Evolution of a subtropical sandsea: the Great Western Erg, Algeria

In the Great Western Erg, a continuity of direction exists among valleys coated by hamada crust, hydro-aeolian depressions, and dunes. The age of the hamada crust shows that the main part of the Great Western Erg aeolian structure was mostly formed at the end of Tertiary or the beginning of Quaternary. Subsequent modifications of the Great Western Erg are expressed, first by the superposition of active fine-sand dunes on older and bigger dunes which are characterized by coarse sands: and second, by intense aeolian ablation on the Holocene lake deposits in the hydro-aeolian depressions of the northern edge of the Erg. -English summary