The cruise BGR95 from 19th November to 28th December 1995 with M.S. AKADEMIK NEMCHINOV was designed to acquire new marine geophysical data for a better understanding of the geological processes and structural variations of the Cretaceous-aged oceanic crust of the Angola Basin in the South Atlantic regarding its reflectivity pattern, its shape of the basement surfaces and its crustal thickness. These evaluations were extended onshore to the ‘Damara Igneous Province’. The aim of this study was the investigation of the rift-related volcanic-magmatic processes accompanying the initial stage of the opening of the South Atlantic Ocean. The survey was a co-operation of BGR, Alfred Wegener Institute for Polar and Marine Research (AWI), GeoForschungsZentrum Potsdam, University of Göttingen and Johann Wolfgang Goethe-University Frankfurt/Main. The M.S. AKADEMIK NEMCHINOV generated the seismic signals by a tuned airgun array of 3260 cu.in. (= 53.4 l) together with two AWI owned large volume guns of 2 x 2000 cu.in. (= 65.6 l), recorded the MCS signals with a 3000 m streamer and controlled the shot releases for the ocean bottom hydrophones (OBH’s) and the onshore seismic stations (PEDAS). A total of 5,114 km of multichannel seismic reflection data in parallel with magnetic and gravity measurements have been collected onboard the M.S. AKADEMIK NEMCHINOV. 1069.4 km of the seismic work was done on 3 combined refraction/wide angle offshore and onshore traverses. The offshore part was recorded by 7 ocean bottom hydrophones (OBH) operated by the M.V. POLAR QUEEN (Reichert et al., 1996). The registration onshore Namibia was performed by 25 mobile seismic landstations (PEDAS) on each profile (Schulze et al., 1996). First results are described in the offshore and onshore reports of these investigations (Reichert et al., 1996, and Schulze et al., 1996). The data clearly show distinct series of the seaward dipping reflector sequences (SRDS) and isochronous variations in the accretion of the oceanic crust. The onshore and offshore registrations show deep arrivals from diving and refracted waves in a range up to 200 to 400 km.
The BGR 1991 cruise with M.V. BIN HAI 511 was designed to study the variability of the oceanic crustal structure along flow-line profiles perpendicular to the ridge axis over Early Tertiary through Cretaceous old oceanic crust of the eastern Atlantic Ocean. Seismic data with a coverage of 3,000 % were acquired along four flow-line profiles with a total length of 4,194 km, and in addition 270 km of MCS data were collected during the period from 2nd October to the 3rd November 1991. The most intriguing new observation from the seismic flow-line profiles is the discovery of two huge oceanic crustal structures characterized by an internally divergent to planar pattern of reflectors having ubiquitous seaward dip. These remarkable structures were found within an about 1,300 km long oceanic crust segment of the eastern South Atlantic located between the Bode Verde Fracture zone in the north and the Rio Grande Fracture Zone in the south. These structures resemble the prominent wedges of seaward dipping reflectors on the widespread volcanic rifted continental margins described in the literature. They are interpreted to represent voluminous build-ups of layered extrusive rocks formed during three excessive episodes of volcanism that accompanied the Cretaceous opening of the South Atlantic. These episodes of excessive volcanism/magmatism are: An episode immediate prior to, and during the first stage of seafloor spreading in the South Atlantic, i.e. during about Hauterivian through about early Aptian; an episode of inferred subaerial and/or shallow marine volcanism along the central South Atlantic spreading ridge during the Albian; and an episode of inferred subaerial and/or shallow marine volcanism along the South Atlantic spreading ridge during latest Cenomanian/earliest Turonian through early Campanian.
Das Projekt "Die Bedeutung des Auftriebsgebietes vor Namibia (Gebiet um Walfisch Rücken) als Senke für partikelreaktive Stoffe (230Th, 231Pa, 210 Pb) (M 48/4)" wird vom Umweltbundesamt gefördert und von Universität Heidelberg, Institut für Umweltphysik durchgeführt. Zur Rekonstruktion der Paläoproduktivität des Ozeans werden in der marinen Geologie sehr häufig Spurenstoffe ('Tracer') verwendet, wie z. B. die natürlichen Radionuklide 230Th und 231Pa. Aus ihrer Verteilung in den Sedimenten wird u. a. auf die Veränderlichkeit der Paläoproduktivität in der geologischen Vergangenheit geschlossen. Im Rahmen dieses Forschungsvorhabens soll das Verhalten dieser Isotope im Bereich des Auftriebsgebietes vor Namibia (Angola-Becken, Kap-Becken) untersucht werden. Es soll nachgeprüft werden, ob das Auftriebsgebiet eine Senke für partikelreaktive Stoffe im Südatlantik darstellt und inwieweit die Hydrographie einen Einfluss auf die Verteilung dieser Isotope in der Wassersäule hat. Darüber- hinaus soll festgestellt werden, wie das 230Th/231Pa-Verhältnis in der Wassersäule modifiziert wird und wie es sich im Sediment abbildet. Mit diesen Untersuchungen sollen Grundlagen geschaffen werden, die einen präziseren Einsatz dieser Isotope als Tracer zur Rekonstruktion der Ozeanographie über geologische Zeitskalen ermöglichen.
Das Projekt "Latitudinale Gradienten der Biodiversität in der abyssalen Tiefsee des Ost- und Südostatlantiks: Kapbecken, nördliches Angolabecken und Guineabecken (M63/2)" wird vom Umweltbundesamt gefördert und von Universität Hamburg, Biozentrum Grindel und Zoologisches Museum durchgeführt.