Late Ordovician

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 2024.[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 is the third and final epoch of the Ordovician period, lasting 14.6 million years and spanning from around 458.4 to 443.8 million years ago.^[4][5] The rocks associated with this epoch are referred to as the Upper Ordovician Series.

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.

References

1. Wellman, C.H.; Gray, J. (2000). "The microfossil record of early land plants". Phil. Trans. R. Soc. B. 355 (1398): 717–732. doi:10.1098/rstb.2000.0612. PMC 1692785. PMID 10905606.
2. Korochantseva, Ekaterina; Trieloff, Mario; Lorenz, Cyrill; Buykin, Alexey; Ivanova, Marina; Schwarz, Winfried; Hopp, Jens; Jessberger, Elmar (2007). "L-chondrite asteroid breakup tied to Ordovician meteorite shower by multiple isochron 40 Ar- 39 Ar dating". Meteoritics & Planetary Science. 42 (1): 113–130. Bibcode:2007M&PS...42..113K. doi:10.1111/j.1945-5100.2007.tb00221.x.
3. Lindskog, A.; Costa, M. M.; Rasmussen, C.M.Ø.; Connelly, J. N.; Eriksson, M. E. (2017-01-24). "Refined Ordovician timescale reveals no link between asteroid breakup and biodiversification". Nature Communications. 8: 14066. doi:10.1038/ncomms14066. ISSN 2041-1723. PMC 5286199. PMID 28117834. It has been suggested that the Middle Ordovician meteorite bombardment played a crucial role in the Great Ordovician Biodiversification Event, but this study shows that the two phenomena were unrelated
4. "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. December 2024. Retrieved January 2, 2025.
5. Hambrey, M.J. (October 1985). "The late Ordovician—Early Silurian glacial period". Palaeogeography, Palaeoclimatology, Palaeoecology. 51 (1–4): 273–289. doi:10.1016/0031-0182(85)90089-6.
6. Buggisch, Werner; Joachimski, Michael M.; Lehnert, Oliver; Bergström, Stig M.; Repetski, John E.; Webers, Gerald F. (2009). "Did intense volcanism trigger the first Late Ordovician icehouse?". Geology. 38 (4): 327–330. doi:10.1130/G30577.1. ISSN 1943-2682.

External links

• Middle & Late Ordovician Climate
• The World during the Middle and Late Ordovician Archived 2005-03-21 at the Wayback Machine
• The Late Ordovician
• GeoWhen Database - Late Ordovician
• The Ordovician Mass Extinction Archived 2005-07-17 at the Wayback Machine
• BBC Evolution Weekend: Extinction Files