Live benthic foraminifera in surface sediments of the Indo-Pakistan continental margin

The Indo-Pakistan Continental Margin represents an extreme habitat for benthic foraminifera since (1) high fluxes of organic matter offer a high food supply, (2) an intensified oxygen minimum Zone (OMZ) develops from the base of the euphotic Zone to water depths over 1000 m and (3) the monsoon causes seasonal oscillations within the biogeochemical cycle. At three stations from the uppermost (233 m), the central (658 m) and the deeper part (902 m) of the OMZ, living benthic foraminiferal assemblages were analyzed within the uppermost 10 cm of the sediment column. The ecologic structure of foraminiferal faunas is characterized by high abundances at the sediment surface and a rapid decrease within the uppermost 2 cm of the sediment column. Despite dysoxic to suboxic bottom-water conditions, stained benthic foraminifera occurred in all cores down to the base of the sampled interval. High surface abundances, a high dominance by few endobenthic calcareous taxa and a low diversity, which may result from specific physiological adaptations to almost anoxic conditions and the absence of predators, are recognized in the central part of the OMZ. The upper and lower margins of the OMZ are characterized by higher diversities and lower abundances. The shallowest part of the OMZ is dominated by calcareous foraminifera, whereas agglutinated species are the most common taxa in the deeper part. Comparisons with previous studies show that benthic foraminiferal assemblages, that are influenced by seasonal oscillations controlling food supply and/or the availability of oxygen, show variations in faunal density and species composition. Since there is strong evidence that oxygen is not a limiting factor for some taxa, it seems more likely that the distribution pattern of benthic foraminifera is preferentially controlled by trophic conditions.

Calculated surface water paleotemperatures for the lower Pliocene at DSDP Site 18-173 from the California continental slope (Table I)

The oxygen isotope record of the planktonic foraminifera Globigerina bulloides and Neogloboquadrina pachyderma from Pliocene and early Pleistocene sediments at both DSDP site 173 and the Centerville Beach section in California suggests a large influx of isotopically light water in this area during late Pliocene and early Pleistocene time. Salinity may have been reduced by as much as 2 to 4 ?. Surface sea water paleotemperatures for the lower Pliocene range from 9.5°C to 15.5°C. The oxygen isotope record of the benthonic genus Uvigerina shows little variation indicating environmental stability at depth. At DSDP site 173 the small variation in Uvigerina is due to variation in the oxygen isotopic composition of the oceans as glaciers waxed and waned. At the Centerville Beach section the oxygen isotopic composition of Uvigerina reflects the gradual shoaling of the Humboldt Basin. Carbon and oxygen isotope ratios in G. bulloides and N. pachyderma are inversely correlated at the 95% confidence level. This may indicate that the oxygen and carbon isotopic composition of foraminifera are influenced by the same factors. On the other hand, the inverse correlation may be due to metabolic fractionation. No correlation was found between oxygen and carbon isotopic composition in Uvigerina.

Bottom water properties observed during Nathanial B. Palmer cruises NBP00-08 and NBP04-08 to the Southern Ocean

We report on observations of dense shelf water overflows and Antarctic Bottom Water (AABW) formation along the continental margin of the Adelie and George V Land coast between 140°E and 149°E. Vertical sections and bottom layer water mass properties sampled during two RVIB Nathaniel B Palmer hydrographic surveys (NBP00-08, December 2000/January 2001 and NBP04-08, October 2004) describe the spreading of cold, dense shelf water on the continental slope and rise from two independent source regions. The primary source region is the Adelie Depression, exporting high-salinity dense shelf water through the Adelie Sill at 143°E. An additional eastern source region of lower-salinity dense shelf water from the Mertz Depression is identified for the first time from bottom layer properties northwest of the Mertz Sill and Mertz Bank (146°E-148°E) that extend as far as the Buffon Channel (144.75°E) in summer. Regional analysis of satellite-derived ice production estimates over the entire region from 1992 to 2005 suggests that up to 40% of the total ice production for the region occurs over the Mertz Depression and therefore this area is likely to make a significant contribution to the total dense shelf water export. Concurrent time series from bottom-mounted Microcats and ADCP instruments from the Mertz Polynya Experiment (April 1998 to May 1999) near the Adelie Sill and on the upper continental slope (1150 m) and lower continental rise (3250 m) to the north describe the seasonal variability in downslope events and their interaction with the ambient water masses. The critical density for shelf water to produce AABW is examined and found to be 27.85 kg/m**3 from the Adelie Depression and as low as 27.80 kg/m**3 from the Mertz Depression. This study suggests previous dense shelf water export estimates based on the flow through the Adelie Sill alone are conservative and that other regions around East Antarctica with similar ice production to the Mertz Depression could be contributing to the total AABW in the Australian-Antarctic Basin.

