The non-cylindrical crustal architecture of the Pyrenees

Sébastien Chevrot,Roland Martin,Mario Ruiz,Sylvain Calassou,Jordi Diaz,Frank Grimaud,Hélène Pauchet,Emmanuel Masini,Frédéric Mouthereau,Matthieu Sylvander,Gianreto Manatschal

doi:10.1038/s41598-018-27889-x

Abstract

We exploit the data from five seismic transects deployed across the Pyrenees to characterize the deep architecture of this collisional orogen. We map the main seismic interfaces beneath each transect by depth migration of P-to-S converted phases. The migrated sections, combined with the results of recent tomographic studies and with maps of Bouguer and isostatic anomalies, provide a coherent crustal-scale picture of the belt. In the Western Pyrenees, beneath the North Pyrenean Zone, a continuous band of high density/velocity material is found at a very shallow level (~10 km) beneath the Mauleon basin and near Saint-Gaudens. In the Western Pyrenees, we also find evidence for northward continental subduction of Iberian crust, down to 50–70 km depth. In the Eastern Pyrenees, these main structural features are not observed. The boundary between these two domains is near longitude 1.3 °E, where geological field studies document a major change in the structure of the Cretaceous rift system, and possibly a shift of its polarity, suggesting that the deep orogenic architecture of the Pyrenees is largely controlled by structural inheritance.

Highlights

The Pyrenees are a collisional orogen produced by the convergence between the Iberian and Eurasian plates from late Cretaceous (~85 Ma) to early Miocene (~20 Ma)
A recent tomographic study relying on teleseismic P waves recorded by the Western PYROPE transect showed that the Mauleon Basin anomaly is produced by a mantle body whose top lies at about 10 km depth[6]
The quality of the receiver function (RF) sections stimulated the deployment of three new transects, in order to characterize the lateral variations of crustal structures, in particular in the Eastern Pyrenees, which remained until today poorly constrained

Summary

Introduction

The Pyrenees are a collisional orogen produced by the convergence between the Iberian and Eurasian plates from late Cretaceous (~85 Ma) to early Miocene (~20 Ma). While no deep reflectors could be clearly identified interpretations favored the northward subduction of the Iberian plate[15,16] This was recently confirmed by migration of receiver functions from two dense transects (transects A-A’ and C-C’ in Fig. 1) deployed during the PYROPE project[17] and by full waveform inversion tomography[6]. We exploit the data from six transects, which were deployed during the PYROPE and OROGEN experiments (Fig. 1) to map the main seismic discontinuities by depth migration of P-to-S conversions These six transects provide a unique dataset to investigate the lateral variations of the deep architecture of a mountain belt. The motivation for this final transect was to sample the Eastern Pyrenean domain, presumably not affected by the opening of the Western Mediterranean basin

Results

Discussion

Conclusion