the strongly flowing subantarctic front related currents a deep abyssal association 3500 5000 m dominated by nuttallides umbonifer and globocassidulina subglobosa occurs on the abyssal plain beneath oligotrophic lower circumpolar water south east of the subantarctic front and is strongly influenced by the cold carbonate corrosive conditions the faunal composition of this subantarctic region is most similar to adjacent southern new zealand but with the addition of a few significant antarctic elements e g e glabra globocassidulina crassa

equatorial pacific productivity changes near the eocene oligocene boundary there is general agreement that productivity in high latitudes increased in the late eocene and remained high in the early oligocene evidence for both increased and decreased productivity across the eocene oligocene transition eot in the tropics has been presented usually based on only one paleoproductivity proxy and often in sites with incomplete recovery of the eot itself a complete record of the eocene oligocene transition was obtained at three drill sites in the eastern equatorial pacific ocean odp site 1218 and iodp sites u1333 and u1334 four paleoproductivity proxies that have been examined at these sites together with carbon and oxygen isotope measurements on early oligocene planktonic foraminifera give evidence of ecologic and oceanographic change across this climatically important boundary export productivity dropped sharply in the basal oligocene 33 7 ma and only recovered several hundred thousand years later however overall paleoproductivity in the early oligocene never reached the average levels found in the late eocene and in more modern times changes in the isotopic gradients between deep and shallow living planktonic foraminifera suggest a gradual shoaling of the thermocline through the early oligocene that on average affected accumulation rates of barite benthic foraminifera and opal as well as diatom abundance near 33 5 ma an interval with abundant large diatoms beginning at 33 3 ma suggests an intermediate thermocline depth which was followed by further shoaling a dominance of smaller diatoms and an increase in average primary productivity as estimated from accumulation rates of benthic foraminifera

last glacial maximum paleoproductivity and water masses off nw africa evidence from benthic foraminifera and stable isotopes abstract last glacial maximum lgm paleoproductivity organic carbon c org fluxes and seasonality was reconstructed from benthic foraminiferal faunas and the stable carbon and oxygen isotopes of foraminiferal calcite sediments of the lgm between 23 000 to 19 000 cal yr bp of sixteen cores from the upwelling region off morocco between cape ghir 31 n and cape yubi 27 5 n were investigated four regions with distinct paleo c org fluxes and seasonality were reconstructed based on faunal assemblages and 13 c values of hoeglundina elegans 1 the cape yubi upwelling region with high paleoproductivity high paleo c org fluxes and very low seasonality as indicated by the bolivina albatrossi uvigerina mediterranea assemblage and lowest mean 13 c h elegans 2 the cape ghir upwelling region with moderate to high paleoproductivity and paleo c org fluxes and low seasonality as indicated by the bulimina mexicana gavelinopsis translucens assemblage and low mean 13 c h elegans 3 the cape yubi filament region with moderate to high paleoproductivity high paleo c org fluxes and high seasonality as indicated by the cassidulina laevigata nonionella iridea assemblage and 13 c h elegans as low as those from the cape ghir upwelling region 4 the cape ghir filament region with highest paleoproductivity high paleo c org fluxes and seasonality as indicated by the epistominella exigua assemblage and highest 13 c h elegans productivities during the lgm and today were compared based on faunal assemblages and 13 c values 13 c 13 c lgm 13 c present of three infaunal species generally during the lgm the upwelling region was characterized by higher paleo c org fluxes particularly in the area between the capes similar seasonality along the coast and higher seasonality further offshore than at present day for the reconstruction of lgm water mass stratification we used the 13 c of cibicidoides wuellerstorfi and equilibrium adjusted 18 o of several species deep water mass stratification is characterized by glacial north atlantic central water above 800 m by glacial mediterranean outflow water between 800 and 1900 m and glacial north atlantic deep water below 1900 m and a southern source deep water mass this means considering the lowered glacial sea level water mass stratification during the lgm was similar to present day conditions

observations of manganese and iron at the coaxial seafloor eruption site juan de fuca ridge magmatic injection during june july 1993 on the coaxial segment of the juan de fuca ridge resulted in an axial lava eruption an overlying chronic style hydrothermal plume and at least three megaplume like event plumes a comprehensive view of mn and fe liberated as hydrothermal discharge during this volcano hydrothermal event was obtained as part of a rapid field response that included continuous in situ measurements of mn and fe distribution maps for mn fe and temperature anomaly within the chronic and event plumes reveal significant thermochemical diversity that we ascribe to variable extraction efficiencies for heat and metals by source fluids and to plume age differences the mn heat data suggest that diffuse fluids could be the primary source of the chronic plume at northern coaxial segment but make only a minor contribution to event plumes measurements of ephemeral fe ii were used to estimate that the event plumes were 2 4 and 6 8 days old when first sampled corresponding to formation times during peak seismic activity the inventories of mn and fe within the three coaxial event plumes were similar to values previously reported for megaplumes

euro north african sirenia biodiversity as a response to climate variations abstract earth has a latitudinal biodiversity gradient in which more species inhabit tropical than polar regions frequently attributed to seasonality this ecological pattern is applied to the evolution of the euro north african sirenians and its relation to cenozoic climate change climate disruption changes in seasonality and geological processes such as sea level variations are statistically tested as primary drivers to explain sirenian evolution and regional amphi mediterranean sirenian speciation and biodiversity

last global extinction in the deep sea during the mid pleistocene climate transition 1 twenty percent 19 genera 95 species of cosmopolitan deep sea 500 4000 m benthic foraminiferal species became extinct during the late pliocene middle pleistocene 3 0 12 ma with the peak of extinctions 76 species occurring during the mid pleistocene climate transition mpt 1 2 0 55 ma one whole family stilostomellidae 30 species was wiped out and a second pleurostomellidae 29 species was decimated with just one species possibly surviving through to the present our studies at 21 deep sea core sites show widespread pulsed declines in abundance and diversity of the extinction group species during more extreme glacials with partial interglacial recoveries these declines started in the late pliocene in southern sourced deep water masses antarctic bottom water circumpolar deep water and extending into intermediate waters antarctic intermediate water north atlantic deep water in the mpt with the youngest declines in sites farthest downstream from high latitude source areas for intermediate waters we infer that the unusual apertural types that were targeted by this extinction period were adaptations for a specific kind of food source and that it was probably the demise of this microbial food that resulted in the foraminiferal extinctions we hypothesize that it may have been increased cold and oxygenation of the southern sourced deep water masses that impacted on this deep water microbial food source during major late pliocene and early pleistocene glacials when antarctic ice was substantially expanded the food source in intermediate water was not impacted until major glacials in the mpt when there were significant expansion of polar sea ice in both hemispheres and major changes in the source areas temperature and oxygenation of global intermediate waters

