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Crustal structure of the transpressional Variscan orogen of SW Iberia: SW Iberia deep seismic reflection profile (IBERSEIS)
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2003 (English)In: Tectonics, ISSN 0278-7407, E-ISSN 1944-9194, Vol. 22, no 6, 1062- p.Article in journal (Refereed) Published
Abstract [en]

IBERSEIS, a 303 km long (20 s) deep seismic reflection profile, was acquired across the Variscan belt in SW Iberian Peninsula. The acquisition parameters were designed to obtain a high-resolution crustal-scale image of this orogen. The seismic profile samples three major tectonic terranes: the South Portuguese Zone, the Ossa-Morena Zone, and the Central Iberian Zone, which were accreted in Late Paleozoic times. These terranes show a distinctive seismic signature, as do the sutures separating them. Late strike-slip movements through crustal wedges are apparent in the seismic image and have strongly modified the geometry of sutures. The upper crust appears to be decoupled from the lower crust all along the seismic line, but some deformation has been accommodated at deeper levels. A sill-like structure is imaged in the middle crust as a 1–2 s thick and 175 km long high-amplitude conspicuous reflective band. It is interpreted as a great intrusion of mafic magma in a midcrustal decollement. Taking into account surface geological data and the revealed crustal architecture, a tectonic evolution is proposed for SW Iberia which includes transpressional collision interacting during Early Carboniferous with a mantle plume. The Moho can be identified along the entire transect as subhorizontal and located at 10 to 11 s, indicating a 30–35 km average crustal thickness. Its seismic signature changes laterally, being very reflective beneath the South Portuguese Zone and the Central Iberian Zone, but discontinuous and diffuse below the Ossa Morena Zone.

Place, publisher, year, edition, pages
AGU , 2003. Vol. 22, no 6, 1062- p.
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-97857DOI: 10.1029/2002TC001479ISI: 000186512900001OAI: oai:DiVA.org:uu-97857DiVA: diva2:172944
Available from: 2008-11-07 Created: 2008-11-07 Last updated: 2010-09-15Bibliographically approved
In thesis
1. Seismic Studies of Paleozoic Orogens in SW Iberia and the Middle Urals
Open this publication in new window or tab >>Seismic Studies of Paleozoic Orogens in SW Iberia and the Middle Urals
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Controlled source seismic methods were employed in this study to investigate the reflectivity and velocity structure of two Hercynian orogens – the Uralides and Variscides. Conventional common depth point (CDP) sections from five reflection seismic campaigns and a velocity model obtained from tomographic inversion of wide-angle observations were the main datasets studied from the Middle Urals. These were complemented with the near-vertical seismic sections and velocity models from the Southern Urals. In the Variscides, conventional CDP processing, along with non-standard processing and synthetic data modeling, were used to obtain and interpret reflection seismic images of the Southwestern Iberian crust.

Although, the Uralian and Variscan belts were formed in Late Paleozoic time in apparently similar plate collisional settings, a comparison of the seismic results show that the crust of these two orogens looks quite different at depth. In the Urals, collision of Baltica with Asian terranes (Siberia and Kazakhstan) resulted in a highly diversely reflective crust of 40-45 km thickness. The axial zone of the orogen is characterized by a high velocity crustal root of diffuse reflectivity and an imbricated Moho, with a crustal thickness reaching 55-60 km. The Moho discontinuity is marked by a sharp decrease in reflectivity and is well imaged in most locations except in the crustal root zone. The Southwestern Iberian Variscan crust is 30-35 km thick and is characterized by a highly reflective two-layered structure that resulted from collision of Luarussia and Gondwana, including terranes in-between them. This type of crustal structure is very similar to those imaged in other regions of the Variscan belt in the Europe. The Moho discontinuity is flat and appears to be the deepest reflection. This thesis compares the deep structure of the two orogens and interprets mountain building processes related to late Paleozoic plate movements.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 79 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 581
Reflection seismics, Traveltime tomography, Uralian orogeny, Variscan orogeny, Crustal structure
National Category
urn:nbn:se:uu:diva-9405 (URN)978-91-554-7358-7 (ISBN)
Public defence
2008-11-28, Axel Hambergsalen, Geocentrum, Villavägen 16, 752 36 Uppsala, 10:00
Available from: 2008-11-07 Created: 2008-11-07 Last updated: 2016-05-13Bibliographically approved

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