Geophysical constraints on the deep structure along the Ecors Pyrenees Line

Daignières, M.; Cabissole, B. de; Muset, Josep Gallart; Hirn, A.; Suriñach, Emma; Torné, Montserrat

doi:10.1029/tc008i005p01051

Cited by 38 publications

(13 citation statements)

References 9 publications

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“…However, they did not invoke a mineralogical transformation, and allocated a constant density (2.93 g cm −3 ) to the lower crust down to 80 km. They included a wide mantle wedge above the subducting lower crust, a feature which is made possible, but not required, by the seismic observations (Daignières et al . 1989).…”

Section: Discussionmentioning

confidence: 99%

A three-dimensional model of the Pyrenean deep structure based on gravity modelling, seismic images and petrological constraints

Vacher¹,

Souriau²

2001

Geophysical Journal International

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Summary The present study aims at building a 3‐D density model of a whole collisional mountain belt at the lithospheric scale. The geometry of internal structures is constrained by seismic studies, while density values are imposed by petrological considerations. The model must fit both the Bouguer and geoid anomalies. This approach is applied to the Pyrenees, for which numerous geophysical data are available. The crustal structure is constrained from the results of seismic profiles. The most important crustal feature is the large Moho jump which coincides with the surface expression of the North Pyrenean Fault, considered as the suture between the Iberian and Eurasian plates. The Eurasian crust is about 30 km thick, whereas the Iberian crust is 50 km thick in the central part of the range. Thick sedimentary basins at the Piedmont, and two large heavy intracrustal bodies located in the western and central parts of the range, are also important features of the crustal model. At the lithospheric scale, a low‐velocity strip under the North Pyrenean Fault down to 80–100 km depth, interpreted as the subduction of the Iberian lower crust, has been revealed by tomographic models. The density of this structure has been constrained using petrological arguments, which assume that the crustal material is transformed into eclogite at about 12–15 kbar (40–50 km depth). An eclogite‐type density value, much higher than the mantle density, is thus imposed from 50 to 100 km depth. Theoretical Bouguer and geoid anomalies are computed for this 3‐D density model using a summation of density block anomalies. A good agreement is found with observations, giving strong support to the proposed model. The crustal structure, as seen by seismic profiles, explains most of the observed long‐wavelength negative Bouguer anomaly, as well the local anomalies related to the intracrustal bodies. A possible mantle origin of these bodies is ruled out. On the other hand, the transformation of the subducted lower crust into dense eclogite provides a successful fit to the long‐wavelength positive geoid anomalies. In addition, the water released during eclogite formation may help to explain the high conductivity zone detected down to 80 km south of the North Pyrenean Fault. The 3‐D model proposed here thus reconciles petrological considerations and geophysical data.

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Section: Discussionmentioning

confidence: 99%

A three-dimensional model of the Pyrenean deep structure based on gravity modelling, seismic images and petrological constraints

Vacher¹,

Souriau²

2001

Geophysical Journal International

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“…The AZ negative anomaly, which decreases in intensity toward the western and eastern edges of the Pyrenean range, is attributed to the thickened low density crustal root of the orogen (Daignières et al, , ; ECORS Pyrenees Team, ; Torné et al, ). In the central sector the NPF delimits the northern edge of this negative anomaly confirming this fault as a major crustal boundary.…”

Section: Bouguer Gravity Anomaliesmentioning

confidence: 99%

Lateral Variations in Foreland Flexure of a Rifted Continental Margin: The Aquitaine Basin (SW France)

Angrand¹,

Ford²,

Watts

2018

Tectonics

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Rift inheritance can play a key role in foreland basin geometry and behavior. If the foreland basin initiates soon after rifting, thermal cooling can also contribute significantly to subsidence. We investigate the effects of crustal inheritance (Aptian‐Cenomanian rifting) on the evolution of the Campanian to middle Miocene flexural Aquitaine foreland basin, northern Pyrenees, France. Surface and subsurface data define rifted crustal geometry and postrift thermal subsidence. Analysis of Bouguer gravity anomalies coupled with flexural modeling constrains the lateral variations of elastic thickness, plate flexure, and controlling loads. The Aquitaine foreland is divided along‐strike into three sectors. The relative role of surface and subsurface (i.e., buried) loading varies along‐strike, and the elastic thickness values decrease from the northeast (25 km) to the southwest (7 km) where the plate is the most stretched. The eastern foreland crust was not rifted and underwent a simple flexural subsidence in response to orogenesis. The central sector was affected by crustal stretching. Here the basin is modeled by combining topographic and buried loads, with postrift thermal subsidence. In the western sector, the foreland basin was created mainly by postrift thermal subsidence. The eastern and central sectors are separated by the Eastern Crustal Lineament, which is one of a series of inherited transverse faults that segment the orogen.

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“…Below the Axial zone the Moho attains a depth of more than 45 km. Wide-angle seismic data give a greater value (Daignikres et al 1989;Suriiiach et al 1993) and gravity data suggest as much as 65km (Torn6 et al 1989). By contrast, the average European crust is thinner, having a thickness of 30km.…”

Section: Introductionmentioning

confidence: 97%

Electrical resistivity model of the crust and upper mantle from a magnetotelluric survey through the central Pyrenees

Pous

Ledo

Marcuello

et al. 1995

Geophysical Journal International

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SUMMARY An MT profile which roughly coincides with the south side of the ECORS‐Pyrenees deep reflection seismic profile was made from the North Pyrenean zone through the central Pyrenees and Ebro basin. The periods recorded ranged from 0.0128s to 2000s. Analysis of MT data shows a 2‐D conductive structure. The strike direction of the structure is E‐W, parallel to the Pyrenean chain. Interpretation of the data includes geomagnetic transfer functions and is constrained by some relevant geometric crustal features observed in seismic data. Accordingly, a 2‐D resistivity cross‐section has been obtained. The most striking results are: (1) detection of subvertical conductors in the upper crust coinciding with major fault zones; (2) detection of a deep, high‐conductivity zone at the contact between the Iberian and the European plates, (3) the fact that the European plate is thicker and more resistive than the Iberian one. Interpretation of the deep high conductivities suggests the existence of partial melting in the Pyrenees related to the subduction of the Iberian plate beneath Europe.

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Geophysical constraints on the deep structure along the Ecors Pyrenees Line

Cited by 38 publications

References 9 publications

A three-dimensional model of the Pyrenean deep structure based on gravity modelling, seismic images and petrological constraints

A three-dimensional model of the Pyrenean deep structure based on gravity modelling, seismic images and petrological constraints

Lateral Variations in Foreland Flexure of a Rifted Continental Margin: The Aquitaine Basin (SW France)

Electrical resistivity model of the crust and upper mantle from a magnetotelluric survey through the central Pyrenees

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