Quantitative component analysis of the coarse fraction of surface sediments from the Persian Gulf

In the Persian Gulf and the Gulf of Oman marl forms the primary sediment cover, particularly on the Iranian side. A detailed quantitative description of the sediment components > 63 µ has been attempted in order to establish the regional distribution of the most important constituents as well as the criteria governing marl sedimentation in general. During the course of the analysis, the sand fraction from about 160 bottom-surface samples was split into 5 phi° fractions and 500 to 800 grains were counted in each individual fraction. The grains were cataloged in up to 40 grain type catagories. The gravel fraction was counted separately and the values calculated as weight percent. Basic for understanding the mode of formation of the marl sediment is the "rule" of independent availability of component groups. It states that the sedimentation of different component groups takes place independently, and that variation in the quantity of one component is independent of the presence or absence of other components. This means, for example, that different grain size spectrums are not necessarily developed through transport sorting. In the Persian Gulf they are more likely the result of differences in the amount of clay-rich fine sediment brought in to the restricted mouth areas of the Iranian rivers. These local increases in clayey sediment dilute the autochthonous, for the most part carbonate, coarse fraction. This also explains the frequent facies changes from carbonate to clayey marl. The main constituent groups of the coarse fraction are faecal pellets and lumps, the non carbonate mineral components, the Pleistocene relict sediment, the benthonic biogene components and the plankton. Faecal pellets and lumps are formed through grain size transformation of fine sediment. Higher percentages of these components can be correlated to large amounts of fine sediment and organic C. No discernable change takes place in carbonate minerals as a result of digestion and faecal pellet formation. The non-carbonate sand components originate from several unrelated sources and can be distinguished by their different grain size spectrum; as well as by other characteristics. The Iranian rivers supply the greatest amounts (well sorted fine sand). Their quantitative variations can be used to trace fine sediment transport directions. Similar mineral maxima in the sediment of the Gulf of Oman mark the path of the Persian Gulf outflow water. Far out from the coast, the basin bottoms in places contain abundant relict minerals (poorly sorted medium sand) and localized areas of reworked salt dome material (medium sand to gravel). Wind transport produces only a minimal "background value" of mineral components (very fine sand). Biogenic and non-biogenic relict sediments can be placed in separate component groups with the help of several petrographic criteria. Part of the relict sediment (well sorted fine sand) is allochthonous and was derived from the terrigenous sediment of river mouths. The main part (coarse, poorly sorted sediment), however, was derived from the late Pleistocene and forms a quasi-autochthonous cover over wide areas which receive little recent sedimentation. Bioturbation results in a mixing of the relict sediment with the overlying younger sediment. Resulting vertical sediment displacement of more than 2.5 m has been observed. This vertical mixing of relict sediment is also partially responsible for the present day grain size anomalies (coarse sediment in deep water) found in the Persian Gulf. The mainly aragonitic components forming the relict sediment show a finely subdivided facies pattern reflecting the paleogeography of carbonate tidal flats dating from the post Pleistocene transgression. Standstill periods are reflected at 110 -125m (shelf break), 64-61 m and 53-41 m (e.g. coare grained quartz and oolite concentrations), and at 25-30m. Comparing these depths to similar occurrences on other shelf regions (e. g. Timor Sea) leads to the conclusion that at this time minimal tectonic activity was taking place in the Persian Gulf. The Pleistocene climate, as evidenced by the absence of Iranian river sediment, was probably drier than the present day Persian Gulf climate. Foremost among the benthonic biogene components are the foraminifera and mollusks. When a ratio is set up between the two, it can be seen that each group is very sensitive to bottom type, i.e., the production of benthonic mollusca increases when a stable (hard) bottom is present whereas the foraminifera favour a soft bottom. In this way, regardless of the grain size, areas with high and low rates of recent sedimentation can be sharply defined. The almost complete absence of mollusks in water deeper than 200 to 300 m gives a rough sedimentologic water depth indicator. The sum of the benthonic foraminifera and mollusca was used as a relative constant reference value for the investigation of many other sediment components. The ratio between arenaceous foraminifera and those with carbonate shells shows a direct relationship to the amount of coarse grained material in the sediment as the frequence of arenaceous foraminifera depends heavily on the availability of sand grains. The nearness of "open" coasts (Iranian river mouths) is directly reflected in the high percentage of plant remains, and indirectly by the increased numbers of ostracods and vertebrates. Plant fragments do not reach their ultimate point of deposition in a free swimming state, but are transported along with the remainder of the terrigenous fine sediment. The echinoderms (mainly echinoids in the West Basin and ophiuroids in the Central Basin) attain their maximum development at the greatest depth reached by the action of the largest waves. This depth varies, depending on the exposure of the slope to the waves, between 12 to 14 and 30 to 35 m. Corals and bryozoans have proved to be good indicators of stable unchanging bottom conditions. Although bryozoans and alcyonarian spiculae are independent of water depth, scleractinians thrive only above 25 to 30 m. The beginning of recent reef growth (restricted by low winter temperatures) was seen only in one single area - on a shoal under 16 m of water. The coarse plankton fraction was studied primarily through the use of a plankton-benthos ratio. The increase in planktonic foraminifera with increasing water depth is here heavily masked by the "Adjacent sea effect" of the Persian Gulf: for the most part the foraminifera have drifted in from the Gulf of Oman. In contrast, the planktonic mollusks are able to colonize the entire Persian Gulf water body. Their amount in the plankton-benthos ratio always increases with water depth and thereby gives a reliable picture of local water depth variations. This holds true to a depth of around 400 m (corresponding to 80-90 % plankton). This water depth effect can be removed by graphical analysis, allowing the percentage of planktonic mollusks per total sample to be used as a reference base for relative sedimentation rate (sedimentation index). These values vary between 1 and > 1000 and thereby agree well with all the other lines of evidence. The "pteropod ooze" facies is then markedly dependent on the sedimentation rate and can theoretically develop at any depth greater than 65 m (proven at 80 m). It should certainly no longer be thought of as "deep sea" sediment. Based on the component distribution diagrams, grain size and carbonate content, the sediments of the Persian Gulf and the Gulf of Oman can be grouped into 5 provisional facies divisions (Chapt.19). Particularly noteworthy among these are first, the fine grained clayey marl facies occupying the 9 narrow outflow areas of rivers, and second, the coarse grained, high-carbonate marl facies rich in relict sediment which covers wide sediment-poor areas of the basin bottoms. Sediment transport is for the most part restricted to grain sizes < 150 µ and in shallow water is largely coast-parallel due to wave action at times supplemented by tidal currents. Below the wave base gravity transport prevails. The only current capable of moving sediment is the Persian Gulf outflow water in the Gulf of Oman.

