Ostracod was dated from core sample 14/15-VIII-80 at a depth of 335 cm. Maize pollen began to appear in Zone 3 at 580 cm and continued to appear sporadically until the present day (Leyden et al. 1998:115-116, Table 1).
Leyden, B. W., M. Brenner and B. H. Dahlin 1998 Cultural and climatic history of Cobá, a Lowland Maya city in Quintana Roo, Mexico. Quaternary Research 49(1):111-122.