late neogene deep sea benthic foraminifera at odp site 762b eastern indian ocean diversity trends and palaeoceanography abstract in the present investigation the late neogene deep sea benthic foraminiferal diversity at odp site 762b has been measured by using hurlbert s diversity index s m this index measures the expected number of species to a common sample size m here m is put equal to 100 this method is relatively more advantageous than other commonly used diversity indices because it eliminates differences in sample size the late neogene section at site 762b is characterised by marked variations in species diversity s 100 of the deep sea benthic foraminiferal assemblages species diversity broadly exhibits an inverse relationship with the values of uvigerina proboscidea abundance and percentage of infaunal taxa in the examined section of the site this suggests that temporal variations in primary productivity of the overlying surface waters are reflected in the late neogene deep sea benthic foraminiferal diversity trends the species diversity pattern explains that the trophic level of the bottom water changed at the beginning of the late pliocene 3 5 ma due to an increased surface water productivity the higher values of species diversity during the early pliocene was due to a stable deep sea environment with low trophic resource levels however the late pliocene and pleistocene interval is largely characterised by low diversity reflecting an unstable deep sea environment with higher surface water productivity a distinct increase in the values of species diversity along with low percentages of u proboscidea and infaunal taxa during the latest pliocene 2 3 1 9 ma suggests low organic carbon influx in the bottom waters due to a decrease in the surface water productivity

late quaternary benthic foraminifera and deep water paleoceanography in the south china sea abstract recent and late quaternary deep sea benthic foraminifera in the south china sea scs have been quantitatively studied in order to approach some disputable questions about the glacial deep circulation of the pacific from the paleoceanographic records of a marginal sea for example whether or not there existed the north pacific deep water npdw during glacials based on the quantitative data of deep sea benthic foraminiferal faunas from sixty six surface sediment samples of the scs a q mode factor analysis indicates that the globocassidulina subglobosa assemblage the astrononion novozealandicum and bulimina aculeata assemblages and the eggerella bradyi assemblage are associated with the intermediate water mass iwm deep water mass dwm and the deep water below ccd in the scs respectively the factor assemblages resulted from surface sample data were then applied to the quantitative analysis of late quaternary deep sea benthic foraminifera in eight cores from the scs and western pacific the results show a generally increased contribution of the dwm assemblage relative to that of the iwm assemblage during glacials which implies that the influence of the dwm increased and that of the iwm decreased in the scs and western pacific however there were two major deep water paleoceanographic changes during the late quaternary 1 the deep sea carbonate dissolution of the scs and western pacific was intensified during 18 0 stages 4 5 evidenced by the higher arenaceous calcareous ratios of benthic foraminifera and relative abundance of eggerella bradyi 2 the influence of the pacific dwm above 2500 m greatly increased during the last glacial maximum lgm inferred from the increased abundances of the pacific dwm benthic foraminiferal assemblage as compared to those of the pacific iwm and pacific bottom water mass assemblages in the western pacific particularly the water in which favocassidulina favus was distributed could not enter the scs since the lgm meanwhile the great changes had taken place in the dwm of the scs during the lgm reflected in the occurrence of a clearly cooled and ventilated dwm and the replacement of a novozealandicum and b aculeata assemblages by b aculeata melonis barleeanum assemblage at water depths of 1000 2500 m these significant changes during the lgm may be related to the formation of the npdw

benthic foraminifera from the carnarvon ramp reveal variability in leeuwin current activity western australia since the pliocene abstract benthic foraminiferal assemblages from a 300 m deep core from an outer carbonate ramp site off western australia international ocean discovery program core u1460a were examined to reconstruct the paleoceanographic evolution of the carnarvon ramp and the warm surficial leeuwin current lc for the last 3 54 ma of the identified 179 benthic foraminiferal species occurrences of the 15 most abundant taxa were assessed using q mode cluster analysis and non metric dimensional scaling diversity equitability planktonic benthic index microhabitat preference and sedimentary parameters such as lithology and sponge spicule content were analyzed to gather information about past intermediate and surface water circulation relative abundances of infaunal and epifaunal species were applied to indicate changes in organic matter supply and oxygenation at the sea floor influence of upwelling was recognized by a high infaunal species ratio with dominance by uvigerina peregrina lagena annellatrachia and trifarina bradyi epifaunal species such as hanzawaia nipponica and hyalinea florenceae gradually became more abundant around 1 14 ma indicating increased ventilation and establishment of the paleo lc a more substantial change was initiated by 0 91 ma as marked by key species spirorutilus carinatus and rotorbinella sp together with increased faunal diversity benthic foraminiferal accumulation rates and evidence for suspension feeding sponges with the lc flow suppressing upwelling and better ventilated waters entering the shelf the environment favored epifaunal agglutinates rotalids and miliolids while buliminids decreased under high flow conditions of the lc sponge spicules and skeletal carbonate production reached an optimum at 0 6 ma before returning to modern conditions supported by these observations we propose the following paleoceanographic evolution of the carnarvon ramp during the late pliocene to mid pleistocene 3 54 0 91 ma conditions of deep water upwelling from the western australian current and indian ocean gyre indicate the absence of the capping lc on the outer carbonate ramp a transitional phase started in the mid pleistocene 1 14 0 61 ma the paleo lc triggered gradual oxygenation at the sediment water interface which coincided with an increase in carbonate sedimentation rates and waning sea surface productivity during a third phase mid pleistocene to present 0 91 0 ma the lc s intensity and flow rates peaked at 0 6 ma benthic foraminiferal accumulation rates reached a high then decreased to present day rates for short periods sea surface productivity was moderately enhanced likely due to fluctuating lc persistence or landward shift during glacial maxima

