Chemistry of magmatic samples of ODP Holes 134-832B and 134-833B

New petrographic and compositional data were reported for 143 samples of core recovered from Sites 832 and 833 during Ocean Drilling Program (ODP) Leg 134. Site 832 is located in the center and Site 833 is on the eastern edge of the North Aoba Basin, in the central part of the New Hebrides Island Arc. This basin is bounded on the east (Espiritu Santo and Malakula islands) and west (Pentecost and Maewo islands) by uplifted volcano-sedimentary ridges associated with collision of the d'Entrecasteaux Zone west of the arc. The currently active Central Belt volcanic front extends through the center of this basin and includes the shield volcanoes of Aoba, Ambrym, and Santa Maria islands. The oldest rocks recovered by drilling are the lithostratigraphic Unit VII Middle Miocene volcanic breccias in Hole 832B. Lava clasts are basaltic to andesitic, and the dominant phenocryst assemblage is plagioclase + augite + orthopyroxene + olivine. These clasts characteristically contain orthopyroxene, and show a low to medium K calc-alkaline differentiation trend. They are tentatively correlated with poorly documented Miocene calc-alkaline lavas and intrusives on adjacent Espiritu Santo Island, although this correlation demands that the measured K-Ar of 5.66 Ma for one clast is too young, due to alteration and Ar loss. Lava clasts in the Hole 832B Pliocene-Pleistocene sequence are mainly ankaramite or augite-rich basalt and basaltic andesite; two of the most evolved andesites have hornblende phenocrysts. These lavas vary from medium- to high-K compositions and are derived from a spectrum of parental magmas for which their LILE and HFSE contents show a broad inverse correlation with SiO2 contents. We hypothesize that this spectrum results from partial melting of an essentially similar mantle source, with the low-SiO2 high HFSE melts derived by lower degrees of partial melting probably at higher pressures than the high SiO2, low HFSE magmas. This same spectrum of compositions occurs on the adjacent Central Chain volcanoes of Aoba and Santa Maria, although the relatively high-HFSE series is known only from Aoba. Late Pliocene to Pleistocene lava breccias in Hole 833B contain volcanic clasts including ankaramite and augite + olivine + plagioclase-phyric basalt and rare hornblende andesite. These clasts are low-K compositions with flat REE patterns and have geochemical affinities quite different from those recovered from the central part of the basin (Hole 832B). Compositionally very similar lavas occur on Merelava volcano, 80 km north of Site 833, which sits on the edge of the juvenile Northern (Jean Charcot) Trough backarc basin that has been rifting the northern part of the New Hebrides Island Arc since 2-3 Ma. The basal sedimentary rocks in Hole 833B are intruded by a series of Middle Pliocene plagioclase + augite +/- olivine-phyric sills with characteristically high-K evolved basalt to andesite compositions, transitional to shoshonite. These are compositionally correlated with, though ~3 m.y. older than, the high-HFSE series described from Aoba. The calc-alkaline clasts in Unit VII of Hole 832B, correlated with similar lavas of Espiritu Santo Island further west, presumably were erupted before subduction polarity reversal perhaps 6-10 Ma. All other samples are younger than subduction reversal and were generated above the currently subduction slab. The preponderance in the North Aoba Basin and adjacent Central Chain islands of relatively high-K basaltic samples, some with transitional alkaline compositions, may reflect a response to collision of the d'Entrecasteaux Zone with the arc some 2-4 Ma. This may have modified the thermal structure of the subduction zone, driving magma generation processes to deeper levels than are present normally along the reminder of the New Hebrides Island Arc.

Non-isoprenoidal intact polar lipids, isoprenoidal and non-isoprenoidal core lipids, isoprenoidal intact polar lipids of the Black Sea site GeoB15105 sampled during Meteor cruise M84/1 in February 2011

This PhD thesis focused on the analysis and application of microbial membrane lipids as biomarkers in marine sediments. Existing protocols for lipid extraction from marine sediments and biomass were modified. In addition, recent protocols based on high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS) as well as state-of-the-art mass spectrometric analysis by quadrupole time-of-flight (MSqTOF) and the triple quadrupole (MSQQQ) mass spectrometer were used to investigate matrix effects and evaluate the reliability of quantitative analysis in marine environmental samples. The improved lipid extraction and quantification were used to analyze Black Sea water column and sediments samples to a depth of 8 meters from site GeoB 15105 taken during cruise M84/1 (DARCSEAS) with R/V Meteor to apply lipid analysis in benthic bio systems. With this component specific differentiation between planktonic and benthic lipid signature we assessed possible lipid sources. Here, this high detail lipid fingerprinting allowed us to observe changes in the head group and lipid core structures of the intact polar lipids according to the geochemical zonation.

Age determination of ODP Leg 120 samples

Conventional K-Ar and 40Ar/39Ar analyses on whole-rock samples are reported for basaltic samples retrieved on the Central and Southern Kerguelen plateaus during Ocean Drilling Program Leg 120. Sites 747, 749, and 750 recovered basalts from the plateau basement, whereas Site 748 drilled a lava flow interbedded with sediments of probable Albian age. The freshest core basalts from the basement yielded dates falling in the 110-100 m.y. interval. Sample 120-749C-15R-3 (26-31 cm) gave conventional K-Ar, total fusion, and plateau 40Ar/39Ar ages that are closely concordant: 111.5 ± 3.2 m.y., 109.9 ± 1.2 m.y., and 109.6 ± 0.7 m.y., respectively. Sample 120-750B-15R-5 (54-60 cm), when taking into account the analytical uncertainties, yields conventional K-Ar and 40Ar/39Ar plateau ages that can be considered similar: 101.2 ± 7.5 and 118.2 ± 5 m.y., respectively. Inspection of the 39Ar/40Ar vs. 36Ar/40Ar diagram does not reveal the occurrence of an initial argon component of radiogenic composition in the two samples. Accordingly, our results suggest that the formation of the basement of the Central Kerguelen Plateau was closed at 110 m.y.. Furthermore, these results are in agreement with a K-Ar age of 114 ± 1 m.y. mentioned in the literature for a basalt dredged in the 77°E Graben. The still scant amount of data indicates that the outpourings of the Central Kerguelen Plateau correspond rather well with widespread continental magmatism in Gondwanaland that is believed to mark the incipient opening of the eastern Indian Ocean. This implies a huge head for the mantle plume at the source of these liquids. Nevertheless, on land and at sea the exact duration of magmatism remains unknown. Therefore, a catastrophic pattern similar to that currently invoked for the Deccan Traps at the end of the Cretaceous, though possible, is not yet required by present geochronologic data.

Geochemistry measured on sediment core GeoB12309-5

Laminated sediment records from the oxygen minimum zone in the Arabian Sea offer unique ultrahigh-resolution archives for deciphering climate variability in the Arabian Sea region. Although numerous analytical techniques are available it has become increasingly popular during the past decade to analyze relative variations of sediment cores' chemical signature by non-destructive X-ray fluorescence (XRF) core scanning. We carefully selected an approximately 5 m long sediment core from the northern Arabian Sea (GeoB12309-5: 24°52.3' N; 62°59.9' E, 956 m water depth) for a detailed, comparative study of high-resolution techniques, namely non-destructive XRF core scanning (0.8 mm resolution) and ICP-MS/OES analysis on carefully selected, discrete samples (1 mm resolution). The aim of our study was to more precisely define suitable chemical elements that can be accurately analyzed and to determine which elemental ratios can be interpretated down to sub-millimeter-scale resolutions. Applying the Student's t-test our results show significantly correlating (1% significance level) elemental patterns for all S, Ca, Fe, Zr, Rb, and Sr, as well as the K/Ca, Fe/Ti and Ti/Al ratios that are all related to distinct lithological changes. After careful consideration of all errors for the ICP analysis we further provide respective factors of XRF Core Scanner software error's underestimation by applying Chi-square-tests, which is especially relevant for elements with high count rates. As demonstrated by these new, ultra-high resolution data core scanning has major advantages (high-speed, low costs, few sample preparation steps) and represents an increasingly required alternative over the time consuming, expensive, elaborative, and destructive wet chemical analyses (e.g., by ICP-MS/OES after acid digestions), and meanwhile also provides high-quality data in unprecedented resolution.

