Characteristics of radiometric dating

The basic science behind this method is that calcareous shell material incorporates the two strontium isotopes in the same ratio that occurs in seawater at the time the organism was alive.At different times in Earth's history, the relative abundance of these two isotopes in seawater gradually changed through time (such as during the Permian, the Late Cretaceous, and parts of the Tertiary).A relative age of the original shell can be established by comparing the strontium isotope ratio of the shell material to published data for the time periods where this method is usable.The method is most effective when used in conjunction with other dating methods. Stable Isotope Records - Stable isotope data derived from mineral and biological materials can provide a variety of insights into environmental conditions (past and present), and can be used in geochronology and correlation.

Paleomagnetic dating is based on correlation of measurements derived from oriented samples to established records of variations of the Earth's magnetic field through time.Tradition paleontological and biostratigraphic correlation methods are still perhaps the most common relative dating methods used by geologists.More modern correlation technologies include use of marine stable isotope records, paleomagnetic dating, tephrachronology, geomorphological methods, sedimentation characteristics, and other geochemical and radiometric methods.During periods of glaciation, large volumes of -O become trapped in glacial ice, enriching ocean water in the heavier oxygen isotope.As a result, oxygen isotope data extracted from shell-bearing sediments can provide information about cycles of glaciation (and climate change), and can be used for relative dating.The Sr geochronology method involves extracting these isotopes from fossil shell material (only several milligrams of sample are necessary for X-ray fluorescence spectroscopy).

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