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Seismic constraints on the three-dimensional geometry of low-angle intracrustal reflectors in the Southern Iberia Abyssal Plain

By S.M. Dean, T.A. Minshull and R.B. Whitmarsh


Several lines of evidence suggest that simple shear rifting of the continental crust, in the form<br/>of low-angle detachment faulting, occurred during the final stages of continental breakup<br/>between West Iberia and the Grand Banks. The primary evidence for such faulting is the<br/>occurrence of low-angle, high amplitude reflectors within the basement adjacent to the ocean–<br/>continent transition zone. Here we present a series of intersecting, depth migrated seismic<br/>reflection profiles that image one such reflector, the H-reflector, located on the southern edge<br/>of Galicia Bank. ‘H’ lies beneath several boreholes drilled during ODP Legs 149 and 173,<br/>in a region where the oceanward extent of extended continental crust steps at least 150 km<br/>westward from its location in the southern Iberia Abyssal Plain to its location off the relatively<br/>shallow Galicia Bank. In our profiles ‘H’ appears to define a surface that extends over a region<br/>of at least 200 km2 and that dips down ?19? to the north, towards Galicia Bank. The profiles<br/>show that a close affinity exists between ‘H’ and the most seaward continental crust. Based on<br/>geophysical data and ODP drilling results, we infer that the basement above ‘H’ is composed<br/>of continental crust deformed by extensional faults into a series of wedge-shaped blocks and<br/>thin slivers. These basement wedges have a complex 3-D geometry. ‘H’ rises to the basement<br/>surface on a number of the seismic profiles and appears to define locally the oceanward extent<br/>of continental fault blocks

Topics: QE
Year: 2008
OAI identifier:
Provided by: e-Prints Soton

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  3. (2007). Characterizing the Galicia Bank-Southern Iberia Abyssal Plain rifted margin segment boundary using multichannel seismic and ocean bottom seismometer data,
  4. (2008). Compressional structures on the West Iberia rifted margin: what controls their 30 distribution? In: The Nature and Origin of Compression in Passive Margins,
  5. (1987). Crustal geometry and extensional models for the Grand Banks, Eastern Canada: constraints from deep seismic reflection data, in Sedimentary Basins and BasinForming Mechanisms,
  6. (1998). Deep structure in the vicinity of the ocean-continent transition zone under the southern Iberia Abyssal Plain,
  7. (2000). Deep structure of the ocean-continent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: The IAM-9 transect at 40°20’N,
  8. (1999). Deep structure of the ocean–continent transition in the southern Iberia Abyssal Plain from seismic 27 refraction profiles: Ocean Drilling Program (Legs 149 and 173) transect,
  9. (1980). Depth migration after stack,
  10. (1999). Detachment faulting at ocean core complexes,
  11. (1995). Detachment tectonics during Atlantic rifting: analysis and interpretation of the S reflector, the west Galicia margin, in The Tectonics, Sedimentation and Palaeoceanography of the North Atlantic Region,
  12. (1988). Early Cretaceous and Tithonian magnetostratigraphy of the Galicia margin,
  13. (1996). Evidence for detachment tectonics on the Iberia Abyssal Plain rifted margin,
  14. (1988). Evidence from the northern Red Sea on the transition from continental to oceanic rifting,
  15. (2001). Evolution of magma-poor continental margins from rifting to seafloor spreading,
  16. (1992). Evolution of Mesozoic sedimentary basins around the North Central Atlantic: a preliminary plate kinematic solution,
  17. (2004). Exhumed upper mantle within the ocean-continent transition of the northern West Iberia margin: Evidence from prestack depth migration and total tectonic subsidence analyses,
  18. (1997). GEBCO Digital Atlas compiled by
  19. (1992). Imaging and velocity estimation with depth-focusing analysis,
  20. (1996). London Special Publication, London, Geological Society, in
  21. (1981). Low-angle normal faults in the Basin and Range Province: nappe tectonics in an extending orogen,
  22. (2003). Magmatism at the west Iberia non-volcanic rifted continental margin: evidence from analyses of magnetic anomalies,
  23. (2003). Mechanisms of extension at nonvolcanic margins: Evidence from the Galicia interior basin, west of
  24. (1995). Models of the development of the West Iberia rifted continental margin at 40°30’N deduced from surface and deep-tow magnetic anomalies,
  25. (1992). Nature of the S reflector beneath the Galicia Banks rifted margin: preliminary results from prestack depth migration,
  26. (1991). New evidence on the structure of the Labrador Sea/Greenland continental margin,
  27. (2004). New models for evolution of magma-poor rifted margins based on a review of data and concepts from West Iberia and the Alps,
  28. (1993). Ocean-continent boundary in the Iberia Abyssal Plain from multichannel seismic data,
  29. (1998). ODP Leg 173 Shipboard Scientific Party,
  30. (1987). Passive margin formation by low-angle faulting within the upper crust: the Northern Bay of Biscay margin,
  31. (1987). Physiography and structure of the western Iberian continental margin off Galicia, from sea beam and seismic data,
  32. (1988). Rifting of the Galicia margin: crustal thinning and emplacement of mantle rocks on the seafloor,
  33. (1978). Rifting, crustal attenuation and subsidence in the Bay of Biscay,
  34. (1996). Seismic slip on a low angle normal fault in the Gulf of Corinth: evidence from high-resolution cluster analysis of microearthquakes,
  35. (1996). Seismic stratigraphy and tectonic history of the Iberia Abyssal Plain,
  36. (1993). Sensitivity of prestack depth migration to the velocity model,
  37. (1997). Shallow dips of normal faults during rapid extension: earthquakes in the Woodlark-D'Entrecasteaux rift system,
  38. (2000). Tectonic implications of exposure of lower continental crust beneath the Iberia Abyssal Plain, Northeast Atlantic Ocean: Geophysical evidence,
  39. (1994). Tectonics of rift propagation into a continental margin: Western Woodlark Basin,
  40. (1992). The ocean-continent boundary off the western continental margin of Iberia - II. Crustal structure in the Tagus Abyssal Plain,
  41. (1989). The origin of metamorphic core complexes and detachment faults formed during Tertiary continental extension in the northern Colorado River region,
  42. (2007). The tectonosedimentary and morpho-tectonic evolution recorded in the deep IberiaNewfoundland margins: Evidence for a complex break-up history,
  43. (1996). The western Iberia margin: a geophysical and geological overview,

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