|
|
|
|
 |
|
The rocky record of the four counties embraced in this history is a very simple one, and will require for the general reader no extended description. Necessarily, for the most part, their account is based upon the investigations made for the State by those able geologists Lardner Vanuxem and James Hall, as recorded in their reports of the third and fourth geological districts. We shall freely use the exact language of these reports – it may be often without note of credit or sign of quotation – when it shall seem so best for our purpose.
Although the fossils are abundant in many of the rocks, neither their character nor the limits of this article will warrant special mention of any. The reader is referred for such details to the works above named, where the characteristics of several groups are fully described and illustrated.
Of the rock formations in the four counties, the lowest exposed rocks are in the county of Tompkins. The deep basin of Cayuga Lake and the ravines traversed by its principal tributaries, which in some cases are cut down nearly to the lake-level, afford the naturalist rare opportunities for studying the structure, thickness, and succession of strata that make up the lower groups.
The dull shales of the Hamilton group, the lowest visible rocks in the county, are of great extent, and form the shores of Seneca and Cayuga Lakes for more than half their length. The six minor divisions of this group are especially well developed on the eastern shore of Cayuga Lake, north of Ludlowville. This group is of small practical importance in its relation to the four counties, and is chiefly distinguished for its great thickness and wide distribution over the State. Its thickness is from three to seven hundred feet, yet it is quite deficient in building materials. "It abounds in fossils, such as shells, corals, trilobites, fucoids, and a few plants resembling those of terrene origin. In organic remains it is the most prolific of all the New York rocks."
The Tully limestone succeeds the Hamilton shales, and first appears about three miles southward from Kidder’s Ferry, presenting a thin and occasionally undulating stratum, which varies from ten to sixteen feet in thickness, the bottom layer being frequently five feet thick. The color is blackish-blue and brown.
"Blocks of this limestone are very common along the lake-shore, where the ledge is seen, requiring but to be encased with ice, the water of the lake raised, and then transported south and deposited, to account for the blocks of the same limestone which there exist and are burnt for lime, - one of which is so large and so much buried as to appear to be in its original place, and was supposed to be the projecting part of a ledge of limestone rock. These transported blocks are found at various levels to the south and east of Ithaca." *
"The mass is too thin to be of importance in its effects upon spring or upon the character of the soil. It is the most southern limestone in the State from which lime is burned, and in this respect is important to the inhabitants of the district along which it extends. Being from six to eight or ten miles south of any other point where limestone is quarried, it becomes of great value, both for burning to lime and as a rough building-stone." **
The Tully limestone and the rocks of the Hamilton group disappear under the lake three miles north of its head. ***
* Report of Third District, p. 167.
** Report of Fourth District, p. 215.
*** The average dip of the rocks of this part of the State is about twenty-five feet to the mile. Direction of dip, a little west of south. – bid., p. 239.
The Genesee slate succeeds the Tully Limestone, and continues its darker line two miles farther south before it in turn disappears. In the ravines east of Ludlowville the slate is well exposed, from the limestone upwards, presenting a mass from eighty to one hundred feet in thickness, and forming several high falls. The greatest exposition of this rock is along Cayuga Lake, south of Ludlowville. This rock is of jointed structure, intersected by vertical planes placed nearly at right angles. "It often shows, where sheltered, a saline efflorescence of two or more different salts."
Because of the higher level of Seneca Lake, the several rocks we have mentioned pass under its surface somewhat farther north than the points of disappearance of the same rocks along Cayuga Lake.
The Genesee slate above and the shales below the limestone, yielding more readily to destructive forces, have given up much of their substance to form the beaches of flat gravel that occur in their vicinity, while the harder limestone remains, projecting the bold, suspended ledges.
The Portage and Ithaca groups occupy the northern part of the counties of Tompkins and Schuyler, being there the highest rocks. The Ithaca group, holding a middle position between the Portage and Chemung masses, has many of the characteristics of both, and appears to assimilate more nearly to the former in the eastern district, and to the latter in the western. Mr. Vanuxem says, "The fossils which will show this mass to be a distinct one, should it be such, will be found towards the lower part of the inclined plane." * Mr. Hall, in his report of the fourth district, gives as his reason for merging the Ithaca and Chemung groups "the impossibility of identifying them as distinct by any characteristic fossils."
