Macrofauna of the Cantera de Margas section, Olazagutia: Coniacian/Santonian boundary, Navarro-Cantabrian Basin, northern Spain

The occurrence of macrofossils in the Cantera de Margas section at Olazagutia, an expanded sequence across the Coniacian/Santonian boundary in the Navarro-Cantabrian Basin (northern Spain), is documented in detail, with taxa recognised illustrated and their distribution discussed. The Cantera de Margas section was considered to be currently the most suitable C/S boundary stratotype section at the Meeting on the Coniacian/Santonian Boundary in Bilbao. The first occurrence (FO) of the fairly common inoceramid bivalve Platyceramus undulatoplicatus (Römer) is the primary marker for this boundary. Additional criteria for correlation are provided by the FOs of the inoceramid Magadiceramus subquadratus subquadratus (Schlüter) (index species of the M. subquadratus Zone), and the echinoids Cardiaster integer (Agassiz), Offaster nuciformis Ernst and Micraster brevis Desor, below the boundary, and of the inoceramids Platyceramus cycloides cycloides (Wegner) and Cordiceramus cordiinitialis (Seitz) (index species of the C. cordiinitialis Zone) and the echinoids Echinocorys gr. scutata Leske and Micraster matheroni Desor above it. Ammonites are rare and occur far above the boundary.