origin of late pleistocene bryozoan reef mounds great australian bight bryozoan rich biogenic mounds grew periodically on the prograding carbonate slope of the central great australian bight throughout pliocene pleistocene time cores from three odp leg 182 drill sites provide a record of mound growth during the last 300 000 years over a stratigraphic thickness of similar to 150 m these mounds the first such structures described from the modern ocean grew between paleodepths of 100 and 240 m we infer that the upper limit of growth was established by swell wave base and the lower boundary was fixed by an oligotrophic water mass detailed chronostratigraphy based on radiometric and u series dating benthic foraminifer stable isotope stratigraphy and planktonic foraminifer abundance ratios confirms that buildups flourished during glacial lowstands even numbered marine isotope stages but were largely moribund during interglacial highstands and are not extant today mound floatstones are compositionally a mixture of in situ bryozoans comprising 96 genera and characterized by fenestrate flat robust branching encrusting nodular arborescent and delicate branching growth forms the packstone matrix comprises autochthonous and allochthonous sand size bryozoans benthic and planktonic foraminifers serpulids coralline algae sponge spicules peloids and variable glauconite and quartz grains together with mud size ostracods tunicate spicules bioeroded sponge chips and coccoliths intermound allochthonous packstone and local grainstone contain similar particles but they are conspicuously worn abraded blackened and bioeroded an integrated model of mound accretion during sea level lowstands begins with delicate branching bryozoan floatstone that increases in bryozoan abundance and diversity upward over a thickness of 5 10 m culminating in thin intervals of grainstone characterized by reduced diversity and locally abraded fossils mound accumulation was relatively rapid 30 67 cm ky and locally punctuated by rudstones and firmgrounds intermound highstand deposition was comparatively slow 17 25 cm ky and typified by meter scale fining upward packages of packstone and grainstone or burrowed packstone with local firmgrounds overlain by characteristically abraded particles mound growth during glacial periods is interpreted to have resulted from increased nutrient supply and enhanced primary productivity such elevated trophic resources were both regional and local and thought to be focused in this area by cessation of leeuwin current flow together with northward movement of the subtropical convergence and related dynamic mixing

climatic records over the past 30 ka from temperate australia a synthesis from the oz intimate workgroup temperate australia sits between the heat engine of the tropics and the cold southern ocean encompassing a range of rainfall regimes and falling under the influence of different climatic drivers despite this heterogeneity broad scale trends in climatic and environmental change are evident over the past 30 ka during the early glacial period 30 22 ka and the last glacial maximum 22 18 ka climate was relatively cool across the entire temperate zone and there was an expansion of grasslands and increased fluvial activity in regionally important murray darling basin the temperate region at this time appears to be dominated by expanded sea ice in the southern ocean forcing a northerly shift in the position of the oceanic fronts and a concomitant influx of cold water along the southeast including tasmania and southwest australian coasts the deglacial period 18 12 ka was characterised by glacial recession and eventual disappearance resulting from an increase in temperature deduced from terrestrial records while there is some evidence for climatic reversals e g the antarctic cold reversal in high resolution marine sediment cores through this period the high spatial density of holocene terrestrial records reveals an overall expansion of sclerophyll woodland and rainforest taxa across the temperate region after 12 ka presumably in response to increasing temperature while hydrological records reveal spatially heterogeneous hydro climatic trends patterns after 6 ka suggest higher frequency climatic variability that possibly reflects the onset of large scale climate variability caused by the el nino southern oscillation

