estimating groundwater exchange with lakes 1 the stable isotope mass balance method groundwater inflow and outflow contributions to the hydrologic budget of lakes can be determined using a stable isotope 18o 16o mass balance method the stable isotope method provides a way of integrating the spatial and temporal complexities of the flow field around a lake thereby offering an appealing alternative to the traditional time and labor intensive methods using seepage meters and an extensive piezometer network in this paper the method is applied to a lake in northern wisconsin demonstrating that it can be successfully applied to lakes in the upper midwest where thousands of similar lakes exist inflow and outflow rates calculated for the wisconsin lake using the isotope mass balance method are 29 and 54 cm yr respectively which compare well to estimates derived independently using a three dimensional groundwater flow and solute transport model of 20 and 50 cm yr such a favorable comparison lends confidence to the use of the stable isotope method to estimate groundwater exchange with lakes in addition utilization of stable isotopes in studies of groundwater lake systems lends insight into mixing processes occurring in the unsaturated zone and in the aquifer surrounding the lake and verifies assumed flow paths based on head measurements in piezometers

assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures though many studies on the mg contents in the calcitic tests of foraminifers exist the processes controlling its uptake are still a matter of debate laboratory cultures offer an excellent opportunity to reveal these mechanisms the mg concentrations within single chambers of the planktic foraminifer globigerinoides sacculifer brady maintained under controlled laboratory conditions were measured 1 at variable temperatures 19 5 29 5 c and constant salinity and 2 at variable salinity 22 45 and constant temperature the experimental results suggest that under natural conditions temperature is the leading mechanism controlling the mg ca ratio temperature and magnesium are related proportionally a temperature increase of ca 10 c gives rise to an increase of the magnesium concentrations of ca 130 drastic unnatural salinity changes dominate the effects of temperature a 110 change in the mg ca ratio was observed when salinity was elevated or reduced by more than ca 10 specimens which underwent gametogenesis reveal significantly higher mg concentrations than specimens that did not release gametes partition coefficients for mg in foraminiferal calcite are orders of magnitude lower than values from inorganically precipitated calcite when comparing observed mg ca ratios of foraminiferal tests with predicted mg ca ratios calculated according to empirical equations it becomes evident that foraminiferal tests are undersaturated with respect to mg for the water temperature they have experienced apparently foraminifers are capable of controlling their mg concentration the physiological processes presumably responsible for such depressed mg ca ratios appear to be temperature controlled as deduced from the close relationship of the observed mg ca ratios and water temperature this study demonstrates that variations in temperature and salinity are definitely reflected in the mg content of foraminiferal tests magnesium may thus serve as a paleo proxy for past surface water temperatures as long as postdepositional changes and salinity variations are of subordinate importance or can be excluded

a modern isotope record of changes in water and carbon budgets in a groundwater fed lake blue lake south australia groundwater is often a major component of lake water and chemical balances alteration in catchment subsurface water balances through land use change and pumping can affect lake biogeochemical cycles through changes in groundwater flow rates we present a modern 200 yr sediment isotope record d 18 ocarb d 13 ccarb and d 13 corg o f changes to the water and carbon budget of blue lake which is situated in karstic limestone in south australia and is mostly fed by groundwater the 3 5 decrease in d 18 ocarb and d 13 ccarb deposited in lake sediments since 1850 reflects higher rates of groundwater through flow due to rainfall variability land use change and increased rates of pumping over the past 40 yr calculated water residence times based on the isotopic data were 23 6 2 yr before 1850 and decreased by the late twentieth century to 8 6 2 yr concomitant dissolved inorganic carbon dic residence times were 3 8 and 2 2 yr respectively although burial rates of caco3 have increased by about threefold over the past 40 yr there is no evidence that substantial changes in organic carbon deposition has occurred the shorter dic residence time is largely due to increased input and higher co2 evasion rates about 88 of ccarb and 96 of corg generated within the water column is remineralized but the isotopic composition is essentially unaltered in the sediments the measured variations in d 13 ccarb and d 13 corg of sediments are thought to reflect changes to dic residence time and increased co2 aq concentrations rather than changes in lake productivity

foraminiferal mg ca evidence for southern ocean cooling across the eocene oligocene transition constraining the magnitude of high latitude temperature change across the eocene oligocene transition eot is essential for quantifying the magnitude of antarctic ice sheet expansion and understanding regional climate response to this event to this end we constructed high resolution stable oxygen isotope 18o and magnesium calcium mg ca records from planktic and benthic foraminifera at four ocean drilling program odp sites in the southern ocean planktic foraminiferal mg ca records from the kerguelen plateau odp sites 738 744 and 748 show a consistent pattern of temperature change indicating 2 3 c cooling in direct conjunction with the first step of a two step increase in benthic and planktic foraminiferal 18o values across the eot in contrast benthic mg ca records from maud rise odp site 689 and the kerguelen plateau odp site 748 do not exhibit significant temperature change the contrasting temperature histories derived from the planktic and benthic mg ca records are not reconcilable since vertical 18o gradients remained nearly constant at all sites between 35 0 and 32 5 ma based on the coherency of the planktic mg ca records from the kerguelen plateau sites and complications with benthic mg ca paleothermometry at low temperatures the planktic mg ca records are deemed the most reliable measure of southern ocean temperature change we therefore interpret a uniform cooling of 2 3 c in both deep surface thermocline waters and intermediate deep waters of the southern ocean across the eot cooling of southern ocean surface waters across the eot was likely propagated to the deep ocean since deep waters were primarily sourced on the antarctic margin throughout this time interval removal of the temperature component from the observed foraminiferal 18o shift indicates that seawater 18o values increased by 0 6 0 15 across the eot interval corresponding to an increase in global ice volume to a level equivalent with 60 130 modern east antarctic ice sheet volume

a simple evaluation of cleaning procedures on fossil benthic foraminiferal mg ca 1 recent studies suggest that benthic foraminiferal mg ca may be useful in reconstructing deep water temperature changes during the quaternary and on longer timescales rosenthal et al 1997 lear et al 2000 martin et al 2002 because changes in deep water temperature may be small sample preparation could play an important role in reconstructing accurate temperatures from shell mg ca a simple examination of changes in measured shell chemistry of benthic foraminifera from two intervals subjected to increasingly rigorous cleaning reveals that fossil benthic foraminiferal samples cleaned by oxidation yield lower mg ca values than samples only rinsed and weak acid leached reductive cleaning further lowered the shell mg ca of one of the two benthic species examined lower mg ca values following oxidation and reduction appear to reflect removal of contaminant mg associated with remnant organic matter and adsorbed phases

fidelity of radially viewed icp oes and magnetic sector icp ms measurement of mg ca and sr ca ratios in marine biogenic carbonates are they trustworthy together improving interlaboratory reproducibility in both precision and accuracy of mg ca and sr ca determination in marine biogenic carbonates is critical in optimizing their utility as paleothermometers coupled with a need for uniform sample cleaning practices there is a need for more exacting methods and procedures across laboratories using varied instrumentation here we employ an intensity ratio matrix effect correction methodology to a suite of solution standards and biogenic carbonates foraminifera tests and a gastropod shell to investigate short term and long term mg ca and sr ca precision and accuracy by different instruments a magnetic sector inductively coupled plasma mass spectrometer icp ms and a radially viewed inductively coupled plasma optical emission spectrophotometer icp oes over an extended 1 0 24 5 mm ca concentration range both instruments have significant ca matrix effects for mg ca and somewhat less for sr ca over our working ca range 1 8 mm ca mg ca matrix effects are significant requiring correction and sr ca matrix effects are small to negligible occasionally requiring correction linear or logarithmic fit using a suite of matrix standards for both instruments the short term intrarun precision for a suite of solution standards is 0 2 1 rsd for mg ca and sr ca for both instruments a long term interrun precision of 0 9 is demonstrated for mg ca and 0 6 for sr ca on both instruments the accuracy of measured mg ca and sr ca values for short and long term standards is similar on both instruments at better than 1 0 5 on par with our long term precision an interinstrument comparison of the same measured suite of biogenic carbonates demonstrates that after accounting for matrix effects data generated on either instrument are essentially interchangeable within analytical precision to a high degree of fidelity

