Identlficatlon of the Campanian stage by means of calcareous nannofossils: review ano state of the art

Abstract

The paper presents and discusses the central aspects of characterization of the boundaries of the Campanian and i//ustrates the evolution and state of the art of concepts entai/ing recognition of this stage based on calcareous nannofossils. The base of the Campanian is usual/y placed between the appearance of Aspidolithus parcus and the extinction of Lithastrinus grillii anel/or Marthasterites furcatus. According to most authors, the levei of the appearance of A. pareus coincides with the Santonian/Campanian boundary, or may lie immediately below it. Extinction of L. grillii andlor M. fureatus is believed to have occured in the oldest part of the Campanian. The CampanianlMaestrichtian boundary is placed between the appearance and extinction of Quadrum trifidum. A more precise individualization involves otherspecies, however, some of which, according 
to certain researchers, displaydiachronous extinction (e. g., Eiffellithus eximius and Reinhardtites anthophorus). There have been several phases in identification and delimilation of the Campanian on lhe Brazilian continental margin. It is current/y believed that the SantonianlCampanian boundary is best placed below the levei of extinction of M. fureatus andlor L. grillii. These extinctions, rather than having occurred in Campanian times as defended by a number of researchers, are believed to having occurred sometime near the end of the Santonian, as suggested by correlations with other fossil groups (foraminifers and palynomorphs). The upper limit of the Campanian was initià//y identified by the extinction of A. parcus, later being identified by the last occurrence of E. eximius. In accordance with concepts stated in lhe literature on nannofossils, it is currently believed that the end of lhe stage is located between the two extinctions .