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How often did sea-level cycles occur during the Llandovery Epoch?

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

During the Llandovery Epoch of the Silurian Period, global sea-level cycles occurred with an average duration of approximately 2.5 million years.1

These fluctuations, which involved rising and falling sea levels, have been reconstructed by analyzing biological community replacement patterns across stratigraphic sequences on multiple paleocontinents. Throughout this epoch, at least four distinct global highstands—intervals where sea level rose above the continental shelf edge—have been identified. These events are categorized as follows:1

First highstand: Occurred during the transition between the Rhuddanian and Aeronian Stages.1
Second highstand: Mid-Aeronian in age.1
Third highstand: Early Telychian.1
Fourth highstand: Late Telychian.1

These cycles were likely coordinated by minor changes in the size of the surviving Gondwanan ice cap, and their global nature is supported by evidence of successive glacial episodes in the Brazilian sector of Gondwana.1