skip to main content

Title: Data report: X-ray fluorescence core scanning of IODP Site U1474 sediments, Natal Valley, Southwest Indian Ocean, Expedition 361
X-ray fluorescence (XRF) core scanning was conducted on core sections from International Ocean Discovery Program Site U1474, located in the Natal Valley off the coast of South Africa. The data were collected at 2 mm resolution along the 255 m length of the splice, but this setting resulted in noisy data. This problem was addressed by applying a 10 point running sum on the XRF data prior to converting peak area to element intensities. This effectively integrates 10 measurements into 1, representing an average over 2 cm resolution, and significantly improves noise in the data. With 25 calibration samples, whose element concentrations were derived using inductively coupled plasma–optical emission spectrometry, the XRF measurements were converted to concentrations using a univariate log-ratio calibration method. The resulting concentrations of terrigenously derived major elements (Al, Si, K, Ti, and Fe) are anticorrelated with Ca concentrations, indicating the main control on sediment chemistry is the variable proportion of terrigenous to in situ produced carbonate material.
; ; ; ; ; ; ;
Award ID(s):
Publication Date:
Journal Name:
Proceedings of the International Ocean Discovery Program
Sponsoring Org:
National Science Foundation
More Like this
  1. Bulk sediment chemistry was measured at 2 cm resolution along cores from International Ocean Discovery Program (IODP) Site U1457 using the X-ray fluorescence (XRF) core scanner at the IODP Gulf Coast Repository. The Pleistocene splice section assembled from Holes U1457A and U1457B was scanned in its entirety, and nearly continuous sediment bulk chemistry profiles were constructed to a depth of 125 m core composite depth below seafloor (CCSF). Some sections of Hole U1457C were also scanned: (1) an upper Miocene hemipelagic section and (2) a 30 m lower Paleocene section directly overlying basalt. In the Pleistocene spliced sections, 2 cm spacing represents a sampling resolution of 150–300 y, whereas in the upper Miocene section this spacing represents about 500 y between samples. We report data and acquisition conditions for major and many minor elements. We find large variability in CaCO3 content in the Pleistocene section, from around 14 to 89 wt%. We used discrete shipboard CaCO3 measurements to calibrate the XRF Ca data. CaCO3 has cyclic variability and correlates with light sediment colors. Variation in aluminosilicate elements is largely caused by changes in dilution by CaCO3. The lower part of the spliced section, presumably representing distal Indus Fan deposits, hasmore »a distinctive but more uniform composition than the upper part.« less
  2. Abstract
    Site description. This data package consists of data obtained from sampling surface soil (the 0-7.6 cm depth profile) in black mangrove (Avicennia germinans) dominated forest and black needlerush (Juncus roemerianus) saltmarsh along the Gulf of Mexico coastline in peninsular west-central Florida, USA. This location has a subtropical climate with mean daily temperatures ranging from 15.4 °C in January to 27.8 °C in August, and annual precipitation of 1336 mm. Precipitation falls as rain primarily between June and September. Tides are semi-diurnal, with 0.57 m median amplitudes during the year preceding sampling (U.S. NOAA National Ocean Service, Clearwater Beach, Florida, station 8726724). Sea-level rise is 4.0 ± 0.6 mm per year (1973-2020 trend, mean ± 95 % confidence interval, NOAA NOS Clearwater Beach station). The A. germinans mangrove zone is either adjacent to water or fringed on the seaward side by a narrow band of red mangrove (Rhizophora mangle). A near-monoculture of J. roemerianus is often adjacent to and immediately landward of the A. germinans zone. The transition from the mangrove to the J. roemerianus zone is variable in our study area. An abrupt edge between closed-canopy mangrove and J. roemerianus monoculture may extend for up to several hundred metersMore>>
  3. Abstract. Coherent variation in CaCO3 burial is a feature ofthe Cenozoic eastern equatorial Pacific. Nevertheless, there has been along-standing ambiguity in whether changes in CaCO3 dissolution or changesin equatorial primary production might cause the variability. Sinceproductivity and dissolution leave distinctive regional signals, a regionalsynthesis of data using updated age models and high-resolution stratigraphiccorrelation is an important constraint to distinguish between dissolutionand production as factors that cause low CaCO3. Furthermore, the newchronostratigraphy is an important foundation for future paleoceanographicstudies. The ability to distinguish between primary production anddissolution is also important to establish a regional carbonate compensationdepth (CCD). We report late Miocene to Holocene time series of XRF-derived (X-rayfluorescence) bulk sediment composition and mass accumulation rates (MARs) from easternequatorial Pacific Integrated Ocean Drilling Program (IODP) sites U1335,U1337, and U1338 and Ocean Drilling Program (ODP) site 849, and we also report bulk-density-derived CaCO3 MARs at ODP sites 848, 850, and 851. We usephysical properties, XRF bulk chemical scans, and images along withavailable chronostratigraphy to intercorrelate records in depth space. Wethen apply a new equatorial Pacific age model to create correlated agerecords for the last 8 Myr with resolutions of 1–2 kyr. Large magnitudechanges in CaCO3 and bio-SiO2 (biogenic opal)more »MARs occurred withinthat time period but clay deposition has remained relatively constant,indicating that changes in Fe deposition from dust is only a secondaryfeedback to equatorial productivity. Because clay deposition is relativelyconstant, ratios of CaCO3 % or biogenic SiO2 % to clayemulate changes in biogenic MAR. We define five major Pliocene–Pleistocene low CaCO3 % (PPLC) intervalssince 5.3 Ma. Two were caused primarily by high bio-SiO2 burial thatdiluted CaCO3 (PPLC-2, 1685–2135 ka, and PPLC-5, 4465–4737 ka),while three were caused by enhanced dissolution of CaCO3 (PPLC-1, 51–402 ka, PPLC-3, 2248–2684 ka, and PPLC-4, 2915–4093 ka). Regional patterns ofCaCO3 % minima can distinguish between low CaCO3 caused by highdiatom bio-SiO2 dilution versus lows caused by high CaCO3dissolution. CaCO3 dissolution can be confirmed through scanning XRFmeasurements of Ba. High diatom production causes lowest CaCO3 %within the equatorial high productivity zone, while higher dissolutioncauses lowest CaCO3 percent at higher latitudes where CaCO3 production islower. The two diatom production intervals, PPLC-2 and PPLC-5, havedifferent geographic footprints from each other because of regional changesin eastern Pacific nutrient storage after the closure of the Central American Seaway.Because of the regional variability in carbonate production andsedimentation, the carbonate compensation depth (CCD) approach is onlyuseful to examine large changes in CaCO3 dissolution.

