Silurian

Silurian
Scotese, Christopher R.; Vérard, Christian; Burgener, Landon; Elling, Reece P.; · CC BY 4.0 · source
Name	Silurian
Color	#ffcc99
Time start	443.8
Time end	419.2
Timeline	Paleozoic
Preceding	Ordovician
Following	Devonian

Silurian The Silurian was a geologic period and system of the Paleozoic Era spanning from about 443.8 million to 419.2 million years ago. It followed the Ordovician and preceded the Devonian and is noted for stabilization after the Hirnantian glaciation, widespread reef development, and important early terrestrial colonization. Key scientific studies of the interval involve stratigraphers, paleontologists, and geochemists from institutions such as the British Geological Survey, Smithsonian Institution, and Geological Society of America.

Overview

The Silurian records recovery from the Late Ordovician mass extinction and features global transgressions studied in sections like the Wenlock Series of Wales, the Ludlow Group, and the Niagara Escarpment. Major fossil taxa include trilobites, eurypterids, graptolites, and early jawed vertebrates documented from localities such as Ludlow, Gotland, and the Pentland Hills. Research on Silurian stratotypes has been advanced by workers associated with the International Commission on Stratigraphy and published in outlets like Journal of the Geological Society and Palaeontology (journal).

Stratigraphy and Chronology

Silurian chronostratigraphy is subdivided into epochs and series including the Llandovery, Wenlock, Ludlow, and Pridoli epochs, each defined by biostratigraphic markers such as conodont and graptolite zonations developed by researchers at the University of Cambridge and University of Oxford. Global correlations use isotope chemostratigraphy (δ13C, δ18O) calibrated against magnetostratigraphy and radiometric dates from volcanic ash beds (zircon U-Pb) reported by teams at Uppsala University and the Geological Survey of Canada. Stratigraphic challenges include regional facies changes in basins like the Michigan Basin, Appalachian Basin, and East European Platform.

Paleogeography and Climate

Paleogeographic reconstructions place major landmasses such as Laurentia, Baltica, Siberia, and Gondwana in configurations that influenced ocean circulation and climate, as modeled by groups at NASA and Potsdam Institute for Climate Impact Research. The interval saw warm epeiric seas, episodic cooling, and sea-level changes driven by glacioeustasy linked to polar ice on Gondwana, debated in studies from University of Edinburgh and University of Sydney. Reef complexes formed on continental shelves in regions including Gotland, Estonia, and the British Isles, and paleoenvironmental proxies are preserved in cores from the North Sea and Baltic Sea.

Life and Evolution

Silurian biotas document major evolutionary innovations: vascular plants expanded on land with genera such as Cooksonia and baragwanathia documented by paleobotanists at Royal Botanic Gardens, Kew and Monash University; arthropods including early myriapods and arachnids appear in terrestrial assemblages from Scotland and Wales. Marine ecosystems featured reef builders like tabulate corals and stromatoporoids, nektonic vertebrates including early acanthodians and ostracoderms, and predatory eurypterids exemplified by finds at Pentland Hills and New York. Biogeographic patterns were analyzed by teams at Natural History Museum, London and Field Museum of Natural History using collections that include type specimens described in works by Roderick Murchison and later revised by Charles Lapworth.

Major Geological Events

Significant events include post-extinction biotic recoveries, major transgressive-regressive cycles recorded in the Michigan Basin and Wenlock Limestone, and widespread carbonate platform growth leading to formations like the Niagara Limestone and Hurley Formation. Tectonic activity related to the Caledonian Orogeny and suturing of Laurentia and Baltica produced mountain belts studied in the Scandian phase by geologists from University of Bergen and Trondheim Geological Museum. Volcanism and associated ash beds provided datable horizons used in global correlation by the United States Geological Survey.

Economic and Scientific Significance

Silurian strata host economically important resources including hydrocarbon reservoirs in the Appalachian Basin, North Sea, and Illinois Basin; evaporite and halite deposits exploited in Poland and Germany; and metalliferous mineralization linked to Silurian basinal processes in regions like Wales and Bohemia. Silurian fossils have informed evolutionary theory, paleoclimatology, and basin analysis, underpinning research at centers such as the University of Cambridge, Imperial College London, and Stanford University. Type sections, museum collections at the Natural History Museum, London and Smithsonian Institution, and ongoing field programs by the British Geological Survey and Geological Survey of Canada continue to refine understanding of this interval.

Category:Paleozoic geologic periods