Nuevos datos sobre cavidades en la cresta Sur del Valle de Ata (Madotz -Sierra de Aralar).

The discovery of two new cavities in a limestone bar, of 4 km of lateral extension, which limits the South of Ata Valley (Aralar mountains, Navarra) is described. The compact outcrop of reef limestones (of early Cretaceous age) is limited between marls and calcareous siltstones, forming a sharp ridge relief on which no cavities were known. The surveys conducted enabled the discovery of two chasms, of little development, and various surface karstic landforms. The cavities are described and data on cave fauna are presented. Hydrogeological features of the set are discussed.