The secular evolution of the Permian seawater ⁸⁷Sr/⁸⁶Sr ratios carries information about global tectonic processes, palaeoclimate and palaeoenvironments, such as occurred during the Early Permian deglaciation, the formation of Pangaea and the Permian–Triassic (P–Tr) mass extinction. Besides this application for discovering geological aspects of Earth history, the marine ⁸⁷Sr/⁸⁶Sr curve can also be used for robust correlations when other bio-, litho- and/or chemostratigraphic markers are inadequate. The accuracy of marine ⁸⁷Sr/⁸⁶Sr reconstructions, however, depends on high-quality age control of the reference data, and on sample preservation, both of which generally deteriorate with the age of the studied interval. The first-order Permian seawater ⁸⁷Sr/⁸⁶Sr trend shows a monotonous decline from approximately 0.7080 in the earliest Permian (Asselian) to approximately 0.7069 in the latest Guadalupian (Capitanian), followed by a steepening increase from the latest Guadalupian towards the P–Tr boundary (c. 0.7071–0.7072) and into the Early Triassic. Various higher-order changes in slope of the Permian ⁸⁷Sr/⁸⁶Sr curve are indicated, but cannot currently be verified owing to a lack of sample coverage and significant disagreement of published ⁸⁷Sr/⁸⁶Sr records.

Supplementary material: Numbers, information, data and references of the samples discussed are available at https://doi.org/10.6084/m9.figshare.c.3589460