relationships between sulphur organic carbon and iron in the modern sediments of the black sea abstract the ratio of sedimentary s to organic c has been used as a diagnostic criterion for recognizing anoxic environments in the sedimentary record here we examine the relationship between pyrite s and organic c in the modern unit 1 sediments of the black sea to re evaluate this suggested relationship in box cores from shallow oxic or near oxic water pyrite s contents ranging from 0 1 and 2 5 by weight do not correlate with organic c contents in cores from the deep anoxic basin pyrite s concentrations range between 1 0 and 2 5 and are linearly related to organic c contents with an intercept that is not significantly different from zero the s c ratio is around 0 31 in these sediments which is somewhat lower than the ratio of 0 36 considered to be characteristic of normal marine oxic sediments thus the black sea anoxic sediments appear to be depleted in s relative to organic c the degree of pyritization dop of the sediments may be a better measure of anoxic conditions of sedimentation the dop values measured here show that pyrite formation is fe limited the correlation between organic c and pyrite s probably being induced by a positive correlation between fine grained sediment components the original fe source for pyrite formation in the sediments and organic matter such fe limitation is probably characteristic of anoxic basins where pyrite formation can take place in the water column and fe oxyhydroxides do not accumulate in the surface sediments the results on the sample set examined here are at variance with earlier data and interpretations for the black sea in particular the suggested s enrichment of anoxic black sea sediments was not found because of fe limitation

distribution of recent benthic foraminifera on the sunda shelf south china sea in this study we investigate the species composition and spatial distribution patterns of rose bengal stained and unstained benthic foraminifera from the central part of the sunda shelf in the south western south china sea in relation to environmental factors the uppermost centimetre of the surface sediments 150 mu m from 45 sites from inner 60 m to outer shelf 226 m water depths revealed 584 species including 443 stained species the univariate analyses of individual species abundances and community parameters and next canonical correspondence analysis were used to relate the faunal data to a set of measured environmental parameters four biofacies recognised on the sunda shelf are most strongly correlated to water depth primary production and sediment type of the habitat the inner shelf biofacies cca cluster a defined by ammomassilina alveoliniformis and asterorotalia pulchella occurs in fine grained sediments classified as modem terrigenous mud in the region with the highest primary production values the high energy inner shelf biofacies cca cluster b defined by heterolepa dutemplei and textularia lythostrota occurs in modem terrigenous sand and silt dominated sediments northeast from the natuna island the high energy outer shelf biofacies cca cluster c defined by cibicidoides pachyderma and textularia bocki is sandwiched between assemblages of biofacies d it occurs in the region characterised by neritic relict sand in the shallow waters on the sunda shelf the relationship of benthic foraminiferal faunal composition to grain size of sediments indirectly signals the prevailing bottom hydrodynamic conditions the dominance of the epibenthic foraminifera attached to bigger particles e g cibicides lobatulus planulina arimiensis and much higher abundances of empty tests suggest greater current velocities northeast of natuna island the outer shelf biofacies cca cluster d is defined by facetocochlea pulchra and bulimina marginata it occurs in an area covered with modem terrigenous silt and mud and is characterised by lower annual primary production but seasonally influenced by weak upwelling c 2006 elsevier b v all rights reserved

sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

zur systematik der kohlenstoff schwefel eisen verhaltnisse in auftriebssedimenten abundances of organic carbon sulfur and reactive iron in sediments of three upwelling environments peru oman and benguela suggest that organic carbon reduced sulfur ratios c s ratios in this category of marine sediments deviate considerably from previously established empirical ratios in normal marine sediments to clarify the discrepancies we investigated those components of the diagenetic system that limit the formation of pyrite sulfate concentrations and reduction rates in pore waters availability of reactive iron and the quantity and quality of organic matter all three limitations are evident in our sample pools the results suggest that c s ratios in recent and fossil marine sediments rich in organic matter may be unsuitable as paleoenvironmental indicators

glaciomarine deltaic deposition and ice marginal tectonics the loch don sand moraine isle of mull scotland detailed descriptions are given of sediments exposed in the loch don sand moraine isle of mull scotland two distinct sediment landform associations occur within the moraine i a gilbert type glaciomarine delta complex graded to ca 34 m ordnance datum and ii thrust moraines consisting of deformed sands and silts whereas previous studies have attributed the moraine to a single glacial readvance this paper shows that the delta and the thrust moraines formed during ice sheet deglaciation and the loch lomond readvance respectively depositional conditions and the palaeoenvironment for each stage of moraine formation are reconstructed during the loch lomond readvance till deposition and thrust moraine formation appear to have been controlled by drainage conditions in the marginal zone of the glacier

variability of upwelling off nw africa during the latest quaternary diatom evidence diatom abundance and species composition were quantitatively studied in two latest quaternary 130 ka to the present sequences from the continental margin of northwest africa off this region coastal upwelling is well developed under the influence of the ne trade winds variations in diatom abundance in these cores are inferred to represent changes caused by varying degrees of the upwelling fertility times of high productivity are marked by high relative frequencies of chaetoceros while low productivity is marked by the dominance of aulacoseira granulata upwelling increased during glacial episodes isotopic stages 2 4 and 6 relative to isotopic stages 1 and 5 during the late holocene primary productivity levels are similar to those for stage 5 but in the early holocene upwelling intensities seem to have been weaker than today the paleoproductivity reconstruction based on the diatom record is supported by paleoproductivity estimations based on the organic carbon content of the sediments sarnthein et al 1987a

