Itinerary 6. Elevated Ranges and Interior Basins of the Axial Zone: The Conflent Basin and its Surrounding Massifs

Abstract

Itinerary 6 follows the Têt River valley and opens a window onto the Paleozoic geological structure of the Axial Zone (lithostratigraphy, Hercynian tectonics). Paleogene tectonics, in contrast, has left limited direct evidence of the Alpine orogeny in this part of the Axial Zone, suggesting that the Hercynian basement in the eastern Pyrenees was not intensely deformed by basement nappes and thrusts during Alpine collision. The tectonic record can mostly only be inferred by proxy methods rather than by direct observation, mainly from rock-cooling histories based on low-temperature thermochronology. The main focus is thus on Neogene tectonics and geomorphological evolution. Both aspects are conspicuous in the landscape of the Conflent half-graben, its sediment fill, the faceted spurs along its boundary fault scarp, and the successive generations of pediments cut into the flanks of the surrounding footwall massifs. Another focus is the incision chronology of the Têt valley, which can be estimated by dating successive generations of alluvial deposits trapped in limestone caves on canyon flanks near Villefranche and alluvial terrace deposits that extend deep into the Axial Zone along the Têt River. These have been used as proxies for estimating rates of neotectonic uplift of the mountain range.