comparison of imbrie kipp transfer function and modern analog temperature estimates using sediment trap and core top foraminiferal faunas we evaluate the reliability of statistical estimates of sea surface temperature sst derived from planktonic foraminiferal faunas using the modem analog method and the imbrie kipp method global core top faunas provide a calibration data set while modem sediment trap faunas are used for validation linear regression of core top predicted sst against atlas sst generated slopes close to one for both methods however the imbrie kipp transfer function temperature estimates had an intercept 1 3oc warmer than modem analog estimates and 1 7oc warmer than recorded atlas sst the rms error for the core top data set using the modem analog method 1 5oc was smaller than that of the imbrie kipp method 1 9oc sst errors for the sediment trap faunas were not statistically different from those of the core top data set regardless of method developing imbrie kipp transfer functions for limited regions reduced the rms variability but introduced residual structure not present in the global imbrie kipp transfer function dissolution simulations with the sediment trap sample which generated the warmest sst residual for both methods suggests that the loss of delicate warm water foraminifera from midlatitude sediments may be the cause of this thermal error we conclude that 1 the fauna structure of sediment trap and core top assemblages are similar 2 both methods estimate sst reliably for modem foraminifera flux assemblages but the modem analog method exhibits less bias and 3 both methods are relatively robust to samples with low communality but sensitive to selective faunal dissolution

seasonal variation in the flux of planktonic foraminifera time series sediment trap results from the panama basin abstract a mooring array with three automated sediment traps capable of collecting time series samples was deployed in the panama basin for one year beginning in december 1979 a series of six consecutive two month long samples was collected at each of three depths 890 2590 and 3560 m in order to examine seasonal variation in the flux of planktonic foraminifera and evaluate the contribution of foraminifera to the total carbonate flux the flux of the larger planktonic foraminifera 250 500 m and 500 1000 m is greatest during february march when upwelling is most intense in the panama basin in contrast the maximum flux of the smaller foraminifera 125 250 m is associated with a phytoplankton bloom during the summer months june through september this size dependent flux pattern appears to be a species specific effect the flux of the larger foraminifera is dominated by non spinose forms i e neogloboquadrina dutertrei and globorotalia theyeri while the flux of the smaller foraminifera consists predominantly of spinose species i e globigerinoides ruber g sacculifer and g conglobatus although the magnitude of the flux varied throughout the year the average weight of individual foraminiferal tests in different size fractions showed no seasonal variability with the exception of the june july period when there was a major coccolith bloom planktonic foraminifera greater than 125 m account for between 28 and 34 of the total carbonate flux at this location during the coccolith bloom planktonic foraminifera accounted for less than 2 of the total carbonate flux planktonic foraminifera in the 250 500 m size range are the most significant contributors to the overall particulate flux accounting for roughly 70 80 of the total foraminiferal fluxes measured at the three trap depths

mg ca ratios of single planktonic foraminifer shells and the potential to reconstruct the thermal seasonality of the water column mg ca ratios of surface and subsurface dwelling foraminifera provide valuable information about the past temperature of the water column planktonic foraminifera calcify over a period of weeks to months therefore the range of mg ca temperatures obtained from single specimens potentially records seasonal temperature changes we present solution derived mg ca ratios for single specimens of the planktonic foraminifera species globigerinoides ruber pink globigerinoides ruber white and globorotalia inflata from a sediment trap off northwest africa 20 45 6 n 18 41 9 w cleaning of single specimens was achieved using a flow through system in order to prevent sample loss mg ca ratios of surface dwelling g ruber pink show strong seasonality linked to sea surface temperature mg ca ratios of g ruber white do not show such seasonality subsurface dwelling g inflata flux is largest during the main upwelling season but mg ca ratios reflect annual temperatures at intermediate water depths the sediment trap time series suggests that changes in the range of mg ca ratios exhibited by single specimens of g ruber pink and g inflata from the sedimentary record should provide information on the past temperature range under which these species calcified statistical analysis suggests detectable changes in the mg ca range are 0 80 mmol mol g ruber pink and 0 34 mmol mol g inflata for g ruber pink such changes would indicate changes in the seasonal sea surface temperature range 4 c or a shift in the main calcification and reproductive period for g inflata such changes would indicate 1 7 c changes in the thermocline temperature or a change in the depth habitat

environmental interpretation and a sequence stratigraphic framework for the terminal proterozoic ediacara member within the rawnsley quartzite south australia abstract fossils of the ediacara biota are confined to preservational windows in the ediacara member of the rawnsley quartzite pound subgroup from the flinders ranges south australia the base of the ediacara member is a type 1 sequence boundary incised into the partly lithified chace quartzite member of the rawnsley quartzite the ediacara member and the upper half of the rawnsley quartzite comprise the rawnsley depositional sequence bounded above by the early cambrian uratanna depositional sequence the rawnsley sequence developed over an erosional surface cut into the chace quartzite member with some 250 m of relief southeasterly directed palaeovalleys are filled with a sequence of massive sandstone and laminated siltstone passing up into well bedded sandstone at lowstand local channels were filled by massive sand the highstand systems tract consists of several parasequence sets of laminated siltstone and channelized amalgamated massive sandstone overlain by interbedded siltstone and sandstone grading up into well bedded clean sandstone impressions of soft bodied ediacaran organisms are preserved above the valley fill facies on sandstone partings within upward shoaling delta front environments between storm and fairweather wavebase the ediacara member is in places conformably overlain by up to 500 m of sandstone of the same lithofacies as those underlying the member distinctive microbial mat bound sand laminae described as petee structures are characteristic of the rawnsley quartzite above and below the ediacara member during deposition of the ediacara member colonization of the deeper substrates by microbial mat communities enabled preservation of the ediacara biota the erosional surface at the base of the ediacara member is one of at least four incision events recorded in the terminal proterozoic and early cambrian succession of the adelaide geosyncline the similarity of incision filling lithofacies of the rawnsley and uratanna sequences has in condensed sections led to confusion between the depositional sequences characteristic trace and body fossil assemblages provide the only clear distinction between depositional cycles spanning the proterozoic cambrian boundary

acraman impact ejecta and host shales evidence for low temperature mobilization of iridium and other platinoids geochemical investigations of a widely dispersed late proterozoic impact ejecta horizon and its host shales bunyeroo formation australia have provided strong evidence for low temperature mobilization of the platinum group elements pge including ir pge anomalies are associated with both the ejecta horizon ir up to 2 0 ppb pt up to 270 ppb and the green shales that envelop it several pge anomalies 0 073 0 45 ppb ir 3 11 314 ppb pt also occur in thin green shale beds at other stratigraphic levels within a predominantly red shale sequence average red shale background of 0 019 ppb ir and 0 89 ppb pt all green shale horizons analyzed regardless of their stratigraphic position have relatively high levels of ir and other pge the nonextraterrestrial postdepositional origin of the pge at other stratigraphic levels away from the impact ejecta horizon is indicated by their occurrence in thin permeable green beds in a predominantly red shale sequence their association with enrichments in cu v zn ni and their nonchondritic pge interelement ratios the impact ejecta horizon has a more chondritic pge geochemistry consistent with a meteoritic origin a redox precipitation model similar to that invoked for redbed cu u v deposits is proposed to explain the pge anomalies in the green shales

exceptionally preserved microbially induced sedimentary structures from the ediacaran post glacial successions in the kimberley region northwestern australia abstract a set of exceptionally preserved microbially induced sedimentary structures miss is described from the post glacial yurabi formation of late ediacaran age in the kimberley region northwestern australia these miss comprise oriented grains bamboo leaf like cracks polygonal cracks worm like cracks sinuous cracks gas domes pyrite concentrated laminae and micrite laminae most of the yurabi miss are morphologically comparable with their ancient and modern counterparts micrometre or nannometre scale bacteria or biofilm like inorganic objects are detected from most miss and are interpreted as bacterial bodies or remains that have been replaced with inorganic minerals upon fossilization oriented grains indirectly support microbial control on their accumulation both pyrite conformable laminae and micrite laminae suggest degradation and decay of original microbial mats upon diagenesis sinuous cracks were likely generated in a soft sediment deformation process whereas other sand cracks bamboo leaf like cracks worm like cracks polygonal cracks could have formed from sediment surface layer microbial organics shrinkage upon desiccation gas domes may have formed as the result of anoxic redox reactions and being filled with gases and sediments transported from below two proxies bedding plane coverage percentage and accumulative thickness of single miss bearing beds are developed to semi quantitatively evaluate miss abundance on bedding plane and vertical outcrop respectively the yurabi miss have substratum preference to fine sandstone facies and intertidal settings the yurabi formation yields the most abundant and diverse post glacial miss assemblages during the late ediacaran worldwide both kimberley and global fossil records indicate that miss may have proliferated in shallow marine ecosystems soon after the retreat of ediacaran gaskiers glaciation during late neoproterozoic

moored sediment trap measurements of carbon export in the subantarctic and polar frontal zones of the southern ocean south of australia sediment trap moorings were deployed from september 21 1997 through february 21 1998 at three locations south of australia along 140 e at 47 s in the central subantarctic zone saz with traps at 1060 2050 and 3850 m depth at 51 s in the subantarctic front with one trap at 3080 m and at 54 s in the polar frontal zone pfz with traps at 830 and 1580 m particle fluxes were high at all the sites 18 32 g m 2 yr 1 total mass and 0 5 1 4 g organic carbon m 2 yr 1 at 1000 m assuming minimal flux outside the sampled summer period these values are similar to other southern ocean results and to the median estimated for the global ocean by lampitt and antia 1997 and emphasize that the southern ocean exports considerable carbon to the deep sea despite its high nutrient low chlorophyll characteristics the saz site was dominated by carbonate 50 of total mass and the pfz site by biogenic silica 50 of total mass both sites exhibited high export in spring and late summer with an intervening low flux period in december for the 153 day collection period particulate organic carbon export was somewhat higher in all the traps in the saz range 0 57 0 84 gc m 2 than in the pfz range 0 31 0 53 with an intermediate value observed at the saf 0 60 the fraction of surface organic carbon export estimated from seasonal nutrient depletion lourey and trull 2001 reaching 1000 m was indistinguishable in the saz and pfz despite different algal communities

southern ocean seasonal temperature and subtropical front movement on the south tasman rise in the late quaternary 1 the subtropical front stf marking the northern boundary of the southern ocean has a steep gradient in sea surface temperature sst of approximately 4c over 0 5 of latitude presently in the region south of tasmania the stf lies nominally at 47s in the summer and 45s in the winter we present here sst reconstructions in a latitudinal transect of cores across the south tasman rise southeast of australia during the late quaternary sst reconstructions are based on two paleotemperature proxies alkenones and faunal assemblages which are used to assess past changes in sst in spring and summer the north south alignment in core locations allows reconstruction of movement of the stf over the last 100 ka surface water temperatures during the last glaciation in this region were 4c colder than today additional temperature changes greater in magnitude than 4c seen in individual cores can be attributed to changes in the water mass overlying the core site caused by the movement of the front across that location during the penultimate interglacial sst was 2c warmer and the stf was largely positioned south of 47s movement of the stf to the north occurred during cool climate periods such as the last marine isotope stages 3 and 4 in the last glaciation the front was at its farthest north position becoming pinned against the tasmanian landmass it moved south by 4 latitude to 47s in summer during the deglaciation but remained north of 45s in spring throughout the early deglaciation after 11 ka b p inferred invigoration of the east australia current appears to have pushed the stf seasonally south of the east tasman plateau until after 6 ka b p when it achieved its present configuration

glacial incursion on a neoproterozoic carbonate platform in the kimberley region australia the 80 m thick egan formation preserves sediment deposited during the younger of two episodes of glaciation recorded in the neoproterozoic succession of the kimberley region northwestern australia like many terminal proterozoic glaciations recorded in australia and elsewhere the glacial strata of the egan formation are associated with carbonate rocks of likely warm water affinity but they are sedimentologically distinct from the marker cap carbonate horizons that overlie glacial strata in other neoproterozoic successions the carbonate strata comprise a wide range of facies indicative of shallow water patch reef shoal and lagoonal deposition detailed facies analysis of the egan formation indicates interruption of the carbonate system by glaciation and subsequent resumption of warm water conditions this sedimentological analysis allows a reassessment of the regional stratigraphic correlations proposed for the egan formation which is here considered to record a glacial event younger than the widespread marinoan glaciation of central and south australia and therefore a speculated third global glaciation in terminal proterozoic time

efficacy of δ18o data from pliocene planktonic foraminifer calcite for spatial sea surface temperature reconstruction comparison with a fully coupled ocean atmosphere gcm and fossil assemblage data for the mid pliocene sea surface temperature sst estimates using the 18o composition of fossil planktonic foraminifer calcite within the time slice 3 12 to 3 05 ma pliocene kaena subchron c2an1r are assessed for nine atlantic ocean sites these are compared with sst estimates from fossil assemblages for the time slab 3 29 2 97 ma and with estimates from a fully coupled ocean atmosphere general circulation model gcm for the same time interval most sst estimates derived from the 18o data indicate a cooler ocean surface than at present through the latitudinal range 69 25 n to 46 88 s at some sites the temperature difference is greater than 5 c cooler than at present this contrasts with sst estimates from fossil assemblages that give warmer than present temperatures at mid to high latitudes and similar temperatures in the tropics and with the gcm which predicts ssts warmer than at present across all latitudes for this time interval difficulties interpreting the ecology of fossil foraminifer assemblages and inaccurate estimates of mid pliocene seawater 18o composition 18osw at some sites may partly produce the temperature discrepancy between isotope based and fossil based sst estimates but do not adequately explain the cool signal of the former we interpret the cool sst estimates from the 18o data to be the product of a calcite formed at a level deep within or below the ocean mixed layer during the life cycle of the foraminifera b secondary calcite with higher 18o formed in the planktonic foraminifer tests in sea bottom pore waters although these effects differ between sites secular and temporal oceanographic trends are preserved in the primary calcite formed in the mixed layer near the ocean surface witnessed by the latitudinal variation in estimated ssts reconstructing accurate mid pliocene ssts with much of the existing published oxygen isotope data probably requires a detailed re assessment of taphonomy particularly at tropical sites this study also indicates that methods for estimating atlantic pliocene 18osw need to be refined

