Geochemical analyses of secondary minerals from ODP Leg 115 basalts (Tables 1+2)

Basalts recovered along the Reunion hotspot track on Ocean Drilling Program (ODP) Leg 115 range in age from 34 Ma at Site 706 to 64 Ma at Site 707. They have undergone various degrees of secondary alteration. Within single holes the amount of alteration can vary from a few percent to near complete replacement of phenocrysts and groundmass by secondary minerals. Olivine appears to be the most susceptible to alteration and in some sections it is the only mineral altered. In other sections, olivine, pyroxene and plagioclase phenocrysts, and groundmass have been completely replaced by secondary minerals. Clays are the predominant form of secondary mineralization. In addition to replacing olivine, pyroxene, glass, and groundmass, clays have filled veins, vesicles, and voids. Minor amounts of calcite, zeolites, and K-feldspar were also detected. The clays that filled vesicles and veins often show color zonations of dark, opaque bands near the edges that grade into tan or green transparent regions in the centers of the veins. The electron microprobe was used to obtain chemical analyses of these veins as well as to characterize isolated clays that replaced specific minerals and filled voids and vesicles.

Tab. 1+2: Representative electron-microprobe analyses of minerals from Du Toit Nunataks

An example of cordierite-bearing gneiss that is part of a high-grade gneiss-migmatite sequence is described from the Hatch Plain in the Read Mountains of the Shackleton Range, Antarctica, for the first time. The cordierite-bearing rocks constitute the more melanosomic portions of the metatectic and migmatitic rocks that are associated with relict granulite facies rocks such as enderbitic granulite and enderbitic garnet granulite. The predominant mineral assemblage in the cordierite-bearing rocks is chemically homogeneous cordierite (XMg 0.61) and biotite (XMg 0.47), strongly zoned garnet (XMg 0.18-0.11), sillimanite, K-feldspar (Or81-94Ab5-18An0.6), plagioclase (An28), and quartz. Inclusions of sillimanite and biotite relics in both garnet and cordierite indicate that garnet and cordierite were produced by the coupled, discontinuous reaction biotite + sillimanite + quartz = cordierite + garnet + K-feldspar + H2O. Various garnet-biotite and garnet-cordierite geothermometers and sillimanite-quartz-plagioclase-garnet-cordierite geobarometers yield a continuous clockwise path in the P-T diagram. The P-T conditions for equilibrium between garnet core and cordierite and between garnet core and biotite during peak metamorphism and migmatization were estimated to be 690 °C at 5-6 kb. This was followed by cooling and unloading with continuously changing conditions down to 515 °C at 2-3 kb. This low-pressure re-equilibration correlates with the pressure conditions evaluated by SCHULZE (1989) for the widespread granitic gneisses of the Read Group in the Shackleton Range. The associated relict enderbitic granulites representing low-pressure type granulite (8 kb; 790 °C) are comparable to similar low-pressure granulites from the East Antarctic craton. They were either formed by under-accretion processes after collision (WELLS 1979, p. 217) or they are a product of remetamorphism at P-T conditions intermediate between granulite and amphibolite facies. A model of a multiple imbrication zone with crustal thickening (CUTHBERT et al. 1983) is discussed for the formation of the relict granulites of the central and eastern Read Mountains which show higher pressure conditions (8-12 kb, SCHULZE & OLESCH 1990), indicating a Proterozoic crustal thickness of at least 40 km.

