Peedee formation

The most widely used standard is a belemnite from the Peedee Formation in South Carolina (PDB) therefore, some ratios may be expressed as negative values. Most carbon isotope ratio correlations are made on the C15+ fraction of crude oil because it is less affected by degradation processes. Valid correlations using carbon isotopes can only be conducted on the same fractions of samples. 

C BelemniteUa americana from the Cretaceous Peedee formation. South Carohna V-PDB... 

It has an I80 / 160 ratio of 2005.20 ( 0.45) x 106 (Baertschi, 1976). In many studies involving carbonates, PDB is the standard relative to which values are reported. The PDB standard is based on the oxygen isotope ratio of a Cretaceous belemnite from the Peedee formation in South Carolina. Because it was composed of calcite, many limestones have isotopic ratios close to it. Values ("X") reported relative to the two standards are related by equation 3.16. 

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. 

Measurements are made relative to a standard belemnite sample known as FDB — belemnitella americana from the Cretaceous Peedee formation. South Carolina. This standard is used because its and values are close to those of average marine... 

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). 

The carbon of the calcites in Table 17.2 is strongly depleted in C. For example, the calcite of sample 582 has 8 C = -22.6 0.1%o on the PDB scale. On this scale, carbon of marine calcite has 8 C close to 0%o because the PDB standard is a marine belemnite of the Cretaceous Peedee Formation in South Carolina. The evident C depletion of all of the calcite samples from the Elephant Moraine in Table 17.2 is therefore inconsistent with a marine origin of the calcites. 

PDB refers to a standard derived from Belemnitella americana from the Cretaceous Peedee Formation, South Carolina, USA. This standard is exhausted but referred to in the literature, so isotope ratios are measured against other standards and related to PDB as follows ... 

Standards The standard for carbon isotope abundance measurements is based on a Cretaceous belem-nite sample from the Peedee formation in South Carolina, USA. The original material is no longer available. It has been replaced by the convention that NBS 19, a carbonate material, has a value of -i-1.95 l versus PDB. This new scale is termed V-PDB (Vienna-PDB). The IAEA distributes a number of secondary standards including graphite (USGS24) with a d C value of - 15.994 V-PDB, oil (NBS-22) at -29.741 V-PDB, and calcium carbonate (NBS-18) with a value of - 5.014 V-PDB. 

Chemical, carbon-isotopic, and oxygen-isotopic compositions from selected samples of the Latrobe dolomite cement are presented in Table 5(A and B). All of the values in Table 5B fall between —10 and —22%o (PDB, Peedee Formation Belemnite). values of the dolomite cement range from 22.7 to 25.2%o (SMOW, Standard Mean Ocean Water) with an... 

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