IBERSEIS Normal Incidence (IBERSEIS-NI) is a NE-SW oriented deep seismic reflection profile that provided for the first time a complete section at crustal scale of the Variscan Iberian Massif in the SW of Spain. This seismic profile samples three major tectonic terranes: the South Portuguese Zone, the Ossa-Morena Zone, and the Central Iberian Zone. 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 mid-crustal 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.

IBERSEIS is a 303 km long deep seismic reflection profile. The transect was recorded in 56 days (from May to July 2001) using a 400 channel SERCEL 388 and five 22 Ton Vibroseis trucks. The asymmetric split spread configuration changed along the profile according to the dips of outcropping structures. To achieve a high resolution at shallow levels and to image steep dips, a 35 m station spacing and a 70 m Vibration Point interval was used with a high fold (60 in average). A relatively long sweep (20 s) was chosen to increase the source energy rather than increasing the number of sweeps per Vibration Point. The migrated and stack dataset derived from this raw data are available in http://hdl.handle.net/10261/220989

Comisión Interministerial de Ciencia y Tecnología-Fondo Europeo de Desarrollo Regional (CICYT-FEDER), 1FD1997-2179/RYEN1.-- Junta de Andalucía.-- ENRESA.-- Swedish Research Council.-- Instituto Geológico y Minero de España.-- Spanish Ministry of Science and Technology, BTE2000-0583-C02-01, BTE2000-3035-E, BTE2000-1490-C02-01

IBERSEIS NI: Migrated and stack files: http://dx.doi.org/10.20350/digitalCSIC/12643 ; http://hdl.handle.net/10261/220989

Peer reviewed