(Table T3) Potassium oxide, uranium and thorium concentration in ODP Site 195-1201 sediments, supplement to: Dean, Simon M (2004): Analysis of NGR spectra from deep-sea sediments in the Philippine Sea, Site 1201. In: Shinohara, M; Salisbury, MH; Richter, C (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 195, 1-33


Natural gamma ray measurements are made routinely during core logging using the physical property multisensor track. The instrument provides a measure of the natural decay of radioactive elements in the core, expressed in counts per second, which is generally used as a proxy for the clay content of nonmarginal marine sediments. At Site 1201 spikes of increased gamma ray emissions, up to six times the average for the entire core over depth intervals on the order of 20-50 cm, are observed from the sediments within 50 m of the basement contact. The spikes show a strong correlation with sediment color variations, coinciding with red/brown layers within otherwise green/gray-colored sediments. In this paper, the gamma ray spectra obtained from 21 measurements using a 4-hr counting period are analyzed to obtain the absolute concentration of the radioactive elements K2O, U, and Th in both the intervals with spikes and the intervals with relatively low count rates. In addition, the concentration of these elements is estimated using the spectra obtained from the routine 20-s counting period measurements and which, although exhibiting a great deal of scatter due to the high statistical uncertainty in the original measurements, are roughly similar to those obtained from the 4-hr counting period. Baseline concentrations for U (1 ppm) and Th (5 ppm) match published averages for the amount present in deep-sea clays; the peak concentrations measured correspond to an additional concentration of 100%-200%. The results are compared to those from downhole logging and shipboard inductively coupled plasma-atomic emission spectrometry measurements. The gamma ray spectra results do not support postdepositional fluid flow through the sediment as the source of the enrichment of radioactive elements. It is more likely that the spikes in the gamma ray emissions are simply the result of interbedding sediments from two different sources, one with relatively high concentrations of K2O, U, and Th.

DOI https://doi.org/10.1594/PANGAEA.779130
Related Identifier https://doi.org/10.2973/odp.proc.sr.195.105.2004
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.779130
Creator Dean, Simon M
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2004
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Language English
Resource Type Supplementary Dataset; Dataset
Format text/tab-separated-values
Size 63 data points
Discipline Earth System Research
Spatial Coverage (135.099 LON, 19.298 LAT); Philippine Sea
Temporal Coverage Begin 2001-03-31T00:00:00Z
Temporal Coverage End 2001-04-25T00:00:00Z