Rock magnetic, element, and color data of three sediment cores along the Senegalese continental margin

We present a suite of new high-resolution records (0-135 ka) representing pulses of aeolian, fluvial, and biogenic sedimentation along the Senegalese continental margin. A multiproxy approach based on rock magnetic, element, and color data was applied on three cores enclosing the present-day northern limit of the ITCZ. A strong episodic aeolian contribution driven by stronger winds and dry conditions and characterized by high hematite and goethite input was revealed north of 13°N. These millennial-scale dust fluxes are synchronous with North Atlantic Heinrich stadials. Fluvial clay input driven by the West African monsoon predominates at 12°N and varies at Dansgaard-Oeschger time scales while marine productivity is strongly enhanced during the African humid periods and marine isotope stage 5. From latitudinal signal variations, we deduce that the last glacial ITCZ summer position was located between core positions at 12°26' and 13°40'N. Furthermore, this work also shows that submillennial periods of aridity over northwest Africa occurred more frequently and farther south than previously thought.

Pore water concentrations and solid phase concentrations of sediment cores from the Ligurian continental slope

In October 1979, a period of heavy rainfall along the French Riviera was followed by the collapse of the Ligurian continental slope adjacent to the airport of Nice, France. A body of slope sediments, which was shortly beforehand affected by construction work south of the airport, was mobilized and traveled hundreds of kilometers downslope into the Var submarine canyon and, eventually, into the deep Ligurian basin. As a direct consequence, the construction was destroyed, seafloor cables were torn, and a small tsunami hit Antibes shortly after the failure. Hypotheses regarding the trigger mechanism include (i) vertical loading by construction of an embankment south of the airport, (ii) failure of a layer of sensitive clay within the slope sequence, and (iii) excess pore fluid pressures from charged aquifers in the underground. Over the previous decades, both the sensitive clay layers and the permeable sand and gravel layers were sampled to detect freshened waters. In 2007, the landslide scar and adjacent slopes were revisited for high-resolution seafloor mapping and systematic sampling. Results from half a dozen gravity and push cores in the shallow slope area reveal a limited zone of freshening (i.e. groundwater influence). A 100-250 m wide zone of the margin shows pore water salinities of 5-50% SW concentration and depletion in Cl, SO4, but Cr enrichment, while cores east or west of the landslide scar show regular SW profiles. Most interestingly, the three cores inside the landslide scar hint towards a complex hydrological system with at least two sources for groundwater. The aquifer system also showed strong freshening after a period of several months without significant precipitation. This freshening implies that charged coarse-grained layers represent a permanent threat to the slope's stability, not just after periods of major rainfall such as in October 1979.

