Interpretation is not possible due to lack of data or because of poor quality of the data.
Definition of lower boundary
Definition of upper boundary
TNO-GDN ([YEAR]). Not interpreted. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from http://www.dinoloket.nl/en/stratigraphic-nomenclature/not-interpreted.