HISTORY OF

SARATOGA COUNTY, NEW YORK.

by NATHANIEL BARTLETT SYLVESTER

1878

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CHAPTER IV.

GEOLOGICAL OUTLINES.

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I. - ERAS - AGES - PERIODS.

The rocky groundwork which underlies the county of Saratoga presents, to the student of geology, many features of surpassing interest. Yet all that properly seems to come within the scope of this work is a mere outline of the subject, so far as it necessarily bears upon the economic interests and historical associations of the county and its surroundings. And this outline will be confined principally to the more striking geologic features of the county; in a word, to the departments of physiographic and historical geology, leaving to the interested student the no less inviting fields of lithological and dynamical geology, of which the county is so rich in natural illustrations, to be studied in the field itself here spread out before him, or in the numerous special works devoted to the science.

The science of geology unfolds to us to some extent the mysteries of the world's creation. The earth itself, like the plant or animal it sustains on its surface, is a thing of growth, of development. The different periods of this growth and development are more or less distinctly marked upon the rocky structure of the earth by the various fossil forms of animal and vegetable life found therein, and these successive periods so marked are termed geologic epochs, times, or ages.

The geologic epochs or ages of the world are distinguished by the progressive development of the various forms of animal and vegetable life, from the lowest to the highest forms of existence.

The extremely interesting geologic features of Saratoga County can be best explained by referring somewhat in detail to the geologic ages of the world based upon the progress of life and living things, and the different periods of geologic time marked by these successive ages.

The subdivisions of geological time are eras, ages, and periods.

The eras are five in number, marked in all by seven ages of development in organic life.

I. - ARCHÆN OR EOZOIC ERA. - (The Dawn of Animal Life.)

1st. Laurentian Age.

II. - PALÆOZOIC ERA. - (Old Life.)

2d. The Silurian, or Age of Mollusks.

3d. The Devonian, or Age of Fishes.

4th. The Carboniferous, or Age of Coal-Plants.

III. - MESOZOIC ERA. - (Middle Life.)

5th. The Reptilian Age.

IV. - CENOZOlC ERA. - (Recent Life.)

6th. The Age of Mammals.

V. - PSYCHOZOIC ERA. - (Era of Man.)

7th. The Age of Man.

These five several eras of geological time and the seven successive ages of life development on the earth are well represented in the accompanying table, which is copied in great part from the one prepared by Prof. James D. Dana for his "Manual of Geology." Beginning with the oldest, at the bottom of the table, the Laurentian, Silurian, Devonian, and Carboniferous periods are represented by series of American rocks in the natural order of their formations. The rest of the series is taken from European geology, in which the later ages of the earth's rocky growth are far more distinctly represented than in America.

As no deposited rocky beds are to be found within the borders of Saratoga County higher in the series than the Hudson river group of slates and shales, the fossils of which rise in fact no higher in the scale of being than the Lower Silurian age, it will be seen that, geologically speaking, Saratoga County is very old.

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II. - THE LAURENTIAN AGE.

The great Canadian Laurentian mountain system, which is so finely developed in northern New York and stretches its rugged, towering masses far down into Saratoga County, begins on the coast of Labrador near the mouth of the river St. Lawrence and extends up along the northern bank of the river to a point near the city of Quebec. From this point it recedes from the river inland for some thirty miles or more until it crosses the Ottawa river above Montreal. After crossing the Ottawa the chain again bends southerly towards the St. Lawrence, and a spur of it crosses the great river at Thousand Islands into northern New York, and, spreading out eastward and southerly, forms the rugged mountain system of the Adirondack wilderness.

The Laurentian system of rocks constitutes the oldest known strata of the earth's crust. In the Laurentian rock-beds are to be found the remains of life-forms of life's early dawn.

Until within a few years the Laurentian system has been termed by geologists Azoic, or without life, but the more recent discoveries show evidences of both animal and vegetable life in great abundance, but life in its earliest forms. It is the prehistoric, mythical era of geologic time now called the Archæan, or Eozoic, time, - the time of dawning life.

The Laurentian rocks are mostly of the metamorphic series, related to granite, gneiss, syenite, and the like. But they embrace only the most ancient of these rocks, for the New England granites and schists belong to later ages.

Besides true granite and gneiss, there are diorite, a rock formed of feldspar and hornblende without quartz, and also very extensive ranges of coarse granite-like rocks of grayish and reddish-brown colors, composed mainly of crystallized Labradorite, or a related feldspar, or this feldspar joined with the brownish-black and bronzy, foliated hyperstene. These rocks also contain green, brown, and reddish-colored porphyry, serpentine, limestone (statuary marble), granular quartz, magnetic and specular iron ore, a hard conglomerate ophiolites, or verd-antique marbles of different varieties, garnets, tourmaline, scapolite, Wollastonite, sphene, rutile, graphite, phlogopite, apatite, chondrodite, spinel, zircon, and corundum.