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

recent planktonic foraminiferal distribution patterns and their relation to hydrographic conditions of the gulf of tehuantepec mexican pacific abstract the distribution and abundance patterns of planktonic foraminifera in sediments and their relation to ocean dynamics were studied in the gulf of tehuantepec hydrographic and nutrient data outline the contrast between two extreme seasons in the gulf the winter early spring conditions dominated by upwelling and a cyclonic eddy that fertilize the surface waters and summer conditions with the typical stratified water column of the tropical pacific foraminiferal abundances number of individuals g of sediment are related to the ocean dynamics and productivity highest abundances are found in the areas influenced by upwelling and associated front and cold eddy and lower abundances are beneath the areas of influence of the warm core lower productivity eddies the effects of dissolution seem to be important at depths over 1000 m but do not appear to affect critically the foraminiferal remains throughout most of the studied area except near the phosphorite deposits of the oaxaqueno bank dilution by terrigenous materials from riverine inputs seafloor topography and strong transport under the upwelling jet are likely to modify the detailed pattern of foraminiferal abundance found without blurring the major imprint of productivity driven by the upwelling three planktonic foraminiferal assemblages were found reflecting the major oceanographic conditions in the gulf the globigerina bulloides assemblage dominates most of the gulf indicating the overall high productivity of the upwelling influenced surface waters the dynamics of the winter early spring upwelling and associated eddies leave a strong imprint in the planktonic foraminiferal assemblages in the sediments the distribution of the globigerinita glutinata assemblage is tied to the axis of upwelling and the globorotalia menardii neogloboquadrina dutertrei assemblage to the warm equatorial water cores the distribution patterns of these assemblages should help identify quaternary paleoenvironments influenced by upwelling and associated changes in productivity

eocene oligocene paleoceanography of the deep bay of biscay benthic foraminiferal evidence abstract a major change in benthic foraminiferal assemblages occurred in the deep bay of biscay 3 km water dsdp sites 119 and site 400a between early middle eocene and earliest oligocene predominant eocene deep sea taxa nuttallides truempyi clinapertina spp abyssamina spp and associated rarer species became extinct in this interval these extinctions were followed by an increase in abundance of bathymetrically wide ranging and stratigraphically long ranging taxa globocassidulina subglobosa oridorsalis spp gyroidinoides spp and the cibicidoides ungerianus plexus the extinctions cannot be dated precisely from the stratigraphic record recovered to date in the bay of biscay however the replacement of the n truempyi dominated assemblage has been noted previously in the deep south atlantic caribbean as occurring near the middle late eocene boundary other than the decrease in abundance and extinction of n truempyi no major abundance changes are noted within the eocene at the shallower site 401 2 km water in the bay of biscay during the oligocene nuttallides umbonifera replaced the eocene species n truempyi as the predominant deep sea benthic foraminifera reaching peak abundance in the middle oligocene at sites 119 and site 400a in the modern oceans the abundance ot n umbonifera is positively correlated with increased corrosiveness of bottom water while at site 119 the abundance of nuttallides spp is negatively correlated with 13c values in benthic foraminifera as lower 13c values are often associated with older water masses large numbers of nuttallides spp are thought to reflect older and more corrosive bottom water the faunal data and oxygen and carbon isotopic data are compared with a circulation model derived from north atlantic seismic stratigraphic studies to show that old warm corrosive and sluggish eocene bottom water was replaced by younger colder less corrosive more vigorously circulating bottom water of northern origin by the early oligocene faunal and isotopic data suggest that bottom water became older and more corrosive again in the middle oligocene reflecting a reduction in circulation that can also be inferred from the seismic record in the nearby rockall plateau region

influence of paleoenvironmental factors on preservation of organic matter in middle cretaceous greenhorn formation pueblo colorado sedimentological and geochemical studies of the upper cretaceous hartland shale and overlying bridge creek limestone members of the greenhorn formation reveal close associations between abundance of current induced sedimentary structures extent of bioturbation and type of preserved organic matter abundant hydrogen rich organic matter 4 5 wt and low sulfur to organic carbon ratios are characteristic of the laminated facies which lack current induced sedimentary structures sparse hydrogen poor organic matter 0 1 0 5 wt and relatively high sulfur to organic carbon ratios are characteristic of the bioturbated facies which contain numerous sedimentary structures indicative of currents the concentration of oxygen in the benthic environment and the degree of bio urbation of the sediment apparently were determined principally by the rate that oxygen was supplied advectively by currents rather than by the rate of oxygen consumption by decomposition thus paleoclimatic and paleo oceanographic factors that influenced mixing and current strength in the water column profoundly affected the amount and type of organic matter preserved in these units it is proposed that episodes of high river discharge lead to density stratification of the water column and in turn to quiescent oxygen depleted bottom water and high preservation of organic matter thus accounting for the intermittent widespread deposition of organic rich strata during maximum transgression and depth of the greenhorn sea the lateral association of voluminous deltaic deposits with dee water black shales in other elongate or restricted marine basins may have causes similar to those envisioned for the hartland shale and bridge creek limestone members

