Paleomagnetic of ODP Leg 133 holes

Paleomagnetic and rock-magnetic analyses from discrete samples of carbonate sites on the Queensland Plateau were used to determine magnetic polarity reversal stratigraphy and the nature of magnetization in these sediments. Magnetic polarity zones were correlated with the geomagnetic polarity time scale in the upper portions of cores at Sites 812 through 814, usually back to a late Pliocene age. Loss of reliable directional data was coincidental with a major decrease in magnetic intensity, below which, no stable polarity zones could be identified. The intensity reduction is either an in-situ alteration of magnetic grains, or an input signal representing progressive increase in the magnetic component of Queensland Plateau sediments. Although not conclusive at this point, the geochemical conditions and differing age of intensity reduction support the former hypothesis. Rock-magnetic analysis of carbonate sediments suggests that ultrafine-grained magnetite or maghemite crystals is an important carrier of remanence and may be biogenic in origin. Application of a recently calibrated anhysteretic remanent magnetization test to assess configuration of single-domain crystal within a natural matrix indicates that cementation (ooze-chalk-limestone) may be important in post-depositional changes affecting magnetostatic grain interaction.

Geochemistry data from the Toupugol volcanogenic complex

A large fragment of a paleovolcano of Silurian to Early Devonian age was discovered in the Voikar volcanic belt suggesting an ensimatic island are as its geodynamic environment. Formationally, the rocks under study are comparable to Pleistocene island arc volcanites and their paleo-analogues. The volcanites of the Toupugol complex underwent strong hydrothermal-metasomatic alteration: propylites, acid metasomatic rocks and quartz-carbonate veins, which must have resulted from hydrothermal-metasomatic alteration of andesitoids. Both volcanites and apovolcanic hydrothermal rocks in Toupugol were found to host noble metal mineralisation. It is found in close association with sulphides, particularly pyrite. Free gold was discovered in all investigated volcanites and hydrothermal rocks and is characterised by low mercury content and an unusual set of microimpurities (Pt, Pd, Cu, Fe, S) suggesting its links to the mantle substrate.

Chemical composition of phosphorite nodules off Peru

Phosphorite nodules collected during Cruise 8 of R/V Dmitry Mendeleev off the Peruvian coast are represented by three lithologic types: friable, compacted, and solid. As the nodules are progressively compacted, contents of phosphate components increase and of non-phosphate components decrease. Isotope composition of uranium in the friable nodules is the same as in ocean water, and diatoms contained in the nodules are represented by recent species indicating Late Quaternary age of the nodules.

(Table 1) List of samples with carbonate mineralogy, stable isotope, and accessory-mineral information

Petrographic and stable-isotope (d13C, d18O) patterns of carbonates from the Logatchev Hydrothermal Field (LHF), the Gakkel Ridge (GR), and a Late Devonian outcrop from the Frankenwald (Germany) were compared in an attempt to understand the genesis of carbonate minerals in marine volcanic rocks. Specifically, were the carbonate samples from modern sea floor settings and the Devonian analog of hydrothermal origin, low-temperature abiogenic origin (as inferred for aragonite in serpentinites from elsewhere on the Mid-Atlantic Ridge), or biogenic origin? Aragonite is the most abundant carbonate mineral in serpentinites from the two modern spreading ridges and occurs within massive sulfides of the LHF. The precipitation and preservation of aragonite suggests high Mg2+ and sulfate concentrations in fluids. Values of d18OPDB as high as +5.3 per mill for serpentinite-hosted aragonite and as high as +4.2 per mill for sulfide-hosted aragonite are consistent with precipitation from cold seawater. Most of the corresponding d13C values indicate a marine carbon source, whereas d13C values for sulfide-hosted aragonite as high as +3.6 per mill may reflect residual carbon dioxide in the zone of methanogenesis. Calcite veins from the LHF, by contrast, have low d18OPDB (-20.0 per mill to -16.1 per mill) and d13C values (-5.8 per mill to -4.5 per mill), indicative of precipitation from hydrothermal solutions (~129°-186°C) dominated by magmatic CO2. Calcite formation was probably favored by fluid rock interactions at elevated temperatures, which tend to remove solutes that inhibit calcite precipitation in seawater (Mg2+ and sulfate). Devonian Frankenwald calcites show low d18O values, reflecting diagenetic and metamorphic overprinting. Values of d13C around 0 per mill for basalt-hosted calcite indicate seawater-derived inorganic carbon, whereas d13C values for serpentinite-hosted calcite agree with mantle-derived CO2 (for values as low as -6 per mill) with a contribution of amagmatic carbon (for values as low as -8.6 per mill), presumably methane. Secondary mineral phases from the LHF for which a biogenic origin appears feasible include dolomite dumbbells, clotted carbonate, and a network of iron- and silica-rich filaments.

