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The cause for the end of the Late Ordovician Glaciation is a matter of intense research, but evidence shows that the deglaciation in the terminal Hirnantian may have occurred abruptly, as Silurian strata marks a significant change from the glacial deposits left during the Late Ordovician. [66]
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 ...
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] The southward shift of the polar front severely contracted the available latitudinal range of warm-adapted organisms. [63]
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 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] The sea level rose more or less continuously throughout the Early Ordovician, leveling off somewhat during the middle of the period. [41]
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;
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]
In the geological timescale, the Llandovery Epoch (from 443.8 ± 1.5 million years ago to 433.4 ± 0.8 million years ago) occurred at the beginning of the Silurian Period. . The Llandoverian Epoch follows the massive Ordovician-Silurian extinction events, which led to a large decrease in biodiversity and an opening up of ecosyste