ABSTRACT
A variety of techniques are available for tracking the history of carbon dioxide through the ages. Carbon dioxide, photosynthetically incorporated as carbon into living marine microorganisms, contributes to a steady shower of organic matter down to great depths. Very precise determinations of slight changes in the abundance of measured isotope fractions are what enable researchers, starting with Urey and his group, to take advantage of the history record in layered depositories. The practical use of the minor variations associated with different isotopes in chemical systems was first recognized by the American chemist Harold Urey in the 1940s. Urey was the first to explain the basis of chemical isotope effects. The heavier the isotopes involved in a bond, the slower, more sluggish, is that vibration. The ostensible disagreement is quite understandable because fresh water originates via rain or snow, mostly from water vapor that has evaporated from the sea.
