PP23B-1402 1340h
Interplay of Iceberg Rafting and Contourite Deposition Over the Last 210 kyr on Snorri Drift, SW Iceland Slope
Denmark Strait located between Iceland and Greenland is a critical study area because slope sedimentation is a result of oceanographic conditions, climate, and ice dynamics. The interaction of these elements through glacial/interglacial cycles determines the nature of the marine sedimentation. This study aims to unravel the oceanographic, climatic, and sedimentary history of the Southwestern Iceland Slope over the last 200 kyr derived from an 18-meter marine core from Snorri Drift. The depositional processes that contribute to the formation of Snorri Drift such as iceberg rafting (IRD) and bottom current (BC) activity reflect ice sheet movement and deep- water convection. Stadials 2, 4 and 6 were times of dominant iceberg rafting. The stable oxygen isotope data suggest that Stage 2 and 6 were relatively cold stadials compared to St. 4. Although St. 2 and 6 were equally cold stadials, the IRD record suggests different glaciological responses to the climate conditions. The sediments of St. 6 have less IRD than those of the St. 2. Although there are at least three major IRD pulses during St. 6, the low background levels indicate that the there was a sea ice cover which prevented iceberg deposition. About 90 kyr ago there was a distinct change in how the Greenland Ice Sheet produced icebergs in response to insolation changes. Prior to then iceberg production was cyclical with pulses occurring 2-6 kyr after insolation maximums, which suggests that the GIS required time to equilibrate and produce icebergs. Since then, the GIS's response to changes in insolation seems independent of insolation trends. During the interstadials deposition by bottom currents appears to be more active on Snorri Drift. During the Holocene, the warmer intervals of stage 3 and 6, and 5e sedimentation was significantly affected by the strong northward flowing Atlantic deep water. These sediments are well sorted with a strong silt mode indicative of current deposition. Current speed proxies suggest that BC's accelerated during deglaciations and increased during warm periods, including the Holocene when some of the strongest flow is recorded. This increase in BC activity suggests that North Atlantic Deep Water convection was more active during the interglacials than during the glacials, during which time iceberg rafting was the more dominant depositional process.
PP23B-1403 1340h
A High-Resolution Study to Reconstruct Paleoclimate and Paleoceanography in Isafjardardjup, NW Iceland
Our goal is to study paleoclimatic and -oceanographic changes in Isafjardardjup, a fjord in NW Iceland. We have chosen three sites along a head to mouth transect in this fjord for a high-resolution analysis. Each site gives us an approximate 10,000-year record. The three sites are B997-339, B997-341, MD99-2266. To reconstruct paleoclimate and -oceanography, we are using three proxies: faunal assemblages, isotopes, and sediments. We are analyzing faunal assemblages, where a representative sample of about 200 benthic foraminifera per 10-cm interval is identified (1000-11,000 cal yr BP). We also are analyzing the sedimentological record. The calcareous tests of foraminifera are being used to obtain stable isotopic data. We are taking advantage of site B997-339 at the mouth of Skotufjordur (a tributary fjord located near the head of Isafjardardjup). In the upper 200 cm of this core, Cibicides lobatulus, Cassidulina reniforme, and Nonion labradoricum occur in sufficient amounts and are well-preserved, suitable for isotopic analysis. Because of vital effects, the isotopic results vary from species to species. We analyze these differences and will apply our findings to the other sites. At the other sites, we find only one or the other species well-preserved, present throughout the entire core, and in sufficient numbers for isotopic analysis. Foraminifera, which make up $ > $5% of the sample (size fraction 106-1000 micron) have been statistically evaluated at a 100-yr resolution. The results show faunal changes at 100 cm and 300 cm depth. The change at 100 cm is recognizable in sedimentological data. The sand-size fraction of sediments increases in the top 100 cm of the core as the clay-size fraction decreases. Total organic carbon content increases, but the inorganic carbon contents decreases. Sedimentological changes, however, are not detected at the 300 cm level. Here the isotopic del-18O of the foraminifera Cassidulina reniforme shows a change from 3.50 to 3.05%. The del-18O of Cibicides lobatulus, an epifaunal, benthic foraminifera, at sites MD99-2266 (at the mouth of Isafjardardjup) and B997-339 for the interval between 1000-2000 cal yr BP averages 1.8%, indicating that temperature has been the main driver for isotopic results during this time interval.
PP23B-1404 1340h
Last Glacial Maximum Sedimentation, and Bottom-Current Variability on the Western Svalbard Slope and Yermak Plateau, Fram Strait.
Two sites in Fram Strait, between 74˚-80˚N, have been surveyed and sampled using multibeam bathymetry, sub-bottom profiling and gravity and multi-cores. This data provides a record of bottom-current variability (the West Spitsbergen Current) and sedimentation during the last 46ky. The most southerly site, on the western Svalbard margin sampled a small sediment mound in 1226m of water. The mound, interpreted as a sediment drift, is 80m high and 5km in lateral extent developed parallel to the margin and contain at least 100m of acoustically well laminated sediments. A 3.8m gravity core and associated multicore recovered from the crest of the drift contained fine-grained silty grayish-brown and dark greenish gray muds. Visible in x-radiograph, the upper section (above 1.50m) of the core contained centimeter-scale silty lamination, with little ice rafted debris (IRD), whilst the lower sections (below 1.50m) contained abundant IRD and no lamination. These sediments are interpreted as fine-grained laminated silty turbidites and muddy-silty contourites. 14C AMS dating indicates an age range of early Holocene (8,380 yrs BP) to late Pleistocene, including Last Glacial Maximum (LGM) (26,993 yrs BP). The more northerly site, sampled acoustically well-laminated sediments draped on the flank of the Yermak Plateau in water depths of 961m. A 3.5m gravity core and associated multicore recovered fine-grained, faintly laminated, greenish gray muds, with minor amounts of IRD common throughout. These sediments are interpreted as silty glaciogenic contourites. 14C dating reveal an age range of between 8,708 - 46,530yrs BP. Dinoflagellate cyst analyses of both cores, provides both biostratigraphic data and information on the surface water conditions. Three biostratigraphic units sub-divide both the cores: 1. Early Holocene-post LGM interval, dominated by a temperate, North Atlantic flora with high productivity and open water ameliorative conditions. 2. Last Glacial Maximum displaying poor cyst recovery and severe, high polar conditions, although with some short-lived open water conditions, indicative of some climatic amelioration. 3. Pre-LGM indicating severe polar conditions with poor cyst recovery, although again with some short-lived phases of open water and limited productivity. The record of bottom-current variability, indicating the activity of the West Spitsbergen Current during the last 46 ky, has been extracted from both cores by examining the mean sortable silt, deconvolved from the IRD signal. Bottom-current activity was weak throughout the LGM, but becomes highly variable and increases during the post-LGM and into the Holocene, corresponding to the onset of increased thermohaline circulation and deep-water production in Fram Strait during deglaciation.
PP23B-1405 1340h
Tracing the Holocene variations in sea ice/icebergs along the North Iceland shelf
During severe ice years, sea ice and icebergs drift onto the northern Iceland shelf and have a major impact on the climate of Iceland. Historically there are records of change in the concentration of ice that go back to the Settlement of Iceland $\sim$870AD. This is one of two major routes whereby ice might be brought to sites to the west of the British Isles. Two models of the variations in IRD throughout the Holocene have been proposed. In one the records show a series of peaks and troughs superimposed on an overall decrease in IRD toward the present. In the other, based on East Greenland cores, there is limited IRD during the Holocene until 6 cal ka when IRD increases and it increases throughout the Neoglacial. We use a new tracer which is the Quantitative Phase Analysis (QPA) of XRD scans of the combined sand/silt/clay fractions of marine sediments, which are spiked by ZnO or corundum, ground to a powder, and scanned between 5° and 65° two theta. The minimum sample sized is 0.8 g. Quartz is not a naturally occurring mineral on Iceland and we use the weight% of quartz and the quartz/plagioclase weight% ratios as potential tracers of sediment brought to Iceland from sources on East Greenland and around the Arctic Basin. We present 3 data sets: 1) the variations in quartz data from surface samples on the SW to N-central Iceland shelf; 2) downcore variations in Icelandic subglacial and glacial marine sediments; and 3) downcore variations in the mineralogy of Holocene sediments from cores off N Iceland with a particular focus on data from MD99-2269 which spans the last 12 cal ka with a sampling density of around 1 sample every 30-yr. The surface samples show a band of quartz weight% values of 2-6%\ off N Iceland that parallels the observed limits of sea ice in the spring. At sites in the SW, W, and inshore on the northern margins quartz values are < 1%\ in the total sediment. In contrast, "native" Icelandic glacial and glacial marine sediments have negligible quartz content of between 0.0 and $ < $1.0%\. The Holocene occurrence of quartz in MD99-2269 shows low and variable amounts in the early Holocene but values start to increase 5-6 cal ka and continue to rise throughout the Neoglacial period---in this the quartz data parallel to the coarse ($ > $ 2 mm) IRD records from the East Greenland shelf.
