(Table 1) Planktonic foraminifer abundance and stable isotope ratios of a sediment core near Baddeckenstedt, north Germany

A refined sample processing technique using glacial acetic acid has been applied to Upper Cenomanian and Lower Turonian limestones from Baddeckenstedt (Lower Saxony) enabeling the first quantitative analysis of planktonic foraminiferal populations through the Stage boundary succession in northwestern Germany. Measurements of carbonate contents, organic carbon and stable carbon and oxygen isotopes were also reported. These data allow a correlation to be made of the Baddeckenstedt section with those at Misburg (basinal facies, northwestern Germany) and Dover (Plenus Marls, southern England). Significant maxima of the organic carbon content at Baddeckenstedt correspond to prominent black shale couplets at Misburg. The planktonic foraminiferal generic groups show at Baddeckenstedt similar fluctuations as reported from Dover. Their correlation reveals details of a complex paleoceanographic regime in the NW-German Basin during the Cenomanian/Turonian Oceanic Anoxic Event.

(Appendix 1) Age, Ge/Si ratio, aluminium and opal contents in ODP Sites 175-1081 and 175-1084

As a result of both culture and sediment core studies, the ratio of germanium (Ge) to silicon (Si) in diatom shells has been proposed as a proxy for monitoring whole-ocean changes in seawater Ge/Si, a ratio affected by changes in continental weathering. However, because of the difficulties of extracting and cleaning diatom frustules from deep-sea sediments, only samples from highly pure diatom oozes in the Antarctic region have been previously analyzed. Here we present data on diatom Ge/Si ratios, (Ge/Si)opal, for the time interval between 3.1 and 1.9 Ma from a mid-latitude, coastal upwelling area where significant terrigenous sediment input complicated the sample processing and analyses. In general, our (Ge/Si)opal values show the same decreasing trend after 2.6 Ma than previously measured in Antarctic sediments (Shemesh et al., 1989. Paleoceanography 4, 221-231), but with a noisier background that may reflect the local imprint of proximal continental input superimposed upon global changes in the ocean reservoir. The time of initiation of large-scale North Hemisphere glaciation at ~2.6 Ma is characterized by a declining pattern of diatom Ge/Si ratios, which could have resulted from a global increase in the input of riverine Si due to enhanced silica weathering and/or equatorward (northward) intrusions of subantarctic waters enriched in silica. High (Ge/Si)opal ratios are associated with high opal contents from the same sediment samples and with warm climate as indicated by depleted benthic foraminiferal d18O values from the North and Equatorial Atlantic. Cold periods signified by enriched benthic d18O values, on the contrary, are associated with lower (Ge/Si)opal ratios. We interpret diatom Ge/Si values to reflect the prevailing weathering state on the continents, with greater chemical weathering during warm and wet periods of the Pliocene and less during cooler and drier intervals.

Geochemistry of sediment core HE337/001-1, North Sea

Reactive iron (oxyhydr)oxide minerals preferentially undergo early diagenetic redox cycling which can result in the production of dissolved Fe(II), adsorption of Fe(II) onto particle surfaces, and the formation of authigenic Fe minerals. The partitioning of iron in sediments has traditionally been studied by applying sequential extractions that target operationally-defined iron phases. Here, we complement an existing sequential leaching method by developing a sample processing protocol for d56Fe analysis, which we subsequently use to study Fe phase-specific fractionation related to dissimilatory iron reduction in a modern marine sediment. Carbonate-Fe was extracted by acetate, easily reducible oxides (e.g. ferrihydrite and lepidocrocite) by hydroxylamine-HCl, reducible oxides (e.g. goethite and hematite) by dithionite-citrate, and magnetite by ammonium oxalate. Subsequently, the samples were repeatedly oxidized, heated and purified via Fe precipitation and column chromatography. The method was applied to surface sediments collected from the North Sea, south of the Island of Helgoland. The acetate-soluble fraction (targeting siderite and ankerite) showed a pronounced downcore d56Fe trend. This iron pool was most depleted in 56Fe close to the sediment-water interface, similar to trends observed for pore-water Fe(II). We interpret this pool as surface-reduced Fe(II), rather than siderite or ankerite, that was open to electron and atom exchange with the oxide surface. Common extractions using 0.5 M HCl or Na-dithionite alone may not resolve such trends, as they dissolve iron from isotopically distinct pools leading to a mixed signal. Na-dithionite leaching alone, for example, targets the sum of reducible Fe oxides that potentially differ in their isotopic fingerprint. Hence, the development of a sequential extraction Fe isotope protocol provides a new opportunity for detailed study of the behavior of iron in a wide-range of environmental settings.

Stable oxygen and carbon isotope ratios of foraminifera and test results after different sample cleaning procedures from ODP Leg 207 sediments

We report oxygen and carbon stable isotope analyses of foraminifers, primarily planktonic, sampled at low resolution in the Cretaceous and Paleogene sections from Sites 1257, 1258, and 1260. Data from two samples from Site 1259 are also reported. The very low resolution of the data only allows us to detect climate-driven isotopic events on the timescale of more than 500 k.y. A several million-year-long interval of overall increase in planktonic 18O is seen in the Cenomanian at Site 1260. Before and after this interval, foraminifers from Cenomanian and Turonian black shales have d18O values in the range -4.2 per mil to -5.0 per mil, suggestive of upper ocean temperatures higher than modern tropical values. The d18O values of upper ocean dwelling Paleogene planktonics exhibit a long-term increase from the early Eocene to the middle Eocene. During shipboard and postcruise processing, it proved difficult to extract well-preserved foraminifer tests from black shales by conventional techniques. Here, we report results of a test of procedures for cleaning foraminifers in Cretaceous organic-rich mudstone sediments using various combinations of soaking in bleach, Calgon/hydrogen peroxide, or Cascade, accompanied by drying, repeat soaking, or sonication. A procedure that used 100% bleach, no detergent, and no sonication yielded the largest number of clean, whole individual foraminifers with the shortest preparation time. We found no significant difference in d18O or d13C values among sets of multiple samples of the planktonic foraminifer Whiteinella baltica extracted following each cleaning procedure.