PeeDee belemnite

Because variations in accurate isotope ratio measurements typically concern only a few parts per 1000 by mass and there are no universal absolute ratios, it is necessary to define some standards. For this purpose, samples of standard substances are produced and made available at two major centers IAEA (International Atomic Energy Authority, U.K.) and NIST (National Institute for Standards and Technology, U.S.). Standards from other sources are also available. These primary standards can be used as such, or alternative standards can be employed if the primary ones are not available. However, any alternative standards need to be related accurately to the primary ones (see formulae below). For example, the material PDB (PeeDee belemnite), used particularly as a standard for the ratio of isotopes, is no longer readily available, and a new standard, VPDB,... 

MS", application of successive mass spectrometric measurements n of them), particularly in linked scanning of m/z, which is the ratio of the mass (m) of an ion and the number of charges (z) on it. Older publications used m/e, but as e is the actual charge on an electron and not the number of charges on the ion, the use of m/e was abandoned, m/z. mass-to-charge ratio, a measure of molecular mass PDB. PeeDee Belemnite (a carbon isotope standard see VPDB)... 

VPDB. Vienna PeeDee Belemnite (a replacement for the PDB isotope standard)... 

Measurements of carbon and nitrogen stable-isotope ratios were made by using a Finnigan MAT 251 or a Delta S isotope-ratio mass spectrometer. Results are reported versus atmospheric nitrogen (N) or PeeDee Belemnite (C) as standards and calculated as ... 

Standard deviation (lc) of die mean of each sample set is reported. VPDB - Vienna Peedee belemnite. Two pedogenic carbonate data points have been excluded, one that shows much higher temperatures relative to other pedogenic nodules of the same age (based on A47 measurement) and one that has a much higher 5180 relative to other pedogenic nodules of the same age. 

Figure 6 The isotopic fractionation, expressed as the difference between the 5 0 of foraminiferal calcite and the 5 0 of seawater (converted from SMOW to a Peedee Belemnite (PDB) like scale by subtracting 0.27 in accordance with paleoceanographic tradition) versus temperature of calcification. Cibicidoides and Planulina from...

The usual reference for water is standard mean ocean water (SMOW). However, oxygen (and carbon) isotope ratios in speleothems are often reported using the PDB (Peedee belemnite) standard (Faure, 1986). Currently, one should report relative to the VPDB standard. 

The original application of oxygen isotope thermometry. The thermal history (top) of the surroundings in South Carolina, USA, during the Cretaceous period as recorded by oxygen isotope changes (bottom) as a function of shell radius in the PeeDee belemnite (Urey et a/., 1951). 

One of the first apphcations of the paleotemperature method was undertaken by Harold Urey et al. (1951), who analyzed incremental sections along the radius of the shell of a fossil belemnite (a type of cephalopod). This bullet-shaped shell, from the Cretaceous PeeDee formation of South Carolina, was the original standard material for 5 C analysis (Table 5.2). The isotopic diary of the PeeDee belemnite (Fig. 5.4) records four cool extremes separated by three warm periods, in what appears to be 3.5 y of life history laid down approximately sixty million years ago. The absolute temperature scale is uncertain, because the 5 0 of the ancient sea where the belemnite lived is unknown. 

Abbreviations V-SMOW = Vienna Standard Mean Ocean Water [15] V-PDB = Vienna PeeDee Belemnite (Carbonate) [16, 17] AIR-N2 atmospheric N2 [18-20] V-CDT = Vienna Canon Diablo Troilite [21-23]... 

Figure 2. Schematic diagram showing differences in photosynthetic pathways for C3 vs. C4 terrestrial plants, which yield different C-isotope fractionations in plant tissue. Phosphoglycerate (PGA), oxaloacetate (OAA), malate, and pyruvate are organic compounds that participate in photosynthesis, and Rubisco and PEPc are enzymes that catalyze reactions among these organic compounds and CO2. Solid arrows show flow of organic molecules within and across cell dashed arrow shows that some CO2 can leak out of bundle sheath cells. See text for more detail. Permil values are all relative to Vienna Peedee Belemnite (V-PDB).

Figure 5 Sea water <5 C recorded in ancient carbonate sediments (Ottawa-Bochum database http //www.science. uottawa.ca/geology/isotope data/). Timescale as Figure 1. ppt PDB = parts per thousand PeeDee Belemnite.

PeeDee Belemnite (PDB) Oxygen and carbon isotope ratios are measured as relative deviations (5 0 per mil 5 C per mil) from a laboratory standard value. The standard normally employed for the analysis of carbonates is a PDB limestone (belemnite shell from the Cretaceous Peedee Formation of South Carolina). 

Analytically, the separated gases have to be combusted to form CO2 for measurements and the H2O formed is turned into H2, which is measured for D. The standard for carbon isotopes is usually PDB (Peedee Belemnite, a carbonate) though the oil industry also uses the NBS22 (an oil fraction), whereas the standard is SMOW (Standard Mean Ocean Water). 

The standards are limited by the availability of the material in the environment and can only be acquired by users once every 3 years. A number of standards are no longer available, for example, PeeDee Belemnite (PDB). As a result, laboratories must evaluate and calibrate laboratory (or working) standards traceable to the certified reference materials for day-to-day measurements. 

FIGURE 15.1 An overview of the natural variations in the carbon isotopic composition of a range of materials. Reprinted from T.B. Coplen et al. [16], with permission from Coplen. NBS, National Bureau of Standards L-SVEC, lithium carbonate IAEA, International Atomic Energy Agency NGS, natural gas standards RM, reference material CAM, Crassulacean acid metabolism USGS, U.S. Geological Survey VPDB, Vienna PeeDee Belemnite. 

Aliquots of CO2 produced during 0-plasmas were analyzed on three different stable isotope-ratio mass spectrometers over a period of five years. The peyote button and the T-shirt label were both run in the summer of 2001. These two samples were chosen to further establish that mass fractionation of carbon during the oxygen plasmas is a small or negligible effect and to test the nondestructive nature of the technique on organic materials. For calibration to Peedee belemnite (PDB) primary standard, carbonate standard NBS-19 (8 C = 1.95%o) was used (i.e., Vienna PDB). values are expressed relative to the V-PDB standard (19). Analytical precision was approximately 0.06%o for 6 C. 

PDB Peedee Belemnite, a calcium carbonate used as a reference material in SIR measurements... 

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