PP23B-1406 1340h
A High-Resolution, Holocene Climate Record From the N Iceland Shelf: Benthic and Planktonic Mg/Ca and d18O Records on a Radiocarbon, Tephrochronology and Paleomagnetic Chronostratigraphy
We present a high-resolution Holocene Mg/Ca and d18O record from benthic foraminifera Islandiella norcrossi/helenae and Melonis barleeanus and planktonic foraminifera Neogloboquadrina pachyderma (sin) from the North Iceland shelf core MD99-2269 (Lat: 66.37.53 N, Long: 23.51.16 W, water depth 365 m, length 2530 cm). These allow reconstruction of the upper and bottom water conditions at our site. To place the observed changes on as accurate chronology as possible we have employed a multilevel approach toward deriving our radiocarbon-based chronology. Twenty-five AMS radiocarbon dates were acquired from MD99-2269. To augment these dates, we have through paleomagnetic synchronization transferred an additional 18 AMS radiocarbon dates from East Greenland core MD99-2322 (Lat: 67.08.18 N, Long: 30.49.67 W, water depth 714 m, length 2635 cm) to their equivalent depths in MD99-2269. Forty of the combined 43 AMS radiocarbon dates were pooled together to create a single age model for the two cores. This chronology was then tested for accuracy using the abundance of traceable and dated tephra-markers from Icelandic volcanoes. Core MD99-2269 contains one visible tephra-marker (Saksunarvatn) and an abundance of cryptotephra. Cryptotephra were located by grain counting in the > 150 µm size-fraction. Samples from selected tephra peaks were geochemically analyzed at the Nordic Volcanological Institute in Iceland. The geochemical fingerprint identifies each tephra to a specific eruption, providing eight checks on the accuracy of MD99-2269 age model. Offsets are generally less than 200 yrs and suggest that reservoir-age on the NW-Iceland shelf was time dependent during the Holocene. We incorporate this variable reservoir age in our final age model. The temperature variations observed are interpreted as variations in the strength of Irminger water inflow to the N Iceland shelf. These variations versus time will be discussed.
PP23B-1407 1340h
A ~100 Kyr SST record based on the Mg/Ca of Neogloboquadrina pachyderma (s) from the Labrador Sea.
Core Hu90013-29[58\deg23.61N; 56\deg45.76E] was retrieved at 2918m water depth from the Labrador Rise of the Eastern Canadian continental margin in front of the mouth of the Hudson Strait. We measured the Mg/Ca ratio and $\delta$ $^{18}$ O in the polar species planktonic foraminifera {\it Neogloboquadrina pachyderma} (sinistral) to reconstruct a sea surface temperature (SST) of the past 100kyr. A modified version of the Boyle and Keigwin (1985/6) cleaning method comprising mechanical, oxidative and reductive cleaning was employed to clean the foraminiferal shell fragments. Mg/Ca ratios range from 0.35 to 1.55mmole/mole corresponding to -3 to 11\deg C temperature using the calibration curve of N\"{u}rnberg {\it et al}.(1996) were obtained. Core top Mg/Ca ratio of 1.4mmole/mole corresponds to summer (August) SST of ~10\deg C at the site. The reconstructed SST-curve is not as high resolution as the oxygen isotope curve due to the dearth of foraminifera; however, we observe high frequency SST variability during Marine Isotope Stage 3. Calculated SST has rise from -3 to 8\deg C at the end of Heinrich events except during Heinrich event 2. The cooler temperature values (below the freezing point of seawater) are suspected to be an artifact of the exponential function of the N\"{u}rnberg {\it et al}. (1996) calibration equation, because under very cold conditions {\it N. pachyderma} (s) would live under stress and its calcification temperature may deeper than their normal depth of habitation (Kohfeld {\it et al}.1996). An SST of ~-1\deg C was reconstructed for the Last Glacial Maximum (LGM) suggesting an ice-free condition during the summer (August) as required for the {\it N. pachyderma} (s) bloom. Our results contrast with the suggestion of a permanent sea-ice cover during the LGM by deVernal {\it et al}.(2000) and Levac {\it et al}.(2001). Moreover these authors reported a SST of ~16\deg C compared to this study (~12\deg C) during the early to mid Holocene, which seems too warm for such Northern latitudes.
PP23B-1408 1340h
Pleistocene North Atlantic Deep Water Production; A Southern Hemisphere Perspective
Faunal counts and stable isotopes of planktonic foraminifera are used to identify glacial-interglacial and millennial scale change in Pleistocene Atlantic interhemispheric transport. The sampling site, ODP Site 1085, has a sedimentation rate of approximately 5 cm/k.y. Samples were taken every 2 cm throughout the sections of the core representing the last 200 k.y., giving the site a resolution of approximately 500 years, high enough to observe glacial-interglacial variation, Dansgaard/Oeschger temperature cycles, and Heinrich events, within the Nyquist frequency. {\it Globigerina bulloides}, found in cold, nutrient-rich water, is used as a proxy for upwelling (Girardeau 1992). At Site 1085, {\it G. bulloides} peaks both during glacial and interglacial periods. The interglacial peaks covary with peaks of terrigenous sediment greater than 10 microns, an indicator of aeolian transport (Stuut et al. 2002), indicating a link between upwelling and wind strength at that time. The glacial peaks broadly correlate to a low C/N ratio, indicating a probable marine cause for the upwelling, such as an enhanced Benguela Current. Additionally, there is higher-frequency (sub-Milankovitch) variability through both the glacial and interglacial periods.
PP23B-1409 1340h
Reconstructing Deep Ocean Temperature During the Last Glacial Maximum Based on Kr/N$_{2}$ and Xe/N$_{2}$ Ratios in air Trapped in Glacial ice
Deep ocean temperature is a fundamental parameter of the climate system, but its past variations remain poorly known. This is mainly due to the inherent ambiguity of oxygen isotope records from benthic foraminifera, which are affected by both temperature and ice volume. Sediment pore water studies have provided a single estimate of deep ocean cooling at the last glacial maximum, but do not resolve a time series of temperature. We discuss the development of a new technique to reconstruct average ocean temperature by using noble gas measurements of the past atmosphere from ice cores. This reconstruction should place constraints on the timing and magnitude of deep ocean temperature variations. Using noble gas and nitrogen inventories and solubilities, as well as the Levitus ocean temperature database, a box model of the ocean and atmosphere indicates that atmospheric Kr/N$_{2}$ and Xe/N$_{2}$ concentrations should have been lower during the last glacial maximum (LGM), approximately 20,000 years ago. This is due to the greater temperature dependence of the solubilities of the heavy noble gases relative to nitrogen. Assuming an average ocean cooling of $4\deg$C, we calculate the change in Kr/N$_{2}$ relative to today$'$s atmosphere to be $-$1.69$\permil$. A similar calculation for Xe/N$_{2}$ yields a result of $-$3.93$\permil$. For a comparison between present and glacial conditions, we have measured these ratios in trapped air bubbles in Greenland ice cores from both the late Holocene and the LGM. The $\delta$Kr/N$_{2}$ and $\delta$Xe/N$_{2}$ in the GISP 2 ice core during the late Holocene ($\sim$ 1,500 years ago) are $-$0.07$\permil$ $\pm$ 0.40$\permil$ and $-$0.29$\permil$ $\pm$ 2.27$\permil$, respectively. We also present preliminary measurements of $\delta$Kr/N$_{2}$ and $\delta$Xe/N$_{2}$ from the LGM in the Dye 3 and GISP2 ice cores, as well as in air bubbles in ice from Pakitsoq, Greenland.
PP23B-1410 1340h
Source Apportionment Mixing Models for High Resolution Trace Element Ice Core Records over the Past 350 years at Siple Dome, Antarctica
High Resolution trace element concentration records from polar ice cores are valuable in identifying paleoclimate trends. However, traditional methods of allocating the elemental concentrations between sources often assume that the analytical measurement errors and the elemental ratio uncertainties of each source are negligible. To address the impacts of each of these uncertainties, a Monte Carlo analysis was used to quantify the sensitivity of mixing models to uncertainties in the input variables. Simulations of 100,000 trails were based on an idealized concentration dataset of average concentrations at Siple Dome, Antarctica, with uncertainty applied to the analytical measurements and/or the source elemental ratios. The results indicated that for both two component and three component mixing models, uncertainty in source allocations decreased with increasing number of elements measured; most notably with the inclusion of unique endmember elements for each source (e.g., sodium and manganese are unique endmembers for seasalt and crustal dust sources, respectively). Further, the Monte Carlo analysis allowed for quantification of error bars on annual average source concentration records over time. Using the two component mixing model, we found that Siple Dome is a marine dominated area (89% seasalt, 11% crustal dust by mass) with seasalts varying approximately 65%, and crustal dust concentrations approximately doubling over the last 350 years. Using the three component mixing model, separating sources that are either not well characterized or do not have unique elemental ratios proved to be problematic.
PP23B-1411 1340h
Foraminifera And Coccolithophorid Assemblage Changes In The Panama Basin During The Last Deglaciation: Response To Sea-Surface Productivity Induced By A Transient Climate Change
The response of community assemblages of planktonic and benthonic foraminifera and coccolithophorids to transient climate change are explored for the uppermost 2m of cores ODP677B (1.2°N; 83.74°W, 3461m) and TR163-38 (1.34°S; 81.58°W, 2200m), for the last ~40ka. Results suggest that the deglaciation interval was a time of increased productivity and a major reorganization of planktonic trophic webs. The succession in dominance of planktonic foraminifera species Globorotalia inflata, Globigerina bulloides, and Neogloboquadrina pachyderma denote four periods of oceanographic change: (1) advection (24 to 20ka), (2) strong upwelling (20 to 15ka), (3) weak upwelling (14 to 8ka) and (4) oligotrophy (8ka to Present). Strong upwelling for the deglaciation interval is supported by the low Florisphaera profunda / other coccolithophorids ratio and the high percentage abundance of Gephyrocapsa oceanica. Benthonic foraminifera assemblage changes are different in both cores and suggest significant regional variations in surface productivity and/or oxygen content at the seafloor, and a decoupling between surface productivity and export production to the seafloor. This decoupling is evidenced by the inverse relationship between the percentage abundance of infaunal benthonic foraminifera and the percentage abundance of N. pachyderma. The terrigenous input of the Colombian Pacific rivers, particularly the San Juan River, is suggested as a possible mechanism. Finally, the Globorotalia cultrata /Neogloboquadrina dutertrei ratio, is used to reconstruct the past influence of the Costa Rica Dome - Panama Bight and cold tongue upwelling systems in the Panama Basin. A northern influence is suggested for the late Holocene (after 5ka), and the last glacial (before 20ka), whereas a southern influence is suggested for the 20 to 5ka interval. There is a correspondence between our reconstructed northern and southern influences and previously proposed positions of the Intertropical Convergence Zone (ITCZ) after the Last Glacial Maximum (LGM).
