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  • The Sonne Cruise SO122 was carried out by the Federal Institute for Geosciences and Natural Resources (BGR, Hannover) from 3rd August to 9th September 1997, in cooperation with GEOMAR (Kiel), the National Institute of Oceanography (NIO, Karachi) and the Hydrocarbon Development Institute of Pakistan (HDIP). During the joint project with R/V SONNE the Makran accretionary wedge off Pakistan should have been investigated in detail with multi-channel reflection seismics, magnetics and gravimetry. Intense fishery offshore Pakistan forced a change of the area of investigation to the south with the following objectives: investigation of the crustal structure and occurrence of the bottom simulating reflector (BSR) in the Makran accretionary wedge; investigation of the structure of the Murray Ridge System in order to reconstruct the geodynamic evolution of the eastern Indian Plate margin; determination of the origin of the crust underlying the Indus Fan and reconnaissance of the sedimentary history of the Indus Fan in order to reveal the uplift and erosion history of the Himalayas.

  • The major pre-alpine tectonic lineaments as the Glückstadt Graben and the Avalonia-Baltica suture zone run across the southern Baltic. The BalTec-expedition aimed at the gapless imaging of these fault systems from the seafloor down to the Paleozoic basement. Scientifically the expedition was motivated by two hypotheses. We postulated that advances and retreats of ice-sheets during the glacials initiated and reactivated faulting of the Post-Permian succession, thereby generating several kilometers long near-vertical faults and anticlines. We further postulated that – in contrast to the generally accepted text book models – deformation of the initially up to 1800 m thick Zechstein salt started already during salt deposition as the consequence of salt load induced basin subsidence and resulting salt creep. The profile network was further designed to allow for linking the stratigraphy between previously generated local underground models in the frame of the TUNB project. Altogether we collected 62 reflection seismic profiles of an entire length of 3500 km. Parasound and multibeam data were collected along 6000 km each. The marine gravimeter collected data along the entire ship’s track of 7000 km. Two wide-angle reflection / refraction profiles have been measured in order to image the deep structure of the Teisseyre-Tornquist Zone off Poland and to investigate North-South striking fault systems in the Bay of Kiel.

  • On the F.S. POLARSTERN cruise ANT-IV/3 (6th December, 1985 - 13th March, 1986) multichannel seismic measurements were carried out in parallel with magnetic and gravimetric measurements on 33 lines with a total length of 6,263 km. 3,350 km of the multichannel seismic lines have been processed aboard. The geophysical studies were designed to investigate the structure and geological development of the Weddell Sea continental margin from meridians zero to 60°W, and to define suitable and safe drilling locations for Leg 113 of the Ocean Drilling Program. The main results of the geophysical studies are: (1) The discovery of an approximately N50°E trending failed drift basin, following the trend of a negative magnetic anomaly and a positive gravity anomaly. (2) The discovery of two extensive wedge-shaped and symmetric basement units around a failed drift basin between longitudes 40°W and 20°W. The seismic characteristics, i.e. seismic velocities of 4 km/s and an internally divergent pattern of reflectors suggest that both wedges are formed from extrusive/intrusive volcanic rocks. (3) The confirmation of a major plate tectonic boundary trending approximately N80°E to N60°E, i.e. the EXPLORA-ANDENES escarpment. (4) The confirmation of a glaciogenic progradational wedge beneath the shelf of the Weddell Sea Embayment, made up of several thousand metres of sediments. (5) The definition of 13 suitable and safe drilling locations for ODP-Leg 113.

  • 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).

