Mecanismos de erosión en arcillas miocenas de la Formación Tudela (Bardenas Reales, Navarra, España)

In Bardenas Reales area (located in the central-western part of the Ebro Depression) several erosion rates have been measured along the last years. The mean annual erosion rates are of 32 Tm/Ha/yr. Due to semiarid conditions, precipitation is irregularly distributed along the year with maximums on spring and autumn when the great erosion is produced. There are intensity and quantity thresholds below which erosion does not take place. In Bardenas Reales some erosion processes act (mudslides and armoured mud balls among others). Mudslides are mobilised on spring when the sediment have reached its plastic limit and could slide due to heavy rains. Armored mud balls are produced by the enhancement of popcorn cracks that individualize clays cores which are rounded by water. The same kind of strong precipitation that mobilised mudslides is the responsible of armoured mud ball’s destruction because the conditions to its maintenance are very limited.