1.2 Ma stacked benthic foraminiferal carbon isotope record

Pleistocene stable carbon isotope (d13C) records from surface and deep dwelling foraminifera in all major ocean basins show two distinct long-term carbon isotope fluctuations since 1.00 Ma. The first started around 1.00 Ma and was characterised by a 0.35 per mil decrease in d13C values until 0.90 Ma, followed by an increase of 0.60 per mil lasting until 0.50 Ma. The subsequent fluctuation started with a 0.40 per mil decrease between 0.50 and 0.25 Ma, followed by an increase of 0.30 per mil between 0.25 and 0.10 Ma. Here, we evaluate existing evidence and various hypotheses for these global Pleistocene d13C fluctuations and present an interpretation, where the fluctuations most likely resulted from concomitant changes in the burial fluxes of organic and inorganic carbon due to ventilation changes and/or changes in the production and export ratio. Our model indicates that to satisfy the long-term 'stability' of the Pleistocene lysocline, the ratio between the amounts of change in the organic and inorganic carbon burial fluxes would have to be close to a 1:1 ratio, as deviations from this ratio would lead to sizable variations in the depth of the lysocline. It is then apparent that the mid-Pleistocene climate transition, which, apart from the glacial cycles, represents the most fundamental change in the Pleistocene climate, was likely not associated with a fundamental change in atmospheric pCO2. While recognising that high frequency glacial/interglacial cycles are associated with relatively large (100 ppmv) changes in pCO2, our model scenario (with burial changes close to a 1:1 ratio) produces a maximum long-term variability of only 20 ppmv over the fluctuation between 1.00 and 0.50 Ma.

(Tables 1,2) Polar bear (Ursus maritimus), beluga whale (Delphinapterus leucas) and ringed seal (Pusa hispida) liver microsomal protein content and EROD activity

The present study assessed and compared the oxidative and reductive biotransformation of brominated flame retardants, including established polybrominated diphenyl ethers (PBDEs) and emerging decabromodiphenyl ethane (DBDPE) using an in vitro system based on liver microsomes from various arctic marine-feeding mammals: polar bear (Ursus maritimus), beluga whale (Delphinapterus leucas), and ringed seal (Pusa hispida), and in laboratory rat as a mammalian model species. Greater depletion of fully brominated BDE209 (14-25% of 30pmol) and DBDPE (44-74% of 90pmol) occurred in individuals from all species relative to depletion of lower brominated PBDEs (BDEs 99,100, and 154; 0-3% of 30pmol). No evidence of simply debrominated metabolites was observed. Investigation of phenolic metabolites in rat and polar bear revealed formation of two phenolic, likely multiply debrominated, DBDPE metabolites in polar bear and one phenolic BDE154 metabolite in polar bear and rat microsomes. For BDE209 and DBDPE, observed metabolite concentrations were low to nondetectable, despite substantial parent depletion. These findings suggested possible underestimation of the ecosystem burden of total-BDE209, as well as its transformation products, and a need for research to identify and characterize the persistence and toxicity of major BDE209 metabolites. Similar cause for concern may exist regarding DBDPE, given similarities of physicochemical and environmental behavior to BDE209, current evidence of biotransformation, and increasing use of DBDPE as a replacement for BDE209.

Age determination of sediment core HZM, lake Holzmar (Tables 1, 2)

AMS radiocarbon ages have been determined on terrestrial macrofossils selected from the annually laminated sediments of lake Holzmaar (Germany). The radiocarbon chronology of this lake covers the last 12.6 ka. Comparison of the radiocarbon dated varve chronology with tree ring data shows that an additional 878 years have to be added to the varve chronology. The corrected 14C varve chronology of Holzmaar reaches back to ca. 13.8 ka cal. BP and compares favourably with the results from Soppensee (Switzerland) (Hajdas et al., 1993, doi:10.1007/BF00209748). The corrected ages for the onset and the end of the Younger Dryas biozone are 11,940 cal. BP and 11,490 cal. BP, respectively. The ash layer of the Laacher See volcanic eruption is dated at 12,201 ± 224 cal. BP and the Ulmener Tephra layer is dated at 10,904 cal. BP.

(Tables 1-2) Heavy mineral composition and median grain size of sediments obtained near 'Rote Kliff' west of Sylt, North Sea

The interpretation of 19 bore cores from the sea floor west of Rote Kliff (Isle of Sylt, North-Frisian Islands) gave information about the thickness of Holocene sand and the sediments below it; especially regarding their resistance to erosion in the area seaward of the beach-barrier. At the Same time, additional knowledge was obtained about the development of Sylt.