Molecular differentiation by PCR-RFLP technique shows that Antarctic fishes of the genus Notothenia, claimed to be two species, are phenotypic varieties with the same genetic pattern (Table 1)

The taxonomy of Antarctic fishes has been predominantly based on morphological characteristics rather than on genetic criteria. A typical example is the Notothenia group, which includes N. coriiceps Richardson, 1844, N. neglecta Nybelin, 1951 and N. rossii Richardson, 1844. The Polymerase Chain Reaction and Restriction Fragment Length Polymorphism (PCR-RFLP) technique was used to determine whether N. coriiceps Richardson, 1844 and N. neglecta Nybelin, 1951 are different or whether they are the same species with morphological, physiological and behavioural variability. N. rossii was used as control. Mitochondrial DNA (mtDNA) was isolated from muscle specimens of N. coriiceps Richardson, 1844, N. neglecta Nybelin, 1951 and N. rossii, which were collected in Admiralty Bay, King George Island. The DNA was used to amplify a fragment (690 base pairs) of the mitochondrial gene coding region of NADH dehydrogenase subunit 2. Further, the amplicon was digested with the following restriction enzymes: DdeI, HindIII and RsaI. The results showed a variation of the digestion pattern of the fragment amplified between N. rossii, and N. coriiceps Richardson, 1844 or N. neglecta Nybelin, 1951. However, no differences were found between N. coriiceps Richardson, 1844 and N. neglecta Nybelin, 1951, on the grounds of the same genetic pattern shown by the two fish.

