oxygen and carbon isotope record of east pacific core v19 30 implications for the formation of deep water in the late pleistocene north atlantic abstract a detailed oxygen and carbon isotope record has been obtained from benthic foraminifera in core v19 30 from the carnegie ridge on the south side of the panama basin expressing these records and the oxygen and carbon isotope records previously published for atlantic core m 12392 on a common timescale it is apparent that the oxygen isotope records are very similar but that the carbon isotope records are quite different by obtaining the carbon isotope gradient between the two sites as a function of time we show that the production of north atlantic deep water has varied over a wide range during the late pleistocene and that the pattern of variation is not simply related to the well known oxygen isotope record although the two oxygen isotope records are very similar changes in the interoceanic gradient are detectable and support the hypothesis that in the glacial mode the north atlantic was colder and less oxygenated than it is today shackleton s 1 1977 interpretation whereby the carbon isotope record from the atlantic core reflects changes in the terrestrial biomass is an over simplification however the record from the pacific core v19 30 probably can be explained in these terms since it probably approximates the carbon isotope record of global mean oceanic dissolved co 2

gulf stream variability during marine isotope stage 3 we have studied ocean drilling program site 1060 on the blake outer ridge which lies beneath the gulf stream we focus on marine isotope stage 3 60 25 thousand years before present ka sea surface temperatures ssts inferred both from foraminiferal fauna and alkenone ratios as well as counts of iceberg melt out debris and benthic stable isotope analyses enable our record to be interpreted in terms of regional hydrographic changes as well as changing thermohaline circulation thc the observed sst record is consistent with the air temperature record from the greenland ice cores however site 1060 exhibits important differences in detail compared with the ice core record and when compared to other sites within the north atlantic significant longitudinal differences emerge at site 1060 in the western atlantic all greenland stadials gs whether associated with heinrich events hes or not show a similar small amplitude of cooling mean faunal based sstaug during gs is only 1 5 c colder than during greenland interstadials gis in addition during gs the coldest ssts are limited to apparently brief events this is in contrast to several eastern atlantic sites where he stadials exhibit coolings that are enhanced by 2 c compared to other gs and where cold conditions are not restricted to cold pulses but cover 2 ka long intervals furthermore site 1060 ssts remained warm right through each interstadial in contrast to the sustained and uniform cooling trend through interstadials that is consistently observed in greenland indicated by measurements of 18o in ice

tracing seafloor methane emissions with benthic foraminifera in the baiyun sag of the northern south china sea changes in the concentrations of atmospheric greenhouse gases are an important part of the global climate forcing the hypothesis that benthic foraminifera are useful proxies of local methane emission from the seafloor has been verified on sediment cores by numerous studies the calcium carbonate caco3 content and the high resolution carbon and oxygen isotope composition of the benthic foraminifera from the core 08cf7 from the northeastern shenhu gas hydrate drilling area in the baiyun sag of the northern south china sea were analyzed and the benthic foraminifera s evidence for methane release from gas hydrate decomposition are presented here for the first time two rapid obvious carbon isotope negative excursions were observed in the oxygen isotope stage boundaries 5d 5c and 6 5e penultimate deglaciation about 130 ka of the cold to warm climatic transition period the largest negative value of 13c is about 2 95 and the whole change of carbon and oxygen isotope is strikingly similar and is in consonance with the atmospheric methane concentration recorded by the vostok ice core and the carbon isotopic record from lake baikal combining these results with the analysis of the geological conditions of the study area and the fact that gas hydrate exists in the surrounding area it can be concluded that the carbon isotope negative excursions of the benthic foraminifera in the northern south china sea are associated with methane release from gas hydrate decomposition due to deglacial climate warming by recording the episodes of massive gas hydrate decomposition closely linked with the northern hemisphere temperatures during major warming periods the new 13c record from the baiyun sag provides further evidence for the potential impact of gas hydrate reservoir on rapid deglacial rises of atmospheric methane levels

interstadial records of the last glacial period at pantai remis malaysia two eustatic high sea stands during the last glacial period are recognised at pantai remis these highstands lower than present day sea level are tropical manifestations of the ameliorating interstadial climate during the weichselian devensian wisconsin glaciation in the northern hemisphere the earlier highstand corresponds to a sea level of 14 6 m below mean sea level msl it is interpreted as synchronous with oyxgen isotope stage 5a and is correlated with other known sea level curves in other parts of the world the younger high sea stand dated 55810 1140 to 53870 1400 yr bp indicates sea level of 4 3 m below msl it represents an interstadial equivalent that lasted for at least 2000 yr whereas the earlier interstadial period indicates a minimum duration of twice this amount or very likely even longer as reflected from the thickness of the accumulated deposits the palynological records indicate that during interstadial times climatic stability in the tropics is attained and was sufficiently long for vegetation to thrive and develop the palynofloral constituents of the earlier interstadial phase at pantai remis showed the establishment of vegetation in a coastal setting initiated by pandanus swamp forests simultaneously mangrove swamp flourished in the lower lying parts of the area hence the presence of direct tidal influence is evident both the pandanus and mangrove swamps were succeeded by mixed freshwater swamp forests of a campnosperma calophyllum assemblage subsequently a slightly open and somewhat drier mixed swamp forest prevailed marked by the increase in fern spore representation the later interstadial phase showed shorter vegetation successions which commenced on the landward edge of a mangrove swamp forest the mangrove was successively replaced by strand forest as indicated by domination of casuarina equisetifolia the palynological assemblages in both the interstadial periods indicate similarity to the present day coastal vegetation this implies that during the interstadials the climate in the lowlands of peninsular malaysia and presumably throughout the equatorial region was as that prevailing today 1997 john wiley sons ltd

paleoceanography of the east equatorial pacific over the past 16 myr and pacific atlantic comparison high resolution benthic foraminiferal δ18o and δ13c records at iodp site u1337 abstract we present astronomically tuned high resolution 3 4 kyr 15 8 myr long benthic foraminiferal 18 o and 13 c records from iodp site u1337 in the east equatorial pacific which provide a reference standard for stratigraphic correlation of deep sea sediments a long term glaciation history over the past 15 8 myr has been recorded in the 18 o two of the most significant glaciation events include the east antarctic ice sheet expansion eaie at 13 8 ma and the final onset of the northern hemisphere glaciation nhg in 3 3 2 5 ma a series of miocene and pliocene glaciation events exist between the eaie and nhg which are important glaciation attempts before the earth finally entered the full icehouse world in the late pleistocene a long term ocean carbon isotope decrease over the past 15 8 myr has been recorded in the 13 c ocean circulation change was the major cause of the ocean carbon isotope decrease in 9 4 8 1 ma and 4 0 ma whereas strengthened continental chemical weathering controlled the long term ocean carbon isotope decrease in most of the time of the past 15 8 myr the divergence in benthic foraminiferal 13 c and end provides strong evidence of significant ocean circulation change between 12 1 and 9 2 ma which was probably related to the formation of the isthmus of panama the internal feedbacks such as continental weathering and sea surface temperature change have great potential for modulating the weak 100 and 400 kyr signals in astronomical forcing into strong 100 and 400 kyr signals in global ice volume and carbon cycle

