Nauru Island Coral Based Radiocarbon Data: Readme file

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                   NOAA Paleoclimatology Program
                               and
              World Data Center A - for Paleoclimatology
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NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!!

NAME OF DATA SET: Nauru Island Coral Radiocarbon
LAST UPDATE: 8/1999 (Original Receipt by WDCA Paleo) 

CONTRIBUTORS: T. Guilderson (1,2), D. Schrag (1), M. Kashgarian (2), 
			   and J. Southon (2)
1. 	Dept. of Earth & Planetary Sciences
	Harvard University
	Cambridge MA  02138
2.	Center for Accelerator Mass Spectrometry
	LLNL, L-397
	Livermore CA  94551
	
	
IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 1999-043

SUGGESTED DATA CITATION: Guilderson, T.P., et al, 1999,
Nauru Island Coral Radiocarbon Data, IGBP PAGES/
World Data Center A-Paleoclimatology Data Contribution Series #1999-043. 
NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. 


ORIGINAL REFERENCE: Guilderson, T.P., D.P. Schrag, M. Kashgarian
and J. Southon, 1998.  Radiocarbon Variability in the Western 
Equatorial Pacific Inferred from a High-Resolution Coral Record from 
Nauru Island J. of Geophysical Research 103, 24641-24650.

Additional References:
 
Stuiver, M., and H. A. Polach, Discussion and reporting of
14C data,  Radiocarbon, 19, 355-363, 1977.

Vogel, J. S., J. R. Southon, and D. E. Nelson, Catalyst and binder
effects in the use of filamentous graphite for AMS, Nucl. Instrum. 
Methods Phys. Res., Sect.B, 29, 50-56, 1987.

Davis, J. C., et al..,  LLNL/UC AMS facility and research program,
Nucl. Instrum. Methods Phys. Res., Sect. B, 52, 269-272, 1990.

Guilderson, T.P., and D.P. Schrag, Reliability of coral isotope records 
from the western Pacific warm pool: A comparison using age-optimized 
records (1999PA900024), Paleoceanography, 14, 457-464, 1999.
 
 
GEOGRAPHIC REGION: western tropical Pacific

PERIOD OF RECORD: 1947-1995 AD

FUNDING SOURCES: (US) NSF, Lawrence Livermore National Laboratory

LIST OF FILES: readme.nauru14c.txt (this file), tab-delimited ASCII 
data file nauru14c.txt.
Variable names  CAMS#/DATE/Delta-14C  (integer/time/per mil)
missing data (NaN)

LONGITUDE: 166E
LATITUDE:  0.5S
WATER DEPTH:  14m
CORAL SPECIES: Porites spp.
CORE LENGTH: 1.6 meters
DATE OF COLLECTION: July 1995

DESCRIPTION: 
Nauru-2 coral radiocarbon (14C) timeseries.
(166E, 0.5S, 14m bottom depth)

Coral radiocarbon (Delta-14C) on untreated, low-speed drilled 
samples. Precision is ±4 per mil as documented by an in-house 
homogenized coral standard, and presented as AGE CORRECTED DELTA-14C 
[see Stuiver & Polach, 1977].

Cores were taken from a 1.6 meter Porties spp coral on the north side 
of Nauru Island (166E 0.5S), 14m bottom depth, in July of 1995 by D. 
Schrag & M. Moore. Cores were split and cleaned with distilled water.  
After identifying the major vertical growth axis, the coral was 
sequentially sampled at 2 mm increments with a low-speed drill. 
Splits (~1 mg) were reacted in vacuo in a modified autocarbonate 
device at 90¡C and the purified CO2 analyzed on a gas source stable 
isotope ratio mass spectrometer. The remaining sample splits 
(~10 mg) were placed in individual reaction chambers, evacuated, 
heated, and then acidified with orthophosphoric acid at 90¡C.  The 
evolved CO2 was purified, trapped, and converted to graphite in the 
presence of cobalt catalyst in individual reactors [Vogel et al., 1987].
Graphite targets were measured at the Center for Accelerator Mass 
Spectrometry, Lawrence Livermore National Laboratory [Davis et al., 
1990].  Radiocarbon results are reported as Delta-14C (ä) as defined 
by Stuiver and Polach [1977] and include the d13C correction obtained 
from the stable isotope results.  Analytical precision and accuracy 
of the radiocarbon measurements is ±4ä (1s) based on repeated
analyses of an in-house homogenized near-modern coral and accepted
secondary and tertiary radiocarbon standards.  

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In keeping with the definition of "high-precision radiocarbon" 
(<3 per mil, 1-sigma) data have been rounded to zero significant 
figures.  The age model for these data was derived from a 
preliminary delta-13C age model which was then optimized by mapping
the delta-18O data to a local instrumental precipitation record.  
Age model errors are estimated (brute force approach) at ±2-3 months.