carbon isotopic changes in benthic foraminifera from the western south atlantic reconstruction of glacial abyssal circulation patterns oxygen and carbon isotopic analyses have been performed on the benthic foraminifer planulina wuellerstorfi in seven late quaternary cores from the vema channel rio grande rise region the cores are distributed over the water depth interval of 2340 to 3939 m which includes the present transition from north atlantic deep water nadw to antarctic bottom water aabw the carbon isotopic records in the cores vary as a function of water depth the shallowest and deepest cores show no significant glacial interglacial difference in 13c four of the five cores presently located in the nadw have benthic foraminiferal 13c that is lower during glacial isotopic stages based on bathymetric gradients in 13c we conclude that like today there were two water masses present in the vema channel during glacial intervals a water mass enriched in 13c overlying another water mass depleted in 13c the largest gradient of change of 13c with depth however occurred at 2 7 km 1 km shallower than the present position of this gradient on the basis of paleontologic and sedimentologic evidence we consider it unlikely that the nadw aabw transition shallowed to this level reduced carbon isotopic gradients between the deep basins of the north atlantic and pacific oceans during the last glaciation suggest that production of nadw was reduced lower production of nadw may have modified the local abyssal circulation pattern in the vema channel region

multiple monsoon controlled breakdown of oxygen minimum conditions during the past 30 000 years documented in laminated sediments off pakistan abstract late holocene laminated sediments from a core transect centred in the oxygen minimum zone omz impinging at the continental slope off pakistan indicate stable oxygen minimum conditions for the past 7000 calendar years high sw monsoon controlled biological productivity and enhanced organic matter preservation during this period is reflected in high contents of total organic carbon toc and redox sensitive elements ni v as well as by a low diversity high abundance benthic foraminiferal buliminacea association and high abundance of the planktonic species globigerina bulloides indicative of upwelling conditions surface water productivity was strongest during sw monsoon maxima stable omz conditions reflected by laminated sediments were found also during warm interstadial events preboreal bolling allerod and dansgaard oeschger events as well as during peak glacial times 17 22 5 ka all ages in calendar years sediment mass accumulation rates were at a maximum during the preboreal and younger dryas periods due to strong riverine input and mobilisation of fine grained sediment coinciding with rapid deglacial sea level rise whereas eolian input generally decreased from glacial to interglacial times in contrast the occurrence of bioturbated intervals from 7 to 10 5 ka early holocene in the younger dryas 11 7 13 ka from 15 to 17 ka heinrich event 1 and from 22 5 to 25 ka heinrich event 2 suggests completely different conditions of oxygen rich bottom waters extremely low mass and organic carbon accumulation rates a high diversity benthic fauna all indicating lowered surface water productivity during these intervals the omz was very poorly developed or absent and a sharp fall of the aragonite compensation depth favoured the preservation of pteropods the abundance of lithogenic proxies suggests aridity and wind transport by northwesterly or northeasterly winds during these periods coinciding with the north atlantic heinrich events and dust peaks in the tibetan loess records the correlation of the monsoon driven omz variability in the arabian sea with the rapid climatic fluctuations in the high northern latitudes suggests a close coupling between the climates of the high and low latitudes at a global scale

femg interdiffusion in olivine up to 9 gpa at t 600 900 c experimental data and comparison with defect calculations abstract interdiffusion data at high pressures are needed to provide good estimates of the closure temperatures of geothermometers based on fe mg exchange in olivine in contact with other phases and to understand the pressure dependence of high temperature deformation in olivine we report here measurements of the interdiffusion coefficient of fe mg in san carlos olivine of mean composition mg mg fe 0 90 in the range of temperatures t 600 900 c and pressures p 0 5 9 gpa the measurements were performed by preparing olivine samples covered by a thin layer of fayalite these specimens were annealed in a uniaxial split sphere apparatus ussa 2000 the fe mg interdiffusion profiles were analysed by rutherford back scattering rbs the results yield a pre exponential factor d 0 7 7 10 8 cm 2 s 1 7 7 10 12 m 2 s 1 and an activation energy e 147 58 kjmol 1 or 62 58 2 sd kj mol 1 if a p o 2 1 6 correction is performed corresponding to the expression d d 0 exp e rt exp x fe exp pv rt our data are fitted best with 3 x fe fe fe mg is between zero and one in the present experiments x fe is around 0 1 p is the pressure and v is found to be 0 5 0 6 cm 3 mol 1 or 1 0 9 cm 3 mol 1 if a p o 2 1 6 correction is performed i e about zero in the p and t range investigated comparisons between the present results obtained at relatively low temperature under extrinsic conditions for diffusion with other fe mg interdiffusion data at high temperature 1125 c or more under intrinsic conditions allow us to deduce that the migration activation volume for point defects is v m 0 whereas that for formation is v f 5 5 cm 3 mol 1 this has important implications for the creep sensitivity to pressure numerical simulations involving energy minimizations and performed with the cascade and parapocs codes confirm these conclusions one finds v m 0 and v f 4 8 cm 3 mol 1 the activation energy e deduced from the experiments as well as the pre exponential factor d 0 now permit precise estimation of the closure temperatures of geothermometers based on the fe mg exchange between olivine and spinel

