The General Global Map of Seafloor Bedrock Geology (seafloorgeol) shows the global distribution of seafloor bedrock, the boundaries of the continental shelf and continental slope, the axes of the oceanic ridges and other marine geological features. Sedimentary deposits are not shown. The map is based on extracts from Bouysse et al. (2010) © CGMW, and Bryan & Ernst (2008) using Esri Basemap, HERE, Garmin, FAO, NOAA, USGS, © OpenStreetMap contributors and the GIS User Community.
The CINCA marine geoscience investigations on the convergent continental margin of Chile between 19°S and 33°30'S were accomplished during three legs of RV SONNE cruise SO-104, from 22. July to 15. October 1995. The objectives of the first leg are to contribute to an understanding of the geological architecture and of the tectonic mechanism in the area of the Chile convergent zone through a geophysical assessment of the tectonic structures of the Chile continental margin and the adjacent oceanic Nazca plate. During the first leg from 22. July to 24. August 1995 multichannel seismic reflection data with BGR's new digital streamer were collected along a systematic grid with a total traverse length of 4,494 km simultaneously with the acquisition of magnetic, gravimetric, Hydrosweep and Parasound data over a total traverse length of 7,012 km. GFZ's mobile land array of 12 seismic stations recorded the air gun shots fired by RV SONNE within the CINCA area. Three seismic lines were surveyed between 32°30'S and 33°30'S in the area of the CONDOR project. Here, the surface of the downbending oceanic crust is smooth. The 5,000 m to 6,000 m deep trench floor is underlain by sediments, in excess 2,500 m thick. The inner trench slope consists of a landward thickening accretionary wedge which terminates against a body forming the base of a fore arc basin near Valparaiso. The principal area of the CINCA project extends between 19°S and 26°S and comprises the convergent continental margin, the Peru-Chile trench and the seaward adjacent part of the Nazca plate up to approximately 75°W longitude. The tectonic regime of these units of the CINCA area is very different from the tectonic system of the respective units of the CONDOR area. The Eocene-aged and sediment-starved oceanic crust of the Nazca plate becomes blockfaulted when approaching the outer trench slope break. The 50 km to 70 km wide outer trench slope is characterized by a complex system of horst and graben structures in the CINCA area probably resulting from the strong downbending. Steep fault scarps forming the flanks of the horsts reach vertical offsets varying between few hundreds of metres to 1,000 m, and locally even more. The 7,000 m to 8,l00 m deep trench is very narrow and mostly sediment-starved in the CINCA area. Morphology and architecture of the continental margin of the CINCA area are controlled by planar and listric faulting and tilted blocks of inferred continental nature, which apparently slid down into the trench. The inferred continental blocks, overlying a reflective mass, are covered by sediments of presumably turbiditic nature. An accretionary wedge is difficult to define on the seismic single channel records from the CINCA area. However, processed seismic data show a deep reflective mass underlying the downfaulted blocks of inferred continental nature. This deep reflective mass is interpreted to consist of a tectonically eroded and underplated continental crust-basalt melange forming the transition between the downfaulted continental upper plate and the subducting oceanic lower plate. Complex structural highs of still unknown origin and nature have been observed on the upper continental slope at 20°S, 24°S and 25°S. The northernmost structural high represents the seaward termination of the Iquique fore arc basin. The accuracy of the acquired gravity and bathymetric data is very good, i.e. better than 1 mGal and less than 10 m. The Chile trench is associated with strong negative gravity anomalies, and the continental margin is characterized by several positive and negative gravity anomalies of varying size and amount. The first results of magnetic modeling show, that the intensive blockfaulting of the oceanic crust across the outer trench slope causes no loss of the magnetization of the oceanic crust. The air gun shots fired by RV SONNE in 50 m intervals along 17 seismic traverses were recorded by GFZ's mobile land array in the coastal area of Chile. Good quality data were obtained out to about 100 km distance and in some cases even out to about 150 km.
The multidisciplinary marine geoscientific expedition ARK-25/3 was focused on the Greenland part of northern Baffin Bay and was aimed to acquire new geoscientific data to be used for modelling the evolution of the Greenland continental margin and its hydrocarbon prospective. The data format is Society of Exploration Geophysicists SEG Y. The cruise was performed under the direction of the Federal Institute for Geosciences and Natural Resources Hannover in cooperation with the Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven. Using 70 days of ship time onboard the research icebreaker R/V POLARSTERN a comprehensive data set was acquired along profiles extending from the deep oceanic basin in the central part of North Baffin Bay onto the Greenland continental margin in an area which was bordered by the Kane Basin in the North and Disko Island in the South. By means of multi-channel seismic, wide angle seismic, gravimetric and magnetic methods the structural inventory of the crust in the NW Baffin Bay was investigated. Additionally, heat flow data and sediment cores were collected along lines crossing the Greenland continental margin. The cores were extracted for geochemical and geomicrobiological analysis to be used for basin modelling, studying the hydrocarbon potential, and the hydrocarbon degradation by microorganisms under polar conditions. Geological sampling in the coastal area was done between Melville Bay and Washington Land. The collected rock material will be used to derive constraints on the erosion history of the coastal area. Aeromagnetic data was acquired covering a substantial part of the marine survey area to investigate magnetic signatures of the oceanic crust and the continental margin. This report summarizes the working programme and contains the documentation of acquired data and first results of the expedition.
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.
On the M/V Akademic Nemchinow multichannel seismic measurements were carried out on 34 lines with a total length of 4,000 km. The area covered was the Laptev Sea. The data format is Society of Exploration Geophysicists SEG Y.
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.
A geophysical reconnaissance survey was carried out in the Labrador Sea and Davis Strait between July and September 1977 by BGR. The data format is Society of Exploration Geophysicists SEG Y. The survey was executed on the research vessel MS Explora. The seismic, magnetic and gravity data from 5931 line-kilometers on 21 lines were recorded on magnetic tape. A 24-fold coverage technique was used with 48 seismic channels (traces), with a 2400m streamer cable, and 23.45 l airgun array. A full integrated computerized satellite navigation system (INDAS III) served as positioning system. Based on a preliminary interpretation of the seismograms, the Labrador Sea was devided into an eastern (Greenland) and western (Canadian) area, seperated by the Mid Labrador Ridge. Within the eastern part of the Labrador Sea the Pre-Cenozoic sediments show three distinct layers, traceable over the entire Greenland area of the sea. In the Cenozoic layer olisthostromes occur. The highest apparent velocity determined from sonobuoy data was 9.26 km/sec. The calculated refractor lies at a depth of approximately 13 km. The seismic section from the sediments on the Canadian side of the Labrador Sea show a uniform series of thick sediments below the Cenozoic cover. The highly disturbed basement is often masked by the multiple reflections from the seafloor. Statements about the nature and structure of the basement can only be made after processing data.
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.
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.
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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