  • Main target of the project GIGICS (Cooperative German-Indonesian Geoscientific Investigations in the Celebes Sea) is the investigation of the internal crustal structure and the plate tectonic evolution of the Celebes Sea and its active continental margins off Mindanao and Northern Sulawesi. These investigations were carried out during the cruise SO98 of RV SONNE by the Federal Institute for Geosciences and Natural Resources (BGR), Hannover; the German Research Centre for Geosciences (GFZ), Potsdam; the GEOMAR, Kiel; the Institute of Oceanography (IfM), Hamburg; the Mines and Geoscience Bureau, Manila; the Agency for the Assessment and Application of Technology, Jakarta, and the Institute of Oceanography, Wormley. The cruise SO98 consisted of three legs of two weeks duration and one leg of four weeks duration. The total amount of data acquired during the cruise were: - 3,300 km of multichannel reflection seismics, - over 6,800 km of gravimetric and magnetic data and approximately 10.000 km of swath bathymetric and sediment echosounder data, - 3 wideangle-/refractionseismic profiles, each of 120 - 150 km length, - geological, geochemical sampling and oceanographical measurements at a total of 37 stations. During the cruise SO98 a widespaced but regular grid of magnetic and gravimetric profiles were acquired in the eastern part of the Celebes Sea from which up to then reliable data were very sparse. WEISSEL (1980) recognized in the western Celebes Sea WSW-ENE striking magnetic lineations, which he interpreted as chrons 18 - 20 (39 - 43 Ma according to the timescale of HARLAND et al. (1990)). The data from cruise SO98 show that there is no continuation of these anomalies to the east. In the eastern part the magnetic field of the Celebes Sea is less clear and much more disturbed. Nevertheless, E-W-striking anomalies are recognizable. Because amplitudes of local magnetic anomalies are higher than the lineations, the correlation of these lineations with the magnetic reversal scale is still somewhat ambiguous. The gravity map compiled from the measured gravimetric data shows elongated positive anomalies in the eastern part of the Celebes Sea. Exceptions occur at the deep sea trenches off North Sulawesi (North Sulawesi Trench) and Mindanao (Cotabatu Trench) and at the Sulu Archipelago where strong negative gravity anomalies were found. A remarkable NW-striking gravity high of up to 60 mgal was found in the central eastern part of the Celebes Sea. Gravimetric modelling suggests that this high can be correlated with the gravimetric effect of the Molucca Sea Plate subducting from the east under the Sangihe Arc. The reflection seismic data from the northern part of the Celebes Sea show indications for a juvenile subduction of oceanic Celebes Sea crust under the Sulu Archipelago. The oceanic crust bends down towards the Sulu Arc with angles between 2° and 5° and the sedimentary sequence above is deformed indicating a compressional stress regime. With the exception of two linear arranged seamount-like basement highs the Celebes Sea is dominated by two different oceanic crustal types showing distinct differences in the topography. The first one is showing a very similar reflection seismic pattern as it is found for oceanic crust of the Atlantic (HINZ et al., 1994). This type is characterized by a small-scale block-faulted relief of the top basement and a low reflectivity in lower crustal levels typically related as to be accreted at slow to intermediate spreading ridges. This type is found in the western, northern and southern part of the investigated area. In the eastern and especially in the southeastern part the igneous crust shows a very different image. The reflection of the top of the basement is less distinct and of lower frequency. The relief is very much smoother than in the previous type. This reflection seismic image indicates a volcanic/magmatic overprinting of the oceanic crust in this part of the Celebes Sea. Another target of cruise SO98 was the area of the active continental margin off North Sulawesi and its accretionary complex. The internal structure of the accretionary complex should be investigated to decide whether this active margin is also of the 'splinter-type' or not. During former geophysical cruises with RV SONNE oceanic crustal splinters were discovered in the accretionary wedges of the Sulu Sea and off Costa Rica (e.g. HINZ et al., 1991). From our reflection seismic measurements this active continental margin is morphologically subdivided into three units and consists of two accretionary complexes of different internal structural style: the lower and middle continental slope is underlain by an intensively thrusted, sedimentary accretionary wedge. This wedge was most probably formed during the last 5 Ma. Landward of this wedge an older and seismically very complex accretionary unit is present which is overlain at its landward termination by a sedimentary fore-arc basin. Within this older accretionary complex, units with a strong, low frequency reflection pattern were found which are interpreted to represent crustal splinters of igneous oceanic or ophiolitic nature. This interpretation is supported by our gravity and magnetic data. The magnetic profiles show an increase of the magnetic field towards the north arm of Sulawesi across the continental margin. This increase of the magnetic field suggests an increase of magnetized material within the older accretionary wedge towards the northern arm of Sulawesi where ophiolites are emplaced. During the interpretation of the reflection seismic data of the project GIGICS BSR's (bottom simulating reflectors) were discovered for the first time along the active continental margin of North-Sulawesi. BSR's are the seismic expression of a velocity decrease at the bottom of a gas hydrate zone. The distribution and depth of the BSR's correlates with the geochemical and geothermal results. Radiometric age dating and geochemical analyses from pillow basalts of a seamount from the southeastern Celebes Sea indicate hot-spot activity in this part of the Celebes Sea during or shortly after the formation of the oceanic crust approximately at 43 Ma ago. Three NW-striking ridges or seamount-chains in the northeastern Celebes Sea were mapped and investigated in detail. They are thought to represent a wrench fault system extending through the northeastern Celebes Sea. At the flank of one of these ridges a strongly alterated plagioclase-olivine basalt sample was dredged which was overlain by non-fossiliferous clay stone. A similar lithostratigraphic sequence was drilled during ODP leg 124 (RANGIN et al., 1990). The geochemical composition of these basalts is different from typical MORB. The existence of a large crustal splinter within the accretionary wedge off southwestern Mindanao obviously is responsible for a high thermal conductivity which in turn could have enhanced heat flow (108.1 mW/m2) and methanogenesis (405 ppb). The heat flow of 103.0 mW/m2 at the deformation front of the Mindanao wedge and the high methane concentration of 5.555 ppb suggests tectonically induced fluid transport within the wedge. High methane concentrations between 8.044 and 49.006 ppb at the lower slope off Sulawesi and in the North Sulawesi Trench are accompanied by high heat flow values of up to 100.5 mW/m2. Heat flow is significantly lower upslope (31.3 mW/m2). This general heat flow distribution pattern is seen over a large portion of the accretionary wedge. The elevated heat flow values and high methane concentrations near the deformation front most likely result from heat transport by fluids squeezed out from vertically and laterally compacting sediments. The reduced heat flow towards the coast is compatible either with a cooling effect of slow subduction of the oceanic crust, or stacking of cool slabs of compacted sediments. A subduction of oceanic crust with a heat flow around 60 mW/m2 over a period of more than 3 million years would have produced the low heat flow values of the upper slope if the wedge consists of claystone with a low thermal conductivity (1.2 - 1.7 W/mK). Even in the low-heat flow area isolated fluid venting is possible. Lateral variations in the heat flow pattern (e.g. broadening of the anomalies in the west) may be due to different thermal regimes within the subducted crust.

