6.1. Peat layers: t (tourbe, turf)
Examples: Botrange Bed (tB): oligotrophic bogs mostly on the summits of the Ardennes, Holocene; Pervijze Bed (tP): eutrophic peat in the maritime plain in the reach of the Calais and Dunkerque Members, Holocene, the type layer is mostly Subboreal.
Rotselaar Bed (tR): eutrophic peat layers in the alluvial plains, mostly Early Holocene