determination of element ca ratios in foraminifera and corals using cold and hot plasma techniques in inductively coupled plasma sector field mass spectrometry abstract we have developed a rapid and precise procedure for measuring multiple elements in foraminifera and corals by inductively coupled plasma sector field mass spectrometry icp sf ms with both cold 800 w radio frequency rf power and hot 1200 w rf power plasma techniques our quality control program includes careful subsampling protocols contamination free workbench spaces and refined plastic ware cleaning process element ca ratios are calculated directly from ion beam intensities of 24mg 27al 43ca 55mn 57fe 86sr and 138ba using a standard bracketing method a routine measurement time is 3 5 min per dissolved sample the matrix effects of nitric acid and ca and sr levels are carefully quantified and overcome there is no significant difference between data determined by cold and hot plasma methods but the techniques have different advantages the cold plasma technique offers a more stable plasma condition and better reproducibility for ppm level elements long term 2 sigma relative standard deviations 2 rsd for repeat measurements of an in house coral standard are 0 32 for mg ca and 0 43 for sr ca by cold plasma icp sf ms and 0 69 for mg ca and 0 51 for sr ca by hot plasma icp sf ms the higher sensitivity and enhanced measurement precision of the hot plasma procedure yields 2 rsd precision for mol mol trace elements of 0 60 mg ca 9 9 al ca 0 68 mn ca 2 7 fe ca 0 50 sr ca and 0 84 ba ca for an in house foraminiferal standard our refined icp sf ms technique which has the advantages of small sample size 2 4 g carbonate consumed and fast sample throughput 5 8 samples hour should open the way to the production of high precision and high resolution geochemical records for natural carbonate materials

the water balance of a small lake using stable isotopes and tritium abstract a small maar lake known as the blue lake set in a karstic region of southeastern australia provides the municipal water supply for a population of 20 000 the lake has a volume of 3 6 10 7 m 3 of which 10 15 is pumped from it each year the lake is recharged almost entirely from groundwater and the main objective of this study was to estimate the total groundwater inflow and outflow rates estimation of groundwater throughflow in a lake is difficult to assess using classical hydrological techniques and an alternative method involving measurement of the concentrations of the environmental isotopes 3 h 18 o 2 h and 14 c in the lake water and in the recharging groundwater was used to establish the lake water balance the water balance calculations indicated a total groundwater inflow to blue lake of between 5 0 10 6 and 6 5 10 6 m 3 yr 1 corresponding to a residence time of water in the lake of 6 yr it was not possible to derive the relative proportions of inflow to the lake from the two possible source aquifers using these isotopes because their concentrations did not show a sufficiently large contrast to distinguish the two water sources

heterogeneous diagenetic patterns in the pleistocene ironshore formation of grand cayman british west indies abstract the ironshore formation on grand cayman consists of six unconformity bounded units a to f that developed in response to repeated transgressive regressive cycles during the middle to late pleistocene corals and matrices in limestones from the rogers wreck point rwp offshore george town gt and western onshore wo areas are characterized by complex diagenetic fabrics that reflect marine bioerosion micrite envelopes internal sediments fibrous high mg calcite acicular aragonite isopachous prismatic calcite cements freshwater phreatic circumgranular cements even random blocky calcite cements and vadose meniscus calcite cements blocky calcite cements diagenesis throughout these limestones the matrices have undergone more meteoric diagenetic alteration than the corals overall however no systematic stratigraphic patterns exist to the distribution of these diagenetic fabrics and it is generally impossible to link the different phases of diagenesis with specific unconformities that cap each unit these heterogenous patterns of diagenetic features can be attributed to many intrinsic and extrinsic factors including the original compositions of the different components in the limestones the porosity and permeability of the substrate the nature of the diagenetic fluids climate and the duration of exposure during each lowstand integration of available data however indicates that maximum diagenesis took place during the lowstands denoted by the unconformities at the top of unit c marine isotope stage 7 and unit d marine isotope stage 5e when long periods of exposure were accompanied by wet climates with high annual rainfalls

a 200 ka pollen and oxygen isotopic record from two sediment cores from the eastern arabian sea abstract we present here a pollen record from the northern indian ocean that goes back to 200 ka the boundary between marine isotopic stages mis 7 and 6 pollen oxygen isotopic composition and organic carbon have been examined for two sediment cores from the eastern arabian sea 15 02 n and 71 41 e 13 16 n and 71 00 e to reconstruct the long term palaeoclimate and palaeovegetation of the indian subcontinent oxygen isotope data suggest that glacial periods mis 2 4 and 6 are characterised by low precipitation because of a weak southwest monsoon and a strong northeast monsoon in contrast interglacial periods mis 1 3 and 5 are marked by high fresh water input resulting from a strong southwest monsoon during the last glacial interglacial cycle sea surface temperature and surface salinity changed as a result of variations in the evaporation precipitation e p balance throughout the core the dominant pollen types are poaceae and chenopodiaceae and or amaranthaceae 50 their dominance during glacial periods mis 2 4 and 6 suggests that the climate was cold and dry this dominance is also suggestive of salinity tolerant vegetation colonizing large areas near seashore due to lower sea level or high e p conditions during interglacial periods mis 1 3 and 5 when there was high precipitation the arid taxa were sparse whereas poaceae and piperaceae were abundant hence chenopodiaceae and or amaranthaceae and artemisia are suggestive of cold and arid semi arid climate and poaceae and piperaceae of warm and wet conditions mangrove pollen is not well represented in the cores

the evolution of the equatorial thermocline and the early pliocene el padre mean state the tropical pacific thermocline strength depth and tilt are critical to tropical mean state and variability during the early pliocene 3 5 to 4 5 ma the eastern equatorial pacific eep thermocline was deeper and the cold tongue was warmer than today which resulted in a mean state with a reduced zonal sea surface temperature gradient or el padre however it is unclear whether the deep thermocline was a local feature of the eep or a basin wide condition with global implications our measurements of mg ca of globorotalia tumida in a western equatorial pacific site indicate pliocene subsurface temperatures warmer than today thus el padre included a basin wide thermocline that was relatively warm deep and weakly tilted at 4 ma thermocline steepening was coupled to cooling of the cold tongue since 4 ma the basin wide thermocline cooled shoaled gradually with implications for thermocline feedbacks in tropical dynamics and the interpretation of tex86 derived temperatures

