Sir Roderick Impey Murchison, 1st Baronet, was a Scottish geologist who served as director-general of the British Geological Survey from 1855 until his death in 1871. He is noted for investigating and describing the Silurian, Devonian and Permian systems.
Sir Roderick Murchison
Vanity Fair print of Sir Roderick Murchison
Roderick Impey Murchison posing with cane
Murchison photographed by Camille Silvy in 1860
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago (Mya), to the beginning of the Devonian Period, 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. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out.
Ordovician-Silurian boundary on Hovedøya, Norway, showing brownish late Ordovician mudstone and later dark deep-water Silurian shale. The layers have been overturned by the Caledonian orogeny.
Fossils of the late Silurian sea bed
Silurian sea bed fossils collected from Wren's Nest Nature Reserve, Dudley UK
Crinoid fragments in a Silurian (Pridoli) limestone (Saaremaa, Estonia)