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Potassium:Absolute Chronologies Calibrated Using Really Accurate TIMS Experiments

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Increasing accuracy of geological dating

An EU-funded project improved the estimate accuracy of the time of geological events.

Climate Change and Environment

Knowledge of detailed ages and durations of events, and therefore rates of processes, are fundamental to Earth sciences. Compared to other geochronological methods, the argon–argon dating technique can determine the age of potassium-rich rocks as far back as when the Earth was formed. Nevertheless, the technique has systematic errors that produce dates with uncertainties of about 2.5 %. Research conducted by the EU-funded project 'Potassium:Absolute chronologies calibrated using really accurate TIMS experiments' (K:ACCURATE) helped increase the accuracy of estimates by correcting measurements of argon made in the 1960s and the 1970s. Scientists developed an isotopic standard for measuring absolute abundances of potassium-40 that are traceable to the International System of Units. They also measured the absolute amount of potassium-40 in mineral standards. A new method was developed in a bid to determine potassium isotopic composition in natural materials. This enabled scientists to identify, for the first time, changes in potassium concentration attributed to natural variability. As such, recalculating the partial decay constant was not possible, since the material used in the past measurements was not known. This variability is expected to shed further light on topics in fields as diverse as pegmatite formation, subduction zone processes, seawater salinity and the potassium atomic weight. By lowering uncertainty to 0.5 %, argon–argon dating is now able to provide more precise absolute dates for many geologic events. As such, K:ACCURATE also dated with unprecedented precision the Cretaceous–Tertiary boundary.

Keywords

Geological dating, geological events, Earth sciences, geochronological, argon–argon dating, potassium, TIMS experiments, potassium-40, natural materials, potassium concentration, natural variability, Cretaceous–Tertiary boundary

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