Carbon isotopes are a powerful tool for investigating the modern and ancient carbon cycle. There are observed global trends in benthic forams and carbon isotopes that lead us to believe that this system varies globally.
In the Neoproterozoic era carbon isotopes are a critical tool for comparing different sedimentary sections where no radiogenic isotope age constraints or biostratigraphic comparisons are available to correlate different stratigraphic sections. Any sedimentary carbonates older than about 200 million years that are preserved today were deposited in a shallow water environment. Therefore, the presumption that carbon isotope signals represent global changes is very important.
I am trying to test this presumption using Ca isotopes on Tonian carbonate sediments from Ethiopia, where they record -5 or +5 per mil carbon isotopes for long periods of time (~10 Ma).