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Why do scientists disagree about how long the Permian extinction lasted?

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Line graph showing the number of marine animal families from the Precambrian era to the present, with illustrations of key groups such as trilobites, ammonoids, marine reptiles, and diatoms. The graph highlights major extinction events and a rise to 1,900 living families today. — Permian extinction The diversity of marine animal families since late Precambrian time. The data for the curve comprise only those families that are reliably preserved in the fossil record; the 1,900 value for living families also includes those families rarely preserved as fossils. The several pronounced dips in the curve correspond to major mass-extinction events. The most catastrophic extinction took place at the end of the Permian Period.

Scientists disagree on the duration of the Permian extinction because of differing interpretations of the geological and paleontological record regarding the timing of these extinction pulses.12

The debate centers on two primary perspectives:

Extended duration: Many geologists and paleontologists argue that the extinction events occurred over approximately 15 million years, spanning the final stage of the Middle Permian Epoch and throughout the Late Permian Epoch, with each successive event appearing more severe than the last.12
Rapid duration: Other scientists contend that the extinction interval was much more compressed, lasting only about 200,000 years. This group suggests that the majority of species loss occurred within a concentrated 20,000-year span near the end of the Permian Period.12

This uncertainty is compounded by complex factors such as shifts in the carbon cycle and temperature crises, which suggest that multiple environmental stressors contributed to the loss of approximately 90 percent of Earth's species.341