Cariaco basin calibration update:: Revisions to calendar and 14C chronologies for core PL07-58PC

Calibration of the radiocarbon time scale is critical in order to fully utilize this important dating tool as a tracer of geochemical and geophysical processes. Tree-ring chronologies provide high-resolution calibration back to similar to 12,400 cal BP (Friedrich et al., this issue), but dendrochronologies beyond that age are currently "floating" and not anchored in absolute age (Kromer et al., this issue). For the previous IntCal98 data set (Stuiver et al. 1998), high-resolution calibration data older than tree rings were provided by Cariaco Basin piston core PL07-PC56 (Hughen et al. 1998). Core 56PC was selected for C-14 dating from a suite of 4 adjacent piston cores, mostly due to the quality of its high-resolution grayscale record. The core was sampled every 10 cm, yielding approximately 100- to 200-yr resolution. Cariaco piston core PL07-58PC, on the other hand, has a similar to 25% higher deposition rate than 56PC (Peterson et al. 1990). Core 58PC was sampled every 1.5 cm, providing C-14 calibration at 10-15 yr resolution throughout the period of deglaciation, similar to 10,500-14,700 cal BP (Hughen et al. 2000). Until now, however, these data were never converted into a smoothed curve or combined with other data sets for use in calibration. The methodologies for combining 58PC data with tree-ring and coral data for the IntCal04 atmospheric and marine C-14 calibration curves are described elsewhere in this volume (Reimer et al., this issue; Hughen et al., this issue). Here, we present the updated anchoring of the floating Cariaco varve chronology to the revised and extended German pine chronology (Friedrich et al., this issue). In addition, we detail the changes made to the calendar age varve chronology between the publication of the 56PC and 58pC C-14 calibrations, and summarize the C-14 sample treatment and statistics for accelerator mass spectrometry (AMS) measurement of blanks and small samples for this work.