Some examples of 13C and O18 data. The most abundant isotope of carbon is 12C. Because it is lighter than 13C, its utilization is favored during photosynthesis, and even more so during chemosynthesis.
Fractionation also occurs during inorganic equilibrium reactions and phase changes.
The most abundant isotope of oxygen is 16O. Fractionation during phase changes is the greatest influence on 18O in seawater, because the reservoir is so large. The vapor pressure of water composed of 16O is greater than 18O and is temperature dependent. At low temperatures, water vapor will be very depleted in 18O, and the residual liquid will be enriched in 18O. Paleoclimate studies have employed this relationship as the carbonate shells record paleotemperature in their isotopic composition. References Return to Authigenic Carbonates from the Monterey Canyon. Or check out the Long Term Deep Sea Observatories Project or maps and video of the Soquel Canyon or Monterey Meander or return to Debra's homepage .