Planktic and Benthic 14C Reservoir Ages for Three Ocean Basins, Calibrated by a Suite of 14C Plateaus in the Glacial-to-Deglacial Suigetsu Atmospheric 14C Record. Issue 1 (2015)

• Record Type: Journal Article
• Authors: Sarnthein, Michael; Balmer, Sven; Grootes, Pieter M; Mudelsee, Manfred
• Is Part Of: Radiocarbon. Volume 57:Issue 1(2015)
• Page Start: 129
• Page End: 151
• Publication Date: 2015
• Subjects: Radiocarbon dating -- Periodicals; 930.1028505
• DOI: 10.2458/azu_rc.57.17916
• Languages: English
• ISSNs: 0033-8222

Abstract

Abstract : This article presents a compilation of planktic and benthic 14 C 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 14 C 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 (Δ 14 C values) for surface and deep waters by comparing the suite of planktic 14 C plateaus of a sediment record with that of the atmospheric 14 C record. Results published thus far have used as atmospheric 14 C reference U/Th-dated corals, the Cariaco planktic record, and speleothems. We have now used the varve-counted atmospheric 14 C record of Lake Suigetsu terrestrial macrofossils to recalibrate the boundary ages and reservoir ages of the seven published records directly to an atmospheric 14 C 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 14 C record on its varve-counted timescale reflects all 14 C plateaus, their internal structures, and relative length previously identified, but implies a rise in the average 14 C plateau age by 200–700 14 C yr during the LGM and early deglacial times. (2) Based on different 14 C ages of coeval atmospheric and planktic 14 C plateaus, marine surface water Δ 14 C may have temporarily dropped to an equivalent of ∼0 yr in low-latitude lagoon waters, but reached >2500 14 C 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 Δ 14 C value of 400 yr. (3) Suites of deglacial planktic Δ 14 C values are closely reproducible in 14 C records measured at neighboring core sites. (4) Apparent deep-water 14 C ventilation ages (equivalents of benthic Δ 14 C), deduced from the sum of planktic Δ 14 C and coeval benthic-planktic 14 C differences, vary from 500 up to >5000 yr in LGM and deglacial ocean basins.