  • The 3rd cooperative BGR/SMNG Arctic cruise was designed to acquire new scietific data for a better understanding of temporal and spatial lithospheric variations during rifting and its influence on the tectonic and structural evolution of the continental crust of the Laptev Sea undergoing extension since at least the Early Tertiary, and for tackling open questions regarding the evolution of the submarine permafrost zone. Although conditions for seismic measurements were worse in 1997 than in 1993 and 1994, along 4,622 km of seismic traverses reflection seismic data and wide angle reflection/refraction data from 23 OBH-(ocean bottom hydrophone) stations were collected in the Laptev and East Siberian Sea. The most prominent rift basin is the Ust' Lena Rift, which is at least 300 km wide at latitude 75°N. The Cenozoic sedimentary cover exceeds 3 km everywhere, increasing up to 14 km at two locations. In the northern part of the shelf, the complex mainly N–S-trending Anisin Basin has a basin fill of up to 10 km thickness. The New Siberian Basin which is located in the northwestern part of the study area shows an up to 9 km thick graben fill. The Laptev Horst crust is locally subdivided into several tilted blocks by deep-reaching faults and there are several half grabens of smaller extent which divide the Laptev Horst into three parts: the North, the South and the East Laptev Horst. A major west dipping listric fault of at least 250 km length separates the Laptev Horst from the Ust' Lena Rift. Results from the seismological investigation indicate that recent extension is concentrated within the narrow rift basins of the eastern Laptev Sea. From wide-angle reflection/refraction seismic measurements the seismic velocities of the crustal layers were estimated along five profiles. The layers with velocities of up to 3.5 km/s apparently consist of predominantly Cenozoic sediments. The sedimentary section showing relatively high seismic velocities of 4.5 to 5.2 km/s might be interpreted as Late Paleozoic to Mesozoic deposits or overcompacted/cemented syn-rift deposits. In the eastern shelf area a layer beneath the acoustic basement was interpreted to represent Ordovician to Early Mesozoic carbonates. The lower crust in the area under study shows relatively uniform seismic velocities of about 6.0-6.8 km/s and the velocities estimated for the crust-mantle transition are in the range of 8.0 to 8.2 km/s. The origin of a several 100 m thick layer with a relative high velocity of 3 to 3.5 km/s directly beneath the seafloor was inferred as sub-sea permafrost.

