Crinoid plates have been found in the Mesozoic sediments of the highly metamorphic (eclogite facies) Adula nappe. They occur in a dolomitic breccia formation that had previously been confused with the Triassic. We name it the Plattenberg Breccia and we suggest a Middle Jurassic age.
This breccia overlies a Triassic dolomitic formation similar to the Triassic of several other Lower
Penninic units. The absence of affinity with the Triassic of the Briançonnais domain is important with
respect to the recent discovery of a Briançonnais Triassic element below the front of the Adula nappe. Consequently this element must have an ultra-Adula origin and was transported over the Adula during its subduction.