Chemical composition of sediment core GeoB12309-5 from the northern Arabian Sea, its pore water profile and age depth relationship as well as CTD data obtained during cruise M74/3

The Arabian Sea off the Pakistan continental margin is characterized by one of the world's largest oxygen minimum zones (OMZ). The lithology and geochemistry of a 5.3 m long gravity core retrieved from the lower boundary of the modern OMZ (956 m water depth) were used to identify late Holocene changes in oceanographic conditions and the vertical extent of the OMZ. While the lower part of the core (535 - 465 cm, 5.04 - 4.45 cal kyr BP, Unit 3) is strongly bioturbated indicating oxic bottom water conditions, the upper part of the core (284 - 0 cm, 2.87 cal kyr BP to present, Unit 1) shows distinct and well-preserved lamination, suggesting anoxic bottom waters. The transitional interval from 465 to 284 cm (4.45 - 2.87 cal kyr BP, Unit 2) contains relicts of lamination which are in part intensely bioturbated. These fluctuations in bioturbation intensity suggest repetitive changes between anoxic and oxic/suboxic bottom-water conditions between 4.45 - 2.87 cal kyr BP. Barium excess (Baex) and total organic carbon (TOC) contents do not explain whether the increased TOC contents found in Unit 1 are the result of better preservation due to low BWO concentrations or if the decreased BWO concentration is a result of increased productivity. Changes in salinity and temperature of the outflowing water from the Red Sea during the Holocene influenced the water column stratification and probably affected the depth of the lower boundary of the OMZ in the northern Arabian Sea. Even if we cannot prove certain scenarios, we propose that the observed downward shift of the lower boundary of the OMZ was also impacted by a weakened Somali Current and a reduced transport of oxygen-rich Indian Central Water into the Arabian Sea, both as a response to decreased summer insolation and the continuous southward shift of the Intertropical Convergence Zone during the late Holocene.

Locations of geochemical samples and tephra from ODP Site 181-1123

Approximately one thousand sediment samples from ODP Site 1123 on the Chatham Rise, east of New Zealand, have been examined for inorganic elemental concentrations. ODP 1123 provides a record of sediment drift deposition under the Deep Western Boundary Current, the main inflow of deep water to the Pacific Ocean since the Early Oligocene, though a major hiatus spans the late Early Oligocene to the Early Miocene. Normalisation of the elemental concentrations by aluminium was used to allow for the effects of variable carbonate dilution. The elemental ratios were used as proxies for sediment composition and as palaeoceanographic indices. The samples were collected at a resolution designed to sample adequately any variation in elemental ratios at the scale of the Milankovitch orbital cycles. The sampled intervals span the Early Oligocene, Early Miocene, mid-Miocene and Late Pleistocene to Recent. Anomalous Si/Al, K/Al, Ti/Al values in the upper Pleistocene section, often associated with horizons of low carbonate, are attributed to tephras derived from North Island. Not all of the tephras detected geochemically had been detected visually in the cores. A total of 37 tephra events between 1.17 Ma BP and the present are recognised based on this and the shipboard investigations. The tephra events cluster at intervals of approximately 326 000 years (326 ka) perhaps due to variations in eruption frequency on North Island and/or to variations in the regional palaeowind intensity and direction. In the Late Pleistocene to Recent P/Al (inferred nutrient availability), percent calcium carbonate (%CaCO3) and Ba/Al (inferred productivity) varied regularly at a period of 40 000 years with these factors lagging minimum global ice volumes (interglacials). During the mid-Miocene CaCO3, Ba/Al, P/Al and Si/Al all gradually increased with %CaCO3 and P/Al showing regular 138 000-yr cyclicity and Ba/Al showing 44-ka cyclicity. Inferred productivity (Ba/Al) may have been rising in association with increasing nutrient availability (P/Al) at the same time as increased vigour of the Deep Western Boundary Current that was connected to a period of rapid ice-sheet growth in Antarctica. In the Early Miocene P/Al and Si/Al were much higher than subsequently and both %CaCO3 and P/Al exhibited 131 000-yr cycles. By far the highest nutrient levels and inferred productivity at this site apparently occurred during the Early Oligocene as revealed by long-term changes in P/Al and Si/Al. A progressive rise in K/Al, but stable Ti/Al from the Early Oligocene to the Recent probably indicates increased proportions of illite in the clay mineral fraction of the drift sediments caused by increased flux of debris from the Southern Alps.

Magnesium/calcium ratio of the foraminifera Oridorsalis umbonatus in surface sediment samples off Namibia

A laser ablation system connected to an inductively coupled plasma mass spectrometer was used to determine Mg/Ca ratios of the benthic foraminifera Oridorsalis umbonatus. A set of modern core top samples collected along a depth transect on the continental slope off Namibia (320-2300 m water depth; 2.9° to 10.4°C) was used to calibrate the Mg/Ca ratio against bottom water temperature. The resulting Mg/Ca-bottom water temperature relationship of O. umbonatus is described by the exponential equation Mg/Ca = 1.528*e**0.09*BWT. The temperature sensitivity of this equation is similar to previously published calibrations based on Cibicidoides species, suggesting that the Mg/Ca ratio of O. umbonatus is a valuable proxy for thermocline and deep water temperature.