PP23B-1412 1340h
Holocene Sedimentation In The Southern Gulf Of California And Its Climatic Implications
Alfonso Basin on the western side of the Gulf of California and Pescadero Basin on the center slope of the east side of the gulf are margin basins which have sills or shoreward slopes in the Oxygen Minimum Zone and preserve primary varves whose physical and associated geochemical characteristics yield information on Holocene climate and oceanographic changes in the gulf. Primary productivity and sedimentation in the gulf are related to the dominant wind fields and the sediment record can be considered as an imperfect proxy of climate. Here we examine the sediment components in multicores, box and gravity cores recovered during cruises from 1994 to 2001 and show that the sediments provide an important history of the changing environment. Laminated, hemipelagic mud, accumulating at rates of 25-50 cm/kyr, were sampled at 1 cm intervals to produce a high resolution record of organic carbon, calcium carbonate (foraminifera and coccoliths), opal silica (diatoms, radiolaria) and terrigenous content, that was examined for variations in accumulation and preservation. Alfonso Basin sediments are organic carbon-rich (5-7%) with varying amounts of calcium carbonate (1-25%) and little opal silica ($ < $4%). Pescadero Basin sediments are also organic carbon-rich (2.5-4.3%) but contain less carbonate (0-6%) and more silica (8-21%). Changes on the sedimentation pattern for biogenic and terrigenous records occurred starting circa 7,200 YBP with major shifts occurring at 4200, 3000 and YBP typified by carbonate maxima. Smaller changes occurred at 1500, 950, and 400 YBP. Changes can be observed in both basins suggesting the events occurred across the whole southern gulf. The stepwise decrease in mass accumulation rates at 3000 and 1500 YBP indicate a shift of conditions that can be correlated to fall insolation records for the northern hemisphere, creating stronger NW winds and inhibiting the summer rains. Biogenic records (Opal and Carbonate) indicate a drop in productivity and terrigenous mud records suggest a shift from wetter to dryer conditions and perhaps from fluvial to eolic sedimentation. At 400 YBP a recovery is observed suggesting a return to wetter less windy conditions. These shifts also are reflected in sediment lamination. Three general periods are recognized; Early period (10,000-7,200 YBP) with high productivity and variability resulting from strong northwesterly winds and upwelling. Middle period (7,200-4,200 YBP) a stable period with steady decrease in productivity. And Late period (4,200 YBP to the present) with constant primary productivity suggested by opal fluxes, and with an increase in the carbonate-opal east-west asymmetry. Spectral analysis shows a 1-2 kyr climate rhythm in the Gulf and the data suggest that it is mediated by the migration of the Intertropical Convergence Zone (ITCZ) due to orbital precession. The records are marked by strong climate-ocean variability cycles with two modes: 210 years (throughout the record) and 800 years (after 3000 YBP) that appear related to latitudinal shifts of the ITCZ, produced by solar cycles.
PP23B-1413 1340h
High resolution paleoceanography of the central Gulf of California during the past 15,000 years
A high resolution paleoceanographic history of the central Gulf of California during the past 15,000 years has been assembled using microfossil (diatom and silicoflagellate) and geochemical proxy data from a composite section of gravity core GGC55 and giant piston core JPC56 in the western Guaymas Basin (27.5 deg. N, 112.1 deg. W, water depth 818 m) and from DSDP Site 480 (27.9 deg. N, 111.7 deg. W, 655 m water depth) in the eastern Guaymas Basin. These data argue for abrupt, basin-wide changes during the Bolling-Allerod, Younger Dryas, and earliest part of the Holocene that mirror changes documented in cores from the Pacific margins of both Baja and Alta California. Between about 10 ka and 6 ka, these central Gulf of California records became more regionally distinctive, as surface and intermediate waters resembling those of the modern-day northern Gulf became dominant and virtually no calcium carbonate or tropical microfossils were preserved in the underlying sediments. Beginning at about 6 ka, tropical microfossils returned to the central Gulf, possibly signaling enhanced El Nino-like conditions. Proxy data suggest that late winter-early spring coastal upwelling was abruptly strengthened on the mainland (eastern) side at about 5.4 ka and again at about 3.0 ka, whereas sediments from the western side of the central Gulf became increasingly diatom poor and calcium carbonate rich. An intensification of northwest winds during the late winter to early spring likely occurred in the central Gulf at about 5.4 ka. Interestingly, this proposed wind shift in the Gulf of California coincides with an abrupt 5.4 ka change to drier conditions in the Cariaco Basin off Venezuela that has been proposed to reflect a southward shift in the mean position of the Intertropical Convergence Zone in response to increasing El Nino-like conditions.
PP23B-1414 1340h
Decadal-Scale Variations in Eastern Pacific Thermocline Structure from Soledad Basin, Baja California
Soledad Basin, a semi-enclosed basin on the Pacific margin of southern Baja California at 25oN, is ideally located to document past variations of ocean/atmosphere interactions responding to the Pacific Decadal Oscillation (PDO) and the El Nino-Southern Oscillation (ENSO). Very high sedimentation rates (~108 cm/kyr; van Geen et al., Paleoceanography, v. 8, no. 4, 2003) combined with low bottow-water oxygen levels have prevented sediment bioturbation throughout the Holocene, setting the stage for high-resolution paleoclimatic reconstructions in this key climatic area. Current studies of this site focus on the combination of a 210Pb-dated multicore and 14C-dated gravity and piston cores. Available data include a 1-cm resolution diffuse spectral reflectance record, indicative of diagenetic processes linked to productivity (Ortiz et al., Geology, v. 32, no. 6, 2004) and Mg/Ca ratios for several planktonic foraminifera species. Mg/Ca results for two shallow-dwelling species in the multicore indicate little change in sea surface temperature (+/-1.1 deg C) over the mean value of 23 deg C observed over the past two centuries. In contrast, variations of Mg/Ca ratios for a deeper-dwelling species suggest considerably larger temperature variations of +/-1.8 deg C with respect to the mean value of 17.5 deg C at the depth habitat of this species. This suggests fluctuations in the temperature, and therefore nutrient content, of thermocline waters upwelling toward the surface at this site without any appreciable changes in upwelling. Periods of low subsurface temperatures in the water column inferred from Mg/Ca correspond to darker sediment bands, suggesting a connection between the structure of the thermocline, the supply of nutrients to the photic zone, and surface productivity. This interpretation is supported by elevated authigenic Mo concentrations in those same dark bands of 30-40 mg/kg. The presentation will include a comparison of these results with instrumental and other proxy climate records of the region and an extension of detailed reconstructions to several intervals of the Holocene.
PP23B-1415 1340h
Patchy deposits of Cenozoic pelagic sediments in the central Pacific
Export of pelagic carbonate tests from surface waters and their deposition at the sea floor plays a significant role in the CO2 cycle and ability of the oceans to absorb atmospheric CO2. Of importance to these, recent sediment 230Th and 3He measurements have been interpreted as evidence that significant lateral advection of pelagic material occurs in the water column, leading to marked spatial variations in deposition rates and in particular to significant focusing of deposits on the Pacific equator. We report spatially continuous stratigraphy from two 1000 km seismic lines which do show evidence of depositional anomalies near the equator. They show accumulation rates locally enhanced by a factor of two, similar to the proposed modern sediment focusing factors, but the anomalies are surprisingly patchy over the 20 Ma period analyzed - they are not confined to an equatorial region and they are not necessarily found on adjacent seismic profiles. These intermediate-scale anomalies are greater than 100 km across and represent areas of seafloor that received more deposits for one period, then less in following periods, and vice versa. Variogram analysis was used to determine how the spatial scales of deposition changed over the Neogene. The period when the spatial scale of depositional variability was largest correlates with hiatuses in drill cores, a correlation that we interpret as caused by enhanced and spatially heterogeneous carbonate dissolution at that time. The study suggests that seismic stratigraphy has the potential to reveal spatial patterns related to unsteady bottom water flow and chemistry.
