Differential dissolution of upper Cretaceous deep-sea benthonic foraminifers from the Angola Basin,South Atlantic Ocean

Material from the Deep Sea Drilling Project (DSDP) Site 527 from the Angola Basin, South Atlantic Ocean, has been analyzed to determine whether Upper Cretaceous benthonic foraminiferal taxa are differentially sensitive to calcite dissolution, and, if so, to rank their order of susceptibility. Two regimes of dissolution, established on the basis of the degree of planktonic foraminiferal fragmentation, representing stronger and less prominent dissolution within the section studied, were used as a framework for reference. A total of 60 calcareous and eight agglutinated benthonic foraminiferal taxa were identified at the species or genus level; of these, twenty-three calcareous and five agglutinated taxa were selected for the dissolution study. Relative abundance of each of the various taxa was tested statistically, using t-test, between dissolution regimes to assess the significance of the change induced by increased dissolution.Nuttallides truempyi andNeoeponides sp. intermediate form are interpreted as resistant to dissolution.Pullenia spp.,Alabamina sp. a,Anomalina sp. a,Praebulimina sp. fusiform, andNuttallinella sp. a are susceptible to dissolution. The majority of the taxa (16 in number) are unaffected by dissolution because they show no change between dissolution regimes. Among the agglutinated taxaGaudryina pyramidata is resistant to dissolution, whereas the remaining four taxa are unaffected by dissolution. At the level of superfamilies, one calcareous superfamily (Discorbacea) is resistant, two (Orbitoidacea and Cassidulinacea) are unaffected, and two (Nodosariacea and Buliminacea) are susceptible to dissolution.