Pridoli

Pridoli is the last stage of the Silurian Period in the international geologic timescale, and it marks the final interval before the Devonian. It follows the Ludlow Stage and is defined by regional to global biostratigraphic correlations rather than a single continuous sequence worldwide. The Pridoli interval is generally placed at roughly 423 to 419 million years ago, though exact boundaries can vary somewhat by region and dating method.

In lithology, Pridoli rocks commonly record continued deposition in shallow seas with a mix of limestone, shale, and sandstone facies, along with reefal and nearshore deposits in suitable paleogeographic settings. The fossil assemblages from Pridoli-age rocks are dominated by marine invertebrates, including brachiopods, bryozoans, corals, mollusks, trilobites, and conodonts, which provide essential biostratigraphic markers for correlations across Gondwana, Baltica, Laurentia, and other landmasses. Terrestrial ecosystems begin to show more evidence of plant and arthropod activity toward the boundary with the Devonian, reflecting early steps in the colonization of land.

Regional correlations are strongest in European sections, where Pridoli strata are well represented, and are extended to other continents through conodont and graptolite zonation and other fossil indicators. The Pridoli interval ends with environmental and faunal changes that pave the way for the Devonian period, including shifts in sea level and climate and broader paleogeographic rearrangements.