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Updated: June 21, 2025
From these considerations it follows that the perfect identity of very ancient and very modern volcanic formations is scarcely possible. Superposition, therefore, is not of the same value as a test of age in the unstratified volcanic rocks as in fossiliferous formations. We can only rely implicitly on this test where the volcanic rocks are contemporaneous, not where they are intrusive.
R. Bald has recorded the circumstances under which a single elephant's tusk was found in the unstratified drift of the valley of the Forth, with the minuteness which such a discovery from its rarity well deserved. This cover he says is sometimes 160 feet thick.
A second unstratified mass of yellow and more sandy clay 40 feet thick, with pebbles and angular polished and striated blocks of granite and other Scandinavian rocks, transported from a distance. Number 5. Stratified sands and gravel, with occasionally large erratic blocks; the whole mass varying from 40 to 100 feet in thickness, but this only in a few spots.
The argillaceous, or clay rocks, including muds, clays, and shales. These three classes pass by mixture into one another. Thus there are limy and clayey sandstones, sandy and clayey limestones, and sandy and limy shales. GRANITE. This familiar rock may be studied as an example of the second great group of rocks, the unstratified, or igneous rocks.
The deposit c in that section consists of sand, mud, gravel, and stones, for the most part unstratified, resembling the till or boulder clay of Europe. It varies in thickness from 10 to 50 feet, being of greater depth in the valleys. The uppermost portion is occasionally, though rarely, stratified. Some few of the imbedded stones have flattened, polished, striated, and furrowed sides.
There was not a bush six inches high, and the only approach to woody plants were minute creeping willows and dwarf rhododendrons, with a very few prostrate junipers and Ephedra. The base of the spur was cut into broad flat terraces, composed of unstratified sand, pebbles, and boulders; the remains, doubtless, of an enormously thick glacial deposit.
Calcareous loam, buff-coloured, resembling loess, for the most part unstratified, in some places with slight traces of stratification, containing freshwater and land shells, with bones of elephants, etc.; thickness about 15 feet. 3.
Professor Ramsay estimates the thickness of the Bala Beds, including the contemporaneous volcanic rocks, stratified and unstratified, as being from 10,000 to 12,000 feet. The Lower Silurian strata were originally divided by Sir R. Murchison into the upper group already described, under the name of Caradoc Sandstone, and a lower one, called, from a town in Carmarthenshire, the Llandeilo flags.
Brown loam with some angular flints, in parts passing into ochreous gravel, filling up indentations on the surface of Number 3, 3 feet thick. 3. White siliceous sand with layers of chalky marl, and included fragments of Chalk, for the most part unstratified, 9 feet. 4.
This idea was adopted in the infancy of the science, when all formations, whether stratified or unstratified, earthy or crystalline, with or without fossils, were alike regarded as of aqueous origin.
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