paleogene stable isotope events the oxygen isotope record in paleogene benthic foraminifera shows that at the base of the paleogene the ocean deep waters had a temperature of about 10 c rising to about 12 c at the base of the eocene and cooling between 51 ma and 49 ma to about 9 c the most dramatic event occurred just after the eocene oligocene boundary at about 35 8 ma when ocean deep waters cooled by several degrees within 104 105 yr probably in association with temporary glaciation in the antarctic region another more intense glacial event in antarctica may have occurred later in the oligocene at about 31 ma and a third near the top of the oligocene at 24 ma in the marine carbon isotope record a very rapid negative excursion occurred precisely at the cretaceous tertiary boundary a recovery to unusually positive values in the late paleocene was followed by a second negative excursion close to the paleocene eocene boundary that was even more extreme in magnitude although it was not as rapid these major carbon isotope events permit very accurate stratigraphic correlation there are many other smaller features in the carbon isotope record that will also prove useful for this purpose

nearshore temperate carbonate depositional systems lower tortonian agua amarga basin southern spain implications for carbonate sequence stratigraphy abstract the bryozoan rich lower tortonian carbonates of the agua amarga basin in southern spain province of almeria provide an example of sediments formed in a nearshore non tropical depositional setting based on data derived from logging of sections and from field mapping these lower tortonian carbonates form a depositional sequence which is subdivided into several depositional systems a lowstand systems tract which consists of volcaniclastic fan deltas and washover deposits formed on the leeward side of a basement shoal which delimited the basin towards the south a transgressive systems tract which is characterised by a landward encroachment of deposits is represented by submarine bars and dune deposits a highstand systems tract consists of progradational beach deposits owing to strong reworking and re distribution of the particles by currents and waves microfacies differentiation of the deposits in poor these tortonian non tropical carbonates display a style of deposition similar to siliciclastics suggesting that sequence stratigraphic concepts derived from tropical carbonates do not apply to non tropical carbonates

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

evolution of atlantic pacific δ13c gradients over the last 2 5 m y the evolution of interocean carbon isotopic gradients over the last 2 5 m y is examined using high resolution 13c records from deep sea cores in the atlantic and pacific oceans over much of the northern hemisphere ice ages relative reductions in north atlantic deep water production occur during ice maxima from 2 5 to 1 5 ma glacial reductions in nadw are less than those observed in the late pleistocene glacial suppression of nadw intensified after 1 5 ma earlier than the transition to larger ice sheets around 0 7 ma at a number of times during the pleistocene 13c values at dsdp site 607 in the north atlantic were indistinguishable from eastern equatorial pacific 13c values from approximately the same depth odp site 677 indicating significant incursions of low 13c water into the deep north atlantic atlantic pacific 13c values converge during glaciations between 1 13 1 05 m y 0 83 0 70 m y and 0 46 0 43 m y this represents a pseudo periodicity of approximately 300 kyr which cannot easily be ascribed to global ice volume or orbital forcing this partial decoupling at low frequencies of the 18o and 13c signals at site 607 indicates that variations in north atlantic deep water circulation cannot be viewed simply as a linear response to ice sheet forcing

an early miocene atlantic wide foraminiferal palaeoceanographic event abstract in the lower miocene deep sea record of the atlantic ocean a foraminiferal assemblage dominated by small smooth thin walled bolivinids occurs at several sites in different regions from 20 17 ma no modern deep sea analogues are known but such assemblages are present in modern environments in the upper bathyal zone within the oxygen minimum zone we interpret this as reflecting lowered oxygen conditions in the deep atlantic ocean perhaps resulting from a period of sluggish bottom water circulation in the early miocene ocean this was a period of major change in global 13 c equivalent to the beginning of the monterey carbon excursion

the influence of microhabitats on the carbon isotopic composition of deep sea benthic foraminifera we report 13c and 18o values for rose bengal stained benthic foraminifera from a set of box cores from continental margin environments in the atlantic and pacific oceans these isotopic results are compared with foraminiferal distribution data and pore water 13c profiles to evaluate the importance of environmental microhabitat effects on the carbon isotopic composition of benthic foraminifera the 13c values of infaunal taxa are consistently lower than those of epifaunal taxa suggesting that microhabitat effects on test composition do exist the 13c differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the 18o differences between benthic foraminifera tests and equilibrium calcite but they do correlate with variations in the chemistry of sediment pore waters however interspecific 18o differences as well as 13c differences between species with similar vertical distributions in the sediments indicate that taxon specific vital effects also influence test composition

planktic foraminiferal diversity as indicator of ocean environments abstract the combination of the number of species simple diversity an information function shannon diversity and a measure of equitability is used to characterize modern ocean environments based on planktic foraminiferal faunas regional environmental conditions can be recognized as deviations from the global latitudinal trend simple diversity number of species offers relatively little resolution itself because it is sensitive to the addition of rare species variable conditions such as the highly productive spring bloom and upwelling are characterized by relatively low diversity and equitability values relatively high diversity and a lesser increase in equitability are found in mixing zones of adjacent water masses in extreme conditions diversity is low whereas equitability is intermediate to high modern patterns can be applied to fossil sections to reconstruct regional paleoceanographic conditions thus relatively low shannon diversity with low equitability in maastrichtian heterohelicid faunas from el kef tunisia is interpreted as indicating variable conditions an increase in simple diversity mostly traces evolution of the heterohelicids as a group which diversified during the maastrichtian the number of species through time is a function of available niches and as such related to oceanic circulation on a global scale therefore when applying modern patterns to fossil sections a distinction has to be made between global diversity trends and regional environmental change the correlation between cenozoic stable isotope record and number of planktic foraminiferal species suggest indeed that simple diversity registers changes in global circulation maximum number of species occurred in the maastrichtian the middle eocene and the early middle miocene in these three instances the maxima are found after the start of a cooling trend and are interpreted as transition periods between two modes of ocean circulation causing the temporary coexistence of old and new species