Geochemistry of sediment core GeoB7920-2

The X-ray fluorescence (XRF) core scanner provides bulk-sediment chemistry data measured nondestructively at the split core sediment surface. Although this method is widely accepted, there is little known about the effects of physical properties such as density and water content on XRF core scanner data. Comparison of XRF scanner measurements from the sediment surface and dry powder samples of sediment core GeoB7920 indicates strongly reduced element intensities for the lighter elements Al and Si. We relate the lower element intensities of the measurements taken at the sediment surface to the amount of water in the sample volume analyzed by the XRF core scanner. The heavier elements K, Ca, Ti, and Fe remain relatively unaffected by the variation of any physical property within sediment core GeoB7920. Additionally, we successfully use the elemental intensity of Cl as a proxy for the seawater content in the sample volume analyzed by the XRF core scanner. This enables the establishment of a correction function for the elements Al and Si that corrects for the radiation absorption of the water content in sediment core GeoB7920 off Cape Blanc, NW Africa.

Planktonic foraminifera of sediment core MD01-2390

Sea-surface temperature (SST) estimates in the sediment core MD01-2390 based on planktonic foraminiferal species abundances using five different transfer function techniques suggest nearly unchanged or unusually higher temperatures in the tropical southern South China Sea (SCS) during the Last Glacial Maximum (LGM) relative to modern temperatures. These results are in contrast to substantial cooling of 2-5 °C inferred by geochemical (Uk'37, Mg/Ca ratios) and terrestrial proxies from the western tropical Pacific region. Using multivariate statistics we show that the glacial southern SCS harboured unique planktonic foraminiferal assemblages that have no modern analogs. Analyses of faunal variation through the core reveal that planktonic foraminiferal assemblages responded to temperature changes inferred from Mg/Ca data but that this signal is subdued by superimposed variations in the relative abundance of Pulleniatina obliquiloculata and Neogloboquadrina pachyderma (dextral). These species occur in glacial samples at proportions that are not observed in the calibration data set. The glacial high abundance of N. pachyderma (dextral) are interpreted to reflect a seasonal (winter) inflow of cold surface water from the northeast via the Bashi Strait due to the combined effects of an intensified winter monsoon, a southward shift of the polar front and the eastward migration of the Kuroshio Current. In contrast, processes controlling the high relative abundances of P. obliquiloculata during the LGM may be unique to the southern SCS. We propose a scenario involving a stronger (winter) mixing or enhanced upwelling due to an intensified winter monsoon that prevented shallow-dwelling, warm indicators to establish larger populations during the LGM. Our results indicate that a no-analog behaviour of planktonic foraminifera faunas is responsible for the warm glacial conditions in this part of the western Pacific warm pool as implied by foraminiferal transfer functions and that a more significant surface cooling in the region as implied by terrestrial and geochemical (Mg/Ca ratios; alkenone unsaturation index) marine proxies is a more likely scenario.

Age determination of sediment core MD07-3088

The Southern Ocean plays a prominent role in the Earth's climate and carbon cycle. Changes in the Southern Ocean circulation may have regulated the release of CO2 to the atmosphere from a deep-ocean reservoir during the last deglaciation. However, the path and exact timing of this deglacial CO2 release are still under debate. Here we present measurements of deglacial surface reservoir 14C age changes in the eastern Pacific sector of the Southern Ocean, obtained by 14C dating of tephra deposited over the marine and terrestrial regions. These results, along with records of foraminifera benthic-planktic 14C age and d13C difference, provide evidence for three periods of enhanced upwelling in the Southern Ocean during the last deglaciation, supporting the hypothesis that Southern Ocean upwelling contributed to the deglacial rise in atmospheric CO2. These independently dated marine records suggest synchronous changes in the Southern Ocean circulation and Antarctic climate during the last deglaciation.

