Space-time partitioning of the Mesozoic deformation along the Iberia/Eurasia diffuse plate boundary
Résumé
Since the 1970s, the Mesozoic kinematic evolution of the Iberian plate has been largely
debated. In particular, no consensus exists on the timing, kinematics and partitioning
of the deformation along the Iberia/Eurasia plate boundary during the Late Jurassic-
Early Cretaceous. Most of the plate kinematics models suggest that this plate boundary
must have accommodated ~400 km of left-lateral displacement between the two plates
in this time lapse. However, no field evidence exists for a narrow transform plate
boundary that could have accommodated such displacement. In the last decade, several
authors have tried to partition this deformation between two/three transtensional
corridors centered in the Pyrenean realm, but still without resolving the discrepancy
between postulated and observed displacement. In this work, we propose a reappraisal
of the Mesozoic Iberia/Eurasia plate boundary by reviewing the tectonic and kinematic
evolution of the numerous rift basins located between the Iberian Chains System (to the
S) and the Armorican Shelf/Northern Aquitaine System (to the N). This allows to
define the transition between the two plates as a
~400 wide NW-SE trending diffuse plate boundary across which the deformation is
partitioned. Its polyphased evolution consists of four main steps: i) a Late Jurassic
phase of left-lateral transtension localized at the northern and southern boundaries of
the system, while the rest of the rift basins underwent orthogonal rifting; ii) a
Neocomian phase of tectonic quiescence; iii) a Barremian-Aptian phase of diffuse leftlateral
transtensional rifting, while the North Pyrenean Rift System underwent
orthogonal rifting; iv) an Albian- Cenomanian phase of transtension localized along the
Basque-Cantabrian/North Pyrenean corridor, following the onset of oceanic spreading
in the Bay of Biscay margins, while the rest of the rift basins underwent post-rift stage.
Finally, we discuss the role of structural inheritance and pre-rift salt in favoring
distributed rather than localized deformation at the plate boundary. This review allows
to make inferences on the timing of rotation of Iberia during the Mesozoic and to
highlight the contribution to the evolution of the plate boundary of some domains
within the Cenozoic foreland basins of the Pyrenees which have been often disregarded.