Cherts sentence example
In the extreme north-east are found the oldest rocks in the state - lower Devonian (the New Scotland beds of New York) and, not so old, an extension of the Lower Carboniferous which underlies the Warrior coalfields of Alabama, and which consists of cherts, limestones, sandstones and shales, with a depth of 800 to 900 ft.
Radiolaria are found in cherts in the Culm of Devonshire and Cornwall, in Russia, Germany and elsewhere.
On the east side in North Glen Sannox Burn, they are associated with cherts, grits and dark schists with pillowy lavas, tuffs and agglomerates which, on lithological grounds, have been regarded as probably of the same age as the Arenig cherts and volcanic rocks in the south of Scotland.
Some cherts contain tests of radiolaria, and correspond fairly closely to the siliceous radiolarian oozes which are gathering at the present day at the bottom of some of the deepest parts of the oceans.
Brownish cherts are found in the English Greensand; these often contain remains of sponges.Advertisement
Red and grey cherts, which have not so far yielded undoubted organic remains, occur in this series, and it has in consequence been compared with the Arenig rocks of southern Scotland.
These are overlaid by conglomerates, limestones and clay slates of very doubtful age, the most interesting being a radiolarian clay which occurs on the south side of the Matinang Mountains, at the north end of Lake Posso, &c.; it may correspond with the radiolarian cherts of Borneo.
There was disseminated mineralization within the bedded succession of shales, cherts and tuffs.
In the Kapoewas district radiolarian cherts supposed to be of Jurassic age are met with.