Dunes in Abalos Undae (ctx frame - possible True Colors; credits: Lunexit)

The Abalos Undae Dunefield stretches westward, away from a portion (Abalos Colles) of the ice-rich North Polar Layered Deposits that is separated from the main Planum Boreum dome by two large chasms (---> abissi, crepacci).
These dunes are special because their sands may have been derived from erosion of the Rupes Tenuis unit (the lowest stratigraphic unit in Planum Boreum, beneath the icier layers) during formation of the chasms.
Some researchers have argued that these chasms were formed partially by melting of the polar ice.