ALBERT

Description: The multidisciplinary research cruise 64PE350 was conducted in the central part of the Red Sea to strengthen our understanding of volcanism and tectonics and related hydrothermal processes in this young rifting system. Therefore we extended our intense multibeam mapping campaign, which had started during the PO408 cruise in 2011, by mainly focusing on the hydrothermally active “Multi Deep” area. Detailed geological mapping was performed by selective rock sampling (dredging, coring) in areas of special interest (i.e. fresh basalt flows, or zones with signals of recent volcanic activities). Moreover, a geochemical sampling campaign (i.e. gravity coring, Niskin water sampling) was conducted in brine-filled Red Sea deeps where variable hydrothermal activity is expected. The geochemical characteristics of sediment (pore water and mineral composition) and brine will help to identify sources and sinks relative to hydrothermal activity (e.g. hydrocarbon inflow, heavy metal concentrations in brine and sediment, etc.). Transport and degradation processes (biogeochemical cycles) at the brine- seawater interfaces were investigated by high-resolution water sampling and subsequent onboard membrane inlet mass spectrometry, gas chromatography, and major and trace element sampling. Biomarker studies are being performed by sampling/ filtering water column and brine to decipher allochthonous from autochthonous organic matter input to the Red Sea Deeps. Moreover, microbiological studies will be performed on selected brine and sediment samples. Hydrocarbon seepage at the pockmark area was investigated by hydroacoustic and geophysical methods (water column imaging, sparker reflection seismics). Additionally, sediment cores were retrieved from selected pockmark structures to investigate gas/ fluid seepage activities during Holocene. The recently described subsea salt glacier phenomenon was investigated by seismic reflection studies and comparative multibeam profiling (salt glacier flow velocities will be calculated).

Description: R/V POSEIDON cruise P457 aimed further development of detailed marine tephrochronology of Iceland by sediment coring in order to improve our knowledge of the spatio-temporal evolution of Icelandic volcanism and related hazards. In addition, the marine record contains paleoclimatic information, which may relate recurrent glacier advances and land degradation periods to ocean and atmospheric circulation changes. A minor sub-project should contribute to a better understanding of Surtsey volcanism by investigations of marine Surtsey tephra. P457 conducted extensive sediment echosounding (11 surveys with a total length of c. 425 nm) in order to identify undisturbed sediment sequences for coring. At 20 appropriate sites, P457 deployed gravity and/or gaint box corers to recover ultra-high resolution sediment cores from 〈 100 m to ~1,600 m water depth at the south-western, southern and eastern sectors of the Icelandic shelf and slope. Of these deployments, 9 gravity corers yielded altogether 59.5 m core recovery and 11 box corers recovered surface sediment samples. Additionally 7 CTD/rosette water sampling stations have been performed at shallow sites close to Iceland and at deep sites further offshore in order to determine the REE distributions and the Nd and Hf isotope compositions of the sea water. No equipment was lost or significantly damaged. Cruise P457 was particularly successful in the working areas southwest and south of Iceland but failed to recover long sediment cores in the eastern working areas and at Surtsey. Sand, clayey silt, clayey sandy silt, sandy clayey silt, and volcanic ashes are the dominant lithologies in the P457 sediment cores. Preliminary studies of selected sedimentary records along the Iceland margin from ca. 24°W to 12°W on both sides of Reykjanes Ridge suggest that a correlation of these cores is possible, implying that sedimentary records are undisturbed and of high quality. Notably, distinct volcanic ash layers can apparently be traced in the P457 cores across the working area. Preliminary age models of selected cores show that the sedimentation rates around Iceland are low with only a thin Holocene. Sediment records cover approximately 120.000 years at most.