synchronous high frequency oscillations in tropical sea surface temperatures and north atlantic deep water production during the last glacial cycle stable isotopic measurements of g sacculifer and c wuellerstorfi in a core from the western equatorial atlantic imply that there are parallel suborbital oscillations in surface water hydrography and deep water circulation occurring during oxygen isotope stages 2 and 3 low values of g sacculifer 18o accompany high values of c wuellerstorfi 13c linking warmer sea surface temperatures ssts in the tropics with increased production of lower north atlantic deep water nadw the amplitude of the 18o oscillations is 0 6 or 2 3 c which is superimposed on a glacial interglacial amplitude of about 2 1 using the g sacculifer 18o data we calculate that surface waters were colder during stage 2 than calculated by climap 1976 1981 the longer period 2 kyr oscillations in air temperature recorded in the greenland and antarctic ice cores appear to correlate with oscillations in sea surface temperature in the equatorial atlantic the magnitude of these oscillations in tropical sst is too large to have resulted from changes in meridional heat transport caused by the global conveyor alone the apparent synchroneity of equatorial sst and polar air temperature changes as well as the amplitude of the sst changes at the equator are consistent with the climate effects expected from changes in the atmosphere s greenhouse gas content h2ovapor co2 and ch4

astronomically tuned plio pleistocene benthic δ 18 o record from south china sea and atlantic pacific comparison based on benthic foraminiferal n 18 o from odp site 1143 a 5 myr astronomical timescale for the west pacific plio pleistocene was established using an automatic orbital tuning method the tuned brunhes matuyama paleomagnetic polarity reversal age agrees well with the previously published age of 0 78 ma the tuned ages for several planktonic foraminifer bio events also agree well with published dates and new ages for some other bio events in the south china sea were also estimated the benthic n 18 o from site 1143 is highly coherent with the earth s orbit etp both at the obliquity and precession bands for the last 5 myr and at the eccentricity band for the last 2 myr in general the 41 kyr cycle was dominant through the plio pleistocene although the 23 kyr cycle was also very strong the 100 kyr cycle became dominant only during the last 1 myr a comparison of the benthic n 18 o between the atlantic odp 659 and the east and west pacific 846 and 1143 reveals that the atlantic pacific benthic oxygen isotope difference ratio vn 18 oatlpac displays an increasing trend in three time intervals 3 6 2 7 ma 2 7 2 1 ma and 1 5 0 25 ma each of the intervals begins with a rapid negative shift in vn 18 oatlpac followed by a long period with an increasing trend corresponding to the growth of the northern hemisphere ice sheet this means that all three intervals of ice sheet growth in the northern hemisphere were accompanied at the beginning by a rapid relative warming of deep water in the atlantic as compared to that of the pacific followed by its gradual relative cooling this general trend superimposed on the frequent fluctuations with glacial cycles should yield insights into the processes leading to the boreal glaciation cross spectral analyses of the vn 18 oatlpac with the earth s orbit suggests that after the initiation of northern hemisphere glaciation at about 2 5 ma obliquity rather than precession had become the dominant force controlling the vertical structure or thermohaline circulation in the paleo ocean a 2002 elsevier science b v all rights reserved

distribution age and deformation of late pleistocene marine terraces at mahia peninsula hikurangi subduction margin new zealand a sequence of seven marine terraces of late pleistocene age constitutes approximately 40 of the area of mahia peninsula in eastern north island the peninsula is one of the closest land areas to the hikurangi trough approximately 80 km further east where the pacific plate is being subducted beneath the australian plate terrace ages of 40 59 81 106 124 176 and 212 ka are assigned by correlation with the marine terrace sequence of huon peninsula papua new guinea paleontological data and amino acid dating of marine components of the 124 ka terrace at mahia peninsula provide a basis for correlation to the huon peninsula sequence loess and tephra stratigraphy constrain the ages of older and younger terraces the marine terrace sequence is tilted to the wnw on the flank of the nne trending lachlan anticline uplift of at least 130 m of the circa 124 kyr old shoreline indicates uplift rates of at least 1 mm yr at the axis of the anticline younger marine terraces have been uplifted more rapidly about 3 mm yr and there is a progressive increase in rate to the youngest holocene shoreline structural contours normalized to the circa 124 ka terrace illustrate the tilt on the flank of the lachlan anticline and on a secondary structure the aurora point fold seismic profiling has confirmed the presence of a reverse fault the lachlan fault at the eastern margin of the lachlan anticline the lachlan fault is inferred to be responsible for growth of the anticline and deformation of the marine terraces the relationship of the reverse fault to the subduction thrust which separates the two crustal plates at about 20 km depth below mahia peninsula and dips about 6 12 to the nw is uncertain however the late pleistocene and holocene growth of the lachlan anticline indicates substantial coupling across the plate interface deforming the inner part of the frontal wedge of the australian plate

paleocene oceanography of the eastern subtropical indian ocean an integrated magnetobiostratigraphic and stable isotope study of odp hole 761b wombat plateau surface and deep water circulation patterns in the eastern indian ocean during the paleocene epoch are inferred based on an integrated magnetobiostratigraphic and stable isotope investigation of ocean drilling program hole 761b drilled on the wombat plateau a combination of magnetostratigraphy biostratigraphy and isotope stratigraphy demonstrates that numerous deep sea sites that have been considered to show continuous or nearly continuous sedimentation through the paleocene are punctuated by a series of hiatuses some of which exceeding a duration of 1 myr therefore our study is based on a detailed temporal interpretation of the stratigraphic successions we used for paleoceanographic reconstructions we compare detailed planktonic and benthic foraminiferal carbon and oxygen isotope records from hole 761b with several temporally correlative records published from different oceanic provinces in order to distinguish between local and global patterns within the eastern indian ocean although site 761 was situated at low latitudes during the paleocene its surface waters were predominantly influenced by circulation originating from the southern ocean as indicated by inferred cool sea surface temperatures and reduced surface to deep water temperature gradients we suggest that deep waters in the eastern indian ocean were not directly fed by the southern or tethys oceans rather the more negative n 13 c composition of the bottom waters recorded by benthic foraminifera implies the presence and or active contribution of aged deep waters from the pacific during this time at least prior to v60 2 ma and subsequent to v59 0 ma the indian continent ninetyeast ridge kerguelen plateau and broken ridge may have played a significant role as submarine barriers to deep water circulation during the paleocene 2002 elsevier science b v all rights reserved

