Ground penetrating radar (GPR) and electrical resistivity tomography (ERT) survey on the neotectonic activity of the Padul-Nigüelas Fault Zone (PNFZ), Southern Spain

The Padul-Nigüelas Fault Zone (PNFZ) is situated at the south-western mountain front of the Sierra Nevada (Spain) in an extensive regime and belongs to the internal zone of the Betic Cordilleras. The aim of this study is a collection of new evidence for neotectonic activity of the fault zone with classical geological field work and modern geophysical methods, such as ground penetrating radar (GPR). Among an apparently existing bed rock fault scarp with triangular facets, other evidences, such as deeply incised valleys and faults in the colluvial wedges, are present in the PNFZ. The preliminary results of our recent field work have shown that the synsedimentary faults within the colluvial sediments seem to propagate basinwards and the bed rock fault is only exhumed due to erosion for the studied segment (west of Marchena). We will use further GPR data and geomorphologic indices to gather further evidences of neotectonic activity of the PNFZ.

Bacterial activity in sediments of the deep Arabian Sea

In the Arabian Sea, productivity in the surface waters and particle flux to the deep sea are controlled by monsoonal winds. The flux maxima during the South-West (June-September) and the North-East Monsoon (December-March) are some of the highest particle fluxes recorded with deep-sea sediment traps in the open ocean. Benthic microbial biomass and activities in surface sediments were measured for the first time in March 1995 subsequent to the NE-monsoon and in October 1995 subsequent to the SW-monsoon. These measurements were repeated in April/May 1997 and February/March 1998, at a total of six stations from 1920 to 4420 m water depth. This paper presents a summary on the regional and temporal variability of microbial biomass, production, enzyme activity, degradation of 14C-labeled Synechococcus material as well as sulfate reduction in the northern, western, eastern, central and southern Arabian deep sea. We found a substantial regional variation in microbial biomass and activity, with highest values in the western Arabian Sea (station WAST), decreasing approximately threefold to the south (station SAST). Benthic microbial biomass and activity during the NE-monsoon was as high or higher than subsequent to the SW-monsoon, indicating a very rapid turnover of POC in the surface sediments. This variation in the biomass and activity of the microbial assemblages in the Arabian deep sea can largely be explained by the regional and temporal variation in POC flux. Compared to other abyssal regions, the substantially higher benthic microbial biomasses and activities in the Arabian Sea reflect the extremely high productivity of this tropical basin.

Occurrence and activity of anammox bacteria in surface sediments of the southern North Sea

We investigated the occurrence and activity of anaerobic ammonia oxidation (anammox) bacteria in sandy and muddy sand sediments of the southern North Sea. The presence of anammox bacteria was established through the detection of specific phosphocholine-monoether ladderane lipids, 16S rRNA gene, and hydrazine synthase (hzsA) genes. Anammox activity was measured in intact sediment cores (in situ rate) and in sediment slurries (potential rate) as the rate of N2 evolution from 15N-labeled substrates and compared to the transcriptional activity of genes of anammox bacteria. The contribution of anammox to N2 production ranged between 0% and 29%. The potential rate of anammox agreed well with the abundance of anammox bacteria 16S rRNA and hzsA gene copies and the transcriptional activity of the anammox bacteria 16S rRNA gene. We found a higher abundance and activity of anammox bacteria in sediments with higher organic carbon content and also higher activity in summer than in winter. The abundance of anammox bacteria and their potential anammox rates were similar to those reported for other marine coastal sediments, suggesting that potentially they are important contributors to the nitrogen cycle in sandy sediments of shallow continental shelf areas.