a 450 kyr planktonic foraminiferal assemblage record of iodp site u1352 and its implications for the migration of the subtropical front in the south west pacific abstract the subtropical front stf is one of the major ocean fronts in the south west pacific the stf migration has a distinct but varying impact on the temperature change throughout the region to improve our understanding on the history of the stf migration and the relationship between stf migration and global climate change we have generated a 450 kyr record of sea surface temperature sst change at iodp site u1352 located in the canterbury basin off new zealand planktonic foraminiferal assemblages from the site were used to derive sst estimates comparisons of the planktonic foraminiferal assemblage and sst record of iodp site u1352 with those of odp site 1119 dsdp site 594 and core md06 2986 allow us to reconstruct the spatial change of the stf over the last 450 kyr by locating the positions of its southland front sf section which runs nearly parallel to the south island s shoreline the percentage of neogloboquadrina pachyderma in the sum of nq pachyderma and nq incompta was below 40 at sites iodp u1352 odp 1119 and dsdp 594 during marine isotope stage mis 11c mis 7a c and mis 5e moreover the ssts of the three sites during these periods were similar and close to that of the present day this indicates that the three sites were covered by a subtropical water subantarctic water stw saw mixture during these interglacials iodp site u1352 recorded a similar scenario during mis 7e in comparison with previous studies the higher resolution record of iodp site u1352 showed the influence of an stw saw mixture was limited to mis 11c mis 7e mis 7a c and mis 5e at this site the ssts of sites iodp u1352 odp 1119 and dsdp 594 were similar during mis 11a b and mis 9a d at the same time the temperature differences among the three sites and core md06 2986 west of new zealand during mis 11a b and mis 9a d were larger than during interglacials mis 11c mis 7a c and mis 5e these indicate that the subantarctic water saw influenced sites iodp u1352 odp 1119 and dsdp 594 during mis 11a b and mis 9a d the 3 4 c warmer ssts at sites iodp u1352 and odp 1119 than at dsdp site 594 suggest that the sf is situated between dsdp site 594 and sites iodp u1352 odp 1119 during mis 7d and glacial periods of mis 10 mis 8 and mis 6 hence unlike previous studies in the region mis 7d is identified as a glacial period

ediacaran palaeomagnetism and apparent polar wander path for australia no large true polar wander summary we report new palaeomagnetic data for red beds from the ediacaran brachina and wonoka formations in the adelaide geosyncline south australia and discuss their place with previously determined poles in the ediacaran apparent polar wander path for australia both formations behave similarly on thermal demagnetization displaying high temperature components that decay to the origin at 680 c consistent with haematite being the only magnetic mineral present restoring the strata to the palaeohorizontal yielded positive fold tests for both units at 99 per cent confidence indicating that acquisition of magnetization occurred before the early palaeozoic delamerian orogeny for the brachina formation n 91 specimens the mean direction after unfolding is declination d 178 2 inclination i 22 6 95 4 4 indicating a palaeolatitude 11 8 2 5 and a pole position at latitude p 46 0 s longitude p 315 4 e with confidence semi axes dp 2 4 and dm 4 6 the mean direction for the wonoka formation after unfolding n 70 is d 255 9 i 23 7 95 6 4 indicating 12 3 3 8 3 4 and a pole position at latitude p 5 2 s longitude p 30 5 e dp 3 6 and dm 6 8 the mean directions for these units and other ediacaran units in the adelaide geosyncline are significantly different from each other which excludes blanket remagnetization of the units before delamerian folding and therefore gives strong preference to their magnetization dating from close to the time of deposition the late cryogenian ediacaran cambrian apparent polar wander path for south australia spans 150 myr from 635 to 490 ma and places australia in low palaeolatitudes throughout the interval studied the poles differ significantly from each other suggesting australia underwent continual drift during that time whereas the directional difference between the late cryogenian elatina formation and early ediacaran nuccaleena formation is mainly in inclination for most other contiguous stratigraphic units the differences are mainly in declination with minor inclination differences indicating australia was rotating about a nearby euler pole in low palaeolatitudes the large and perhaps rapid polar shifts at 615 590 and 575 565 ma in the laurentian apparent polar wander path are not evident in the ediacaran apparent polar wander path for australia because true polar wander should be recorded globally in the absence of evidence for any major stratigraphic break in the south australian succession we conclude that large true polar wander did not occur during the ediacaran

neoproterozoic to lower palaeozoic successions of the tandilia system in argentina implication for the palaeotectonic framework of southwest gondwana the cryogenian to uppermost ediacaran successions of the tandilia system sierras bayas group and cerro negro formation in central eastern argentina is exceptional because of its unmetamorphosed and nearly undeformed character its sediment provenance trend and the absence of any identified glacial deposit and the deposition of warm water carbonates we decipher a dramatic change in the basin evolution from small scale depositional areas during the neoproterozoic to a larger basin related to an active continental margin throughout the uppermost ediacaran the base of the succession is represented by immature detritus of alkaline composition villa monica formation but towards the top of this formation the material is sorted and reworked nonetheless still reflecting in its detritus the local rocks the clastic deposition is interrupted by diagenetic overprinted dolomites the unconformable overlying quartz arenitic ediacaran cerro largo formation reworked the cryogenian villa monica formation and contains mainly felsic granitic and metamorphic basement material of slightly wider variety while the dominant alkaline geochemical signature in rocks of the villa monica formation disappears based on diagenetic petrographic and sedimentological data we can interpret the unconformity representing a longer time of erosion the cerro largo formation shows a transition to mudstones and the heterolithic facies of the olavarria formation the top of the sierras bayas group is represented by limestones loma negra formation which are discordantly overlain by the uppermost ediacaran cerro negro formation the latter displays detrital material derived from a continental arc mafic and felsic sources several arc related geochemical proxies th sc 20 are recorded in the sediment detritus as are syn depositional pyroclastites the absence of volcanic material in the underlying rocks allows proposing that the cerro negro formation is related to an active continental margin fringing gondwana terra australis orogen as a retro arc or retro arc foreland basin

a large scale meandering submarine canyon outcrop example from the late proterozoic adelaide geosyncline south australia the late proterozoic adelaide geosyncline along with overlying cambrian strata comprises a thick sequence of sediments and sparse volcanics which accumulated in a major rift and passive margin setting during late syn rift or early post rift phases large volumes of terrigenous and carbonate sediments of the late proterozoic umberatana and wilpena groups and cambrian hawker group filled the rift submarine canyon development was related to at least four of these depositional cycles the most notable of which resulted in incision and subsequent filling of the major several kilometres in width and up to 1 5 km deep submarine canyons by the wonoka formation the wonoka formation canyons are not obviously fault controlled they are interpreted to have been eroded by turbidity currents during a relative low stand of sea level they were subsequently filled by a fining upwards suite of sediments which reflects subsequent relative rise of sea level and carbonate platform development ultimately the canyon complex was buried by north westerly progradation of overlying fluvial and slope sequences billy springs beds and possibly correlative upper pound subgroup it is considered likely that more distal elements of this prograding clastic wedge provided the necessary material for canyon erosion prior to canyon filling and ultimate burial by what may have been elements of the same depositional cycle it is considered possible that the series of isolated outcrops of canyon cross sections within the wonoka formation are sections of a single canyon thalweg developed within a considerably broader zone of slope degradation if this interpretation is correct then the gorge like patsy springs canyon lies in more proximal regions of the basin slope whereas 40 km to the north east the lower slope is cut by the fortress hill canyon complex palaeocurrent analyses of channel fill turbidites within the canyons imply that the fortress hill complex is in fact the outcropping western edge of a sinuous incised canyon thalweg the wonoka formation canyons containing basal sedimentary breccias but only minor conglomerates are considered typical of passive margin canyon development they are contrasted with the generally highly conglomeratic channel fills observed in outcropping tertiary and cretaceous examples of active margin canyons and upper fan valleys

planktonic foraminifera as indicators of oceanographic complexity on the southern caribbean sea continental shelf abstract the southern caribbean sea over the northern south american continental shelf is oceanographically complex it is subject to 1 widespread coastal upwelling 2 wakes and eddies in the nw flowing guiana and caribbean currents to the lee of islands and 3 the hypopycnal orinoco river plume upwelled water is dispersed nw along high productivity filaments offshore northern trinidad an intra plume front separates higher productivity orinoco derived water to the west from lower productivity amazon derived water this paper examines planktonic foraminiferal assemblages in surface sediment samples a below upwelling foci in the gulf of venezuela gov north of lake maracaibo and b at an upwelling focus in the north coast marine area ncma offshore northern trinidad near but west of the intra plume front the samples were collected for previous studies and only certain size fractions which differed between the study areas were available for current study samples from the gov 250 m fraction taken using an alpine corer or a petersen dredge were assigned a priori to groups underlying upwelled and non upwelled water discriminant analysis after cluster analysis confirmed these assignments total recovery was dominated by neogloboquadrina dutertrei with lesser globigerinoides ruberpink and the upwelling indicator globigerina bulloides all four non upwelled samples co dominated by n dutertrei and gs ruberpink reflect seasonal freshwater outflow from lake maracaibo five upwelled area samples were dominated by g bulloides with subdominant n dutertrei or globigerinoides ruber morphotype b the remaining two upwelled samples dominant n dutertrei subdominant gs ruber morphotype a apparently reflect the transition between upwelling and non upwelling areas the mean proportions of assemblages as trilobatus sacculifer morphotype a did not differ markedly between the upwelled and non upwelled gov clusters this morphotype was absent from the gulf proper but present to the north ncma total recovery 150 m fraction samples taken using a van veen grab was dominated by gs ruber morphotype b cluster analysis here indicated three clusters cluster 1 proximal to the intra plume front cluster 2 distal to the intra plume front and cluster 3 scattered throughout the ncma upwelling was pervasive canonical variate analysis cva verifying that g bulloides did not differentiate the clusters instead these clusters were differentiated by gs ruber morphotype b only the proportional abundance of which was highest in cluster i and lowest in cluster 2 this pattern indicates that the influence of the orinoco plume on assemblage composition is stronger than that of upwelling cluster 1 reflecting higher productivity near the front

seasonal variability in the δ18o and δ13c of planktonic foraminifera from an upwelling environment sediment trap results from the san pedro basin southern california bight stable isotopic analyses 18o and 13crpar on four species of planktonic foraminifera collected from high resolution time series sediment trap sampling indicate that rapid and significant seasonal variability occurred in response to rapid changes in both the hydrographic environment and the isotopic composition of ambient seawater specimens were collected at a depth of 500 m for 28 consecutive 1 week periods in the san pedro basin within the southern california bight a region seasonally influenced by upwelling hydrographic monitoring of the study area revealed a 6 week period late april to mid june during which pulses of upwelling occurred causing significant increases in the oxygen isotopic composition of surrounding waters while decreasing the carbon isotopic composition analyses of globigerina bulloides orbulina universa neogloboquadrina dutertrei and neogloboquadrina pachyderma right coiling indicate that during the upwelling period these species live respectively at the surface in the surface mixed layer within the thermocline and below the thermocline globigerina bulloides ascends from well below the thermocline to the surface at the onset of upwelling and increases production to its maximum simultaneously as its morphology changes to less calcified open forms both n dutertrei and n pachyderma follow isothermal ranges migrating to shallower waters during upwelling and subsequently descending after upwelling ceases neogloboquadrina dutertrei appears to inhabit the region associated with both the thermocline base and chlorophyll maximum when it is most abundant following upwelling orbulina universa increases its depth habitat as solar irradiance increases but this species decreases in abundance during upwelling the 18o signal of o universa appears to be a useful indicator of seasonal temperature variations above the thermocline whereas the 18o of g bulloides documents near surface temperatures during upwelling the 13c signal of both n dutertrei and n pachyderma appears to record the 13c of equilibrium calcite for the regions of the thermocline and just below the thermocline respectively due to the relative preservation potentials of the four species analyzed only n dutertrei and n pachyderma are likely to be preserved in the sedimentary record in regions of oxygenated bottom waters thus an actual record of hydrographic conditions during upwelling as would be found in tests of g bulloides is not preserved instead conditions before n pachyderma and just after n dutertrei are more likely recorded

sea surface temperatures of the southwest pacific ocean during the last glacial maximum the southwest pacific ocean covers a broad range of surface water conditions ranging from warm salty water in the subtropical east australian current to fresher cold water in the circumpolar current using a new database of planktonic foraminifera assemblages ausmat f2 we demonstrate that the modern analog technique can be used to accurately reconstruct the magnitude of sea surfacetemperature sst in this region we apply this technique to data from 29 deep sea cores along a meridional transect of the southwest pacific ocean to estimate the magnitude of sst cooling during the last glacial maximum we find minimal cooling in the tropics 0 2 c moderate cooling in the subtropical midlatitudes 2 6 c and maximum cooling to the southeast of new zealand 6 10 c the magnitude of cooling at the sea surface from the tropics to the temperate latitudes is found to generally be less than cooling at the surface of adjacent land masses

late cretaceous upwelling system along the southern tethys margin israel interrelationship between productivity bottom water environments and organic matter preservation organic rich upper cretaceous sequences in israel were deposited in an extensive highly productive upwelling linked system which prevailed along the southern tethys margin and lasted for 19 m y santonian to late maastrichtian an understanding of the spatial and temporal characteristics of this system was gained through detailed paleontological and geochemical analyses of subsurface sequences in two basins in israel representing an outer shefela and an inner zin facies belt the nature of the upwelling system and its effect on the sedimentary record is related to two basic environmental parameters namely paleoproductivity intensity and oxygen levels at the bottom the assessment of these parameters and their interrelationship has been performed through the development of paleontological foraminiferal criteria which are independent of the organic matter content following the establishment of these criteria it is concluded that the productivity reached its maximum intensity during the late campanian which was also the time of most notable differentiation between the center of the upwelling system in the inner belt and the less intense conditions in the outer basin this distribution is expressed in varied lithology organic rich carbonates phosphorites and siliceous rocks at the core of upwelling and a uniform lithology organic rich carbonates at the margin of this system the uniform lithology of the maastrichtian in both basins composed of organic rich carbonates is ascribed to a gradual weakening of productivity the bottom conditions in the inner belt during the late campanian the time of maximum surface productivity were near anoxic changing to more aerated dysaerobic conditions during the early maastrichtian in the outer belt a more aerated bottom dysaerobic prevailed throughout the late campanian to late maastrichtian the elevated organic matter content in both basins reflects the overall environment of high productivity its actual variations however seem to be unrelated to changes in surface productivity and bottom oxygen levels

