56 research outputs found
Seismic constraints on the three-dimensional geometry of low-angle intracrustal reflectors in the Southern Iberia Abyssal Plain
Several lines of evidence suggest that simple shear rifting of the continental crust, in the formof low-angle detachment faulting, occurred during the final stages of continental breakupbetween West Iberia and the Grand Banks. The primary evidence for such faulting is theoccurrence of low-angle, high amplitude reflectors within the basement adjacent to the ocean–continent transition zone. Here we present a series of intersecting, depth migrated seismicreflection profiles that image one such reflector, the H-reflector, located on the southern edgeof Galicia Bank. ‘H’ lies beneath several boreholes drilled during ODP Legs 149 and 173,in a region where the oceanward extent of extended continental crust steps at least 150 kmwestward from its location in the southern Iberia Abyssal Plain to its location off the relativelyshallow Galicia Bank. In our profiles ‘H’ appears to define a surface that extends over a regionof at least 200 km2 and that dips down ?19? to the north, towards Galicia Bank. The profilesshow that a close affinity exists between ‘H’ and the most seaward continental crust. Based ongeophysical data and ODP drilling results, we infer that the basement above ‘H’ is composedof continental crust deformed by extensional faults into a series of wedge-shaped blocks andthin slivers. These basement wedges have a complex 3-D geometry. ‘H’ rises to the basementsurface on a number of the seismic profiles and appears to define locally the oceanward extentof continental fault blocks
RRS Shackleton Cruises 3/75 and 4/75, 27 March (086) - 7 May (127) 1975. Geophysical studies of the Gulf of Aden, Gulf of Oman and Owen Basin (North West Indian Ocean)
A technique for conducting seismic refraction experiments on the ocean bed using bottom shots: field procedures
RRS Discovery Cruise 107, 28 December 1979 (362) - 9 February 1980 (040). Lesser Antilles Deep Lithosphere Experiment (LADLE)
RRS Discovery Cruise 87, 8 October (281) - 19 October (292) 1977. Instrument testing west of Portugal
RRS Discovery Cruise 161, 15 August (227) - 19 September (262) 1986. Portuguese ocean-continent boundary, plate boundaries west of Iberia and seismic structure of sediments off Madeira
MV Eastella, 19 Jul(200) - 8 Aug(220) 1989. Bottom shot experiments with ocean bottom seismographs in the Norwegian Sea
RRS Discovery Cruise 107, 28 December 1979 (362) - 9 February 1980 (040). Lesser Antilles Deep Lithosphere Experiment (LADLE)
RRS "Discovery" Cruise 93, 26 May (146) - 5 July (186) 1978. The deep structure of the northern Azores-Biscay Rise and detailed seismic studies of crustal ageing east of the Mid-Atlantic Ridge
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