Rocks of the Western Kamchatka-Koryak continental margin volcanogenic belt: age, chemical and mineral compositions

An isotope-geochemical study of Eocene-Oligocene magmatic rocks from the Western Kamchatka-Koryak volcanogenic belt revealed lateral heterogeneity of mantle magma sources in its segments: Western Kamchatka, Central Koryak, and Northern Koryak ones. In the Western Kamchatka segment magmatic melts were generated from isotopically heterogeneous (depleted and/or insignificantly enriched) mantle sources significantly contaminated by quartz-feldspathic sialic sediments; higher 87Sr/86Sr (0.70429-0.70564) and lower 143Nd/144Nd [eNd(T) = 0.06-2.9] ratios in volcanic rocks from the Central Koryak segment presumably reflect contribution of an enriched mantle source; high positive eNd(T) and low 87Sr/86Sr ratios in magmatic rocks from the Northern Koryak segment area indicate their derivation from an isotopically depleted mantle source without significant contamination by sialic or mantle material enriched in radiogenic Sr and Nd. Significantly different contamination histories of Eocene-Oligocene mantle magmas in Kamchatka and Koryakia are related to their different thermal regimes: higher heat flow beneath Kamchatka led to crustal melting and contamination of mantle suprasubduction magmas by crustal melts. Cessation of suprasubduction volcanism in the Western Kamchatka segment of the continental margin belt was possibly related to accretion of the Achaivayam-Valagin terrane 40 Ma ago, whereas suprasubduction activity in the Koryak segment stopped due to closure of the Ukelayat basin in Oligocene.

Reconstruction of sea-surface conditions at middle to high latitudes of the Northern Hemisphere

A new calibration database of census counts of organic-walled dinoflagellate cyst (dinocyst) assemblages has been developed from the analyses of surface sediment samples collected at middle to high latitudes of the Northern Hemisphere after standardisation of taxonomy and laboratory procedures. The database comprises 940 reference data points from the North Atlantic, Arctic and North Pacific oceans and their adjacent seas, including the Mediterranean Sea, as well as epicontinental environments such as the Estuary and Gulf of St. Lawrence, the Bering Sea and the Hudson Bay. The relative abundance of taxa was analysed to describe the distribution of assemblages. The best analogue technique was used for the reconstruction of Last Glacial Maximum (LGM) sea-surface temperature and salinity during summer and winter, in addition to sea-ice cover extent, at sites from the North Atlantic (n=63), Mediterranean Sea (n=1) and eastern North Pacific (n=1). Three of the North Atlantic cores, from the continental margin of eastern Canada, revealed a barren LGM interval, probably because of quasi-permanent sea ice. Six other cores from the Greenland and Norwegian seas were excluded from the compilation because of too sparse assemblages and poor analogue situation. At the remaining sites (n= 54), relatively close modern analogues were found for most LGM samples, which allowed reconstructions. The new LGM results are consistent with previous reconstructions based on dinocyst data, which show much cooler conditions than at present along the continental margins of Canada and Europe, but sharp gradients of increasing temperature offshore. The results also suggest low salinity and larger than present contrasts in seasonal temperatures with colder winters and more extensive sea-ice cover, whereas relatively warm conditions may have prevailed offshore in summer. From these data, we hypothesise low thermal inertia in a shallow and low-density surface water layer.

Turbidite layers in sediments of the Dakar Canyon

The relationship of sea-level changes and short-term climatic changes with turbidite deposition is poorly documented, although the mechanisms of gravity-driven sediment transport in submarine canyons during sea-level changes have been reported from many regions. This study focuses on the activity of the Dakar Canyon off southern Senegal in response to major glacial/interglacial sea-level shifts and variability in the NW-African continental climate. The sedimentary record from the canyon allows us to determine the timing of turbidite events and, on the basis of XRF-scanning element data, we have identified the climate signal at a sub-millennial time scale from the surrounding hemipelagic sediments. Over the late Quaternary the highest frequency in turbidite activity in the Dakar Canyon is confined to major climatic terminations when remobilisation of sediments from the shelf was triggered by the eustatic sea-level rise. However, episodic turbidite events coincide with the timing of Heinrich events in the North Atlantic. During these times continental climate has changed rapidly, with evidence for higher dust supply over NW Africa which has fed turbidity currents. Increased aridity and enhanced wind strength in the southern Saharan-Sahelian zone may have provided a source for this dust.