benthic foraminiferal biodiversity response to a changing arctic palaeoclimate in the last 24 000 years investigations on the benthic foraminiferal fauna of sediment cores from the eurasian basin arctic ocean continental margin reveal well correlated biodiversity maxima and minima during the last 24 kyrs the temporal variable biodiversities observed at the core sites on a large scale reflect the palaeoclimatic evolution of the high northern latitudes herein sediments deposited during interglacials and interstadials reveal highest species richness whereas glacials and stadials are documented by lower species numbers in high resolution core ps2837 different periodicities in species richness in sediments from the late weichselian and holocene can be detected biodiversity periodicities of 1 57 kyrs and 0 76 kyrs characterize sediments of the late weichselian whereas with the retreat of glacial ice sheets and shorter seasonal ice coverage holocene sediments reveal shorter periodicities of 1 16 kyrs and 0 54 kyrs with the establishment of modern hydrographic conditions at about 4000 bp 4 kyrs a significant increase in the amplitudes of species richness can be observed although sediments deposited during warmings reveal highest species richness we doubt that water temperature determines the abundance and distribution of most benthic foraminifera in the arctic ocean we rather suggest that the temporal variabilities in species richness reflect changes in the availability of food which in the arctic ocean mainly depends on extend and duration of seasonal sea ice retreat in the study area the latter one besides the seasonal varying insolation is essentially determined by the advection rates and temperature of atlantic water entering the arctic ocean via the west spitsbergen current because both flowrate and temperature of the west spitsbergen current were increased during interstadials and interglacials a predominantly indirect influence of palaeotemperature on the biodiversity of benthic foraminifera is suggested yet rare species like atlantic species may indeed have a temperature sensitive metabolism 2007 elsevier b v all rights reserved

global deep sea extinctions during the pleistocene ice ages the dark near freezing environment of the deep oceans is regarded as one of the most stable habitats on earth and this stability is generally reflected in the slow turnover rates extinctions and appearances of the organisms that live there by far the best fossil record of deep sea organisms is provided by the shells of benthic foraminifera protista a little known global extinction of deep sea benthic foraminifera occurred during the pleistocene ice ages in the southwest pacific it caused the disappearance of at least two families 15 genera and 48 species 15 25 of the fauna of dominantly uniserial elongate foraminifera with distinctive apertural modifications these forms progressively died back and became extinct during glacial periods in the late pliocene to middle pleistocene ca 2 5 0 6 ma most extinctions occurred between 1 0 and 0 6 ma at the time of the middle pleistocene climatic revolution this first high resolution study of this extinction event indicates that it was far more significant for deep sea diversity loss than previously reported 10 species the middle pleistocene extinction was the most dramatic last phase of a worldwide decline in the abundance of these elongate forms a phase that began during cooling near the eocene oligocene boundary and continued during the middle miocene clearly these taxa declined when the world cooled but the reason is yet to be resolved

south equatorial current sec driven changes at dsdp site 237 central indian ocean during the plio pleistocene evidence from benthic foraminifera and stable isotopes abstract this study attempts to analyse paleoceanographic changes in the central indian ocean deep sea drilling project site 237 linked to monsoon variability as well as deep sea circulation during the plio pleistocene we used factor and cluster analyses of census data of the 34 most dominant species of benthic foraminifera that enabled us to identify five biofacies astrononion umbilicatulum uvigerina proboscidea au up pullenia bulloides bulimina striata pb bs globocassidulina tumida nuttallides umbonifera gt nu gyroidinoides nitidula cibicides wuellerstorfi gn cw and cassidulina carinata cassidulina laevigata cc cl biofacies knowledge of the environmental preferences of modern deep sea benthic foraminifera helped to interpret the results of factor and cluster analyses in combination with oxygen and carbon isotope values the biofacies indicative of high surface productivity resulting from a stronger south equatorial current au up and pb bs biofacies dominate the early pliocene interval 5 6 4 5 ma of global warmth an intense indo pacific biogenic bloom and strong oxygen minimum zone extended to intermediate depths 1000 2000 m over large parts of the indian ocean in the early pliocene since 4 5 ma the food supply in the central indian ocean dropped and fluctuated while deep waters were corrosive biofacies gt nu gn cw the pleistocene interval is characterized by an intermediate flux of organic matter cc cl biofacies

paleoproductivity increase at the eocene oligocene climatic transition odp dsdp sites 763 and 592 abstract during the late eocene early oligocene period of rapid climate change across oxygen isotope shift oi 1 productivity showed major changes in the region around australia dsdp site 592 off new zealand odp site 763 off nw australia we estimated paleoproductivity at these sites using benthic foraminiferal accumulation rates as well as accumulation rates of siliceous and other calcareous microfossils and carbon isotope data in the eocene productivity was generally higher at site 763 where it reached 4 maxima but dropped at about 34 3 ma at both sites productivity increased strongly at oi 1 as recognized in the oxygen isotopic record at the sites and fluctuted during the early oligocene at higher levels than in the eocene we attribute the difference in eocene productivity to differences in oceanographic settings site 592 was probably under a n s flowing western boundary current of the pacific gyre whereas site 763 showed periodic high productivity as a result of local upwelling this upwelling occurred when a warm n s flowing current proto leeuwin current replaced the cold s n flowing eastern boundary current of the indian ocean gyre upwelling ended at the opening of the tasman sea the earliest oligocene increase in productivity occurred at many other locations in the southern oceans and is accompanied by a strong increase in carbon isotopic values indicating increased burial of organic matter on a global scale this productivity increase as well as the increased burial indicates that the oceanic carbon cycle may have been part of the climate change in the earliest oligocene