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III. - POTSDAM AND CALCIFEROUS SANDSTONES.

The rocks next above the Laurentian series belong to the Lower Silurian age and to the Potsdam or Primordial period. First in order comes the Potsdam sandstone, and next above and resting on that is the calciferous sandrock. The calciferous sandrock ia the grayish rock which underlies all the northwestern part of the village of Saratoga Springs, and may often be seen cropping out near North Broadway in all the upper part of the village.

A narrow belt of calciferous sandstone, covering Potsdam sandstone, extends across the county, lapping over on to the lower edge of the old Laurentian rocks.

In this Primordial period the remains of life appear in its lower marine, but not fresh-water forms, in great abundance.

These rocks were deposited in the shallow beds of the Primordial ocean, when its waves beat along the old Laurentian shore.

Algæ, or sea-weeds, are the only plant forms found in the Potsdam sandstone and Calciferous sandstone epochs.

The animal remains of this period are all marine.

1. Among Protozoans are found sponges and rhizopods.

2. Among Radiates are found crinoids, graptolites, and, it may be, coral-making polyps.

3. Among Mollusks are found bryozoans, brachiopods, conchifers, pteroyods, gasterpods, and cephalodes, thus representing all the grand divisions of mollusk life.

4. Among Articulates may be found marine worms, crustaceans of the trilobite tribes, and ostracoids.

The most abundant fossils found in the Potsdam beds are the brachiopod, genus lingula, and trilobites. The trilobites were the largest animals of the seas and highest in rank. Of them there were numerous kinds, varying in size from the sixth of an inch to two feet.

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IV. - THE TRENTON LIMESTONE PERIOD.

Next above the Potsdam and calciferous sandrocks there appears stretching across the county a narrow belt of the Trenton period.

First in order, overlapping the calciferous sandrock or abutting against it, come the Birdseye, Black River, and Trenton limestones. The Chazy limestone seems to run into the others of the group before it reaches the Hudson river, on the borders of the county.

In this period sea-weeds are the only fossil plants. Two species are found, the Buthotriphis gracilis and B. succulosus.

The seas of the Trenton period were densely populated with animal life. With the Trenton period first appear species of undoubted polyps, the true coral animals of the seas.

The different species of the lower forms of animal life shown in the fossils of the limestone period are too humorous to name in this article.

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V. - THE HUDSON PERIOD OF SLATES AND SHALES.

Covering all the southeastern part of the county of Saratoga, as the Laurentian rocks cover the northwestern, lie the strata of the slates and shales of the Hudson river group. Between these wide beds of slate and shale, and the equally wide beds of the Laurentian formation, run the narrow strips of the Potsdam calciferous sandstones and Trenton limestones. Such, in a word, is the interesting geologic situation of Saratoga County.

The life, both animal and vegetable, of the Hudson river period, is quite identical with the life of the Trenton period, none of which, the reader will bear in mind, rises higher in the scale of being than the sub-kingdom of Articulates.

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VI. - THE POST-TERTIARY PERIOD.

The next period that attracts our attention in studying the geology of Saratoga is the Post-tertiary period, which ushers in the present state of things on the earth's surface.

After the highest strata of the Hudson group of rooks had been deposited in the primordial ocean's bed, there must have been an upheaval of the land above the waters in the region of the Hudson valley, leaving these rocks high and dry. But countless centuries of time intervened before the age of man upon the earth.

The Post-tertiary period in America includes two epochs:

1. The GLACIAL, or that of drift.

2. The CHAMPLAIN.

Next follows (3) the TERRACE epoch, a transition epoch, in the course of which the peculiar Post-tertiary life ends, and the age of man opens upon the world.

The Drift period is well represented in all the central and western parts of Saratoga County.

The term Drift includes the gravel, sand, stones, and boulders, forming low hills, and covering even the mountain tops in many places.

The Drift is derived from the rocks to the north of where its beds occur, and is supposed to have been transported by the ice fields of the glacial period. In many places the surface rocks of the limestones are worn smooth, and marked by the scratches and grooves caused doubtless by the passage over them of heavy beds of ice, tilled with stones, sand, and gravel.

The Champlain and Terrace epochs are well represented in Saratoga County by the extensive beds of what are called "Saratoga Sands," and the clay hills of the river-valley, which it would seem were deposited along the receding shore of a later ocean that had again covered the land during the Post-tertiary period. It is quite evident that the long, narrow bed of Saratoga sands, which runs across the county from northeast to southwest, was once but the shifting sands of the ocean's beach, when its waters washed the foot-hills of the Adirondacks, in the Post-tertiary world.

A volume could be written upon the interesting geology of the county of Saratoga, of which but a mere outline is above given.

In a succeeding chapter something will be said upon the origin of the numerous and wonderful mineral springs of Saratoga County, a subject properly belonging to geological science, yet so closely identified with the industrial and social interests of the people of the county as to make it to them a matter of absorbing interest.

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