Isotopic variation in late Cenomanian to early Turonian foraminifera and matrix from DSDP site 551 (Goban Spur, Northeast Atlantic)

Stable isotopic measurements have been made on both planktonic foraminifera and coccolith-rich matrix of Cretaceous (latest Cenomanian-early Turonian) age from DSDP site 551 (Goban Spur, Northeast Atlantic). The foraminifera display a δ18O range of - 1.1 to -2.2 %o (PDB) whilst the δ13C values are confined to a narrower range of 2.0 to 2.1 ‰ (PDB). The preservation of the foraminifera has been assessed through geochemistry and scanning electron microscopy and indicates that they show evidence of some diagenetic alteration. Consequently palaeotemperature estimates using these values are deemed to be in general unreliable. The δ13C of the matrix (in conjunction with published data) show heaviest values during the latest Cenomanian. The data are thus consistent with the widely observed positive carbon isotope excursion associated with the latest Cenomanian oceanic anoxic event.