Britannica Sources used in this answer

What are tempestites in Ordovician rocks?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

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

In the context of the Ordovician Period, tempestites are sedimentary deposits formed by storm-driven processes. These deposits are common in Ordovician strata, particularly within sedimentary beds on continental shelves where they occur alongside shale, sandstone, or limestone.1

These structures are created by the combination of large waves and strong currents associated with tropical cyclones. Characteristic features of these beds include evidence of erosion at their bases and a tendency to become finer-grained toward the top of the bed. Because the seafloor can be eroded during the early phases of a storm, the preservation of these layers provides a record of storm frequency; for example, an interval of Late Ordovician rock near Cincinnati, Ohio, contains over 300 tempestites, suggesting that storms left a preserved sedimentary record at least once every 5,000 years during that time.1