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

assessing coral sr ca sst calibration techniques using the species diploria strigosa the coral species diploria strigosa is a promising archive for paleoclimate reconstruction in the tropical atlantic but limited work has been accomplished thus far to quantify the relationship between strontium to calcium ratios and sea surface temperatures in this species in this study we collected three modern d strigosa coral colonies from anegada british virgin islands to refine the use of this species as a paleoclimate archive three regression techniques including ordinary least squares reduced major axis and weighted least squares were used to assess how assumptions implicit in these regression methods influence the calibration our analysis demonstrated that regression slopes were strongly impacted by the assumptions about data uncertainty we recommend using the unbiased weighted least squares regression technique for calibrating the sr ca paleothermometer especially when precise local sea surface temperature data are unavailable combining our sr ca data with previously published data from this species results in a multi site multi colony temperature sensitivity of 0 046 0 001 mmol mol c for mean centered monthly data 0 059 0 001 mmol mol c for monthly anomalies and 0 063 0 004 for annual anomalies we suggest these relationships are the best available characterization of the temperature dependence of sr ca in d strigosa and can be utilized in future paleoclimate reconstructions

an intensity ratio calibration method for the accurate determination of mg ca and sr ca of marine carbonates by icp aes an inductively coupled plasma atomic emission spectroscopy icp aes method for the accurate and precise simultaneous measurement of the mg ca and sr ca content of carbonates was established while a precision of 0 3 1 standard deviation sd is easily obtainable for both mg ca and sr ca analysis a ca matrix effect complicates achieving similar levels of accuracy with conventional calibration procedures an alternative ratio calibration procedure is proposed which overcomes the ca matrix effects and ensures the accuracy of the mg ca and sr ca analysis of marine carbonates to 0 3 almost an order of magnitude better than conventional calibration methods the longer term precision is 0 1 if the batch run average values are corrected for longer term drift the method is suitable for analysis of foraminiferal calcite and coral aragonite and can easily be adjusted for the analysis of other carbonates or microsamples

rapid analysis of high precision sr ca ratios in corals and other marine carbonates a method for rapid determination of high precision sr ca ratios in scleractinian corals is presented using an inductively coupled plasma atomic emission spectrophotometer samples are corrected for instrument drift using a reference solution similar to the approach used for analysis of stable isotopes using gas source mass spectrometry further correction for variation of the sr ca ratio with ca concentration is accomplished using internal standards the precision once all corrections have been made is better than 0 1 relative standard deviation 1 for samples of similar ca concentration and better than 0 2 for samples with variable ca concentrations this method increases the sample throughput by approximately a factor of 20 relative to thermal ionization mass spectrometry and significantly reduces instrument and per sample costs comparison of sr ca data for a coral from the galapagos islands with an instrumental temperature record shows excellent agreement and demonstrates the potential for application of this technique to samples of modern and fossil scleractinian corals and other marine carbonates including foraminifera

sst artifacts in coral proxy records produced by early marine diagenesis in a modern coral from rabaul papua new guinea 1 we investigated the effects of early marine diagenesis on the skeletal geochemistry of a porites coral collected live offshore of rabaul papua new guinea the lowermost 14 cm of the 1 9 m coral core contains physical evidence of alteration which is clearly visible in x radiograph sem and petrography images abrupt and significant increases in coral 18o and sr ca and decreases in coral mg ca occur at the transition from unaltered to altered skeleton all of which imply significant sst cooling if the altered nature of the coral skeleton went unrecognized screening for the effects of early marine diagenesis should become a standard procedure in coral climate studies

impact of skeletal dissolution and secondary aragonite on trace element and isotopic climate proxies in porites corals restricted zones of recent dissolution and secondary aragonite infilling were identified in a coral core collected in 1986 from a living massive porites colony from the central great barrier reef australia secondary aragonite needles 20 m long cover skeletal surfaces deposited from 1972 to late 1974 and increase bulk density by 10 dissolution is observed above this zone whereas older skeleton is pristine we investigate the impact of both types of early marine diagenesis on skeletal geochemistry and coral paleoclimate reconstructions by comparison with similar records from eight contemporary porites colonies collected at nearby reefs secondary aragonite overgrowth causes anomalies in skeletal density mg ca sr ca u ca o and c the secondary aragonite is consistently associated with a cool temperature anomaly for each of the sea surface temperature sst proxies o sst 1 6 c sr ca sst 1 7 c mg ca sst 1 9 c u ca sst 2 8 c dissolution through incongruent leaching also causes cool sst artifacts but only for trace element ratios mg ca sst 1 2 c sr ca sst 1 2 c u ca sst 2 1 c the sequence of preference with respect to dissolution of coral skeleton in seawater is mg ca sr u rigorous screening of coral material for paleoclimate reconstructions is therefore necessary to detect both dissolution and the presence of secondary minerals the excellent agreement between apparent sst anomalies generated by different modes of diagenesis means that replication of tracers within a single coral cannot be used to validate climate proxy interpretations poor replication of records between different coral colonies however provides a strong indication of nonclimatic artifacts such as dissolution and secondary aragonite copyright 2007 by the american geophysical union

temporal and spatial variations in the diagenetic fabrics and stable isotopes of pleistocene corals from the ironshore formation of grand cayman british west indies abstract on grand cayman the unconformity bounded units a to f in the ironshore formation represent repeated cycles of deposition and subaerial exposure that were associated with the dramatic oscillations in sea levels that characterized the middle to late pleistocene montastrea annularis and acropora palmata the dominant corals found in units a to f in the rogers wreck point area and offshore george town area reflect these changes with their complex mosaics of marine aragonite cements bioerosion internal sediments and meteoric calcitization of coral skeleton dissolution diagenetic features the distribution of the diagenetic fabrics throughout this sequence however is not predictable the randomness in the degree of skeletal calcitization is shown by the lack of systematic variation in calcitization from units a to f and the fact that the degree of skeletal calcification in m annularis is higher than that in a palmata in the rogers wreck point area but less than in a palmata in the george town cores the stable isotope compositions 13c 18o of the corals from units a to f plot along the same trend line with their positions on that trend reflecting the amount of meteoric diagenesis they have undergone the variable styles and degrees of diagenesis evident in the corals from the ironshore formation reflect 1 the variable impact of intrinsic e g skeletal architecture porosity of coral and extrinsic e g sea level climate factors during each phase of diagenesis and 2 temporal effects associated with the diagenetic overprinting that took place during each successive phase of diagenesis this means that the diagenetic fabrics are not stratigraphically ordered and that it is impossible to correlate specific diagenetic phases with specific sea level lowstands or highstands

mg ca sr ca and stable isotope δ18o and δ13c ratio profiles from the fan mussel pinna nobilis seasonal records and temperature relationships 1 we present new annually resolved 18o 13c mg ca and sr ca ratio records for two shells of the fast growing mediterranean fan mussel pinna nobilis collected from proximal spanish coast sea grass meadows the relationship between the potential geochemical proxies and ontogenetic and environmental controlling factors is investigated specifically the use of shell mg ca and sr ca ratios as potential calcification temperature proxies the latter calculated from measured shell 18o values has been assessed the 18o cycles along the growth axis indicate that our p nobilis specimens are 10 5 and 4 5 years old shell sr ca ratios do not exhibit any consistent interannual cyclicity and are not correlated to temperature a subtle ontogenetic effect on shell mg ca ratios was observed during the first 4 5 years of recorded growth but was highly evident during the organism s later growth years in p nobilis shells different mechanisms influence ontogenetic variation in shell mg ca and 18o records shell mg ca ratios from the first 4 5 years of growth correlate significantly to temperature in a best fit relationship described by the equation mg ca 17 16 1 95 exp 0 022 0 004 t p nobilis shell mg ca records therefore are a valid temperature proxy only during an early growth phase for the same range of temperatures shell mg ca ratios in p nobilis are approximately 1 3 lower than those reported for inorganic calcite but 3 to 4 times higher than in another bivalve species mytilus trossulus and 4 to 16 times higher than in foraminifera we suggest these offsets are due to a higher degree of similarity between seawater and calcification fluid composition in p nobilis than in other bivalves and foraminifera the observed shell mg ca ratio change per c of 2 2 also is lower than that observed for inorganic and other biogenic calcites our findings strongly support taxon and species specific mg ca temperature relationships for bivalves and other calcifying organisms an appreciation of the physiology and calcification mechanisms of any biogenic carbonate archive therefore is paramount prior to the application of stable isotope and element ca ratio proxies for paleotemperature reconstructions

