The Imprints of Cenozoic Calcareous Nannofossils from Polymetallic Concretions: Biostratigraphic Significance for two Crusts from the Central Pacific (Line Islands Ridge and Mid-Pacific Mountains)

Resume 121 Abstract SEM investigation of manganese nodules and crusts dredged in diverse deep-sea areas has shown many imprints of calcareous nannofossils assigned to more than 30 Cenozoic species. In two Cobalt-containing crusts from the central Pacific (Line Islands Ridge and Mid-Pacific Mountains), the ex­ ceptional grain fineness of the manganese oxide allowed to identify for the first time the molds of very small forms, such as C. gr. murrayi, E. huxleyi, Gephyrocapsa ssp. and R. claviger. The encountered nannofossils demonstrate that these concretions have grown during two main periods between early Pliocene and Recent.