Description: During the two legs of cruise MSM34 of R/V MARIA S. MERIAN regional 2D seismic surveying, high resolution 2D and 3D seismic imaging, geo-chemical sampling, heatflow measurements and long-term piezometer installations were undertaken. A grid of 28 2D seismic profiles was collected across the palaeo Danube delta. A number of inactive and partly buried channel systems could be mapped. Most of them were underlain by one or more bottom simulation reflectors (BSR). Based on the seismic brute stack images and the limits of the MeBo drilling device a prospective channel system with indications for possible gas hydrate formation at shallow depth (BSR, inverted strong amplitudes) could be identified in about 1500 m water depth. High resolution 2D seismic and 3D P-Cable seismic were used together with OBS deployments in order to allow structural mapping and physical description of the channel infill. Heatflow measurements and geochemical analyses of gravity and multi corer samples accompany these investigations. Neither the multibeam water column images nor Parasound records show any evidence of flares (gas bubbles in the water column) in this working area suggesting a well sealed hydrate reservoir. Active gas expulsion from the seafloor was observed at about 200 m water depth circling around a slump area. The base plane of the failed sediment volume builds the current seafloor at about 600 m to 700 m water depth. On regional 2D seismic profiles a BSR has been mapped underneath the slope failure with unexpectedly strong upward bending. High resolution 2D and 3D P-Cable seismic investigations with complementary OBS deployment will allow imaging the BSR outline. Moreover velocity analyses, heatflow measurements and geo-chemical samples will be available for a detailed description of hydrate distribution and sediment parameters. In a third working area high resolution 2D seismic reflection profiles were acquired across a fully buried channel system. Together with the regional seismic lines slope failure of the channel fill material can be studied across the slope extension of the system.

Description: The underlying scientific motivation of SO227 was to constrain the geological processes that control the distribution and saturation of hydrate in marine sediments. The most important objective of the cruise was to observe the effect of additional fluid advection along blind thrusts into the gas hydrate stability zone. With its clear distinction into a passive margin and an active margin the area SW of Taiwan is particularly well suited for this kind of research because it is very well studied and it is known where the tectonic structures of the compression and subduction zone disturb the otherwise fairly homogeneous surface sediments of the margin. After a reconnaissance survey using multi beam echo sounder and side scan sonar we selected two sites that are typical for the active and passive margin, respectively. At these two sites we carried out comprehensive geophysical experiments including high-resolution 3D seismic imaging with the P-Cable system, ocean bottom seismometer (OBS) deployments, controlled source electromagnetic (CSEM) measurements, heat flow measurements, and ground-truthing using HyBis and TV grab. While the P-Cable data allow us to determine the internal structure of the study areas down to a depth of approximately 500 m below sea floor, the OBS and CSEM data will constrain the hydrate and free gas saturation along twodimensional transect through the 3D seismic cubes. The heat flow data will provide information on the thermal conditions of the sediments. The first site covers the Formosa Ridge on the passive margin of the South China Sea. The ridge is the result of canyon erosion in the north, west, and east. The high-resolution threedimensional seismic data show a continuous bottom simulating reflector (BSR) marking the base of the hydrate stability zone. Particularly, underneath the canyon in the north the BSR is much shallower than underneath the centre of the ridge. This may indicates that the canyon incision has changed the hydrate stability field and that hydrate formation at depth has not been able to adjust to the new pressure and temperature conditions. The second site includes a roll over anticline called Four-Way-Closure Ridge which is the surface expression of an underlying blind thrust. In this area numerous high amplitude reflectors occur above the BSR. This unusual observation may suggest very high gas hydrate saturations and coeval presence of free gas and gas hydrate in the sediments. Evaluation of the OBS and CSEM data will allow to test this hypothesis. The 3D seismic data clearly show fluid migration pathways through the gas hydrate stability to the sea floor. Sea floor video footage and sampling confirmed the presence of on-going methane seepage at the Formosa Ridge above the fluid migration pathway imaged in the 3D seismic data. They also establish that there is at least one seep on the Four-Way-Closure Ridge at which methane is released into the ocean above another seismically imaged fluid migration pathway. This is the first active seep site with chemosynthetic ecosystems discovered on the active margin SW off Taiwan.

