22 samples collected from Yop and Codon Formations in Catanduanes Island,Philippines were analyzed for calcareous nannofossil content in order to refine the age of the lithostratigraphic units.Preliminary analysis yielded very rare to few occurrences of 47 species belonging to 27 genera with most specimens poorly-to moderately-preserved.Based on the presence of the marker taxa Quadrum intermedium and Helenea chiastia,the samples from northeast Catanduanes (possibly from the Yop Formation) were assigned to the UC5c Nannofossil Zone,within the Cenomanian-Turonian boundary.