benthic foraminiferal response to the middle eocene climatic optimum meco in the south eastern atlantic odp site 1263 the response of marine biota to the middle eocene climatic optimum meco is still poorly constrained specifically changes in deep sea benthic foraminiferal faunas have been documented at few locations only we carried out a quantitative study of benthic foraminiferal assemblages at lower bathyal odp site 1263 walvis ridge se atlantic providing documentation of the response of benthic foraminiferal assemblage to the meco in an open ocean setting there was no major temporary or persistent assemblage turnover in benthic foraminiferal faunas in the se atlantic ocean the benthic foraminiferal accumulation rates bfar and assemblage composition indicate that the delivery of food to the seafloor increased during the early stages of surface and deep sea warming during this period the absolute and relative abundance of phytodetritus exploiters increased pronouncedly indicating that the increase in the flux of organic matter to the sea floor was largely seasonal or otherwise pulsed during later stages and peak warming of meco in contrast the flux of organic matter to the seafloor declined markedly as shown by a decrease in both infaunal and epifaunal benthic foraminiferal accumulation rates the low flux of organic matter during the more extreme parts of the meco thus did not favor one of these broad groups but affected all common taxa paleoceanographic reconstructions combined with data on benthic foraminifera suggest that the meco warming was the main cause of the reduction in the flux of organic matter to the sea floor by increasing the metabolic rates of pelagic consumers which thus used more food preventing it from reaching the sea floor as well as increasing remineralization of organic matter in the water column

cenozoic deep sea benthic foraminifers tracers for changes in oceanic productivity from late middle eocene through earliest oligocene high latitude regions cooled and by the end of the period continental ice sheets existed in antarctica diversity of planktonic microorganisms declined and modern groups of terrestrial vertebrates originated coeval faunal changes in deep sea benthic foraminifers have been related to cooling of deep waters and increased oxygenation cooling however occurred globally whereas species richness declined at high latitudes and not in the tropics the late eocene and younger lower diversity high latitude faunas typically contain common epistominella exigua and alabaminella weddellensis opportunistic phytodetritus exploiting species that indicate a seasonally fluctuating input of organic matter to the sea floor we speculate that the species richness gradient and increase in abundance of phytodetritus exploiting species resulted largely from the onset of a more unpredictable and seasonally fluctuating food supply especially at high latitudes

contrasting glacial interglacial regimes in the western arctic ocean as exemplified by a sedimentary record from the mendeleev ridge distinct cyclicity in lithology and microfaunal distribution in sediment cores from the mendeleev ridge in the western arctic ocean water depths ca 1 5 km reflects contrasting glacial interglacial sedimentary patterns we conclude that during major glaciations extremely thick pack ice or ice shelves covered the western arctic ocean and its circulation was restricted in comparison with interglacial modern type conditions glacier collapse events are marked in sediment cores by increased contents of ice rafted debris notably by spikes of detrital carbonates and iron oxide grains from the canadian arctic archipelago composition of foraminiferal calcite n 18 o and n 13 c also shows strong cyclicity indicating changes in freshwater balance and or ventilation rates of the arctic ocean light stable isotopic spikes characterize deglacial events such as the last deglaciation at ca 12 14 c kyr bp the prolonged period with low n 18 o and n 13 c values and elevated contents of iron oxide grains from the canadian archipelago in the lower part of the mendeleev ridge record is interpreted to signify the pooling of freshwater in the amerasia basin possibly in relation to an extended glaciation in arctic north america unique benthic foraminiferal events provide a means for an independent stratigraphic correlation of sedimentary records from the mendeleev ridge and other mid depth locations throughout the arctic ocean such as the northwind and lomonosov ridges this correlation demonstrates the disparity of existing age models and underscores the need to establish a definitive chronostratigraphy for arctic ocean sediments 2003 elsevier b v all rights reserved

a 370 ka paleoceanographic record from the hess rise central north pacific ocean and an indistinct kuroshio extension abstract a 5 m long core np36 collected from the hess rise in the central north pacific ocean 34 11 7 n 179 15 4 e water depth 2664 m was analyzed for benthic and planktonic foraminifera this core yields a continuous record for the last ca 370 000 years according to the oxygen isotope stratigraphy cross spectral analysis of down core variations in planktonic 18o values correlates well with the specmap reference scale allowing recognition of marine isotope stages mis down to mis 10 and the 18o variations coincide well with the changes in sea surface temperature derived using the modern analogue technique time series analyses of mass accumulation rates mar of planktonic and benthic foraminifera were also performed along with analysis of variations in faunal composition mar of planktonic foraminifera display maxima during glacial periods which together with coincident changes in lightness l of sediment measured with the spectrophotometer strongly suggests increasing flux of eolian dust to the hess rise due to strengthened westerly winds however mar of benthic foraminifera including epistominella exigua a common typical phytodetritus feeder also display highest increases during some interglacial periods i e mis 5 and 7 the benthic mar maxima are thought to reflect variations in consumption patterns between benthic and planktonic species a proposed hypothesis that vigorous grazing of phytoplanktons occurred during glacial periods reducing the flux of phytodetritus to the sea floor in turn impacting and limiting production of benthic foraminifera with the opposite effect prevailing during interglacial periods down core variations in right coiling neogloboquadrina pachyderma abundance and the composition of planktonic foraminiferal faunas indicate the subarctic front did not shift southward over the study site during the past 370 000 years alternatively variations in faunal composition indicate that subtropical water prevailed in the study area throughout this period no clear faunal evidence of the presence of the kuroshio extension was found in core np36 reflecting the loss of heat and tropical faunal elements from this water mass as it flowed eastward during late quaternary climatic maxima and minima