PP23B-1416 1340h
Evolution in Planktonic Foraminifer Fauna and Sea Surface Temperature Variation in last 500 ky, Northern South China Sea
Site 1144 ($20\deg$3.18'N; $117\deg$25.14'E, 2037m) of Leg 184 of the Ocean Drilling Program was drilled on a sediment drift to provide a high resolution history of the South China Sea (SCS). The average sedimentation rate at this Site is $\sim$92.5 cm/ky, with the 517-meter section extending back to $\sim$1.1 Ma. We examined 280 samples from upper 300-meter that were collected at variable sampling interval corresponding to temporal intervals of 0.11$\sim$6.28 ky. Quantitative analysis reveals that the planktonic foraminifer (PF) fauna is dominated by 11 species that constitute nearly 88% of the average species population. Some species that account for smaller percent (5-10%) of the population (eg. {\it Pulleniatina obliqueloculata, Globigerinoides bulloides} etc.) appear to be dominated by glacial-interglacial scale variability while some species that account for larger percent (20-30%)of the population (eg. {\it Neogloboquadrina dutertrei, G. ruber} etc.) are dominated by higher frequency variability. A record of sea surface temperature (SST) was reconstructed for the past 500 ky using planktonic foram transfer function PF-12E. Variation of SST and some PF species share similarities with marine \delta$^{18}$O record (measured by C. B\"{u}hring {\it et al.}) indicating climatic teleconnection between high latitude of northern hemisphere and local environment. Higher frequency variability superimposed on the glacial-interglacial scale variability suggests orbital forcing at the precession frequency as well. The fragmentation index and benthic to planktonic foram ratio exhibit stronger calcium carbonate dissolution during interglacials relative to glacials, which may impact relative abundance variation patterns of several dissolution resistant species, such as {\it Globorotalia inflata} and {\it G. menardii}. Sub-orbital scale correlations are observed between SST, faunal assemblages and \delta$^{18}$O. For instance, increasing relative abundance of {\it Pulleniatina obliqueloculata} appears to be correlated to heavy \delta$^{18}$O events. In addition, we found that large decreases in winter SST are closely followed by the large scale demise or extinction of {\it G. ruber} (pink) in the SCS, for example, the event at the beginning of MIS 5 (SST dropped by $\sim$$6.5\deg$C within 1.5 ky) and the event at the end of MIS 13 (SST dropped by $\sim$$7.9\deg$C within 4.8 ky).
PP23B-1417 1340h
Holocene Pulleniatina Minimum Event: A Paleoecological Enigma in the Western Pacific
During the past decade, paleoceanographers have reported the so-called {\it Pulleniatina} Minimum Event (PME) at 4.5-3.0 ka from the Okinawa Trough and South China Sea. Several paleoenvironmental and tectonic causes have been invoked to explain the sudden decrease or disappearance of the planktonic foraminifer {\it Pulleniatina obliquiloculata} in such marginal seas. All these interpretations, however, might be misleading because of limited geographic observation and inappropriate proxies. In this study, we report new data from a suite of cores located from the Southern Okinawa Trough to the upper reach of the Kuroshio: MD012403 ($123.2\deg$E, $25.3\deg$N, water depth 1420 m), OR102-3P ($121.3\deg$E, $22.3\deg$N, water depth 1309 m) and MD982188 ($123.5\deg$E, $14.8\deg$N, water depth 730 m). All these three cores witnessed the PME during the period of 5.0 to 3.0 ka. We reconstructed the thermocline hydrography during the past 11 kyr at MD012403 and MD982188 by measuring the oxygen isotope values of the surface-dwelling foraminifer {\it Globigerinoides ruber}, and thermocline-dwelling {\it Globorotalia menardii}, {\it N. dutertrei} and {\it P. obliquiloculata}. No distinct or consistent anomalies can be identified in the $\delta$18O and $\delta$13C values in either core during this period. The reciprocal patterns in relative abundance between {\it P. obliquiloculata} and {\it N. dutertrei} can only be observed in MD012403 (Southern Okinawa Trough) and OR102-3P (off eastern coast of Taiwan). In MD982188 (western Philippine Sea), the relative abundances of {\it N. dutertrei} and {\it Globigerina bulloides} increase only after the PME. Accompanying the lightening $\delta$18O values of {\it N. dutertrei} and {\it P. obliquiloculata}, this faunal change implies a shoaling of the thermocline after 3 ka. These data shed some new lights on the nature of the PME: (1) PME is not a phenomenon restricted in the marginal seas, but widespread at least to the upper reach of the Kuroshio in the margin of the Western Pacific Warm Pool (WPWP). (2) No distinctive anomalies in the planktic isotope values are associated with the PME. This implies that no temperature/salinity changes of the surface waters were involved in this event. (3) The thriving of {\it N. dutertrei} during the PME in the subtropical sites might be a result of regional upwelling when surface waters were better mixed. In other words, {\it P. obliquiloculata} might be better adapted to the well-stratified oligotrophic tropical water than the opportunistic species {\it N. dutertrei}. The inability of using conventional paleoceanographic proxies to characterize this event implies our lack of appropriate understanding of this particular organism, and challenges the validity of our current usage of transfer functions or Modern Analog Technique in the western Pacific. New proxies (such as Mg/Ca ratios of multiple planktic foraminifers) and microfossil census data from a more extensively geographic coverage of the upper reach of the Kuroshio are needed to resolve this PME enigma.
PP23B-1418 1340h
Organic Carbon Accumulation in the Late Quaternary Santa Barbara Basin: A Comparison of Deep and Shallow Sites
Two giant piston cores obtained during the IMAGES MONA Cruise (2002) from central/deep (569 m) and marginal/shallow (481 m) sites in Santa Barbara Basin, CA, present a special opportunity for testing the relative importance of different environmental criteria for the preservation of organic carbon. The cores were deposited within and above the low-oxygen upper intermediate water mass, recording more consistently dysoxic (deep core) and consistently oxygenated (shallow core) settings. Samples were analyzed at 20 cm spacing ($\sim$140 yr) for total organic carbon (TOC), carbonate (CaCO3), C/N ratios, grain size and the mass accumulation rates of TOC and CaCO3 (MARTOC and MARCaCO3) from late Marine Isotope Stage 3 through the Holocene. As indicated by C/N ratios, the organic matter in both cores is a mixture of marine and terrigenous sources. Both TOC profiles display asymptotic curves that decrease with depth with little variation lower in the core in spite of significant changes in climate, bioturbation/lamination, and benthic foraminiferal populations. This confirms that anoxia, as indicated by sedimentary fabric and benthic populations, is not a prerequisite for enhanced organic matter preservation. MD2504, in the shallower slope setting, has sediments that are primarily coarser and organic components that are more marine in composition (including shell fragments). MD2503, the deep basinal core, primarily has very fine-grained sediments originating with a more terrigenous signature, suggesting more efficient routing of Santa Clara River-derived materials to the basin center than to the more proximal slope setting. The best correlations (covariation) in MD2503 are positive (TOC vs. C/N ratios and MARTOC vs. C/N ratios) during cold, oxygenated intervals of the Last Glacial Maximum, and Younger Dryas implying that for these climatic intervals, TOC correlates with the proportion of organic matter coming from terrigenous sources. During the Preboreal and Holocene in MD2504, times of warmth and higher sea level, the TOC increased when low C/N ratios indicate more marine-sourced organic matter. Peaks in percent silt during the Heinrich 1 event, the Younger Dryas and Preboreal intervals are possibly related to changes in precipitation or in distribution of river sediments associated with sea-level fluctuation.
PP23B-1419 1340h
A Continuous High-Resolution Climate-Proxy Record of the past 2600 Years from the Central Sahara Desert
Persistent lack of high-quality climate-proxy records from the arid-subarid belt of North Africa has hampered analysis of decade-to-century-scale climate tele-connections between warm-temperate southern Europe and the monsoonal climate regimes of sub-Saharan tropical Africa. Here we report recovery of a finely laminated sediment record from Lake Yoa, a stratified hypersaline lake occupying a Pleistocene deflation basin at Ounianga Kebir in northeastern Chad (20.0°N; 20.5°E). It represents a continuous, annual-resolution record of climate and environmental change during the past 2600 $^{14}$C years from the hyper-arid core of the Sahara desert where rainfall is erratic and annual evaporation exceeds 600 cm. Lake Yoa is one of the very few permanent waters in this region maintained today by sub-surface inflow of fossil groundwater from sandstone aquifers recharged during the early-Holocene humid period. Preliminary sedimentological, chronological and fossil-diatom data suggest that Lake Yoa has been poly- to hyper-saline throughout the sampled period, and with conditions of physical and chemical limnology similar to those prevailing today for at least the past 1000 years. Given that the desert landscape in a large area surrounding Ounianga probably lacked significant ground cover throughout this period, we surmise that variation in aeolian mineral sediment input to the lake, partly reflected in distinct sand layers, could be exploited as a proxy of past changes in the intensity of dry northeasterly trade winds over central North Africa.
PP23B-1420 1340h
East Asian Summer Monsoon Variability During Marine Isotope Stage 5 Based on Speleothem $\delta$$^{18}$O Records from Wanxiang Cave, Central China
Speleothems collected from Wanxiang Cave, China (33.31$\deg$ N, 105.00$\deg$ E) provide high-resolution records of East Asian paleomonsoon variability. Wanxiang Cave is located in a key climatic location, near the northern limit of the summer monsoon. We present a simple model for interpreting $\delta$$^{18}$O shifts in speleothems from this region. The $\delta$$^{18}$O of speleothem calcite at this site is inversely related to monsoon intensity. We show that temperature has little effect on the $\delta$$^{18}$O of precipitation near Wanxiang Cave and is most likely canceled out by the $-$0.24$\permil$/°C temperature effect on calcite-water fractionation. Given this, the largest magnitude $\delta$$^{18}$O shift that could occur due only to changes in the composition of the oceanic source region, the amount of rainfall, and the amount of evaporation between full glacial conditions with a weak summer monsoon and full interglacial conditions with a strong summer monsoon is 5.5$\permil$. It is, therefore, necessary to invoke past changes in the summer:winter precipitation ratio and circulation changes to explain the nearly 7$\permil$ range observed in fossil speleothems from this site. We present detailed $\delta$$^{18}$O records from two stalagmites, WXSM 51 and WXSM 52, which formed during Marine Isotope Stages 5a-5b and 5c-5d. During the MIS 5d-5c transition, summer monsoon intensity increased steadily from 117.6 ka, with a peak in intensity occurring at 106.8 ka, concurrent with Greenland Interstadial 24. During the MIS 5b-5a transition, monsoon intensity increased abruptly at about 85.7 ka, when $\delta$$^{18}$O decreased by approximately 4$\permil$ in 200 years. The close agreement of the MIS 5c-5d record and the MIS 5a-5b record with global climate records such as the GISP2, Vostok, and SPECMAP records, and the Northern Hemisphere insolation curve, suggest that East Asian summer monsoon intensity varies in phase with global climate fluctuations and is largely controlled by solar variations in the Northern Hemisphere. The MIS 5a-5b and 5c-5d paleomonsoon records from Wanxiang Cave also agree well with other records of Asian monsoon variability indicating that $\delta$$^{18}$O of speleothems from Wanxiang cave is a valid proxy for past changes in monsoon intensity.
