Fossils, dating

Fig. 1.9. Cumulative history of 02 levels through geologic time as recorded by minerals and fossil dating. Most of the oxygen is now present as Fe203 (some 65%). Molecular oxygen in the atmosphere represents 21% in volume (see Fig. 1.12), but only some 4% of the total oxygen on Earth.

The effect of temperature on the rate of racemization of amino acids in fossils was investigated and the implications of the findings on fossil dating were analyzed313. The high rate of conversion of L-aspartic acid into its D-isomer, observed in uncontaminated bone samples taken from catacombs in Rome (IV century BC) was attributed to collagen decomposition due to the humidity of the catacombs314. 

V. R. Meyer, Amino Acid Racemization A Tool for Fossil Dating, Chemtech, July 1992, p. 412. For another application, see T. F. Bidleman and R. L. Falconer, Using Enantiomers to Trace Pesticide Emissions. Environ. 

A molecular clock has been constructed from our 18S rDNA tree and calibrated with fossil dates from the haptophyte coccolithophorid species (Fig. 4). Our molecular clock calculations indicate... 

Fig. 4 Calculation of a molecular clock, (a) The ml tree shown in Edvardsen et al. (2000) has been linearized (Kooistra and Medlin 1996) so that all rates of evolution are the same. Fossil dates from coccolithophore taxa are placed on nodes where these taxa have their first appearance in the fossil record (open circles on tree), (b) A regression of branch lengths against fossil dates has been performed...

We have seen in this work that most of the regional Pleistocene sediments have yielded mammalian fossils originating from the Upper Pleistocene, i.e. the no. II terrace surfaces and the Upper Pleistocene loess. In addition, the upper layers (down to ca. 40-50 m) of the filling material of the Great Hungarian Plain—just like the swamp loess of the Tisza, or its bluish clay —have been found to contain fossils dated to the Lower Wiirm (Janossy and Voros, 1979). 

Estimation of enantiomer ratios is conveniently accomplished using diastereoisomer-forming derivatisation protocols or through separations of enantiomer mixtures over chiral stationary phases. Commercially available chiral coatings for this purpose, such as Chirasil-Val, have been used in the field of amino-acid fossil dating (Section 1.11), exploiting the better resolution of capillary GLC, whereby a thermally stable liquid coats the surface of a narrow tube. 

Hauschka, P.V. (1980) Osteocalcin a specific protein of bone with potential for fossil dating. In Biogeochemistry of Amino Acids, edited by Hare, P.E., Hoering, T.C., King, K. J. New York WUey, pp. 75-82. 

The earliest spruce pollen fossils, dating back to 70 million years before present (b.p.), have been found in North America and elsewhere, according to Morgenstem and Farrar (1964). They noted that fossils resembling modem spmce species, located in Europe, date back to 13 million b.p. These authors stated that black spmce fossil records date back to 1 million b.p. evidence suggests that the species has been in eastern North America for at least 100,000 years. 

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