patterns of export production in the eastern equatorial pacific over the past 130 000 years 1 productivity at six core locations in the eastern equatorial pacific eep was reconstructed with a benthic foraminiferal transfer function the core records show strong regionality especially where affected by peru margin upwelling of deeper equatorial undercurrent water euc originally coming from the subantarctic this peru margin record differs from that seen along the equator where divergence leads to shallow upwelling and it is generally inverse to that seen in cores outside the areas of equatorial upwelling principal components analysis shows that the main productivity pattern correlates well to the global oxygen isotope record and has lowest values during isotope stages 2 and 4 in addition to this equatorial cores show a higher frequency pattern of variation which becomes much more pronounced during mis 3 and 2 the reconstructions based on benthic foraminifera were tested against those from nonaccumulation rate based inorganic chemical proxies of export production these were found to correlate well in the region influenced by peru upwelling and also to share common features for sites along the equator all the nonaccumulation rate based paleotracers are consistent with one another and differ from accumulation rate derived proxies the differences between the two classes of paleotracers may result from uncertainties in calculating actual biogenic fluxes since 230th normalized results conform more to those we obtained analysis of planktonic carbon isotope values for the eep and their comparison to the record of the pacific subantarctic indicates that the subantarctic contribution to the euc was reduced during mis 3 and 2

glacial interglacial variations in sediment organic carbon accumulation and benthic foraminiferal assemblages on the bermuda rise odp site 1063 during mis 13 to 10 glacial times organic d 13 c values are less negative during mis 12 and mis 10 than during mis 11 which is consistent with greater glacial stage marine productivity high relative abundances of oridorsalis umbonatus during glacial intervals probably records a low but sustained flux of highly degraded organic material large recurrent fluctuations in the abundance of epistominella exigua at the beginnings of the mis 12 and mis 10 glaciations suggest a marked increase in local phytoplankton blooms at these times and consequent delivery of phytodetritus to the seafloor the most likely causes of these variations are changes in the position and strength of the gulf stream and its associated cold ring eddies combined with increased advection of terrigenous sediments from northerly locations during glacial lowstands

evolution of cenozoic seaways in the circum antarctic region abstract a complete circum antarctic seaway did not open until both the south tasman rise cleared the oates land coast of east antarctica and drake passage opened between the southern tip of south america and the northern end of the antarctic peninsula major plate motions based on dated seafloor spreading anomalies and distinct fracture zone lineations constrain the age of the opening of a seaway between the south tasman rise and antarctica as very close to the eocene oligocene boundary with an unrestricted opening deeper than 2000 m dating from 32 ma timing of the opening of drake passage is more circumstantial because the exact motions of certain micro continental fragments are not known the motion of africa with respect to south america as well as the motion of east antarctica with respect to africa are well constrained for the cenozoic these major plate motions are used with the reasonable assumption of no cenozoic motion of the antarctic peninsula with respect to east antarctica to constrain the location of the antarctic peninsula with respect to the southern tip of south america for the critical period of late eocene to late oligocene uncertainty of motion of the south georgia and south orkney microcontinents and other possible continental fragments make an exact time for opening of drake passage difficult to ascertain even so the early oligocene position of the antarctic peninsula with respect to south america requires a through going deep water seaway to have been open at drake passage prior to 28 ma even given the unconstrained motion of various high standing crustal fragments in the scotia sea with reasonable assumptions concerning motion of the crustal fragments in the western and central scotia sea it is likely that drake passage or passage through powell basin was open to deep water circulation by 31 2 ma

benthic foraminifera and the late quaternary last 150 ka paleoceanographic and sedimentary history of the bounty trough east of new zealand abstract the bounty trough east of new zealand lies along the southeastern edge of the present day subtropical front stf and is a major conduit via the bounty channel for terrigenous sediment supply from the uplifted southern alps to the abyssal bounty fan census data on 65 benthic foraminiferal faunas 63 m from upper bathyal odp 1119 lower bathyal dsdp 594 and abyssal odp 1122 sequences test and refine existing models for the paleoceanographic and sedimentary history of the trough through the last 150 ka marine isotope stages mis 6 1 cluster analysis allows recognition of six species groups whose distribution patterns coincide with bathymetry the climate cycles and displaced turbidite beds detrended canonical correspondence analysis and comparisons with modern faunal patterns suggest that the groups are most strongly influenced by food supply organic carbon flux and to a lesser extent by bottom water oxygen and factors relating to sediment type major faunal changes at upper bathyal depths 1119 probably resulted from cycles of counter intuitive seaward landward migrations of the southland front sf north south sector of the stf benthic foraminiferal changes suggest that lower nutrient cool subantarctic surface water saw was overhead in warm intervals and higher nutrient bearing warm neritic subtropical surface water stw was overhead in cold intervals at lower bathyal depths 594 foraminiferal changes indicate increased glacial productivity and lowered bottom oxygen attributed to increased upwelling and inflow of cold nutrient rich antarctic intermediate water aaiw and shallowing of the oxygen minimum zone upper circum polar deep water cpdw the observed cyclical benthic foraminiferal changes are not a result of associations migrating up and down the slope as glacial faunas dominated by globocassidulina canalisuturata and eilohedra levicula at upper and lower bathyal depths respectively are markedly different from those currently living in the bounty trough on the abyssal bounty fan 1122 faunal changes correlate most strongly with grain size and are attributed to varying amounts of mixing of displaced and in situ faunas most of the displaced foraminifera in turbiditic sand beds are sourced from mid outer shelf depths at the head of the bounty channel turbidity currents were more prevalent during but not restricted to glacial intervals

benthic foraminiferal response to sea level change in the mixed siliciclastic carbonate system of southern ashmore trough gulf of papua 1 ashmore trough in the western gulf of papua gop represents an outstanding modern example of a tropical mixed siliciclastic carbonate depositional system where significant masses of both river borne silicates and bank derived neritic carbonates accumulate in this study we examine how benthic foraminiferal populations within ashmore trough vary in response to sea level driven paleoenvironmental changes particularly organic matter and sediment supply two 11 3 m long piston cores and a trigger core were collected from the slope of ashmore trough and dated using radiocarbon and oxygen isotope measurements of planktic foraminifera relative abundances principal component analyses and cluster analyses of benthic foraminiferal assemblages in sediment samples identify three distinct assemblages whose proportions changed over time assemblage 1 with high abundances of uvigerina peregrina and bolivina robusta dominated between 83 and 70 ka early regression assemblage 2 with high abundances of globocassidulina subglobosa dominated between 70 and 11 ka late regression through lowstand and early transgression and assemblage 3 with high abundances of neritic benthic species such as planorbulina mediterranensis dominated from 11 ka to the present late transgression through early highstand assemblage 1 represents heightened organic carbon flux or lowered bottom water oxygen concentration and corresponds to a time of maximum siliciclastic fluxes to the slope with falling sea level assemblage 2 reflects lowered organic carbon flux or elevated bottom water oxygen concentration and corresponds to an interval of lowered siliciclastic fluxes to the slope due to sediment bypass during sea level lowstand assemblage 3 signals increased off shelf delivery of neritic carbonates likely when carbonate productivity on the outer shelf great barrier reef increased significantly when it was reflooded benthic foraminiferal assemblages in the sediment sink slopes of ashmore trough likely respond to the amount and type of sediment supplied from the proximal source outer gop shelf

