Rare earth element deposition in pelagic sediment at the CenomanianTuronian Boundary, Exmouth Plateau

ODP Site 762 (eastern Indian Ocean) includes a section of sediment that spans the Cenomanian-Turonian Boundary (CTB) and was deposited along a continental margin during a period of widespread oceanic 09. deficiency. The rare earth element (REE) content of preand post-boundary sediment is similar to that of present-day continental slope material deposited in well-oxygenated seawater, whereas the CTB section is characterized by significantly depleted REE abundances, a bulk Ce anomaly that increases to maximum of 1.0, and a REE pattern that resembles that of present-day fluvial material. We suggest the change in REE patterns reflects release of scavenged REEs upon reductive dissolution of authigenic Fe-Mn oxyhydroxides, such that sediment deposited uring the CTB is dominated by the lithogenous REE fraction. These results are consistent with recent models concerning pervasive fractionation of Mn and Fe and redirection of Mn in pelagic CTB waters.