Early diagenesis of the Upper Devonian Escuminac Formation in the Gaspé Peninsula, Québec: sedimentological and geochemical evidence

Clay mineral investigations, pyrolysis of organic matter, and microscopic observation of palynomorphs are used to interpret the diagenetic conditions of the Upper Devonian Escuminac Formation, Quebec, Canada. Pyrolysis of kerogen, vitrinite reflectance, and the presence of smectite show that the sediments of this formation have been subjected only to a shallow burial diagenesis; hence, the geochemical signatures are informative on the palaeoenvironment. Concretions are observed in the Escuminac Formation. Sedimentological and geochemical evidence suggest that these concretions were formed during early diagenesis from biodegradation of organic matter. The well-known fish-fauna of the Escuminac Formation show good preservation, due in part to extensive early diagenetic carbonate cementation. The occurrence of calcite cements and fibrous calcite is attributed to the early diagenetic transformation of pre-existing organic matter.