Fig. 8From: Geochemical evidence (C and Sr isotopes) for methane seeps as ammonite habitats in the Late Cretaceous (Campanian) Western Interior Seaway 87Sr/86Sr isotope ratios in well-preserved mollusc shells from methane seep at AMNH loc. 3418 (D. cheyennense Zone). Values are consistently elevated above the coeval seawater ratio (shown as solid horizontal line; McArthur et al. 1994)Back to article page