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Updated: May 21, 2025
Fe Bajada, as may be inferred from the vegetable debris, from the quantities of silicified wood, and from the remains of a Toxodon found, according to M. d'Orbigny, in still lower strata, we may conclude, that at this ancient period a great expanse of water was surrounded by the same rocky framework which now bounds the plains of Pampean formation.
From Level of Sea to Surface of plain, 252 feet above sea, through levels F, E, D and C: F. Lower sandstone, with concretions and silicified bones, with fossil shells, all, or nearly all, extinct. E. Upper ferruginous sandstone, with numerous Balani, with fossil shells, all, or nearly all, extinct. C and D. Calcareous beds with recent shells.
Near Weymouth there is a piece of this stratum, in which stumps of trees remain rooted, mostly erect or slightly inclined, and from one to three feet high; while trunks of the same forest, also silicified, lie imbedded on the surface of the soil in which they grew.
Many silicified trunks of coniferous trees, and the remains of plants allied to Zamia and Cycas, are buried in this dirt-bed, and must have become fossil on the spots where they grew.
In some of the jaspery layers, and in some of the black siliceous slaty bands, there were irregular seams of imperfect pitchstone, undoubtedly of metamorphic origin, and other seams of brown, crystalline limestone. Here, also, were masses, externally resembling ill-preserved silicified wood. Fourthly and fifthly: calcareous pseudo-honestone; and a thick stratum concealed by detritus.
These are plants growing in sea or fresh water, or on damp surfaces, with a filamentous, or more rarely a leaf-like pulverulent or gelatinous thallus; the last two forms essentially microscopic. Consisting frequently of definitely arranged groups of distinct cells, either of ordinary structure or with their membrane silicified Diatomaceae. We note three forms of fructification: 1.
The layer of coal in contact with the carbonized or silicified part of the specimens is due, then, to a compression of the organic elements already chemically carbonized, but in which the mineral matter was not yet hardened and was able to escape. Arthropitus gallica, St. If this be so, we ought to find the remains of organic structure in this region c.
A few miles north of Coquimbo, I met with the ferruginous, balaniferous mass E with many silicified bones; I was informed that these silicified bones occur also at Tonguay, south of Coquimbo: their number is certainly remarkable, and they seem to take the place of the silicified wood, so common on the coast-formations of Southern Chile.
At the bottom we found a forest of large silicified trees, all lying as if the elevation of the range had made them fall away from it, and toward the river. An ordinary-sized tree standing on end, measured 22 inches in diameter: there were 12 laminae to the inch.
The various Porphyries, and Diorites, and Granitic, and Sienitic rocks, which characterize large districts along the eastern coast of Australia, were missing; not a pebble, except of sandstone, was found in the numerous creeks and watercourses. Pieces of silicified wood were frequent in the bed of the Isaacs.
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