The previous BGR-cruises with RV AURELIA in 2003 and 2004 were designed to collect a grid of seismic MCS-data which should enable us to get a high-resolution overview over the upper 1 s TWT of the sediments of the German North Sea sector. The data format is Society of Exploration Geophysicists SEG Y. Together with the previously acquired data these new data should help to extend our knowledge of the Late Tertiary and Quaternary evolution of the German North Sea Sector. For the current measurements under the scope of the DFG-funded project RE2424/1-1 ‚Nordsee’ the research vessel RV HEINCKE was made available by the ‘Senatskommission für Ozeanographie’ of the DFG. During the cruise a total ca. 1400 km of high quality MCS lines were surveyed and simultaneously measured by a sediment echosounder system that enabled additional profiles during transits with speeds > 5 kn. The BGR high-resolution multichannel seismic reflection system consisting of a GI-Gun (0.8 l) and a 300 m streamer with 24 channels and a sediment echosounder type SES 2000 standard by Innomar, Rostock. While the BGR-seismic system was used to observe the shallow subsurface down to 2 s TWT penetration depth, the sediment echosounder with a penetration depth of several meters was primarily intended to identify sampling positions for the deployment of the BGR vibration corer during the succeeding Leg 2. Additionally, the echosounder system enables the relationship to the highest-resolution multichannel seismic measurements of the group of the University of Bremen on FK SENCKENBERG. All seismic records were processed onboard for the quality control and for a first interpretation.
Processed seismic data from Baltic Sea with research ship M/V Polar Queen.The data format is Society of Exploration Geophysicists SEG Y. During the period from 14th to 28th of April 1996 BGR and GFZ chartered the Norwegian vessel M/V POLAR QUEEN for testing the new and updated marine seismic equipment of the BGR and for acquiring seismic lines. The operating area was the North Sea and Baltic Sea. The geophysical lines in the Baltic Sea were chosen as extended onshore DEKORP lines to evaluate the deep structure of the south western part of the Baltic Sea. For the seismic profiles a tuned source array consisting of 20 air guns in two linear strings with a total volume of 52 l was used. The recording length was 26 s, the sample rate 4 ms and the shot interval 30 s. This time triggering for the shot release was chosen, because all shots were also recorded onshore by seismic stations for wide angle/refraction acquisition (GFZ). During this leg 810 km reflection lines and additional 230 km pure shooting could be surveyed. The preliminary interpretation of the seismic single traces was restricted on the ship to the upper time range. The main structures in the southern Baltic Sea could be evaluated. A full interpretation especially of the deeper part is only possible after a processing due to the nature of the single traces and the S/N ratio.
The dataset comprises the locations of outcrops with respective information on the lithology, stratigraphy, rock age and tectonic data collected during the CASE expeditions. The data attributes include stereographic projections and sketches of tectonic structures derived from the outcrop data. At the end of the 1980s, BGR initiated the research program Circum-Arctic Structural Events (CASE) to reconstruct the plate tectonic processes during the evolution of the Arctic Ocean using terrestrial data from the surrounding continental margins. One of the scientific questions of the CASE programme is as simple as it is complex: How did the Arctic Ocean, this large basin between the Eurasian and North American continental plates, develop? There are still no conclusive answers to this question in terms of plate tectonics. In contrast to the marine expeditions of geophysicists in the Arctic Ocean, geologists on land along the various coastal areas of the Arctic Ocean can directly touch, examine and map rocks, structures, folds and fault zones and determine the respective ages of the movements. This makes it possible to directly compare rock units and deformation zones on different continental plates and thus also to reconstruct when these plates collided, how long they remained next to each other and when and how they separated again. Since the inception of BGR’s Arctic research, the primary focus and research areas have been along the continental margins between Spitsbergen and the Canadian Arctic Archipelago via Greenland, to the Yukon North Slope on the border with Alaska. On the opposite side of the Arctic Ocean, there have been expeditions to Yakutia, the mainland areas near the Laptev Sea, the New Siberian Islands and to the Polar Ural with Russian partners. An important method for the interpretation of the geological evolution of the Arctic is the examination of tectonic structures (faults, folds, cleavage etc.), the determination of the kinematics and the age of the tectonic movements.
Reconnaissance surveys were carried out in 1975 within the framework of the BGR program "Geoscientific studies in the North Atlantic". The data format is Society of Exploration Geophysicists SEG Y. The areas covered were the continental margin of Spitsbergen, the Barents Sea and the Norwegion continental margin. On the vessel LONGVA (30th August, 1975 - 29th September, 1975) multichannel seismic measurements were carried out on 37 lines with a total length of 2,815 km.