early marine diagenesis in corals and geochemical consequences for paleoceanographic reconstructions detecting the potential geochemical consequences of early marine diagenesis is essential for establishing the validity of past climate reconstructions from coral we present coral skeletal 18o and sr ca data for two long coral cores spanning 1839 1994 ad at ningaloo reef western australia one of which includes significant secondary precipitation of marine inorganic aragonite long term trends in reconstructed sea surface temperatures ssts for the well preserved coral correlate strongly with instrumental sst records spanning the 20th century in contrast the 18o and sr ca for the diagenetically altered coral give identical cool sst anomalies of 4 5 c as a consequence of the addition of secondary aragonite enriched in 18o and sr our results indicate that cross checking of paleoclimate reconstructions with two supposedly independent paleothermometers may not be valid and that coral records showing cooler ssts in the past need to be interpreted with caution furthermore modern coral records with long term trends in 18o indicating recent warming and freshening of the ocean can be potentially explained by early marine diagenesis

geochemical mass balance of a volcanic crater lake in australia abstract the recharge regime of blue lake a freshwater crater lake has been determined by using the environmental tracers uranium and calcium partly precipitated in the sediments and sodium and chloride conserved in the lake s waters the geochemical mass balances allowed best estimates of the water budget to be derived these are inflow rate from groundwater of 5 10 6 m 3 yr 1 the outflow rate into the groundwater is therefore about 1 10 6 m 3 yr because the measured pumping rate is 4 10 6 m 3 yr 1 the unconfined gambier limestone aquifer contributes 85 to the inflow and receives 100 of the outflow the lower lying aquifer dilwyn formation fluviatile sediments contributes 15 to the inflow the techniques used to interpret the chemical data of concentrations of the dissolved environmental constituents are described actual concentrations in range of magnitude whose contrasts between the lake and the two aquifers enabled the approach to be used were na 60 160 mg 1 1 cl 75 250 mg 1 1 ca 40 150 mg 1 1 and u 0 005 1 3 g 1 1

surface water groundwater interaction near shallow circular lakes flow geometry in three dimensions steady flow regimes for three dimensional lake aquifer systems are studied via idealized mathematical models that are extensions of earlier simplified vertical section models of interaction between shallow lakes and underlying aquifers the present models apply to a shallow circular lake at the surface of a rectangular aquifer of finite depth yielding a truly three dimensional representation of the resulting flow system flux boundary conditions are applied at the ends of the aquifer with net vertical recharge or evapotranspiration at the water table the lake is defined by a region with constant head by determining and visualizing solutions to the discretized saturated flow equations a range of possible flow regimes is identified and their topological properties are studied tools for analyzing flow regimes are described including a method for locating and mapping three dimensional dividing surfaces within steady flow fields results show strong similarities between two and three dimensional systems including a large number of flow through recharge and discharge regimes and reverse flow cells flow lines calculated on a vertical plane through the middle of a lake resemble but are not identical to two dimensional streamlines for a range of aquifer flow and recharge conditions estimates of the widths and depths of capture and release zones for various lake aquifer geometries are asymptotic to earlier results for two dimensional systems numerical predictions are compared with analytical results for certain limiting flow regimes

palaeoenvironmental records from fossil corals the effects of submarine diagenesis on temperature and climate estimates the geochemistry of coral skeletons may reflect seawater conditions at the time of deposition and the analysis of fossil skeletons offers a method to reconstruct past climate however the precipitation of cements in the primary coral skeleton during diagenesis may significantly affect bulk skeletal geochemistry we used secondary ion mass spectrometry sims to measure sr mg b u and ba concentrations in primary coral aragonite and aragonite and calcite cements in fossil porites corals from submerged reefs around the hawaiian islands cement and primary coral geochemistry were significantly different in all corals we estimate the effects of cement inclusion on climate estimates from drilled coral samples which combine cements and primary coral aragonite secondary 1 calcite or not vert similar2 aragonite cement contamination significantly affects sr ca sst estimates by 1 c and 0 4 to 0 9 c respectively cement inclusion also significantly affects mg ca b ca and u ca sst estimates in some corals x ray diffraction xrd will not detect secondary aragonite cements and significant calcite contamination may be below the limit of detection not vert similar1 of the technique thorough petrographic examination of fossils is therefore essential to confirm that they are pristine before bulk drilled samples are analysed to confirm that the geochemistry of the original coral structures is not affected by the precipitation of cements in adjacent pore spaces we analysed the primary coral aragonite in cemented and uncemented areas of the skeleton sr ca b ca and u ca of primary coral aragonite is not affected by the presence of cements in adjacent interskeletal pore spaces i e the coral structures maintain their original composition and selective sims analysis of these structures offers a route to the reconstruction of accurate ssts from altered coral skeletons however mg ca and ba ca of primary coral aragonite are significantly higher in parts of skeletons infilled with high mg calcite cement we hypothesise this reflects cement infilling of intraskeletal pore spaces in the primary coral structure

the age and hydrological history of blue lake south australia abstract three sediment cores from the blue lake a groundwater fed lake of volcanic origin in south australia have been investigated using a range of chemical and isotopic parameters the 14c activity of both the inorganic and organic carbon fractions of the sediment decreases monotonically with depth the rate of change with depth is greater for near surface samples with an apparent hiatus in sedimentation rate at about 7000 yr b p estimates of age for the precipitated authigenic carbonate after correction for dilution with dead carbon from the groundwater agree well with calculated ages from the organic carbon fraction of the sediment we suggest the lake is much older than previously proposed using other dating techniques variations in the 13c and 18o composition of the authigenic carbonate reflect different residence times of dissolved inorganic carbon and water in the lake caused by changes in the lake level during periods of hydrologic steady state it is suggested that relative changes in the temperature of the lake can be seen in 18o changes in authigenic carbonate blue lake has been undergoing sedimentation for at least 28 000 years including two lengthy periods of hydrologic steady state the lake for a large proportion of its existence was much shallower while for the last 7000 years has maintained a level close to the present one the influence of pumping from the lake for urban water supply during this century is reflected in the isotopic composition of carbonate in the sediment

reproducibility of geochemical and climatic signals in the atlantic coral montastraea faveolata 1 monthly resolved 41 year long stable isotopic and elemental ratio time series were generated from two separate heads of montastraea faveolata from looe key florida to assess the fidelity of using geochemical variations in montastraea the dominant reef building coral of the atlantic to reconstruct sea surface environmental conditions at this site the stable isotope time series of the two corals replicate well mean values of 18o and 13c are indistinguishable between cores compare 0 70 versus 0 68 for 13c and 3 90 versus 3 94 for 18o mean values from the sr ca time series differ by 0 037 mmol mol which is outside of analytical error and indicates that nonenvironmental factors are influencing the coral sr ca records at looe key we have generated significant 18o sea surface temperature sst r 0 84 and sr ca sst r 0 86 calibration equations at looe key however these equations are different from previously published equations for montastraea variations in growth parameters or kinetic effects are not sufficient to explain either the observed differences in the mean offset between sr ca time series or the disagreement between previous calibrations and our calculated 18o sst and sr ca sst relationships calibration differences are most likely due to variations in seawater chemistry in the continentally influenced waters at looe key additional geochemical replication studies of montastraea are needed and should include multiple coral heads from open ocean localities complemented whenever possible by seawater chemistry determinations

coral windows onto seasonal climate variability in the northern caribbean since 1479 mean surface ocean conditions in the caribbean were up to 2 c cooler than today at times during the little ice age the seasonal context for such mean state changes is important for determining the mechanisms involved we reconstructed surface ocean conditions in southwest puerto rico at approximately monthly resolution over eight 4 12 year periods during the last 520 years to test if the seasonal cycles of temperature or salinity varied with mean state we carried out paired analyses of sr ca and 18o for two coral cores the 18o data contained clear annual cycles and were significantly correlated to temperature during the 20th century calibration periods 1993 2004 and 1902 1912 r 0 73 the sr ca data contained high frequency noise that obscured the seasonal cycles although the centennial variability matched that of the coral 18o indicating a common forcing that is likely temperature the seasonal coral 18o amplitude averaged 0 60 0 17 with none of the periods significantly different from the most recent the simplest explanation is that the amplitudes of seasonal seawater 18o and temperature variations were not different from today previous work in the southern caribbean indicates that the intertropical convergence zone was shifted southward or weaker during the little ice age and we speculate about how this could occur with no apparent affect on seasonality in the northern caribbean

