Evidence for detachment tectonics on the Iberia abyssal plain rifted margin

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doi: 10.2973/odp.proc.sr.149.244.1996
Author(s): Krawczyk, Charlotte M.; Reston, T. J.; Beslier, Marie-Odile; Boillot, G.
Author Affiliation(s): Primary:
Kiel University, Geomar Research Centre for Marine Geoscience, Kiel, Federal Republic of Germany
Rice University, United States
Ocean Drilling Program, United States
Université Pierre et Marie Curie, France
Dalhousie University, Canada
Universidad de Granada, Spain
Université de Nantes, France
Florida State University, United States
Universidade de Aveiro, Portugal
INTERGEOS, Netherlands
University of Waterloo, Canada
Lamont-Doherty Earth Observatory, United States
University of Tokyo, Japan
GEOMAR, Federal Republic of Germany
University of Leicester, United Kingdom
University of Texas at El Paso, United States
University of Michigan, United States
Universität Kiel, Federal Republic of Germany
Cornell University, United States
California State University, United States
Iowa State University, United States
University of Maryland System, United States
Open University, United Kingdom
University of California, United States
Laboratoire de Géodynamique Sous-Marine, France
Volume Title: Proceedings of the Ocean Drilling Program; scientific results, Iberia abyssal plain; covering Leg 149 of the cruises of the Drilling Vessel JOIDES Resolution; Balboa Harbor, Panama, to Lisbon, Portugal; sites 897-901, 10 March-25 May 1993
Volume Author(s): Whitmarsh, Robert B.; Sawyer, Dale S.; Klaus, Adam; Beslier, Marie-Odile; Collins, Eric S.; Comas, María Carmen; Cornen, Guy; de Kaenel, Eric; Pinheiro, Luis de Menezes; Gervais, Elisabeth; Gibson, Ian L.; Harry, Dennis L.; Hobart, Michael A.; Kanamatsu, Toshiya; Krawcyzk, Charlotte M.; Liu, Li; Lofts, Jeremy C.; Marsaglia, Kathleen M.; Meyers, Philip A.; Milkert, Doris; Milliken, Kitty L.; Morgan, Julia K.; Ramirez, Pedro; Seifert, Karl E.; Shaw, Timothy J.; Wilson, Chris; Yin, Chuan; Zhao, Xixi
Source: Proceedings of the Ocean Drilling Program; scientific results, Iberia abyssal plain; covering Leg 149 of the cruises of the Drilling Vessel JOIDES Resolution; Balboa Harbor, Panama, to Lisbon, Portugal; sites 897-901, 10 March-25 May 1993, Robert B. Whitmarsh, Dale S. Sawyer, Adam Klaus, Marie-Odile Beslier, Eric S. Collins, María Carmen Comas, Guy Cornen, Eric de Kaenel, Luis de Menezes Pinheiro, Elisabeth Gervais, Ian L. Gibson, Dennis L. Harry, Michael A. Hobart, Toshiya Kanamatsu, Charlotte M. Krawcyzk, Li Liu, Jeremy C. Lofts, Kathleen M. Marsaglia, Philip A. Meyers, Doris Milkert, Kitty L. Milliken, Julia K. Morgan, Pedro Ramirez, Karl E. Seifert, Timothy J. Shaw, Chris Wilson, Chuan Yin and Xixi Zhao. Proceedings of the Ocean Drilling Program, Scientific Results, Vol.149, p.603-615. Publisher: Texas A&M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 0884-5891
Note: In English. 35 refs.; illus., incl. geol. sketch map, sects.
Summary: The Iberia Abyssal Plain segment of the western Iberian Atlantic margin is characterized by highly extended and thinned continental crust bounded westward by a ridge of serpentinized peridotite within the transition zone between continental and oceanic crust. To better understand the evolution of this margin, we have analyzed the margin-normal profile Lusigal 12 (LG12) between Sites 898 and 901. After optimum processing, including prestack depth migration, the seismic sections image strong reflections below the breakup unconformity in this segment of the Iberian nonvolcanic margin. We show that these intracrustal reflections are overlain by probable basement rocks (Vp>5 km/s), whereas synrift or prerift sedimentary units exhibit generally lower velocities (Vp<4.7 km/s). Between Site 901 (identified by drilling as probable continental crust) and Site 900 (amphibolite facies metamorphosed gabbro) to the west, basement is broken up into landward-tilted crustal blocks bound by normal faults. These block-bounding faults appear to detach onto bright intracrustal reflections, which thus mark the lower boundary of the tilted blocks. By analogy with the similar seismic image of the Galicia Bank area to the north, where continental breakup has been controlled by a detachment fault structure (the S reflector), we suggest that continental breakup in the Iberia Abyssal Plain could have been also controlled by detachment faults that were active at different times during rifting. Extension of the upper lithosphere along the detachment system may have exposed a cross-section through the entire lithosphere from the upper crust (in the east, at Site 901), through the lower crust (Site 900), to the uppermost mantle exposed at the western edge of the drilling transect (Site 897, just landward of oceanic crust).
Year of Publication: 1996
Research Program: ODP Ocean Drilling Program
Key Words: 16 Structural Geology; 20 Geophysics, Applied; Atlantic Ocean; Continental crust; Continental margin; Crust; Crustal thinning; Detachment faults; Europe; Extension tectonics; Faults; Galicia Bank; Geophysical methods; Geophysical profiles; Geophysical surveys; Iberian Peninsula; Iberian abyssal plain; Igneous rocks; Leg 149; Metasomatism; North Atlantic; Northeast Atlantic; ODP Site 898; ODP Site 901; Ocean Drilling Program; Oceanic crust; Peridotites; Plate tectonics; Plutonic rocks; Reflection methods; Rifting; Seismic migration; Seismic profiles; Serpentinization; Southern Europe; Surveys; Tectonics; Ultramafics
Coordinates: N404029 N404029 W0110335 W0110335
N404106 N404106 W0120725 W0120725
Record ID: 2007088119
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