Yardangs in the semiarid central sector of the Ebro Depression (NE Spain)

Abstract

This work reveals the existence of yardangs in the central sector of the semiarid Ebro Depression of Spain. Almost all the documented yardang fields are located in extreme arid environments. The yardangs are developed in horizontal tertiary gypsum and limestone. More than 100 closed depressions (solution dolines) have been formed in the soluble sediments of this area, some of them hosting saline lakes or playas. All the yardangs occur on the leeward margin of the larger playas and their mean orientation (N122E) coincides with the prevalent direction of the strong local wind called Cierzo. Two main types of yardang have been identified; 44 rock yardangs formed in the Miocene bedrock and six yardangs developed in unconsolidated lacustrine deposits. Nebkha dunes have been recognized and yardang-like morphologies in building rubble accumulations on the floor of a playa (<100 years old). The generation of yardangs in this semiarid area is related to the presence of playas, which constitute the source of abrading particles during dry periods. At the present time, the yardangs developed in the lacustrine terraces, nebkhas and rubble accumulations are active landforms, whereas the rock yardangs are considered to be inactive.