*The old railroad place at Ithaca.
The line of division between these rocks and those below is distinctly traced on Cayuga Lake in a compact sandstone, in some places exceeding a yard in thickness, resting on the Genesee slate, and gradually approaching the lake surface in its course southward. The mass consists of coarse shales and sandstones, of varying thickness and little regularity of arrangement, but of marked continuity. Many of the sandstones furnish building materials and "flags" for sidewalks, of good quality, and the hill-sides about Ithaca are dotted with quarries and workings, old and new.
"Buttress" cliff, near South Point, on Cayuga Lake, and thence extending two miles northward, is a very picturesque portion of the Portage rocks.
The sandstones of the Portage group produce falls in the streams which flow over them, as well as some of the most beautiful cascades in the State. Taghkanie and Hector Falls are thus produced; the former, with its sheer plunge of 215 feet, is the highest perpendicular fall in the country east of the Mississippi.
The line of division between the Ithaca and Chemung groups is not well defined, and many of their contained fossils are similar, if not identical.
The Chemung group rests upon the Portage and Ithaca rocks (called "Portage" henceforward for convenience), and may be characterized as "a series of thin-bedded sandstones or flag-stones, with intervening shales, and frequently beds of impure limestone, resulting from the aggregation of organic remains."
The sandstones of this group are coarser with a greater admixture of clay, than those of the group immediately below. In the high hills south of Cayuga Lake this group first appears, and is well exposed in the upper part of the "inclined plane" at Ithaca, increasing in thickness with the elevation farther south. All the southern portions of the counties of Schuyler and Tompkins, including the southeast part of Dryden, and that part of Tioga and Chemung Counties north of the Susquehanna and Chemung Rivers, are occupied by the rocks of the Chemung group, as also are the highest elevations of Hector in Schuyler County.
In the deep ravines within the territory named, and especially at the Chemung "Narrows" and in the valley of Cayuta Creek, these rocks are well exposed and afford fine opportunities for examination.
Although the high hills bordering the Cayuta rise to nearly six hundred feet above the stream, no other rocks appear than those of the group we are describing.
Some of the layers afford good building-stone, but often the proportion of argillaceous matter is so great that it will not bear exposure without crumbling. Notwithstanding this fact, many quarries have been opened near Ithaca, Owego, Factoryville (Waverly), Elmira, Millport, Horseheads, and other places, some of which have been worked many years, and still supply satisfactorily all local demands for building purposes.
The best stones for flagging found in this part of the State are quarried at Ithaca from the lower strata of this group. They range in thickness from three to six inches.
The imposing and solid stone structures of Cornell University, built of materials quarried on the spot, bear witness to the economic value of the most solid portions of the two groups last described.
The removal of the rocks of the Chemung group in the southern counties has formed the magnificent, fertile valleys of these two large rivers, whose waters unite at the southern limit of that broad plain which extends from Athens to and beyond Factoryville.
This plain shows "four distinct terraces of alluvion, the highest rising some sixty or eighty feet above the river."
North of Factoryville the hills reappear and continue for fifteen miles unbroken, until they reach a series of east and west valleys connecting the valley of the Catatunk, at Candor, and the south end of the broad plain at Spencer with the valley of the Cayuta, at Van Ettenville.
The hills again appear north of Van Ettenville, and continue northward unbroken to Cayuga Lake, showing their highest and most rugged elevations near the junction of the four counties, from whence they decline, with smoother features, until they reach the lake.
From the "summit" of the valley at North Spencer, which is 1059 feet above tide and 672 feet above Cayuga Lake, the waters of Cayuga Inlet descend through the lower portion of the Chemung and nearly the whole of the Portage groups. This valley is so bordered with "rounded alluvial hills (spurs) or terraces" that no considerable exposure of the strata there exists; while the Catatunk, rising in Danby, at an elevation greater by 254 feet and flowing southward, runs a parallel course through rocks of the Chemung group only.