Pollen profile from sediment core Höllerer See

(expanded by Eberhard Grüger, Göttingen) The site "Höllerer See" is a lake in the northern foreland of the Alps, about 30 km north of the city of Salzburg/Austria, situated in the south-western part of Oberösterreich/Austria. A 2 m long piston core from this locality, consisting entirely of calcareous gyttja, was studied by pollen analysis. The three lowermost samples (1.98, 1.95 and 1.92 m) were deposited during the Preboreal when Pinus and Betula were still the dominating forest trees. High pollen values of thermophilous woody species (mainly Corylus and Quercus, but also Ulmus, Tilia, Fraxinus) prove the Boreal age of the next younger sample (1.91 m). The following two pollen spectra attest that Alnus (1.89 m) and - later (1.88 m) - Fagus had become important members of the local (Alnus) and the regional (Fagus) vegetation. From this level up to the top of the profile these two tree taxa contribute - together with Betula - always 50 to 80 % to the arboreal pollen sum. The upper 1.89 m of sediment of the Höllerer See core evidently date from the Subboreal and the Subatlantic. As Preboreal sediment was stated at the base of the profile it must be concluded that most of the Boreal and the Atlantic is - for whatever reason - not represented by sediment in this core. As no radiocarbon dates are available age estimates of the distinguished pollen zones can be achieved only by correlating major changes of the former vegetation with historical events which probably influenced the then contemporary vegetation. The pollen grains of the Triticum and Hordeum type found in samples of zone 2.1 might indicate the growing of cereals in the region during the Late Bronze Age. The first pollen grains of Secale date from the boundary Hallstatt/Latène Age (zone 2.2). The cereal curves become continuous in Bavarian times (Bajuwarenzeit, Middle Ages, zone 3.3). The Plantago laceolata curve, continuous since 1.7 m depth (zone 2.1), points to animal breeding since the Early Subatlantic (Hallstattzeit). This curve reaches its absolute maximum in Roman time (zone 3.1). Roman time forest clearance caused a drastic decrease of tree pollen curves (start of zone 3.1). Values of anthropogenic indicators as high as in zone 3.1 are found again - after a distinct decrease in zone 3.2 - not till the Bavarians settled in the region (6th century). Maximal Fagus values and the simultaneous total lack of anthropogenic indicators mark the Migration Period (zone 3.2). The Younger Subatlantic (zone 4) is characterized by a decrease of deciduous forests due to medieval forest clearance. At the same time the conifers Pinus and Picea gained in importance. The lake was probably used for retting hemp in Medieval times. The distinction of the pollen grains of Cannabis and Humulus might not be certain in all cases. It is known that hemp as well as hop was cultivated in the study area. Markers were added to the samples at the beginning of pollen preparation (13500 Lycopodium spores, sample volume 0.5 cm**3) and counted together with the pollen grains. Therefore pollen concentrations can be calculated: Concentration = C * F / V (with C = number of grains of a particular pollen type, V = volume of the untreated pollen sample, F = marker added/marker counted). F ranges from 39 to 1688. Factors that large are not suited to produce reliably interpretable pollen concentrations. Consequently no use was made of the pollen concentrations in this thesis, although a concentration diagram is added.