high temporal resolution mg ca and ba ca records in modern porites lobata corals 1 secondary ion mass spectrometry sims was used to determine mg ca and ba ca variations across two skeletal structures the fasciculi and the centers of calcification cocs in two porites lobata corals of different linear extension rates from oahu hawaii both corals exhibit large mg and ba heterogeneity which is not related to sea surface temperature sst or composition higher concentrations of ba occur in the fasciculi and higher mg in the cocs of the slowly extending coral compared to the fast growing coral mg and ba concentrations are significantly higher in the cocs of both corals compared to the fasciculi trace element variations may reflect changes in the calcifying fluid composition or changes in skeletal trace element incorporation regressions between mg ba and sr reported in a prior publication indicate that the skeletal incorporation of each element is affected by a different factor or combination of factors smoothed sims records of ba ca variations across the fasciculi of the fast growing coral follow the seasonal trend predicted from sst and expected seawater chemistry variations smoothed sims mg ca records do not correlate with sst indicating that sims mg ca records cannot be used to estimate past ssts

a deep eastern equatorial pacific thermocline during the early pliocene warm period abstract during the early pliocene warm period 4 6 4 2 ma in the eastern equatorial pacific upwelling region sea surface temperatures were warm in comparison to modern conditions warm upwelling regions have global effects on the heat budget and atmospheric circulation and are argued to have contributed to pliocene warmth though warm upwelling regions could be explained by weak winds and or a deep thermocline the temporal and spatial evolution of the equatorial thermocline is poorly understood here we reconstruct temporal and spatial changes in subsurface temperature to monitor thermocline depth and show the thermocline was deeper during the early pliocene warm period than it is today we measured subsurface temperature records from eastern equatorial pacific odp transect sites 848 849 and 853 using mg ca records from globorotalia tumida which has a depth habitat of 50 100 m in the early pliocene subsurface temperatures were 4 5 c warmer than modern temperatures indicating the thermocline was relatively deep subsurface temperatures steeply cooled 2 3 c from 4 8 to 4 0 ma and continued to cool an additional 2 3 c from 4 0 ma to present compared to records from other regions the data suggests the pronounced subsurface cooling between 4 8 and 4 0 ma was a regional signal related to restriction of the isthmus of panama while continued cooling from 4 0 ma to present was likely related to global processes that changed global thermocline structure additionally the spatial evolution of the equatorial thermocline along a n s transect across odp sites 853 849 and 848 suggests an intensification of the southeast trades from the pliocene to present large scale atmospheric and oceanographic circulation processes link high and low latitude climate through their influence on equatorial thermocline source water regions and consequently the equatorial thermocline through these low latitude high latitude linkages changes in the equatorial thermocline and thermocline source water played an important role in the transition from the warm pliocene to the cold pleistocene

reduced el nino southern oscillation during the last glacial maximum el nino southern oscillation enso is a major source of global interannual variability but its response to climate change is uncertain paleoclimate records from the last glacial maximum lgm provide insight into enso behavior when global boundary conditions ice sheet extent atmospheric partial pressure of co2 were different from those today in this work we reconstruct lgm temperature variability at equatorial pacific sites using measurements of individual planktonic foraminifera shells a deep equatorial thermocline altered the dynamics in the eastern equatorial cold tongue resulting in reduced enso variability during the lgm compared to the late holocene these results suggest that enso was not tied directly to the east west temperature gradient as previously suggested rather the thermocline of the eastern equatorial pacific played a decisive role in the enso response to lgm climate

orbital control of low latitude seasonality during the eemian 1 we used sr ca and stable isotope data from well dated and preserved corals from the northeastern caribbean to determine the seasonal environmental conditions for four continuous years during the eemian the last time the earth was in a prolonged warm phase we determined that the seasonal range in sst during the eemian was 25 30 c this is 1 2 larger than at present and caused primarily by winter cooling and only to a small degree by summer warming as climate modeling studies indicate the bias towards colder winters can be explained by changes in low latitude insolation induced by altered orbital parameters modulated by atmospheric co2 levels that were lower than today milankovitch forcing at higher latitudes was probably less important

a transient rise in tropical sea surface temperature during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been attributed to a rapid rise in greenhouse gas levels if so warming should have occurred at all latitudes although amplified toward the poles existing records reveal an increase in high latitude sea surface temperatures ssts 8 to 10 c and in bottom water temperatures 4 to 5 c to date however the character of the tropical sst response during this event remains unconstrained here we address this deficiency by using paired oxygen isotope and minor element magnesium calcium ratios of planktonic foraminifera from a tropical pacific core to estimate changes in sst using mixed layer foraminifera we found that the combined proxies imply a 4 to 5 c rise in pacific sst during the petm these results would necessitate a rise in atmospheric pco 2 to levels three to four times as high as those estimated for the late paleocene

a high resolution calibration of sr ca thermometry using the caribbean coral montastraea annularis 1 a relationship has been established between the sr ca ratio in the skeleton of the scleractinian coral montastraea annularis and sea surface water temperature in south florida in order to obtain this correlation specimens of montastraea annularis were transplanted to a site at a local reef where every two to three months throughout a 2 year period the corals were stained with alizarin red s and where water temperature which annually ranges between 20 and 30 c was continually monitored at the end of the experimental period the coral skeleton was sampled at a rate of 50 samples per year each sample corresponding to only around 20 g of calcium carbonate for the 2 5 year period the sr ca ratio exhibited excellent correlation in the first year r2 0 83 sr ca mmol mol 10 11 0 0452 sst c but a rather poorer correlation in the second year r2 0 68 sr ca mmol mol 10 09 0 0406 sst c averaging the data into monthly values for year 1 we determined a relationship of sr ca mmol mol 10 165 0 0471 sst c on the basis of the excellent correlation between temperature and sr ca we feel that this relationship is the most accurate discrepancies in the second year are suggested to arise from slight sampling errors relative to the stain lines

diagenesis in live corals from the gulf of aqaba i the effect on paleo oceanography tracers abstract the effect of early diagenesis on trace element abundance in coral skeleton was studied in live coral heads porites from the nature reserve reef nrr elat gulf of aqaba northern red sea petrography of the corals shows diagenetic features of dissolution recrystallization and secondary aragonite precipitation pore filling which are most extensive in the oldest part of the coral coral porewaters were extracted with a special setup and were analyzed for chemical composition the total alkalinity and sr deficit in pore water as compared to reef water is consistent with both precipitation of secondary aragonite and recrystallization of primary skeleton the present rate constant of pore filling by secondary aragonite was estimated by a water replacement experiment to be 0 0015 y 1 which equals to pore filling rate of 1 5 0 3 kg aragonite per year the corals show clear seasonal fluctuations in sr ca ratios that are interpreted as reflecting changes in sea surface temperature sst yet the secondary aragonite is characterized by a significantly higher sr ca ratio than the average ratio in primary aragonite thus measuring a mixed sample of pristine and secondary aragonite may produce erroneous about 2 c lower sst estimates by the sr ca thermometers it appears that the sr ca ratio a major proxy for paleo environmental marine studies is sensitive to subtle pore filling and replacement of the original coral matrix by secondary aragonite in the marine environment

