Sur l'origine karstique et l'âge plio-quaternaire des accumulations bréchiques dites «brèches marines et paléocè nes» d'Amélie-les-Bains (Pyrénées-Orientales, France)

Abstract

The Amélie-les-Bains (Eastern Pyrenees) breccias, recently considered to be Paleocene deep marine deposits, are reinterpreted here as Plio-Quaternary karstic brecciated accumulations. The palaeontological, sedimentological and paleogeographical data proposed in favor of Paleocene age and marine conditions are unfounded. The sediments are found to be devoid of planctonik Foraminifera, a fact that casts doubts on the reliability of the forms supposedly recognized on thin sections of the breccia clasts and cement. The so-called "hemipelagites" and "megablocks" (olistostroma) related to a supposed tectogenic sedimentation in palaeocanyon environments, actually correspond to thin or coarse bedded karstic infillings. The location of the breccias is not in favor of the creation of a trough at the emplacement of the present Tech valley; this would be incompatible with the indisputable post-Paleocene uplift tectonics in the Eastern Pyrenees. The brecciated deposits are closely linked to the carbonate substratum and absent above the surrounding silico-aluminous metasedimentary formations. They stretch along the present topographic surface of the valley flanks and rest upon the Pyrenean (Eocene) thrusts of the Amelie duplex. This new interpretation, which follows previous observations, leads to reject the recent hypothesis involving the development of a "transpyrenean Paleocene trough" filled up with deep marine breccias, following a main "LateCretaceous folding phase" of the Pyrenean orogeny.