the middle pleistocene transition characteristics mechanisms and implications for long term changes in atmospheric pco2 abstract the emergence of low frequency high amplitude quasi periodic 100 kyr glacial variability during the middle pleistocene in the absence of any significant change in orbital forcing indicates a fundamental change internal to the climate system this middle pleistocene transition mpt began 1250 ka and was complete by 700 ka its onset was accompanied by decreases in sea surface temperatures ssts in the north atlantic and tropical ocean upwelling regions and by an increase in african and asian aridity and monsoonal intensity during the mpt long term average ice volume gradually increased by 50 m sea level equivalent whereas low frequency ice volume variability experienced a 100 kyr lull centered on 1000 ka followed by its reappearance 900 ka although as a broad band of power rather than a narrow persistent 100 kyr cycle additional changes at 900 ka indicate this to be an important time during the mpt beginning with an 80 kyr event of extreme sst cooling followed by the partial recovery and subsequent stabilization of long term north atlantic and tropical ocean ssts increasing southern ocean sst variability primarily associated with warmer interglacials the loss of permanent subpolar sea ice cover and the emergence of low frequency variability in pacific ssts and global deep ocean circulation since 900 ka ice sheets have been the only component of the climate system to exhibit consistent low frequency variability with the exception of a near universal organization of low frequency power associated with marine isotope stages 11 and 12 all other components show an inconsistent distribution of power in frequency time space suggesting a highly nonlinear system response to orbital and ice sheet forcing most hypotheses for the origin of the mpt invoke a response to a long term cooling possibly induced by decreasing atmospheric pco2 none of these hypotheses however accounts for the geological constraint that the earliest northern hemisphere ice sheets covered a similar or larger area than those that followed the mpt given that the mpt was associated with an increase in ice volume this constraint requires that post mpt ice sheets were substantially thicker than pre mpt ice sheets indicating a change in subglacial conditions that influence ice dynamics we review evidence in support of the hypothesis that such an increase in ice thickness occurred as crystalline precambrian shield bedrock became exposed by glacial erosion of a thick mantle of regolith this exposure of a high friction substrate caused thicker ice sheets with an attendant change in their response to the orbital forcing marine carbon isotope data indicate a rapid transfer of organic carbon to inorganic carbon in the ocean system during the mpt if this carbon came from terrigenous sources an increase in atmospheric pco2 would be likely which is inconsistent with evidence for widespread cooling apparently rapid carbon transfer from terrestrial sources is difficult to reconcile with gradual erosion of regolith a more likely source of organic carbon and nutrients which would mitigate pco2 rise is from shelf and upper slope marine sediments which were fully exposed for the first time in millions of years in response to thickening ice sheets and falling sealevels during the mpt modeling indicates that regolith erosion and resulting exposure of crystalline bedrock would cause an increase in long term silicate weathering rates in good agreement with marine sr and os isotopic records we use a carbon cycle model to show that a post mpt increase in silicate weathering rates would lower atmospheric pco2 by 7 12 ppm suggesting that the attendant cooling may have been an important feedback in causing the mpt

comparison of atlantic and pacific paleochemical records for the last 215 000 years changes in deep ocean circulation and chemical inventories abstract detailed cd ca and 13 c data have been obtained for benthic foraminifera from western north atlantic and equatorial pacific sediment cores in the modern ocean both tracers are closely linked to nutrient distributions the sedimentary records for both tracers indicate that bottom waters overlying the atlantic site have been nutrient depleted relative to those at the pacific site over the last 215 000 years from this evidence it is reasonable to infer that there has been a continuous net flux of nutrient depleted water from the western north atlantic into the pacific this exchange has undergone significant fluctuations with the export of nutrient depleted atlantic water diminishing by about a factor of two relative to the inflow from southern ocean sources over the last 215 000 years carbon isotope fluctuations in both regions are dominated by variable storage of isotopically light carbon on continents with a lesser contribution from these deep ocean circulation changes the cadmium signal in the north atlantic is dominated by changes in deep ocean circulation patterns cadmium shows less variability in the pacific which may reflect changes in the global average cadmium content or minor changes in deep pacific circulation patterns using these records to estimate global averages it appears that glacial ocean water had 22 more cd and 0 46 less 13 c than the modern ocean these numbers are estimates which may be revised as more data become available although they are not likely to be as much as 20 in error for cd or 0 2 for 13 c relative north atlantic deep water nadw formation rates are modulated with a significant 41 kyr periodicity linked to obliquity induced variations in high latitude insolation nadw lags 8 2 kyr behind insolation however

subsidence of the northern south china sea and formation of the bashi strait in the latest miocene paleoceanographic evidences from 9 myr high resolution benthic foraminiferal δ 18 o and δ 13 c records abstract we present astronomically tuned high time resolution 3 4 kyr benthic foraminiferal 18o and 13c records between 9 ma and 5 ma from ocean drilling program odp site 1143 in the southern south china sea scs we found that the late miocene ocean carbon shift lmocs which was linked with the late miocene early pliocene biogenic bloom also occurred in the northern and southern scs a marked deep water 13c gradient as much as 1 0 of the northern and southern scs was observed between 6 5 ma and 5 9 ma which was probably caused by the significant difference in paleoproductivity between the northern and southern scs the deep 13c gradient was likely produced by rapid tectonic subsidence in the northern scs at 6 0 ma and the final formation of the bashi strait at 6 5 ma a reversed benthic 13c gradient of the northern and southern scs was also observed between 1 2 ma and 0 35 ma which was probably caused by the consecutive closures of the interarc water gates within the bashi strait at 3 0 ma and 1 2 ma closures of the interarc water gates within the bashi strait at 3 0 ma and 1 2 ma further semi enclosed the scs basin and made the paleoproductivity the major factor influencing the deep water 13c leading to the reversed deep water 13c gradient of the northern and southern scs between 1 2 ma and 0 35 ma

history of atmospheric co2 constraints from the deep sea record the carbon chemistry of deep ocean water is quantitatively reflected in carbonate preservation and in the 13c values of foraminifera by using benthic 13c ranges to estimate total dissolved co2 and correcting for the aging effect of deep water back aging the pco2 of the atmosphere can be reconstructed data at hand are insufficient for detailed studies but allow the calculation of an upper limit of pco2 for selected periods within the last 100 million years the limit is probably near a factor of 2 5 times present atmospheric co2 for post eocene time and below a factor of 10 for the late cretaceous

paleoclimate history of galapagos surface waters over the last 135 000 yr abstract records of planktonic and benthic foraminiferal 18 o and planktonic mg ca from core tr163 22 just northwest of the galapagos islands reveal a detailed 250 450 year resolution climate history of the region over the last 135 thousand years kyr sea surface temperatures ssts reconstructed from g ruber mg ca averaged 24 3 0 4 c during the holocene 22 6 0 6 c during marine isotope stage mis 2 3 and 4 and 26 0 0 9 c during mis 5e changes in sst lead changes in both planktonic and benthic 18 o by an average 3 kyr suggesting that sst changes in this region predated continental ice volume changes changes in sst display clear millennial scale variability especially in marine isotope stage 3 with behavior somewhat similar to antarctic proxy air temperature and south pacific sst records removal of the temperature component from the planktonic 18 o record demonstrates that glacial interglacial 18 o water changes at this site were 1 0 0 2 similar to estimates for mean ocean shifts implying that salinity changes due to regional hydrological variation between the last glacial maximum and holocene in the galapagos region were minimal comparison between the tr163 22 sst record and an sst record from core tr163 19 north of the equatorial front reveals a largely similar broad scale climate history suggesting that changes in the galapagos region were caused by large scale forcing rather than by local or regional dynamical changes changes in atmospheric greenhouse forcing are the most plausible explanation for the observed large scale climate changes in the eastern equatorial pacific