deep sea benthic foraminiferal turnover during the early middle eocene transition at walvis ridge se atlantic abstract the early middle eocene transition emet 51 47 ma was a pivotal time in cenozoic global climate development encompassing the end of the early eocene climate optimum eeco and the start of high latitude cooling culminating in the early oligocene glacial maximum 34 33 ma we studied benthic foraminiferal assemblages and stable isotopes at upper abyssal site 1263 paleodepth 1800 m and lower abyssal site 1267 paleodepth 3500 m on walvis ridge se atlantic across the emet benthic 18 o values at both sites rose from 49 7 ma on becoming slightly higher at the shallower site than at the deeper site from 44 ma on benthic 13 c values show a broad maximum at 49 48 ma benthic foraminiferal assemblages at both sites are dominated by calcareous taxa particularly nuttallides truempyi indicative of oligotrophic conditions large species of bulimina indicative of more food rich conditions were less rare at the shallower site where benthic foraminiferal accumulation rates were generally higher specimens intermediate in morphology between n truempyi a cosmopolitan warm water species which died out in the latest eocene and its extant also cosmopolitan cold water descendant nuttallides umbonifera indicative of corrosive bottom waters are present as well as various epistominella species indicative of seasonal delivery of phytodetritus to the sea floor and globally more common after the eocene oligocene transition these assemblages indicate that deep water environments started a gradual evolution from conditions typical for the warm early eocene greenhouse to those typical for icehouse conditions by the end of the early eocene characteristic early eocene species such as aragonia aragonensis and quadrimorphina profunda persisted at least until 48 ma the end of the studied interval at the deeper site whereas at the shallower site they had their last appearances at 49 7 ma the time of increase in 18 o values i e high latitude and deep water cooling the benthic foraminiferal transition towards assemblages typical for a glaciated world thus started close to the end of the early eocene in the se atlantic with the middle eocene already representing a transitional world the faunal changes in the se atlantic began earlier at upper abyssal than at lower abyssal depths this suggests that a more stratified ocean started to develop in the se atlantic at the end of the eeco possibly due to changes in source regions of intermediate water masses due to polar cooling and or circulation changes around the antarctic continent

environmental perturbation in the southern tethys across the paleocene eocene boundary dababiya egypt foraminiferal and clay mineral records foraminiferal and clay mineral records were studied in the upper paleocene to lower eocene dababiya section egypt this section hosts the gssp for the paleocene eocene boundary and as such provides an expanded and relatively continuous record across the paleocene eocene thermal maximum petm deposition of illite smectite clay minerals is interpreted as a result of warm and arid conditions in the southern tethys during the latest paleocene benthic foraminiferal assemblages are indicative of seasonal variation of oxygen and food levels at the seafloor a sea level fall occurred in the latest paleocene followed by a rise in the earliest eocene foraminiferal diversity and densities decreased strongly at the p e boundary coinciding with the level of global extinction of benthic foraminifera bee and start of the carbon isotope excursion cie and petm in the lower cie the seafloor of the stratified basin remained nearly permanently anoxic and azoic a sudden increase in mixed clay minerals kaolinite and others suggests that warm and perennial humid conditions prevailed on the continent high levels of toc and phosphathic concretions in the middle cie are evidence for increased organic fluxes to the sea floor related to upwelling and to augmented continental runoff low densities of opportunistic taxa appeared indicating occasional ephemeral oxygenation and repopulation of the benthic environment the planktic community diversified although conditions remained poor for deep dwelling taxa an increase in illite smectite dominated clay association is considered to mark the return of a seasonal signature on climatic conditions during the late cie environmental conditions changed to seasonally fluctuating mesotrophic conditions and diverse and rich benthic and planktic foraminiferal communities developed post cie planktic faunas consisted of both deep and shallow dwelling taxa and buliminid dominated benthic assemblages reflect fluctuating mesotrophic conditions the frequent environmental perturbations during the cie petm at dababiya provided a rather specialized group of foraminiferal taxa i e anomalinoides aegyptiacus the opportunity to repopulate survive and subsequently dominate by a hypothesized capacity to switch to an alternative life strategy population dynamics habitat shift or different metabolic pathway the faunal record of dababiya provides insight into the cause and development of the bee various severe global changes during the petm e g ocean circulation caco3 dissolution productivity and temperature changes disturbed a wide range of environments on a geologically brief timescale explaining together the geographically and temporally variable character of the bee this allowed a number of specific but different foraminiferal assemblages composed of stress tolerant and opportunistic taxa to be successful during and after the periods of environmental perturbations associated with the petm

