Late Ordovician

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Late Ordovician" – news · newspapers · books · scholar · JSTOR (January 2024) (Learn how and when to remove this message)

Late/Upper Ordovician
458.4 ± 0.9 – 443.8 ± 1.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N
A map of Earth as it appeared 450 million years ago during the Late Ordovician Epoch, Katian Age
Chronology
−485 — – −480 — – −475 — – −470 — – −465 — – −460 — – −455 — – −450 — – −445 — – P a l e o z o i c Ꞓ O r d o v i c i a n S Furongian E a r l y M i d d l e L a t e Llandovery Tremadocian Floian Dapingian Darriwilian Sandbian Katian Hirnantian       ← First land plant spores[1] ← Ordovician meteor event[2][3] Subdivision of the Ordovician according to the ICS, as of 2023.[4] Vertical axis scale: Millions of years ago
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Epoch
Stratigraphic unit	Series
Time span formality	Formal

The Late Ordovician, also called the Upper Ordovician by geologists, is the third and final epoch of the Ordovician period.^[5]

At this time, Western and Central Europe and North America collided to form Laurentia, while glaciers built up in Gondwana, which was positioned over the South Pole. This caused a drop in global temperatures, resulting in "ice house" conditions.^[6]

For most of this time, life continued to flourish, but at and near the end of the period, there were mass-extinction events that seriously affected planktonic forms like conodonts, graptolites, and some groups of trilobites (Agnostida and Pytchopariida, which completely died out, and the Asaphida which were much reduced). Brachiopods, bryozoans and echinoderms were also heavily affected, and the endocerid cephalopods died out completely, except for possible rare Silurian forms. The Ordovician-Silurian Extinction Events may have been caused by an ice age that occurred at the end of the Ordovician period as the end of the Late Ordovician was one of the coldest times in the last 600 million years of Earth history.