Elemental abundance anomalies in the late Cenomanian extinction interval: A search for the source(s)

Elemental abundances have been measured by neutron activation methods across the Cenomanian-Turonian (late Cretaceous) extinction interval in samples collected from sixteen sites in the Western Interior Basin of North America and from twelve widely separated locations around the globe, including six ODP/DSDP sites. In most Western Interior Basin sites, in Colombia, and in western Europe (weaker), two closely spaced elemental abundance peaks occur in the upper Cenomanian (∼ 92 m.y.), spanning the ammonite zones ofSciponoceras gracile throughNeocardioceras juddii. Elements with anomalously high concentrations include Sc, Ti, V, Cr, Mn, Co, Ni, Ir, Pt and Au. The lower peak coincides with the disappearance (extinction) of the foraminiferRotalipora cushmani. In North American sectionsR. greenhornensis also disappears at or just below this horizon, but in Europe it disappears considerably earlier thanR. cushmani. A series of molluscan extinction and speciation or migration events also begins near the stratigraphic level of the lower elemental abundance peak.