neoproterozoic stratigraphy of the centralian superbasin australia abstract the basement of central australia includes the arunta block and the 1200 1100 ma musgrave block succeeded by 1075 1000 ma bimodal volcanic rifts and dolerite dykes a regional hiatus at 1000 800 ma interpreted as reflecting a central post volcanic underplated upland was followed at 800 ma by a second swarm of dykes in the musgrave block gawler craton and stuart shelf associated with the crustal sagging that initiated the centralian superbasin the centralian superbasin is defined here to encompass the neoproterozoic fill of the amadeus georgina ngalia officer and savory basins the intra cratonic superbasin was disrupted internally 540 600 ma ago petermann ranges orogeny by a central uplift and associated thrusts and by mid carboniferous 320 ma tectonism alice springs orogeny to form the structural basins listed above the stratigraphy and sedimentology of the relatively well known areas can be used as a basis for predicting those of the poorly known regions new results from acritarch biostratigraphy and isotope chemostratigraphy in conjunction with conventional lithostratigraphy and sequence analysis allow better stratigraphic resolution than previously possible field observations in the recently discovered savory basin in western australia provide a basis for correlations with the adjacent basins

acritarchs from the doushantuo formation at liujing section in songlin area of guizhou province south china implications for early middle ediacaran biostratigraphy abstract a taxonomically diverse and morphologically disparate microfossil assemblage is recovered from the upper doushantuo formation in the liujing section of songlin area guizhou province including acanthomorphic and sphaeromorphic acritarchs multicellular algae and filamentous cyanobacteria acritarch mengeosphaera membranifera sp nov is newly erected and genus cymatiosphaeroides and several species c forabilatus c kullingii bacatisphaera baokangensis are emended in the systematics the acanthomorphic species are dominated by cymatiosphaeroides forabilatus and mengeosphaera membranifera sp nov the liujing assemblage shares many species with other ediacaran coeval assemblages from south china australia siberia the east european platform india mongolia and svalbard and indicates a significant taxonomic similarity to the global age diagnostic assemblages new occurrence of those known taxa in the liujing succession documents the biodiversity of the ediacaran acritarchs in south china the liujing assemblage extends the palaeogeographic distribution of the ediacaran acritarchs and may be assigned to the tanarium conoideum cavaspina basiconica assemblage zone that was recognized in the yangtze gorges area of south china alternatively it could be partially correlated with the barren interval between t conoideum c basiconica assemblage zone and the overlying tanarium pycnacanthum ceratosphaeridium glaberosum assemblage zone

comparison of seasonal flux variations of planktonic foraminifera in sediment traps on both sides of the ryukyu islands japan variations in the fluxes of planktonic foraminifera were analyzed based on sediment trap data collected over a period of 10 months from october 1994 to august 1995 at stations jast01 and jast02 located on both sides of the ryukyu islands japan station jast01 latitude 27 23 n longitude 126 44 e was deployed at a depth of 1000 m in the okinawa trough east china sea along the flow axis of the kuroshio current west of the islands whereas station jast02 latitude 25 4 n longitude 127 34 e was deployed at a depth of 3000 m in the ryukyu trench along the western margin of the northwest pacific east of the islands the total planktonic foraminiferal fluxes tffs in the eastern station were high in winter when the surface water column was vertically well mixed in contrast the tff peaks did not show significant seasonality in the western station but values fluctuated with the northwest southeast oscillation of the kuroshio axis among the 36 planktonic foraminiferal species identified in the trap samples globigerina bulloides globigerinita glutinata neogloboquadrina dutertrei pulleniatina obliquiloculata globigerinoides ruber globigerinoides sacculifer and globigerina falconensis exhibited a greater shell flux on both sides of the ryukyu island arc the fluxes of g ruber and g sacculifer increased synchronously with the seasonal warming of surface waters whereas that of g falconensis increased during winter when the water column was vertically well mixed as a result of the nw monsoon in contrast to these species which exhibited similar seasonal flux variation patterns at both stations the species g bulloides g glutinata n dutertrei and p obliquiloculata displayed different flux variations on both sides of the islands these fluxes seem to be regulated by phytoplankton productivity which is controlled by the vertical structure of the water column on the eastern ryukyu trench side and by the oscillation of the kuroshio axis on the western okinawa trough side lateral transport of suspended planktonic foraminiferal shells to the okinawa trough might exist but is not prominent enough to wipe out the original features of the planktonic foraminiferal flux the species g falconensis is an indicator of winter mixing on both sides of the ryukyu islands and may possibly be used as a proxy to trace the intensity of the paleo winter monsoon

seasonal changes in the isotopic composition of planktonic foraminifera collected in panama basin sediment traps abstract isotopic analyses have been made on five species of planktonic foraminifera collected in two deployments of parflux mark ii time series sediment traps in the panama basin the automated sampling system on the traps provided 4 one month samples from 29 july to 16 november 1979 and 6 two month samples from december 1979 to november 1980 the 18o values of globigerinoides ruber and globigerinoides sacculifer in this region are primarily affected by a low salinity surface layer that forms during the early winter these species each show a 1 total range in 18o the 18o values of the colder water species globorotalia menardii neogloboquadrina dutertrei and globorotalia theyeri show smaller seasonal changes in 18o the 13c values of g ruber and g sacculifer exhibit small seasonal changes 0 35 and 0 4 respectively despite large seasonal changes in surface water productivity the colder water species exhibit only slightly larger changes in 13c up to 0 55 throughout the year all colder water species exhibit minimum or near minimum 13c values during february and march which is the period of maximum upwelling and primary productivity seasonal variations in the flux of foraminifera in the water column at this location will have only a small effect on the isotopic composition of the sediment assemblage extreme values of 18o and 13c do not occur during the periods which are associated with the high flux of foraminiferal tests

signature of the brazil malvinas confluence argentine basin in the isotopic composition of planktonic foraminifera from surface sediments we explored the potential to use the stable isotopic compositions of planktonic foraminifera as a proxy for the position of the brazil malvinas confluence bmc in the argentine basin for this purpose we measured the oxygen and carbon isotopic compositions of globigerinoides ruber pink and white varieties measured separately globigerinoides trilobus globigerina bulloides globorotalia inflata and globorotalia truncatulinoides left and right coiling forms measured separately from a latitudinal transect of 56 surface sediment samples from the continental slope off brazil uruguay and argentina between 20 and 48 s lowest oxygen isotopes values were found in g ruber pink followed by g ruber white and g trilobus reflecting the highly stratified near surface water conditions north of the bmc globigerina bulloides was present mainly south of the bmc and records subsurface conditions supporting earlier plankton tow studies globorotalia inflata and g truncatulinoides left and right were both available over the whole transect and calcify in the depth level with the steepest temperature change across the bmc accordingly the 18 o of these species depict a sharp gradient of 2 at the confluence with remarkably stable values north and south of the bmc our data show that the oxygen isotopic composition of g inflata and g truncatulinoides left and right are the most reliable indicators for the present position of the bmc and can therefore be used to define the past migration of the front if appropriate cores are available

controls on the carbon isotopic composition of southern ocean phytoplankton carbon isotopic compositions of suspended organic matter and biomarker compounds were determined for 59 samples filtered from southern ocean surface waters in january 1994 along two north south transects woce sr3 from tasmania to antarctica and across the princess elizabeth trough pet east of prydz bay antarctica along the sr3 line bulk organic matter show generally decreasing 13c contents southward which are well correlated with increasing dissolved molecular carbon dioxide concentrations co2 aq this relationship does not hold along the pet transect using concentrations and isotopic compositions of molecular compounds we evaluate the relative roles of several factors affecting the 13c of southern ocean suspended particulate organic matter along the woce sr3 transect the concentration of co2 aq plays an important role it is well described by a supply versus demand model for the extent of cellular co2 utilization and its associated linear dependence of isotopic fractionation ep on the reciprocal of co2 aq an equally important factor appears to be changes in algal assemblages along the sr3 transect with their contribution to isotopic fractionation also well described by the supply and demand model when formulated to include the cell surface volume control of supply changes in microalgal growth rates appear to have a minor effect on ep along the pet transect algal assemblage changes and possibly changes in microalgal growth rates appear to strongly affect the carbon isotopic variations of suspended organic matter these results can be used to improve the formulation of modern carbon cycle models that include phytoplankton carbon isotopic fractionation

iridium anomaly from the acraman impact ejecta horizon impacts can produce sedimentary iridium peaks the observation of anomalously high iridium concentrations at the cretaceous tertiary k t boundary1 triggered the still unresolved debate concerning the origin of sedimentary ir anomalies several hypotheses have been presented including meteorite impacts1 2 and intense volcanism3 4 here we present data from the acraman impact ejecta horizon south australia5 which conclusively links high sedimentary iridium concentrations to a major meteoroid impact structure and its widely dispersed ejecta an ir anomaly up to 2 parts per 109 p p b ir as well as au pt pd ru and cr anomalies is present within the ejecta from the acraman impact event preserved in late precambrian 600 myr bp shales within the adelaide geosyncline the highest ir and cr concentrations within the ejecta are associated with the coarsergrained clasts of acid volcanics boulder to medium sand size suggesting that most of the ir is carried by these fragments the target rocks at the impact site are comparable acid volcanics that have very low ir au pt pd ru and cr concentrations indicating a meteoritic origin for the anomalous ir levels within the ejecta to our knowledge this is the first example in which an accepted widely dispersed impact ejecta blanket itself uniquely linked to a major terrestrial impact structure5 6 has been shown to be anomalously high in cosmogenic siderophile elements this finding strongly supports the hypothesis that ir anomalies in sediments can be produced by terrestrial meteorite impact events

quaternary history of calcium carbonate fluctuations in the western equatorial indian ocean somali basin abstract a study of the quaternary history of calcium carbonate fluctuations in the equatorial indian ocean based on the swedish deep sea expedition core 154 demonstrates that the calcite compensation depth ccd was shallower during interglacial periods than during glacials higher percentages of calcium carbonate lower percentages of dissolution resistant planktonic foraminifera and lower values of the berger dissolution index suggesting better calcium carbonate preservation are recorded during glacial periods and or at glacial interglacial transitions in contrast interglacial periods are marked by stronger calcium carbonate dissolution the data indicate that dissolution is the main controlling factor of calcium carbonate in the western equatorial indian ocean higher dissolution during interglacial periods and enriched 13 c are due to higher noncarbonate productivity and enhanced antarctic bottom water aabw ventilation in the equatorial indian ocean

the nature of the proterozoic cambrian transition in the northern amadeus basin central australia abstract the nature and completeness of the rock record is vital in determining whether evolution across the proterozoic cambrian boundary was episodic or explosive this study documents the nature of the neoproterozoic cambrian transition within the arumbera sandstone of the northern amadeus basin central australia and demonstrates an erosional surface close to this major stratigraphic boundary we are not able to recognise major facies differences between the largely unfossiliferous lower units i and ii and the rich trace fossil bearing beds of units iii iv horizons above and below the purported neoproterozoic cambrian transition were traced laterally and searched for both trace and body fossils in an attempt to locate a local boundary between the neoproterozoic and cambrian a single nonconformity bound sedimentary cycle above the major erosional surface dividing arumbera ii and iii is recognised the lowest sedimentary cycle of arumbera iii is devoid of trace fossils but at correlative levels in the ooraminna sub basin this horizon bears elements of the ediacara fauna reported for the first time herein we therefore suggest that contrary to previous studies the neoproterozoic cambrian transition is not coincident with the widespread seismic reflector but in areas of more complete sedimentation actually lies above it this study also presents new stratigraphic ichnological and palaeontological information from the neoproterozoic cambrian transition in central australia identifies areas of potentially continuous sedimentation and provides a basis for correlation of the arumbera sandstone with other neoproterozoic cambrian successions within australia and beyond

warmer tropics during the mid pliocene evidence from alkenone paleothermometry and a fully coupled ocean atmosphere gcm 1 traditional reconstructions of sea surface temperatures ssts produced by the pliocene research interpretations and synoptic mapping prism group indicate that mid pliocene surface ocean temperatures were unchanged or slightly cooler than modern at the tropics and low latitudes and significantly warmer at higher latitudes particularly in the north atlantic this change in the latitudinal pattern of ssts has been attributed to enhanced meridional ocean heat transport generated by more vigorous surface ocean gyres and or thermohaline circulation thc this study derives new sst estimates using the alkenone paleothermometer in the pacific ocean these estimates combined with published alkenone sst data from two atlantic sites are located in tropical and subtropical regions where the distribution of prism sites is sparse a fully coupled ocean atmosphere general circulation model oagcm running for the mid pliocene was also used to predict sst significant differences are noted between absolute prism ssts interpolated to our core locations and alkenone derived ssts these differences may be related to errors in the prism and alkenone paleothermometry estimates or to regional differences between localities where data was collected however the available alkenone and model based sst estimates are consistent in the sign of temperature change they predict and provide the first indication of warmer ssts during the mid pliocene in the tropics and subtropics this contrasts with prism s estimates of unchanged or slightly cooler ssts for the same geographical regions the pattern of ssts produced by alkenone estimates and modeling is not characteristic of that produced by enhanced meridional ocean heat transport or thc instead the pattern is similar to that which might be expected as a result of higher concentrations of atmospheric co2 which would act to warm the oceans at the tropics and other latitudes furthermore model diagnostics indicate that reduced sea ice and terrestrial ice sheet extents and a strong ice albedo feedback played a major role in forcing mid pliocene warmth further work aimed at validating these conclusions should concentrate on expanding the mid pliocene sst data set particularly at low latitudes as well as undertaking model model comparisons to assess model dependency of the results