PP23B-1421 1340h
Dating New York - Tracking the Retreat of the Laurentide Ice Sheet
The Laurentide Ice Sheet (LIS) covered the New York City area during the Last Glacial Maximum (LGM) and when it retreated carved out the present topography, exposing fresh bedrock. Although modernization has led to the modification of much of the present landscape, the New York area still features many attributes of the glacial sculpting. These attributes: glacially polished bedrock, erratic boulders and glacial moraines, remain as evidence of past climate change. Long Island represents a terminal moraine of the LIS, while areas in Central Park, Inwood (northern Manhattan) and the Hudson valley display beautiful retreat features. We present surface exposure dates of samples removed from these areas from the measurement of 10Be in them. This allows us to better understand the dynamics of the Laurentide Ice Sheet at the end of the last ice age. We will match the data with existing moraine records from the LIS as well as with mountain glacier records to determine whether or not (i) the LIS and the Scandinavian Ice Sheet were in sync; (ii) the huge LIS reacted more inertial than smaller systems to the climate reorganizations; (iii) the retreat pattern of the LIS.
PP23B-1422 1340h
A revised shallow-marine global stratigraphic template for Quaternary glacio-eustatic sea-level fluctuations from Wanganui Basin, New Zealand
Wanganui Basin, New Zealand, contains one of the most complete Quaternary stratigraphic records in the world. The ca. 2 km thick basin-fill for the last 2.6 Ma comprises 44 superposed 5th- and 6th-order shallow marine sedimentary cycles which correspond to individual 100 ka and 41 ka sea-level cycles since oxygen isotope stage 100. Stages 100 to 5 are represented by marine cyclothems, whereas stages 17 to 4 are represented by a suite of coeval and younger uplifted marine terrace sequences. The Milankovitch-frequency, shallow marine, cyclostratigraphy of Wanganui Basin is here correlated with the astronomically-calibrated oxygen isotope Plio-Pleistocene timescale. The presence of interbedded tephras and an established paleomagnetic stratigraphy allows the development of an integrated cyclostratigraphy for Wanganui Basin which correlates closely with the global oxygen isotope sea-level proxy. Lithogical and faunal variation in the cyclothems correspond closely to that predicted by the sequence stratigraphic model. Each sea-level cycle is represented by individual depositional sequence comprising transgressive (TST), highstand (HST), and regressive systems tracts (RST). In general, major sedimentary facies within the basin fill were deposited in a range of coastal plain, shoreface, and shelf marine environments during the rise, highstand and falling part of each glacio-eustatic cycle. Glacial stages are represented by regressive shoreline facies that are truncated above by surfaces of marine planation and bioerosion, and that mark both cyclothem and sequence boundaries. Here we present a revised astronomically calibrated cyclostratigraphy from Wanganui Basin using high-resolution outcrop, borehole and seismic records.
PP23B-1423 1340h
Holocene Changes in Atmospherical Circulation in the North Atlantic Region - Evidences for Millennial-Scale co-Variability Between Ocean and Atmosphere Circulation
Whereas a number of records from the marine realm have demonstrated Holocene changes regarded to be related to overturning circulation in the North Atlantic region, independent information of atmospherical variability from the terrestrial realm have proven more elusive to capture in palaeo-records. This is a major concern, as several studies have suggested that atmospherical forcing may be an important factor to understand the reconstructed variations in ocean circulation trough the Holocene. A number of studies considering the instrumental period have shown (A) that the atmospheric variability associated with the North Atlantic Oscillation (NAO) and sea-level pressure (SLP) in the North Atlantic is amplified in alpine areas on the western side of the Scandinavian mountain range, and is manifested as variations in the total winter accumulation in these areas. Moreover, it is (B) demonstrated that the spatial distribution of winter precipitation can be seen as a direct response to NAO and SLP variations. Three established Holocene glacier reconstructions are transferred into winter-accumulation signal, and viewed as palaeo-gauges of effective precipitation representing three regions in southern Norway, thereby allowing the spatio-temporal variations in winter-precipitation to be reconstructed. The vectors of westerly and southerly air-flow over southern Scandinavia is inversely modeled, and likely pressure-field patterns are identified for the last 6000 years with a 100 yr resolution. By comparing our results with information on North Atlantic Ocean circulation, we can for the first time demonstrate a consistent behavior between the ocean and independently reconstructed atmospherical circulation from the terrestrial realm, thereby presenting post priori support to the a priori hypothesis that wind-fields are inter-connected with variations in the ocean's circulation during the mid to late Holocene.
PP23B-1424 1340h
Geochemical Signatures in Corals from Looe Key, Florida since 1870 A.D.
Geochemical variations in modern and fossil coral skeletons (Sr/Ca, Mg/Ca, $\delta$$^{18}$O, $\delta$$^{13}$C) are increasingly being used to reconstruct climate variability in tropical ocean-atmosphere system on interannual to centennial timescales. Sub-annually resolved, centennial-length records of climate from the Atlantic that overlap with and extend beyond the instrumental record are sparse, yet required to assess interannual climate variations over decades to centuries. We address this data gap by presenting a %\sim$132 year time series of monthly geochemical variations in {\it Montastraea annularis} (complex) corals from Looe Key reef, Florida USA (24.5$\deg$ N, 81.4$\deg$ W). We first reconstructed estimates of hydrographic and temperature variability at Looe Key using temperature calibrations developed over the decade in which we have thermistor data. Calibration-verification exercises over this interval indicate differences in mean values of 0.6$\deg$C Sr/Ca-SST and 0.2$\deg$C $\delta$$^{18}$O-SST. Next we extended the calibration-verification intervals by comparing the coral geochemical variations with a SST record extracted from the HadISST 1.1 database using the appropriate 1$\deg$ by 1$\deg$ grid point for Looe Key. These longer-term verification exercises show a better agreement in estimation of the mean in $\delta$$^{18}$O-SST (0.15$\deg$C) than Sr/Ca-SST (0.47$\deg$C). Comparisons of monthly Sr/Ca and $\delta$$^{18}$O anomalies with monthly temperature anomalies over the entire record reveal weak relationships (r = -0.13, -0.10, respectively); however, there is a strong coupling between Sr/Ca and $\delta$$^{18}$O anomalies (r = 0.51) that shares spectral power in the decadal band. The relationship between decadally smoothed geochemical values and the AMO is also weak (r = -0.13, 0.09; for Sr/Ca and $\delta$$^{18}$O) despite a strong correlation between the AMO and SST from the Looe Key region (r = 0.72). The low correlation between SSTA/AMO and the coral proxies (Sr/Ca and $\delta$$^{18}$O), despite the good fit between the coral proxies themselves, could be the result of 1) difficulties in sampling the variable skeletal architecture of {\it Montastaea} or 2) it could indicate decoupling of the local thermal and hydrographic conditions from the larger-scale surface ocean conditions, which would suggest that a regional climate signal is being masked by local environmental variability at Looe Key. We are performing additional tests to better define the source of misfit between coral proxies and instrumental data at Looe Key.
PP23B-1425 1340h
Decadal and Centennial Variability of Climate From Isotopic Records in a Galapagos Coral
Radiocarbon and $\delta$$^{18}$O measurements of annual Galapagos coral bands will be presented for the period A.D. 1595 to 1954. Because radiocarbon ($^{14}$C) in the surface ocean has a long turnover time (10 years) with respect to exchange with atmospheric $^{14}$CO$_{2}$, $\Delta$$^{14}$C of dissolved inorganic carbon in surface seawater is a tracer of mixing between the surface and subsurface waters, or thermocline depth. A large shift in $\Delta$$^{14}$C values was observed around the beginning of the nineteenth century. A similar shift was not observed in a subtropical coral record from the southwest Pacific. Changes in circulation inferred from these data, and their implications for the regional net efflux of CO$_{2}$ from the eastern tropical Pacific to the atmosphere, will be discussed.