Results of bulk sediment X-ray diffraction analysis and quantification of mineral phases based on the RockJock and on the QUAX quantitative analysis

We have performed quantitative X-ray diffraction (qXRD) analysis of 157 grab or core-top samples from the western Nordic Seas between (WNS) ~57°-75°N and 5° to 45° W. The RockJock Vs6 analysis includes non-clay (20) and clay (10) mineral species in the <2 mm size fraction that sum to 100 weight %. The data matrix was reduced to 9 and 6 variables respectively by excluding minerals with low weight% and by grouping into larger groups, such as the alkali and plagioclase feldspars. Because of its potential dual origins calcite was placed outside of the sum. We initially hypothesized that a combination of regional bedrock outcrops and transport associated with drift-ice, meltwater plumes, and bottom currents would result in 6 clusters defined by "similar" mineral compositions. The hypothesis was tested by use of a fuzzy k-mean clustering algorithm and key minerals were identified by step-wise Discriminant Function Analysis. Key minerals in defining the clusters include quartz, pyroxene, muscovite, and amphibole. With 5 clusters, 87.5% of the observations are correctly classified. The geographic distributions of the five k-mean clusters compares reasonably well with the original hypothesis. The close spatial relationship between bedrock geology and discrete cluster membership stresses the importance of this variable at both the WNS-scale and at a more local scale in NE Greenland.

Elemental contents, non-carbonate, fatty acids and alcohols analysis from different Holes of IODP Expedition 310

During IODP Expedition 310 (Tahiti Sea Level), drowned Pleistocene-Holocene barrier-reef terraces were drilled on the slope of the volcanic island. The deglacial reef succession typically consists of a coral framework encrusted by coralline algae and later by microbialites; the latter make up < 80% of the rock volume. Lipid biomarkers were analyzed in order to identify organisms involved in reef-microbialite formation at Tahiti, as the genesis of deglacial microbialites and the conditions favoring their formation are not fully understood. Sterols plus saturated and monounsaturated short-chain fatty acids predominantly derived from both marine primary producers (algae) and bacteria comprise 44 wt% of all lipids on average, whereas long-chain fatty acids and long-chain alcohols derived from higher land plants represent an average of only 24 wt%. Bacterially derived mono-O-alkyl glycerol ethers (MAGEs) and branched fatty acids (10-Me-C16:0; iso- and anteiso-C15:0 and -C17:0) are exceptionally abundant in the microbial carbonates (average, 19 wt%) and represent biomarkers of intermediate-to-high specificity for sulfate-reducing bacteria. Both are relatively enriched in 13C compared to eukaryotic lipids. No lipid biomarkers indicative of cyanobacteria were preserved in the microbialites. The abundances of Al, Si, Fe, Mn, Ba, pyroxene, plagioclase, and magnetite reflect strong terrigenous influx with Tahitian basalt as the major source. Chemical weathering of the basalt most likely elevated nutrient levels in the reefs and this fertilization led to an increase in primary production and organic matter formation, boosting heterotrophic sulfate reduction. Based on the observed biomarker patterns, sulfate-reducing bacteria were apparently involved in the formation of microbialites in the coral reefs off Tahiti during the last deglaciation.

Geochemical analysis of minerals from sediment core CRP-2 in the Ross Sea, Antarctica

Distribution patterns, petrography, whole-rock and mineral chemistry, and shape and fabric data are described for the most representative basement lithologies occurring as clasts (granule to bolder grain-size class) from the 625 m deep CRP-2/2A drillcore. A major change in the distribution pattern of the clast types occurs at c. 310 mbsf., with granitoid-dominated clasts above and mainly dolerite clasts below; moreover, compositional and modal data suggest a further division into seven main detrital assemblages or petrofacies. In spite of this variability, most granitoid pebbles consist of either pink or grey biotite±hornblende monzogranites. Other less common and ubiquitous lithologies include biotite syenogranite, biotite-hornblende granodiorite, tonalite, monzogranitic porphyries (very common below 310 mbsf), microgranite, and subordinately, monzogabbro, Ca-silicate rocks, biotite-clinozoisite schist and biotite orthogneiss (restricted to the pre-Pliocene strata). The ubiquitous occurrence of biotite±hornblende monzogranite pebbles in both the Quaternary-Pliocene and Miocene-Oligocene sections, apparently reflects the dominance of these lithologies in the onshore basement, and particularly in the Cambro-Ordovician Granite Harbour Igneous Complex which forms the most extensive outcrop in southern Victoria Land. The petrographical features of the other CRP-2/2A pebble lithologies are consistent with a supply dominantly from areas of the Transantarctic Mountains facing the CRP-2/2A site, and they thus provide further evidence of a local provenance for the supply of basement clasts to the CRP-2/2A sedimentary strata.

