Unter dem Motto „Rohstoffe aus dem Meer – Chancen und Risiken“ wurde am 20. Februar 2014, der dritte „World Ocean Review“ (WOR) der Öffentlichkeit präsentiert. Der WOR 3, herausgegeben von der gemeinnützigen Organisation maribus gGmbH und mit Unterstützung der Zeitschrift »mare«, des International Ocean Instituts (IOI) und des Exzellenzclusters »Ozean der Zukunft«, beschreibt ausführlich die bekannten metallischen und energetischen Rohstoffe in den Ozeanen und beleuchtet die Chancen und Risiken des Abbaus und der Nutzung von Rohstoffen. Der neue Report liefert Fakten über die Menge an bekannten Öl- und Gasvorkommen und der festen Gashydratvorkommen unterhalb des Meeresbodens. Ferner geht es um das Potenzial von mineralischen Rohstoffen wie Manganknollen, Kobaltkrusten und Massivsulfiden. Darüber hinaus thematisiert der WOR 3 die Verantwortung der internationalen Staatengemeinschaft für einen umweltverträglichen Abbau und die völkerrechtliche Herausforderung, für eine sozial gerechte Verteilung der Ressourcen in internationalen Gewässern zu sorgen.
From 19th November to 19th December 2004 BGR conducted a marine geophysical cruise between 34°S and 36°S off Uruguay and between 46°S and 50°S off Argentine. The main research objective was to contribute to a better understanding of the initial breakup and the early opening of the South Atlantic. In continuation of our former work on the South Atlantic continental margins off Argentina, Brazil, Uruguay, Namibia and South Africa marine geophysical research (multi-channel seismics, refraction-/wide-angle reflection seismics, magnetics and gravity) was performed in close cooperation with the Argentine and Uruguayan authorities Comisión Nacional del Límite Exterior de la Plataforma Continental (COPLA) of Argentina and Servicio de Oceanograficia, Hidrograficia y Meteorologia de la Armada (SOHMA) of Uruguay. Multi-channel seismic lines with a total length of 3,754 km and additional 3540 km with the other geophysical methods were acquired . Along two lines refraction-/wide-angle reflection seismic work was carried out. The preliminary analyses of the new seismic data show different images of the crustal structures between Uruguay and southern Argentine with regard to the distribution and volume of offshore volcanic rocks (seaward dipping reflector sequences, SDRS) along the South American Atlantic margin. On the northern profiles between 34°S and 36°S one single well developed wedge of SDRS is present. Although the landward termination (‘feather edge’) on most of the lines is masked by multiples the average total width of the wedge across the margin seems to be 90 – 100 km and is very constant for this margin segment. This is strong contrast to the results from former cruises (BGR87, SO85 and BGR98) which covered the area between 38°S and 45°S. There, the SDRS showed distinct multiple wedges which in some places extend over 120 km across the continental slope. The investigation of the sedimentary section yielded that in the area off Uruguay widespread bottom simulating reflectors (BSR) are present. This indications for stable gas hydrates cover a total area of 7000 km2. One major aim of the cruise was to cover the transition between a volcanic passive margin and a non-volcanic passive resp. sheared margin. This was accomplished in the southern part of the investigated area. Two EW-trending profiles across the Argentine shelf into the Argentine Basin still show indications for SDRS but these structures are only 25 – 30 km wide. The profiles which extend from the NE to the SW crossing the Agulhas-Falkland Fracture Zone (AFFZ) onto the Falkland Plateau show the typical trend of a sheared margin. At the northern rim of the Falkland Plateau a set of small pre-rift half grabens were found indicating pre-rift extensional tectonic phases. The magnetic data in the area off Uruguay show lineations which are preliminary interpreted as chrons M0 to M3. This might indicate that the first (oldest) oceanic crust was created at a time around the magnetic polarity reversal between the normal interval M4 and the reversed interval M3 (126-127 Ma). Together with existing data from previous cruises this indicates that the breakup of the South Atlantic started further South because there magnetic chrons back to M9 (130 Ma) were identified. In the southernmost part of the margin at 47°S only the magnetic lineations M0 to M4 were identified in the oceanic domain Nevertheless, it is likely that between M4 and the assumed position of the continent ocean boundary/transition (COB/COT) older oceanic crust exists that for some reasons does not show correlatable lineations. The the free-air gravity map is dominated by the main topographic and structural features in the survey area. Rifted continental margins are characterized by prominent free-air gravity anomalies elongated parallel to the ocean-continent transition. The continental slope is considerably steeper in the North off Uruguay than in the South and thus the gravity high is much more pronounced in the North than in the South. The simple Bouguer anomaly map also shows the difference between the more gentle and wider continental slope in the South and the steeper slope in the North. The lowest Bouguer gravity values are found in the area of the basins on the continental shelf. Especially the Salado Basin in the prolongation of the Rio de la Plata and the Colorado Basin at about 40°S are indicated by Bouguer gravity anomaly highs. The interpretation by forward density modelling shows, however, the presence of SDRS units in the North of relative high density in the area of the continental slope. Whereas the modelling shows no indications for such volcanic bodies in the South. Although the MCS data indicate a small SDRS wedge but this body may be too small to cause an anomaly.From 17th April to 6th June 2003 BGR conducted a marine geophysical cruise between 30°S and 38°S off the Atlantic coast of South Africa. The main research objective was to contribute to a better understanding of the initial breakup and the early opening of the South Atlantic. In continuation of our former work on the South Atlantic continental margins off Argentina, Brazil, Uruguay and Namibia marine geophysical research (multi-channel seismics, wide-angle refraction seismics, magnetics and gravity) was performed in cooperation with the Petroleum Agency South Africa (PASA). Multi-channel lines with a total lenght of 3,260 km, and additional 1,365km, with the other geophysical methods were acquired. Combined onshore/offshore refraction seismic work in cooperation with GeoForschungsZentrum Potsdam (Germany) and the Council for Geoscience (South Africa) was also part of the program.