The county lines separating Tompkins and Schuyler from Tioga and Chemung follow nearly the line of natural division in those counties between the waters flowing northward to Seneca and Cayuga Lakes and those flowing southward to the Susquehanna. *
South of the Susquehanna River, the next higher rocks, those of the Catskill, or Old Red Sandstone group, first appear, but are not largely developed until the State line is passed. They present no valuable features within the territory we are describing.
Iron pyrites occurs in abundance in most of the shales of the several groups mentioned, which on decomposing imparts a rust color to the rocks. "The same gives origin to numerous small beds of bog-ore which occur in many localities. One of them near Elmira and another at Big Flats furnishes a tolerably pure ore, but in most places it appears as a ferruginous tufa. In Southport there is a small deposit of bog-ore, which apparently owes its origin to the destruction of the conglomerate of the Carboniferous system." **
*The three grand natural passes between the river and lake systems of Central New York are within the four counties under consideration, and are now traversed each by a railroad, and on (that of Catharine Creek) also by a canal.
** Report of Fourth District, p. 479.
Along Seely creek, a tributary of the Catatunk from the west, at North Spencer, is to be seen a vein of ferruginous shale, two or three feet in thickness, composed of kidney-shaped masses of various sizes.
The shales of the Portage and Chemung groups are highly bituminous, and probably are the source of the carbureted hydrogen gas emitted from many of the springs of the district. At Ithaca it has often appeared in newly-driven wells, in some cases rushing out with considerable force, and burning freely at the surface.
A spring, highly charged with sulphur, breaks forth from the side of Six-Mile Creed ravine, while at the "Steamboat Landing" is an old-fashioned "bored" well, which has been flowing, since 1839, a copious stream of like strength and quality.
Near Watkins, on the Seneca Lake, is a chalybeate spring; also an unimportant brine spring which gives some traces of iron.
All the springs named occur within the limits of the Portage group.
Thin Laminac of coal are found in the black shales, but are nod evidence of its existence in any considerable quantity in these rocks. The specimen found is usually the extent of the deposit. Ignorance of the structure of these rocks and their relation to the Carboniferous system has caused a waste of much time, labor, and money in search for beds of coal or salt, based upon slight and occasional traces of the one or the other occurring in them. "It is unnecessary to say that these attempts always fail, as do all similar undertakings in the rocks of this period."
Marl is abundant in many localities. There is an extensive bed about six miles south of Ithaca, and other small ones near Newfield, while in the low ground at the head of Cayuga Lake there are several deposits. At Ithaca the Tully limestone, being accessible, is preferred for lime making; hence the marl there remains intact.
There are also sundry beds of marl in Chemung County, near Millport, and one about two miles northeast of Johnson’s settlement. A bed exists also near Horseheads, and in the town of Dix, at the Beaver dam, an extensive deposit, which is burned for lime.
Springs. – The country underlaid by the rocks of the Chemung and Portage groups is well watered by never-failing springs; but the practice of indiscriminately clearing the woods from hills and valleys will, in time, result in drying up their sources of supply, which now send refreshing waters through many mysterious, hidden channels to the surface. The vertical joints in the thicker masses of black shale often afford vents for the waste of water downward. The only remedy, in such cases, is to bore through the black and porous to the more solid green shales below.
Some remarkable results have been obtained by means of sundry "driven" wells in the towns of Dryden, Danby, and Ithaca. In several the water rises from three to thirty feet above the surface, - one in Danby attaining the latter elevation, and another, at Ithaca, the height of from twelve to thirteen feet.
Agricultural Considerations. – In the valleys and on the low northern slopes of the Portage groups, in the counties of Tompkins and Schuyler, the soil produces wheat with the same case and certainty as the formations farther north. This is true also of the deep valleys farther south, including those of Chemung and Tioga Counties, which have received, intermixed with the northern "drift" deposits, a liberal supply of calcareous materials. The higher lands in the southern portion of the district, having little or no lime, or equivalent ingredients, are naturally best adapted to grazing and the coarser grains. The application of certain manures or phosphates may modify these conditions; but experience alone can determine how economically.
|