  • In July/August 1988 a seismic reconnaisance survey was carried out with F.S. Polarstern on the perennially ice covered East Greenland shelf between latitudes 73°N and 81°N. The data format is Society of Exploration Geophysicists SEG Y. 14 reflection seismic lines with a total length of 2.016 km and 12 sonobuoy refraction profiles were recorded. The following results were obtained: •On the wide Holm Land shelf province north of 79°N three possible Cretaceous rift basins were observed. •A buildup of layered extrusive basaltic rocks forming a wedge of seaward dipping reflectors underlies the Holm Land continental slope. •On the Northeastern Greenland shelf province the existence of a wide sedimentary basin was demonstrated north of 76°N. •South of 76°N four volcanic structures from the continent to ocean were observed: The zone of Early Tertiary plateau basalts (zone I) that occur landward of an escarpment, a flat lying basaltic flow unit immediately seaward of the escarpment (zone II), an elongate wedge of seaward dipping reflectors (zone IIIa), a basaltic flow unit which in places shows seaward dipping beds of short length (zone IIIb), and the oceanic crust. •Dyke swarms and intrusions of inferred Neogene age were recognized at several locations.

  • During the cruise with S.V. EXPLORA within the Ross Sea on the second marine-geophysical expedition of the Federal Institute for Geosciences and Natural Resources (BGR) to Antarctica, in total 6,745 km of magnetic, gravity and digital reflection seismic lines and additionally 1,400 km gravity lines were acquired in the period from January 10th to March 2nd 1980. On 43 stations sonobuoy refraction measurements have been carried out. The main results are: (1) In the eastern part of the Ross Sea Shelf two striking discontinuities have been identified in the reflection seismics representing gaps in the sediments at the turn-over of the Upper Miocene to the Pliocene (ca. 7 mio years B.P.) and between the Middle and Upper Miocene (ca. 11.5 mio. years B.P.) according to results of DSDP boreholes. (2) In the southern part of the Ross Sea Shelf the basement is uncovered at depths over 700m due to a thrust of the shelf ice recently. (3) A structural unit extends alongside the meridian of 180° separating the Ross Sea into two different geologic regions. This unit is characterised by two basement highs with seismic velocities exceeding 5 km/sec. (4) In relation with the GANOVEX expedition two profiles have been measured off northern Victoria Land which indicate two large faults with a faulting amount of 2 km. Another area is characterised by intrusive and volcanic bodies.

  • The cruise leg MSM09/3 was conducted as a cooperative project between the Alfred Wegener Institute for Polar and Marine Research (AWI), the Federal Institute for Geosciences and Resources (BGR), the Geological Survey of Denmark and Greenland (GEUS) and Dalhousie University. The data format is Society of Exploration Geophysicists SEG Y. A geophysical survey covered areas of Baffin Bay and Davis Strait between Greenland and the Canadian Baffin Island. A component of the IPY 2007/08 Lead Project Plate Tectonics and Polar Gateways in the Earth System (PLATES & GATES), this project DAVIS GATE is aimed to develop a tectonic and sedimentary reconstruction of the opening process of this oceanic gateway. Baffin Bay and Davis Strait play an important role in the shallow water exchange from the Arctic to the Atlantic Ocean. The plate-tectonic evolution as well as the magmatic history of this region has been sparsely known and required a careful geophysical investigation in order to construct a set of gridded detailed paleotopographic maps for a complete geodynamic reconstruction of this gateway. With a set of three seismic refraction/wide-angle reflection profiles, using ocean-bottom seismometers on 62 stations, as well as multi-channel reflection seismic recordings with a 3000-m long streamer, data were acquired from the sedimentary cover to the deep crust and even from parts of the uppermost mantle. Additional seismic data supplement these profiles and provide insights into the structures of the basement and dominant fault zones such as the Ungava fault system. A parallel running magnetic survey aimed to resolve the temporal evolution of the oceanic crust of Baffin Bay. The extension and subsidence of the continental and transitional crust in the Davis Strait and the evolution of oceanic crust in the Labrador Sea and Baffin Bay could be investigated with dataset to which continuously recorded gravity anomaly data and sub-bottom profiler data also contribute. This dataset provides the basis of geometrical and physical properties of the crust required for a realistic geodynamic model which will describe the break-up and the ocean basin evolution between Greenland and Canada in terms of detailed paleo-topography.

