This section is from the book "An Introduction To Geology", by William B. Scott. Also available from Amazon: An Introduction to Geology.
The European Devonian appears in three different fades; one of these is the "Old Red Sandstone," which is largely of continental origin, and lies to the north The second facies is of marine, shoal-water deposits and runs from Devonshire, through Belgium, the northern part of the lower Rhenish and the Hartz Mountains, to Poland; and the third, extending from northwestern France, through Germany to Bohemia, was laid down in deeper water. On the other hand, great changes took place in the extent and depth of the Devonian seas, those of the Lower Devonian being far less extensive than those of the Middle and Upper parts of the period, as is also true of North America.
The period began in Europe with an advance of the sea over the land in many places, reaching its maximum extension in the latter part of the period, but beginning to retire before the opening of the Carboniferous. This subsidence removed the barrier which in Ordovician and Silurian times had separated the northern and southern seas, but was accompanied by the formation of closed basins farther to the north. Europe then was largely an open sea with many islands, and where the waters were sufficiently clear and free from terrigenous sediment, coral reefs were extensively formed.
The marine Devonian occurs in the southwest of England, over large areas of Germany, in northwestern and southern France, and on an enormous scale in Russia. During the Silurian the sea had withdrawn almost entirely from Russia west of the Ural Mountains. In the Lower Devonian the sea broke in from the north over Siberia, reaching far into central Asia. In the Middle Devonian a great basin was formed by the depression of central Russia, the sea advancing from the north and the east. Devonian limestones and great coral reefs occur in the Alps, as do limestones, shales, and sandstones of the same period in Spain and Portugal.
The " Old Red Sandstone " is of particular interest, because, owing to the peculiar circumstances of its formation, it has preserved a record of Devonian land life, which, though fragmentary, is far more complete than anything we possess from the more ancient periods. These strata were laid down in closed basins (sometimes, perhaps, in fresh-water lakes), which had only a restricted communication with the sea, and it may be that these accumulations were partly made by the wind, though there is no gypsum or salt in the beds to indicate the prevalence of desert conditions. The Old Red is found in south Wales and the adjoining part of England, and on a much larger scale in Scotland; also in the Baltic provinces of Russia, where it is interstratified with beds of the marine Devonian; in Spitzbergen and Greenland the same formation recurs. These sandstones are said to be 10,000 feet thick, but according to some authorities, the lowermost part of them is Silurian. The Catskill of New York is very like the Old Red, and contains similar fossils, and the Old Red facies is found in northern New Brunswick on Chaleur Bay.
The European Devonian is full of the evidences of volcanic activity, in the shape of great lava-flows and tuffs. In central Scotland the volcanic accumulations exceed 6000 feet in thickness. • Besides the Devonian areas already mentioned in Asia, rocks of this system are found in China, the Altai, and in Asia Minor. They recur in northern Africa. The Bokkeveld beds of South Africa are among the rare marine formations of that region, and these, which are Lower Devonian, thin away northward and die out within a hundred miles of the coast. Below the Bokkeveld, in the upper part of the Table Mountain sandstone, is a boulder clay with striated boulders of evidently glacial origin, pointing to the establishment of rigorous climatic conditions in South Africa in the earliest Devonian, or perhaps late Silurian. In South America occurred a great transgression of the sea, and Devonian strata form larger areas of the surface than those of any other Palaeozoic system. Shallow-water deposits are found in Peru, Bolivia, over large parts of Brazil, especially the basin of the Amazon, and in the Falkland Islands. The Bolivian Devo-. nian, which belongs to the lower and middle parts of the system, contains a very similar fauna to that of North America, and connects the latter with Brazil, the Falkland Islands, and South Africa.
Kayser distinguishes two great marine provinces during the Devonian: (i) the Eurasian, which extended from Europe eastward over northern and central Asia to Manitoba, Canada, and (2) the American, which reached from the United States to South America and thence to South Africa.
With the exception of South Africa, the distribution of Devonian fossils leads us to infer that the climate of the period was, like that of the Ordovician and Silurian, generally uniform over the earth and without distinction of zones.