paleocene to eocene benthic foraminiferal isotopes and assemblages implications for deepwater circulation early paleogene warm climates may have been linked to different modes and sources of deepwater formation warm polar temperatures of the paleocene and eocene may have resulted from either increased atmospheric trace gases or increased heat transport through deep and intermediate waters the possibility of increasing ocean heat transport through the production of warm saline deep waters wsdw in the tethyan region has generated considerable interest in addition general circulation model results indicate that deepwater source regions may be highly sensitive to changing basin configurations to decipher deepwater changes we examined detailed benthic foraminiferal faunal and isotopic records of the late paleocene through the early eocene 60 to 50 ma from two critical regions the north atlantic bay of biscay site 401 and the pacific shatsky rise site 577 these records are compared with published data from the southern ocean maud rise site 690 islas orcadas rise site 702 during the late paleocene similar benthic foraminiferal 18o values were recorded at all four sites this indicates uniform deepwater temperatures consistent with a single source of deep water the highest 13c values were recorded in the southern ocean and were 0 5 more positive than those of the pacific we infer that the southern ocean was proximal to a source of nutrient depleted deep water during the late paleocene upper paleocene reflector ab was cut on the western bermuda rise by cyclonically circulating bottom water also suggesting a vigorous source of bottom water in the southern ocean a dramatic negative excursion in both carbon and oxygen isotopes occurred in the latest paleocene in the southern ocean this is a short term 100 kyr globally synchronous event which also is apparent in both the atlantic and pacific records as a carbon isotopic excursion of approximately 1 faunal analyses from the north atlantic and pacific sites indicate that the largest benthic foraminiferal faunal turnover of the cenozoic was synchronous with the isotopic excursion lending support to the hypothesis that the extinctions were caused by a change in deepwater circulation we speculate that the southern ocean deepwater source was reduced or eliminated at the time of the excursion during the early eocene southern ocean 13c values remained enriched relative to the north atlantic and pacific however the southern ocean was also enriched in 18o relative to these basins we interpret that these patterns indicate that although the southern ocean was proximal to a source of cool nutrient depleted water the intermediate to upper deep water sites of the north atlantic and pacific were ventilated by a different source that probably originated in low latitudes i e wsdw

surface sediment diatom distribution and holocene paleotemperature variations in the greenland iceland and norwegian sea one hundred and four surface sediment samples and two piston cores from the greenland iceland and the norwegian gin sea hopkins 1988 were analyzed diatoms were common to abundant in most surface sediment samples and throughout the holocene q mode factor analysis allowed the definition of six significantly different floral assemblages which explained 91 7 of the total variance mapping of the six factors showed their close affinity to hydrographic regimes these are the norwegian atlantic current assemblage thalassionema nitzschioides paralia sulcata proboscia alata arctic water assemblage thalassiosira gravidaspores sea ice assemblage nitzschia grunowii nitzschia cylindra thalassiosira hyalina arctic norwegian waters mixing assemblage rhizosolenia hebetata f semispina rhizosolenia borealis atlantic assemblage thalassiosira oestrupii and norwegian arctic waters mixing assemblage thalassiosira gravida vegetative cells transfer functions gint2 relating factor distributions to winter february and summer august surface water temperatures were generated the transfer functions have a standard error of estimate of 1 5 c august and 1 0 c february downcore studies of core 52 43 from the norwegian basin and core 57 5 from the iceland plateau revealed diatom abundance and sea surface paleotemperature trends in the area during the holocene the first appearance of diatoms in cores 52 43 and 57 5 occurs within the vedde ash layer 10 600 years b p and the saksunarvatn ash layer 9100 years b p respectively diatom abundances increase steadily throughout the pre boreal atlantic time to 25 and 35 million valves per gram dry sediment in the norwegian basin and iceland plateau cores respectively application of the temperature transfer functions gint2 to the two holocene records revealed higher than present sea surface temperatures during the boreal atlantic chronozones for the iceland plateau and during the middle younger dryas sub boreal chronozones for the norwegian basin core temperatures decreased steadily since then with a slight increase to the present values both the iceland and the norwegian seas experienced a strong influx of temperate atlantic surface waters in the beginning of the holocene sea surface temperatures dropped steadily in the latter part of the holocene as the influx of the atlantic surface waters diminished