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 late Tertiary and Quaternary development of the German EEZ was systematically inverstigated by seismic profiling. The data format is Society of Exploration Geophysicists SEG Y. For that survey the privately owned motor vessel AURELIA was chartered for a period of 24 days from the 16th of September to 10th of October 2003. A more or less equidistant E-W and N-S grid of profiles with a length of 2500 km was surveyed by high-resolution multichannel seismic system. A 0.82 litre GI-Gun was employed every 12.5 m and the reflected signals were recorded by a 300 m long streamer. Simultaneously a deep-towed HUNTEC-Boomer or a GEO-Sparker was run (150km/620km). All seismic records were processed onboard for the quality control and for a first interpretation.
On the MS Explora (1st September, 1976 - 29th September, 1976) multichannel seismic measurements were carried out on 44 lines The area covered was the Barentssea. The data format is Society of Exploration Geophysicists SEG Y.
The main purpose of the cruise SO75 from 14th October to 12th November 1991 was to test the new instrumentation of the SONNE and the ship itself for the needs of marine geophysics. The second purpose was the investigation of the crustal structure of the Atlantic Ocean from the Madeira-Torre Rise to the continental slope of Portugal which is conjugate to the margin off Newfoundland being investigated by a previous BGR cruise (Hinz et al., 1989). Methods used were multichannel reflection seismics, gravimetry, magnetics, swath echosounding and sediment echography. The test of the ship and its result is discussed in a separate technical report (Roeser et al., 1991). On two lines crossing the Madeira-Torre Rise we have observed seaward dipping reflector sequences. Their position is conjugate to similar features observed off Newfoundland. Magnetic models for one line show a strong magnetization of the whole reflector sequence. Thus, in analogy to the drilled dipping reflector sequence on the Vøring Plateau, it is likely that it mainly consists of lava flows which were extruded subaerially or in shallow water. In contrast to the dipping reflector sequences found earlier, the newly detected sequences are far away from continental crust. Presumably, at the time of their formation the Midatlantic Ridge was subaerial. Geometrical constraints indicate a compressional regime for the eastern part of the Azores-Gibraltar Fracture Zone. Most prominent expression of this is the Gorringe Bank. Our seismic line across it indicates an overthrusting of oceanic crust, however, it does not show any evidence for a Benioff zone. Therefore, only a small amount of oceanic crust can be subducted until now. We have observed compressional features also in the Tagus Abyssal Plain. Our lines north of the Azores-Gibraltar Fracture Zone did not confirm the weak indications for a continuation of the magnetic anomaly M0 across the fracture zone. The present platetectonic models for this area require therefore a modification. For the definition of the ocean-continent transition in the Iberia Abyssal Plain and for the investigation of the nature of the crust near the transition zone 6 ODP drillsites have been proposed. In response to a request by R.B. Whitmarsh from the Institute of Oceanographic Sciences at Wormley, Godalming, we have carried out the required ODP Site Survey.
In the period from October 16, 1978 to December 9, 1978 geophysical investigations have been carried out on SONNE cruises SO-7A and SO-7B on the Lord Howe Rise off eastern Australia and in the northern Coral Sea by the Federal Institute for Geosciences and Natural Resources (Hannover) in co-operation with the Bureau of Mineral Resources, Geology & Geophysics (Canberra), Department of Scientific and Industrial Research (Wellington), Geological Survey of Papua New Guinea (Port Moresby). A total of 10,500 km of bathymetric, magnetic and gravity profiles, 7,000 km of digital seismic reflection profiles and 50 sonobuoy refraction profiles were recorded during this survey. Objective of cruise SO-7A was to determine the depth and nature of the basement of the Lord Howe Rise, the configuration of the early rift basin, and the thickness and internal structure of the enclosed sediments. A new sea-mount in the southern Norfolk Basin rising some 2200 m above sea floor characterized by a free air anomaly of about 80 mgal and by a magnetic anomaly of some 500 nT was found. A complex horst and graben zone often associated with volcanic intrusions underlies the western flank of the Lord Howe Rise. Within some grabens the "breakup"-unconformity seems to exist, supporting the model that the Lord Howe Rise and the Dampier Ridge were once part of the Australian continent. The thickness of pre-breakup sediments is normally small on the Lord Howe Rise. Only in some grabens the thickness of these sediments exceeds 1 second reflection time. The Oligocene/Eocene unconformity and a Miocene unconformity are clearly recognizable in all our seismic records. Best explanation of