Aragonite distribution and preservation of sediment cores from the Brazilian Continental Slope

We present late Quaternary records of aragonite preservation determined for sediment cores recovered on the Brazilian Continental Slope (1790-2585 m water depth) where North Atlantic Deep Water (NADW) dominates at present. We have used various indirect dissolution proxies (carbonate content, aragonite/calcite contents, and sand percentages) as well as gastropodal abundances and fragmentation of Limacina inflata to determine the state of aragonite preservation. In addition, microscopic investigations of the dissolution susceptibility of three Limacina species yielded the Limacina Dissolution Index which correlates well with most of the other proxies. Excellent preservation of aragonite was found in the Holocene section, whereas aragonite dissolution gradually increases downcore. This general pattern is attributed to an overall increase in aragonite corrosiveness of pore waters. Overprinted on this early diagenetic trend are high-frequency fluctuations of aragonite preservation, which may be related to climatically induced variations of intermediate water masses.

Geological map of MONSRUDNABBEN, Heimefrontfjella, Antarctica (Scale 1:25,000)

Topographic data of this geological map were obtained through stereoscopic aerial photo interpretation. The photogrammetric photo flights were undertaken in 1986 by the Institut für Angewandte Geodäsie, Frankfurt. Horizontal ground control points required for aerial photo interpretation were determined by means of Doppler satellite observation during the 2nd German Neuschwabenland Expedition 1985/86. Vertical ground control points were taken from unpublished map drafts at 1:100 000 scale by Norsk Polarinstitutt, Oslo. The elevation above mean sea level was transferred to Heimefrontfjella barometrically. For this reason assertions concerning the absolute elevation (referred to sea level) are uncertain. Contours and spot heights presented on the map were obtained from the photogrammetric evaluation of the photography taken in 1986; relative elevation data (hight differences) are accurate to approximately ±10 m.

Tab. 1: U-Pb analyses of zircons from rock samples in MT. Newton and Cumpston Massif, East Antarctica

We present new U-Pb zircon (SHRIMP) data on rocks from Mt Newton and Cumpston Massif in the southern Prince Charles Mountains. Our data demonstrate that Mt Newton was affected by a newly proposed Palaeoproterozoic "Newton" Orogeny at c. 2100-2200 Ma. Sedimentation, felsic volcanism (c. 2200 Ma), metamorphism and folding, followed by granite intrusion (c. 2100 Ma), suggest development of a trough or aulacogene in the area during the early Palaeoproterozoic. An orthogneiss from Cumpston Massif yielded an age of c. 3180 Ma for granitic protolith emplacement, which is in good agreement with many U-Pb zircon ages from similar rocks in the southern Mawson Escarpment. A syn- to late-tectonic muscovite-bearing pegmatite from Cumpston Massif yielded a c. 2500 Ma date of emplacement, which indicates early Palaeoproterozoic activity in this block, probably in response to a tectono-magmatic episode in the Lambert Terrane bordering the Ruker Terrane in the northeast. The correlation of tectono-magmatic events in both the Ruker and Lambert terranes of the southern Prince Charles Mountains provides evidence for their common evolution during the Proterozoic.

Benthic foraminifera and stable isotope composition in Paleocene-Eocene sediments

