Marine-derived 14C calibration and activity record for the past 50,000 years updated from the Cariaco Basin

An expanded Cariaco Basin C-14 chronology is tied to Th-230-dated Hulu. Cave speleothem records in order to provide detailed marine-based C-14 calibration for the past 50,000 years. The revised, high-resolution Cariaco C-14 calibration record agrees well with data from Th-230-dated fossil corals back to 33 ka, with continued agreement despite increased scatter back to 50 ka, suggesting that the record provides accurate calibration back to the limits of radiocarbon dating. The calibration data document highly elevated Delta (14) C during the Glacial period. Carbon cycle box model simulations show that the majority of observed A C-14 change can be explained by increased C-14 production. However, from 45 to 15 ka, A C-14 remains anomalously high, indicating that the distribution of radiocarbon between surface and deep ocean reservoirs was different than it is today. Additional observations of the magnitude, spatial extent and timing of deep ocean A C-14 shifts are critical for a complete understanding of observed Glacial A C-14 variability. (c) 2006 Elsevier Ltd. All rights reserved.