constraints on the ocean oxygen isotopic enrichment between the last glacial maximum and the holocene paleoceanographic implications abstract we review the various methods which have been applied to estimate the change of seawater 18 o w between the last glacial maximum lgm and the holocene the most accurate constraints on these estimates are provided by the measurement of pore waters 18 o and by high resolution records of benthic foraminifer 18 o in the high latitude oceans of both hemispheres they show that the 18 o of seawater in the deep ocean during the lgm was 1 05 0 20 heavier than today with significant regional variations constraints resulting from ice sheet models are less accurate because both the volume and isotopic composition of each ice sheet are still poorly known the amplitude of the benthic 18 o change between the lgm and the holocene together with the 18 o and 13 c values of the benthic foraminifera genus cibicides during the lgm show that the southern ocean deep waters were extremely cold close to the freezing point during this time deep waters of the south atlantic and the pacific oceans were at least 1 3 c warmer than those of the southern ocean overall the glacial deep ocean below 2500 m was characterized by extremely cold temperatures everywhere lower than 0 c 18 o values of benthic foraminifer from the north atlantic are highly variable this variability suggests that deep atlantic waters were not homogeneous probably because they resulted from the sinking of different surface water masses at various locations during winter the deep waters in the north atlantic were at most 2 c warmer than in southern ocean alternatively they could have been nearer the freezing point with a 18 o value lighter than the mean ocean water brine formation during winter would preserve such light 18 o values of the northern north atlantic surface water

uranium series dating of marine and lacustrine carbonates of the possible uranium series dating schemes the most important and most widely applied to marine carbonates is 230th dating with 231pa dating playing an increasingly important role for this reason this review will focus on these two methods 230th dating also referred to as u th dating or 238u 234u 230th dating involves calculating ages from radioactive decay and ingrowth relationships among 238u 234u and 230th 232th is also typically measured as a long lived essentially stable index isotope over the time scales relevant to 230th dating at present 230th dating can in principle be used to date materials as young as 3 years and in excess of 600 000 years edwards et al 1987a 1993 edwards 1988 see stirling et al 2001 for an example of dating corals in excess of 600 000 years old 231pa dating also referred to as u pa dating involves calculating ages from the ingrowth of 231pa from its grandparent 235u at present 231pa dating can be used to date materials as young as 10 years and as old 250 000 years edwards et al 1997 230th dating covers all of the 231pa time range and more with somewhat higher precision and is therefore the method of choice if a single method is applied however the combination of 231pa and 230th dating is of great importance in assessing possible diagenetic mobilization of the pertinent nuclides and thereby the accuracy of the ages allegre 1964 ku 1968 even if the primary age exceeds the 250 000 year limit of 231pa dating the combined methods can be used to assess the degree to which the samples have remained closed over the past 250 000 years e g edwards et al 1997 thus

geologic time series from deep sea sediments time scales and distortion by bioturbation abstract in order to evaluate the time and frequency domain characteristics of geologic time series obtained from deep sea sediments two important problems must be considered first an accurate time scale must be established for the sediment records to be studied an accurate time scale is a basic requirement for such techniques as spectral and cross spectral analysis secondly the distortion of a geologic time series by sedimentation processes such as bioturbation must be considered if inferences are to be made about the mechanisms controlling climatic and oceanographic processes reflected in the geologic record recently it has been suggested that the periodic components in paleoclimatic records which can be related to variations in the earth s orbital parameters can be used as a means for providing very detailed control for late pleistocene sediment sections a time scale is estimated by tuning an individual frequency component in a climate record to an orbital parameter the tuning procedure commonly uses the technique of bandpass filtering which removes all frequency components except the one equivalent to an orbital parameter and then adjusting the geologic time scale so that the filtered record and orbital record align since bandpass filtering will produce a periodic record from any data set a question is raised as to the circularity of this tuning approach a series of numerical experiments using synthetic time series are used to determine if the tuning of a geologic record artificially induces improved correlation and increased periodic character in a climatic record these experiments indicate that the tuning does not artificially induce these effects thus it is suggested that the careful use of orbital tuning provides a powerful means of defining a geologic time scale the degree to which bioturbation distorts a paleoclimatic record is studied by comparing the spectra of oxygen isotopic records obtained from cores with sedimentation rates ranging from 1 to 12 cm 1000 yr 1 it is shown that the systematic change in the variance spectra of these records that is predicted by models of bioturbation cannot be observed for sedimentation rates greater than 2 cm 1000 yr 1 this can be explained in part if bioturbation is a function of sedimentation rates if this is the case then bioturbation must proceed to depth of tens to hundreds of centimeters however it seems likely that the degree to which bioturbation alters the climate signal preserved in deep sea sediment cores has been overestimated

possible triggering of heinrich events by ice load induced earthquakes north atlantic sediments dating from the last ice age contain layers of rock fragments from northeastern canada so called heinrich layers 1 like modern iceberg borne sediments from greenland these layers have been attributed to ice rafting episodes1 2 3 six heinrich layers have been documented and correlated with climate changes4 5 6 7 8 the layers which are several centimetres thick contain negligible amounts of foraminifera which accumulate at a few millimetres per century implying that they were deposited over just a few years these ice rafting heinrich events are separated by progressively shorter intervals from about 40 to 6 kyr ref 9 and it has been suggested10 that they are related to the milankovitch cycles in the earth s orbital parameters11 alternatively they may be generated by forcing mechanisms arising from the internal dynamics of the laurentide ice sheet12 here we suggest the possibility that the heinrich events were precipitated by ice load induced earthquakes analogous to those produced by reservoir water loads13 we suggest that near its edge the laurentide ice sheet sheared the earth s crust inducing repeated failure that released the ice rafts this region along canada s northeastern seaboard shows evidence of both current14 15 and past seismic activity owing to postglacial rebound our model accounts for the intervals between both the heinrich events and the evidence of palaeoseismicity and can be tested by studying local sedimentary relationships

response of deep ocean circulation to initiation of northern hemisphere glaciation 3 2 ma carbon isotopic records from benthic foraminifera are used to map patterns of deep ocean circulation between 3 and 2 million years ago the interval when significant northern hemisphere glaciation began the 18o and 13c data from four atlantic sites 552 607 610 and 704 and one pacific site 677 show that global cooling over this interval was associated with increased suppression of north atlantic deep water nadw formation however the relative strength of nadw production was always greater than is observed during late pleistocene glaciations when extreme decreases in nadw are observed in the deep north atlantic our data indicate that an increase in the equator to pole temperature gradient associated with the onset of northern hemisphere glaciation did not intensify deepwater production in the north atlantic but rather the opposite occurred this is not unexpected as it is the warm high salinity characteristic rather than the low temperature of thermocline waters that is critical to the deepwater formation process in this region today