Sedimentology on two core from the Bransfield Strait area

The raw material for these investigations are samples from marine (sub)surface sediments around the northern part of the Antarctic Peninsula. They had been sampled in the years 1981 to 1986 during several expeditions of the research vessels Meteor, Polarstern and Walther Herwig. 83 box core, gravity core and dredge samples from the area of the Bransfield Strait, the Powell Basin and the northern Weddell Sea have been examined for their grain-size distribution, their mineralogical and petrographical composition. Silt prevails and its clay proportions exceed 25% wt. in water depths greater than 2000 m. The granulometrical results reveal some typical sedimentation processes within the area of investigation. While turbiditic processes together with sediment input from melting icebergs control the sedimentation in the Weddell Sea, the South Orkney Island Plateau and the Powell Basin, the fine grained material from Bransfield Strait mainly relies on marine currents in the shelf area. In addition, the direct sediment input of coarse shelf sediments from the Bransfield Strait into the Powell Basin through submarine canyons could be proven. Variations in the grain-size composition with sediment depth are smalI. The mineral composition of the clay and fine silt fractions is quite uniform in all samples. There are (in decreasing order): illite, montmorillonite, chlorite, smectite, mixed-Iayers, as well as detrital quartz and feldspars. A petrographically based sediment stratigraphy can be established in using the considerable changes in the chlorite- and Ca-plagioclase portions in samples from Core 224. For this sedimentation area a mean sedimentation rate of 7 cm/1000 a is assumed. Remarkable changes in the portions of amorphous silica components - diatom skeletons and volcanic glass shards - appear all over the area of investigation. They contribute between 4-83 % to the clay and fine silt fraction. Several provinces according to the heavy mineral assemblages in the fine sand fraction can be distinguished: (i) a province remarkably influenced by minerals of volcanic origin south and north of the South Shetland Islands; (ii) a small strip with sediment dominated by plutonic material along the western coast of the Antarctic Peninsula and (iii) a sediment controlled by metamorphic minerals and rock fragments in the area of the Weddell Sea and Elephant Island. While taking the whole grain-size spectrum into account a more comprehensive interpretation can be given: the accessoric but distinct appearance of tourmaline, rutile and zircon in the heavy mineral assembly along the northwestern coast of the Antarctic Peninsula is in agreement with the occurrence of acid volcanic rock pieces in the coarse fraction of the ice load detritus in this region. In the vicinity of the South Shetland Islands chlorite appears in remarkable portions in the clay fraction in combination with leucoxene, sphene and olivine, and pumice as well as pyroclastic rocks in the medium and coarse grain fractions, respectively. Amphiboles and amphibole-schists are dominant on the South Orkney Island Plateau. In the sediments of the northwestern Weddell Sea the heavy mineral phases of red spinel, garnet, kyanite and sillimanite in connection with medium to highgrade metamorphic rocks especially granulitic gneisses, are more abundant. A good conformity between the ice rafted rock sampIes and the rocks in the island outcrops could be proven, especially in the vicinity of offshore islands nearby. On the continent enrichments of rock societies and groups appear in spacious outlines: acid effusive rocks in the west of the ice divide on the Antarctic Peninsula, clastic sedimentites at the tip of the Antarctic Peninsula and granoblastic gneisses in central and eastern Antarctica. Coarse grain detritus with more than 1 cm of diameter must have been rafted by icebergs. These rock fragments are classified as rock types, groups and societies. The spacial distribution of their statistically determined weight relations evidently shows the paths of the iceberg drift and in nexus with already known iceberg routes also point to the possible areas of provenance, provided that the density of sample locations and the number of rock pieces are sufficient.

Planktonic foraminifera in Core ML2_66, North Atlantic

Evolution of approaches and methods for reconstruction of paleoenvironmental conditions from microfossils contained in bottom sediments is assessed. Authors elaborated a new actualistic basis for such reconstructions, consisting of a database on contents of tests of planktonic foraminifers in the surface layer of Atlantic sediments and a package of mathematical tools for computer data processing. Structure of the database is described. It contains data on test contents for 29 species and varieties of planktonic foraminifers in 381 samples. A mathematical model designed for reconstructions is based on factor analysis and multidimensional spline interpolation. The model allows one to deduce Quaternary hydrological parameters (paleotemperature, paleosalinity) for standard hydrological levels down to depth of 250 m for the four seasons of the year. Reconstructions are illustrated by an example of a sedimentary core from the North Atlantic representing a period of 300 ky. During the next to last and the last maxima of continental glaciation (oxygen isotope stages 8, 6, 4, and 2), the subarctic water mass was spread here. Winter and summer surface water temperatures comprised 1-5° and 5-7°C, respectively. During interglacials and in Holocene the conditions were close to present ones: winter and summer surface water temperatures comprised 10-12 and 15-17°C, respectively. Vertical paleohydrological profiles compiled for peaks of climatostratigraphic intervals suggest that during cold intervals water stratification was stronger than during the warm ones. At depth 50 m seasonal salinity oscillations did not exceed 0.4 per mil and commonly salinity was minimum in winter and maximum in summer.