paleoceanography of the southern agulhas plateau during the last 150 ka inferences from benthic foraminiferal assemblages and multispecies epifaunal carbon isotopes benthic foraminiferal assemblages and the carbon isotope composition of the epifaunal benthic foraminifera epistominella exigua and fontbotia wuellerstorfi have been investigated along core md02 2589 located at the southern agulhas plateau 41 26 03 s 25 15 30 e 2660 m water depth this study aims to evaluate changes in the benthic paleoenvironment and its influence on benthic 13c with a notable focus on e exigua a species associated with phytodetritus deposits and poorly studied in isotope paleoceanographic reconstructions the benthic foraminiferal assemblages 63 m show large fluctuations in species composition suggesting significant changes in the pattern of ocean surface productivity conceivably related to migrations of the subtropical convergence stc and subantarctic front saf low to moderate seasonality and relatively higher food supply to the seafloor are indicated during glacial marine isotope stages mis 6 4 and 2 and during mis 3 probably associated with the northward migration of the saf and confluence with the more stationary stc above the southern flank of the agulhas plateau the lowest organic carbon supply to the seafloor is indicated from late mis 5b to mis 4 as a consequence of increased influence of the agulhas front af and or weakening of the influence of the stc over the region episodic delivery of fresh organic matter similar to modern conditions at the core location is indicated during mis 5c mis 5e and at termination i comparison of this paleoenvironmental information with the paired 13c records of e exigua and f wuellerstorfi suggests that organic carbon offsets 13c of e exigua from ambient bottom water 13cdic while its 13c amplitude on glacial interglacial timescales does not seem affected by changes of organic carbon supply to the seafloor this suggests that this species calcifies preferentially during the short time span of the year when productivity peaks and phytodetritus is delivered to the seafloor therefore e exigua while offset from 13cdic potentially more faithfully records the amplitude of ambient bottom water 13cdic changes than f wuellerstorfi notably in settings such as the southern ocean that experienced substantial changes through time in the organic carbon supply to the seafloor

two abyssal sites in the southern ocean influenced by different organic matter inputs environmental characterization and preliminary observations on the benthic foraminifera abstract the abundance and diversity of the deep sea benthos are intimately linked to inputs of organic matter from the euphotic zone however it is often difficult to isolate the influence of surface productivity on benthic ecosystems from other environmental factors to this end two abyssal sites 4200 m water depth located under contrasting productivity regimes around the crozet plateau in the indian ocean sector of the southern ocean were sampled during the austral summer of 2004 2005 one site m5 east of the crozet isles was located beneath an area where there was an enduring seasonal phytoplankton bloom the second site m6 was located in an oligotrophic high nutrient low chlorophyll hnlc region to the south of the islands organic fluxes to the seafloor at these sites are thought to reflect the overlying productivities so that the benthic environment to the east of the islands was more eutrophic than at the southerly station all other environmental variables were similar at the two sites which are located just 460 km apart the concentrations of chlorophyll a and total organic carbon in the surficial sediments were significantly greater at the relatively eutrophic site east of the islands m5 than at the southerly site m6 total nitrogen however was similar at both sites significantly higher phytopigment concentrations were observed in the surficial sediments at the eutrophic site in particular the concentration of chlorophyll a was 3 times greater than at the southern site although the freshness of the labile component as measured by chlorophyll a to pheophorbide ratio was not different between sites these results confirm that fluxes of organic matter to the seafloor were higher at the site located beneath the bloom region this was reflected in the abundance and diversity of live stained and dead benthic foraminifera 125 m which were greater at the eutrophic site the species composition of the dead foraminiferal assemblages were similar at both sites however and were dominated by nuttallides umbonifera pullenia bulloides and melonis pompiloides an exception was the phytodetritus species epistominella exigua which was more abundant at the eutrophic site indicating a larger seasonal component to the export under the bloom region differences in the organic matter input regimes at the two sites appear to influence the abundance and diversity but not the overall species composition of the foraminiferal assemblages

regional differences in pelagic productivity in the late eocene to early oligocene a comparison of southern high latitudes and lower latitudes paleoproductivity patterns at the eocene oligocene boundary in southern high latitudes and in the equatorial oceans were synthesized from the literature three odp dsdp sites from the southern ocean sites 689 748 and 511 were compared with three dsdp odp sites from the equatorial oceans sites 574 462 and 959 paleoproductivity was estimated by multiple sedimentological biological and geochemical proxies changes in paleoproductivity at the eocene oligocene boundary mainly took place in the southern high latitudes at site 689 the benthic foraminiferal fauna also indicates an increase in seasonality in equatorial oceans there are no indications for a shift to higher paleoproductivity at the eocene oligocene boundary on the contrary at site 959 sedimentology documents decreasing paleoproductivity in the oligocene major changes in temperature and ocean circulation in southern high latitudes versus only minor changes in the lower latitudes were probably responsible for the geographically different changes in paleoproductivity d 2004 elsevier b v all rights reserved

spiroplectinata key benthic foraminifer genus for palaeoceanographic reconstruction of the albian lower saxony basin abstract this paper is focused on albian spiroplectinata a morphologically unique benthic agglutinated foraminifer genus and its application for reconstructing changes in the water masses within the lower saxony basin a new interpretation of microhabitat preferences and feeding habit for spiroplectinata is proposed and discussed their functional morphology composition of their tests and their relationships with adherent foraminifera suggest that at least adult individuals of spiroplectinata were epibenthic and were either suspension or deposit feeders the suspension feeding mode is favoured because this genus is associated with adherent suspension feeding foraminifera and it does not correlate with other epibenthic deposit feeders spiroplectinata constructed an elongated uniserial terminal part which probably facilitated an erect position to spread a reticulopodium well above the sediment water interface the distribution of this foraminifer can therefore be used here as a sensitive indicator for the existence of bottom currents four or five periods of intensified bottom water circulation around the early middle albian boundary s 1 middle s 2 late middle to earliest late albian s 3 probably represents two intervals and early late albian s 4 are reconstructed and well marked by maxima of spiroplectinata annectens s complanata and spiroplectinata sp a s annectens is known from strata in the western tethys i e in the late aptian and early albian that are older than those in the boreal realm its first appearance in the lower saxony basin occurs in the late early albian followed by the first maximum just above the early middle albian boundary and probably represents the main immigration event into the lower saxony basin this supports the idea that the deep water in the late early to early late albian boreal epicontinental sea during the spiroplectinata intervals came from the tethys and not from the polar regions if one interprets the plankton benthos foraminifera ratio as reflecting sea level changes it implies that sea level rises may have been responsible for opening and or deepening of boreal tethyan gateways that activated extensive exchange of water masses this late early albian and early late albian invasion of tethyan water can be correlated with a general global warming and shifting of climate zones