atlantic mediterranean water exchange during the late neocene the nature of water exchange between the mediterranean and the atlantic is examined for three time periods during the late neogene in order to assess the impact of flow patterns between these basins on bottom water conditions in the oceans the large volume of carbonates and evaporites deposited in the mediterranean during the messinian salinity crisis appears to have caused the open ocean to become more undersaturated in calcium carbonate resulting in increased dissolution of deep sea carbonates during the latest miocene during the earliest pliocene an estuarine type of flow existed between the atlantic and mediterranean waters entered the mediterranean at depth and flowed out at the surface benthic foraminiferal stable isotopic evidence from the north atlantic indicates that north atlantic deep water nadw was produced throughout the early pliocene and that the absence of saline mediterranean outflow did not have a significant effect on bottom water production eustatic lowering of sea level during the last glacial maximum 18 000 years b p reduced water exchange between the atlantic and the mediterranean as a result salinities in the mediterranean increased substantially but it seems unlikely that diminished nadw production during the last glacial episode can be attributed to a reduction in mediterranean outflow

glacial interglacial changes in global deepwater circulation variations in the areal extent of the cryosphere appear to exert an important control over glacial interglacial changes in the mode of formation and source areas for deepwater and bottom water masses during interglacials when ice extents are minimal these water masses form by mechanisms which are well documented for the present interglacial climatically related advances and retreats of sea ice in the northern hemisphere during glacials probably resulted in shifting loci of formation for each of the three types of north atlantic deep water nadw probable glacial advances of grounded ice sheets to the continental shelf margins in antarctica precluded formation of antarctic bottom water aabw at the presently active continental shelf sites because these shifts in source areas for aabw and nadw probably involved source waters with salinity temperature oxygen content and nutrient levels that differed from modern values deep and bottom waters are likely to have had different characteristics in glacials than they do during interglacials

oxygen isotopes sea level changes and the temperature history of a coral reef environment in new guinea over the last 105 years abstract coral reef terraces consisting of an upward succession of fringing and barrier reef types are preserved on land along the raising coast of huon peninsula new guinea seven coral reef units i vii from the coast landwards spaced at about 20 kyr interval provide a rather complete record of sea levels oxygen isotopes and temperature of teh surface tropical ocean over the duration of the high sea level events of the last glacial cycle the systematic sampling of the coral reefs was restricted to the massive tridacna gigas species the giant clam which are about 0 7 0 enriched in 18o relative to calcite equilibrium value and the presence of symbionts seems to have no effect on the 18o of their aragonitic skeleton sea levels rose rapidly to 5 6 5 m above present during the last interglacial which on stratigraphic grounds and 18o compositions can be separated into an early phase whose 18o is similar to modern reef viia dated at 138 kyr and a late phase that is 0 6 0 heavier reef viib dated at 118 kyr fringing reefs vi v iv iii and ii record short lived high sea levels stands at 107 85 60 45 to 40 and 31 kyr respectively that stopped short of the present sea level 12 19 28 32 to 42 m the general decline of the high sea level stands corresponds to an average 18o enrichment of 1 7 0 measured between the early interstadials of isotope stage 5 vi and v and the late interstadials of isotope stage 3 iv iiia iiib and ii the maximum 18o enrichment of 1 7 0 relative to present was registered during a regressive phase of reef iiia stratigraphic evidence indicates that sea level lows in the range of 37 to 55 m below present have occurred in between the high sea level stands but those are unlikely to represent the lowest sea levels of the last glacial cycle sea levels and 18o ddta pair offer important clues regarding the partitioning of ice volume and temperature in 18o records the results suggest that the ice volume effect accounts for the observed 18o changes during the early interstadial culminations but only for 29 46 during the late interstadial culminations sea water cooling beyond the threshold limit of coral reef growth 18 c did not occur during the last glacial cycle the temperature of the surface tropical ocean was similar to present during the early interstadials of isotope stage 5 and cooler by 3 c below present during the later interstadials of isotope stage 3

stable isotopes in late middle eocene to oligocene foraminifera oxygen and carbon isotope ratios in eocene and oligocene planktonic and benthic foraminifera have been investigated from atlantic indian and pacific ocean locations the major changes in eocene oligocene benthic foraminiferal oxygen isotopes were enrichment of up to l in 18o associated with the middle late eocene boundary and the eocene oligocene boundary at locations which range from 1 to 4 km paleodepth although the synchronous eocene oligocene 18o enrichment began in the latest eocene most of the change occurred in the earliest oligocene the earliest oligocene enrichment in 18o is always larger in benthic foraminifera than in surface dwelling planktonic foraminifera a condition that indicates a combination of deep water cooling and increased ice volume planktonic foraminiferal 18o does not increase across the middle late eocene boundary at our one site with the most complete record deep sea drilling project site 363 walvis ridge this pattern suggests that benthic foraminiferal 18o increased 40 m y ago because of increased density of deep waters probably as a result of cooling although glaciation cannot be ruled out without more data stable isotope data are averaged for late eocene and earliest oligocene time intervals to evaluate paleoceanographic change average 18o of benthic foraminifera increased by 0 64 from the late eocene to the early oligocene 18o maximum whereas the average increase for planktonic foraminifera was 0 52 this similarity suggests that the eocene oligocene boundary 18o increase was caused primarily by increased continental glaciation coupled with deep sea cooling by as much as 2 c at some sites average 18o of surface dwelling planktonic foraminifera from 14 upper eocene and 17 lower oligocene locations when plotted versus paleo latitude reveals no change in the latitudinal 18o gradient the oligocene data are offset by 0 45 also believed to reflect increased continental glaciation at present there are too few deep sea sequences from high latitude locations to resolve an increase in the oceanic temperature gradient from eocene to oligocene time using oxygen isotopes

late pleistocene holocene radiolarian and pollen records from sediments in the sea of okhotsk in two cores with oxygen isotope stratigraphy from the southern okhotsk sea marine pollen and siliceous microfauna record concurrent late glacial through holocene variations in regional terrestrial and marine environments glacial vegetation around the southern okhotsk basin which resembles the present tundra steppe of the northwest coast of this marginal sea yields to spruce dominated boreal forests during the glacial interglacial transition temperate forest components such as oak peak during the mid holocene decreasing oak accompanied by increasing spruce reflects the effect of global cooling on local vegetation during the last 4 kyr although the radiolarian fauna in the okhotsk sea samples is similar to that present in the northwest pacific the dominant species in both regions differ concentrations of radiolarians are low in latest glacial samples with higher concentrations occurring above and below this interval cycladophora davisiana the dominant radiolarian species in the majority of holocene okhotsk sea sediments is present at lower percentages in late glacial samples from our two sites thus this species holocene latest pleistocene abundance pattern in sea of okhotsk sediments is the reverse of that recorded in high latitude open ocean sites the combined marine pollen and radiolarian records indicate changes in the sea of okhotsk s physical oceanographic conditions and surrounding vegetation during the late glacial which were associated with this region s response to global climate change

