bottomset beds

(geology) Horizontal or gently inclined layers of finer material carried out and deposited on the bottom of a lake or sea in front of a delta.

Fine debris deposits, carried furthest out to sea by a river, and forming the lowest layers of its delta. These will be covered by the slightly coarser foreset beds; the upper layers, nearest the coast, will be covered by the coarse, horizontal topset beds.

Bottom set beds