PP23B-1426 1340h
Fidelity of Stable Oxygen Isotope Ratios as Environmental Recorders Using Multiple Coral Cores From Coastal Kenya
Climate variability in the western equatorial Indian Ocean reflects the combined influence of seasonally changing sea surface temperature (SST), ocean currents, and monsoon circulation, as well as inter-annual to -decadal variability associated with ENSO in the Pacific. However, the Indian Ocean also exhibits variability that appears unrelated to ENSO in the Pacific. The nature of interactions between air-sea variability in the Indian and Pacific oceans is not yet fully resolved, in part because of the lack of long-term, high-resolution SST records from key localities in the Indian Ocean. Such records are now being obtained using oxygen isotope profiles measured on corals from East Africa, Indonesia, Australia, and Indian Oceania (Maldives, Seychelles), with the longest coral-based time series from Malindi, Kenya, covering the last 300 years at near-monthly resolution. The value of these developing coral records depends on the fidelity with which they record regional climate variability. In order to assess the fidelity of oxygen isotope ratios (\delta$^{18}$O) in Indian Ocean corals as a proxy for sea surface temperature, we have generated stable isotopic time series from multiple Porites lutea coral heads collected along the coast of Kenya. Coral-based isotopic paleoclimatology is labor and time-intensive so detailed analyses using multiple coral heads from different sites within a region are extremely rare. Most published records are produced from a single coral head, yet questions have been raised about the accuracy of such records. To address such concerns, near-monthly resolution isotopic profiles, spanning 10 to 50 years prior to 1997, were measured on a total of 8 cores from five sites along a north-south transect between $2\deg$ and $4\deg$S (Kiwayu: $2\deg$2'S, $41\deg$2'E, Malindi: $3\deg$14'S, $40\deg$8'E, Watamu: $3\deg$23'S, $39\deg$52'E, Mombasa: $3\deg$59'S, $39\deg$5'E, and Kisite: $4\deg$43'S, $39\deg$23'E. Correlations among individual \delta$^{18}$O time series (r values range from 0.65 to 0.80) reveal that sample- and site-specific effects do not sufficiently bias \delta$^{18}$O such that regional climate signals cannot be discerned from any of the 5 sites. Furthermore, correlation of all individual oxygen isotope time series with instrumental monthly SST yields r values between -0.70 and -0.75, demonstrating that fluctuations in \delta$^{18}$O primarily reflect variations in SST. Although correlation coefficients between \delta$^{18}$O and instrumental monthly SST are higher using either single-site composite \delta$^{18}$O time series, such as for Malindi (r = -0.76), or a multisite, multi-core composite (r = -0.81), these correlation coefficients are only slightly higher than those for individual coral \delta$^{18}$O time series. We conclude that in this case, the cost of developing replicate coral delta$^{18}$O time series from individual sites may not be warranted in terms of a marginal gain in signal-to-noise ratio. Our work suggests that a 300 year long, near-monthly \delta$^{18}$O record from a single coral head from Malindi, can be used with confidence for environmental reconstructions in the western equatorial Indian Ocean.
PP23B-1427 1340h
A coral record from the West Pacific Warm Pool (New Georgia)
The Western Pacific Warm Pool (WPWP) acts as the heat engine for Earth's climate and as a major moisture source for the global hydrological cycle. There is a long-standing uncertainty about the stability of SST changes in this key region. Here we use elemental ratio (Sr/Ca) and oxygen isotope data from a Porites coral head collected offshore Gizo Island, New Georgia (8$\circ$ S, 155$\circ$ E), a site that is located in the warmest part of the WPWP, to assess the degree to which changes in these geochemical variables reflect variations in sea surface conditions. Contrary to other regions, the Sr/Ca and SST relation is unimpressive in the raw data (r= -0.4). Removal of a PDO (Pacific Decadal Oscillation) signal improves the correlation (r= -0.67), but it is still less than the normal Sr/SST correlation. The correlation between ENSO filtered Sr/Ca and SST also shows decadal variations, following the phase shift of PDO index. It is generally highly correlated when warm PDO regimes dominated ( $\mid$r$\mid$ = 0.74 $\sim$ 0.88), and poorly correlated when cool PDO regimes prevailed ( $\mid$r$\mid$ $\leq$ 0.3). We therefore used cyclostationary EOFs to develop a transfer function to isolate the annual cycle in the Sr/Ca record and get a much more reliable estimate of SST (r= 0.86, from 1932 to 1964). A prediction of the linear growth rate curve suggests that the bottom of the core is $\sim$ 1706, thus this may be the first coral record with the potential of extracting a Little Ice Age signal from the WPWP.
PP23B-1428 1340h
Thermal, hydrological, and biological signals with constraints of geochemical records in coral skeletons, southern Taiwan
Combination of {\it Porites} $\delta$$^{18}$O and Sr/Ca records can be utilized to reconstruct not only the thermal but also hydrological history, which is based on that coral Sr/Ca is controlled by SST and seawater Sr/Ca while $\delta$$^{18}$O is by SST, salinity, and rainfall-influenced seawater $\delta$$^{18}$O. Therefore, residual $\delta$$^{18}$O extracted by removing temperature effects enable us to explore the variation of seawater $\delta$$^{18}$O that is governed by salinity-induced and rainfall-induced changes. We use the Q-ICPMS (Agilent 7500s, equipped in NTU) to efficiently and successfully analyze the coral samples under the precision of 4\permil for Sr/Ca. A twenty-years-old living {\it P. lobata} coral collected in southern shallow sea of Taiwan (namely Nanwan) was subsampled by the resolution of 2-3 weeks along maximum extension axis. Each sample was firstly rinsed by HClO, and then cleaned by the standard procedure. Our Sr/Ca results of 2002\sim2003 after normalizing the seawater Sr/Ca between Nanwan and Hawaii show a similar regression as previous presented, i.e., Sr/Ca ($\mu$mole/mole) = -0.0517\times SST (\deg C) +10.316. By removing SST-induced $\delta$$^{18}$O variations, the fluctuant pattern of residual $\delta$$^{18}$O from the middle 2001 to beginning of 2003 is qualitatively consistent with that of independently precipitation records. However, it is still not sufficient for us to establish a simply quantitative relationship, possibly derived from the complex hydrology. In addition, the $\delta$$^{13}$C values of coral skeleton in spawning season of 1994 and 1995 surprisingly show negative anomalies, probably inferring a reduced spawning or even ceased. The independent support is that the coral underwent relatively high extension rates in above-mentioned two years than the other years where the produced energy is distributed to both of growth and spawning. Based on the ecological site survey and the morphology of collected coral, the anomalies are probably related to the anemone booming event in the surrounding sea.
PP23B-1429 1340h
Natural Variability of Environmental Proxies in Corals from an Upwelling Region
The ratios of cadmium to calcium (Cd/Ca) and barium to calcium (Ba/Ca) chronicled in coral skeletal records are promising, yet uncalibrated, proxy tracers of oceanic upwelling. To date there has been no rigorous experimental evaluation of the natural variability of these elements among coral individuals, between species or across depth. Without an understanding of this variability, comparison of such proxy-derived records could yield inaccurate results. As a first step towards the quantitative development of these tracers, preliminary results from a survey of skeletal Cd and Ba (3 species, 2 depths, 30 individuals) will be presented, as well as stable oxygen and carbon isotopic values. {\it Pavona gigantea}, {\it Pavona clavus} and {\it Porites lobata} coral fragments were grown under monitored conditions during upwelling and non-upwelling periods in the Gulf of Panama (Pacific Ocean); the associated sea surface temperature, subsurface light intensity and nutrient concentration data will be compared to the skeletal records. Initial data from {\it P. clavus} does indicate a clear relationship between upwelling conditions and skeletal Cd/Ca. Once the range of natural variability in these fragments has been determined, the Cd/Ca and Ba/Ca ratios can then be evaluated against ocean conditions with an improved understanding of any species-specific offset or depth adjustments that should be made when comparing data sets. As quantitative upwelling proxies, coralline Cd/Ca and Ba/Ca could dramatically contribute to our understanding of the natural variability and intensity of oceanic upwelling events, and tropical climate variability on seasonal-to-centennial timescales.
PP23B-1430 1340h
Sea Surface Temperature Variability in the Southwest Pacific as Reconstructed from the Skeletal Geochemistry of a Tricentennial Coral from New Caledonia
We reconstruct sea surface temperatures (SST) and SST variability in the southwestern tropical Pacific back to $\sim$1654 A.D. using Sr/Ca and Mg/Ca variations in a {\it Porites} {\it lutea} coral collected offshore of Am\'{e}d\'{e}e Island, New Caledonia ($22.29\deg$S, $166.28\deg$E). Monthly samples were extracted along a path parallel to the previous sampling of this coral slab, samples from which were used to generate a seasonally resolved stable isotope record. The monthly Sr/Ca time series correlates well with the seasonal $\delta$$^{18}$O time series over the entire length of the record. There is a long-term trend of increasing SST over the length of the Sr/Ca-SST time series, the magnitude of this increase is $\sim$$1\deg$C. Temperatures in the twentieth century section of Sr/Ca-SST time series are the warmest, whereas temperatures in the eighteenth century section are the coolest. Spectral analysis (MTM) of the coral Sr/Ca time series identifies concentrations of variance ($ > $95% confidence) in the interannual and decadal band. Wavelet analysis of the coral Sr/Ca time series demonstrates that decadal-scale variability is particularly prominent in the middle of the eighteenth century and during the second half of the nineteenth century. Quantitative comparisons with other long coral records and with a suite of climate indices are in progress.
PP23B-1431 1340h
Biogenic Magnetite and Magnetostratigraphic Dating of Shallow-Water Carbonates from the Ryukyu Islands, Northwestern Pacific
Magnetostratigraphy in shallow-water carbonates has been used successfully for establishing polarity reversal sequences and determining chronologies. However, this has only rarely been attempted for the Pleistocene shallow-water carbonates (the Ryukyu Group) of the Ryukyu Islands in northwestern Pacific. Here I describe the magnetic grains contained in the Ryukyu Group and in Holocene unconsolidated surface sediments (the Kerama Islands; intertidal zone, 10m, 15.5m, 91m in water depth) using transmission electron microscope (TEM). I also show the successful magnetostratigraphic dating of a core from the Ryukyu Group on Irabu Island. Carbonate environments of the Ryukyu Islands are essentially isolated from detrital sources because the Kuroshio Current prevents the input of terrigenous material from the Asian continent. Sediments consist of pure carbonates, and only rarely contain detrital magnetic particles. Extracted magnetic particles reveal the presence of single-domain crystals of magnetite similar to those produced by magnetotactic bacteria. Widespread occurrence of single-domain magnetite in these pure carbonates suggests that bacterial magnetite is probably the major carrier of early in-situ depositional magnetization. On the basis of the remnant magnetism of 56 samples from a 61-m core taken from the Ryukyu Group, the polarity sequence can be correlated with the magnetic polarity time scale from the Matsuyama chron containing the Jaramillo subchron to the Brunhes chron. This age-estimate is fixed by biostratigraphic datums. Magnetic polarities were determined on the basis of relative up-down direction in the unoriented core. The results suggest that magnetostratigraphy, based presumably on bacterial magnetite, can be a powerful chronostratigraphic tool in the shallow-water carbonates of the Ryukyu Islands, which contain very little detrital magnetite.
