Milankovitch cycles in the upper part of the Toa Baja drillhole, detected by geophysical logs, are used to estimate sedimentation rates, and to localize the depth at which sedimentation rate changes occur. The log-derived age information is then combined with reference dates from palaeontological data and the ''Vail'' global sea-level curve to build a detailed record of the chronology of the upper stratigraphic sequence in the well. ¿American Geophysical Union 1991