EAGER: Towards a High Resolution Record of Phanerozoic Ocean Chemistry: Links to Plate Tectonics and Climate

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Towards a High Resolution Record of Phanerozoic Ocean Chemistry: Links to Plate Tectonics and ClimateTroy Rasbury, SUNY StonybrookEAR-1028663ABSTRACTThe oceans are the heart of our planet and are the primary feature that makes Earth different from other planets we have found. Much of the difficulty in constraining models for interlinking of the Earth systems comes from the paucity of reliable archives of past seawater chemistry. PI has chosen to focus on the relationship between Sr and Mg in marine invertebrate fossils to study changes in paleo-seawater. Seawater chemistry is thought to result from the mixing of hydrothermal fluids from ridge spreading centers and continental fluxes as sources, and the sinks of various elements such as in new mineral formation or sorption on existing mineral surfaces. Some geochemical models for seawater have used changes in sea level and volcanism to imply changes in the spreading rates of ocean ridges and their corresponding flux. These models closely predict the changes measured in the marine proxy record. However, other scientists maintain there is no evidence that spreading rates have changed since the Jurassic. These scientists do not address seawater chemistry constraints, and therefore their interpretation requires that another mechanism be sought to produce the observed relationships between sealevel, climate, and seawater chemistry. Another point of conflict with the geochemical record of seawater is the behavior of Sr. While studies based on Sr concentrations in low Mg fossils shells show that Sr behaves inversely to Mg in seawater, a recent Science paper argues that Sr behaves the same Mg in seawater. They suggest that the difference may be a poor understanding of the Kd for Sr in biogenic carbonates. However this would only impact the magnitude of calculated changes, not cause an inverse relationship. PIs research goal is to produce a high resolution record of Mg and Sr from marine fossils to address the issue of how seawater chemistry ties to known tectonic events and climate change in the Cenozoic- and by doing so to perhaps address the overarching question of what causes changes in rates of plate tectonics and how this links to global climate change.