diagenesis in pleistocene 80 to 500 ka corals from the ironshore formation implications for paleoclimate reconstruction abstract fossil corals provide a unique opportunity for paleoclimate research because they can be dated and they incorporate climate controlled seawater proxies into their aragonitic skeletons during growth coral skeletons however can only produce reliable environmental information if they have not been diagenetically altered an issue that becomes increasingly probable as the age of the corals increase although commonly used analytical techniques such as thin section scanning electron microscopy and x ray diffraction can highlight obvious mineralogical changes subtle changes in the trace element and isotopic composition of the skeletons may not be evident this premise is assessed by examining orbicella annularis and montastrea cavernosa corals from the pleistocene ironshore formation units a f on grand cayman 80 500 ka to determine the diagenetic effects on both physical and chemical properties of corals in the ironshore formation the corals in units a and c were altered in a semi open diagenetic system by seawater diluted by meteoric water which resulted in chemical diagenesis that changed the elemental and isotopic composition of the corals even though their aragonitic skeletons show no obvious signs of change in contrast the limestones in unit b have been pervasively recrystallized in an open diagenetic system by meteoric waters that caused both chemical and physical changes the corals in units d to f however underwent minimal diagenesis and show no evidence of alteration for altered corals from the ironshore formation elevated mg ca and low sr ca ratios provide evidence of subtle chemical diagenetic changes even in corals that have retained their primary aragonitic skeleton thus corals that are formed of 95 wt aragonite show no evidence of cementation and have mg ca ratios 8 0 mmol mol 1 18o values 5 7 and 13c values 3 0 are ideal candidates for paleoclimate reconstruction adoption of these criteria shows that the corals from units d to f can be used to calculate sea surface temperatures sst whereas those from units a to c cannot be used for this purpose the calculated sst and the corresponding temperature profiles derived from the corals in units d to f are consistent with global sst reconstructions during the pleistocene unit d corals record an overall increase in sst which is consistent with elevated temperatures associated with marine isotope stage mis 5e whereas units e and f record overall cooling which is consistent with the end of the peak interglacials of mis 5c and 5a respectively

interpreting sea surface temperature from strontium calcium ratios in montastrea corals link with growth rate and implications for proxy reconstructions 1 we analyzed strontium calcium ratios sr ca in four colonies of the atlantic coral genus montastrea with growth rates ranging from 2 3 to 12 6 mm a 1 derived sr ca sea surface temperature sst calibrations exhibit significant differences among the four colonies that cannot be explained by variations in sst or seawater sr ca for a single coral sr ca ratio of 8 8 mmol mol 1 the four calibrations predict ssts ranging from 24 0 to 30 9 c we find that differences in the sr ca sst relationships are correlated systematically with the average annual extension rate ext of each colony such that sr ca mmol mol 1 11 82 0 13 0 058 0 004 ext mm a 1 0 092 0 005 sst c this observation is consistent with previous reports of a link between coral sr ca and growth rate verification of our growth dependent sr ca sst calibration using a coral excluded from the calibration reconstructs the mean and seasonal amplitude of the actual recorded sst to within 0 3 c applying a traditional nongrowth dependent sr ca sst calibration derived from a modern montastrea to the sr ca ratios of a conspecific coral that grew during the early little ice age lia 400 years b p suggests that caribbean ssts were 5 c cooler than today conversely application of our growth dependent sr ca sst calibration to sr ca ratios derived from the lia coral indicates that ssts during the 5 year period analyzed were within error 1 4 c of modern values

highstands during marine isotope stage 5 evidence from the ironshore formation of grand cayman british west indies abstract the ironshore formation on grand cayman is formed of six unconformity bounded packages units a f units a b c and d known from the subsurface in the northeastern part of grand cayman formed during marine isotope stages mis 11 9 7 and 5e respectively unconformities at the tops of units a b and c are highlighted by terra rossa and or calcrete layers strata in core obtained from wells drilled in george town harbour and exposed on the west part of grand cayman belong to unit d and the newly defined units e and f corals from unit e yielded th u ages of 104 ka whereas conch shells from unit f gave ages of 84 ka unit e equates to mis 5c whereas unit f developed during mis 5a th u dating of corals and conchs from the ironshore formation on the western part of grand cayman shows that unit d formed during the mis 5e highstand whereas units e and f developed in association with highstands at 95 110 ka mis 5c and 73 87 ka mis 5a unit e 5 m thick in the offshore cores is poorly represented in onshore exposures unit f which unconformably overlies unit d at most localities is formed largely of fossil poor cross bedded ooid grainstones the unconformity at the top of unit d a marine erosional surface with up to 2 5 m relief is not characterized by terra rossa or calcrete in the offshore cores or onshore exposures unit d formed with a highstand of 6 m asl whereas units e and f developed when sea level was 2 to 5 asl and 3 to 6 m asl respectively thus the highstands associated with mis 5e 5c and 5a were at similar elevations

manganese carbonate overgrowths on foraminifera tests below the zone where manganese is remobilized as mn2 aq reductively cleaned foraminifera in deep sea sediments have much higher mnca than those in core tops and sediment traps mnca ranges from less than 20 10 6 in and above the mno2 maximum to as high as 700 10 6 in reducing panama basin sediments the most plausible explanation for this enrichment is that the tests are coated with mn carbonate overgrowths these coatings can account for a significant proportion of the mn in reduced deep sea sediments uptake of manganous ion by carbonate may explain the absence of mn nodules in areas of high carbonate accumulation extreme degrees of overgrowth can alter foram trace element values but this artifact can be avoided by avoiding foraminifera with high mn ca

kinetic and mineralogic controls on the evolution of groundwater chemistry and 87sr 86sr in a sandy silicate aquifer northern wisconsin usa abstract substantial flowpath related variability of 87sr 86sr is observed in groundwaters collected from the trout lake watershed of northern wisconsin in the extensive shallow aquifer composed of sandy glacial outwash groundwater is recharged either by seepage from lakes or by precipitation that infiltrates the inter lake uplands 87sr 86sr of groundwater derived mainly as seepage from a precipitation dominated lake near the head of the watershed decreases with progressive water chemical evolution along its flowpath due primarily to enhanced dissolution of relatively unradiogenic plagioclase in contrast 87sr 86sr of groundwater derived mainly from precipitation that infiltrates upland areas is substantially greater than that of precipitation collected from the watershed due to suppression of plagioclase dissolution together with preferential leaching of sr from radiogenic phases such as k feldspar and biotite the results of a column experiment that simulated the effects of changing residence time of water in the aquifer sand indicate that mobile waters obtain relatively unradiogenic sr whereas stagnant waters obtain relatively radiogenic sr nearly the entire range of strontium isotope composition observed in groundwaters from the watershed was measured in the experimental product waters the constant mobility of water along groundwater recharge flowpaths emanating from the lakes promotes the dissolution of relatively unradiogenic plagioclase perhaps due to effective dispersal of clay mineral nuclei resulting from dissolution reactions in contrast episodic stagnation in the unsaturated zone along the upland recharge flowpaths suppresses plagioclase dissolution perhaps due to accumulation of clay mineral nuclei on its reactive surfaces differences in redox conditions along these contrasting flowpaths probably enhance the observed differences in strontium isotope behavior this study demonstrates that factors other than the calculated state of mineral saturation must be considered when attempting to simulate chemical evolution along flowpaths and that reaction models must be able to incorporate changing contributions from reacting minerals in the calculations