Description: 13.04. – 27.04.2013 Port Calls: Gdynia, Poland 19. – 21.04.2013

Description: R/V SONNE cruise SO-233 WALVIS II conducted geological, morphological, and biological studies in the area of the aseismic Walvis Ridge and the adjacent ocean floor (South Atlantic). The Walvis Ridge is a textbook example of a hotspot track connected to a continental flood basalt province and represents the Atlantic “type locality” for the enriched mantle one (EM-I) geochemical endmember in intraplate volcanic rocks. Despite its importance in the global hotspot reference frame, endmember geochemical composition, and uncertainties in its formation and evolution, basement sampling of the Walvis Ridge remained poor to date, in particular along its easternmost 1500 km. The geological studies carried out during SO-233 therefore aimed for extensive multi-beam mapping using a SIMRAD EM 120 echo-sounding system, sediment echo-sounding using a ATLAS PARASOUND sub-bottom profiling system, and hard rock sampling by dredging and TV-grab of the Walvis Ridge and associated features. The major targets of the WALVIS II project are (1) to test for age progressive volcanism along the ridge, (2) to differentiate between classical hotspot and plate fracturing models for its formation, and (3) to constrain the origin, temporal and spatial evolution of melting conditions and source compositions (in particular regarding the EM-I endmember and proposed zonation models of mantle plumes). The biology program conducted on SO-233 comprised sampling of benthic organisms and meiofauna using a TV-multi-corer, a TV-grab, sediment traps installed in the geological dredges, and by collecting marine invertebrates from the hard rocks yielded by dredging. The biological investigations of the WALVIS II project intend to describe the benthic diversity of deep-sea invertebrates of the Walvis Ridge and will help to identify proxies of species connectivity and dispersal between the Walvis Ridge and neighboring ridge like structures (e.g. Agulhas Ridge). Another objective is to test whether connectivity of benthic communities in the Angola and Cape Basins is interrupted by the Walvis Ridge. SO-233 multi-beam mapping revealed that the southern bifurcated section of the Walvis Ridge appears to have formed through the coalescence of former volcanic islands. The new bathymetric data also yielded several evidence for large-scale extensional tectonic movements which are most likely related to the separation of the Walvis Ridge and Rio Grande Rise that were rifted apart by the mid Atlantic Ridge. Seventy-one dredge hauls have been conducted during SO-233. Of these, 28 delivered massive lavas, 24 volcaniclastic rocks including breccias containing lava fragments, 22 sedimentary rocks, and 11 Mn-Fe-oxide crusts and nodules. The volcanic rocks comprise a broad variety of lavas as well as epiclastic, hydroclastic, and pyroclastic rocks. Carbonates dominate among the non-volcanic rocks, many of them represent relicts of fossil coral reefs. Despite technical problems with the EM 120 system and difficult weather and seafloor conditions occasionally constraining rock sampling, SO-233 achieved its major goals, i.e. bathymetric mapping and representative hard rock sampling of all major geomorphological units of the Walvis Ridge and of associated features. The set of rock samples recovered during SO-233 represents the by far most detailed sampling of the Walvis Ridge to date. Out of 91 collecting stations, 80 stations yielded the total amount of 80 kg of sediment from sediment traps in the geological dredges, TV-multi-corer tubes and TV-grab. At 44 stations we could collect macrofaunal organisms, partly in large quantities. Ninety specimens of living brachiopods representing 6 genera were found at all depths and will mainly be used for molecular diversity studies. The remaining living macrofauna was largely composed of sponges, octocorals, some deep water hexacorals, molluscs, polychaetes, bryozoans, cirriped crustaceans and a few isopods and amphipods, mainly occurring in small numbers and medium diversity. The most spectacular finding was a fossil cold water reef mound community, which shows similarities in species composition to North Atlantic cold water reefs and proofs the influence of Antarctic benthos communities on the Walvis Ridge fauna mediated by northbound cold water currents. The samples represent the most diverse collection of benthos organisms ever retrieved from the Walvis Ridge region.