Abundance of organic-walled dinoflagellate cysts and geochemical analysis of sediment core GeoB5546-2

NW African climate shows orbital and millenial-scale variations, which are tightly connected to changes in marine productivity. We present an organic-walled dinoflagellate cyst (dinocyst) record from a sediment core off Cape Yubi at about 27°N in the Canary Basin covering the time period from 47 to 3ka before present (BP). The dinocyst record reflects differences in upwelling intensity and seasonality as well as the influence of fluvial input. Sea-level changes play an important role for the upwelling pattern and productivity signals at the core site. Within the studied time interval, four main phases were distinguished. (1) From 45 to 24ka BP, when sea-level was mostly about 75m lower than today, high relative abundances of cysts of heterotrophic taxa point to enhanced upwelling activity, especially during Heinrich Events, while relatively low dinocyst accumulation rates indicate that filament activity at the core location was strongly reduced. (2) At sea-level lowstand during the LGM to H1, dinocyst accumulation rates suggest that local filament formation was even more inhibited. (3) From the early Holocene to about 8ka BP, extraordinary high accumulation rates of most dinocyst species, especially of Lingulodinium machaerophorum, suggest that nutrient supply via fluvial input increased and rising sea-level promoted filament formation. At the same time, the upwelling season prolongated. (4) A relative increase in cysts of photoautotrophic taxa from about 8ka BP on indicates more stratified conditions while fluvial input decreased. Our study shows that productivity records can be very sensitive to regional features. From the dinocyst data we infer that marine surface productivity off Cape Yubi during glacial times was within the scale of modern times but extremely enhanced during deglaciation.

Analysis of Pacific oyster larval proteome and its response to high-CO2

Most calcifying organisms show depressed metabolic, growth and calcification rates as symptoms to high-CO(2) due to ocean acidification (OA) process. Analysis of the global expression pattern of proteins (proteome analysis) represents a powerful tool to examine these physiological symptoms at molecular level, but its applications are inadequate. To address this knowledge gap, 2-DE coupled with mass spectrophotometer was used to compare the global protein expression pattern of oyster larvae exposed to ambient and to high-CO(2). Exposure to OA resulted in marked reduction of global protein expression with a decrease or loss of 71 proteins (18% of the expressed proteins in control), indicating a wide-spread depression of metabolic genes expression in larvae reared under OA. This is, to our knowledge, the first proteome analysis that provides insights into the link between physiological suppression and protein down-regulation under OA in oyster larvae.

Solid phase analysis of sediment core GeoB9309-1 from the Zambezi (or Mozambique) deep-sea fan

The Zambezi deep-sea fan, the largest of its kind along the east African continental margin, is poorly studied to date, despite its potential to record marine and terrestrial climate signals in the southwest Indian Ocean. Therefore, gravity core GeoB 9309-1, retrieved from 1219 m water depth, was investigated for various geophysical (magnetic susceptibility, porosity, colour reflectance) and geochemical (pore water and sediment geochemistry, Fe and P speciation) properties. Onboard and onshore data documented a sulphate/methane transition (SMT) zone at ~ 450-530 cm sediment depth, where the simultaneous consumption of pore water sulphate and methane liberates hydrogen sulphide and bi-carbonate into the pore space. This leads to characteristic changes in the sediment and pore water chemistry, as the reduction of primary Fe (oxyhydr)oxides, the precipitation of Fe sulphides, and the mobilization of Fe (oxyhydr)oxide-bound P. These chemical processes also lead to a marked decrease in magnetic susceptibility. Below the SMT, we find a reduction of porosity, possibly due to pore space cementation by authigenic minerals. Formation of the observed geochemical, magnetic and mineralogical patterns requires a fixation of the SMT at this distinct sediment depth for a considerable time-which we calculated to be ~ 10 000 years assuming steady-state conditions-following a period of rapid upward migration towards this interval. We postulate that the worldwide sea-level rise at the last glacial/interglacial transition (~ 10 000 years B.P.) most probably caused the fixation of the SMT at its present position, through drastically reduced sediment delivery to the deep-sea fan. In addition, we report an internal redistribution of P occurring around the SMT, closely linked to the (de)coupling of sedimentary Fe and P, and leaving a characteristic pattern in the solid P record. By phosphate re-adsorption onto Fe (oxyhydr)oxides above, and formation of authigenic P minerals (e.g. vivianite) below the SMT, deep-sea fan deposits may potentially act as long-term sinks for P.

