HR: 0830h
AN: T51F-0228    [PDF]
TI: The Conjugate Volcanic Continental Margins Of Argentina And Southern Africa
AU: * Neben, S
EM: s.neben@bgr.de
AF: Federal Institute for Geosciences & Natural Resources (BGR), Stilleweg 2, Hannover, 30655 Germany
AU: Schreckenberger, B
EM: b.schreckenberger@bgr.de
AF: Federal Institute for Geosciences & Natural Resources (BGR), Stilleweg 2, Hannover, 30655 Germany
AU: Franke, D
EM: d.franke@bgr.de
AF: Federal Institute for Geosciences & Natural Resources (BGR), Stilleweg 2, Hannover, 30655 Germany
AB: In April-June 2003 the German Federal Institute for Geosciences and Natural Resources (BGR) undertook a new marine geophysical cruise along the South Atlantic continental margin off South Africa. In total more than 3,000 km of combined multi-channel reflection seismic (MCS), magnetic and gravity and an additional of 1,300 km with only magnetic and gravity were acquired. In combination with the extensive MCS ($>$20,000 km) data set from the Argentine margin we are able to interpret seven conjugate traverses available over almost exact conjugate parts of these volcanic passive margins. A first interpretation of the raw stacked seismic data from the South African side shows that the volcanic features seem to be mirror images to the structures found on the Argentine margin. Continental break-up and initial sea-floor spreading were accompanied by large-scale magmatism and volcanism as manifested in the seismic data by a huge wedge of seaward dipping reflectors (SDRS), and a distinct high-velocity (average value 7.3 km/s) lower crustal body beneath the SDRS. The data from the Argentine margin already suggested that the emplacement of the deeply buried, 60-120km wide SDRS was episodic as documented by at least three superimposed SDRS units. A similar distinct partitioning of the SDRS into three to four individual wedges is present on the South African margin. From the new data a detailed correlation of timing of these individual pulses is intended. Furthermore, it is possible to estimate the amount of extruded material during the phases of emplacement. The seismic data from the Argentine margin document the presence of a narrow, north-east striking half-graben system beneath the upper slope. This buried half-graben system developed during the final stage of rifting in the Early Cretaceous, whereas the east-west trending Colorado-Basin probably formed earlier. In the new data from South Africa only one half graben was identified up to now.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3025 Marine seismics (0935)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 8105 Continental margins and sedimentary basins
DE: 8155 Plate motions--general
SC: Tectonophysics [T]
MN: 2003 Fall Meeting