Pollen analysis of sediment cores from the mouth of the river Congo to Walvis Bay and Lüderitz

The distribution of pollen in marine sediments is used to record vegetation changes over the past 30,000 years on the adjacent continent. A transect of marine pollen sequences from the mouth of the river Congo (~5°S) to Walvis Bay and Lüderitz (~25°S) shows vegetation changes in Congo, Angola and Namibia from the last glacial period into the Holocene. The comparison of pollen records from different latitudes provides information about the latitudinal shift of open forest and savannahs (Poaceae pollen), the extension of lowland forest (rain forest pollen) and Afromontane forest (Podocarpus pollen), and the position of the desert fringe (pollen of Caryophyllaceae, Chenopodiaceae and Amaranthaceae). High Cyperaceae pollen percentages in sediments from the last glacial period off the mouth of the river Congo suggest the presence of open swamps rather than savannah vegetation in the Congo Basin. Pollen from Restionaceae in combination with Stoebe-type pollen (probably from Elytropappus) indicates a possible northwards extension of winter rain vegetation during the last glacial period. The record of Rhizophora (mangrove) pollen is linked to erosion of the continental shelf and sea-level rise. Pollen influx is highest off river mouths (10-2000 grains year**-1 cm**-2), close to the coast (300-6000 grains year**-1 cm**-2), but is an order of magnitude lower at sites situated far from the continent (<10 grains year**-1 cm**-2).

Radioactivity of the Chernobyl fallout at Tyrolean glaciers

The stratigraphy of the gross-beta-activity of the Chernobyl fallout was measured in samples from glaciers in Tyrol. Great regional differences were obtained. The comparison of the results of samples collected in 1986 and 1987 shows a significant immigration of the fission products into deeper layers by melt water percolation but without any significant fractionation occuring. Gammaspectra show the dominance of 137Cs with the ratio 137Cs/134Cs of 2.6 to 2.9 (measurement February 1987) and 3.7 (measurement January 1988).

Respiration rates and abundances of dominant copepods of the northern Benguela Current System

Respiration rates of 16 calanoid copepod species from the northern Benguela upwelling system were measured on board RRS Discovery in September/October 2010 to determine their energy requirements and assess their significance in the carbon cycle. Individual respiration rates were standardised to a mean copepod body mass and a temperature regime typical of the northern Benguela Current. These adjusted respiration rates revealed two different activity levels (active and resting) in copepodids C5 of Calanoides carinatus and females of Rhincalanus nasutus, which reduced their metabolism during dormancy by 82% and 62%, respectively. An allometric function (Imax) and an energy budget approach were performed to calculate ingestion rates. Imax generally overestimated the ingestion rates derived from the energy budget approach by >75%. We suggest that the energy budget approach is the more reliable approximation with a total calanoid copepod (mainly females) consumption of 78 mg C m-2 d-1 in neritic regions and 21 mg C m-2 d-1 in oceanic regions. The two primarily herbivorous copepods C. carinatus (neritic) and Nannocalanus minor (oceanic) contributed 83% and 5%, respectively, to total consumption by calanoid copepods. Locally, C. carinatus can remove up to 90% of the diatom biomass daily. In contrast, the maximum daily removal of dinoflagellate biomass by N. minor was 9%. These estimates imply that C. carinatus is an important primary consumers in the neritic province of the northern Benguela system, while N. minor has little grazing impact on phytoplankton populations further offshore. Data on energy requirements and total consumption rates of dominant calanoid copepods of this study are essential for the development of realistic carbon budgets and food-web models for the northern Benguela upwelling system.

14C activity of Antarctic lichens

By the nuclear bomb tests during the 1950s and early 1960s, the radiocarbon content of the atmospheric CO, on the Southern Hemisphere rose within a few years from 98 to 162% of the standard recent value and then dropped to 122% (at the end of 1984). This rapid fluctuation was used to determine the lifetime of five species of lichens collected in the beginning of 1985 in the maritime Antarctic. Under the assumption that Lichens assimilate each year carbon at the same rate and that carbon once fixed at least in main branches never will be exchanged later on. The age of mature thalli of Caioplaco regalis, Ramalino tetebrata and Ustiea antarctica was determined to 32 years, while U, aurantiaco-atra and Himantormia lugubris gave an age of ca. 38 years and ca. 60 years, respectively.