Description: R/V SONNE cruises SO-224 and SO-225 are part of the cooperative project MANIHIKI II between GEOMAR Helmholtz Centre for Ocean Research Kiel and the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI), funded by the German Ministry of Education and Research (BMBF). This multidisciplinary project continues previous research at the Manihiki Plateau conducted since 2007 (SO-193) on morphological, volcanological, geochemical, and geochronological studies and is now broadened by geophysical and paleoceanographic research foci. SO-225 focused on stratigraphically controlled sampling of the igneous successions of the Manihiki Plateau. This has been accomplished by using the remotely operated vehicle ROV Kiel 6000 and chain bag dredges. Coring of deep sea sediments and sampling of the overlying water column has been added to the program. SO-225 and subsequent shore-based research in the home institutes mainly address (1) the temporal, spatial, and compositional evolution of the igneous basement of Manihiki Plateau, (2) the environmental impact of the large volcanic eruptions, which formed the Manihiki Plateau, (3) the Plio-Pleistocene dynamics and evolution of the West Pacific Warm Pool during the last ~3 million years, and (4) the potential oceanographic interaction between the equatorial Pacific and the Southern Ocean (“ocean tunnel hypothesis”) and its climatic responses. The integration of scientific results from SO-224 and SO-225 with existing data from the West Pacific large igneous provinces Manihiki, Hikurangi, and Ontong Java will contribute towards a better understanding of the origin and effects of volcanic mega events, the formation of large igneous provinces, and the paleoceanography and paleoclimate of the equatorial West Pacific. R/V SONNE cruise SO-225 started in Suva/Fiji on November 21st, 2012, and ended in Auckland/New Zealand on Januar 5th, 2013. Complementing 2,940 nm multi-beam mapping and 2,250 nm sediment echo-sounding, a total of 62 deployments of various devices have been carried out during SO-225. Ten of 11 multi corers yielded sediment samples, 16 piston corer and 3 gravity corer deployments recovered altogether 131.6 m sediment cores. The sampling of the water column by CTD and multi net was successful. Foraminiferal sand and ooze dominate among the sediment samples, some cores also contained sandy clayey silt rich in foraminifers and nanno ooze. The sediment cores cover a more than 1,100 km core transect extending from the ocean floor to the north of the Manihiki Plateau to the southern foothills of the High Plateau. Preliminary studies on board showed that the SO-225 sediment sampling yielded excellent paleoceanographic archives which can be correlated along the entire core transect and dated back to Pliocene. Further preliminary results include that past climate changes significantly affected the West Pacific Warm Pool. The sediment samples also will allow to reconstruct the Plio/Pleistocene variability of equatorial currents and the Antarctic intermediate water. Four ROV dives yielded 32 rock samples from two profiles across the slopes in the northern and central part of the Manihiki Plateau (North Plateau and Danger Island Troughs). Stratigraphically controlled sampling along c. 3 km long profile reaching from 4,600 m up to 3,260 m water depth across the flank of the south-eastern foothills of the North Plateau was particularly successful. Due to a series of unfortunate circumstances beyond our control, further ROV sampling on SO-225 had to be cancelled. Instead we decided to run dredges to considerably broaden the range of samples from the Manihiki Plateau basement by dredging. Twenty-three dredge hauls have been conducted in an average water depth of 4,380 m. Of these, 20 delivered magmatic rocks, 12 volcaniclastics, 8 sedimentary rocks, and 13 Mn-Fe-Oxide crusts. Notably, some of the dredged rocks show spinifex textures indicating unusual high eruption temperatures and several dredges contained fresh volcanic glass. The recovery of fresh glass from a presumably c. 120 million years old flood basalt province is a great achievement which will enable detailed petrological and geochemical studies of the plateau forming melts. Finally, mapping of submarine volcano Monowai en route on the transit to Auckland SO-225 should contribute to a time series of maps which continuously document the evolution of the volcano. During profiling, however, a sudden and significant increase in volcanic activity hindered us in mapping the top area of Monowai.

