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.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/dynamic-marine-calcium-cycle-during-past-28-million-years
[2] http://admin.indiaenvironmentportal.org.in/category/author/elizabeth-m-griffith
[3] http://admin.indiaenvironmentportal.org.in/category/author/adina-paytan
[4] http://admin.indiaenvironmentportal.org.in/category/author/ken-caldeira-et-al
[5] http://admin.indiaenvironmentportal.org.in/category/journal/science
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/oceans-and-seas
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sedimentation
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/carbon-dioxide
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/climate-change
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/climate-science