In the late Paleocene to early Eocene, deep sea benthic foraminifera suffered their only global extinction of the last 75 million years and diversity decreased worldwide by 30-50% in a few thousand years. At Maud Rise (Weddell Sea, Antarctica; Sites 689 and 690, palaeodepths 1100 m and 1900 m) and Walvis Ridge (Southeastern Atlantic, Sites 525 and 527, palaeodepths 1600 m and 3400 m) post-extinction faunas were low-diversity and high-dominance, but the dominant species differed by geographical location. At Maud Rise, post-extinction faunas were dominated by small, biserial and triserial species, while the large, thick-walled, long-lived deep sea species Nuttallides truempyi was absent. At Walvis Ridge, by contrast, they were dominated by long-lived species such as N. truempyi, with common to abundant small abyssaminid species. The faunal dominance patterns at the two locations thus suggest different post-extinction seafloor environments: increased flux of organic matter and possibly decreased oxygen levels at Maud Rise, decreased flux at Walvis Ridge. The species-richness remained very low for about 50 000 years, then gradually increased. The extinction was synchronous with a large, negative, short-term excursion of carbon and oxygen isotopes in planktonic and benthic foraminifera and bulk carbonate. The isotope excursions reached peak negative values in a few thousand years and values returned to pre-excursion levels in about 50 000 years. The carbon isotope excursion was about -2 per mil for benthic foraminifera at Walvis Ridge and Maud Rise, and about -4 per mil for planktonic foraminifera at Maud Rise. At the latter sites vertical gradients thus decreased, possibly at least partially as a result of upwelling. The oxygen isotope excursion was about -1.5 per mil for benthic foraminifera at Walvis Ridge and Maud Rise, -1 per mil for planktonic foraminifera at Maud Rise. The rapid oxygen isotope excursion at a time when polar ice-sheets were absent or insignificant can be explained by an increase in temperature by 4-6°C of high latitude surface waters and deep waters world wide. The deep ocean temperature increase could have been caused by warming of surface waters at high latitudes and continued formation of the deep waters at these locations, or by a switch from dominant formation of deep waters at high latitudes to formation at lower latitudes. Benthic foraminiferal post-extinction biogeographical patterns favour the latter explanation. The short-term carbon isotope excursion occurred in deep and surface waters, and in soil concretions and mammal teeth in the continental record. It is associated with increased CaC03-dissolution over a wide depth range in the oceans, suggesting that a rapid transfer of isotopically light carbon from lithosphere or biosphere into the ocean-atmosphere system may have been involved. The rapidity of the initiation of the excursion (a few thousand years) and its short duration (50 000 years) suggest that such a transfer was probably not caused by changes in the ratio of organic carbon to carbonate deposition or erosion. Transfer of carbon from the terrestrial biosphere was probably not the cause, because it would require a much larger biosphere destruction than at the end of the Cretaceous, in conflict with the fossil record. It is difficult to explain the large shift by rapid emission into the atmosphere of volcanogenic CO2, although huge subaerial plateau basalt eruptions occurred at the time in the northern Atlantic. Probably a complex combination of processes and feedback was involved, including volcanogenic emission of CO2, changing circulation patterns, changing productivity in the oceans and possibly on land, and changes in the relative size of the oceanic and atmospheric carbon reservoirs.

Ladderane lipid analysis and pore water and sediment chemistry of sediment cores from the continental shelf and slope off northwest Africa

The presence and abundance of anaerobic ammonium-oxidizing (anammox) bacteria was investigated in continental shelf and slope sediments (300-3000 m water depth) off northwest Africa in a combined approach applying quantitative polymerase chain reaction (q-PCR) analysis of anammox-specific 16S rRNA genes and anammox-specific ladderane biomarker lipids. We used the presence of an intact ladderane monoether lipid with a phosphocholine (PC) headgroup as a direct indicator for living anammox bacteria and compared it with the abundance of ladderane core lipids derived from both living and dead bacterial biomass. All investigated sediments contained ladderane lipids, both intact and core lipids, in agreement with the presence of anammoxspecific 16S rRNA gene copies, indicating that anammox occurs at all sites. Concentrations of ladderane core lipids in core top sediments varied between 0.3 and 97 ng g**-1 sediment, with the highest concentrations detected at the sites located on the shelf at shallower water depths between 300 and 500 m. In contrast, the C20 [3]-ladderane monoether-PC lipid was most abundant in a core top sediment from 1500 m water depth. Both anammox-specific 16S rRNA gene copy numbers and the concentration of the C20 [3]-ladderane monoether-PC lipid increased downcore in sediments located at greater water depths, showing highest concentrations of 1.2 x 10**8 copies g**-1 sediment and 30 pg g**-1 sediment, respectively, at the deepest station of 3000 m water depth. This suggests that the relative abundance of anammox bacteria is higher in sediments at intermediate to deep water depths where carbon mineralization rates are lower but where anammox is probably more important than denitrification.