benthic foraminiferal response to variations in surface water productivity and oxygenation in the northern arabian sea abstract a benthic foraminiferal record of 120 000 year obtained from the base of the oxygen minimum zone omz at a site in the northern arabian sea was studied quantitative benthic foraminiferal data were compared with palaeoproductivity indices corg and globigerina bulloides and indices for bottom water oxygen concentration pteropod preservation index mo al v al and mn al the benthic foraminiferal record revealed two distinct assemblages that show variations in the precession frequency band a high diversity low equitability assemblage proliferates in isotopic stages 1 4 and 5 and has been interpreted to reflect relatively oxygenated bottom water conditions this assemblage shows a strong covariance with minima in summer monsoon productivity a low diversity low equitability fauna typically with a few species showing high dominances is considered to reflect low bottom water oxygen conditions related to eutrophic surface water conditions dominating species in this assemblage are bolivinids buliminids and globobuliminids this assemblage dominates during precession driven maxima in summer surface water productivity and also during isotopic stages 2 and 3 we suggest that an intensified and colder glacial winter ne monsoon led to increased winter production which superimposed on the precession driven changes in surface water productivity resulted in overall poorly oxygenated bottom water during glacial stages 2 and 3 a promising proxy for tracing winter productivity in the northern arabian sea is the planktonic foraminifer globigerina falconensis the benthic foraminiferal species rotaliatinopsis seminvoluta in particular is prolific under glacial conditions

carbonate sedimentation beneath the antarctic circumpolar current during the late quaternary abstract calcium carbonate content and planktonic foraminiferal fragmentation have been studied in four late quaternary eltanin piston cores e48 22 e48 28 e49 18 and e49 23 taken from the southeast indian ridge between 3200 and 3400 m waterdepth beneath the antarctic circumpolar current the calcium carbonate records in the two southernmost cores e49 18 and e49 23 show distinct glacial interglacial cycles with the glacial intervals and intermediate cool intervals having low carbonate values relative to the interglacial times however the carbonate records of e48 22 and e48 28 are largely independent of the paleoclimatic records and may be influenced by input of volcanic ash from the st paul or amsterdam islands located less than 700 km upwind of the cores planktonic formainiferal fragmentation considered to be a dissolution index indicates that dissolution generally increased during glacial intervals relative to the interglacial intervals in e49 18 and e49 23 in e48 22 and e48 28 the dissolution records do not follow glacial interglacial patterns but instead dissolution was greatest during oxygen isotope stage 9 the stage 9 8 boundary the early part of stage 8 and during stage 7 no relationship exists between benthonic formainiferal changes and the fragmentation records in three cores e48 22 e48 28 and e49 23 indicating that deep water circulation changes had minimal or no influence on these dissolution records however in e49 18 the benthonic foraminiferal and the dissolution records are closely matched from oxygen isotope stages 12 to 5 t 440 000 120 000 yrs b p deep water circulation changes may have influenced the dissolution record in e49 18 or the two variables may be unrelated but may have independently responded to glacial interglacial climatic changes

13c record of benthic foraminifera in the last interglacial ocean implications for the carbon cycle and the global deep water circulation the 13c 12c ratios of upper holocene benthic foraminiferal tests genera cibicides and uvigerina of deep sea cores from the various world ocean basins have been compared with those of the modern total carbon dioxide tco2 measured during the geosecs program the 13c difference between benthic foraminifera and tco2 is 0 07 0 04 for cibicides and 0 83 0 07 for uvigerina at the 95 confidence level 13c analyses of the benthic foraminifera that lived during the last interglaciation isotopic substage 5e about 120 000 yr ago show that the bulk of the tco2 in the world ocean had a 13c value 0 15 0 12 lower than the modern one at the 95 confidence level reflecting a depletion compared to the present value of the global organic carbon reservoir regional differences in 13c between the various oceanic basins are explained by a pattern of deep water circulation different from the modern one the antarctic bottom water production was higher than today during the last interglaciation but the eastward transport in the circumpolar deep water was lower

