. Annals of the New York Academy of Sciences. Science. 48 ANNALS NEW YORK ACADEMY OF SCIENCES formations, essentially a silicified dune deposit such as that at San Juan^ also by Tertiary limestone reefs, such-as that at Quebradillas and at Guanica, or by the still older igneous and clastic series, such as that at Anasco, or by massive intrusives of a strictly igneous habit, such as that at Maunabo. It would appear from this that the former outline of the island must have been more irregiilar than it is at present and that the distribution of marginal formations is also not as regular as has be
. Annals of the New York Academy of Sciences. Science. 48 ANNALS NEW YORK ACADEMY OF SCIENCES formations, essentially a silicified dune deposit such as that at San Juan^ also by Tertiary limestone reefs, such-as that at Quebradillas and at Guanica, or by the still older igneous and clastic series, such as that at Anasco, or by massive intrusives of a strictly igneous habit, such as that at Maunabo. It would appear from this that the former outline of the island must have been more irregiilar than it is at present and that the distribution of marginal formations is also not as regular as has been represented in earlier Fig. 16.—Playa plain and marginal terrace View of the Playa plain (foreground), the marginal terrace (middle field) and the mountainous divide formed hy the Sierra de Cayey as seen from the "Central Machete" near Guayama. This terrace bevels across the upturned edges of shales, ashes and intru- sives of the older series and is probably due to marine cutting. Terraces At many places on both sides of the island there are comparatively smooth tracts having the appearance of bordering shelves Trhich represent true terraces. Their location along the sea margin and the compara- tively insignificant development of similar benches along the streams lead one to believe that they have an origin connected with the wave action and attack of the This interpretation is supported by the presence of these terraces along the coastal margin where stream action would not seem to have been able to reach. In any case, the presence of such terraces, which stand from 100 to 200 feet above the present sea level, indicate a former more submerged condition, so that the sea or streams, or both combined, were able to attempt base-leveling at that ele-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble th
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1877