relationship of benthic foraminiferal diversity to paleoproductivity in the neogene caribbean abstract diversity trends 8 3 2 5 ma in caribbean deep sea foraminifera as interpreted from the indices fisher s and the information index h s parallel paleoproductivity proxies benthic foraminiferal infaunal epifaunal species ratio benthic foraminifer accumulation rates and flux of organic carbon to the seafloor paleoproductivity never reached a eutrophic threshold value above which we would predict opposite trends of high paleoproductivity and low diversity consistent with stressful conditions instead results are similar to those from other studies of oligotrophic settings that show a positive and statistically significant correlation between paleoproductivity and diversity the correlations between current intensity and watermass oxygenation with diversity are negative and statistically significant these results are also borne out by principal component analysis pca intervals of increased relative abundance of epistominella exigua a proxy for seasonality of phytodetrital input to the seafloor coincide with increased diversity suggesting that pulsed paleoproductivity enhanced the diversity signal in the caribbean diversity and paleoproductivity peaked in the caribbean at 7 9 ma and declined thereafter due to the cut off of the nutrient rich pacific deep waters

bipolar atlantic deepwater circulation in the middle late eocene effects of southern ocean gateway openings we present evidence for antarctic circumpolar current acc like effects on atlantic deepwater circulation beginning in the late middle eocene modern ocean circulation is characterized by a thermal differentiation between southern ocean and north atlantic deepwater formation regions in order to better constrain the timing and nature of the initial thermal differentiation between northern component water ncw and southern component water scw we analyze benthic foraminiferal stable isotope 18obf and 13cbf records from ocean drilling program site 1053 upper deep water western north atlantic our data compared with published records and interpreted in the context of ocean circulation models indicate that progressive opening of southern ocean gateways and initiation of a circum antarctic current caused a transition to a modern like deep ocean circulation characterized by thermal differentiation between scw and ncw beginning 38 5 ma in the initial stages of drake passage opening in addition the relatively low 18obf values recorded at site 1053 show that the cooling trend of the middle late eocene was not global because it was not recorded in the north atlantic the timing of thermal differentiation shows that ncw contributed to ocean circulation by the late middle eocene 1 4 myr earlier than previously thought we propose that early ncw originated in the labrador sea based on tectonic reconstructions and changes in foraminiferal assemblages in this basin finally we link further development of meridional isotopic gradients in the atlantic and pacific in the late eocene with the tasman gateway deepening 34 ma and the consequent development of a circumpolar proto acc

early oligocene glaciation and productivity in the eastern equatorial pacific insights into global carbon cycling the onset of sustained antarctic glaciation across the eocene oligocene transition eot marks a pivotal change in earth s climate but our understanding of this event particularly the role of the

late oligocene miocene paleoceanographic evolution of the southeastern indian ocean evidence from deep sea benthic foraminifera odp site 757 abstract we quantitatively analyzed deep sea benthic foraminifera from 125 m size fraction from ocean drilling program odp site 757 to understand deep sea paleoceanographic changes in the southeastern indian ocean during the late oligocene miocene 26 5 5 35 ma we used the knowledge of the ecology of recent deep sea benthic foraminifera for environmental interpretations factor and cluster analyses were run using percentages of 46 highest ranked species that helped identify six biofacies defining six clusters of samples the faunal data document a major shift in deep sea ventilation organic carbon flux and productivity at 8 3 ma coinciding with the major intensification of the indian ocean monsoon system this marks a change from cold and well oxygenated deep waters with low and pulsed organic carbon flux during 26 5 to 8 3 ma to oxygen poor deep waters with sustained flux of organic matter from 15 0 to 7 6 ma the deep sea currents were stronger in the southeastern indian ocean probably due to major expansion of the east antarctic ice sheet and increased production of deep waters and in turn increased deep sea circulation the productivity increased in the indo pacific region in the late miocene and the modern monsoon regime probably established at 8 3 ma

living foraminiferal assemblages from the southern california margin a comparison of the 150 63 150 and 63 μm fractions abstract analyses of living rose bengal stained deep sea benthic foraminifera from three size fractions 150 m 63 150 m and both combined into the 63 m collected on the southern california margin reveal changes in foraminiferal assemblages that provide clues about the ecology of some species the top 5 cm of cores were examined from multicorer samples collected in may august and october 1996 at a 990 m water depth site within the southern california bight replicate cores at each site were not examined and results may be affected by spatial patchiness as well as seasonality calcareous foraminiferal abundances of the 63 150 m size fraction were highest during surface bloom months may and october and lowest in august while those of the 150 m size fraction remained relatively constant during the study small specimens probably representing young individuals in the 63 150 m fraction and larger specimens older individuals in the 150 m fraction of most large species live in overlapping microhabitats older individuals were found slightly deeper in the sediment than younger individuals of some species such as uvigerina peregrina and bolivina spissa most species of foraminifera at the study site increase in abundance in one or both of the bloom months of may and october nonionella fragilis appears to be an opportunistic species that takes rapid advantage of fresh phytodetritus increasing in abundance only during may and october as a result n fragilis may be a useful paleoseasonality indicator other taxa that appear to prefer fresh phytodetritus include u peregrina b spissa and bolivina pacifica the deep infaunal species globobulimina pacifica instead increases in abundance only during august no surface bloom these results provide important clues about the ecology of benthic foraminifera in dysoxic organic rich continental margins

an oblique slant on deep sea biodiversity organisms at the bottom of the deep seas might seem to be immune from large scale shifts in climate not so according to a study which reveals links between benthic biodiversity glaciation and the earth s obliquity

abrupt climate change and collapse of deep sea ecosystems we investigated the deep sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20 000 years in a core from intermediate depth in the northwestern atlantic results show that deep sea benthic community collapses occur with faunal turnover of up to 50 during major climatically driven oceanographic changes species diversity as measured by the shannon wiener index falls from 3 to as low as 1 6 during these events major disruptions in the benthic communities commenced with heinrich event 1 the inter allerod cold period iacp 13 1 ka the younger dryas yd 12 9 11 5 ka and several holocene bond events when changes in deep water circulation occurred the largest collapse is associated with the yd iacp and is characterized by an abrupt two step decrease in both the upper north atlantic deep water assemblage and species diversity at 13 1 ka and at 12 2 ka the ostracode fauna at this site did not fully recover until 8 ka with the establishment of labrador sea water ventilation ecologically opportunistic slope species prospered during this community collapse other abrupt community collapses during the past 20 ka generally correspond to millennial climate events these results indicate that deep sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less