PP23B-1432 1340h
Fulfilling the Promise of the DSDP/ODP Legacy with Multiparameter Logging of Archive Cores
Since 1968, the Deep-Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP) have been storing their recovered sediment and rock cores in purpose-built, refrigerated repositories. Approximately 300 km of core was recovered by DSDP and ODP at an estimated average cost of $2,000,000/km. Half of every core recovered is kept as an archive half, normally only available for viewing (subsampling requires special permissions). Sound archiving policies and storage techniques over the years have ensured that these half cores have remained well preserved for analyses that were not made, or were not technically possible, at the time of recovery. The archive half-cores are well suited for automated non-destructive geophysical measurements ("core logging"), including many of those that provide essential data for reconstructing Earth's climatic history, such as high-resolution magnetic susceptibility, natural gamma spectroscopy, and UV/VIS/IR spectrophotometry. Most of the cores have either not been logged for all the relevant parameters or have not been logged at the spatial intervals necessary for high resolution climatic studies. Consequently, a very large, untapped reservoir of paleoclimatic and other data awaits extraction from these well-preserved archive half-cores. Recently we used a new Geotek MSCL-XYZ core logger at the IODP West Coast Repository to log archive core halves recovered by D/V Glomar Challenger in 1983. We wished to obtain a high-resolution paleoclimate record for DSDP Site 594, east of New Zealand, Southwest Pacific, to complement the record obtained more recently from nearby ODP Site 1119, cored in 1998. The new MSCL-XYZ system is specifically designed to allow multiparameter, non-destructive geophysical data to be collected easily at high spatial resolutions from archive core halves. Because the data acquisition from archive cores can be slow, either because of the measurement itself or the frequency at which the data is required, the system holds multiple 1.5 m-long core sections (currently up to 9) and can be left to run unattended for hours or days at a time. We obtained complete data sets of natural gamma, magnetic susceptibility, spectral color and RGB digital line scan images for the top 150m of the sediment column at Site 594 . No useful core log data was previously available for this site. The data set of primary interest was natural gamma, which will be compared with the downhole natural gamma record from Site 1119. To our knowledge this is the first time that a high-resolution natural gamma data log has been recovered from an archive core half. Detailed magnetic susceptibility records were also obtained despite low signal levels, using 10 sec sampling time throughout. The excellent quality of the spectral color and RGB image data, despite the partially ephemeral nature of these properties, is a testament to the core storage techniques employed over 21 years. As core working halves become depleted, pressure is mounting to allow subsampling from the archive core-halves. The community now has the tools necessary to take advantage of what could be a final opportunity to collect continuous geophysical data on ocean cores drilled over the past three decades.
PP23B-1433 1340h
OSL Dating of Diatoms: A Potential Application of an Established Chronometric Method
G.A. Wagner (1998) lists 65 different geological, archaeological and historical materials that can be dated by a broad spectrum of chronometric methods. OSL ages of diatoms would contribute to studies of paleoclimatological and chronological significance which until now have been obtained using TL, 226Pa and 32Si methods. OSL dating of diatom tests has been attempted at the Luminescence Dating Laboratory, School of Earth Sciences, Victoria University Wellington. Two samples differing in age, origin (fresh water and marine) and genus/species were selected for dating. Until now, OSL dating of continental and marine sediments has focused on materials of inorganic origin and siliceous composition. This study's diatom tests have been buried concomitantly with such materials and hence exposed to the same doses of radiation so a direct comparison of ages can be made. Although diatom skeletal composition is opaline and structure is amorphous not crystalline, the diatom tests may contain long-term stable traps in microcrystalline phases. Trials of methods of diatom isolation and preparation, determination of light sensitivity, dose dependency and long-term stability of diatoms are described and age results presented for diatoms from two cores. The first, late-Pleistocene freshwater diatom ooze (dominant Cyclotella stelligera), is from the Auckland New Zealand Pukaki Maar Crater (core Pukaki 1-01). It has excellent independent age control from associated Kawakawa and Rotoehu tephras ($ > $26 and $ < 55$ ka). The second is a RV Maurice Ewing northern North Atlantic Ocean core containing marine isotope substage 5e (130-115 ka BP) monospecific laminated diatom ooze (pinnate diatom- Thalassiothrix longissima). Our results reflect the need to attend to preparation, dose dependence, stability, measurement parameters and signal detection. The potential and problems of OSL-based chronometric studies utilizing diatoms will be reported. Additional studies of an extended suite of diatom bearing samples are planned.
PP23B-1434 1340h
Optical Dating of Marine Sediment From ODP Core 658B - An Intercomparison With an Independent AMS 14C Chronology
We demonstrate the potential of optical dating of detrital quartz silt from marine sediments via a chronological intercomparison for samples from ODP Site 658, which range in age from 0 to 140ka. ODP Site 658 is located off Cap Blanc, Mauritania. It has a high sedimentation rate (18 cm/ka), due to high regional surface productivity and large inputs of windblown Africa dust. This windblown dust provides both the substrate for optical dating and a proxy for North African aridity. The AMS 14C chronology is based on monospecific foraminiferal (Globigerinoides bulloides) samples. This is the first large-scale, systematic application of optical dating to marine sediment, and demonstrates that the technique has considerable potential for the age estimation of otherwise undateable deep-sea material. Optical dating techniques measure the total ionising radiation dose that a mineral grain has received since its last exposure to sunlight (i.e. during burial). The resulting optical age is essentially calibrated via a knowledge of the environmental dose rate, yielding the burial period. The environmental dose rate is derived from the decay of radioisotopes in the sediment (K, U and Th). In terrestrial sediments, the uranium and thorium decay chains can be assumed to be in equilibrium. In the marine realm this assumption is not valid, and unsupported uranium decay series exist on deposition. Consequently, the environmental dose rate changes with sample age. This problem was circumvented by quantifying U and Th decay series disequilibrium, using an MC-ICP-MS. The evolution of the environmental dose rate during burial was modelled, and ages for each sample calculated. The 14C and optical ages are generally in good agreement, indicating that the latter technique can provide equally robust chronologies for marine sediments. Although the maximum age attainable using optical dating is sample specific, the dose rate and luminescence characteristics of the samples analysed in this study indicate that marine sediments ranging from 0-200ka should be dateable. Very precise (1-3%) burial doses and radioisotope concentrations were obtained, although ultimately precision is limited to about 10% due to uncertainties in the moisture content, source calibrations and dose rate conversion factors. However, over the timescales that optical dating is applicable, these overall errors are not inconsistent with the rarely quoted precision accorded to orbitally tuned records. Optical dating should provide a valuable geochronological tool for marine sediments extending well beyond the time range of 14C dating, and for dating marine sediments that contain no dateable carbon.
PP23B-1435 1340h
Accessing Silver as a Paleoceanographic Proxy
A strong correlation has been found between dissolved silver and silicic acid at several locations in the sea, especially in the Pacific. This has led to the hypothesis that diatom opal acts as a vector of silver to the sea floor. If so, and if silver released by dissolution is sequestered by the sediments, it is possible that downcore sedimentary silver concentrations could be used as a paleo-proxy for the diatom settling flux. However, recent studies have found that the Ag:H4SiO4 correlation is weak in some areas and a more detailed examination of the Ag:Si relationship is needed before any paleo-inferences can be made from sedimentary silver concentrations. Toward this end, a 13 month time series study has begun in Saanich Inlet, BC, Canada, focusing on silver and silicate levels in sediment trap materials, water column samples and the underlying sediments. Initial results show that silicate levels were reduced by up to 80% in the upper 80 m of the water column during the spring bloom. It is expected that silver levels will show a similar depletion. The results of dissolved and particulate silver analyses now underway will be presented at the meeting, in conjunction with a suite of supporting data (sediment-trap opal, organic carbon and nitrogen contents, and dissolved nutrient measurements). The anticipated results and their interpretation should contribute to the potential calibration of the sedimentary Ag content as a paleotracer of diatom production.
