The paleoenvironmental context and diagenetic history of the middle Frasnian Escuminac Formation were investigated through geochemical (rare earth elements) and isotopic (Rb–Sr, Nd–Sm) analyses of fossil fish material and sediments. Samples of sediments and bioapatite were collected from the base to the top of the Escuminac Formation.

Strontium isotope ratios (87Sr/86Sr) for bioapatites vary from 0.70804 to 0.70845 and overlap with Frasnian seawater Sr isotope compositions, though most of the biogenic apatites analyzed show a variable drift from marine values toward a more radiogenic continental signature. This trend is possibly the result of post-mortem Sr exchange between fossils and a fluid isotopically distinct from the waters in which they developed.