benthic foraminifera at the cretaceous tertiary boundary around the gulf of mexico cretaceous tertiary k t boundary sections in northeastern mexico contain marly formations separated by a controversial clastic unit benthic foraminifera in seven sections indicate middle and lower bathyal depths of deposition for the marls with the exception of the upper bathyal northernmost section mixed neritic bathyal faunas were present in the clastic unit indicating redeposition in the deep basin by mass wasting processes resulting from the k t bolide impact in the gulf of mexico benthic foraminifera in the mexican sections and at other deep sea locations were not subject to major extinction at the time of impact but there were temporary changes in assemblage composition benthic faunas indicate welloxygenated bottom waters and mesotrophic conditions during the late maastrichtian and increased food supply during the latest maastrichtian the food supply decreased drastically just after the k t boundary possibly because of the collapse of surface productivity cretaceous and early paleogene benthic foraminifera however did not exhibit the benthic pelagic coupling of present day faunas as documented by the lack of significant extinction at the k t collapse of surface productivity much of the food supplied to the benthic faunas along this continental margin might have been refractory material transported from land or shallow coastal regions the decrease in food supply at the k t boundary might be associated with the processes of mass wasting which removed surface food rich sediment benthic faunas show a staggered pattern of faunal recovery in the lowermost paleogene consistent with a staged recovery of the vertical organic flux but also with a gradual buildup of organic matter in the sediment

ocean overturning since the late cretaceous inferences from a new benthic foraminiferal isotope compilation 1 benthic foraminiferal oxygen isotopic d 18 o and carbon isotopic d 13 c trends constructed from compilations of data series from multiple ocean sites provide one of the primary means of reconstructing changes in the ocean interior these records are also widely used as a general climate indicator for comparison with local and more specific marine and terrestrial climate proxy records we present new benthic foraminiferal d 18 o and d 13 c compilations for individual ocean basins that provide a robust estimate of benthic foraminiferal stable isotopic variations to 80ma andtentatively to 110ma first order variations ininterbasinal isotopicgradients delineate transitions from interior ocean heterogeneity during the late cretaceous 65 ma to early paleogene 35 65 ma homogeneity and a return to heterogeneity in the late paleogene early neogene 35 0 ma we propose that these transitions reflect alterations in a first order characteristic of ocean circulation the ability of winds to make water in the deep ocean circulate we document the initiation of large interbasinal d 18 o gradients in the early oligocene and link the variations in interbasinal d 18 o gradients from the middle eocene to oligocene with the increasing influence of wind driven mixing due to the gradual tectonic opening of southern ocean passages and initiation and strengthening of the antarctic circumpolar current the role of wind driven upwelling possibly associated with a tethyan circumequatorial current in controlling late cretaceous interior ocean heterogeneity should be the subject of further research

the maastrichtian record from shatsky rise northwest pacific a tropical perspective on global ecological and oceanographic changes we present new isotopic and micropaleontological data from a depth transect on shatsky rise that record the response of the tropical pacific to global biotic and oceanographic shifts during the mid maastrichtian results reveal a coupling between the upper ocean characterized by a weak thermocline and low to intermediate productivity and intermediate waters during the earliest maastrichtian oxygen and neodymium isotope data suggest a significant contribution of relatively warm intermediate water from the north pacific isotopic shifts through the early maastrichtian suggest that this warmer water mass was gradually replaced by cooler waters originating in the southern ocean although the cooler water mass remained dominant through the remainder of the maastrichtian it was displaced intermittently at shallow intermediate depths by north pacific intermediate water the globally recognized mid maastrichtian event similar to 69 ma manifested by the brief appearance of abundant inoceramid bivalves over shallow portions of shatsky rise is characterized by an abrupt increase similar to 2degrees 3degrees c in sea surface temperatures a greater flux of organic matter out of the surface ocean and warmer similar to 4degrees c intermediate waters results implicate simultaneous changes in surface waters and the sources distribution patterns of intermediate water masses as an underlying cause for widespread biotic and oceanographic changes during mid maastrichtian time

diversity in deep sea benthic macrofauna the importance of local ecology the larger scale history and the antarctic abstract high diversity in macrobenthos in the deep sea still lacks satisfactory explanation even if this richness may not be exceptional compared to that in coastal soft sediments explanations have assumed a highly ecologically interactive saturated local community with co existence controlled by either niche heterogeneity or spatio temporal heterogeneity embodying disturbance all have failed to provide convincing support local regional scale biodiversity relationships support the idea of local richness in macrobenthos being predominantly dependent on the larger rather local scale local scale ecological interactions seem unlikely to have overriding importance in co existence of species in the deep sea even for relatively abundant core species with wide distributions variety in observed larger scale pattern and the strong inter regional pattern particularly in the poorly known southern hemisphere seem to have a pluralistic causation these include regional scale barriers and extinctions e g arctic and ongoing adaptive zone re colonisation e g mediterranean along with other historical constraints on speciation and migration of species caused by changes in ocean and ocean basin geometry at the global scale lack of knowledge of the antarctic deep sea for example blocks coherent understanding of latitudinal species diversity gradients we need to reconcile emerging understanding of large scale historical variability in the deep sea environment with massive extinctions among microfossil indicators as recently as the pliocene to results from cladistic studies indicating ancient lineages such as asellote isopods that have evolved entirely within the deep sea the degree to which the great age diversity and high degree of endemism in antarctic shelf benthos might have enriched biodiversity in the adjacent deep seas basins remains unclear basin confluence with the atlantic indian and pacific oceans may have encouraged northwards dispersion of species from and into the deep antarctic basins so that any regional identity is superficial interpretation of the antarctic deep sea as a diversity pump for global deep sea biodiversity may simply reflect re colonisation via basin confluence of northern hemisphere areas impoverished by the consequences of rapid environmental change during the quaternary