Description: [Davy et al., 2010a] reported on pockmark observations along the Chatham Rise, offshore New Zealand’s South Island. The observed structures fall into three categories: features of approx. 150 m diameter are found in water depths of 500 m – 700 m, depressions with diameters of up to 5 km and the largest structures with diameters of up to 11 km were observed in water depth of 800 - 1100 m. Seismic sections across the pockmarks were available at only a few locations and mainly consisted of Parasound data. Multiple layers of small pockmarks could be correlated with sediment interfaces of increased amplitudes that correspond to the transitions between glacial maxima and minima. Consequently [Davy et al., 2010a] assumed that sealevel lowstands during glacial maxima caused the dissolution of gas hydrates and hence triggered the formation of pockmarks. Project SO226 CHRIMP aimed to test this hypothesis with an extended data base. Additional bathymetric coverage revealed multiple occurrences of large and medium size structures. Three working areas were selected along the Chatham Rise each representing one of the three types / sizes of seafloor depression. Area one was chosen to be centred around 178°40’E with the largest pockmark structure of up to 15 km diameter. From the extended bathymetric coverage a south-west to north-east oriented alignment of three similar structures was observed. Seismic sections show a highly variable sedimentation. Inside the structures all sediments had been fully eroded to a surface that can be mapped throughout the entire region. All observed pockmarks show a radial eroded rim to the South-West with a base that corresponds to the above mentioned erosional surface. Near vertical faults and blanking patterns are found underneath the eroded rim of the structures. Shallow bright spots with negative polarity are interpreted as indicators for free gas. Nevertheless no signs were found for active fluid venting above the structure or in the surrounding. The second area centred around 177°05’E hosts medium-size pockmarks. Five depressions were mapped, but some of them might be formed by overlapping pockmarks. Partly resedimented the structures show an eroded southern part with a sharp radial rim. Indifferent from area one a roughly 250 m wide blanking zone was found underneath one of the pockmarks. The area is imaged right above a conical shaped upward extension of a deeper sediment interface. From the 3D data the interface shows a rough topography. The conical structure and the blanking area are interpreted as an ancient feeder channel. This chimney terminates at an erosional interface, which forms the base of the seafloor depression. Multiple events of erosion, sedimentation and slumping have been identified above the erosional surface. Again water column imaging and geochemical analyses do not show indications for active methane venting within this area. The third working area was chosen to be centred 174°35’E where a large zone of small pockmarks was known from earlier mapping. A 2D seismic profile confirms the existence of stacked pockmark layers. The wide funnel shaped opening of the buried pockmarks terminates at distinguished sediment interfaces that show an increased reflection amplitude. This corresponds to the interpretation of [Davy et al., 2010a]. At greater depth the horizontal layering of the sediments is not interrupted. As with the previous two working areas there is no sign of a BSR and active methane venting could not be confirmed by water column imaging or geochemical analyses. In summary all three areas do show images of gas migration pathways of various sizes within the deeper sediments. Nevertheless active venting of fluids could not be confirmed. Therefore other models need to be developed to explain todays still sharp defined rims of the pockmark-like seafloor depressions.

Description: Cruise P453 & P458 with R/V POSEIDON aim to conduct 3D wide-angle ocean bottom recording (OBR) data during the acquisition of 3D multichannel seismic (MCS) reflection data (D. Sawyer, Rice University & T.J. Reston, Birmingham) and to analyze and interpret a highresolution densely sampled 2D OBR wide-angle profile. The primary goal of the wide-angle data will be to provide an accurate and detailed 3D P-wave velocity model for the 3D reflection data. Particularly the densely sampled 2D profile will help to determine the degree of thinning within the crust and the degree of serpentinisation of the uppermost mantle. The collection of 3D MCS data gives the unique opportunity to obtain densely sampled water column reflection data and to analyze spatial and temporal (4D) variations of the internal wave field which will yield new understanding and insights into water mass mixing processes offshore west Iberia. Contemporaneously hydrographic data will be collected to calibrate and analyze the oceanic thermohaline structures originating from the interaction between Atlantic waters and the Mediterranean Sea Outflow.

Description: The aim of R/V Alkor cruise AL438 was to investigate the assemblage composition, population density and distribution of Recent benthic foraminifera in the Elbe estuary and southern North Sea. We focused on an assessment of the present state of the ecosystems and a comparison with data from former decades. Our work resumed investigations of the Geologisch-Paläontologisches Institut of Kiel University and the Federal Hydrographic Office from 1960s till the 1980s, as well as topical studies to the west of Helgoland. We revisited the same stations and took sediment samples with historical and modern grab samplers, box corer, Minicorer and a gravity corer. These samples were accomplished with samples from new stations in order to describe the relationships of foraminiferal faunas living in the Helgoland mud area with those inhabiting the surrounding sands. The sampling was accompanied with hydrographical measurements and water sampling to document relevant environmental parameters. The foraminiferal sampling was carried out for the first time following of the FOraminiferal BIoMOnitoring group (FOBIMO) recommendations as much as possible, in order to test the practicability of the guidelines. In total, 109 deployments at 37 stations were successfully accomplished.