these unconformities seems to be relative falls in sea level due to swelling and subsidences of oceanic crust. Strong variations in the character of the acoustic basement have been observed. Besides blocks with flat-lying acoustic basement zones with hummocky and irregular basement surface exist which may relate to areas of stretched continental basement contaminated by basaltic intrusions. The eastern edge of the Lord Howe Rise is characterized by an edge anomaly rising to +1000 nT. The general magnetic and gravity features of the western flank of Lord Howe Rise and the Dampier Ridge are: A generally quiet magnetic field with isolated large anomalies, consistent with the faulted acoustic basement of low or moderate susceptibility, with low susceptibility, dense intrusives in places, and also high susceptibility intrusions or flows. Gravimetric/magnetic "edge anomalies" between the outer and western edge of the Lord Howe/Dampier Ridge and the Tasman Sea are apparently absent. The objective of cruise SO-7B was to search for marginal graben zones off the Queensland and Papuan Plateaus associated with the initial rifting of the Coral Sea Basin. In the seismic records at least two regional unconformities are recognizable which represent periods of erosion or non-deposition during Oligocene/Eocene respectively in Miocene time. Further an older unconformity exists in block-faulted regions of the Queensland and Papuan Plateaus. Beneath the present continental slopes the Miocene and Oligocene/Eocene unconformities lie close together and are sometimes coincident. The transition from oceanic crust of the Coral Sea Basin to continental crust of the Queensland and Papuan Plateaus occurs in the surveyed area over a narrow ( 50 km) zone and is associated with a sediment filled graben. The graben-zone observed beneath the present slope of the Queensland and Papuan Plateaus contains more than 2 sec (reflection time) thick sediments of pre-Oligocene/Eocene age. The oceanic crust, as it approaches the plateaus, either rapidly deepens or abruptly stops and/or changes its seismic character so as not to be recognizable. In the seismic records from the outer part and slope of the Queensland and Papuan Plateaus, 5 to 10 km wide, convex, reflectionless zones exist. These features are interpreted as drowned fossil reefs. All observed reefs lie beneath the Oligocene/Eocene unconformity indicating these present deep-water areas were at shallow depths in pre-Eocene time. In the surveyed area post-Oligocene fossil reefs do not exist suggesting these areas were already at upper bathyal depths in the Oligocene. Assuming a seismic velocity for reefal material of 4000 m/s, the reefs on the outer Papuan Plateau have an approximate thickness of 3000 meters. Assuming a reef-growth rate of 25 m/m.y. the growth of the reefs started in upper Jurassic time (120 m.y. + 29 m.y. (assumed age of the Oligocene/Eocene unconformity) yields to 149 m.y.). The basement of the Papuan and Queensland Plateaus is probably crystalline Paleozoic rocks. This is suggested for the Queensland Plateau in particular by their relatively shallow depth, refraction velocities of 6.0 - 6.3 km/s (Ewing et al.) and 5.0 (this survey) and high intensity magnetics. A complex system of horst and graben structures exist on the Queensland and Papuan Plateaus. A larger graben appears to trend in an East-West direction on the southern Papuan Plateau. This graben is about 1 second (reflection time) deep and varies in width from 5 to 20 km.
The previous BGR-cruises with RV AURELIA in 2003 and 2004 and RV HEINCKE in 2005 and RV ALKOR in 2006 were designed to collect a grid of seismic MCS-data which should enable us to get a high-resolution overview over the upper 1-2 s TWT of the sediments of the German North Sea sector. The data format is Society of Exploration Geophysicists SEG Y. The aim of this cruise was a detailed survey in the north westernmost area of the German EEZ (exclusive economic zone), the so-called ‘Entenschnabel’ and additionally a mapping of special glacial structures off Sylt Island. The cruise was subdivided into two Legs. One outreaching additional aim was to extend the results from the previous cruises for the Late Tertiary and Quaternary sedimentary evolution into the ‘Entenschnabel’-area which was virtually unexplored by systematic shallow high-resolution seismics. During Leg 1 the BGR high-resolution multichannel seismic reflection system consisting of a GI-Gun (0.8 l) and a 500 m streamer with 36 channels and a shallow swath bathymetric system, type SIMRAD EM1200 by Kongsberg, Bergen, Norway were used. While the BGR-seismic system was used to observe the shallow subsurface down to 2 s TWT penetration depth, the swath bathymetric system was used to identify possible pockmark locations as well as sampling positions for the deployment of the BGR vibration corer during the succeeding Leg 2. All seismic records were processed onboard for the quality control and for a first interpretation loaded into GEOQUEST.
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