environmental isotope study on hydrodynamics of lake naini uttar pradesh india environmental isotopes 18o d and 3h were used to understand the hydrodynamics of lake naini in the state of uttar pradesh india the data was correlated with the in situ physico chemical parameters namely temperature electrical conductivity and dissolved oxygen the analysis of the data shows that lake naini is a warm monomictic lake i e in a year the lake is stratified during the summer months march april to october november and well mixed during the remaining months the presence of a centrally submerged ridge inhibits the mixing of deeper waters of the lake s two sub basins and they exhibit differential behaviour the rates of change of isotopic composition of hypolimnion and epilimnion waters of the lake indicate that the water retention time of the lake is very short and the two have independent inflow components a few groundwater inflow points to the lake are inferred along the existing fractures fault planes and dykes in addition to poor vertical mixing of the lake due to the temperature induced seasonal stratification the lake also shows poor horizontal mixing at certain locations of the lake the lake groundwater system appears to be a flow through type also a tritium and water balance model was developed to estimate the water retention time of well mixed and hydrologically steady state lakes the model assumes a piston flow of groundwater contributing to the lake the developed model was verified for a finger lakes new york b lake neusiedlersee austria and c blue lake australia based on literature data the predicted water retention times of the lakes were close to those reported or calculated from the hydrological parameters given in the references on application of this model to lake naini a water retention time of 2 years and age of groundwater contributing to the lake 14 years is obtained copyright 2001 john wiley sons ltd

application of a radially viewed inductively coupled plasma optical emission spectrophotometer to simultaneous measurement of mg ca sr ca and mn ca ratios in marine biogenic carbonates 1 we developed and applied an analytical system for the simultaneous determination of magnesium calcium strontium calcium and manganese calcium ratios in biogenic carbonates using a perkin elmer 4300 optima dv inductively coupled plasma optical emission spectrophotometer in radial mode intensity ratio responses to calibration standard elemental ratios were linear over suitable working ranges we evaluated instrumental response using solution replicates and we analyzed planktonic foraminifera in multiple runs ca concentrations were kept in a relatively narrow range typically 0 6 2 4 mm ca although we found no resolvable ca matrix effect over a much wider range each analysis required a minimum sample volume of 300 l and took 3 5 min instrument time an analytical run of 30 samples plus standards blanks and control materials typically took 5 6 hours reproducibility interrun precision 1s rsd for solutions was 1 2 1 5 and 1 2 for mg ca sr ca and mn ca ratios far smaller than reproducibility for foraminiferal replicates over multiple analytical runs there was no independent reference material for assessing accuracy detection limits were equivalent for an 0 5 mm ca solution to 0 058 mmol mol for mg ca 0 015 mmol mol for sr ca and 0 005 0 020 mmol mol for mn ca precautions included limiting length of time the peristaltic tubing for the autosampler was used avoiding mg contamination from plastic ware and screening out results from samples with very low ca concentrations 0 25 mm ca

temperature control on the incorporation of magnesium strontium fluorine and cadmium into benthic foraminiferal shells from little bahama bank prospects for thermocline paleoceanography surface sediments from little bahama bank lbb intersecting the subtropical thermocline were used to assess the influence of temperature on the incorporation of mg sr f and cd into shells of benthic foraminifera samples were obtained from twelve cores along the southern slope of lbb covering a temperature range of 18 4 5 c between 301 and 1585 m we studied the composition of ten calcitic and one aragonitic species which are often used in paleochemical reconstructions mg ca ratios decrease with increasing water depth in all benthic species both with calcitic and aragonitic mineralogy showing a strong correlation with water temperature similar decrease is seen in sr ca but with no correlation with temperature none of the benthic species studied here exhibits a depth or temperature related change in f ca similar trends are observed when using an ocean wide dataset which includes shallow and deep core tops 300 5000 m we suggest that temperature is the primary control on the mg content of benthic foraminifera based on inorganic precipitation experiments and thermodynamic considerations presented here a 30 40 decrease in the mg distribution coefficient in calcite may be expected as a result of a temperature change from 25 c to 5 c which is about half the observed change in lbb a calibration curve applied to c pachyderma data from core tops along the slope of little bahama bank suggests that water temperature may be inferred from mg ca ratios with an uncertainty of about 0 8 c therefore the mg content of benthic foraminifera may provide a new independent temperature proxy for studying shallow waters paleoceanography the linear decrease in sr ca with increasing depth is not correlated with temperature the trend is constant from the ocean surface down to 5 km suggesting that pressure related effects on the calcification process are a more likely explanation than post depositional dissolution mg ca ratios in aragonitic shells of h elegans covary with temperature in accord with recent observations from corals in contrast the sr and f chemistry of h elegans is very different than that of corals and inorganically precipitated aragonites the disparities between the elemental composition of biogenic and inorganic phases and the large intergeneric and interspecific differences observed both in planktonic and benthic foraminifera implicate temperature related physiological processes in regulating the coprecipitation of elements in foraminiferal shells our work demonstrates that cd ca ratios of shallow calcitic species reflect the vertical distribution of nutrients no significant influence of temperature on the partitioning of cd into the shells was found our data extend the previous deep water calibration boyle 1992 thereby allowing for the reconstruction of the nutrient chemistry of shallow thermocline waters

200 k y paleoclimate record from death valley salt core a 186 m long core dv93 1 from death valley california composed of interbedded salts and muds contains a 200 k y record of closed basin environments and paleoclimates interpreted on the basis of sedimentology ostracodes homogenization temperatures of fluid inclusions in halite and correlation with shoreline tufa the 200 k y paleoclimate record is dominated by two dry and or warm and wet and cold cycles that occurred on a 100 k y time scale these cycles begin with mud flat deposits 192 ka to bottom of core and 60 ka to 120 ka wetter and or colder conditions produced greater effective moisture saline pan and shallow saline lake evaporites overlie mud flat sediments 186 ka to 192 ka and 35 ka to 60 ka eventually enough water entered death valley to sustain perennial lakes that had fluctuating water levels and salinities 120 ka to 186 ka and 10 ka to 35 ka when more arid conditions returned mud flat deposits accumulated on top of the perennial lake sediments completing the cycle 120 ka and 10 ka of particular significance are the major lacustrine phases 10 ka to 35 ka and 120 ka to 186 ka oxygen isotope stages 2 and 5e 6 which represent markedly colder and wetter conditions than those of modern death valley of the two major lake periods the penultimate glacial lakes were deeper and far longer lasting than those of the last glacial

a cenozoic seawater sr ca record from benthic foraminiferal calcite and its application in determining global weathering fluxes a cenozoic multi species record of benthic foraminiferal calcite sr ca has been produced and is corrected for inter specific offsets typically less than 0 3 mmol mol and for the linear relationship between decreasing benthic foraminiferal sr ca and increasing water depth the water depth correction determined from holocene late glacial maximum and eocene paleowater depth transects is not vert similar0 1 mmol mol km the corrected cenozoic benthic foraminiferal sr ca record ranges from 1 2 to 2 0 mmol mol and has been interpreted in terms of long term changes in seawater sr ca enabling issues related to higher resolution variability in sr ca to be ignored we estimate that seawater sr ca was not vert similar1 5 times modern values in the late cretaceous but declined rapidly into the paleogene following a minimum in the eocene seawater sr ca increased gradually through to the present day with a minimum superimposed on this trend centered in the late miocene by assuming scenarios for changing seawater calcium concentration and using published carbonate accumulation rate data combined with suitable values for sr partition coefficients into carbonates the seawater sr ca record is used to estimate global average river sr fluxes these fluxes are used in conjunction with the seawater strontium isotope curve and estimates of hydrothermal activity tectonic outgassing to calculate changes in global average river 87sr 86sr through the cenozoic the absolute magnitude of sr fluxes and isotopic compositions calculated in this way are subject to relatively large uncertainties nevertheless our results suggest that river sr flux increased from 35 ma to the present day roughly two fold accompanied by an overall increase in 87sr 86sr by not vert similar0 to 0 001 between 75 and 35 ma river 87sr 86sr also increased by not vert similar0 001 to 0 002 but was accompanied by a decrease two to three fold in river sr flux