the cave of the monk ban fa suai chiang dao wildlife sanctuary northern thailand biostratigraphic and paleoecological analyses of southeast asian pleistocene faunal sites are based on the assumption that paleontological assemblages are homogeneous this means that the sites formed during a time range shorter than biological evolution range and above all without faunal replacement induced by environmental successions detailed study of the cave of the monk paleontological site in thailand has lead to the conclusion that the complex pattern of this southeast asian paleontological site cannot support such an assumption the cave of the monk provides an ailuropoda stegodon assemblage typical of southeast asia pleistocene fauna the pluridisciplinary study presented here includes i site morphology description ii sedimentological analysis of fossiliferous deposits iii taphonomy study of the bone assemblage and iv electron spin resonance esr dating of tooth samples this integrated approach demonstrates the existence of a pleistocene porcupine den inhabited during mis 3 and 2 the features of this site are commonly reported for other paleontological sites of the area indicating that this kind of site formation is a very general one in southeast asia esr dating and porcupine ethological reports are used to question the site time averaging a time range of a few tens of thousands of years is suggested the paleoecological value of the site can then be discussed on one hand the assemblage is thought to be a valuable paleoenvironmental record considering that the bone accumulation agent is reputed to represent the fauna present in the environment without bias on the other hand the time averaging of the site indicates that site formation range likely covered the environmental fluctuations of the last climatic cycle this last hypothesis is confirmed by the alternating association of species indicated by the stratigraphic distribution of the faunal remains the research demonstrates the need for integrated and pluridisciplinary taphonomic study of southeast asian paleontological sites it also reveals the utility of a microstratigraphic analysis of a fossiliferous karst deposit in order to disentangle the succession of pleistocene mammals in response to environmental changes

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

regional and global benthic δ18o stacks for the last glacial cycle although detailed age models exist for some marine sediment records of the last glacial cycle 0 150 ka age models for many cores rely on the stratigraphic correlation of benthic 18o which measures ice volume and deep ocean temperature change the large amount of data available for the last glacial cycle offers the opportunity to improve upon previous benthic 18o compilations such as the lr04 global stack not only are the age constraints for the lr04 stack now outdated but a single global alignment target neglects regional differences of several thousand years in the timing of benthic 18o change during glacial terminations here we present regional stacks that characterize mean benthic 18o change for 8 ocean regions and a volume weighted global stack of data from 263 cores age models for these stacks are based on radiocarbon data from 0 to 40 ka correlation to a layer counted greenland ice core from 40 to 56 ka and correlation to radiometrically dated speleothems from 56 to 150 ka the regional 18o stacks offer better stratigraphic alignment targets than the lr04 global stack and furthermore suggest that the lr04 stack is biased 1 2 kyr too young throughout the pleistocene finally we compare global and regional benthic 18o responses with sea level estimates for the last glacial cycle

new evidence for episodic post glacial sea level rise central great barrier reef australia abstract we present an extensive database of 364 radiocarbon dates from coastal and marine sediments of the central great barrier reef gbr shelf of which 110 are previously unpublished the elevation data have been reduced to a common datum australian height datum ahd and the various sources of error have been assessed using modern lithological and biological relationships with sea level the elements of the radiocarbon database have been converted into sea level indicators the upper bound of the assembled dataset corresponds to a best estimate sea level curve and the full dataset provides a narrow envelope for sea level rise on the gbr shelf for the last 11 12 kyr not including hydro isostatic crustal flexing the envelope is consistent with episodic rise in post glacial sea levels the rising post glacial sea level probably included stillstands or minor falls at ca 45 m ahd at ca 10 5 kyr b p 5 m 7 8 kyr b p 2 m ca 6 kyr b p and 1 7 m 5 5 kyr b p there is evidence for a significant fall in sea level between stillstands at 11 m 8 5 kyr b p and 17 m 8 2 kyr b p stillstand durations apparently ranged between the vertical spread in the derived sea level data is very wide the use of shell material for dating seems unreliable and prone to large and unpredictable errors data from bulk mangrove muds appear reliable for determination of ancient sea level but may at times result in sea level being placed up to 4 m below the true level in situ biogenic carbonates such as preserved oyster beds and coral micro atolls are the most reliable indicators of sea level position while deposits of mangrove mud give a useful first order approximation of ancient sea levels caution should be used in drawing sea level curves from few data points we conclude that the post 11 12 kyr b p relative rise in sea level was episodic on the central gbr continental margin more data are required to define clearly sea level change up to ca 20 m at 9 kyr b p

reflection of scandinavian ice sheet fluctuations in norwegian sea sediments during the past 150 000 years the record of glacier fluctuations in western scandinavia as reconstructed from continental data has been correlated with records of ice rafted detritus ird from well dated sediment cores from the norwegian sea covering the past 150 000 yr b p the input of ird into the ocean is used as a proxy for ice sheet advances onto the shelf and thus for the calibration of a glaciation curve the marine results generally support land based reconstructions of glacier fluctuations and improve the time control on glacial advances the saalian ice sheet decayed very rapidly approximately 125 000 yr b p in the early weichselian a minor but significant ird maximum indicates the presence of icebergs in isotope substage 5b especially between 95 000 and 83 000 yr b p reduced amounts of calcareous nannofossils indicate that surface waters were influenced by meltwater discharges during isotope substages 5d and 5b an extensive build up of inland ice began again during isotope stage 4 but maximum glaciation was reached only in early stage 3 58 000 53 000 yr b p marine sediments have minimum carbonate content indicating strong dilution by lithogenic ice rafted material generally the ird accumulation rate was considerably higher in stages 4 2 than in stage 5 a marked peak in ird accumulation rates from 47 000 to 43 000 yr b p correlates well with a second middle weichselian ice sheet advance dated by the laschamp olby paleomagnetic event minimum ice extent during the alesund interstade 38 500 32 500 yr b p and several glacial oscillations during the late weichselian are also seen in the ird record of several late weichselian glacial oscillations on the shelf at least four correspond to the north atlantic heinrich events ice sheet behavior was either coupled or linked by external forcing during these events whereas internal ice sheet mechanisms may account for the noncoherent fluctuations

trace elements stable isotopes and clay mineralogy of the elles ii k t boundary section in tunisia indications for sea level fluctuations and primary productivity abstract trace elements and stable isotopes in bulk rocks and foraminifera bulk rock and clay mineral compositions are used as palaeoproxies to evaluate sea level fluctuations climatic changes and variations in primary productivity across the k t transition at elles ii in tunisia from 1 m 33 kyr below to 1 m 70 kyr above the k t boundary results on clay minerals major and trace elements stable isotopes in bulk rock samples e g ca cu zn rb sr zr ba 13c and 18o and in foraminifera sr ca 13c 18o indicate that the latest maastrichtian last 33 kyr in tunisia was marked by a relatively warm but humid climate and a rising sea level the transgressive surface is marked by deposition of a foraminiferal packstone just below the k t boundary followed by maximum flooding across the k t boundary red layer and black clay layer humid warm conditions accompanied the maximum flooding along with increased total organic carbon values and rapidly decreasing primary productivity at the k t boundary an impact event ir anomaly ni rich spinels spherules exacerbated already stressed environmental conditions leading to the mass extinction of tropical planktic foraminifera increasingly more humid conditions prevailed within the lowermost danian zone p0 50 kyr culminating in a sea level lowstand near the top of p0 a slow recovery of the ecosystem in zone p1a coincided with a rising sea level and gradually less humid climatic conditions