uvigerina proboscidea abundances and paleoceanography of the northern indian ocean dsdp site 214 during the late neogene abstract this study attempts to understand the significance of uvigerina proboscidea in paleoceanographic reconstructions at the northern tropical indian ocean dsdp site 214 from the late miocene through the pleistocene in this interval at this site u proboscidea is the most abundant species of the benthic assemblage and shows abrupt frequency changes about 1 74 based on relative percentages of u proboscidea calibrated with oxygen and carbon isotope record and the sediment accumulation rates the modern distribution of the species in the indian ocean and other evidence the peaks of abundance of u proboscidea are inferred to represent times of high surface productivity this productivity is related to intensified trade winds during strong southwest sw indian monsoons causing widespread upwelling along equatorial divergence in the indian ocean the sudden increase of u proboscidea abundance at approximately 8 5 7 5 ma reflects significant upwelling at the equatorial divergence this event corresponds to the permanent build up of west antarctic ice sheets and a major increase in sw indian monsoons related upwelling in the northwestern indian ocean the chron 6 carbon shift at approximately 6 2 ma is marked by another peak of abundance reflecting widespread ocean fertility the highest abundances of u proboscidea and highest sediment accumulation rates occur between 5 8 and 5 1 ma which coincides with the greatest development of antarctic ice sheets and strong southwest monsoons the higher percentages at 3 2 3 1 ma approximately 2 4 ma and 1 6 ma all represent phases of high productivity at the equatorial divergence

late quaternary palaeoceanography of the tasman sea the benthic foraminiferal view abstract the benthic foraminiferal content of four gravity cores from the east tasman plateau 2450 m and 2667 m water depth and the lord howe rise 1349 m and 1448 m water depth was examined in order to determine late quaternary palaeoceanographic changes in the tasman sea in all cores benthic foraminifera demonstrate the glacial interglacial cyclicity through changes in assemblages and abundance abundances range from about 400 to 1200 specimens per gram of dry sediment over the last 400 kyr abundance patterns differ between the northern between 31 s and 33 s and the southern sites between 43 s and 44 s in the southern cores a significantly increased benthic foraminiferal abundance indicates high nutrient flux and quality perhaps continuously during stage 5 the northern cores on the other hand display this signal for stage 6 this reversed pattern is recognizable for other glacial episodes as well as for interglacials but the trend is less distinctive enhanced sea surface productivity in the tasman sea during the last glacial cycle is recognized from benthic foraminiferal assemblages but the pattern appears highly variable and complex the data suggest that for the past relocation of recent high productive oceanographic features sensu yoder et al 1994 in the tasman sea such as the tasman front the subtropical convergence the east australian current and perhaps the east australian eddy field tranter et al 1982 are reflected in the benthic formainiferal abundances in the cores increased foraminiferal abundance during glacials on the lord howe rise indicate a slight northward shift of the tasman front data from the east tasman plateau show a more complex situation the faunal pattern in the cores probably reflect a southward shift of the eddy field during glacials and a slight northward shift of the subtropical convergence during interglacials

linkage of north atlantic and southern ocean deep water circulation during glacial intervals the antarctic circumpolar current acc is one of the major current systems in the world ocean affecting circulation in all of the major ocean basins the acc flows eastwards around antarctica from the surface to 4 000 m depth with a transport on the order of 125 sverdrups1 deep sea benthic foraminifera from one piston core e49 18 from the south east indian ocean sector of the southern ocean were analysed to determine deep water mass circulation conditions within the acc during the late quaternary i report here that benthic foraminiferal faunal patterns closely match northern hemisphere ice volume changes shown by planktonic foraminiferal oxygen isotopic stratigraphy the glacial interglacial faunal oscillations are interpreted to reflect the presence of a deep water mass in the acc during glacial times which differs from modern circumpolar deep water i suggest that deep water circulation changes within the acc during the interval 440 000 to the present are directly linked to changes in north atlantic deep water nadw circulation

carbon and oxygen isotopic disequilibria of recent deep sea benthic foraminifera abstract the carbon and oxygen isotopic compositions of 149 samples of benthic foraminifera from deep sea core tops indicate that none of the nine species studied secrete calcium carbonate in isotopic equilibrium with ambient bottom water uvigerina pyrgo murrhina and oridorsalis tener are the closest to 18o equilibrium with average deviations about 0 4 while planulina wuellerstorfi and p murrhina are the closest to 13c equilibrium with average deviations about 1 p wuellerstorfi shows the most systematic relationship between 13c and bottom water apparent oxygen utilization the intraspecific variabilities in 18o and 13c suggest that estimates of bottom water paleotemperatures can be made to a precision of 0 7 c while estimates of past apparent oxygen utilization aou can be made to 35 mol kg based on intraspecific comparisons of the recent samples with fossils no temporal changes in the degree of either 18o or 13c disequilibrium have been detected for planulina wuellerstorfi uvigerina oridorsalis tener and globocassidulina subglobosa

