Die Suche nach dem verschollenen Großsteingrab G4 'Onner es' (Onnen, Prov. Groningen)
At the end of the 1960s during a field survey, a scatter of surface finds of granite fragments and Funnel beaker sherds discovered in the hamlet Onnen, situated on the eastern hillside of the Hondsrug, led to the belief that a megalithic grave must have been present.
Such a burial monument had been mentioned in an early 18th century source, but had never been depicted on a historical map; further reference to this monument came only from a historic toponym Steenberg/Steenbergerveen. At the surface, no traces of a megalithic grave can be discerned at present, whether as an elevation or as a soil mark. In the Dutch hunebedden numeration, the scatter provisionally received the number of G4 (G for the province of Groningen).
The German-Dutch archaeology-project Land der Entdeckungen – Land van ontdekkingen (2011-2014) provided the opportunity to verify the location of the presumed hunebed. The non-destructive technique of soil radar was applied to detect anomalies with the expectation that the extraction of the megalithic stones had caused a distortion in the natural soilprofile in the upper 1.5 m. Immediately adjacent to the find scatter discovered in the 1960s, an elongated pit of 6 m x 11 m caught the attention of the research group, who expected it to be the demolished cavity of the megalithic grave. However, a test excavation exposed a natural depression in the cover sand substratum, revealing a heavily podsolised layer that had originally caused the gauge reading. Everywhere else the podsolised surface had been absorbed into a plaggen soil layer. Afterwards, this depression was filled up with coversand and granite gravel, which is presumably anthropogenic as the substratum proved stoneless to a depth of 2 m. The granite fragments might originate from a torn down hunebed of which the burial chamber should have been paved with cobbles and stone fragments. Pollen analysis suggests that the leveling of the depression took place in the late Middle Ages or Early Modern times. In a later stage, the investigation concentrated on the presence of fragments of natural stone in the modern top soil, to focus on the spot where the burial chamber once stood. Soil radar discerned a dense zone of stones, broken stones and stonedust. Within this zone, cores were extracted tod etect granite scatter, silex, and ceramics, yielding a particle concentration of 12 m x 25 m coinciding with the find scatter of the 1960s. In all probability, this concentration is where megalithic grave G4 once stood, on a sandy ridge at about 50 m away from a pingo remnant.