PP23B-1436 1340h
Inferring Paleoenvironments Using Seasonal Isotope and Trace-Metal Profiles of Serially-Sampled Gastropods
Early Cenozoic (e.g., Eocene-Oligocene), foraminiferal records of tropical SSTs are controversial, due to the possible alteration of the shells' isotopic and elemental composition by diagenetic recrystalization. Here we test the fidelity of shallow water molluskan skeletons as an alternative archive of tropical SSTs. Because of the long life-spans and rapid growth of mollusks, mollusk shells provide excellent records for Cenozoic seasonality, provided that seasonal variations in the isotopic and trace-metal composition of the carbonate shells reflect the ambient temperature and $\delta^{18}$O of the water in which the organisms grew. To evaluate the fidelity of gastropod skeletons as recorders of such paleoenvironmental information, we performed isotopic and trace-metal analyses on specimens of {\it Conus ermineus} from the Gulf of Mexico. Three adult specimens were collected at Stetson Bank in the Flower Garden Banks National Marine Sanctuary from depths of 21-24 m. Two were sampled alive and remain in aquaria. The shells were milled parallel to growth banding to produce time series profiles along the axes of growth. These profiles were compared with temperature and salinity records from water quality data recorders at the reef surface for the later part of the growth period. For the earlier growth record, we estimated 24 m temperatures using records from nearby surface data buoys. The $\delta^{18}$O and Sr/Ca profiles covary in a saw-tooth pattern, with a high degree of coherency. Such saw-tooth patterns are often interpreted as resulting from slower growth rates during summer and winter months. However, environmental records show that temperatures at 24 m change in a pattern similar to that seen in the profiles, with summer warming at 24 m lagging behind warming at the surface by up to three months. This asymmetric pattern of temperature change suggests that the shapes of isotope and trace-metal profiles may be dominantly controlled by local hydrography, rather than by intra-annual changes in growth rates. The strong similarity between the Sr/Ca profiles and {\it in-situ} temperature records suggests that Sr/Ca can be used as a paleothermometer in aragonitic mollusks. Regression of temporally-tuned metal profiles against temperature records suggests a 5$\pm$0.8% increase in Sr/Ca per degree Celsius over the range of 19$\deg$ to 30$\deg$C. Therefore, using paired $\delta^{18}$O and Sr/Ca measurements in {\it Conus} shells can provide reconstruction of variations in sea surface temperature and salinity in the past.
PP23B-1437 1340h
Methane Venting Documented by Lowest Hitherto Reported $\delta$$^{13}$C of Live Epibenthic Foraminifer {\it Fontbotia wuellerstorfi}
To investigate the use of benthic foraminifera as a means to assess modern and document ancient methane release, we determined the stable isotopic composition of tests of several live and dead species. Foraminiferal shells were collected from three push-core samples obtained with a ROV and three multiple corer samples. All samples are from the Haakon Mosby Mud Volcano (HMMV), a cold methane-venting seep at the Barents Sea continental slope in 1250 m water depth. We compared stable isotope ratios of these samples with those from a close-by reference station being not influenced by methane seepage but otherwise by the same overall environmental conditions. In areas densely populated by pogonophors, $\delta$$^{13}$C values of live {\it F. wuellerstorfi} are by 4.4$\permil$ lower than at the reference station and thus the lowest values hitherto reported for this species. Also {\it Cassidulina neoteretis}, a common shallow infaunal high Arctic species, reaches $\delta$$^{13}$C values of -7.5$\permil$ VPDB, which is by 6.2$\permil$ lower than at reference station. Surprisingly, $\delta$$^{13}$C of empty {\it F. wuellerstorfi} and {\it C. neoteretis}, tests are by 1 to 2$\permil$ and by about 4$\permil$, respectively, higher than those of live specimens, although still significantly lower than empty tests from the reference station. This documents that overgrowth at or below the sediment surface is not influencing the stable isotopic composition of these shells. It rather demonstrates that disturbance of sediments due to upward convection of porewater and fluid mud during active methane venting phases at this site mingles tests just recently calcified with older ones secreted at intermittent times of less or no methane discharge. Live epibenthic and shallow endobenthic foraminiferal $\delta$$^{13}$C values at HMMV exceed those that could be due to organic matter decomposition and thus in fact document active methane release. However, empty test $\delta$$^{13}$C values do not differ significantly from those measured in high productivity non-seep environments, but might be distinguished by their greater carbon isotopic variability.
PP23B-1438 1340h
Benthic Foraminiferal Responses to Seasonal and Spatial Changes in Organic Input Within the Southern California Bight
One of the primary means to determine ancient changes in productivity is through the use of microfossils. Although abundance changes in fossil benthic foraminiferal assemblages are used to assess paleoproductivity, questions remain about the use of this method in areas with high organic carbon input. This study examined intra-annual (Oct. 1995 to Oct. 1996) and spatial changes in living (Rose Bengal stained) foraminifera from the $ > $150 micron and $ > $63 micron fractions collected at two sites along a sea-surface productivity gradient within the Southern California Bight. Foraminiferal density increases of the 63-150 micron and $ > $63 micron fractions were positively related to surface productivity in this region. In contrast, abundances of the $ > $150 micron fraction appeared negatively correlated with surface productivity. Comparisons of vertical profiles showing changes in abundances within the sediments revealed appreciable differences in patterns for the $ > $150 micron and the $ > $63 micron fractions. Vertical profiles of foraminiferal densities from the $ > $63 micron fraction showed surface maxima (0-1 cm interval) for all seasons at both sites, except in May at the southern (lower surface productivity) site. Vertical profile patterns for the $ > $150 micron fraction were more variable. At the southern site, total foraminiferal abundances in May reached a subsurface maximum at the 1-1.5 cm interval, and abundance patterns were similar for both the $ > $150 micron and the $ > $63 micron fractions. Based on these modern analog results, examination of the $ > $63 micron fraction is a viable, necessary means for benthic foraminiferal assessments of paleoproductivity in organic rich environments.
PP23B-1439 1340h
Stable Carbon and Oxygen isotopic analysis of sub-microgram quantities of CaCO$_{3}$ and the application to the analysis of single small foraminiferal shells.
~ We developed an analytical system to determine stable isotopic compositions ($\delta$$^{13}$C and $\delta$$^{18}$O) of sub-microgram quantities of CaCO$_{3}$ for the purpose of analyzing individual foraminiferal shells, using continuous-flow isotope ratio mass spectrometry (CF-IRMS). The system consists of a micro volume CaCO$_{3}$ decomposition tube, stainless steel CO$_{2}$ purification vacuum line with an introduction quantity regulating unit, helium-purged CO$_{2}$ purification line, gas chromatograph, and CF-IRMS. By using this system, we can determine stable carbon and oxygen isotopic compositions as low as 0.2 $\mu$g of CaCO$_{3}$, with standard deviations of $\pm$0.10 $\permil$ for $\delta$$^{13}$C and $\pm$0.18 $\permil$ for $\delta$$^{18}$O within a 4-hour reaction time and 30-minute analysis. Our method has the advantage that we do not have to regulate the weight of CaCO$_{3}$ to react with H$_{3}$PO$_{4}$ because we can regulate the introduced quantity of CO$_{2}$ within the stainless steel vacuum line. ~ By using the system, we can determine the $\delta$$^{13}$C and $\delta$$^{18}$O values for individual small foraminifera whose weight is below 10 $\mu$g (e.g. {\it Globocassidulina} sp.). That is to say, we can determine the $\delta$$^{13}$C and $\delta$$^{18}$O values for almost all kinds of calcareous foraminifera. Thus, we can apply the isotopic studies of foraminifera to seafloor sediments in which limited numbers of small shells are available (e.g. at high latitudes, in the deep sea around CCD, or in the seafloor fluid seepage area). In addition, in the case of large-sized calcareous foraminifera, we can determine the $\delta$$^{13}$C and $\delta$$^{18}$O differences between the fragments within a single shell. Partial analysis of their shells will be useful not only for paleoceanography but also for ecological research. ~ Using the system, we determined $\delta$$^{13}$C and $\delta$$^{18}$O values of a small-sized hyaline calcareous foraminifera {\it Globocassidulina} sp., about 210 $\mu$m in diameter and 3 $\mu$g of weight, collected from the top part (0-1cm) of a sediment core. The analytical result shows the isotopic compositions and dispersions of {\it Globocassidulina} sp. as -1.66$\pm$0.17 $\permil$ $_{PDB}$ for $\delta$$^{13}$C and +2.88$\pm$0.31 $\permil$ $_{PDB}$ for $\delta$$^{18}$O (1$\sigma$, n=10). Each measured value of single {\it Globocassidulina} sp. coincided well with those of multiple shells. No systematic difference was observed for the isotopic values between the living and the dead.
PP23B-1440 1340h
High precision measurement of Mg/Ca and Sr/Ca ratios in carbonates by cool plasma quadrupole inductively coupled plasma mass spectrometry
We have developed a high-precision analytical technique using an quadrupole inductively coupled plasma mass spectrometer Agilent 7500s, for simultaneously measuring Mg/Ca and Sr/Ca ratios in carbonates, which are broadly used as environmental and climatic proxies in the Earth Sciences. Cool plasma technique with 650-W RF power was employed to diminish spectral interference. A desolvation introduction system was used to enhance sensitivity, improve detection limit and reduce sample size. Intensities of isotopes, including $^{24}$Mg, $^{43}$Ca and $^{86}$Sr, were all detected in pulse-counting mode. Mg/Ca and Sr/Ca ratios were calculated directly from intensity ratios, $^{24}$Mg/$^{43}$Ca and $^{86}$Sr/$^{43}$Ca, using external matrix-matched standards to correct for instrumental mass discrimination and low-frequency ratio drift. For Mg/Ca analysis, matrix effect of Ca level is 0.018 Mg/Ca (mmol/mol) / [Ca] (ppm). This problem can be overcome by holding [Ca] from 6-8 ppm in sample solution or correcting measured ratio with an empirical formula. Different Sr/Ca also slightly affects Mg/Ca determination with a slope of 0.017 Mg/Ca (mmol/mol) / Sr/Ca (mmol/mol). It is mainly caused by the formation of doubly-charge ion of $^{86}$Sr, which biases intensity measurement of $^{43}$Ca$^{+}$ ion beam. This effect brings about only a trivial offset less than 0.1% on Mg/Ca determination for Quaternary foraminiferal and coral samples. Internal precision given by our method ranges 0.1-0.2% (2sd). Replicate measurements made on standards and samples show that external uncertainties of 0.5% and 0.4% (2sd) can be achieved for Mg/Ca and Sr/Ca, respectively. Requirement of a small sample size of only 3.5 microgram carbonate even allows investigating characteristics of single foraminiferal chamber.