foraminiferal faunal evidence for glacial interglacial variations in the ocean circulation and the upwelling of the gulf of tehuantepec mexico abstract three marine sediment cores from the gulf of tehuantepec eastern tropical north pacific were used to determine variations in upwelling intensity and surface circulation patterns over the last 26 kyr bp changes in foraminiferal assemblages at glacial interglacial timescale indicate a sequence of three major palaeoceanographic events in the study area 1 the late pleistocene including the last glacial maximum lgm dominated by a neogloboquadrina dutertrei globorotalia menardii assemblage indicative of a stable thermocline stratified water column and greater persistence of warm equatorial waters in the region 2 the termination 1 dominated by a globigerinita glutinata assemblage which indicates mixed surface water and transitional conditions between upwelling and stratified water column episodes changes in sedimentation rates and a clear reduction of the faunal abundances at this time could be the result of eustatic sea level change 3 the holocene dominated by a globigerina bulloides globigerinoides ruber assemblage indicates periods of elevated productivity intense upwelling and the establishment of the modern ocean conditions these findings are consistent with climate model results that suggest that regional surface ocean and upwelling conditions are mostly linked to changes in atmospheric circulation over the laurentide ice sheet and shifts in the latitudinal position of the intertropical convergence zone

comparison of foraminiferal coccolithophorid and radiolarian paleotemperature equations assemblage coherency and estimate concordancy the imbrie kipp method of paleotemperature estimation is rigorously tested by comparing atlantic temperature equations independently derived from the microfossils of three biotic groups the foraminifera coccolithophorida and radiolaria this method consists of two steps factor analysis of the modern sea bed data of the individual groups which resolves discrete biogeographic assemblages and regression analysis of the modern assemblage data with observed sea surface temperature data to obtain paleotemperature equations assemblage biogeography shows a simple subdivision into warm low latitude and cold high latitude for all biotic groups between biotic groups there is greater similarity among high latitude assemblages than low latitude ones correlating the assemblage data with observed sea surface temperatures to produce temperature distribution patterns shows differences of less than 2 c in their optimum and critical temperatures regression analysis produced accurate temperature equations for each biotic group all with standard errors of estimate of less than or equal to 2 c multiple correlation coefficients were all greater than 0 970 applying these equations to two multiple biotic data sets the modern and ice age sea bed data and comparing their temperature estimates using the standard error pooled shows over 87 concordancy for both data sets unlike the modern data the discordancy among temperature estimates of the ice age data shows a distinct geographic distribution its cause is believed to be oceanographic a difference in the water mass structure between the modern and ice age ocean

neogene bottom water masses and benthic foraminifera in the ne atlantic ocean modern benthic foraminiferal assemblages show a correlation with oceanic bottom water masses a study of the neogene benthic foraminifera from seven sites to the south and two sites to the north of the azores ridge shows patterns of change which can be interpreted in terms of past water masses an antarctic bottom water aabw influence has been present to the south since the mid miocene but to the north of the azores ridge aabw was present only up to the late pliocene since when it has been absent overlying aabw is north atlantic deep water nadw and north east atlantic deep water neadw the latter shows a spectacular increase in importance from the late pliocene to recent the faunal changes can be correlated with changes in circulation in the late pliocene which heralded the incoming of major glacial events from c 2 4 ma

the distribution of living benthic foraminifera on the continental slope and rise off southwest norway abstract surface sediment samples taken by corer from 45 stations on the norwegian continental margin and in the norway basin have been investigated for their benthic foraminiferal content unlike previous studies the living benthic foraminiferal fauna was differentiated from empty tests comprising the foraminiferal death assemblage factor analysis of both the living and dead faunal data reveals six living species assemblages and five corresponding dead assemblages the additional living assemblage is characterized by the arenaceous speciescribrostomoides subglobosum that dominates between 1400 and 2000 m water depth but is rare in the dead faunal data trifarina angulosa and to a lesser extent cibicides lobatulus characterize the shallowest foraminiferal assemblage from 200 to 600 m water depth where it is associated with strong bottom currents and warm saline atlantic water of the north atlantic drift on the slope between 600 and 1200 m water depth themelonis zaandami species assemblage dominates particularly in areas characterized today by rapid sedimentation of terrigeneous material between 1000 and 1400 m depth where the slope is covered by fine grained organic rich terrigeneous mud the living foraminiferal assemblage is characterized bycassidulina teretis andpullenia bulloides below 1400 m three foraminiferal assemblages are found c subglobosum is found from 1400 to 2000 m cibicidoides wuellerstorfi andepistominella exigua predominantly live from 2000 to 3000 m water depth and below 3000 m oridorsalis umbonatus andtriloculina frigida dominate the fauna all of theelphidium excavatum tests found in this study and thecassidulina reniforme tests found above 500 m water depth were found to be reworked analysis of the sediment grain size distribution and the organic carbon content in surface samples from the deepest stations suggest that the abundance ofc wuellerstorfi ande exigua is positively correlated to relatively coarse caused by planktic foraminifera and organic rich sediments whereas high frequencies ofo umbonatus andt frigida coincide with low organic carbon content we suggest thatc wuellerstorfi is adapted to deep sea environments with relatively high food supply tolerating relatively low interstitial water oxygen content whereaso umbonatus may tolerate lower food supply prefering well oxygenated interstitial waters

degree of pyritization of iron as a paleoenvironmental indicator of bottom water oxygenation abstract a new method is presented for recognizing the degree of bottom water oxygenation in organic carbon bearing rock the method uses the parameter degree of pyritization dop which is the ratio of pyritic fe to pyritic fe acid soluble fe sediments with ages ranging from devonian to cretaceous have been classified on paleoecological and sedimentological criteria as having been deposited in aerobic conditions deposited in fully oxygenated bottom waters restricted marine conditions deposited in waters with low oxygen concentrations or inhospitable bottom conditions where little or no oxygen is present and h2s may be continually or intermittently present aerobic dop

