PLANKTIC AND BENTHIC C-14 RESERVOIR AGES FOR THREE OCEAN BASINS, CALIBRATED BY A SUITE OF C-14 PLATEAUS IN THE GLACIAL-TO-DEGLACIAL SUIGETSU ATMOSPHERIC C-14 RECORD

摘要

This article presents a compilation of planktic and benthic C-14 reservoir ages for the Last Glacial Maximum (LGM) and early deglacial from 11 key sites of global ocean circulation in the Atlantic and Indo-Pacific Ocean. The ages were obtained by C-14 plateau tuning, a robust technique to derive both an absolute chronology for marine sediment records and a high-resolution record of changing reservoir/ventilation ages (Delta C-14 values) for surface and deep waters by comparing the suite of planktic C-14 plateaus of a sediment record with that of the atmospheric C-14 record. Results published thus far have used as atmospheric C-14 reference U/Th-dated corals, the Cariaco planktic record, and speleothems. We have now used the varve-counted atmospheric C-14 record of Lake Suigetsu terrestrial macrofossils to recalibrate the boundary ages and reservoir ages of the seven published records directly to an atmospheric C-14 record. In addition, the results for four new cores and further planktic results for four published records are given. Main conclusions from the new compilation are the following: (1) The Suigetsu atmospheric C-14 record on its varve-counted timescale reflects all C-14 plateaus, their internal structures, and relative length previously identified, but implies a rise in the average C-14 plateau age by 200-700 C-14 yr during the LGM and early deglacial times. (2) Based on different C-14 ages of coeval atmospheric and planktic C-14 plateaus, marine surface water Delta C-14 may have temporarily dropped to an equivalent of similar to 0 yr in low-latitude lagoon waters, but reached > 2500 C-14 yr both in stratified subpolar waters and in upwelled waters such as in the South China Sea. These values differ significantly from a widely assumed constant global planktic.C-14 value of 400 yr. (3) Suites of deglacial planktic.C-14 values are closely reproducible in C-14 records measured at neighboring core sites. (4) Apparent deep-water C-14 ventilation ages (equivalents of benthic Delta C-14), deduced from the sum of planktic.C-14 and coeval benthic-planktic C-14 differences, vary from 500 up to > 5000 yr in LGM and deglacial ocean basins.