A Dynamic Marine Calcium Cycle During the Past 28 Million Years
Elizabeth M. Griffith, Adina Paytan, Ken Caldeira, Thomas D. Bullen & Ellen Thomas
Climatic changes over the past 28 million years has affected the isotopic ratio of calcium in the Earth's oceans. Here we try to understand what calcium isotopes can tell us about Earth's climate evolution.
Multiple lines of evidence have shown that the isotopic composition and concentration of calcium in seawater have changed over the past 28 million years. A high-resolution, continuous seawater calcium isotope ratio curve from marine (pelagic) barite reveals distinct features in the evolution of the seawater calcium isotopic ratio suggesting changes in seawater calcium concentrations. The most pronounced increase in the δ44/40 Ca value of seawater (of 0.3 per mil) occurred over roughly 4 million years following a period of low values around 13 million years ago. The major change in marine calcium corresponds to a climatic transition and global change in the carbon cycle and suggests a reorganization of the global biogeochemical system.