carbon accumulation rates and the origin of the holocene sapropel in the black sea a detailed radiocarbon chronology obtained by accelerator mass spectrometry together with organic carbon and carbonate measurements on two black sea cores has been used to compare and contrast the burial fluxes of organic carbon in the holocene sapropel and the modern sediment at both deep water and eastern slope sites the sapropel is separated from the modern facies by a variable thickness of compositionally homogeneous sediment with low levels of organic carbon and anomalously old radiocarbon ages this homogeneous unit probably represents deposition by slumping or mudflow the age limits of the sapropel are 1600 6600 b p at the deep water site and 4000 6000 b p radiocarbon years before 1950 a d at the shallow water site the carbon accumulation rate in the deep water sapropel is higher than that in the modern deep water facies by a factor of 2 and is approximately the same as that in the modern sediment in shallow water the revised chronology of sapropel formation and the differences in the carbon accumulation rates probably indicate that the sapropel was formed by increased production during the transition from the premodern lake to the modern marine phases of the black sea this conclusion is consistent with the clear marine carbon isotope signal in the organic mattermore in the sapropel in both cores results to be reported elsewhere in contrast to the mixed source of carbon in the other facies less

the last interglacial ocean the final effort of the climap project was a study of the last interglaciation a time of minimum ice volume some 122 000 yr ago coincident with the substage 5e oxygen isotopic minimum based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean last interglacial sea surface temperatures sst were compared with those today there are small sst departures in the mid latitude north atlantic warmer and the gulf of mexico cooler the eastern boundary currents of the south atlantic and pacific oceans are marked by large sst anomalies in individual cores but their interpretations are precluded by no analog problems and by discordancies among estimates from different biotic groups in general the last interglacial ocean was not significantly different from the modern ocean the relative sequencing of ice decay versus oceanic warming on the stage 6 5 oxygen isotopic transition and of ice growth versus oceanic cooling on the stage 5e 5d transition was also studied in most of the southern hemisphere the oceanic response marked by the biotic census counts preceded led the global ice volume response marked by the oxygen isotope signal by several thousand years the reverse pattern is evident in the north atlantic ocean and the gulf of mexico where the oceanic response lagged that of global ice volume by several thousand years as a result the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years these regional lead lag relationships agree with those observed on other transitions and in long term phase relationships they cannot be explained simply as artifacts of bioturbational translations of the original signals

benthic foraminiferal assemblage response to the onset of northern hemisphere glaciation paleoenvironmental changes and species trends in the northeast atlantic abstract the response of the benthic foraminiferal community in the northeast atlantic to the late pliocene onset of northern hemisphere glaciation was investigated using closely spaced samples from dsdp ipod site 548 factor analysis of quantitative species abundance data shows that the replacement of aglobocassidulina subglobosa assemblage first bybulimina mexicana and then bymelonis uvigerina dominated assemblages accompanied the onset of glaciation also the benthic assemblages became much more variable with progressive climatic deterioration in order to examine benthic foraminifera species responses to changing paleoenvironmental variables measurements of planktonic foraminifera species abundances benthic foraminifera stable isotope values and sediment grain size and composition were made the planktonic data and oxygen isotope values were used to quantify paleoclimatic changes and changes in bottom water properties the sediment analyses were used to quantify changes in the substrate and a combination of planktonic assemblage data and benthic carbon isotope values were used to estimate changes in food supply surface ocean productivity canonical correlation analysis of the species data and the independent paleoenvironmental indicators shows a strong relationship between planktonic assemblage diversity and the long term benthic trend of assemblage replacement this trend could be a response to changing bottom water properties but it might also reflect increasing food supply at the sea bed in addition the benthic assemblages show a strong relationship to changes in the carbonate content of the sediments this latter fluctuates due to varying terrigenous input changes in substrate at site 548 may influence the benthic foraminiferal assemblage there remains however a significant fraction of species abundance variability particularly in theuvigerina species that cannot be explained with the paleoenvironmental indicators used in this study

a new planktic foraminifer transfer function for estimating pliocene holocene paleoceanographic conditions in the north atlantic abstract a new planktic foraminifer transfer function gsf18 related 5 north atlantic assemblages to winter and summer sea surface temperature gsf18 based on recombined and simplified core top census data preserves most environmental information and reproduces modern north atlantic conditions with approximately the same accuracy as previous transfer functions but can be more readily applied to faunal samples ranging in age from pliocene to holocene transfer function gsf18 has been applied to faunal data from deep sea drilling project hole 552a to produce a 2 5 m y sea surface temperature sst time series estimates show several periods between 2 3 and 4 6 ma during which mean sst s were both several degrees warmer and several degrees cooler than modern conditions between 2 9 and 4 0 ma sst was generally warmer than modern except for a 250 k y interval centered at 3 3 ma maximum sst with respect to modern conditions occurred after the cool interval near 3 1 ma when sst was approximately 3 6 c warmer than present conditions comparison of sst estimates with stable isotope data suggest that after peak warming at 3 1 ma there was an overall surface water cooling with concomitant build up of global ice volume culminating in northern hemisphere glaciation this event is also indicated by the presence of ice rafted detritus in 552a sediments at about 2 45 ma

