Lake sediments covered by a basaltic blanket contain a larger number of well preserved fossils.
Since 1990 studies have been developed towards a multidisciplinary approach to the site. This is equivalent to the Upper Oligocene and a palaeomagnetic age of about 25.8 Ma. New data have corrected this date to about 24.7 Ma, based on determinations of the overlying volcanic material. Geophysical and geological investigations showed that Enspel is part of a complex volcanotectonic structure. The sediments of the Upper Oligocene Enspel lake are rich in organic remains, which are remnants of the primary production in the lake.