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Updated: May 25, 2025
Such joints, therefore, must often have resulted from one of the last changes superinduced upon sedimentary deposits. S-S are the lines of stratification; D, D are lines of slaty cleavage, which intersect the rock at a considerable angle to the planes of stratification. In the Swiss and Savoy Alps, as Mr.
Succession implies time; the lower members of a series of sedimentary rocks are certainly older than the upper; and when the notion of age was once introduced as the equivalent of succession, it was no wonder that correspondence in succession came to be looked upon as a correspondence in age, or "contemporaneity."
In these formations, as well as in many true sedimentary deposits, it is evident that iron tends to become aggregated, either in the form of a shell, or of a network. The origin of these superficial beds, though sufficiently obscure, seems to be due to alluvial action on detritus abounding with iron.
On the causes of the absence of recent conchiferous deposits on the coast of S. America. On the contemporaneous deposition and preservation of sedimentary formations. I can add little to the details given by M. d'Orbigny on the sandstone formation of this district.
Twelfthly: a bed of compact, sonorous, feldspathic lava, like that of bed No. 8, divided by numerous joints into large angular blocks. Thirteenthly: sedimentary beds as before.
Considering the perishable nature of many of the lower organic forms, the metamorphosis of numerous sedimentary strata, and the great gaps occurring among the rest, we shall see further reason for distrusting our deductions.
And seeing, from the laminated structure of many formations and the organic remains contained in others, that they were sedimentary; he further inferred that these universal strata had been in succession precipitated from a chaotic menstruum which once covered our planet.
The shore lines of extinct lakes, such as Lake Agassiz and Lakes Bonneville and Lahontan, may be traced by the heavy deposits at the mouths of their tributary streams. We have seen that the work of streams is to drain the lands of the water poured upon them by the rainfall, to wear them down, and to carry their waste away to the sea, there to be rebuilt by other agents into sedimentary rocks.
Petroleum and natural gas, wherever found, have probably originated from the decay of organic matter when buried in sedimentary deposits, just as at present in swampy places the hydrogen and carbon of decaying vegetation combine to form marsh gas.
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.
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