sentences:  As a stratigraphic unit, Olympia Undae describes materials that make up the geographic Olympia Undae as well as other sand sheets and dune fields encircling Planum Boreum (e.g., Abalos Undae).The Olympia Undae unit is Amazonian in age.To address some of this confusion, the stratigraphic term Olympia Undae unit has recently been renamed to simply "undae unit," since it encompasses other named dune fields (undae) around Planum Boreum.