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Book Chapter

The role of detachment faulting in the formation of an ocean–continent transition: insights from the Iberia Abyssal Plain

By
G. Manatschal
G. Manatschal
Geologisches Institut, ETH Zürich, CH-8092 ZüCrich, SwitzerlandPresent address: EOST-CGS (UMR 7517) CNRS, UniversitѐLouis Pasteur, 1 rue Blessig, F-67064 Strasbourg Cedex, France(e-mail: manatschal@illite.u-strasbg.fr)
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N. Froitzheim
N. Froitzheim
Geologisches Institut, Universität Bonn, Nussallee 8, D-53115 Bonn, Germany
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M. Rubenach
M. Rubenach
Department of Earth Sciences, James Cook University, Townsville, 4811 Qld., Australia
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B. D. Turrin
B. D. Turrin
Lamon–Doherty Earth Observatory, Route 9W, Palisades, NY 10964, USA
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Published:
January 01, 2001

Abstract

The Iberia Abyssal Plain segment of the West Iberia margin was drilled during Ocean Drilling Program Legs 149 and 173 and has been extensively studied geophysically. We present new microstructural investigations and new age data. These, together with observed distribution of upper-and lower-crustal and mantle rocks along the ocean–continent transition suggest the existence of three detachment faults, one of which was previously unrecognized. This information, together with a simple kinematic inversion of the reinterpreted seismic section Lusigal 12, allows discussion of the kinematic evolution of detachment faulting in terms of the temporal sequence of faulting, offset along individual faults, and thinning of the crust during faulting. Our study shows that the detachment structures recognized in the seismic profile became active only during a final stage of rifting when the crust was already considerably thinned to c.12 km. The total amount of extension accommodated by the detachment faults is of the order of 32.6 km corresponding to a ß factor of about two. During rifting, the mode of deformation changed oceanwards. Initial listric faulting led to asymmetric basins, accommodating low amounts of extension, and was followed by a situation in which the footwall was pulled out from underneath a relatively stable hanging wall accommodating high amounts of extension. Deformation along the latter faults resulted in a conveyor-belt type sediment accumulation in which the exhumed footwall rocks were exposed, eroded and redeposited along the same active fault system.

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Contents

Geological Society, London, Special Publications

Non-Volcanic Rifting of Continental Margins: A Comparison of Evidence from Land and Sea

R. C. L. Wilson
R. C. L. Wilson
The Open University, UK
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R. B. Whitmarsh
R. B. Whitmarsh
Southampton Oceanography Centre, UK
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B. Taylor
B. Taylor
University of Hawaii, Hawaii
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N. Froitzheim
N. Froitzheim
University of Bonn, Germany
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Geological Society of London
Volume
187
ISBN electronic:
9781862394353
Publication date:
January 01, 2001

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