late glacial to recent deep sea benthic foraminifera from the northeastern atlantic cadiz gulf and western mediterranean alboran sea paleooceanographic results abstract deep sea benthic foraminifera of the region of water exchange between the mediterranean and the atlantic ocean at the gibraltar strait show significant water mass relationships for the past 18 000 years cores used in this benthic foraminifera analysis were selected according to the context of the distribution of various deep bottom water masses on each side of the gibraltar strait 1 1 on the atlantic side of the strait two cores ks 8228 ks 8229 are located in the present day nadw and one kc 8221 in the upper part of the present mediterranean outflow water 2 2 on the mediterranean side of gibraltar two cores kc 8241 su 8107 are located in the deep water mass and one ks 8230 in the intermediate water mass in the two deep basins 1500 2800 m depth in the gulf of cadiz 1200 1300 m depth in the alboran sea the paleooceanographic changes appear to be in an opposite way for the past 18 000 years the alboran basin shows a paleooceanographic evolution from a well oxygenated nutrient rich environment at about 18 000 yr b p to a nutrient poor oxygen depleted environment from 13 000 to the present time moreover for the time span synchronous with the well known development of sapropels in the eastern mediterranean basins between 10 000 and 7000 yr b p the faunal assemblage shows most unusual characteristics implying drastic environmental conditions conversely in the gulf of cadiz the environment pass as from a biotope occupied by an oxygen depleted nutrient poor water mass at about 18 000 years b p to a biotope occupied by nadw since the younger dryas this agrees with previous data obtained in the northeastern atlantic ocean caralp 1987 in the epibathyal zones 550 800 m depth on both sides of the gibraltar strait paleohydrographic changes do not seem so important according to the present and very late holocene assemblages which are similar on both sides of the strait with a strong east west flow two other stratigraphic episodes have shown the same conditions of water exchanges the end of the isotopic stage 2 and the younger dryas conversely during the last glacial maximum the bolling allerod and the lower holocene westward water fluxes were probably lower at no time the hypothesis of a reversal or a stop in the east west exchanges between mediterranean and atlantic ocean may be justified

stable isotopes in benthic foraminifera from ontong java plateau box cores erdc 112 and 123 abstract detailed oxygen and carbon isotope stratigraphies for two species of benthic foraminifera planulina wuellerstorfi oridorsalis umbonatus are compared between two box cores spanning the period of deglaciation and holocene within core stratigraphies are quite well correlated between core signals less so vertical mixing and possibly horizontal redeposition processes disturb the signals nevertheless there is a strong suggestion of fluctuations in the ambient bottom water conditions fo the entire time span considered

reconstructing last glacial maximum bottom water salinities from deep sea sediment pore fluid profiles deep sea sediment pore fluids contain a record of past glaciations in their cl and 18 o the signal of the last glacial maximum lgm ice volume increase remains in the pore fluids as a local peak in each of these species using a one dimensional model to account for the diffusive and advective transport within the sediment column since the lgm the past bottom water salinity and 18 o seawater values can be estimated the model is most sensitive to the shape of the forcing function used to represent bottom water variations through time the effective diffusion coefficient and the scatter in the data assuming steady state compaction the model is relatively insensitive to the initial condition the bulk sedimentation rate and the assumed porosity profile though these last two are measured independently overall uncertainties in the relative cl increase at the lgm are between 0 1 and 0 5 where the mean ocean change is about 3 5

changes in the oceanic 13c 12c ratio during the last 140 000 years high latitude surface water records detailed records of the carbon and oxygen isotopic ratios of neogloboquadrina pachyderma are compared between nine high latitude sediment cores from the northern and southern hemispheres covering the last 140 000 yrs the strong analogies between the 13c records permit to define a 13c stratigraphic scale with three clear cut transitions simultaneous with the oxygen isotopic transitions 65 125 kyrs 54 65 kyrs and 21 13 kyrs the 13c records of n pachyderma in the high latitude cores which follow the changes in 13c of the surface water tco2 near areas of deep water formation present trends similar to the benthic foraminifera 13c records in cores v19 30 and m12 392 although amplitudes of the isotopic shifts are different this implies that a large part of the observed variations represents global changes in the carbon distribution between biosphere and ocean the 13c12c ratios of n pachyderma in the north atlantic cores display larger regional variations at 18 kyrs b p than at present to explain these differences we have plotted the 18 kyrs b p 13c values of n pachyderma from 17 cores distributed n of 40 n comparison with published surface water temperature distribution at 18 kyrs b p indicates that a strong divergent cyclonic cell centered approximatively 55 n and 15 w was active during most of the last ice age maximum this hydrology analogous to the present weddell sea explains the published evidences of bottom water formation if located on the northern flank of the gyre and the strong polar front on the southern flank probable location of intermediate water formation

the terraces of corinth gerrce a detailed record of eustatic sea level variations during the last 500 000 years abstract between corinth and xylokastro 20 marine terraces reflect the interaction of the northern peloponnese uplift and the global eustatic sea level fluctuations during the last 500 000 years correlation of the terraces with oxygen isotope records in deep sea cores allowed accurate dating of these fossilized transgressive shorelines curves of altitude versus age have been plotted they show a regular decrease of the uplift rate and a frequent return of the sea level very close to the present day one not only during the interglacial periods 5 7 9 11 13 but also during glacial periods 3 1 3 3 6 8 the alternative would be to suppose very complicated and highly improbable vertical movements of the substratum to explain the regularity of the curves the rhythm of these high sea levels is around 20 30 ka since at least 330 000 years ago

a radiometric calibration of the specmap timescale the astronomical theory of climate change asserts that earth s climate is affected by changes in its orbit which vary the seasonal and latitudinal distribution of solar radiation this theory is the basis of the orbitally tuned specmap timescale a key constraint for this important chronology was the mid point of the penultimate deglaciation initially dated to 127 000 years ago recent work suggests this event may be considerably older casting doubt on the astronomical theory the specmap timescale and the accuracy of orbitally tuned chronologies difficulties with u th coral dating of sea level events have impeded progress on this problem because most corals are not closed systems here we use a new approach to u th dating that corrects for open system behavior and produces a sea level curve of sufficient resolution to confidently correlate with specmap over the last 240 000 years permitting a reassessment of both this critical chronology and a central tenet of climate change theory high precision ages for 24 oxygen isotope events provide a 240 000 year chronology for marine 18o records that is independent of orbital tuning assumptions although there appear to be significant differences between the radiometric and orbitally tuned timescales near the lastglacial maximum and at the marine isotope stage 7 6 boundary a comparison of radiometric and specmap ages for identical isotope events suggest that the specmap timescale is quite accurate and that its errors were in general overestimated despite suborbital complexity orbital cyclicity is clearly evident in our record high amplitude sea level oscillations at periods greater than 20 000 years are very close in phase to summer insolation in the northern hemisphere although sea level changes cannot be uniquely tied to a specific season or latitude of insolation forcing the simplest explanation is that long period high amplitude sea level change is linked to northern hemisphere insolation forcing these results validate the principles of orbital tuning and suggest such timescales are generally robust

