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Some of the Upper Ludlow sandstones are ripple-marked, thus affording evidence of gradual deposition; and the same may be said of the accompanying fine argillaceous shales, which are of great thickness, and have been provincially named "mud-stones."
The rocks are of many kinds, white laminated, sometimes siliceous sandstone, purple and red sandstone, sometimes so highly calcareous as to have a crystalline fracture, argillaceous limestone, black calcareous slate-rock, like that so often described at Copiapo and other places, thinly laminated, fine-grained, greenish, indurated, sedimentary, fusible rocks, approaching in character to the so- called pseudo-honestone of Chile, including thin contemporaneous veins of gypsum, and lastly, much calcareous, laminated porcelain jasper, of a green colour, with red spots, and of extremely easy fusibility: I noticed one conformable stratum of a freckled-brown, feldspathic lava.
One general character of all argillaceous rocks is to give out a peculiar, earthy odour when breathed upon, which is a test of the presence of alumine, although it does not belong to pure alumine, but, apparently, to the combination of that substance with oxide of iron. This division comprehends those rocks which, like chalk, are composed chiefly of lime and carbonic acid.
I have already hinted at the close analogy in the forms of certain granitic and trappean veins; and it will be found that strata penetrated by Plutonic rocks have suffered changes very similar to those exhibited near the contact of volcanic dikes. Thus, in Glen Tilt, in Scotland, alternating strata of limestone and argillaceous schist come in contact with a mass of granite.
The stumps still remain in their original position; but the numerous articulations, once composing the stem, arms, and body of the encrinite, were scattered at random through the argillaceous deposit in which some now lie prostrate.
A few gaunt willows creep timorously down its sandy sides; at the very bottom, which is dry and yellow as copper, lie huge slabs of argillaceous rock. A cheerless position, there's no denying, yet all the surrounding inhabitants know the road to Kolotovka well; they go there often, and are always glad to go.
Such carbonic acid, meeting with the protoxide of iron in solution, would unite with it and form a carbonate of iron; and this mingling with fine mud, when the excess of carbonic acid was removed, might form beds or nodules of argillaceous ironstone. Natural size and magnified. b. Natural size and magnified. Goniatites Listeri, Martin. Aviculopecten papyraceus, Goldf.
The peculiar aspect which is most characteristic of the Lias in England, France, and Germany, is an alternation of thin beds of blue or grey limestone, having a surface which becomes light-brown when weathered, these beds being separated by dark-coloured, narrow argillaceous partings, so that the quarries of this rock, at a distance, assume a striped and ribbon-like appearance.
Its waters are very sweet, and abound with delicious fish in great variety. The fertility of the northern end of the lake surpassed anything we had hitherto seen; but this was not surprising when duly considered. The hills, instead of being, as on the great plateau we had recently left, outcrops of granite, were composed of argillaceous sandstone.
Hillocks, formed of the hardest and purest varieties of the white gypsum, stand up above the surrounding parts, and have their surfaces cracked and marked, just like newly baked bread. There is much pale brown, soft argillaceous gypsum; and there were some intercalated green beds which I had not time to reach.
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