title: A dynamic marine calcium cycle during the past 28 million years.
abstract: 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 delta44/40Ca 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.
authors.affiliation: Department of Geological and Environmental Sciences, Stanford University, Building 320, Room 118, Stanford, CA 94305, USA. egriffith@ucsc.edu
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Griffith
authors.forename: Adina
authors.initials: A
authors.lastname: Paytan
authors.forename: Ken
authors.initials: K
authors.lastname: Caldeira
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Bullen
authors.forename: Ellen
authors.initials: E
authors.lastname: Thomas
mesh_terms: D000818:Animals; D001466:Barium Sulfate / Q000737:chemistry; D002118:Calcium / Q000032:analysis* / Q000378:metabolism; D002119:Calcium Carbonate / Q000032:analysis; D002127:Calcium Isotopes / Q000032:analysis; D002980:Climate; D019015:Geologic Sediments / Q000737:chemistry; D012623:Seawater / Q000737:chemistry*; D013995:Time
chemical_list: D002127:Calcium Isotopes; D001466:Barium Sulfate; D002119:Calcium Carbonate; D002118:Calcium