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Why can absolute dates for Triassic events change as scientists make new measurements?

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Triassic paleogeography — Triassic Period Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the early Triassic Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.

Absolute dates for events during the Triassic Period are subject to change as scientific techniques evolve and new measurements are obtained. Because the Triassic System is primarily composed of sedimentary rocks, which generally do not provide reliable radiometric data, researchers have historically relied on relative dating methods like biochronology to establish chronologies.1

When absolute dating is possible, it relies on the measurement of radioactive isotopes and their decay products. As analytical technology advances—such as the development of mass spectrometry, isotope dilution, and high-resolution microprobes like SHRIMP—scientists can analyze smaller samples with significantly higher precision and lower contamination levels. These technical improvements allow for more accurate calibration of isotopic tracers and better assessment of background interference. Consequently, as measurement errors are reduced and analytical sensitivity increases, previously established numerical ages are often refined or updated to reflect more precise data.234