  • Im Rahmen des weit gespannten SPOC-Projektes (Subduction Processes off Chile) wurden zwischen dem 16.10. und 29.11.2001 vor Zentralchile zwischen 28° und 44°S die SONNE-Fahrten SO161 Leg 2 und 3 durchgeführt. In diesem Zeitraum wurden etwa 5.300 km mit vielkanal-/reflexionsseismischen (MCS), magnetischen, gravimetrischen, hochauflösenden bathymetrischen und echographischen Methoden vermessen. Hinzu kamen etwa 3.900 km mit denselben Verfahren, jedoch ohne MCS. Die Gesamtzahl der 2D-Profile betrug 48. Auf vier Ost-West-Traversen wurden amphibische (d. h. in Land-/See-Kombination) weitwinkel-/refraktionsseismische Beobachtungen durchgeführt. Darüber hinaus wurden die ausgesandten marin-seismischen Signale an Land von einem zweidimensionalen seismischen Mobilstationsnetz, das zwischen 37° und 39°S aufgestellt war, aufgezeichnet. Ziel der Untersuchungen war die Veränderlichkeit der Subduktionseigenschaften zwischen den konvergenten Nazca (ozeanisch) und Südamerika (kontinental) Platten sowie die verschiedenen Begleiterscheinungen, die den Subduktionsprozess beeinflussen können wie: (1) Alter der ozeanischen Kruste, (2) ihre Struktur und ihr Aufbau, (3) ihre sedimentäre Bedeckung, (4) ihr thermischer Zustand, (5) Subduktionswinkel und -schiefe sowie (6) der terrigene Sedimentzufluss von der Kontinentseite. Weiterhin waren die Subduktionsfront, die Subduktionsflächen, die Struktur des Kontinenthanges ebenso wie Struktur und Entwicklungsgeschichte der Forearcbecken und die Verteilung von Gashydrat anzeigenden "Meeresboden simulierenden Reflektoren" (BSRs) Gegenstand der Untersuchungen. Die Ergebnisse sollen mit früheren Studien am aktiven chilenischen Kontinentalrand in Vergleich gesetzt werden, z. B. mit CONDOR (SO101 und 103) und CINCA (SO104). Das SPOC-Zielgebiet war in zwei Untergebiete A und B unterteilt. A erstreckt sich von 36°S bis 40°S und war ausersehen für eine detaillierte Untersuchung mit Hilfe eines engabständigen Profilnetzes sowie für eine enge Verbindung mit den landseitigen Aktivitäten des Sonderforschungsbereichs SFB 267 ("Deformationsprozesse in den Anden") der Deutschen Forschungsgemeinschaft (DFG), des GeoForschungsZentrums Potsdam, der FU Berlin und anderer Partner. Dieses Gebiet ist charakterisiert durch einen deutlich anderen Kontinentrandtyp und andere Eigenschaften des Tiefseegrabens als die Gebiete nördlich davon. Gebiet B wurde ausgewählt, weil in diesem Bereich eine Übergangszone oder eine Grenze zwischen dem subduktionserosiven Kontinentrandtyp vor Nordchile und dem Typ, der im Süden vorherrscht, vermutet wird. Darüber hinaus tritt in dieser Region der Juan Fernandez Rücken in die Subduktionszone ein, der ebenfalls ein wichtiges Erkundungsziel des Projektes ist. Günstige Umstände erlaubten die Vermessung eines Ost-West-Profils südlich von Chiloé zwischen 43°S und 44°S, das über die abgesunkene Küstenkordillere bis in das geflutete Valle Longitudinal verläuft. Dieses Gebiet wird als "C" bezeichnet. Anhand einer ersten an Bord durchgeführten Interpretationen ergeben sich für Fahrtabschnitt 2 und 3 folgende Resultate: In beiden Gebieten A und B konnte kein "Subduction Bulge" (Outer High) festgestellt werden. Möglicherweise reichen die Profile hierfür nicht weit genug. Die sedimentäre Bedeckung der ozeanischen Kruste ist sehr dünn und die ozeanische Krustendicke im allgemeinen sehr "normal" mit ungefähr 7 km, abgeleitet aus relativ schwachen Moho-Reflexionen. In Gebiet B konnte eine bis jetzt magnetisch unkartierte Region vermessen werden, woraus sich recht sichere Alter für die ozeanische Kruste ergeben sowie starke Anhaltspunkte dafür, dass die Challenger Fracture Zone westlich des Untersuchungsgebietes aufhört. Die Arbeiten im Gebiet "C" erbrachten wertvolle Information über die Trench-Morphologie und das bis jetzt einzige MCS-Profil südlich von Chiloé, welches einen sehr breiten Trench anzeigt und weitgehend die Extrapolation der Eigenschaften, die im Gebiet A angetroffen wurden, nach Süden bis etwa 44°S erlaubt.

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