late quaternary nannofossil indicators of climate change in two deep sea cores associated with the leeuwin current off western australia the stratigraphic variations in nannoflora observed in the two deep sea cores recovered from the offshore western australia revealed a sequence of paleoceanographic changes for the last 250 kyr the dominance of small placolith taxa in the upper photic flora indicates continuous mild upwelling for the isotope stages 7 5 in this region the most important controlling factor for the abundance variation of florisphaera profunda in this region is considered to be the lower photic temperature rather than the stability of water column or the water turbidity the significant reduction in the abundance of f profunda combined with the stable in the northern core rs96gc21 and reduced in the southern core rs9 150 abundance of the small taxa suggest an intensified upwelling for the penultimate glaciation the sharp increase in f profunda abundance indicates a weakening of upwelling at the last interglacial climax lic offshore western australia after isotope stage 5 the existence of upwelling is not clear except in stage 2 when it was not strong enough to produce blooms of emiliania huxleyi among the subordinate taxa calcidiscus leptoporus calciosolenia murrayi neosphaera coccolithomorpha and oolithotus fragilis provide meaningful paleoceanographic signals supporting the conclusions of previous studies a weakening or cessation of leeuwin current for the glacial periods the shift of dominance from small gephyrocapsa mostly g ericsonii to small reticulofenestra mostly r parvula can be an useful datum event offshore western australia the reduced diversity of nannoflora during the interglacial periods can be explained by a lessened competition within nannoplankton community caused by particularly favorable conditions for the opportunists such as e huxleyi f profunda and small placoliths the variations in nannofossil abundance suggests an increased aeolian flux at the stages 6 and 2 offshore north west cape as well as at stage 6 offshore southwestern australia

latest miocene pleistocene productivity and deep sea ventilation in the northwestern indian ocean deep sea drilling project site 219 knowledge of the biology of deep sea benthic foraminifera was used to interpret the results of multivariate analyses factor and cluster on relative abundance data of benthic foraminifera at deep sea drilling project site 219 southeastern arabian sea 1764 m depth in combination with carbon and oxygen isotope data faunal data document major changes in deep sea ventilation and productivity over the past 5 5 ma including the end of the miocene pliocene indo pacific biogenic bloom period at 4 0 ma interestingly there is no simple correlation between high productivity and low oxygenation productivity fluctuated but became overall more pulsed whereas overall oxygenation increased we interpret the records as a combination of local to regional fluctuations in productivity probably caused by changes in monsoonal development particularly its seasonality and changes in oxygenation of intermediate depth waters in the indian ocean caused by global changes in climate and ocean circulation

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

latest pliocene through holocene paleoceanography of the eastern indian ocean benthic foraminiferal evidence multivariate analyses of latest pliocene through holocene benthic foraminifera from 61 samples from deep sea drilling project dsdp site 214 eastern indian ocean were carried out the 46 highest ranked species were used in r mode factor analysis which has enabled to the identification of three environmentally significant assemblages at site 214 assemblage 1 is characterized by uvigerina hispido costata osangularia culter gavelinopsis lobatulus cibicides wuellerstorfi and karreriella baccata as principal species this assemblage is inferred to reflect high energy well oxygenated and probably low organic carbon deep sea environment at site 214 assemblage 2 is defined principally by globocassidulina pacifica and u proboscidea and is considered to indicate an organic carbon rich environment which resulted from high surface productivity irrespective of dissolved oxygen content assemblage 3 is marked by oridorsalis umbonatus textularia lythostrota hoeglundina elegans pyrgo murrhina and pullenia quinqueloba as principal species this assemblage is inferred to indicate a low organic carbon environment with high pore water oxygen concentration leading to better preservation of deep sea sediments

evidence for a bathyal front at 2000 m depth in the glacial pacific based on a depth transect on ontong java plateau data on oxygen and carbon isotope compositions of the benthic foraminifer planulina wullerstorfi from 18 cores 17 box cores and one piston core from ontong java plateau provide proxy depth profiles for temperature water mass and nutrient content for the late holocene the last transition and the last glacial the 18o profile during glacial time shows an increased gradient at a depth near 2000 m the corresponding 13c data suggest that a bathyal nutricline existed close to the same depth level the 13c values provide limits on the global change in carbon content of the glacial ocean which may be estimated as distinctly less than 1 atmospheric carbon mass 1 acm 700 gtc the greater co2 content of glacial deep waters which is reflected in the more negative 13c values may be at least in part due to a more sluggish renewal of abyssal deep waters if so the water of the deep pacific was up to 400 years older than now in turn ventilation in the upper waters above 2000 m may have been more vigorous than today

