Chromium isotope fractionation between modern seawater and biogenic carbonates from the Great Barrier Reef, Australia: Implications for the paleo-seawater δ 53 Cr reconstruction

•Cr isotopes in a seawater-carbonate system from the Great Barrier Reef, Australia.•Systematically lower δ53Cr in marine biogenic carbonates relative to ocean waters.•Coupling between δ53Cr and Ce/Ce* data in carbonates from Lady Elliot Island.•Evidence for redox-controlled incorporation of Cr into marine biogenic carbonates.•Implications for paleo-seawater δ53Cr reconstruction based on multi-proxy approach.