(Table 1) Stratigraphic occurrence and fossil content of fossiliferous horizons in southern north Victoria Land

In contrast to the adjacent parts of the Transantarctic Mountains, the Mesozoic macrofossil record of north Victoria Land remains poorly documented. During the Ninth German Antarctic North Victoria Land Expedition (GANOVEX IX 2005/2006) twelve fossil sites in southern north Victoria Land were discovered and sampled. Fossils from the Triassic to Early Jurassic Section Peak Formation were collected from Archambault Ridge, Anderton Glacier, Skinner Ridge, Timber Peak, Vulcan Hills, Runaway Hills, Section Peak and Shafer Peak. These localities have yielded abundant fossil wood and compressions of horsetails, ferns, and seed ferns. In addition, several beetle elytra were found at Timber Peak. Fossil localities of the overlying Shafer Peak Formation and Exposure Hill-type deposits occur at Shafer Peak and in the Mount Carson area, and have yielded various trace fossils, permineralized wood, leaf compressions, and conchostracans. Two newly discovered fossil sites are associated with the late Early Jurassic Kirkpatrick lava flows. Upright-standing tree trunks have been recorded at Suture Bench, and highly fossiliferous sedimentary interbeds occur at the southwestern end of the Mesa Range. Of special interest is the exquisite fossil preservation at some of the sites. Compression fossils from Timber Peak and Shafer Peak contain well-preserved cuticles, which is very rare in the Antarctic. An Early Jurassic permineralized deposit at Mount Carson contains structurally preserved ferns. Furthermore, the arthropod fossils from sedimentary interbeds at the Mesa Range are preserved in minute detail, including antennae and limb spines of a blattid insect.

Abundance of diatom cells in sediments from the Okhotsk and Bering Seas and the Northwest Pacific Ocean

The present investigation was targeted at diatom composition studies in the surface sediments (0-1 cm) sampled in the Sea of Okhotsk and the northwest Pacific in the depth range from 130 to 6110 m. The taxonomic analysis, as well as the quantitative (the diatom cell abundance per sediment dry weight unit) content and ecological group definition, was applied. Ten diatom taxa are the main body (80-100%) of the diatom assemblages: Bacterosira bathyomphala, Chaetoceros spp. (spores), Actinocyclus curvatulus, Thalassiosira latimarginata (group), T. antarctica (spores), Neodenticula seminae, Rhizosolenia hebetata f. hiemalis, Thalassiothrix longissima, Coscinodiscus marginatus, Coscinodiscus oculus iridis. The relative content of these species reflects the sedimentation conditions for different parts of the sea: the shelf, the continental slope, the open sea, and the ocean. The highest diatom content (45.6.3-60.0 mln per g of dry weight) was found for the surface sediments in the central part of the Sea of Okhotsk and the continental slope of western Kamchatka.

(Table 1) Concentrations of organic pollutants in soil samples from Adélie penguin (Pygoscelis adeliae) colonies and reference sites, Hop Island, Antarctica

Although long-range atmospheric transport has been described as the predominant mechanism for exposing polar regions to persistent organic pollutants (POPs), recent studies have suggested that bird activity can also contribute substantially to contaminant levels in some environments. However, because the species so far reported have all been migratory, it has not been demonstrated conclusively whether locally elevated contamination represents transport from lower latitudes by the migrating birds or, alternatively, redistribution and concentration of contaminants that were already present in the high-latitude environments. The present study demonstrates, for the first time, that several POPs are present in elevated concentrations in an environment frequented by a non-migratory species (Adelie penguins) that spends its entire life in the Antarctic. Levels of POPs, such as p,p'-DDE, hexachlorobenzene (HCB), chlordanes (CHLs) and polychlorinated biphenyls (PCBs), were 10 to 100-fold higher in soil samples from penguin colonies than from reference areas. This significant difference is likely related to local penguin activity, such as a higher abundance of guano and the presence of bird carcasses. This hypothesis is also supported by a higher percentage of persistent congeners (PCB 99, 118, 138 and 153) in the soil from the colonies compared to the reference areas. This profile of PCB congeners closely matched profiles seen in penguin eggs or penguin blood.