Within the frame of the comprehensive SPOC project (Subduction Processes off Chile) the SONNE cruises SO161 Leg 2 and 3 have been conducted between October 16th and November 29th, 2001, off central Chile between 28° and 44° S. In that period some 5,300 km were surveyed with multichannel seismic (MCS) reflection, magnetic, gravity, high-resolution bathymetric and echographic methods. In addition, approximately 3,900 km were surveyed with the same spectrum of methods but without MCS. The total number of 2D profiles was 48. Target was the variation of the subduction properties between the convergent oceanic Nazca and continental Southamerica plates and the different conditions that might influence the subduction process as there are: (1) age of the oceanic crust, (2) its structure and composition, (3) its sedimentary cover, (4) its thermal state, (5) the subduction angle and obliquity, and (6) the terrigenous sediment afflux from the continent. Furthermore, special focus was given to the subduction front, the subduction interface, the structure of the slope as well as to the forearc basin structure and history, and the general distribution of gas hydrate indicating bottom simulating reflectors (BSR's). The results are to be compared with previous studies of the Chilean active margin, e.g. CONDOR (SO 101 and 103) and CINCA (SO 104). The SPOC target area was subdivided into three sub-areas A,B and C. One area was chosen for a detailed survey by aid of a narrowly spaced grid and for a close link with a lot of partners. This area is characterized by a distinctly different margin type south of it is assumed. Moreover, the subducting portion of the aseismic Juan Fernandez Ridge is located in that area representing another important target of the survey. Advantageous conditions enabled the survey of an east-west profile south of Chiloé Island, providing a section through the submerged coastal Cordillera into the flooded longitudinal valley. Some results of Leg 2 and 3 are: In all areas A, B and C no subduction bulge (outer high) in the oceanic crust was visible perhaps due to the shortness of the profiles. The sedimentary cover of the oceanic crust is exceptionally thin, and the crustal thickness is generally quite "normal" with around 7 km derived from relatively weak Moho reflections. In area B a so far magnetically unmapped region was filled providing reliable ages of the oceanic crust, and suggesting that the Challenger Fracture Zone abruptly terminates west of the area of investigation. The survey in area C yielded valuable information on the trench morphology. The so far unique MCS profile south of Chiloé island shows a very wide trench and allows to extrapolate the general conditions encountered an area A southward to approximately 44° S. It can be stated that the situation is in sharp contrast to the basin structures detected by industry profiles further north in the Golfo de Corcovado.
Between 08.11.1999 and 02.12.1999 the active convergent margin off Costa Rica was investigated using the S/V Professor Polshkov. The cruise had three scientific targets. Several seismic profiles in the dip-direction of the subduction zone were acquired to map the general variability of the accretionary wedge. Near the Jaco Scarp, a dense net of seismic profiles using a smaller seismic source should deliver information about the amount of gas hydrates within the shallow sub-surface. In an area of this wedge south of the Quepos Plateau densely spaced seismic lines were measured to prepare an ODP campaign (which was finished in 2011 as IODP Expedition 334).
The main objectives of the BGR cruise BGR01 POPSCOMS (Properties of a Gas Hydrate Province on a Subduction-Collision Related Margin off Sabah) off Sabah/Malaysia with M/V AKADEMIK NEMCHINOV from 4th November to 3rd December 2001 in co-operation with PETRONAS Malaysia are the research on (1) Marine Methane Gas Hydrates: Detection, distribution and formation; relation to the adjacent highly productive "conventional" gas province in the specific tectonic setting of the collisional belt off Sabah. (2) Tectonic development of the (accretionary) margin off Sabah: Improve the tectonic stratigraphic hypothesis of the subducted Proto-South-China-Sea and continental crust under the accretionary wedge, respectively in the subducted plate. Open questions and targets of the survey: Within the help of the already existing magnetic data and other seismic measurement methods (e.g. special refraction seismic with ocean-bottom hydrophones [OBH], which presumably is an exellent and adequate method) we try to discern between oceanic and continental crust in the subducted plate, to investigate the nature of the transition and get information on the subduction angle. This is important in relation to the Cagayan Ridge (Sulu Sea) that is interpreted as an island arc that is related to the subduction of the proto-South China Sea. Another aim was to enable the determination of seismic anisotropy, distribution of BSR's and hydrates in the area and their v(p) to v(s) ratios. Are the gas hydrates related to the adjacent highly productive "conventional" gas province? What is the structural character of the transition zone between the hydrate province and the adjacent conventional gas bearing province further up-slope? Conversely, are there indication for a possible deepwater source? Can initial conclusions be drawn regarding their biogenic or thermogenic origin? Is there an impact of sedimentation conditions, compressional behaviour (e.g. at active margins) and/or structural properties on the genesis and stability of gas hydrates and BSRs (Bottom Simulating Reflectors)? How do the findings under different conditions compare in that regard? Which are the favorable conditions for the genesis of gas hydrates, and can they be detected by geophysical methods even if there are no BSR's? The findings are expected to provide a contribution to the assessment of the deepwater hydrocarbon potential along the continental margin off Sabah. Results: In the study area the BSRs were identified on the base of their polarity reversal with respect to the seafloor and when they transect reflectors from the strata. The widely distributed BSRs along the seismic lines of the survey deliver an indirect indicator for the presence of gas hydrates in the study area (BSR's in post Miocene sediments). The BSR depths below seafloor vary between 250 and 350 m. Differences in the reflection coefficient of the BSRs are mainly related to the amount of free gas beneath the Gas Hydrate Stability Zone.