Figure 2 in The first in situ collection of a mosasaurine from the marine Breien Member of the Hell Creek Formation in south-central North Dakota, USA

Figure 2. Stratigraphic description of the study site, NDGS L301. The original thickness of the Breien Member is not preserved at the site, with the upper prairie surface situated within the upper portion of the Breien Member. Burrows within the Breien Member are largely referable to Ophiomorpha sp., while those in the underlying "Undifferentiated Hell Creek Formation" are small (~3.0–4.0 mm thick) terrestrial burrows and root traces within an organic-rich paleosol.