response of deep sea benthic foraminifera to late quaternary climate changes southeast indian ocean offshore western australia the late quaternary benthic foraminifera of four deep sea cores off western australia odp 122 760a odp122 762b bmr96gc21 and rc9 150 have been examined for evidence of increased surface productivity to explain the anomalously low sea surface paleotemperatures inferred by planktic foraminifera for the last and penultimate glaciations the 13c trends ofcibicidoides wuellerstorfi and differences between the 13c trends of planktics globigerinoides sacculifer and benthicsc wuellerstorfi in the four cores indicate that during stage 6 bottom waters were significantly depleted in 13c and strong 13c gradients were established in the water column while during stage 2 and the last glacial maximum 13c trends did not differ greatly from that of the holocene two main assemblages of benthic foraminifera were identified by principal component analyses one dominated byuvigerina peregrina another dominated byu proboscidea abundance of these uvigerinids and of taxa preferring an infaunal microhabitat and ofepistominella exigua andbulimina aculeata indicate that episodes of high influx of particulate organic matter were established in most sites during glacial episodes and particularly so during stage 6 while evidence for upwelling during the last glacial maximum is less strong the penultimate glaciation upwellings were established within the areas of low sea surface paleotemperature indicated by planktic foraminifera during the last interglacial climax upwelling appears to have been established in an isolated region offshore from a strengthened leeuwin current off north west cape last glacial maximum 13c values ofc wuellerstorfi at waterdepths of less than 2000 m show smaller than global mean glacial interglacial changes suggesting the development of a deep hydrological front a similar vertical stratification bathyal front was also established during the penultimate glaciation

review of paleoseismological and active fault studies in taiwan in the light of the chichi earthquake of september 21 1999 abstract this paper reviews the research on active and earthquake faults in taiwan conducted prior and after the 1999 chichi earthquake the chichi earthquake plays as a turning point of the relevant studies since the 1999 coseismic surface rupture exactly follows preexisting fault scarps created in turn by previous seismic events along the chelungpu fault this fact indicates that the precise mapping on the other active faults is fundamental to predict the location of surface rupture caused by large future earthquakes since 1999 many trenching studies have been carried out along the chichi earthquake fault a few of them demonstrates that the penultimate event is as young as probably only 200 430 years old however some others show a rather old age of several hundreds years or even older for the last faulting event before 1999 more trenching studies are necessary for such a long fault in order to understand the possible segmentation features and the correlation of the paleoseismic events identified along the entire fault length in addition we further discuss the offshore faulting associated with seismic event along the eastern coast of taiwan where the multiple holocene terraces are well known

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

core top evaluation of benthic foraminiferal isotopic ratios for paleo oceanographic interpretations abstract the benthic foraminifera cibicides wuellerstrofi oridforsalis tener and pyrgo rotalaria from twelve core tops in the norwegian greenland sea and c wuellerstorfi o tener and o umbonatus from four core tops on the rio grande rise were analysed for oxygen and carbon isotopes the norwegian greenland sea data yield statistically discrete means for both 18o and 13c for each species the interregional comparison of our data to published data from the east pacific rise shows that c wuellerstorfi 18o and 13c variations reflect oceanographic differences between sites whereas the data on oridorsalis and pyrgo do not we conclude that c wuellerstorfi is a reliable sensor of bottom water conditions whereas other taxa are of unproven utility supportive biological studies and the lack of positive covariance of 18o to 13c among deep sea benthic taxa lead us to reject models calling for incorporation of metabolic co2 to explain the isotopic variation among deep sea benthic foraminifera we propose a within sediment microhabitat hypothesis to explain the 13c variations among taxa