6000 years of environmental changes recorded in blue lake south australia based on ostracod ecology and valve chemistry abstract a 4 m long core taken from the freshwater blue lake crater near the township of mount gambier in southeastern south australia provided a high resolution palaeoclimatic record for the last six millennia accelerator mass spectrometry ams radiocarbon 14 c dates were obtained from organic plant fibres and biogenic carbonates from the laminated sequence of the core and from a modern water sample large discrepancies between the radiocarbon ages determined from plant fibres and biogenic carbonates indicate the presence of a time variable lacustrine reservoir which is consistent with what is known of the lake s hydrology ostracod assemblages associated with stable isotope 13 c 18 o analyses and in combination with mg ca sr ca and na ca analyses done on ostracod valves infer salinity temperature and water level changes in blue lake over the last 6 millenia the influence of local aquifers through time has also been determined from the na ca of ostracod valves approximately 900 year cycles are evident in the 13 c record from 5 4 ka to 1 8 ka the history of blue lake records an initial period of high hydrological variability around 6 ka becoming increasingly deeper as groundwater flowed into the basin by 4 ka the lake had reached steady state with the lake level fluctuating by as much as 9 m although significant geochemical variations represent temperature fluctuations until european settlement near the lake in 1839

comparison of foraminiferal cleaning procedures for mg ca paleothermometry on core material deposited under varying terrigenous input and bottom water conditions a down core comparison of two commonly applied foraminiferal cleaning procedures for mg ca paleothermometry has been conducted using well preserved globigerinoides ruber white 250 300 mm from core material deposited under varying terrigenous input and bottom water conditions this study demonstrates that in the majority of investigated core materials both cleaning methods yield fairly comparable results of mg ca ratios however fe and mn phases are effectively removed by the cleaning procedure containing a reductive step in a core interval indicating gradual transition of terrigenous deposition and pore water conditions the cleaning procedure without a reductive step results in anomalously higher mg ca ratios accompanied by high fe ca and mn ca ratios indicating the presence of high mg contaminants considering that the mg ca deviation of the comparison study is the cumulative sum of 1 the difference in cleaning efficiency of the applied methods 2 the cleaning method dependent partial dissolution of mg and 3 the heterogeneity of subsamples we suggest that selective mg loss from well preserved globigerinoides ruber shells caused by the reductive sample treatment is not substantial enough to significantly bias paleotemperature estimation thus for core material deposited under varying sources and amounts of terrigenous material and bottom water conditions favorable for formation of authigenic mineral phases the use of cleaning methods that do include a reductive step yields more effective cleaning results by successful removal of mineral phases that may contain high mg

foraminiferal magnesium in globeriginoides sacculifer as a paleotemperature proxy foraminiferal magnesium shows increasing promise as a paleothermometer but the accuracy and precision are limited by biases introduced by partial dissolution salinity variations mg rich gametogenic calcite and contaminant phases we improved cleaning methods and reduced errors introduced by partial dissolution by sampling from well preserved cores in the equatorial atlantic and the caribbean sea with different dissolution histories all cores reveal a synchronous 25 increase in mg ca from the stage 2 3 boundary to the holocene core top indicating that dissolution is not a controlling factor modern temperatures estimated from core top mg ca are 24 5 25 0 c equal to mean annual water temperatures at 50 100 m we estimate that sea surface temperature increased by 2 6 c 1 3 from the last glacial maximum to the holocene holocene values were comparable to those during isotope stage 5e our data indicate that biases from contaminant phases and partial dissolution can be reduced this paleothermometer holds promise if uncertainties introduced by salinity variations and gametogenic calcite can be constrained

geochemical isotopic and hydrological mass balance approaches to constrain the lake water groundwater interaction in dal lake kashmir valley it is important to have qualitative as well as quantitative understanding of the hydraulic exchange between lake and groundwater for effective water resource management dal a famous urban fresh water lake plays a fundamental role in social cultural and economic dynamics of the kashmir valley in this paper geochemical isotopic and hydrological mass balance approaches are used to constrain the lake water groundwater interaction of dal lake and to identify the sources of lake water water samples of precipitation n 27 lake water n 18 and groundwater n 32 were collected across the lake and its catchment for the analysis of 18o and 2h a total of 444 lake water samples and 440 groundwater samples springs tube wells and dug wells were collected for the analysis of ca2 mg2 hco3 so4 2 cl no3 na and k water table and lake water level were monitored at 40 observation locations in the catchment water table map including ph and ec values corroborate and verify the gaining nature of the dal lake stable isotopes of lake water in boddal and gagribal basins showed more deviation from the global meteoric water line than hazratbal and nigeen basins indicating the evaporation of lake water the isotopic and geochemical mass balance suggested that groundwater contributes a significant proportion 23 40 to dal lake the estimated average groundwater contribution to dal lake ranged from 31 2 103 to 674 103 m3 day 1 with an average of 276 103 m3 day 1 the study will be useful to delineate the possible sources of nutrients and pollutants entering the lake and for the management of lake water resources for sustainable development

climate variability and land ocean interactions in the indo pacific warm pool a 460 ka palynological and organic geochemical record from the timor sea climatic conditions in the western timor sea and the adjacent northwestern part of australia are reconstructed for the last 460 ka based oil geochemical and palynological proxy records of paleoproductivity and land vegetation precipitation from images core md01 2378 reduced precipitation and elevated productivity characterize glacial stages whereas enhanced precipitation and reduced productivity are typical of interglacial stages a long term reduction in precipitation over the last 320 ka occurred in two steps at approximately 300 ka and 180 ka bp that are clearly recognizable in the pollen record variations in paleoproductivity and paleoclimate in the timor sea and adjacent landmasses appear to be driven by similar mechanisms that are related to the precession control led australian monsoon system c 2005 elsevier b v all rights reserved

diagenesis of fossil coral skeletons correlation between trace elements textures and 234 u 238 u a comparative study of pleistocene fossil coral skeletons and of modern coral skeletons was carried out using petrographie and trace element analyses on a suite of pleistocene samples that had previously been studied for 234 u 230 th and u 230 th ages chen et al 1991 evidence of a range of diagenetic changes can be recognized by optical om and scanning electron microscopy sem the normal texture exhibited by modern corals under om consists of fine needles of aragonite forming a radial fibrous pattern around a central dark line center of calcification this pattern can also be seen in many fossil corals in most cases the central dark line partially disappears during diagenesis the radialfibrous pattern is obscured and there is a distinct coarsening of the radial fabric of aragonite to unoriented platy or equant aragonite crystals sem images show diagenetic textures ranging from dense structureless images of the coralline matrix with sharp boundaries at the septa walls to the development of 1 a patchy distribution of dissolution micropores partially filled with aragonite fibers in the matrix 2 aragonite needles coming from selvages in the septa walls which radiate into the septa voids using an electron microprobe and sem concentrations of na s sr and mg were measured no other trace elements were detected na s and mg contents of the matrix the fibrous micropores and radiating needles are highly variable and well correlated high concentrations of na s and mg were found in modern living corals with lower concentrations in fossil corals and fibrous micropores and the lowest value in the radiating needles the reason for the correlations of na s and mg and crystal chemistry and the response to diagenesis of these trace elements is not understood the average concentrations of na s and mg for each sample when plotted against the whole coral initial 234 u are generally correlated chen et al 1991 as all these diagenetic changes involve the recrystallization and deposition of aragonite we infer that the geologic site of diagenesis both for forming the secondary aragonitic phases and for the enhancement of the 234 u content in the fossil corals was the marine environment it is possible that the textural and na s and mg trace element contents of fossil corals be used to ascertain the reliability of fossil coral skeletons for u 230 th dating the basic problem of identifying a priori unaltered coral skeletons for 230 th dating is not yet resolved