climatic evolution in the australian region over the last 94 ka spanning human occupancy and unveiling the last glacial maximum abstract the quaternary is well known for being a period of the geological record that saw significant and alternating climatic fluctuations here we concentrate on the last 94 millennia that saw australia and its surrounding seas undergo significant environmental changes importantly also it is during that this period of time includes the arrival and settlement of humans in australia following on from marine isotopic stage 4 mis4 that saw over the period of 71 59 ka bp a significant eustatic sea level drop 100 m low sea surface temperatures as well as glacial conditions on land australia experienced wet conditions again but eventually progressively entered into a glacial phase by then humans had arrived on this large continent and later the megafauna progressively became extinct this paper describes in detail the climate over this period based principally on the high resolution record of two marine sediment cores located offshore of the southern australian margin and that are then compared with known events on land as well as other deep sea cores particular emphasis is placed on the period that spans the last glacial maximum lgm the extent of which thus far had been poorly defined in the australian region emphasis is placed on the period from 34 to 14 ka to demonstrate that 1 the lgm defined here as the period 24 to 18 ka was not always extremely dry and cold and 2 that people were able to live in inland australia as water existed in places despite generally cold conditions we also show using a series of ten maps at 2 ka intervals over the 34 14 ka period the waxing and waning of oceanic fronts such as the subtropical and subantarctic fronts link sea surface temperatures sst with periods of glacial expansion in the australian alps and tasmania as well as the south island of new zealand and the extent of the leeuwin current down to south of australia aeolian dust was transported at sea over the main core site from 26 to 18 ka period pointing to arid conditions in australia but this period was punctuated by two significant reductions in dust transport to both core sites coinciding with a retreat of the subantarctic front away from the australian southern coastline and slight sst shifts for a few centuries at 24 and 22 21 ka bp at the peak of the cold phase from 23 to 18 4 ka summer sst were of the order of 9 c below that experienced during the middle of the holocene at about 6 ka bp a similar temperature drop was also experienced offshore the northwestern corner of western australia periglacial activity dates for the australian mainland and tasmania pool around 22 ka on either side of the 24 ka event the chain of lakes in the willandra lakes retained water and human activity was registered in the area elsewhere in australia water was present to sustain human populations during the cold and dry times it is postulated here that northern australia was at times quite wet especially during mis4 the cessation of the lgm is set on 18 4 ka from offshore southern australia as confirmed for the deep sea cores by several proxies and more likely at 18 ka inland finally we document that it took two millennia for glacial conditions to end in the australian region as registered in our deep sea core records well after the lowest global sea level 20 6 and 20 ka respectively started to rise there is also evidence of another very cold period determined on the australian mainland tasmania and the south island of new zealand centred around 27 ka after which time warmer conditions occurred before the start of the lgm this is matched with our deep sea records with very cold conditions and changes in oceanographic conditions

seasonal associations of phytoplankton and planktic foraminifera in an upwelling region and their contribution to the seafloor abstract seasonal occurrences of both phytoplankton and zooplankton are closely associated with upwelling and stabilization in waters overlying the san pedro basin this region is situated within the southern california bight and is affected by variations in the general southward flowing california current and variable intrusion of oceanic waters increased northerly wind stress in spring and early summer results in upwelling of deeper nutrient rich waters into the photic zone a seven month time series sediment trap experiment revealed clear patterns in seasonal succession of both phytoplankton and planktic foraminifera several distinct high and low flux periods occurred over the study period some of which can be related to rapid changes in the hydrographic environment caused by upwelling and subsequent surface water stratification factor analysis of relative abundances of combined phytoplankton and foraminiferal taxa defines seven assemblages reflecting seven stages of production which range in duration from two to five weeks factor scores describe phytoplankton and foraminiferal taxa indicative of specific production stages periods of high flux of the more abundant diatoms and planktic foraminifera also illustrate preferred production stages and compare well with percentage based results a comparison of the sediment trap assemblage with local sediment from an oxygenated portion of the basin suggests that long term phytoplankton accumulation in this region is dominated by taxa associated with winter bloom and post upwelling bloom production implying that brief but massive episodic events overwhelm and dominate the annually averaged diatom species assemblage found in the sediments foraminifera however are modified by dissolution to the extent that the high production periods of late spring and during upwelling are poorly represented rather species indicative of early spring and post upwelling conditions dominate the planktic foraminiferal sedimentary assemblage

pleistocene variability of the subtropical convergence at east tasman plateau evidence from planktonic foraminiferal mg ca odp site 1172a combined measurements of mg ca and stable oxygen isotopes in tests of the planktonic foraminifer g bulloides from ocean drilling program odp site 1172a east tasman plateau allowed us to reconstruct sea surface temperature sstmg ca sea surface salinity sss and hence variations in the subtropical convergence stc in the southwestern tasman sea over the last four major glacial interglacial changes during interglacials the commonly enhanced sstmg ca and sss correspond to a lowered marine productivity and a lowered terrigenous flux implying that the stc separating cool high nutrient subantarctic surface water from warm saline oligotrophic subtropical surface water and hence the band of zonal westerlies responsible for the eolian dust flux were located south of east tasman plateau the warm east australian current was well established during warm periods and propagated far south during glacial times sstmg ca and sss were lower while both marine productivity and eolian flux increased such conditions prevailed during glacial marine isotope stages mis 12 mis 10 and to a lesser degree mis 6 and implied the extended northward influence of subantarctic surfacewater and a shift of the stc to 44 s the overall climatic signal at site 1172a appears to be largely attenuated when compared to published climate records from comparable latitudes to the west and to the east sstmg ca amplitudes were more pronounced in the subantarctic indian ocean and at chatham rise they exhibit a consistent pattern suggesting that latitudinal shifts of the stc occurred synchronously in the subantarctic indian ocean and at chatham rise but were largely damped at east tasman plateau due to the influence of the east australian current

acanthomorphic acritarchs of the doushantuo formation from an upper slope section in northwestern hunan province south china with implications for early middle ediacaran biostratigraphy abstract doushantuo pertatataka acritarchs dpas are abundant and well preserved in the ediacaran doushantuo formation in south china not only do they provide insights into the marine ecosystem immediately after a neoproterozoic global glaciation they also afford us an ideal tool for ediacaran stratigraphic subdivision and correlation however previous reports of dpas in south china are mostly from the yangtze gorges area in intra shelf basin and from weng an in shelf margin environments while data from localities in slope and basinal facies are lacking here we present lithostratigraphy carbon and strontium isotope chemostratigraphy and acritarch biostratigraphy of the doushantuo formation from an upper slope section at lujiayuanzi in northwestern hunan province south china five dpa genera and eight species are preserved in the doushantuo formation chert nodules with the uppermost two dpa horizons occurring above a 13 c negative excursion that is correlated with the en3 shuram excursion based on integrated litho and chemostratigraphic correlation our new findings reveal a broader temporal and spatial distribution of dpas in south china and further support their biostratigraphic potential in the early middle ediacaran subdivision and correlation

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

the fate of diatom valves in the subantarctic and polar frontal zones of the southern ocean sediment trap versus surface sediment assemblages abstract an array of deep ocean sediment traps was initiated in 1997 within the australian sector of the southern ocean and serviced annually for over a decade the subantarctic site is ongoing as part of the southern ocean time series here we expand on previous findings obtained from the shallow traps 1000 m depth in the polar frontal zone pfz and subantarctic zone saz by examining the chemical composition and diatom assemblages collected by sediment traps deployed at bathypelagic depths in the pfz 1500 m depth years 1997 1998 1999 2000 and 2003 2004 and saz 2000 and 3800 m year 1999 2000 additionally the diatom assemblages of the surface sediments below the traps were analyzed to document how the seasonal signal is recorded in the sedimentary record analysis of the changes of the bsi poc ratios with depth at both sites confirms previous work suggesting that the decoupling between si and c cycles in the southern ocean is not different from other biogeochemical provinces of the world s ocean comparison of the seasonal flux pattern registered by the traps indicates that the diatom assemblages in the sediments of the antarctic zone and pfz mainly represent the summer period in contrast the assemblages found in the sediments of the saz are a reflection of the spring and summer months a period characterized by a larger variability in chemical and physical parameters the strong correlation between the poc fluxes and the relative abundance of a group of diatom species mainly pseudo nitzschia and small fragilariopsis in the pfz traps suggest that there is an intimate relationship between the development of these species and the poc pulses to the deepest layers of the water column in this region interestingly analysis of the diatom assemblages in the surface sediments reveals that the strong dissolution in the sediment water interface removed the signal of these carbon sinkers from the sedimentary record leaving the sediment assemblage enriched in heavily silicified species

mechanisms and variations of the paleoproductivity off northern chile 24 s 33 s during the last 40 000 years 1 a multiparameter investigation including organic carbon carbonate opal and planktic foraminifera was carried out on five sediment cores from the coastal upwelling area between 24 s and 33 s along the peru chile current to reconstruct the history of the paleoproductivity and its driving mechanisms during the last 40 000 years inferred from our data we conclude that the antarctic circumpolar current as the main nutrient source in this region mainly drives the productivity by its latitudinal shifts associated with climate change simplified its northerly position during the last glacial led to enhanced productivities and its southerly position during the holocene caused lower productivities at 33 s the paleoproductivity was additionally affected by the southern westerlies and records highest levels during the last glacial maximum lgm north of 33 s several factors e g position and strength of the south pacific anticyclone wind stress continental runoff and el nino southern oscillation events supplementary influenced upwelling and paleoproductivity where maximum values occurred prior to the lgm and during the deglaciation

the problems and potential of using animal fossils and trace fossils in terminal proterozoic biostratigraphy abstract despite the discovery of soft bodied megascopic fossils of late neoproterozoic age at numerous localities world wide there has been slow acceptance of their potential for intercontinental correlation the stratigraphic thickness of sediments separating individual occurrences of such fossils from the base of the cambrian is very varied basic questions have also been posed as to the classification of the organisms represented and hence their likely time significance recent geochronological studies support notions of a narrow time distribution well studied neoproterozoic sequences in eurasia eastern and western north america and southern australia show strikingly similar patterns of increase in the numbers and diversity of trace fossils and soft bodied megascopic remains up section though strata immediately preceding the cambrian are relatively barren other than for a sparse palynoflora and compressions of primitive plants trace fossils from australian sections relating to an early part of the ediacaran apparently overlap a time of abundance of large process bearing acritarchs and big leiosphaerids this overlap of early animal traces and distinctive acritarchs may prove to be of significant biostratigraphic importance rare discoveries of forms resembling rangea gurich in the flinders ranges of south australia precede the classical ediacara assemblage and may provide a possible correlation with occurrences of this genus in namibia the distinctive remains and trace fossils at this level constituting the rangeid hiemalora assemblage zone resemble a biota from the podolia region of the ukraine and show a similarity to finds in parts of the windermere supergroup of the northwest territories canada similarly the offshore frondose assemblage of newfoundland is comparable with the biota of charnwood forest england the type ediacara assemblage of the flinders ranges characterizing the dickinsonia costata assemblage zone is a climax biota with diverse taxa and large individual species as well as some 20 ichnogenera it closely correlates with a late redkinian or early kotlinian assemblage in the upper part of the section on the zimny gory coast of the white sea northern russia the trace fossils of these levels show that significant diversification began before the cambrian

glacial southern ocean freshening at the onset of the middle pleistocene climate transition changes in southern ocean hydrography may have played an important role in the middle pleistocene transition mpt particularly through their impact on ocean circulation and atmospheric co2 concentrations here we present foraminiferal mg ca and 18o results for the subsurface dwelling planktonic foraminifer neogloboquadrina pachyderma sinistral at the ocean drilling program odp site 1090 results are used to reconstruct upper ocean temperatures and derive seawater 18o in the subantarctic atlantic ocean during the mpt the new records indicate that starting at 1250 ka glacial temperatures and local ice volume corrected seawater 18o in the upper water column of the subantarctic atlantic ocean decreased pointing to cooler 2 c and fresher 0 4 conditions than in the preceding glacial stages these upper ocean hydrographic changes broadly coincide with the increase in the power of the 100 ky glacial interglacial cycle in both records and with a shift towards decreased deep ventilation in the glacial southern ocean our finding suggests that an increase in southern ocean stratification driven by the observed freshening of the upper water column may have reduced the exchange of carbon between the deep southern ocean and the atmosphere during glacial stages this process may have contributed in combination with other mechanisms to lower glacial atmospheric co2 concentrations during the mpt

planktic foraminiferal and sea surface temperature record during the last 1 myr across the subtropical front southwest pacific planktic foraminiferal faunas and modern analogue technique estimates of sea surface temperature sst for the last 1 million years myr are compared between core sites to the north odp 1125 178 faunas and south dsdp 594 374 faunas of the present location of the subtropical front stf east of new zealand faunas beneath cool subtropical water stw north of the stf are dominated by dextral neogloboquadrina pachyderma globorotalia inflata and globigerina bulloides whereas faunas to the south are strongly dominated by sinistral n pachyderma 80 95 in glacials with increased g bulloides 20 50 and dextral n pachyderma 15 50 in interglacials beneath subantarctic water or saw canonical correspondence analysis indicates that at both sites sst and related factors were the most important environmental influences on faunal composition greater climate related faunal fluctuations occur in the south significant faunal changes occur through time at both sites particularly towards the end of the mid pleistocene climate transition mis18 15 e g decline of globorotalia crassula in stw disappearance of globorotalia puncticulata in saw and during mis8 5 interglacial sst estimates in the north are similar to the present day throughout the last 1 myr to the south interglacial ssts are more variable with peaks 4 7 c cooler than present through much of the early and middle pleistocene but in mis11 mis5 5 and early mis1 peaks are estimated to have been 2 4 c warmer than present these high temperatures are attributed to southward spread of the stf across the submarine chatham rise along which the stf appears to have been dynamically positioned throughout most of the last 1 myr for much of the last 1 myr glacial sst estimates in the north were only 1 2 c cooler than the present interglacial except in mis16 mis8 mis6 and mis4 2 when estimates are 4 7 c cooler these cooler temperatures are attributed to jetting of saw through the mernoo saddle across the chatham rise and or waning of the stw current to the south glacial sst estimates were consistently 10 11 c cooler than present similar to temperatures and faunas currently found in the vicinity of the polar front one interpretation is that these cold temperatures reflect thermocline changes and increased circumpolar surface water spinning off the subantarctic front as an enhanced bounty gyre along the south side of the chatham rise for most of the last 1 myr the temperature gradient across the stf has been considerably greater than the present 4 c during glacial episodes the stf in this region did not migrate northwards but instead there was an intensification of the temperature gradient across it interglacials 4 11 c glacials 8 14 c