late quaternary deep ocean circulation a review of paleoceanographic studies dealing with late quaternary deep water circulation in the oceans is presented these studies which are based on the analysis of deep sea benthic foraminiferal faunal and geochemical data and sedimentological data are discussed in light of physical oceanographic conditions in the modern ocean we include in this review a re evaluation of benthic foraminiferal data from north atlantic and southern ocean piston cores and suggest that the dominance of uvigerina during glacial intervals reflects increased amounts of organic carbon at the sea floor compared to modern values a number of geochemical studies have suggested that the production or characteristics of north atlantic deep water nadw changed during glacial times although these changes have been thought to result from a cessation of overflow water from the norwegian greenland seas it is suggested here that seasonal sea ice cover was possible over southern portions of the norwegian sea during glacial intervals the presence of seasonally open water would have allowed norwegian sea overflow water to have been produced although perhaps at lower volumes and with different hydrographic properties than at present the record of antarctic bottom water aabw circulation does not show a simple relationship with paleoclimatic oscillations indicating that changes in oceanographic conditions in the southern ocean had little effect on aabw formation the aabw record contrasts with the glacial interglacial cycles of nadw suggesting no direct link between aabw and nadw circulation a variety of data suggests that changes in pacific deep water circulation occurred as a result of glacial production of north pacific deep water or from an increased flux of southern ocean water

tsunami sediments and their foraminiferal assemblages abstract tsunami hazard assessment begins with a compilation of past events that have affected a specific location given the inherent limitations of historical archives the geological record has the potential to provide an independent dataset useful for establishing a richer chronologically deeper time series of past events recent geological studies of tsunami are helping to improve our understanding of the nature and character of tsunami sediments wherever possible geologists should be working to improve the research tool kit available to identify past tsunami events marine foraminifera single celled heterotrophic protists have often been reported as present within tsunami deposited sediments but in reality little information about environmental conditions and by analogy the tsunami that deposited them has been reported even though foraminifera have an enormous capacity to provide meaningful palaeo environmental data here we review what foraminifera are describe their basic form and significance summarise where they have been reported in tsunami sediments and identify what can be learnt from them we review the gaps in our understanding and make recommendations to assist researchers who examine foraminiferal assemblages in order to enhance their use within tsunami geology

response of northern indian ocean deep sea benthic foraminifera to global climates during pliocene pleistocene abstract the northern indian ocean dsdp site 214 benthic foraminifera have been examined quantitatively to understand their response to the global climatic events and to determine the history of bottom water circulation in the northern indian ocean during pliocene pleistocene uvigerina spp cibicides kullenbergi c wuellerstorfi globocassidulina pacifica g subglobosa oridorsalis umbonatus and bulimina alazanensis are the dominant members of the benthic assemblage and reveal significant changes in distribution patterns based on benthic foraminiferal frequency changes four intervals of major faunal and climatic turnover have been recognized at 5 2 5 1 ma 3 9 3 2 ma 3 2 3 1 ma and 3 1 0 6 ma the interval between 5 2 5 1 ma is marked by widespread antarctic glaciation deep sea hiatuses bottom water cooling increased upwelling high sedimentation rates highest uvigerina abundances and intensified bottom water circulation during 3 9 3 2 ma the bottom waters were warmer and bottom water activity waned with a sharp decline in uvigerina abundance and increase in cibicides the interval between 3 2 3 1 ma was a time of bottom water cooling and coincides with a global benthic positive oxygen isotopic shift antarctic ice volume increase and possible initiation of northern hemisphere glaciation the late pliocene and pleistocene interval 3 1 recent is punctuated by major changes in benthic foraminiferal assemblages warm cold cycles major glacial interglacial intervals increase in polar ice volume and intensification of upwelling on the basis of cumulative percentages of uvigerina and cibicides nine intervals of major bottom water cooling have been inferred in the pliocene and two in the pleistocene at site 214 reflecting the major changes in bottom water circulation

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

large scale reorganization of ocean currents offshore western australia during the late quaternary abstract the history of coastal surface currents in the eastern indian ocean over the last 130 kyr has been studied through the application of the fi 2 transfer function to planktic foraminifera in deep sea cores in a n s transect offshore western australia the concept of sea surface temperature sst gradient residuals is the amount by which the sea surface temperature gradient of a given time differs from that in the modern sea the sst gradient residuals for several episodes of climate extremes in the late quaternary the last glacial maximum 20 kyr b p the last interglacial maximum 122 120 kyr b p and at the end of the penultimate glaciation 130 kyr b p indicate that areas north of 18 s off western australia have changed very little during the extremes in climate over the last 130 kyr while south of 18 s there have been significant changes in surface water temperatures large areas of anomalously cool surface water were established off north west cape 22 s 24 s during both glacial and interglacial extremes these reflect the increased influence of the west australian current on the surface water circulation during the last glacial maximum and at the end of the penultimate glaciation cold sea surface temperature anomalies were established near to the coast indicating that the leeuwin current did not warm the coastal zone as it does today during the last interglacial maximum the leeuwin current flowed as an intensified current in a narrow zone close to the coast but did not significantly warm surface waters offshore as far as 20 25 s where a zone of cold water was maintained