along the present coast of Patagonia, and to the escarpments or ancient
sea-cliffs at different levels, one above another, on that same line of
coast.
The old underlying tertiary formation at Coquimbo, appears to be of
about the same age with several deposits on the coast of Chile (of
which that of Navedad is the principal one), and with the great
formation of Patagonia. Both at Navedad and in Patagonia there is
evidence, that since the shells (a list of which has been seen by
Professor E. Forbes) there entombed were living, there has been a
subsidence of several hundred feet, as well as an ensuing elevation. It
may naturally be asked, how it comes that, although no extensive
fossiliferous deposits of the recent period, nor of any period
intermediate between it and the ancient tertiary epoch, have been
preserved on either side of the continent, yet that at this ancient
tertiary epoch, sedimentary matter containing fossil remains, should
have been deposited and preserved at different points in north and
south lines, over a space of 1100 miles on the shores of the Pacific,
and of at least 1350 miles on the shores of the Atlantic, and in an
east and west line of 700 miles across the widest part of the
continent? I believe the explanation is not difficult, and that it is
perhaps applicable to nearly analogous facts observed in other quarters
of the world. Considering the enormous power of denudation which the
sea possesses, as shown by numberless facts, it is not probable that a
sedimentary deposit, when being upraised, could pass through the ordeal
of the beach, so as to be preserved in sufficient masses to last to a
distant period, without it were originally of wide extent and of
considerable thickness: now it is impossible on a moderately shallow
bottom, which alone is favourable to most living creatures, that a
thick and widely extended covering of sediment could be spread out,
without the bottom sank down to receive the successive layers. This
seems to have actually taken place at about the same period in southern
Patagonia and Chile, though these places are a thousand miles apart.
Hence, if prolonged movements of approximately contemporaneous
subsidence are generally widely extensive, as I am strongly inclined to
believe from my examination of the Coral Reefs of the great oceans--or
if, confining our view to South America, the subsiding movements have
been co-extensive with those of elevation, by which, within the same
period of existing shells, the shores of Peru, Chile, Tierra del Fuego,
Patagonia, and La Plata have been upraised--then we can see that at the
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