In Scotland the upper and middle series are represented by a thick mass of limestone and dolomite, the Durness limestone (1500 ft.). In the lower series are, in descending order, the “Serpulite grits” or “Salterella beds,” the “Fucoid beds” and the “Eriboll quartzite,” which is divided into an upper “Pipe rock” and lower “Basal quartzite.”
The Cambrian rocks of Ireland, a great series of purple and green shales, slates and grits with beds of quartzite, have not yet yielded sufficient fossil evidence to permit of a correlation with the Welsh rocks, and possibly some parts of the series may be transferred in the future to the overlying Ordovician.
North America.—On the North American continent, as in Europe, the Cambrian system is divisible into three series: (1) the lower or “Georgian,” with Olenellus fauna; (2) the middle or “Acadian,” with Paradoxides or Dikelocephalus fauna; (3) the upper or “Potsdam,” with Olenus fauna (with Saratogan or St Croix as synonyms for Potsdam). The lower division appears on the Newfoundland and Labrador coasts, and is traceable thence, in a great belt south-west of those points, through Maine and the Hudson-Champlain valley into Alabama, a distance of some 2000 m.; and the rocks are brought up again on the western uplift, in Nevada, Idaho, Utah, western Montana and British Columbia. The middle division covers approximately the same region as the lower one, and in addition it is found in the states of Texas, Oklahoma, and Arizona, in western Montana, and possibly in western Wisconsin. The lower division, in addition to covering the areas already indicated, spreads over the interior of the United States.
Bohemia.—The Cambrian rocks of this country are now recognized by J.F. Pompesk; to comprise the Paradoxidian and Olenelledian groups. They were made famous through the researches of Barrande. The Cambrian system is covered by his stages “B” and “C”; the former a barren series of conglomerates and quartzites, the latter a series of grey and green fissile shales 1200 ft. thick with sandstones, greywackes and conglomerates.
| North Wales. | South Wales. | Midland and West of England. | |||
| Shropshire. | Malvern Hills. | Nuneaton. | |||
| Upper Cambrian, Olenus fauna | Tremadoc slates (Euloma-Niobe fauna) | Tremadoc beds | Shineton shales and shales with Dictyonema | Bronsil shales, gray (Niobe fauna) | Upper Stockingford shale (Merivaleshales) |
| Lingula flags | Lingula flags | Malvern black shales (White-leaved-oak shales) | |||
| (1) Dolgelly beds | |||||
| (2) Ffestinieg beds | Middle Stockingford shales (Oldbury shales) | ||||
| (3) Maentwrog beds | |||||
| Middle Cambrian Paradoxides fauna | Menevian beds | Menevian beds | |||
| Solva group | Comley or Hollybush sandstone with upper Comley limestone | Hollybush sandstone | Lower Stockingford shales (Purley shales) | ||
| Lower Cambrian Olenellus fauna | Harlech grits and Llanberis slates | Caerfai group | Lower Comley limestone | Hollybush sandstone with Malvern quarzite and conglomerate at the base | Upper Hartshill quarzite Hyolithes Hyolithes shales and limestone |
| Wrekin quartzite | Middle and lower Hartshill quarzite and the quarzite of the Lickey Hills | ||||
Scandinavia.—Here the Cambrian system is only distinguished clearly on the eastern side, where the three subdivisions are found in a thin series of strata (400 ft.), in which black concretion-bearing shales play an important part. Limestones and shales with the Euloma-Niobe fauna come at the top. The upper series (Olenus) has been minutely zoned by W.C. Brögger, S.A. Tullberg and J.C. Moberg. In the middle series (Paradoxides) three thin limestone bands have been distinguished, the Fragmenten-Kalk, the Exulans-Kalk and the Andrarums-Kalk.
On the Norwegian side the Cambrian is perhaps represented by the Röros schists which lie at the base of a great series of crystalline schists, the probable equivalent of Ordovician and Silurian rocks.
Baltic Province.—The Cambrian rocks in this region are nearly all soft sediments, some 600 ft. thick; they reach from the Gulf of Finland towards Lake Ladoga. At the base is the so-called “blue clay” (really greenish) with ferruginous sandstones and with a fucoidal sandstone at its summit. This division is the equivalent of the Lower Cambrian. Above the fucoidal sandstone an important break appears in the system, for the Paradoxides and Olenus divisions are absent. The upper members are the “Ungulite grit” and about 20 ft. of Dictyonema shale. Cambrian rocks have been traced into Siberia (lat. 71°) and on the island of Vaigatch.
Central Europe.—Besides the Bohemian region previously mentioned, Cambrian rocks are present in Belgium and the north of France, in Spain and the Thüringer Wald. In the Ardennes the system is represented by grits and sandstones, shales, slates and quartz schists, and includes also whet slates and some igneous rocks. A. Dumont has arranged the whole series (Terrain ardennais) into three systems, an upper “Salmien,” a middle “Revinien” and a lower “Devillien,” but J. Gosselet has subsequently proposed to unite the two lower groups in one.
France.—-In northern France Cambrian rocks, mostly purple conglomerates and red shales, rest with apparent unconformability upon pre-Cambrian strata in Brittany, Normandy and northern Poitou. In the Rennes basin limestones—often dolomitic—are associated with quartzites and conglomerates; silicious limestones also occur in the Sarthe region. Farther south, around the old lands of Languedoc, equivalents of the two upper divisions of the Cambrian have been recorded; and the uppermost members of the system appear in Herault. Patches of Cambrian rocks are found in the Pyrenees.