It preserves fossils dating back to the latest Cenomanian and Turonian stages of the Cretaceous period.
It consists "predominantly of alternating fossiliferous, organic matter-rich, laminated, dark gray limestone and non-laminated, organic matter-poor limestone in decimeter-thick beds (10 to 30 cm) with occasional centimetric beds (5 cm) of brown shale that show no apparent internal structures.
"[1] The formation is noted for its qualities as a Konservat-Lagerstätte, with notable finds including the plesiosaur Mauriciosaurus, the mosasaur Yaguarasaurus and sharks Ptychodus and Aquilolamna.
It appears to have been deposited on the upper part of a shallow continental shelf.
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