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

movement of oceanic fronts south of australia during the last 10 ka interpretation of calcareous nannoplankton in surface sediments from the southern ocean abstract preservation of calcareous nannoplankton in surface sediment samples from the southern ocean south of australia and adjacent to new zealand record a single assemblage the dominant species are emiliania huxleyi gephyrocapsa muellerae calcidiscus leptoporus helicosphaera carteri and coccolithus pelagicus the assemblage varies little in abundance and diversity with minor correlation to present day overlying surface water masses and oceanic fronts increase in abundance of h carteri and c pelagicus in the region of the subtropical front may reflect higher nutrients associated with this front the assemblage although altered by dissolution represents a warmer climatic interval than present day with the presence of preferentially dissolved warm water species preserved as far south as the polar front the presence of warm water species under sub antarctic waters at the polar front is interpreted as a relic population from the holocene climatic optimum of 10 8 ka the absence of coccoliths in sediments poleward of the polar front suggests an equatorward shift of this front following the climatic optimum resulting in increased productivity of siliceous phytoplankton associated with the colder waters and increased dissolution of coccoliths movement of the subtropical front for the same interval is not recorded in the preserved coccoliths the more heavily calcified form of e huxleyi which dominates the living assemblage north of the subtropical front is subject to dissolution in this region and is poorly preserved in the sediment assemblage

a 220 000 year climatic record for the east equatorial atlantic ocean and equatorial africa evidence from diatoms and opal phytoliths in the zaire congo deep sea fan accumulation rates of microfossil associations are independent of each other and in addition to percentages give indispensable information about the significance of micropaleontological data marine diatoms reveal that coastal upwelling in the zaire fan region was strong during glacial stages and weaker during interglacial stages oceanic upwelling was intense in stages 6 and 2 and at the stage 5d 5c transition but not in stage 4 the benguela current did not penetrate into the gulf of guinea during the last 220 000 years the phfd index based on the contribution of freshwater diatoms and phytoliths is a measure of aridity in equatorial africa the production in the low salinity river plume was high in the most humid periods on land and low when the continent was arid on the long term nutrient supply of the zaire river to the ocean was probably larger in humid than in arid periods periods of strong seasonal variability in river fluxes and coastal upwelling coincide with arid intervals except in the very humid interval with strong seasonal contrasts 35 000 20 000 years b p

organic carbon sulphur and iron in recent semi euxinic sediments of kau bay indonesia kau bay island of halmahera eastern indonesia is a 470 m deep basin separated from the pacific ocean by a sill that is at present only 40 m below sea level during weichselian time the sea level dropped below the depth of the sill and freshwater sediments were deposited these sediments are rich in organic matter corg 2 6 wt with terrigenous isotope characteristics 13corg 28 to 30 and are also rich in sulphur s 4 wt this sulphur enrichment is interpreted to be a late diagenetic feature related to diffusion of dissolved sulphate and sulphide from the marine sediments into the freshwater sediments the sulphur in these sediments has a 34s value of 15 the overlying holocene sediments consist of marine muds deposited in alternating low oxygen and h2s bearing bottom waters the marine sediments are also rich in organic matter corg 2 6 wt but of mixed terrigenous and marine origin 13c 25 to 19 moreover the sulphur content of these holocene sediments is lower s 1 2 wt and isotopically lighter 34s 20 in addition to pyrite large amounts of acid volatile sulphur avs compounds accumulate in kau bay the reactive iron content of the sediment limits the amount of iron that is sulphidized while the supply of oxidants controls the limited conversion of avs to pyrite total and reactive iron contents are strongly correlated with the amount of terrigenous organic matter as a consequence of their common provenance and depositional histories the marine sediments in kau bay show no simple relation between organic carbon and sulphur

a benthic foraminiferal proxy of pulsed organic matter paleofluxes in the temperate open ocean of the modern northeast atlantic the spring bloom of phytoplankton leads to a seasonal pulse of detrital organic material phytodetritus to the ocean floor opportunistic benthic foraminifera rapidly colonise this food resource producing large numbers of individuals whose tests are ultimately added to the sediment one of these taxa epistominella exigua shows periodic peaks in abundance in the fossil record at many open ocean sites previously such peaks have been commonly interpreted to result from changes in physicochemical properties of bottom water mass and thus deep sea circulation the main purpose of this paper is to propose thate exigua may be used as a proxy of pulsed organic matter inputs to the deep ocean and therefore as an indicator of relative changes in productivity

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

palaeoceanographic significance of recent foraminiferal biofacies on the southern shelf of western australia a preliminary study the southern shelf of western australia lies close to the subtropical convergence in a region strongly influenced by the warm leeuwin current from the north and the cold more massive western australian current from the south fresh holocene and relict pleistocene foraminiferal specimens are mixed in dredged sediment samples similar in composition to those from other parts of the southern australian margin the holocene planktonic assemblages are dominated in the west by subtropical forms globigerinoides trilobus s l globorotalia menardii and neogloboquadrina dutertrei and in the east by the temperate species globorotalia inflata three holocene benthic assemblages are distributed from the inner shelf to the upper slope also showing a strong longitudinal gradation from west to the east the change from warm water assemblages to temperate assemblages is progressive and continuous but the southwest corner is marked by the southerly limit of some larger benthic taxa including heterostegina and the area off esperance is the furthermost extent of an abundant though patchy living amphisorus marginopora association this w e gradation indicates that the leeuwin current has played a key role in influencing the distribution of foraminifera as from at least the last interglacial because this pattern exists not only in the holocene but also in the relict foraminiferal biofacies 1999 elsevier science b v all rights reserved

reactive iron in marine sediments abstract a combined field laboratory study has been undertaken to explore the mineralogy concentrations and reactivity towards sulfide of iron in marine sediments also considered is the importance of bacterial fe liberation in regulating pore water chemistry two contrasting marine environments are included one is the relatively fe poor foam site and the other is the fe rich sediment of the subaqueous mississippi delta results show that oxide minerals are the most important fe phases in early diagenetic pyrite formation however viewed separately lepidocrocite and ferrihydrite are more reactive towards sulfide than goethite and hematite when fe oxides are present in relatively high concentrations dissolved sulfide is nearly absent from sediment pore waters with concomitant high concentrations of dissolved fe even in the presence of active sulfide production by sulfate reduction a combination of experimental results and diagenetic modelling shows that in some sediments pore water fe finds it origin in the bacterial reduction of iron oxides this seems the case even though greater amounts of fe are reduced by reaction of sulfide with iron oxides it appears that distinct microenvironments may exist in marine sediments where in one microenvironment sulfide reacts with fe oxides locally precipitating fe sulfide minerals in another fe reduced and solubilized by microorganisms migrates freely into solution

unlocking the ice house oligocene miocene oxygen isotopes eustasy and margin erosion oxygen isotope records and glaciomarine sediments indicate at least an intermittent presence of large continental ice sheets on antarctica since the earliest oligocene circa 35 ma the growth and decay of ice sheets during the oligocene to modern ice house world caused glacioeustatic sea level changes the early eocene was an ice free greenhouse world but it is not clear if ice sheets existed during the middle to late eocene doubt house world benthic foraminiferal 18o records place limits on the history of glaciation suggesting the presence of ice sheets at least intermittently since the earliest oligocene the best indicator of ice growth is a coeval increase in global benthic and western equatorial planktonic 18o records although planktonic isotope records from the western equatorial regions are limited subtropical planktonic foraminifera may also record such ice volume changes it is difficult to apply these established principles to the cenozoic 18o record because of the lack of adequate data and problems in stratigraphic correlations that obscure isotope events we improved oligocene to miocene correlations of 18o records and erected eight oxygen isotope zones oi1 oi2 mi1 mi6 benthic foraminiferal 18o increases which are associated with the bases of zones oil circa 35 8 ma oi2 circa 32 5 ma and mil circa 23 5 ma can be linked with 18o increases in subtropical planktonic foraminifera and with intervals of glacial sedimentation on or near antarctica our new correlations of middle miocene benthic and western equatorial planktonic 18o records show remarkable agreement in timing and amplitude we interpret benthic planktonic covariance to reflect substantial ice volume increases near the bases of zones mi2 circa 16 1 ma mi3 circa 13 6 ma and possibly mi5 circa 11 3 ma possible glacioeustatic lowerings are associated with the 18o increases which culminated with the bases of zone mi4 circa 12 6 ma and mi6 circa 9 6 ma although low latitude planktonic 18o records are required to test this these inferred glacioeustatic lowerings can be linked to seismic and rock disconformities for example we link 12 oligocene early late miocene inferred glacioeustatic lowerings with 12 of the sequence boundaries inferred eustatic lowerings of haq et al 1987

variations in surface water mass conditions in the norwegian sea evidence from holocene coccolith and dinoflagellate cyst assemblages coccolith and dinoflagellate cyst assemblages have been investigated in five sediment cores from the norwegian sea and fram strait both fossil groups are characterized by similar patterns of composition the assemblages contain high proportions of single species the coccolith flora is of low diversity and consists almost entirely of coccolithus pelagicus and emiliania huxleyi the dinoflagellate cysts are generally dominated by operculodinium centrocarpum and nematosphaeropsis labyrinthus other species especially bitectatodinium tepikiense peridinium faeroense and impagidinium pallidum sometimes contribute considerably to the assemblages based on the abundance of the assemblages and the ratio change between the dominating species it has been possible to establish three intervals of distinct major changes in surface water mass conditions sparse occurrences of coccoliths and dinoflagellate cysts have been observed before 10 000 yrs b p indicating harsh environmental conditions with a distinct influence of meltwater and temporarily very slight inflow of atlantic water the modern surface water circulation pattern was reinitiated during termination ib the assemblages suggest slightly cooler and probably less saline surface water conditions than are present today until 7500 yrs b p solar insolation may have caused a first temperature peak which is responsible for the early holocene productivity maximum a considerable change in the composition of dinocyst and coccolith assemblages occurs corresponding approximately to the onset of the holocene climatic optimum this change was most probably linked to an almost synchronous reorganization of the hydrographic properties in the entire north atlantic realm after the ice sheets had vanished since 6000 yrs b p the norwegian current with its modern oceanographic and ecological properties has been fully established