Diagenesis of Inoceramus and late Cretaceous paleoenvironmental geochemistry: a case study from James Ross Island, Antarctica

Inoceramid bivalves and dimitobelid belemnites from the Santonian-Campanian of James Ross Island, Antarctica, were analyzed for their isotopic and elemental geochemistry. On the basis of petrographic and cathodoluminescence studies and minor element data, the dimitobelid belemnites show minimal diagenetic modification. These data are interpreted in terms of a stratified water column model. Epifaunal inoceramid bivalves are thought to have lived in bottom waters where the isotopic composition was modified by pore waters expelled from the underlying compacting volcaniclastic sediments. In contrast, the nektonic belemnites were living within more «normal» marine conditions. Paleotemperatures calculated from the isotopic composition of the belemnites give an average of 13.6°C for the «normal» marine waters. However, paleotemperatures based on the inoceramid bivalve data imply considerably higher values