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new age of this standard of 28.201 ± 0.046 Ma is remarkably more precise than the
previously adopted value of 28.02 ± 0.56 Ma).
Productive interplay between astronomical dating and the improved accuracy
of the
40
Ar/
39
Ar and U/Pb chronometers is likely to continue in the coming years.
Such interplay is nicely illustrated by work on the Cretaceous-Tertiary (K-T)
boundary (Kuiper et al., 2008). While excellent cyclostratigraphy is apparent in some
K-T boundary sections (see Figure 2.27), there is ambiguity in precisely how to map
the sedimentary signals to the independently computed astronomical forcings.
Improved dating accuracy has provided a new, high-accuracy-age tie point at the K-T
boundary. This new tie point provides a new and more robust (but not yet definitive)
age anchor on which to pin the astronomical timescale.
Figure 2.27
Milankaovitch cycles at the Zumaya K-T boundary section,
Spain. High-precision radiometric dates permit improved assignment of the
absolute ages of these cycles and hence a more accurate geological timescale.
SOURCE: Kuiper et al. (2008). Reprinted with permission from AAAS.
Geochronology has its roots in analytical geochemistry and has greatly
benefited from improvements in instrumentation and in a refined understanding of the
underlying geochemical principles. Geochronology is a vibrant research
subdiscipline, and the next decade will likely see continued advances in this area.
However, as the fidelity, availability, and diversity of dating methods expand, the
need for close collaboration among those who develop techniques and make the
measurements with those who select key samples and interpret results is becoming
increasingly apparent. In many cases—for example, in surface exposure dating and
thermochronometry—sophisticated models are essential to extract the full meaning
from the data. Thus, continued and robust advances in geochronology will involve a
broad cross section of the Earth science community.
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