neoproterozoic carbon isotope stratigraphy of the amadeus basin central australia neoproterozoic shallow marine and carbonate rich strata of the northern amadeus basin central australia comprise a geochemical record of neoproterozoic seawater that facilitates correlation with other basins in australia and worldwide this study includes new carbon and oxygen isotope measurements of cryogenian and ediacaran carbonate in the northern amadeus basin that in combination with previous data from tonian strata of the bitter springs formation form a composite amadeus basin neoproterozoic c record key features of the cryogenian ediacaran portion of this record include 1 negative c excursions in cap carbonates overlying cryogenian glacigenic deposits of the areyonga and olympic formations i e the rasthof and maieberg excursions respectively 2 a mid cryogenian negative excursion in the ringwood member of the aralka formation seemingly correlative with the taishir excursion of sw mongolia 3 a subsequent mid cryogenian positive excursion the keele peak excursion in the limbla member of the aralka formation and 4 relatively low magnitude excursions in the ediacaran julie formation in comparison with other neoproterozoic stratigraphic successions key portions of the overall neoproterozoic c record that appear to be absent from the amadeus basin based on existing data include large magnitude negative excursions islay and trezona excursions that immediately preceded basaland terminal cryogenian i e sturtian and marinoan respectively glaciations these missing c excursions are associated with significant unconformities in the amadeus basin c and o from carbonate clasts in diamictite of the areyonga and olympic formations suggest that deposition of islay and trezona equivalent strata was limited or nonexistent in the amadeus basin as opposed to the possibility that these strata were deposited but subsequently removed by glacial erosion our new amadeus basin results refine cryogenian and early ediacaran correlations among the amadeus basin adelaide rift complex and namibia the lower part of the ringwood member which was deposited during early stages of the cryogenian nonglacial interlude includes two negative c excursions that are also evident in previous results from the tapley hill formation of the adelaide rift complex the upper part of the ringwood member contains abundant stromatolites and seems to correlate with cryogenian stromatolite reefs of the balcanoona formation in the adelaide rift complex the overlying limbla member in the amadeus basin correlates with the yankaninna etina amberoona and enorama formations of the adelaide rift complex as well as carbonate from other continents that record the keele peak excursion c from the early ediacaran olympic cap of the amadeus basin is 1 comparable to previous results from the maieberg and elandshoek formations in namibia and 2 consistent with diachronous deposition of marinoan cap dolostone in the amadeus basin additionally new c from the julie formation of the amadeus basin is similar to previous results from the late ediacaran kuibis subgroup in southern namibia these correlations underscore that ediacaran strata of namibia as well as the cryogenian nonglacial interlude strata of the adelaide rift complex are roughly an order of magnitude thicker than stratigraphic counterparts in the amadeus basin the wide disparity in sedimentation rates implied by this finding is likely attributable to fundamental differences in the neoproterozoic tectonic settings of the three locations

isotope stratigraphy of the ediacarian neoproterozoic iii of the adelaide rift complex australia and the overprint of water column stratification abstract this study establishes a high resolution 13c chemostratigraphic framework for the type ediacarian terminal proterozoic section in the adelaide rift complex a framework that contributes to the emerging global chronostratigraphic synthesis of a period that saw momentous changes in the earth s surface environment only 15 m of the 3 5 km thick type section consists of shallow water carbonates of the kind that have formed the basis of most previous studies of neoproterozoic chemostratigraphy however the organic 13corg record reveals a surprising richness of information and shows excellent utility in correlation between sections in the adelaide rift complex lateral variations in 13corg profiles correspond to expected diachronous patterns of basin fill with the addition of 87sr 86sr data correlation can also be made to the officer and amadeus basins consistent with known lithostratigraphic and sequence stratigraphic constraints sublittoral micritic carbonates of the upper nuccaleena formation cap dolostone and lower and middle wonoka formation show strong basinwide 13c depletion 13ccarb 3 to 10 despite compelling evidence for preservation of depositional 13ccarb such as good textural preservation evidence for sea floor lithification and in the wonoka formation pristine 87sr 86sr and low mn sr associated with the depleted carbonates are rare subaqueous evaporite relatively heavy 13corg and anomalously 13c depleted organic carbon of benthic microbial mat origin and a common cause salinity stratification of the water column is postulated the indicated palaeogeographic setting an evaporative mediterranean like basin tenuously connected to the world ocean is entirely consistent with previous suggestions of one or more messinian type desiccation events to explain very deep 1 km incised valleys or canyons in the adelaide rift complex and officer basin at horizons within the wonoka formation and correlates positive excursions in 13corg during basin stratification may in part be due to 12c depletion of surface waters by photosynthetic carbon fixation despite the proposed semi isolation of australian ediacarian basins from the world ocean major 13c excursions which can to some extent be differentiated by the monotonic rise in ediacarian marine 87sr 86sr appear to be correlatable to the upper windermere supergroup northwest canada

coastal zone color scanner pigment concentrations in the southern ocean and relationships to geophysical surface features the spatial and seasonal distributions of phytoplankton pigment concentration over the entire southern ocean have been studied for the first time using the coastal zone color scanner historical data set from october 1978 through june 1986 enhanced pigment concentrations are observed between 35 s and 55 s throughout the year with such enhanced regions being more confined to the south in the austral summer and extending further north in the winter north and south of the polar front phytoplankton blooms 1 mg m3 are not uniformly distributed around the circumpolar region instead blooms appear to be located in regions of ice retreat or high melt areas such as the scotia sea and the ross sea in relatively shallow areas e g the patagonian and the new zealand shelves in some regions of ekman upwelling like the tasman sea and near areas of high eddy kinetic energy such as the agulhas retroflection among all features examined by regression analysis bathymetry appears to be the one most consistently correlated with pigments correlation coefficient being about 0 3 for the entire region the cause of negative correlation with bathymetry is unknown but is consistent with the observed abundance of iron in shallow areas in the antarctic region it is also consistent with resuspension of phytoplankton cells by wind induced mixing especially in shallow waters on the other hand in the deep ocean especially at latitudes 30 in average pigment concentration over the entire region during different seasons indicates possible influence of time dependent parameters

disparities in glacial advection of southern ocean intermediate water to the south pacific gyre highlights surface mg ca temperatures and salinities show comparable glacial conditions subsurface mg ca temperatures suggest that lgm is 3 to 2 c colder than mis 6 relative to holocene subsurface salinities suggest fresher lgm and saltier mis 6 thermal gradients suggest stratified lgm and well mixed mis 6 water column contrasting glacial scenarios suggest variable formation and advection of soiws abstract the intermediate waters formed in the southern ocean are critical for ventilating the thermocline in the southern hemisphere gyres and transporting climatic signals from high to low latitudes on glacial interglacial time scales despite the importance of the southern ocean intermediate waters soiws information on past changes in soiws formation is fragmentary and its impact on the south pacific gyre spg s thermocline largely unknown here we present a 200 kyr record of paired mg ca ratios and stable oxygen isotope from surface and deep dwelling planktonic foraminifera from the spg on average the globigerina bulloides mg ca derived sea surface temperatures show similar conditions during the lgm and marine isotope stage mis 6 9 4 c versus 9 8 c in contrast the subsurface temperatures derived from the mg ca values of globorotalia inflata and globorotalia truncatulinoides suggest that lgm is 3 to 2 c colder than mis 6 furthermore at subsurface depths the reconstructed 18osw ivc record proxy for relative local salinity changes suggests opposite glacial conditions with slightly saltier than holocene waters during mis 6 and fresher than holocene waters during lgm contrasting glacial scenarios plausibly due to changes in the presence of soiws at the study site suggest variable formation and or advection of soiws to the spg during different glacial stages the variability in soiws is probably driven by the changes in the intensity of the southern westerly winds

coastal upwelling in the canary island region spatial variability reflected by the surface sediment diatom record abstract modern diatom and c org distribution patterns were investigated in 39 surface sediment samples of the canary region in order to quantitatively determine the influence of coastal upwelling and saharan dust on the flux of these sedimentary components high diatom abundance in surface sediments 2 10 6 valves g 1 dry sediment as well as the dominance of the assemblages by spores of chaetoceros which is a genus related to upwelling conditions reflect the stronger coastal upwelling conditions occurring at cape ghir off the nw african coast further offshore total diatom abundance decreases one order of magnitude 1 10 5 valves g 1 dry sediment and the assemblages are dominated by oceanic species of the genus nitzschia and fresh water diatoms mainly the genera aulacoseira which is known to be a component of saharan dust this association suggest that offshore diatom concentrations may be generated by dust input from desert regions even though the sediments are expected to preserve only a mixed and averaged oceanographic signal characteristic biogeographic patterns of a phytoplankton community occurring across a gradient of turbulence and nutrient availability are recorded in surface sediments off cape ghir this is seen in the subsequent maximum abundances of the genera thalassiosira chaetoceros and rhizosolenia

storm dominated mixed carbonate siliciclastic shelf sequence displaying cycles of hummocky cross stratification late proterozoic wonoka formation south australia abstract the regressive late proterozoic wonoka formation of the adelaide geosyncline in south australia contains a thick mixed carbonate siliciclastic interval of middle to inner shelf origin the shelf was storm dominated and displays abundant hummocky cross stratification hcs of varying scales and other wave formed sedimentary structures some parts of this sequence are notably cyclic two kinds of cycles are described here the first average cycle 8 m thick consists of the alternation of silty and argillaccous limestone with fine grained hummocky cross stratified calcareous sandstone climatic cyclicity e g milankovitch cycles involving alternate wet and dry periods or minor sealevel fluctuations along a low gradient shoreline are considered the most likely cause of the observed sediment cyclicity carbonate deposition predominated during dry periods or high sealevel followed by influxes of sand from deltaic sources during wet periods or times of low sealevel the prevalence of hcs in the sandstones is most likely due to much slower rates of lithification in comparison to the limestones which give evidence of rapid lithification on the seafloor the second type of cycle average cycle 5 10 m thick is characterised by the cyclic appearence of red hummocky cross stratified glauconitic and phosphatic limestones within a sequence dominated by grey green stylonodular limestone tempestites the most likely origin of the red limestone involves contributions of volcanic ash fall material the resulting sediment did not undergo the rapid seafloor lithification of the associated grey green limestones and thus was involved in considerable storm wave reworking before deposition the micritic shelf carbonates of the wonoka formation are considered to represent direct inorganic precipitation into the middle shelf environment rather than reworking of detrital material from shallow carbonate banks

seasonal variations in foraminiferal flux in the southern ocean campbell plateau new zealand abstract time incremental sediment trap moorings were deployed at two sites across campbell plateau new zealand one in the relatively quiet waters of the plateau interior pukaki rise and the other at the antarctic circumpolar current swept margin eastern campbell flank a continuous record of particle flux over 416 days identifies marked differences in faunal composition and seasonal occurrence in response to these two dynamically different southern ocean settings in the shallow and thermally isolated interior of the pukaki rise site the flux of foraminifera was closely linked to the austral spring pulse of primary production at which time 97 of the total foraminiferal production for the year occurred this seasonal flux of foraminifera at pukaki rise was dominated by the species globorotalia inflata and globigerina bulloides the collapse of phytoplankton production at the end of spring was most likely a result of a co limitation of iron and silicic acid over the deep and dynamic eastern flank of campbell plateau there were four seasonal pulses of foraminiferal flux the largest in spring when almost half of the foraminiferal production occurred most of the spring flux at this site consisted of globorotalia inflata and globigerinita glutinata summer at eastern campbell flank exhibited the lowest flux of foraminifera but the highest species diversity while autumn and winter fluxes were dominated by the deep dwelling globorotalia truncatulinoides although there was only a single pulse of foraminiferal flux at pukaki rise its mass g m 2 d 1 was still greater than that which occurred over the flank summed across all four seasons however the overall standing stock tests m 2 d 1 on the flank was more than twice that which occurred at the pukaki rise site an examination of core top material taken from gravity cores collected in the vicinity of the sediment trap locations revealed typical southern ocean foraminiferal assemblages that were markedly dissimilar in proportion to those observed in the sediment traps

an integrated view of inorganic and organic biogeochemical indicators of palaeoproductivity changes in a coastal upwelling area in order to evaluate the role of the continental margin areas in the changes of atmospheric co2 during past climatic cycles it is crucial to reconstruct reliably export palaeoproductivity changes in such areas this paper examines and discusses the specific relationships between various productivity dependent geochemical signals recorded in a single sediment core from the northwestern africa continental slope including both major and trace parameters of inorganic and organic origin this paper clearly shows that the export productivity flux as well as its composition e g the relative contribution of calcareous siliceous and mineral free producers have changed these changes have subsequently modified benthic conditions which can have had in turn a retroaction on major biogenic element contents this effect seems however to be only minor compared to that one directly induced by changes in biogenic fluxes these results indicate that direct palaeoproductivity transfer functions which are based on present day statistical calibrations of one single parameter and which are valid to some extent for sediments from abyssal open ocean cannot be properly applied in marginal areas which are much more complex and in particular highly affected by sea level changes in such areas quantitative palaeoproductivity reconstructions should be only considered at a regional scale including off shoreward on shoreward and latitudinal migration or extension of the productive areas as well as the palaeoproductivity intensity and composition

impact ejecta horizon within late precambrian shales adelaide geosyncline south australia a solitary layer of shattered crustal rock fragments has been traced over a distance of 260 kilometers within folded 600 million year old precambrian marine shales of the adelaide geosyncline south australia the fragments consist entirely of acid to intermediate volcanics approximately 1575 million years old displaying shattered mineral grains shock lamellae in quartz and small shatter cones fragments reach 30 centimeters in diameter and show evidence of vertical fall emplacement available evidence points to derivation of the rock fragments from a distant hypervelocity impact into the gawler range volcanics at lake acraman approximately 300 kilometers west of the adelaide geosyncline

