Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • BCO-DMO Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information
• Funding

Dataset: Radionuclides, sediment cores
PI: Bob Anderson
of: Lamont-Doherty Earth Observatory
Project/cruise: EqPac/TT013, Benthic survey
Ship: R/V Thomas Thompson
Original version date (v1): April 22, 2002

Version 2 of this dataset was processed on November 18, 2025. In this update, four new values for the opal content of sediment have been added to piston core 18,. The principal change is that the number of samples analyzed for piston core 72 is approximately double the number of samples reported previously in version 1.

Radionuclide analytical methodologies, sediment samples
Methodology originally published at: https://usjgofs.whoi.edu/PI-NOTES/Anderson_rad_sed_core.html
January 8, 2002
Bob Anderson, Lamont-Doherty Earth Observatory
EqPac TT013 Benthic Survey

U, Th and Pa were measured by isotope dilution alpha spectrometry; 10Be by accelerator mass spectrometry. The reference that best described the methods followed for measuring U, Th, Pa and 10Be in sediment samples is:

Y. Lao, R.F. Anderson, W.S. Broecker, H.J. Hofmann and W. Wolfli, Particulate fluxes of 230Th, 231Pa, and 10Be in the Northeastern Pacific Ocean, Geochimica Cosmochimica Acta 57(1), 205-217, 1993.

CaCO3 and opal were measured in the Lamont sediment laboratory (a semi-commercial operation) by standard methods (coulometry for CaCO3; spectrophotometry following alkaline leach for opal).

14C ages were obtained by accelerator mass spectrometry using bulk CaCO3 at the US AMS facility in Arizona.

Notes:
Each sample is a one-centimeter sample centered on the depth indicated by the parameter depth_core.

C14 ages were obtained by the University of Arizona Accelerator Mass Spectrometer (AMS) Facility using bulk sediment CaCO3. C14 age values uncorrected.

Error bars for all variables are plus or minus one sigma.

Based on a comparison of Piston core and Trigger core for station/core 32, it appears that about 10 (cm) of sediment was lost from the top of the piston core. Thus core 32, samples at 5.5 and 10.5 (cm) are from trigger core.

Version History:
Version 1
Version Date 2002-04-22
This dataset was originally processed and published by Cynthia Chandler on 2002-04-22 as part of the JGOFS EqPac Project. The original file name was "rad_sed_core.tsv". This file was accompanied by several metadata files, which are attached here as Supplemental Files.

On 2025-09-29, Shannon Rauch made the following adjustments:
- Imported the original jgofs file "rad_sed_core.tsv" into our current processing system.
- Saved the data file in CSV format as "985428_v1_rad_sed_core.csv".

Version 2
Version Date 2025-11-18
Replaced version 1 file with version 2, in which four new values for the opal content of sediment have been added to piston core 18. The principal change is that the number of samples analyzed for piston core 72 is approximately double the number of samples reported previously for dataset 985428 (V1).
BCO-DMO Processing Steps:
- Imported original, revised file "985428_v2_rad_sed_core.xlsx" into the BCO-DMO system.
- Marked "nd" as a missing data value (missing data are empty/blank in the final CSV file).
- Saved the final file as "985428_v2_rad_sed_core.csv".

The U.S. EqPac process study consisted of repeat meridional sections (12°N -12°S) across the equator in the central and eastern equatorial Pacific from 95°W to 170°W during 1992. The major scientific program was focused at 140° W consisting of two meridional surveys, two equatorial surveys, and a benthic survey aboard the R/V Thomas Thompson. Long-term deployments of current meter and sediment trap arrays augmented the survey cruises. NOAA conducted boreal spring and fall sections east and west of 140°W from the R/V Baldridge and R/V Discoverer. Meteorological and sea surface observations were obtained from NOAA's in place TOGA-TAO buoy network.

The scientific objectives of this study were to determine the fluxes of carbon and related elements, and the processes controlling these fluxes between the Equatorial Pacific euphotic zone and the atmosphere and deep ocean. A broad overview of the program at the 140°W site is given by Murray et al. (Oceanography, 5: 134-142, 1992). A full description of the Equatorial Pacific Process Study, including the international context and the scientific results, appears in a series of Deep-Sea Research Part II special volumes:

Topical Studies in Oceanography, A U.S. JGOFS Process Study in the Equatorial Pacific (1995), Deep-Sea Research Part II, Volume 42, No. 2/3.

Topical Studies in Oceanography, A U.S. JGOFS Process Study in the Equatorial Pacific. Part 2 (1996), Deep-Sea Research Part II, Volume 43, No. 4/6.

Topical Studies in Oceanography, A U.S. JGOFS Process Study in the Equatorial Pacific (1997), Deep-Sea Research Part II, Volume 44, No. 9/10.

Topical Studies in Oceanography, The Equatorial Pacific JGOFS Synthesis (2002), Deep-Sea Research Part II, Volume 49, Nos. 13/14.

The United States Joint Global Ocean Flux Study was a national component of international JGOFS and an integral part of global climate change research.

The U.S. launched the Joint Global Ocean Flux Study (JGOFS) in the late 1980s to study the ocean carbon cycle. An ambitious goal was set to understand the controls on the concentrations and fluxes of carbon and associated nutrients in the ocean. A new field of ocean biogeochemistry emerged with an emphasis on quality measurements of carbon system parameters and interdisciplinary field studies of the biological, chemical and physical process which control the ocean carbon cycle. As we studied ocean biogeochemistry, we learned that our simple views of carbon uptake and transport were severely limited, and a new "wave" of ocean science was born. U.S. JGOFS has been supported primarily by the U.S. National Science Foundation in collaboration with the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the Department of Energy and the Office of Naval Research. U.S. JGOFS, ended in 2005 with the conclusion of the Synthesis and Modeling Project (SMP).