Corte geológico N-S en el Pirineo oriental: emplazamiento en una secuencia de bloque superior ("fuera de secuencia") de las láminas cabalgantes que forman el manto inferior del Pedraforca

Abstract

We present a N-S geological cross-section in the eastern Pyrenees, starting in the southern margin of the Neogene Cerdanya basin, and ending in the Upper Eocene to Oligocene Ebro foreland basin. The lower Pedraforca thrust sheet, which mainly consists of Mesozoic and Paleocene pre-tectonic sediments, was emplaced during late Lower Lutetian times over the early Lower Lutetian sediments forming the Cadi thrust sheet, and the whole, over the Ebro foreland basin, in a piggy-back thrust-propagation sequence. Once the lower Pedraforca thrust sheet was emplaced, internal deformation processes continued until Upper Eocene to Oligocene times. Subsequently, five thrust slices forming an imbricate system were individualized into this thrust sheet. Field detailed geological mapping allowed us to define four major unconformities in the syntectonic conglomerates. Precise dating of these unconformities constrained the emplacement of the thrust slices. Thus, we conclude that the imbricates formed in an overstep sequence of thrust propagation