Geological Observations on South AmericaDarwin, Charles
Science
Geological Observations on South America
Darwin, Charles
Beagle Expedition (1831-1836); Geology -- South America; Mollusks, Fossil -- South America; Paleontology
In the midst of these shells on San Lorenzo, I found light corallines,
the horny ovule-cases of Mollusca, roots of seaweed (Mr. Smith of
Jordan Hill found pieces of seaweed in an upraised pleistocene deposit
in Scotland. See his admirable Paper in the “Edinburgh New
Philosophical Journal” volume 25 page 384.), bones of birds, the heads
of Indian corn and other vegetable matter, a piece of woven rushes, and
another of nearly decayed COTTON string. I extracted these remains by
digging a hole, on a level spot; and they had all indisputably been
embedded with the shells. I compared the plaited rush, the COTTON
string, and Indian corn, at the house of an antiquary, with similar
objects, taken from the Huacas or burial-grounds of the ancient
Peruvians, and they were undistinguishable; it should be observed that
the Peruvians used string only of cotton. The small quantity of sand or
gravel with the shells, the absence of large stones, the width and
thickness of the bed, and the time requisite for a ledge to be cut into
the sandstone, all show that these remains were not thrown high up by
an earthquake-wave: on the other hand, these facts, together with the
number of dead shells, and of floating objects, both marine and
terrestrial, both natural and human, render it almost certain that they
were accumulated on a true beach, since upraised eighty-five feet, and
upraised this much since INDIAN MAN INHABITED PERU. The elevation may
have been, either by several small sudden starts, or quite gradual; in
this latter case the unrolled shells having been thrown up during gales
beyond the reach of the waves which afterwards broke on the slowly
emerging land. I have made these remarks, chiefly because I was at
first surprised at the complete difference in nature, between this
broad, smooth, upraised bed of shells, and the present shingle-beach at
the foot of the low sandstone-cliffs; but a beach formed, when the sea
is cutting into the land, as is shown now to be the case by the low
bare sandstone-cliffs, ought not to be compared with a beach
accumulated on a gently inclined rocky surface, at a period when the
sea (probably owing to the elevatory movement in process) was not able
to eat into the land. With respect to the mass of nearly angular, salt-
cemented fragments of sandstone, which lie under the shells, and which
are so unlike the materials of an ordinary sea-beach; I think it
probable after having seen the remarkable effects of the earthquake of
1835 (I have described this in my “Journal of Researches” page 303 2nd
edition.), in absolutely shattering as if by gunpowder the SURFACE of
the primary rocks near Concepcion, that a smooth bare surface of stone
was left by the sea covered by the shelly mass, and that afterwards
when upraised, it was superficially shattered by the severe shocks so
often experienced here.
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