Oxygen and stable carbon isotopes from a nautiloid from the middle Pennsylvanian (Late Carboniferous) impregnation Lagerstätte 'Buckhorn Asphalt Quarry' - Primary paleo-environmental signals versus diagenesis

► We studied stable O and C isotopes and diagenesis of two Pennsylvanian cephalopods. ► Paleo-temperatures and diagenetic alteration were reconstructed. ► Paleo-temperatures point to different life habitats of the specimens. ► Alteration points to mixing of two end-members by meteoric diagenesis. ► HMC-mineralogy was determined for first time for orthoconic nautiloids.