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  • 1
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    PANGAEA
    In:  Supplement to: Klinkhammer, Gary P; Haley, Brian A; Mix, Alan C; Benway, Heather M; Cheseby, Maziet (2004): Evaluation of automated flow-through time-resolved analysis of foraminifera for Mg/Ca paleothermometry. Paleoceanography, 19(4), PA4030, https://doi.org/10.1029/2004PA001050
    Publication Date: 2020-01-17
    Description: The primary Mg/Ca ratio of foraminiferal shells is a potentially valuable paleoproxy for sea surface temperature (SST) reconstructions. However, the reliable extraction of this ratio from sedimentary calcite assumes that we can overcome artifacts related to foraminiferal ecology and partial dissolution, as well as contamination by secondary calcite and clay. The standard batch method for Mg/Ca analysis involves cracking, sonicating, and rinsing the tests to remove clay, followed by chemical cleaning, and finally acid-digestion and single-point measurement. This laborious procedure often results in substantial loss of sample (typically 30-60%). We find that even the earliest steps of this procedure can fractionate Mg from Ca, thus biasing the result toward a more variable and often anomalously low Mg/Ca ratio. Moreover, the more rigorous the cleaning, the more calcite is lost, and the more likely it becomes that any residual clay that has not been removed by physical cleaning will increase the ratio. These potentially significant sources of error can be overcome with a flow-through (FT) sequential leaching method that makes time- and labor-intensive pretreatments unnecessary. When combined with time-resolved analysis (FT-TRA) flow-through, performed with a gradually increasing and highly regulated acid strength, produces continuous records of Mg, Sr, Al, and Ca concentrations in the leachate sorted by dissolution susceptibility of the reacting material. Flow-through separates secondary calcite from less susceptible biogenic calcite and clay, and further resolves the biogenic component into primary and more resistant fractions. FT-TRA reliably separates secondary calcite (which is not representative of original life habitats) from the more resistant biogenic calcite (the desired signal) and clay (a contaminant of high Mg/Ca, which also contains Al), and further resolves the biogenic component into primary and more resistant fractions that may reflect habitat or other changes during ontogeny. We find that the most susceptible fraction of biogenic calcite in surface dwelling foraminifera gives the most accurate value for SST and therefore best represents primary calcite. Sequential dissolution curves can be used to correct the primary Mg/Ca ratio for clay, if necessary. However, the temporal separation of calcite from clay in FT-TRA is so complete that this correction is typically 〈=2%, even in clay-rich sediments. Unlike hands-on batch methods, that are difficult to reproduce exactly, flow-through lends itself to automation, providing precise replication of treatment for every sample. Our automated flow-through system can process 22 samples, two system blanks, and 48 mixed standards in 〈12 hours of unattended operation. FT-TRA thus represents a faster, cheaper, and better way to determine Mg/Ca ratios in foraminiferal calcite.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 2
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 66 data points
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  • 3
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 130 data points
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  • 4
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 68 data points
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  • 5
    Publication Date: 2020-01-18
    Type: Dataset
    Format: text/tab-separated-values, 199 data points
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  • 6
    Publication Date: 2020-01-18
    Type: Dataset
    Format: text/tab-separated-values, 96 data points
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  • 7
    Publication Date: 2020-01-18
    Type: Dataset
    Format: text/tab-separated-values, 39 data points
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  • 8
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    PANGAEA
    In:  Supplement to: Oyun, S; Elderfield, Henry; Klinkhammer, Gary P (1995): Strontium isotopes in pore waters of east equatorial Pacific sediments: Indicators of seawater advection through oceanic crust and sediments. In: Pisias, NG; Mayer, LA; Janecek, TR; Palmer-Julson, A; van Andel, TH (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 138, 813-819, https://doi.org/10.2973/odp.proc.sr.138.156.1995
    Publication Date: 2020-01-18
    Description: Pore-water samples from the equatorial sedimentary bulge area show reversals in depth profiles of 87Sr/86Sr ratios at the sediment/basement interface. Results of this work support inferences made from previous pore-water data (from DSDP drilling in the area) that large-scale horizontal advection of seawater has occurred through the basement underlying the thick sedimentary sequence in this region. The area of apparent advection includes the eastern part of the equatorial high-productivity zone and part of the Guatemala Basin. We attempted to find links between the observed near-basement reversals in pore-water chemistry and sedimentary thickness, age, and topography of the area. Most of the sites that show horizontal advection have disturbed basement topography or outcrops within 10 to 20 km, suggesting that the cooling effects of outcrops may extend for at least 20 km horizontally. Heat-flow data from the area were compared to determine whether sites showing near-bottom chemistry reversals were consistent with areas of low conductive heat flow. This was generally true for the area of the sedimentary bulge and Guatemala Basin. Not enough pore-water data from the Nazca Plate were available to establish any reliable systematics. Because the high-productivity area is well-sealed from hydrothermal circulation, the missing heat must be lost by horizontal advective heat transport. From profiles of strontium isotopes and other elements that show departure from seawater values with increasing depth in the sediments, but return to seawater values near the basement, it appears that water flows relatively freely through much of the oceanic crust, even when sealed by considerable sedimentary cover.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 9
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    PANGAEA
    In:  Supplement to: Himmler, Tobias; Haley, Brian A; Torres, Marta E; Klinkhammer, Gary P; Bohrmann, Gerhard; Peckmann, Jörn Ludwig (2013): Rare earth element geochemistry in cold-seep pore waters of Hydrate Ridge, northeast Pacific Ocean. Geo-Marine Letters, 33(5), 369-379, https://doi.org/10.1007/s00367-013-0334-2
    Publication Date: 2020-01-18
    Description: The concentrations of rare earth elements (REEs), sulphate, hydrogen sulphide, total alkalinity, calcium, magnesium and phosphate were measured in shallow (〈12 cm below seafloor) pore waters from cold-seep sediments on the northern and southern summits of Hydrate Ridge, offshore Oregon. Downward-decreasing sulphate and coevally increasing sulphide concentrations reveal sulphate reductionas dominant early diagenetic process from ~2 cm depth downwards. A strong increase of total dissolved REE concentrations is evident immediately below the sediment-water interface, which can be related to early diagenetic release of REEs into pore water resulting from the remineralization of particulate organic matter. The highest pore water REE concentrations were measured close to the sediment-water interface at ~2 cm depth. Distinct shale normalized REE patterns point to particulate organic matter and iron oxides as main REE sources in the upper ~2-cm depth interval. In general, the pore waters have shalenormalized patterns reflecting heavy REE (HREE) enrichment, which suggests preferential complexation of HREEs with carbonate ions. Below ~2 cm depth, a downward decrease in REE correlates with a decrease in pore water calcium concentrations. At this depth, the anaerobic oxidation of methane (AOM) coupled to sulphate reduction increases carbonate alkalinity through the production of bicarbonate, which results in the precipitation of carbonate minerals. It seems therefore likely that the REEs and calcium are consumed during vast AOM-induced precipitation of carbonate in shallow Hydrate Ridge sediments. The analysis of pore waters from Hydrate Ridge shed new light on early diagenetic processes at cold seeps, corroborating the great potential of REEs to identify geochemical processes and to constrain environmental conditions.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 10
    Publication Date: 2020-01-18
    Type: Dataset
    Format: text/tab-separated-values, 410 data points
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