| Klerf Formation | |
| Period: | Emsian |
| Age: | Emsian ~ |
| Type: | Geological formation |
| Prilithology: | Siltstone, shale |
| Otherlithology: | Sandstone |
| Subunits: | Reifferscheid Mb. Altenberg Mb. Unterpreth Mb. |
| Underlies: | Heisdorf Formation |
| Overlies: | Schleiden Formation |
| Thickness: | 1300m (4,300feet) |
| Map: | AVALONIA.svg |
| Location: | Eifel |
| Region: | Rhineland-Palatinate |
| Namedby: | Richter |
| Year Ts: | 1919 |
| Location Ts: | Willwerath near Prüm |
| Region Ts: | Eifel |
The Klerf Formation is an Early Devonian (Emsian) formation that includes a Lagerstätte in the Northern Eifel hills, at Willwerath near Prüm, Rhineland-Palatinate, Germany. In it Jaekelopterus rhenaniae, a giant eurypterid was discovered. The Klerf Formation, comprising greenish and reddish shales, siltstones and sandstones, was first described in 1919 by Rudolf Richter (1881-1957) and reaches a maximum thickness of about 1300m (4,300feet).[1] It is part of Alken quarry along with Nellenköpfchen Formation.[2]
The siltstone and sandstone formation was deposited in an estuarine to deltaic environment.[3] This was located on the edge of Avalonia bordering the Proto-Tethys Ocean.
Apart from the largest arthropod, Jaekelopterus rhenaniae, found in the formation, it also preserved other eurypterids (Adelophthalmus sievertsi, Parahughmilleria hefteri, Rhenopterus diensti, Pruemopterus salgadoi, Erieopterus sp.),[4] possible xiphosuran (Willwerathia),[5] terrestrial arachnids (Devonotarbus hombachensis, Xenarachne willwerathensis),[6] [7] some fish, bryozoa, brachiopod and ostracod remains, Mutationella indet. and flora.[8]