To show the vast power of the wearing action of sea-beaches, we need only appeal to the great cliffs 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 intombed 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.