    « less
  4. Throughout the course of an organism’s life, the chemical signatures of environment, food consumption, and weather are recorded into their carbonate structures; these signatures can be directly linked to a time-resolved lifespan. Here we present trace element data from benthic foraminifera and tropical molluscs determined using an ESI NWR193UC excimer laser coupled with an Agilent 8900 triple quadrupole mass spectrometer in the MicroAnalytical Geochemistry and Isotope Characterization (MAGIC) Laboratory at the University of Maine. Benthic foraminifera are protists that live on the sea floor and produce calcite shells, progressively adding chambers. Changes in Mg/Ca in foraminifera are used as a proxy for ocean temperature. Laser ablation ICP-MS data for 18 trace elements were collected in individual growth chambers in foraminifera of the genus Uvigerina from the Bay of Plenty. Line scans were performed within thin (~10 µm) chamber walls using a spot size of 8 µm, beam energy density of 3 J/cm2, repetition rate of 12 Hz, and scan speeds of 2-3 µm/s. Concentrations were determined relative to the NIST610 glass. Ratios of Mg/Ca and other trace elements record the same range of values as those determined via bulk wet chemistry analysis of ~10 foraminifera for a given population, whichmore »suggests that LA-ICP-MS may be a viable alternative to wet chemistry. Trace element data were collected across shells of the warm-tropical mollusc species Chione subrugosa from the Ostra Base Camp area, Peru (78°37’22”W, 8°54’46”S). Previous studies of the area have suggested that a large climate transition occurred, transforming a warm water tropical bay into a desert surrounded by a coastal stand with cool waters. This area was occupied by humans at 6250-5450 radiocarbon years BP. This study examines Chione subrugosa, which were found in the living position at the fossilized Ostra Beach and are thought to have been the final living warm-tropical molluscs in the bay. Studies of modern molluscs have revealed that molluscs record massive climatic changes, such as El Niño, in their chemistry. Laser ablation provides a unique opportunity to examine chemical changes directly related to the changing coastal environment. Line scans transverse growth bands along the length of the shell, providing a high resolution record of daily variation in trace element chemistry over the lifespan of the mollusc. Eleven elements were analysed with a beam energy density of 2.4 J/cm2, repetition rate of 15 Hz, spot size of 5 x 25 µm, and a scan speed of 5 µm/s. Preliminary data suggest the preservation of yearly oscillations in trace elements, with high concentrations of La, Ce, U, and Pb during early shell growth. Continued study will examine catastrophic mollusc life events in an effort to link these with environmental climate changes over daily timescales.« less
  5. Abstract. The Global Ocean Data Analysis Project (GLODAP) is asynthesis effort providing regular compilations of surface-to-bottom oceanbiogeochemical data, with an emphasis on seawater inorganic carbon chemistryand related variables determined through chemical analysis of seawatersamples. GLODAPv2.2020 is an update of the previous version, GLODAPv2.2019.The major changes are data from 106 new cruises added, extension of timecoverage to 2019, and the inclusion of available (also for historicalcruises) discrete fugacity of CO2 (fCO2) values in the mergedproduct files. GLODAPv2.2020 now includes measurements from more than 1.2 million water samples from the global oceans collected on 946 cruises. Thedata for the 12 GLODAP core variables (salinity, oxygen, nitrate, silicate,phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12,CFC-113, and CCl4) have undergone extensive quality control with afocus on systematic evaluation of bias. The data are available in twoformats: (i) as submitted by the data originator but updated to WOCEexchange format and (ii) as a merged data product with adjustments appliedto minimize bias. These adjustments were derived by comparing the data fromthe 106 new cruises with the data from the 840 quality-controlled cruises ofthe GLODAPv2.2019 data product using crossover analysis. Comparisons toempirical algorithm estimates provided additional context for adjustmentdecisions; this is new to this version. The adjustments are intendedmore »toremove potential biases from errors related to measurement, calibration, anddata-handling practices without removing known or likely time trends orvariations in the variables evaluated. The compiled and adjusted dataproduct is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate,4 µmol kg−1 in dissolved inorganic carbon, 4 µmol kg−1in total alkalinity, 0.01–0.02 in pH (depending on region), and 5 % inthe halogenated transient tracers. The other variables included in thecompilation, such as isotopic tracers and discrete fCO2, were notsubjected to bias comparison or adjustments. The original data and their documentation and DOI codes are available at theOcean Carbon Data System of NOAA NCEI(, lastaccess: 20 June 2020). This site also provides access to the merged dataproduct, which is provided as a single global file and as four regional ones– the Arctic, Atlantic, Indian, and Pacific oceans –under (Olsen et al., 2020). Thesebias-adjusted product files also include significant ancillary andapproximated data. These were obtained by interpolation of, or calculationfrom, measured data. This living data update documents the GLODAPv2.2020methods and provides a broad overview of the secondary quality controlprocedures and results.« less