Kinematic Evolution of the Western Pyrenees Thrust Front From Paleomagnetic Analysis on its Foreland Basin.
Abstract
The Pyrenees is a collisional orogen formed during the Alpine orogeny. Its southwestern frontal thrust was originated as a result of the Cenozoic inversion of preexisting extensional faults. The emplacement of the frontal thrust in the Western Pyrenees generated a foreland basin, which locally accumulated more than 4,500 meters of Tertiary sediments. The kinematic evolution of the Western Pyrenees thrust front is poorly constrained due to the scarcity of reliable age constraints within the Tertiary sediments. However, the good exposure conditions of syntectonic continental deposits in its foreland basin makes it an excellent scenario to carry out paleomagnetic and structural studies in order to unravel the kinematic history, geometry and evolution of the thrust front. A magnetostratigraphic composite section along the continental basin infill was sampled covering up to 3,000 m of succession. Correlation of the local magnetostratigraphy with the GPTS was helped by a new mammal fossil locality found in continental sediments and attributed to the Agenian local biozone Y (MN2D). The cronostratigraphy of the tectosedimentary units, ranging from lower Oligocene (Cr12r) to lower Miocene, provides further constraints on the timing of two main tectosedimentary events recorded as major unconformities within the basin infill. From this study, sedimentation rates have been also obtained. The analysis of several paleomagnetic sites revealed that no vertical axes rotations occurred in the Tertiary sediments regardless superimposed folding with oblique axes could be observed, and the proximity of adjacent structures as the Estella diapir and the Pamplona fault. Finally, the analysis of the anisotropy of magnetic susceptibility together with collected sedimentary data suggests that magnetic fabrics record both, a depositional and tectonic fabric.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFMGP43C1494A
- Keywords:
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- 1518 Magnetic fabrics and anisotropy;
- 1520 Magnetostratigraphy;
- 1525 Paleomagnetism applied to tectonics: regional;
- global