Along-strike switch of subduction polarity in the Pyrenees? (PYRTEC)
PYRTEC is designed to study the differences in subduction pattern of the eastern Pyerenees and the Cantabrian system in the west, varying the geometry and, to some degree, relative (“lithospheric”) strength, architecture and thickness.
The experiments for the eastern Pyrenees are very robust in that they invariably produce northerly subductionand southerly directed shortening by in-sequence foreland-directed contraction. The Cantabrian system, which involves collision between “oceanic” and “continental” plates, is less stable, producing both southerly and northerly subduction and frequently also obduction.
Preliminary results suggest that the strength of the “oceanic” plate and the geometry of the plate-plate contact rule these processes and the pattern of subduction/obduction. If this is confirmed, it indicates that plate contacts that are seared before or at an early stage of collision may be prone more easily to produce obduction than orogens that are characterized by head-on collision.
Preliminary field work has confirmed a complex relation between frontal deformation in the thrust system and the post-orogenic subsidence/uplift/erosion patterns. All data (field study and experimental) are systematized to produce constraints to the numerical modelling to come.