In the geologic timescale , the Rhuddanian is the first age of the Silurian Period and of the Llandovery Epoch. The Silurian is in the Paleozoic Era of the Phanerozoic Eon . The Rhuddanian Age began 443.8 ± 1.5 Ma and ended 440.8 ± 1.2 Ma (million years ago). It succeeds the Hirnantian Age (the last age of the Ordovician Period) and precedes the Aeronian Age.
2-448: The Llallagua Formation is a Rhuddanian to Homerian geologic formation of western Bolivia. The formation comprises siliciclastic sediments. The fossil fauna suggests a warm water, nearshore current was active allowing northern hemisphere benthos to exist in the formation. The formation has provided the following fossils: Rhuddanian The GSSP for the Silurian is located in
4-657: A section at Dob's Linn , Scotland, in an artificial excavation created just north of the Linn Branch Stream. Two lithological units ( formations ) occur near the boundary. The lower is the Hartfell Shale (48 metres (157 ft) thick), consisting chiefly of pale gray mudstone with subordinate black shales and several interbedded meta-bentonites. Above this is the 43 metres (141 ft) thick Birkhill Shale , which consist predominantly of black graptolitic shale with subordinate gray mudstones and meta-bentonites. The name
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