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

climate of the last glaciation in new zealand based on aerosolic quartz influx in an andesitic terrain abstract on western north island new zealand a record of climatic change during the last glaciation is preserved in a terrestrial coverbed sequence of dominantly andesitic provenance here a succession of five loess like andisol units postdates the global high sea level stand of oxygen isotope substage 5e

quaternary sequences along the north shore of lake ontario oshawa port hope we describe six major stratigraphic units from the hitherto neglected quaternary sequences along the north shore of lake ontario between oshawa and port hope these units from the base upwards co

high resolution stratigraphic correlation of benthic oxygen isotopic records spanning the last 300 000 years abstract in order to compare the response of different oceanographic regions to global climate change very detailed stratigraphic techniques are required the global signal of ice volume changes recorded in the oxygen isotopic composition of foraminifera can provide the tool for developing the necessary high resolution stratigraphy in order to evaluate the resolution of a stratigraphy based on detailed isotopic records two techniques are used to correlate a set of benthic oxygen isotope records from seven piston cores taken in the north and south atlantic the indian and the equatorial and north pacific oceans the first technique was modified from the graphic correlation procedure of shaw 1964 this procedure requires the identification of isotopic events that are correlated from core to core detailed correlations for intervals of the cores between events are provided by a series of straight line segments connecting all common events the second technique developed by martinson et al 1982 uses inverse procedures to define a continuous non linear mapping function that correlates the isotopic records the mapping function maximizes the correlation coefficient between data sets being compared the techniques are independent in that they rely on different criteria for correlating the data series stratigraphic correlations obtained by these procedures are in excellent agreement the mean difference between the correlations is on the order of the sampling intervals of each core and when corrected for sedimentation rates suggests that benthic isotope records from the suite of seven cores can be correlated to a resolution of 2000 to 4000 yrs

rapid sea level fall and deep ocean temperature change since the last interglacial period we have dated huon peninsula papua new guinea and barbados corals that formed at times since the last interglacial period applying both 230 th and 231 pa dating techniques as a test of age accuracy we show that marine isotope stage mis 5e ended prior to 113 1 8 0 7 kyr when sea level was 319 m during mis 5b sea level was 357 m at 92 6 8 0 5 kyr having dropped about 40 m in approximately 10 kyr during the mis 5c 5b transition sea level then rose more than 40 m during the mis 5b 5a transition also in about 10 kyr mis 5a lasted until at least 76 2 8 0 4 kyr at a level of 324 m at that time combined with earlier data that places mis 4 sea level at 381 m at 70 8 kyr our late mis 5a data indicate that sea level fell almost 60 m in less than 6 kyr 10 6 m kyr during the mis 5 4 transition the magnitude of the drop is half that of the glacial interglacial amplitude and approximatelyequivalent to the volume of the present dayantarctic ice sheet during this interval the minimum average rate of net continental ice accumulation was 18 cm yr likely facilitated by efficient moisture transport from lower latitudes at three specific times 60 6 8 0 3 50 8 8 0 3 and 36 8 0 2 kyr during mis 3 sea level was between 385 and 374 m sea level then dropped to 3107 m at 23 7 8 0 1 kyr early in mis 2 before dropping further to last glacial maximum lgm values and then rising to present values during the last deglaciation times of rapid sea level drop correspond to times of high winter insolation at low northern latitudes and high winter latitudinal gradients in northern hemisphere insolation supporting the idea that these factors mayhave resulted in high water vapor pressure in moisture sources and efficient moisture transport to high latitude glaciers therebycontributing to glacial buildup we combined our sea level results with deep sea n 18 o records as a means of estimating the temperature and ice volume components in the marine n 18 o record this analysis confirms large deep ocean temperature shifts following mis 5e and during termination i deep ocean temperatures changed bymuch smaller amounts between mis 5c and 2 maximum temperature shift in the deep pacific is about 2 whereas the shift at a site in the atlantic is 4 under glacial conditions temperatures at both sites are near the freezing point the shift in the atlantic is likelycaused bya combination of changing proportions of northern and southern source waters as well as changing temperature at the sites where these deep waters form

oxygen and carbon isotopes of individual shells of planktonic foraminifera from ontong java plateau equatorial pacific abstract analyses of single shells of orbulina universa and two other species show ranges of 2 in 18 o and 13 c at various levels in a box core from the western equatorial pacific seasonal and inter annual variations can account for only about half of this range variations in depths of calcification and in metabolic effects must account for the rest the large range must introduce considerable noise in multi shell analysis unless the number of shells in the sample is of the order of 50 or more we did not find a change in the range downcore nor did we find any evidence for the deglacial meltwater spike

sampling statistic limitations on benthic foraminifera chemical and isotopic data abstract analyses of benthic foraminiferal isotopic and chemical properties are typically done on a small number of individuals often 5 10 because benthic sediment mixing produces a mix of individuals whose properties were determined at times encompassing several thousand years a sampling of several individuals does not adequately represent the average mixture a quantitative statistical analysis shows that this effect places a fundamental limit on measurement precision in cores especially where rapid environmental changes occur over short vertical distances the fundamental parameters defining this limit are the rate of change of the property per unit distance and the effective mixing depth in cores found in the vema channel rio grande rise region where sedimentation rates are about 1 cm ka 1 and mixing depths are about 3 cm a single sampling of six individuals can produce a result that has an expected one sigma standard deviation of 6 25 of the observed range precision can be improved by using more individuals or running more replicate analyses but the result only improves as the square root of the number of individuals or replicates this effect is illustrated by cd ca and isotopic data from low 0 7 cm ka 1 and moderate 1 5 cm ka 1 sedimentation rate cores although precision is compromised the most in low sedimentation rate cores this effect contributes to imprecision in high sedimentation rate cores as well

a high resolution opal and radiolarian record from the subpolar north atlantic during the mid pleistocene transition 1069 779ka palaeoceanographic implications abstract a high resolution record of radiolarian assemblages from site u1314 was studied to reconstruct hydrographic and climatic changes in the north atlantic ocean during the mid pleistocene transition period 1069 779 ka besides the faunal record absolute accumulation of radiolarians and total biogenic opal are used to determine changes in surface water productivity results show that the north atlantic arctic front shifted back and forth repeatedly at a glacial interglacial timescale bringing the site under the influence of both cold arctic glacial and much warmer atlantic interglacial waters during glacial intervals and ice rafted debris ird events the deep dwelling taxon cycladophora davisiana was the greatest contributor of the radiolarian assemblage suggesting cold surface conditions melt water discharge and changes in deep and intermediate circulation interglacial intervals were characterized by abundant shallow dwelling taxa like pseudodyctiophimus gracilipes and lithomelissa setosa increased opal accumulation and higher radiolarian diversities indicating a northward flow of warm atlantic surface waters to the site u1314 area a marked change in the structure of the radiolarian assemblage occurred after mis 22 860 ka with large taxa differences between warm and cold periods probably in response to changing ocean conditions due to the higher amplitude of glacial interglacial changes as the dominant periodicity of high latitude climate oscillations shifted from 41 kyr to 100 kyr thus we conclude that the radiolarian assemblage from the north atlantic have changed drastically along with variations in ocean circulation in response to orbital and millennial scale climatic variations that occurred in the early and mid pleistocene