(Table 3) Textural and bulk mineralogy of Pliocene and Pleistocene sediments from ODP Hole 161-976B

The Pliocene and Pleistocene deposits recovered at Site 976 from the northwestern Alboran Sea at the Málaga base-of-slope include five main sedimentary facies: hemipelagic, turbidite, homogeneous gravity-flow, contourite, and debris-flow facies. The thickness and vertical distribution of these facies into lithostratigraphic Units I, II, and III show that the turbidites and hemipelagic facies are the dominant associations. The Pliocene and Pleistocene depositional history has been divided into three sedimentary stages: Stage I of early Pliocene age, in which hemipelagic and low-energy turbidites were the dominant processes; Stage II of early Pleistocene/late Pliocene age, in which the dominant processes were the turbidity currents interrupted by short episodes of other gravity flows (debris-flows and homogeneous gravity-flow facies) and bottom currents; and Stage III of Pleistocene age, in which both hemipelagic and low-energy gravity-flow processes occurred. The sedimentation during these three stages was controlled mainly by sea-level changes and also by the sediment supply that caused rapid terrigenous sedimentation variations from a proximal source represented by the Fuengirola Canyon.

Chronostratigraphic summary and raw counts of selected dinoflagellate cysts and architarch taxa of ODP Hole 151-907A

A detailed dinoflagellate cyst investigation of the almost continuous Middle Miocene through Pliocene of Ocean Drilling Program Hole 907A in the Iceland Sea has been conducted at 100-kyr resolution. The investigated section is well constrained by magnetostratigraphy, providing for the first time an independent temporal control on a succession of northern high-latitude dinoflagellate cyst bioevents. Based on the highest/lowest occurrences (HO/LO) and highest common occurrence (HCO) of 20 dinoflagellate cyst taxa and one acritarch species, 26 bioevents have been defined and compared with those recorded at selected DSDP, ODP, and IODP sites from the North Atlantic and contiguous seas, and in outcrops and boreholes from the onshore and offshore eastern U.S.A., and the North Sea and Mediterranean basins. Comparisons reveal near-synchronous HOs of the dinoflagellate cysts Batiacasphaera micropapillata (3.8-3.4 Ma, mid-Pliocene) and Reticulatosphaera actinocoronata (4.8-4.2 Ma, Lower Pliocene) across the Nordic Seas and North Atlantic, highlighting their value on a supraregional scale. This probably applies also to Hystrichosphaeropsis obscura (upper Tortonian), when excluding ODP Hole 907A where its sporadic upper stratigraphic range presumably relates to cooling in the early Tortonian. Over a broader time span within the upper Tortonian, the HO of Operculodinium piaseckii likely also permits correlation across the Nordic Seas and North Atlantic, and the HO of Labyrinthodinium truncatum appears useful in the Labrador and Nordic Seas. Biostratigraphic markers useful for regional rather than supraregional correlation are the HOs of Batiacasphaera hirsuta (c. 8.4 Ma, upper Tortonian) and Unipontidinium aquaeductus (c. 13.6-13.9 Ma, upper Langhian), the HCO of the acritarch Decahedrella martinheadii (c. 6.7-6.3 Ma, Messinian), and possibly the LO of Cerebrocysta irregulare sp. nov. (c. 13.8 Ma, uppermost Langhian) across the Nordic Seas. Since Habibacysta tectata, B. micropapillata, R. actinocoronata and D. martinheadii have been observed in the Arctic Ocean, they are potentially useful for high latitude correlations in the polar domain. The LOs of Habibacysta tectata and Unipontidinium aquaeductus suggest a mid- to late Langhian age (15.1-13.7 Ma) for deposits at the base of Hole 907A, thus providing new constraints on the age of basalts at the base of ODP Hole 907A. The stratigraphically important dinoflagellate cysts Cerebrocysta irregulare sp. nov., and Impagidinium elongatum sp. nov. are formally described.