the witputs diamictite in southern namibia and associated rocks constraints for a global glaciation the witputs section of the gariep belt s namibia comprises a sequence of clastic and chemical sediments which have been interpreted as representative of a late neoproterozoic global or near global ice age event and recent biostratigraphic work in the upper rocks of the witputs suggest a late ediacaran age to further characterise this sequence and provide additional age constraints a detailed sedimentological and detrital zircon study has been carried out the petrographic sedimentological and geochemical characteristics of the witputs diamictite determined in this study are homogenous and indicative of debris flow or palaeo valley infill sediments deposited in an oxic environment with no glaciogenic evidence this homogeneity is also reflected in the detrital zircon age spectra with most ages falling between 1 0 and 1 3 ga representing the local geology with the youngest grain at 1030 2 10 9 2 n 92 10 discordance despite the fact that mid and late neoproterozoic volcanic activity is known in the local region the overlying carbonate rocks often considered to be cap carbonates show high mn up to 60 mno with base metal precipitation zn v co and are recrystallised their 13cvpdb isotope ratios are homogeneous at around 3 major and trace element ratios reach values which indicate that c o isotopes may be disturbed and might not reflect primary global seawater composition thus questioning their use for global correlation and comparison with composite chemostratigraphic curves the contact to the overlying late ediacaran sanddrif member is not exposed and the rocks dip in a different direction than the underlying carbonate rocks the c 40 m thick section is characterised by rapid lithology changes including shales calcareous sandstones and wackes fine grained conglomerates and rare clean quartz rich sandstones all of which have strikingly similar detrital zircon populations and the youngest zircon is dated at 1082 8 10 ma 2 errors from 72 grains with 10 discordance acritarchs earlier found in the sanddrif member however indicate a post 570 ma depositional age if the diamictites are glacio marine deposits then an interesting conclusion is that the clastic sediments can display a very immature geochemical signature indicating a localised provenance with derivation purely from the local basement rocks which is also reflected in the detrital zircon populations however we would hesitate to assign a glacial origin to the deposits as no glacial indicators other than a diamictitic texture were observed clearly far more work on the detailed mapping and sedimentology of the neoproterozoic gariep belt deposits is required particularly as many are currently used for global correlation age constraints derived from extensive detrital zircon work can only constrain the deposits as being post 1 03 ma with the detritus being purely locally derived

proterozoic canyons of the flinders ranges south australia submarine canyons or drowned river valleys abstract a number of kilometer sized erosional incisions canyons occur within a specific stratigraphic interval in the late proterozoic succession of the adelaide geosyncline flinders ranges south australia this paper describes in detail four adjacent east west orientated incisions in the northern flinders ranges which are interpreted to be part of an ancient sinuously meandering canyon system at least 600 m of siltstones and fine sandstones of the bunyeroo and the brachina formations were removed during the erosional event that produced the canyon infilling sediments which exhibit a similar succession in each incision were deposited during emplacement of the wonoka formation although an identical sedimentary succession occurs within each incision palaeocurrents determined from flute casts at the bases of sandstone beds alternate by close to 180 from one erosional feature to the next basal infilling sediments commonly contain lenticular breccias interpreted as slumps derived from the brachina formation which forms the incision walls it is significant that clasts in these breccias preserve evidence of lithification predating the erosional event that produced the incisions channel filling debris flow units which occur mainly above the basal slumps along with associated sandstones were most likely emplaced episodically asymmetric ripple cross laminae in the sandstone beds above and within debris flow units commonly are wave modified isolated occurrences of hummocky cross stratification are observed in most units of the incision fill a thin

the surface expression of radiocarbon anomalies near baja california during deglaciation abstract periods of declining atmospheric radiocarbon activity 14 c during the heinrich 1 17 8 14 6 ka and younger dryas 12 8 11 5 ka stadials of the last deglaciation coincide with intervals of rising atmospheric co2 as well as evidence of 14c depleted carbon at intermediate ocean depths near baja california mexico and in the arabian sea the latter has been interpreted as the signature of aged carbon emerging through the intermediate ocean to the atmosphere from a previously isolated deep ocean reservoir here we report measurements from near baja california that enable us to reconstruct the 14 c of surface waters as recorded by three different species of planktonic foraminifera we find that surface ocean 14 c recorded by planktonic foraminifera was anomalously low relative to the coeval atmosphere during previously documented periods of low benthic 14 c consistent with upwelling and subsequent mixing and or partial atmospheric equilibration of the intermediate depth benthic signal we also propose an oceanographic explanation for observed 14 c differences between individual planktonic species during deglaciation at this location based on seasonal growth habitats and a seasonal change in the source of coastal upwelling waters from northern in the spring to southern in late summer as the shelf trapped poleward california undercurrent strengthens an analysis of the contemporary hydrography and planktic habitat preferences suggests that g bulloides and g sacculifer record primarily springtime conditions off baja california when the local influence of waters sourced from the surface of the north pacific is greatest this is supported by the strong resemblance of the 14 c of those species and a recent record of planktic 14 c from the northeast pacific during deglaciation lower 14 c recorded by the late summer species g ruber suggests that locally upwelling waters carried 14c depleted carbon that was proximately sourced from equatorial subsurface waters entrained by the california undercurrent together with the benthic record these observations are consistent with transport of an anomalous 14c depletion signal carried primarily by antarctic intermediate water from an ultimate source in the southern ocean

late quaternary upwelling off tropical nw africa new micropalaeontological evidence from odp hole 658c planktonic foraminifera and radiolaria have been analysed in a late quaternary 40 0 ka sediment sequence from ocean drilling program odp hole 658c located under a coastal upwelling system near cap blanc offshore northwest africa in order to document the palaeoceanographic history of the area temporal variations in species abundance and faunal assemblage analysis reveal a tripartite phased sequence of palaeoceanographic change through the late quaternary phase 1 spans 40 14 5 ka and is characterised by moderate upwelling but heinrich event 2 is distinguished as a brief episode of strengthened upwelling phase 2 begins with a change in a number of variables at ca 14 5 ka and extends to ca 5 5 ka this phase is characterised by a general strengthening of upwelling but may be subdivided into three minor phases including a the recognition of the younger dryas marked by a temporary reduction in upwelling strength followed by b an intensification of upwelling and c upwelling and high productivity between 8 and 5 5 ka this phase of upwelling corresponds with maximum holocene cooling possibly triggered by the collapse of the laurentide ice sheet phase 3 extends from 5 5 to 0 ka and is characterised by weak upwelling and significant calcite dissolution these phases are related to climatic events particularly the african humid period ahp which is coincident with phase 2 the ahp is characterised by increased precipitation linked to an intensification of the african monsoon that enhances north east trade wind driven coastal upwelling and is associated with the expansion of continental vegetation across north africa copyright 2006 john wiley sons ltd

fine scale recognition and use of mesoscale fronts by foraging cape gannets in the benguela upwelling region oceanic structures such as mesoscale fronts may become hotspots of biological activity through concentration and enrichment processes these fronts generally attract fish and may therefore be targeted by marine top predators in the southern benguela upwelling system such fronts might be used as environmental cues by foraging seabirds in this study we analyzed high frequency foraging tracks gps 1 s sampling of cape gannets morus capensis from two colonies located on the west and east coast of south africa in relation to mesoscale fronts detected on daily high resolution chlorophyll a maps modis 1 km we tested the association of i searching behavior and ii diving activity of foraging birds with mesoscale fronts we found that cape gannets shift from transiting to area restricted search mode ars at a distance from fronts ranging between 2 and 11 km median is 6 7 km this suggests that cape gannets may be able to sense fronts smell or vision or other predators and that such detection triggers an intensified investigation of their surroundings i e ars also we found that diving probability increases near fronts in 11 out of 20 tracks investigated 55 suggesting that cape gannets substantially use fronts for feeding in the remaining cases 45 birds may have used other cues for feeding including fishing vessels particularly for gannets breeding on the west coast we demonstrated in this study that oceanographic structures such as mesoscale fronts are important environmental cues used by a foraging seabird within the rich waters of an upwelling system there is now need for further investigations on how cape gannets actually detect these fronts

seasonal succession vertical distribution and dissolution of planktonic foraminifera along the subarctic front implications for paleoceanographic reconstruction in the northwestern pacific abstract the regional spatial and depth distribution of planktonic foraminifera were studied through sediment trap observations at two stations stations wct 5 about 41 n 150 e and wct 6 about 42 n 155 e along the subarctic front in the northwestern pacific ocean the sediment traps were moored at 1000 and 4500 m depths at station wct 5 and 1091 2051 and 4871 m depths at station wct 6 the samples were collected from 17 august 1998 to 10 august 1999 at station wct 5 and from 15 august 1999 to 6 august 2000 at wct 6 at station wct 5 two distinct annual periods of increased total foraminiferal and species production were evident the period of highest production was in autumn with a secondary period in early summer at station wct 6 high total foraminiferal shell fluxes occurred in april may and september october the april may spring bloom of planktonic foraminifera apparently began each year as the sea surface temperature sst increased after winter and the decrease of thickness of the mixed water layer during june july in every year following the cessation of bloom the most common foraminiferal species in the study region were globigerina quinqueloba neogloboquadrina pachyderma neogloboquadrina dutertrei neogloboquadrina incompta globigerinita glutinata globigerina bulloides globigerina falconensis globorotalia theyeri globorotalia scitula and globigerinella calida foraminiferal fluxes displayed a distinct seasonality at all trap depths at both stations at station wct 5 in 1998 1999 foraminiferal species were scarce in the surface water during spring and summer and the dominant foraminiferal species were most productive during winter and autumn at station wct 6 the dominant foraminiferal species were most productive during late winter to spring and all species showed a peak in middle spring may a comparison of seasonal patterns of dominant foraminiferal species between the northwestern and northeastern pacific demonstrated that foraminiferal productivity was a good proxy for sea surface temperature and mixing of water column significant dissolution of foraminiferal tests was evident in the deepwater column and was used to estimate the foraminiferal lysocline depth 4500 m in the northeastern pacific basin

palaeoclimatic changes in kveithola svalbard during the late pleistocene deglaciation and holocene evidences from microfossil and sedimentary records abstract climate changes are reflected in the arctic ecosystem history over different timescales we use a multi proxy based approach for palaeoenvironmental and palaeoclimatic reconstructions conducted on sediment cores compared with summer insolation and greenland ice core 18o data in order to establish a framework for climate changes from late pleistocene to late holocene our dataset includes the results compiled from a sediment core collected on the middle slope of the kveithola trough mouth fan south of svalbard during the coribar cruise 2013 the studied core presents remarkable lithological and magnetic susceptibility similarities with cores recovered in the same area during the svais 2007 and the ogs eglacom cruise 2008 allowing the construction of the age model the results indicate that during the last 14 5 cal ky bp advances and retreats of the svalbard barents sea ice sheet were strictly linked to the interplay of atlantic and arctic water inflows to the study area during the deglaciation from the last glacial maximum to the onset of the holocene the climate underwent a series of abrupt changes including the bolling allerod warm interstadial and the younger dryas cold event during the early holocene the investigated area was dominated by enhanced warm atlantic water inflow which was concomitant with summer insolation increase characterizing the holocene thermal maximum conversely the late holocene was governed by deteriorating climatic conditions with predominant arctic polar water inflow on the surface water masses off western svalbard possibly associated with summer insolation decline due to orbital forcing

the middle miocene climatic transition in the southern ocean evidence of paleoclimatic and hydrographic changes at kerguelen plateau from planktonic foraminifers and stable isotopes abstract middle miocene 14 8 11 9 ma deep sea sediments from odp hole 747a kerguelen plateau southern indian ocean contain abundant well preserved and diverse planktonic foraminiferal assemblages a detailed study of the climatic and hydrographic changes that occurred in this region during the middle miocene climatic transition led to the identification of an intense cooling phase the middle miocene shift abundance fluctuations of planktonic foraminiferal species with different paleoclimatic affinities and oxygen and carbon stable isotopes have been integrated in a multi proxy approach reconstruction of changes in foraminiferal faunal composition and diversity through time were the basis for identification of three foraminiferal biofacies the most prominent faunal change took place at 13 8 ma when a fauna with warm water affinity marked by high abundance of globorotalia miozea group and globoturborotalita woodi plexus was replaced by an oligotypic opportunistic fauna with typical polar characters and dominated by neogloboquadrinids this faunal change is interpreted as the result of foraminiferal migration from adjacent bioprovinces caused by modifications in climate and hydrography a positive 2 0 shift in 18o interpreted as the mi3 event and a related positive 1 0 shift in 13c corresponding to the cm6 event accompanied this faunal turnover these are interpreted to reflect substantial reorganization of southern ocean waters the northward migration of the polar front and a strong increase in primary productivity the second faunal change took place at 12 9 ma and was characterized by the gradual decrease in abundance of the neogloboquadrinids and the recovery of globorotalia praescitula scitula group and globigerinita glutinata a positive 1 5 shift in 18o interpreted as the mi4 event and a concurrent gradual negative shift in 13c accompanied this faunal change witnessing further modifications of the climate ocean system variations in sea surface temperature considered as the main factor causing changes of surface hydrography at the kerguelen plateau seem to have been driven by obliquity and long term eccentricity thus suggesting a key role played by the astronomical forcing on the evolution of southern ocean dynamics during the middle miocene also an evident 1 2 myr modulation of the 13c record suggests a main control of the long term obliquity cycles on the carbon cycle dynamics particularly the mi3 cm6 events exactly fit with a node of the 1 2 myr modulation cycles this confirms the key role played by orbital parameters on high latitude temperatures and antarctic ice volume and indirectly on global carbon burial and or productivity this climatic transition was marked also by changes in surface hydrography from 14 8 to 13 8 ma an intermediate strength thermocline controlled by seasonality developed just below the photic zone weaker seasonality characterized the interval from 13 8 to 12 9 ma when the thermocline became shallower and sharper and favored intermediate water foraminifers from 12 9 ma seasonality increased again and an intermediate strength thermocline re developed

