Pedraforca: estratigrafía y estructura (Pirineo catalán, España)

Abstract

Pedraforca: stratigraphy and structure (Catalonian Pyrenees, Spain)
Stratigraphic analysis and detailed geological cartography allow us to reach essential conclusions about the sedimentary and tectonic evolution of the Pedraforca peak, an impressive southern Pyrenean mountain.
Simplistic interpretations that consider the Pedraforca peak like a “klippe” of remote origin are based on insufficient or erroneous observations as is demonstrated in this paper.
Understanding the paleogeography of the Lower Cretaceous is basic as it played a decisive role in the posterior structure of the Pedraforca peak.
The pre-Cenomanian tectonics and erosion, distinguished for the first time on this mountain, help to explain the existence of compartments with and without Lower Cretaceous.
The Laramian tectonic phase (uppermost Cretaceous – Paleocene) which involves the paleogeographic wedge towards the S and the E of the Lower Cretaceous produced the migration of the Upper Cretaceous basin during post-Santonian times; this originated two important unconformities over the Pedraforca peak compartment.
The location of the Pedraforca zone (unit s.l.) to the S of Cadí (relative autochthon) from its primitive western position is the result of the major phases of the Pyrenean tectonics (Middle – Upper Eocene and Oligocene in age). Consecutively, the Saldes – L’Espà – Pedraforca subunit, following a fault with a strike-slip component from W to E and thrusting from S to N or from SW to NE, produced the stretching of the SW limb of the hypothetical syncline of the Gresolet
– Gisclareny subunit. This limb, already wedged by the Uppermost Cretaceous Paleocene unconformities, is at present inverted under the northern thrust of the Pedraforca peak subunit.
The Miocene alluvial sedimentation (Roca Roja N) and the affected Neogene tectonics are analysed comparatively to the neighbouring Cerdanya depression.
Recent colluvial deposits (perhaps Plio-Quaternary in age) suggest that the Pedraforca peak is a young relief.