(Table 1) 10 Beryllium and CaCO3 at DSDP Holes 86-576B, 86-576, and 86-578

Extension of the 10Be geochronology for deep-sea sediments beyond the limit of late Pliocene age found in published works has been attempted. The results obtained on sediments from Deep Sea Drilling Project (DSDP) Sites 576 and 578 of Leg 86 suggest the feasibility of dating sediments as old as 12 to 15 m.y. At both sites, there have been large changes in sedimentation rate, with the Pleistocene sediments accumulating several times faster than those of the Pliocene, which in turn were deposited several times more rapidly than the late Miocene sediments. The Pleistocene-Pliocene section is considerably thicker in Hole 578 than in Hole 576B: the respective depths for the 7 m.y. time boundary in the two holes are about 125 and about 25 m. These 10Be-based age estimates are in agreement with the paleomagnetic stratigraphies established for the two sites. The suggested enhancement in the oceanic deposition of 10Be before 7 to 9 m.y. ago, as noticed in manganese crusts, has found tentative support from the present sedimentary records. A preliminary search for 10Be production variation during a geomagnetic field reversal has been conducted. In Hole 578, an enhanced 10Be concentration is found in a sample close to the Brunhes/Matuyama reversal boundary. More detailed and systematic measurements are required to confirm this observation, which bears on the detailed behavior of the geomagnetic field during the reversal.

Iodine ages of pore water at Hydrate Ridge, Cascadian continental margin

Hydrate Ridge off the coast of Oregon, USA, is a prime example for gas hydrate occurrences in active margin settings. It is part of the Cascadia Margin and was the focus of Ocean Drilling Program (ODP) Leg 204, which successfully recovered fluids from nine sites from the southern part of the ridge. Iodide concentrations in pore fluids associated with gas hydrates are strongly enhanced, by factors up to 5000 compared to seawater, which allows the use of this biophilic element as tracer for organic source regions. We applied the cosmogenic isotope 129I (T1/2=15.7 Ma) system to determine the age of the organic source formation responsible for the iodide enrichment. In all sites at ODP Leg 204, 129I/I ratios were found to decrease with depth to values around 250x10**-15, corresponding to minimum ages of 40 Ma, but in several sites, maxima in the 129I/I ratios point to the local addition of young iodide. The results indicate that a large amount of iodide was derived from deep accreted sediments of Eocene age, and that additional source regions provide iodide of Late Miocene age. The presence of old iodide in the pore waters suggests that fluid pathways are open to allow transport over large distances into the gas hydrate fields. The strong correlation between iodide and methane in hydrate fields coupled with the similarity in transport parameters in aqueous solutions suggests that a large fraction of methane in gas hydrates also has old sources and is transported into the present locations from source regions of Eocene age.

(Table 1) Stratigraphic distribution and abundances of Cretaceous radiolarians from ODP Holes 130-803D and 130-807C

Among the five sites drilled during Ocean Drilling Program Leg 130, two deep holes (8O3D and 807C) penetrated Cretaceous sediments overlying the basaltic pillows, flows, and possibly basement rocks. Abundant, poorly preserved radiolarians with limited diversity were recovered from a few horizons within the sediments proximal to the basalt. At Site 803, three thin layers of radiolarites interbedded with claystone and clayey siltstone yielded radiolarian assemblages of late Albian age. At Site 807, several layers of radiolarian siltstones were recovered proximal to the basalt. Among them the most significant radiolarian assemblage is an Aptian fauna, located approximately 7 m above the basaltic flows. The Aptian radiolarian age for Site 807 is at least in accord with those suggested by planktonic foraminifer and paleomagnetic evidence. These Cretaceous radiolarians are the oldest assemblages recorded from the Ontong Java Plateau region.