glacial differences of southern ocean intermediate waters in the central south pacific abstract southern ocean intermediate waters soiws such as antarctic intermediate water and subantarctic mode water play a key role in modulating the global climate on glacial interglacial time scales they link the southern ocean and the tropics via mechanisms such as oceanic tunneling that transport climatic signals across latitudes despite their importance the past evolution of the soiws in the central south pacific is largely unknown here we compare paired mg ca temperature stable carbon 13c and oxygen 18o isotope records from surface dwelling and deep dwelling planktic foraminifera to infer changes in the water column structure for the last 260 ka in the central south pacific 54 s our study focuses on the subsurface oceanographic variability controlled by soiws which are subducted at the subantarctic front our data show that the subsurface ocean in the central south pacific was colder and fresher during glacial stages than during the holocene 0 10 ka bp suggesting a general glacial enhanced presence of antarctic intermediate water in agreement with previous studies from the eastern equatorial pacific and the southeast pacific however the subsurface ocean salinity differs for both glacial stages with fresher condition during the last glacial maximum lgm 26 5 19 ka bp and more saline condition during the penultimate glacial maximum pgm 155 140 ka bp the 13c data also show contrasting conditions for both glacial time windows in the upper water column with a large depletion of 0 37 in 13c from the lgm values suggests a larger contribution of old low 13c deep waters at intermediate depths at the study site during the pgm plausibly due to stronger upwelling in high southern latitudes the dissimilar scenarios between the lgm and the pgm may have been caused by processes that are analogous to the phase switch in modern day southern annular mode

early neoproterozoic sequence stratigraphy and acritarch biostratigraphy eastern officer basin south australia abstract the early neoproterozoic torrensian latest tonian 800 750 ma succession in the central and eastern officer basin was deposited in an intra cratonic rift basin the outcropping pindyin sandstone consists of basal lowstand conglomerate and upward fining transgressive sandstone and is conformably overlain by marine highstand shale of the alinya formation in the giles 1 well the pindyin sandstone contains aeolian to fluvial deposits and is overlain by peritidal and sabkha sediments of the alinya formation seismic interpretation suggests that the succession is thin on the murnaroo platform and thickens toward the munyarai trough the two sedimentary provinces are separated by the ungoolya hinge which probably marks the southeastern margin of the fraser musgrave fold belt highstand organic rich shale in the alinya formation is probably an important petroleum source rock acritarchs occur in both chert and shale in the alinya formation and their distribution was probably controlled by sedimentary environments similar assemblages from outcrop and subsurface provide a reliable evidence for regional correlation the assemblages in giles 1 are dominated by benthic coccoids and contain many distinct spinose acritarchs which are particularly abundant in the subtidal grey shale whereas mainly phytoplankton is present in the chert the assemblage represented by trachyhystrichosphaera vidalii t aimica cymatiosphaeroides kullingii can be used for global correlation in the early neoproterozoic the abundant microfossils from the alinya formation and equivalent beds around the world probably indicate a microorganism explosion at 750 800 ma prior to the neoproterozoic glaciations thirty seven acritarchs spheroids and seven cyanobacterial filaments are briefly described in this study including 5 new species comasphaeridium tonium eoentophysalis gilesis goniosphaeridium alinyum gorgonisphaeridium pindyium and gorgonisphaeridium torrensium and a newly combined species archaeoellipsoides karatavicus comb nov

mg ca thermometry in planktic foraminifera improving paleotemperature estimations for g bulloides and n pachyderma left planktic foraminiferal mg ca ratios have become a fundamental seawater temperature proxy in past climate reconstructions due to the temperature dependence of mg uptake into foraminiferal calcite however empirical calibrations for single species from methodologically consistent data are still lacking here we present species specific calibrations of mg ca versus calcification temperature for two commonly used species of planktic foraminifera globigerina bulloides and neogloboquadrina pachyderma left based on a series of southern ocean and north atlantic core tops combining these new data with previously published data we derive an integrated g bulloides mg ca temperature calibration for mid and high latitudes of both hemispheres between 2 and 18 c where mg ca 1 006 0 032 e0 065 0 003 tiso r2 0 82 g bulloides is found to calcify deeper in the southern ocean 200 m than in the north atlantic top 50 m we also propose a mg ca temperature calibration to describe the temperature response in n pachyderma left that calcified away from the influence of sea ice in the southern ocean valid between 1 and 9 c of the form mg ca 0 580 0 016 e0 084 0 006 tiso r2 0 70 these calibrations account for uncertainties on mg ca measurements and calcification temperature that were carefully estimated and propagated using monte carlo iterations the 1 propagated error in mg ca derived temperatures is 1 1 c for g bulloides and 0 9 c for n pachyderma left for the presented data sets geographical extension of genotypes must be assessed when choosing to develop regional or global calibrations

particle fluxes to the interior of the southern ocean in the western pacific sector along 170 w abstract an array of five bottom tethered moorings with 19 parflux time series sediment trap at three depths 1 and 2 km below the surface and 0 7 km above the sea floor was deployed in the western pacific sector of the southern ocean along 170 w the five stations were selected to sample settling particles in the main hydrological zones of the southern ocean the sampling period spanned 425 days november 28 1996 january 23 1998 and was divided into 13 or 21 synchronized time intervals a total of 174 sequential samples were recovered and analyzed to estimate fluxes of total mass tmf organic carbon carbonate biogenic silica and lithogenic particles the fluxes of biogenic material were higher than anticipated challenging the notion that the southern ocean is a low productivity region organic carbon fluxes at 1 km depth within the polar frontal zone and the antarctic zone were relatively uniform 1 7 2 3 g m 2 yr 1 and about twice the estimated ocean wide average ca 1 g m 2 yr 1 carbonate fluxes were also high and uniform between the subantarctic front and ca 64 s 11 13 g m 2 yr 1 a large fraction of the carbonate flux in the antarctic zone was due to the presence of pteropod shells coccoliths were found only to the north of the polar front and calcium carbonate became the dominant phase in the subantarctic zone in contrast carbonate particles were nearly absent near 64 s latitudinal variations in biogenic silica fluxes were substantial the large opal flux 57 g m 2 yr 1 measured in the antarctic zone suggests that opal productivity in this region has been previously underestimated and helps to explain the high sedimentary opal accumulation often found south of the polar front unlike biogenic material fluxes of lithogenic particles were among the lowest measured in the open ocean 0 12 0 05 g m 2 yr 1 reflecting a very low dust input

planktonic foraminiferal fluxes in the santa barbara basin response to seasonal and interannual hydrographic changes results of a three year time series sediment trap experiment in the santa barbara basin indicate linkages between water column dynamics and variations in plankton fluxes on both seasonal and interannual time scales the two week collection interval utilized for this study allows evaluation of high frequency changes in the production and flux of planktonic foraminifera which are compared to those of siliceous microorganisms diatoms radiolaria and silicoflagellates annual hydrographic conditions in santa barbara basin are influenced by seasonal changes in insolation the wind field and source waters this study includes periods of weak to moderate el nino conditions followed by a transitional period to a non el nino state planktonic foraminiferal fluxes and species turnover are related to seasonal and interannual changes in source waters and water column conditions globigerina bulloides g quinqueloba and neogloboquadrina pachyderma dextral dominate the planktonic foraminiferal population in this location and are present throughout the year globigerina bulloides and g quinqueloba have similar flux patterns and highest fluxes occur in association with diatom blooms the flux patterns of g bulloides and g quinqueloba in general are inversely related to that of n pachyderma dextral globigerina quinqueloba seems to respond earlier to the onset of upwelling than g bulloides three temperature limited species neogloboquadrina dutertrei orbulina universa and globigerinoides ruber are present in lower numbers and show more restricted seasonal ranges in the thermal regime of the santa barbara basin n dutertrei like o universa disappears during upwelling neogloboquadrina dutertrei occurs in highest abundance when the water column is thermally stratified and there is a well developed deep chlorophyll maximum increased fluxes of globigerinoi ruber the most thermally restricted of the dominant species in the basin are associated with the presence of warm oceanic diatoms and warm water radiolarians total planktonic foraminiferal fluxes were lower in 1995 than during the previous two years which were characterized by el nino conditions

late quaternary palaeoceanography of the circumpolar deep water from the south tasman rise we use sediment cores from the south tasman rise str to reconstruct deepwater circulation in the southwest pacific sector of the southern ocean sediment cores md972106 45 09 s 146 17 e 3310 m water depth and gc34 45 06 s 147 45 e 4002 m water depth preserve records covering the last 160 k yr with chronology controlled by calibrated accelerator mass spectrometry radiocarbon dates and benthic foraminiferal 18o tied to specmap the stir benthic foraminiferal 13c records provide new 13c values for southern ocean deep water spanning the last 160 kyr at sites unlikely to be affected by variations in productivity the records establish that glacial benthic foraminifera cibicidoides spp 13c values are lower relative to interglacial values and are comparable to previous glacial benthic 13c records in the indian and pacific sectors of the southern ocean comparisons of the benthic foraminiferal 13c time series at the str are made with the equatorial pacific v19 30 and site 846 and the equatorial atlantic geob1115 the similarity of benthic 13c records at the str to the equatorial pacific suggest the southern ocean deep water mass closely tracked those of the deep pacific and the presence of a 13c gradient between the str and the equatorial atlantic suggests there was continual production of northern source deep water over the past 160 k yr

sequence stratigraphy and the interpretation of neoproterozoic earth history abstract the application of sequence stratigraphy to neoproterozoic successions is important for improving the resolution of time correlation within individual sedimentary basins and potentially at a global scale the methodology is illustrated in this paper by reference to two contrasting examples from the flinders ranges adelaide geosyncline of south australia where the younger part of the neoproterozoic to earliest cambrian succession 770 ma to 540 ma has been divided into thirteen unconformity bounded depositional sequences one of the most prominent sequence boundaries at or near the base of the wonoka formation is characterized by a series of buried canyons as much as 1 km deep high resolution sequence stratigraphic studies at umberatana syncline continue to support the view that the canyons were cut subaerially and filled by fluvial and shallow water sediments in contrast to the wonoka canyons sequence boundaries interpreted at the base of the nuccaleena formation seacliff sandstone and near the top of the abc range quartzite are relatively subtle with only limited evidence for erosion and valley incision four sequence boundaries at the level of the sturtian and marinoan varanger glacial deposits and in the vicinity of the precambrian cambrian boundary are thought to correlate with surfaces in the amadeus basin of central australia other prominent sequence boundaries including the wonoka canyons and surfaces within the upper part of the wonoka formation and at the base of the ediacara member of the rawnsley quartzite correspond with a relatively condensed section in the amadeus basin and their lateral persistence beyond the adelaide geosyncline is therefore difficult to evaluate given the lack of precision in biostratigraphy and isotope geochemistry in neoproterozoic rocks and in a marked departure from phanerozoic practice we recommend placement of a terminal proterozoic gssp at a sequence boundary a prime candidate in australia is the sequence boundary at the base of the nuccaleena formation seacliff sandstone immediately above the marinoan glacial rocks in the adelaide geosyncline and its likely correlative at or near the base of the gaylad sandstone in the amadeus basin

constraining foraminiferal calcification depths in the western pacific warm pool highlights first apparent calcification depth assessment of living foraminifera in the se wpwp deep surface mixed layer causes deep apparent calcification depths deep dwelling g hexagonus traces nutrient conditions in equatorial water masses abstract insight into past changes of upper ocean stratification circulation and nutrient signatures rely on our knowledge of the apparent calcification depth acd and ecology of planktonic foraminifera which serve as archives for paleoceanographic relevant geochemical signals the acd of different species varies strongly between ocean basins but also regionally we constrained foraminiferal acds in the western pacific warm pool manihiki plateau by comparing stable oxygen and carbon isotopes 18ocalite 13ccalcite as well as mg ca ratios from living planktonic foraminifera to in situ physical and chemical water mass properties temperature salinity 18oseawater 13cdic our analyses point to globigerinoides ruber as the shallowest dweller followed by globigerinoides sacculifer neogloboquadrina dutertrei pulleniatina obliquiloculata and globorotaloides hexagonus inhabiting increasing greater depths these findings are consistent with other ocean basins however absolute acds differ from other studies the uppermost mixed layer species g ruber and g sacculifer denote mean calcification depths of 95 m and 120 m respectively these western pacific acds are much deeper than in most other studies and most likely relate to the thick surface mixed layer and the deep chlorophyll maximum in this region our results indicate that n dutertrei appears to be influenced by mixing waters from the pacific equatorial divergence while p obliquiloculata with an acd of 160 m is more suitable for thermocline reconstructions acds of g hexagonus reveal a deep calcification depth of 450 m in oxygen depleted but nutrient rich water masses consistent to other studies as the 13c of g hexagonus is in near equilibrium with ambient seawater we suggest this species is suitable for tracing nutrient conditions in equatorial water masses originating in extra topical regions

contribution of seasonal sub antarctic surface water variability to millennial scale changes in atmospheric co2 over the last deglaciation and marine isotope stage 3 the southern ocean is thought to have played a key role in past atmospheric carbon dioxide co2 atm changes three main factors are understood to control the southern ocean s influence on co2 atm via their impact on surface ocean pco2 and therefore regional ocean atmosphere co2 fluxes 1 the efficiency of air sea gas exchange which may be attenuated by seasonal or annual sea ice coverage or the development of a shallow pycnocline 2 the supply of co2 rich water masses from the sub surface and the deep ocean which is associated with turbulent mixing and surface buoyancy and or wind forcing and 3 biological carbon fixation which depends on nutrient availability and is therefore influenced by dust deposition and or upwelling in order to investigate the possible contributions of these processes to millennial scale co2 atm variations during the last glacial and deglacial periods we make use of planktonic foraminifer census counts and stable oxygen and carbon isotope measurements in the planktonic foraminifera globigerina bulloides and neogloboquadrina pachyderma sinistral from marine sediment core md07 3076q in the sub antarctic atlantic these data are interpreted on the basis of a comparison of core top and modern seawater isotope data which permits an assessment of the seasonal biases and geochemical controls on the stable isotopic compositions of g bulloides and n pachyderma s based on a comparison of our down core results with similar data from the southeast atlantic cape basin we infer past basin wide changes in the surface hydrography of the sub antarctic atlantic we find that millennial scale rises in co2 atm over the last 70 ka are consistently linked with evidence for increased spring upwelling and enhanced summer air sea exchange in the sub antarctic atlantic parallel evidence for increased summer export production would suggest that seasonal changes in upwelling and air sea exchange exerted a dominant influence on surface pco2 in the sub antarctic atlantic these results underline the role of southern ocean dynamics in particular their seasonal variations in driving millennial scale variations in co2 atm

