Argiles d'lignite du Soissonnais
The Argiles d'lignite du Soissonnais is a geologic formation in the Oise department of northern France. The formation has provided fossil mammals, reptiles and fish as well as arthropods in the amber of the formation. The Argiles d'lignite du Soissonnais dates back to the Ypresian stage of the Eocene period. Description. The formation comprises a succession of lenticular bodies showing two main facies; clayey sands rich in frequently pyritised lignite, together with amber and grey clayey sands with less lignite (1 to 12 % of the sediment), with continental vertebrate fauna. These facies, the rarity of mollusk  shells and charophytes, probably due to decarbonatation and the presence of pyrrhotite (FeS), reflect a hypoxic environment. The strata were deposited at the bottom of two channels cutting into underlying Thanetian marine green sands. The channels prograde toward the northeast and were discovered under Oise River Quaternary deposits. Fossil content. The formation has provided among others the following fossils: