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The Hirnantian glaciation, also known as the Andean-Saharan glaciation, Early Paleozoic Ice Age (EPIA), [1] the Early Paleozoic Icehouse, [2] the Late Ordovician glaciation, or the end-Ordovician glaciation, occurred during the Paleozoic from approximately 460 Ma to around 420 Ma, during the Late Ordovician and the Silurian period.
Two environmental changes associated with the glaciation were responsible for much of the Late Ordovician extinction. First, the cooling global climate was probably especially detrimental because the biota were adapted to an intense greenhouse, especially because most shallow sea habitats in the Ordovician were located in the tropics. [62]
On the other hand, global cooling has also been offered as a cause of the radiation, [11] [16] [17] with long-term biodiversity trends showing a positive correlation between cooling and biodiversity during GOBE. [18] [7] An uptick in fossil diversity correlates with the increasing abundance of cool-water carbonates over the course of this time ...
In fact, the Hirnantian (also known as the End Ordovician and the Ordovician-Silurian) mass extinction event represents the second largest such event in geologic history. Approximately 85% of marine (sea-dwelling) species died. Only the End-Permian mass extinction was larger. Unlike many smaller extinction events, however, the long-term ...
Further cooling during the Hirnantian, at the end of the Ordovician, led to the Late Ordovician glaciation. [52] The Ordovician saw the highest sea levels of the Paleozoic, and the low relief of the continents led to many shelf deposits being formed under hundreds of metres of water. [41]
A "greenhouse Earth" is a period during which no continental glaciers exist anywhere on the planet. [6] Additionally, the levels of carbon dioxide and other greenhouse gases (such as water vapor and methane) are high, and sea surface temperatures (SSTs) range from 28 °C (82.4 °F) in the tropics to 0 °C (32 °F) in the polar regions. [7]
The plant shows a high degree of development in relation to the age of its fossil remains. Fossils of this plant have been recorded in Australia, [39] [40] Canada, [41] and China. [42] Eohostimella heathana is an early, probably terrestrial, "plant" known from compression fossils [43] of Early Silurian (Llandovery) age. [44]
Pages in category "Ordovician plants" The following 6 pages are in this category, out of 6 total. This list may not reflect recent changes. C. Casterlorum; Chaetocladus;