This is how the filling of a ditch for a palisade looks like.
A level of stones and others of clay by the interior and the dark sediment in the outside part of the ditch, where the wood must have been. And practically no archaeological materials inside. It is Coelheira 3, near Santa Vitória, Beja, South Portugal. Excavated by the company Omniknos (for EDIA), it will be published soon in Apontamentos de Arqueologia e Património nº10, 2015.