Rifting Processes on the West Galicia Margin, Spain
Published:January 01, 1989
G. Boillot, D. Mougenot, J. Girardeau, E.L. Winterer, 1989. "Rifting Processes on the West Galicia Margin, Spain", Extensional Tectonics and Stratigraphy of the North Atlantic Margins, A. J. Tankard, H. R. Balkwill
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The west Galicia passive margin exposes extensional structures (north-south normal faults and tilted crustal blocks; northeast-southwest trans-verse faults) formed during a Valanginian-latest Aptian rifting episode. The structural setting was controlled by older Variscan lineaments and by Early Cretaceous plate kinematics. Prior to the Hauterivian, crustal stretching was apparently northeast-directed, and subsequently northwest- directed. The amount of crustal extension is clearly less than the amount of crustal thinning, which is explained better by detachment faulting than by uniform stretching of the lithosphere.
To the north, basaltic basement borders Galicia Bank. To the west, the margin is bounded by a ser- pentinized peridotite ridge. Petrological and struc-tural analysis and 39Ar-40Ar dating demonstrate uplift and exposure of mantle rocks onto the sea floor during rifting. We conclude that stretching of the lithosphere beneath a continental rift system can result in total removal of the continental crust and tectonic unroofing of the upper mantle. A com-posite model is suggested, combining astheno- spheric diapirism and normal simple shear of the thinned lithosphere.
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Extensional Tectonics and Stratigraphy of the North Atlantic Margins
Stimulated by the wealth of frontier exploration data and deep seismic surveys about the North Atlantic margins, this publication was crafted to provide a comprehensive analysis of North Atlantic extension. The 40 papers in this volume are divided into 6 sections: concepts, North Atlantic perspectives, North American margins, European-African margins, North Sea and Barents Shelf, and analogs. This book is concerned primarily with the circum-North Atlantic data base. It is largely biased toward presentation and interpretation of data rather than being model driven. The book includes comparative stratigraphic columns for basins of the North Atlantic margins.