Silurian
Introduction
The Silurian is a geologic period and system that spans 24.6 million years from the end of the Ordovician period, at 443.8 million years ago (mya), to the beginning of the Devonian, 419.2 mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years.
Geology
During the Silurian, the continents were relatively stable, with no significant landmasses moving about. The Earth's climate was also stable, with a warm climate and high sea levels. The Silurian was a time of calcite sea geochemistry, where low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate.
Paleogeography
The Silurian witnessed a relative stabilization of the Earth's general climate, ending the previous pattern of alternating glaciations and greenhouse conditions. The period is marked by the first extensive buildups of coral reefs, and the evolution of a number of important land plants.
Flora and Fauna
The Silurian was a time when the world was recovering from the Ordovician-Silurian extinction events that had wiped out 60% of marine genera. The terrestrial flora was composed of small, simple plants that lacked vascular tissue. The first terrestrial arthropods appeared in the Silurian, represented by mites and early members of the arachnids.
Cultural and Historical Impact
The Silurian was first identified by British geologist Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick, who had named the period of his study the Cambrian, from the Latin name for Wales.