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Abstract

AAPG Bulletin, V. 90, No. 1 (January 2006), P. 31-60.

Copyright copy2006. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/08110504138

Mesozoic–Cenozoic evolution of North Atlantic continental-slope basins: The Peniche basin, western Iberian margin

Tiago M. Alves,1 Carlos Moita,2 Frode Sandnes,3 Tiago Cunha,4 Joseacute H. Monteiro,5 Luis M. Pinheiro6

1Departamento de Geologia Marinha, Instituto Nacional de Engenharia, Tecnologia e Inovaccedilatildeo, Estrada da Portela, Zambujal-Alfragide, 2720-866 Amadora, Portugal; [email protected]
2Direcccedilatildeo Geral de Geologia e Energia-Divisatildeo para a Pesquisa e Prospecccedilatildeo de Petroacuteleo, Av. Repuacuteblica 45-5deg, Lisbon, Portugal; [email protected]
3TGS-NOPEC Geophysical Company, Baarsrudveien 2, N-3478 Naersnes, Norway; [email protected]
4Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, United Kingdom; [email protected]
5Departamento de Geologia Marinha, Instituto Nacional de Engenharia, Tecnologia e Inovaccedilatildeo, Estrada da Portela, Zambujal-Alfragide, 2720-866 Amadora, Portugal; [email protected]
6Departamento de Geociecircncias, Universidade de Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal; [email protected]

ABSTRACT

New regional (two-dimensional) seismic reflection data, published Deep-Sea Drilling Project–Ocean Drilling Program reports, and unpublished shallow-offshore well information characterize the Mesozoic–Cenozoic evolution of the western Iberian continental slope north of 38deg45primeN. Two distinct sectors bounded by first-order transfer faults exist between the Galicia Bank and the Nazareacute fault. The northernmost sector 1 is filled by Triassic–Aptian (prebreakup) sequences, reaching more than 3.5 s two-way traveltime (TWTT) in thickness in distinct half grabens. Salt pillows, salt ridges, minibasins, and salt-detached overburden faults were generated during the Mesozoic and reactivated in the Cenozoic. Sector 2 shows Triassic–Jurassic units more than 2.0 s TWTT thick, underlying east-tilting half grabens of Early Cretaceous age. Salt structures in this sector evolved into mature salt diapirs. Postbreakup units are up to 2.0 s TWTT thick in both sectors. The evolution of the study area replicates evolutionary settings that have previously been proposed for nonvolcanic passive margins. However, some distinct features are noted: (1) widespread Triassic–Berriasian units deposited over rotated tilt blocks represent the early rifting stage; (2) Early Cretaceous subbasins showing rift-climax units, most likely formed during the advanced rifting stage, are spatially constrained to an approximately 100-km (62-mi)-wide region stretched along the continental slope; and (3) listric blocks and their associated low-angle (deep) detachment faults, formed on the distal margin during the advanced rifting and transition to sea-floor spreading stages, show no developed rift-climax units above them. From the early rifting stage onward, Mesozoic faults and halokinetic structures induced local differences in the thickness and character of seismic facies. Cenozoic (Alpine) tectonism promoted the reactivation of older Mesozoic structures.

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