Abstract: Iodine is a redox sensitive halogen. The oxidized form (iodate) can be incorporated into carbonate structure. I/Ca ratios have been determined in bulk rock and foraminifera tests for long-term records and during abrupt climatic events (e.g. methane "burp"). Applications of this proxy reveal a series of interesting changes throughout the Earth history, ranging from the first appearance of dissolved O₂ in surface ocean, terminal oxygenation of atmosphere-ocean system, to the OMZ dynamics during glacial cycles. This talk will be a tasting menu of these recent investigations.