A NEW C-14 CALIBRATION DATA SET FOR THE LAST DEGLACIATION BASED ON MARINE VARVES

Varved sediments of the tropical Cariaco Basin provide a new C-14 cali bration data set for the period of deglaciation (10,000 to 14,500 year s before present: 10-14.5 cal ka sp). Independent evaluations of the C ariaco Basin calendar and C-14 chronologies were based on the agreemen t of varve ages with the GISP2 ice core layer chronology for similar h igh-resolution paleoclimate records, in addition to C-14 age agreement with terrestrial 14C dates, even during large climatic changes. These assessments indicate that the Cariaco Basin C-14 reservoir age remain ed stable throughout the Younger Dryas and late Allerod climatic event s and that the varve and C-14 chronologies provide an accurate alterna tive to existing calibrations based on coral U/Th dates. The Cariaco B asin calibration generally agrees with coral-derived calibrations but is more continuous and resolves century-scale details of C-14 change n ot seen in the coral records. C-14 plateaus can be identified at 9.6, 11.4, and 11.7 C-14 ka BP, in addition to a large, sloping ''plateau'' during the Younger Dryas (similar to 10 to 11 C-14 ka sp). Accounting for features such as these is crucial to determining the relative tim ing and rates of change during abrupt global climate changes of the la st deglaciation.