Hirnantian

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• Hirnantian — The Hirnantian is the seventh and final internationally recognized stage of the Ordovician Period of the Paleozoic Era. It was of short duration, lasting about 1.9 million years, from 445.6 ± 1.5 to 443.7 ± 1.5 Ma (million years ago). The early… …   Wikipedia

• Ordovician — Period 488.3–443.7 million years ago …   Wikipedia

• Anoxic event — As early as 1911, major oceanic currents were well mapped and understood, albeit without today s understanding of how they affect regional and global climatological conditions …   Wikipedia

• Ordovician Period — Interval of geologic time, 490–443 million years ago, the second oldest period of the Paleozoic Era. It follows the Cambrian and precedes the Silurian. During the Ordovician, many of the landmasses were aligned in the tropics. Life was dominated… …   Universalium

• Geologic time scale — This clock representation shows some of the major units of geological time and definitive events of Earth history. The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga.[1] Other… …   Wikipedia

• Paleozoic — era 542   251 million years ago Key events in the Paleozoic view • edit …   Wikipedia

• Ordovician–Silurian extinction event — …   Wikipedia

• Geology of the North Sea — Contents 1 Tectonic structure 2 Precambrian 3 Finnmarkian, Athollian, Caledonian Orogenies …   Wikipedia

• Cambrian — For other uses, see Cambrian (disambiguation). Cambrian Period 542–488.3 million years ago …   Wikipedia

• Carboniferous — For the album by Zu see Carboniferous (album). Carboniferous Period 359.2–299 million years ago …   Wikipedia

• Cretaceous — Period 145.5–65.5 million years ago …   Wikipedia