finite amplitude evolution of instabilities associated with the coastal upwelling front abstract a primitive equation model is used to study the finite amplitude evolution of instabilities associated with the coastal upwelling front simulations of increasing complexity are examined that represent idealizations of summer conditions off the oregon coast including cases with steady and with time variable wind in a domain with alongshore uniform bathymetry and with time variable wind in a domain with realistic oregon coast bathymetry the numerical results indicate that the fastest growing mode in this system has approximately an 8 10 km alongshore wavelength but that once the disturbances grow to finite amplitude the predominant alongfront scale increases rapidly because of nonlinear effects separation of the total kinetic energy into contributions from the alongshore average flow and perturbation about that average shows that the initial growth of the perturbation kinetic energy is due to potential energy conversion but transfer of energy from the kinetic energy of the alongshore average

seasonal export and sediment preservation of diatomaceous foraminiferal and organic matter mass fluxes in a trophic gradient across the se atlantic abstract seasonal deposition fluxes of sinking phytoplankton zooplankton and major mass compounds i e calcium carbonate biogenic opal and organic matter intercepted by deep moored sediment traps are contrasted with their sediment accumulation rates over the 2700 m deep central walvis ridge in the oligotrophic se atlantic these data provide the first seasonally resolved record of biogenic particle fluxes in the south atlantic central gyre and serve as the oligotrophic end member of a gradient across the benguela system to the highly productive coastal upwelling off namibia maximum fluxes at the central walvis ridge were deposited in early austral spring following winter deepening of the surface mixed layer and associated nutrient entrainment nearly 25 of the annual mass flux arrived in october when sea surface temperature rose deep vertical mixing halted and surface production collapsed the annual flux of diatoms was dominated by small specimens of nitzschia bicapitata 60 whereas globorotalia inflata dominated the foraminiferal fluxes 25 diatom diversity dropped significantly during the bloom periods when up to 80 was composed of small n bicapitata but foraminiferal diversity remained about constant the diatom flux maximum together with those of biogenic silica and organic matter preceded those of the foraminifera pteropods carbonate and total mass by 1 week fluxes of the left and right coiled shells of the deep dwelling foraminifer globorotalia truncatulinoides peaked in different seasons a distinctive ecological behaviour which merits their taxonomic recognition as separate species these findings testify to recent evidence for the existence of several genetic species within g truncatulinoides and now suggest that such species may also have different seasonal responses the benguela trophic gradient showed a shoreward increase in particle fluxes but differences were surprisingly small testifying to only moderately enhanced export productivity and deposition at the namibian margin relative to the oligotrophic central gyre from the open ocean toward coastal upwelling small and weakly silicified diatoms were substituted by other larger and more heavily silicified species possibly in response to decreased silica limitation foraminiferal deposition fluxes were increasingly dominated by g inflata accompanied by a change over from many warm to few cold water minor species the late winter maximum at the namibian margin and the early spring maximum at the central walvis ridge were generated by the same process of collapsing surface productivity in response to the shut down of nutrient entrainment at the winter to summer transition although delayed by up to 2 months in the central gyre at the sediment water interface intense degradation of organic matter and biogenic silica resulted in poor preservation accompanied by pronounced changes in the species composition of siliceous phytoplankton of all particle groups at the central walvis ridge only the export of foraminiferal shells appeared to be fully transferred into the sediment and through their species assemblage to provide a sedimentary record of past seasonal productivity conditions of the upper ocean

globally synchronous marinoan deglaciation indicated by u pb geochronology of the cottons breccia tasmania australia u pb zircon data from the uppermost cottons breccia representing the marinoan glacial postglacial transition on king island tasmania provide the first direct age constraint on the cryogenian ediacaran boundary in australia zircons in four samples from the topmost meter of the cottons breccia dated by sensitive high resolution ion microprobe exhibit two modes ca 660 ma and ca 635 ma the younger component predominates in the uppermost sample a possibly volcanolithic dolomitic sandstone apparently lacking glacially transported debris in the transition to cap carbonate chemical abrasion thermal ionization mass spectrometry ca tims u pb dating of euhedral zircons from that sample yields a weighted mean age of 636 41 0 45 ma equivalence to published tims ash bed dates from cryogenian ediacaran transitional strata in namibia 635 51 0 82 ma within glacial deposit and china 635 23 0 84 ma 2 m above glacial deposit supports correlation of those strata to the australian type sections and globally synchronous deglaciation at the end of the cryogenian period

neoproterozoic microfossils from the margin of the east european platform and the search for a biostratigraphic model of lower ediacaran rocks abstract a ca 600 m thick siliciclastic succession in northern russia contains abundant and diverse microfossils that document early to middle ediacaran deposition along the northeastern margin of the east european platform the vychegda formation is poorly exposed but is well documented by a core drilled in the timan trough region kel tminskaya 1 borehole vychegda siliciclastics lie unconformably above tonian to lower cryogenian strata and below equivalents of the late ediacaran redkino succession that is widely distributed across the platform the basal 10 m of the formation preserve acritarchs and fragments of problematic macrofossils known elsewhere only from pre sturtian successions in contrast the upper nearly 400 m of the succession contains abundant and diverse large acanthomorphic acritarchs attributable to the ediacaran complex acanthomorph palynoflora ecap this distinctive set of taxa is known elsewhere only from lower but not lowermost ediacaran rocks in between lies an additional assemblage of relatively simple filaments and stratigraphically long ranging sphaeromorphic acritarchs interpreted as early ediacaran in age bearing in mind that knowledge of late cryogenian post strurtian pre marinoan microfossils is sparse the vychegda record is consistent with data from australia and china which suggest that diverse ecap microfossil assemblages appeared well into the ediacaran period accumulating paleontological observations underscore both the promise and challenges for the biostratigraphic characterization of the early ediacaran period

planktonic foraminiferal δ13c records from southern ocean sediment traps new estimates of the oceanic suess effect the carbon isotopic composition is measured for three species of planktonic foraminifera globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s from southern ocean sediment traps the sediment traps represent the annual flux of foraminifera in subtropical to polar frontal environments from the western pacific southern australia sector comparison between the seasonal 13c composition of the foraminifera and estimated 13c of dissolved inorganic carbon dic allows disequilibrium effects to be determined disequilibrium exhibits a latitudinal trend with greatest offsets from equilibrium at lower latitudes this effect causes a north to south increase in foraminiferal 13c while the 13cdic displays a decrease across these latitudes disequilibrium in g bulloides can be accounted for by changes in temperature the relationship between disequilibrium and temperature which we derive in this field study is consistent with the laboratory relationship of bemis et al 2000 corrected 13c for g bulloides is closely correlated to seasonal changes in nutrients at each site indicating the utility of g bulloides 13c as a nutrient tracer in southern ocean environments comparison between flux weighted sediment trap values and nearby core tops indicates a modern depletion in 13c which we attribute to the oceanic suess effect the imprint of this effect on the foraminiferal isotopes provides further evidence for the equilibration between surface waters and the atmosphere in the subantarctic zone

planktonic foraminiferal flux seasonality in subantarctic sediment traps a test for paleoclimate reconstructions sediment trap moorings deployed during 1997 and 1998 in the subantarctic to polar frontal regions of the southern ocean reveal distinct seasonality in foraminiferal flux foraminiferal assemblages vary between each site yet major species exhibit very similar patterns of seasonal succession which can be associated with changes in mixed layer depth enhanced foraminiferal productivity is also associated with periods of high biogenic silica and particulate organic carbon flux on a broader scale foraminiferal assemblages are strongly delineated by temperature temperature estimates derived from the assemblages using the modern analog technique mat are mostly within 2 5 c of the satellite advanced very high resolution radiometer temperatures observed during the deployment period this indicates that core top sediments included in the mat database do reflect modern observed conditions at the sea surface providing a robust technique for estimating past temperature change from foraminiferal assemblages in southern ocean environments

calcite dissolution and the modification of planktonic foraminiferal assemblages abstract the results of an in situ experiment in the panama basin allow us to determine the way in which planktonic foraminiferal assemblages are modified by calcite dissolution pre weighed planktonic foraminiferal samples of known species composition were attached to a deep sea mooring at various water depths between 665 m and 3791 m for a period of 123 days weight loss due to dissolution during this period ranged from less than 5 for the shallowest samples to slightly over 30 for the deepest samples in terms of change in foraminiferal number this is equivalent to decreases of between 1 and 26 only in the samples placed at the two deepest levels 3769 m and 3791 m was there a significant loss in the total number of foraminifera the magnitude of change in the abundance of individual species in early related to their different susceptibilities to dissolution species such as hastigerina pelagica globigerinella aequilateralis and candeina nitida which are very susceptible to dissolution exhibited the largest decreases in frequency percentage while the more resistent species sphaeroidinella dehiscens pulleniatina obliquiloculata and globorotalia truncatulinoides had minimal changes from these results a solution susceptibility ranking for planktonic foraminifera is established that is quite similar to those derived from previous laboratory experiments and sea floor studies

top marine predators track lagrangian coherent structures meso and submesoscales fronts eddies filaments in surface ocean flow have a crucial influence on marine ecosystems their dynamics partly control the foraging behavior and the displacement of marine top predators tuna birds turtles and cetaceans in this work we focus on the role of submesoscale structures in the mozambique channel in the distribution of a marine predator the great frigatebird using a newly developed dynamic concept the finite size lyapunov exponent fsle we identified lagrangian coherent structures lcss present in the surface flow in the channel over a 2 month observation period august and september 2003 by comparing seabird satellite positions with lcs locations we demonstrate that frigatebirds track precisely these structures in the mozambique channel providing the first evidence that a top predator is able to track these fsle ridges to locate food patches after comparing bird positions during long and short trips and different parts of these trips we propose several hypotheses to understand how frigatebirds can follow these lcss the birds might use visual and or olfactory cues and or atmospheric current changes over the structures to move along these biologic corridors the birds being often associated with tuna schools around foraging areas a thorough comprehension of their foraging behavior and movement during the breeding season is crucial not only to seabird ecology but also to an appropriate ecosystemic approach to fisheries in the channel

δ18o seasonality of planktonic foraminifera from southern ocean sediment traps latitudinal gradients and implications for paleoclimate reconstructions abstract the oxygen isotopic record obtained from globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s was analysed for 5 sediment traps moored in the southern ocean and southwest pacific the traps extend from subtropical to the polar frontal environments providing the first analysis of seasonal foraminiferal 18 o records from these latitudes comparison between the foraminiferal records and various equations for predicted 18 o of calcite reveals that the predicted 18 o is best captured by the equations of epstein et al 1953 epstein s buchsbaum r lowenstam h a urey h c 1953 revised carbonate water isotopic temperature scale geological society of america bulletin 64 1315 1326 and kim and o neil 1997 kim s t o neil j r 1997 equilibrium and non equilibrium oxygen isotope effects in synthetic carbonates geochimica et cosmochimica acta 61 3461 3475 the epstein equation shows a constant offset from the 18 o of g bulloides and n pachyderma s across the full range of latitudes the seasonal range in 18 o values for these two species implies a near surface habitat across all sites while g inflata most likely dwells at 50 m depth a significant finding in this study was that offsets from predicted 18 o for g bulloides do not correlate to changes in the carbonate ion concentration this suggests that co 3 2 in and of itself may not capture the full range of carbonate chemistry conditions in the marine system this sediment trap deployment also reveals distinct seasonal flux patterns for each species comparison between flux weighted isotopic values calculated from the sediment traps and the isotopic composition of nearby surface sediments indicates that the sedimentary records retain this seasonal imprint at the 51 s site g bulloides has a spring flux peak while n pachyderma s is dominated by summer production the imprint of these differing seasonal production patterns on the flux weighted 18 o values results in more depleted 18 o for n pachyderma s than for g bulloides interpretations of n pachyderma s isotopic composition as a record of subsurface conditions may therefore need to be refined with implications for interpretation of depleted glacial 13 c for this species sigman boyle 2000 sigman d m boyle e a 2000 glacial interglacial variations in atmospheric carbon dioxide nature 407 859 869

the paleoclimatic response of the southern californian margin to the rapid climate change of the last 60 ka a regional overview abstract high resolution planktonic foraminiferal census and stable isotope data from a core transect odp site 1017 893 and 1014 demonstrate remarkable similarities along the southern california margin during the last glacial 60 10 ka bp modern analog technique and 18 o derived sea surface temperatures sst demonstrate sst shifts were regionally expressed supporting the hypothesis that the relative strength of local surface ocean currents affected the advection of subpolar and subtropical water into the region divergent alkenone sst records suggest the flux of planktonic organisms shifted seasonally during the last glacial in response to changing environmental conditions when considered as seasonal sst reconstructions summer oligotrophic surface ocean conditions appear to have a muted response to orbital and millennial scale climate change compared to the surface ocean during high nutrient winter conditions

proliferation of miss forming microbial mats after the late neoproterozoic glaciations evidence from the kimberley region nw australia abstract a total of 20 morphological types of microbially induced sedimentary structures miss are recognized from the late neoproterozoic tillite bearing successions of the kimberley northwestern australia which include alpha petees triradiate cracks multidirectional linear ridges millimeter ripples erosional remnants and pockets and so on of these triradiate cracks multidirectional linear ridges and millimeter ripples are reported for the first time from the neoproterozoic worldwide most kimberley miss are morphologically comparable with their ancient and present day counterparts whose biogenicity have been well demonstrated in the kimberley during the interglacial period miss have colonization preference to relatively coarse sandy substrates ranford formation and their abundance decreased towards the younger strata throssell shale in contrast miss abundance increased from the older strata yurabi formation towards the younger strata flat rock formation during the postglacial period however overall both miss abundance and bedding plane coverage percentage increased from the marinoan younger marinoan gaskiers interglacial successions to younger marinoan gaskiers postglacial successions indicating a proliferation of microbial mats after the younger marinoan gaskiers glaciation the increase of microbial mats could have ameliorated marine biogeochemical conditions and ecosystems and thus laid the foundation for the rise of ediacaran biota in australian basins