Pollen analysis of surface sediment off northwest Africa

Over 100 samples of recent surface sediments from the bottomn of the Atlantic Ocean offshore NW Africa between 34° and 6° N have been analysed palynologically. The objective of this study was to reveal the relation between source areas, transport systems, and resulting distribution patterns of pollen and spores in marine sediments off NW Africa, in order to lay a sound foundation for the interpretation of pollen records of marine cores from this area. The clear zonation of the NW-African vegetation (due to the distinct climatic gradient) is helpful in determining main source areas, and the presence of some major wind belts facilitates the registration of the average course of wind trajectories. The present circulation pattern is driven by the intertropical front (ITCZ) which shifts over the continent between c. 22° N (summer position) and c. 4° N (winter position) in the course of the year. Determination of the period of main pollen release and the average atmospheric circulation pattern effective at that time of the years is of prime importance. The distribution patterns in recent marine sediments of pollen of a series of genera and families appear to record climatological/ecological variables, such as the trajectory of the NE trade, January trades, African Easterly Jet (Saharan Air Layer), the northernmost and southernmost position of the intertropical convergence zone, and the extent and latitudinal situation of the NW-African vegetation belt. Pollen analysis of a series of dated deep-sea cores taken between c. 35° and the equator off NW African enable the construction of paleo-distribution maps for time slices of the past, forming a register of paleoclimatological/paleoecological information.

Geochemistry, lithology and maceral analysis at DSDP Hole 71-511

The quantity, type, and maturity of the organic matter in Recent through Upper Jurassic sediments from the Falkland Plateau, DSDP Site 511, have been determined. Sediments were investigated for their hydrocarbon potential by organic carbon and Rock-Eval pyrolysis. Kerogen concentrates were prepared and analyzed in reflected and transmitted light to determine vitrinite reflectance and maceral content. Total extractable organic compounds were analyzed for their elemental composition, and the fraction of the nonaromatic hydrocarbons was determined by capillary column gas chromatography and combined gas chromatography/mass spectrometry. Three main classes of organic matter can be determined at DSDP Site 511 by a qualitative and quantitative evaluation of microscopic and geochemical results. The Upper Jurassic to lower Albian black shales contain high amounts of organic matter of dominantly marine origin. The content of terrigenous organic matter increases at the base of the black shales, whereas the shallowest black shales near the Aptian/Albian boundary are transitional in composition, with increasing amounts of inert, partly oxidized organic matter which is the dominant component in all Albian through Tertiary sediments investigated. The organic matter in the black shales has a low level of maturity and has not yet reached the onset of thermal hydrocarbon generation. This is demonstrated by the low amounts of total extractable organic compounds, low percentages of hydrocarbons, and the pattern and composition of nonaromatic hydrocarbons. The observed reflectance of huminite and vitrinite particles (between 0.4% and 0.5% Ro at bottom-hole depth of 632 m) is consistent with this interpretation. Several geochemical parameters indicate, however, a rapid increase in the maturation of organic matter with depth of burial. This appears to result from the relatively high heat flow observed at Site 511. If we relate the level of maturation of the black shales at the bottom of Hole 511 to their present shallow depth of burial, they appear rather mature. On the basis of comparisons with other sedimentary basins of a known geothermal history, a somewhat higher paleotemperature gradient and/or additional overburden are required to give the observed maturity at shallow depth. A comparison with contemporaneous sediments of DSDP Site 361, Cape Basin, which was the basin adjacent and to the north of the Falkland Plateau during the early stages of the South Atlantic Ocean, demonstrates differences in sedimentological features and in the nature of sedimentary organic matter. We interpret these differences to be the result of the different geological settings for Sites 361 and 511.