Gib04a (entity_id = 182): The age model was based on counting back annual cycles in d13C which were known to be forced by reversing seasonal ventilation from cave monitoring. Annual cycles in d13C mapped onto the paired laminae. Minima in d13C represents calcite deposited in late winter (April). The age model was validated by the position of the radiocarbon bomb peak and a high correlation between the d18O of net winter calcite and the corresponding weighted mean of monthly rainfall from the GNIP record. Uncertainty of the age model varies from 0 to c. 1980 thereafter +/-1 year for the older part of the record.