Erie County, Pennsylvania

Chapter III- Geology

The geological formations are comprised within the Devonian period, and include in the nomenclature of the State geological report, in descending order, Corry and Cussewago Sandstone, Venango Oil Sand Group, Chemung formation, Girard shales and Portage flags. The age of the upper strata has not been definitely determined. The Corry and Cussewago beds belong either to the Pocono, No. X, or Catskill, No. IX, formation, and the Venango Group is by different geologists ascribed to both Catskill and Chemung ages.

Topography.-- The mean level of Lake Erie above the ocean in New York Harbor is 573-7/10 feet. Facing the lake, a steep terrace of sand and clay, from 50 to 100 feet high rises, and through this terrace break three or four fair sized streams and numerous smaller ones, descending a slope which extends upward from the lake terrace to a line which may be drawn from the northeast corner of Greenfield Township, through Greenfield, Greene, Summit, McKean and Franklin. The slope is high and short at the New York line, hence the lake streams in the east part of the county are short and rapid. Along the Ohio line, the slope is long and low, and the streams here are larger. Walnut Creek heads only eight miles from the lake shore, but is fifteen miles in length. Elk Creek is thirty miles long, yet its head is only ten miles back from the shore. Conneaut Creek runs twenty-six miles in Pennsylvania, then crosses into Ohio. The course of all these streams is the same, first down the upper part of the slope toward the lake, then westward in a deep gully parallel to the lake, then out through a ravine straight to the lake shore.

South of the divide, French Creek is the largest stream in Erie County. The valleys are flat, one or two miles wide, and are bordered by low and gently rounded hill slopes, separated by low, flat table-lands. Swamps occur along the South Branch of French Creek, and Tamarack Swamp stretches across the water-shed of the divide, on the highest land of the Waterford (McKean) Township line; elsewhere in Erie County, swamps are rare. Several lakes are found in the low valleys.

Drift Period.-- There is little land in the county that has not been affected by the great ice-sheet which in glacial times moved southeastward over the entire county; except possibly the hilltops which rise 1,200 feet above the level of the lake; in them no erratic boulders have been observed. While the ice was smoothing down the lower flat country of the western townships, it was operating through the deep and narrow vales of the eastern ones, leaving the high hill-tops comparatively untouched. The character of drift deposits can be studied along the shore of Lake Erie toward the Ohio line, where they constitute a terrace bluff fifty to eighty feet high, out of which the waves are constantly removing the clay and fine sand, leaving the coarse sand, pebbles and boulders to be daily rounded and polished on the beach. The matrix is a bluish-white tough clay, imbedding fragments, mostly angular, of all kinds of crystalline rocks, with sandstone, shale, black slate and limestone, and occasionally a large boulder of granite or gneiss. Quicksand is abundant in the drift deposits of the townships back from the lake.

Buried Valleys.-- Scarcely a stream of any considerable size in Erie County flows over a rock bed except those which cut deep ravines in the lake slope. The present water-courses meander along the upper surfaces of drift deposits, which fill up the ancient valleys to various heights above the old rock beds, even in some places where not living stream now flows. Bed rocks are seen along French Creek at Union, Mill Village, Le Boeuf and elsewhere, but the flood plain being two miles wide, there is ample space for a buried valley between the two wall slopes.

The most remarkable of these buried valleys are those through which two streams now flow in opposite directions from a common divide scarcely more elevated than other parts of the flood plain.

These ancient valleys were excavated, first, either by ancient rivers flowing from 100 to 400 feet below the present floors; or, second, by the great southward moving Canadian ice sheet, which as it retreated filled them up again with debris; or, third, they were first excavated by pre-glacial rivers, then deepened and widened by the moving ice and filled with its moraine to the present level. J. C. White, who make the geological survey of Erie County, ascribes the buried water ways to the plowing power of ice. The State Geologist, Prof. J. P. Lesley, takes exceptions to this view, and assigns the valleys to ancient rivers draining Northwestern Pennsylvania toward Lake Erie. Recent discoveries confirm this latter opinion. Prof. Spencer, of King's College, Windsor, Nova Scotia, has shown that a submerged valley bed crosses Lake Erie transversely, entering the present lake basin from the north, and by a bend northward and extending beneath the present drift filled water bed of Grand River, Upper Canada, then passing eastward into the head of Lake Ontario. Into this river channel, before the basin of the lake was filled, the Allegheny, French Creek, Mahoning and other streams doubtless poured their waters. Then came the glacial winter, and a thousand feet of snow and ice from the Laurentian Mountains moved slowly southward, filled the channel of this ancient river, damming back its waters and converting the forest-covered plain into an inland sea, banking itself against the Pennsylvania upland, and sending long glaciers across the country. By the melting of these glaciers, the valleys were filled with debris and a new topography formed. Lake Erie and the upper lakes were formed; the direction of Pennsylvania and Ohio rivers were reversed to the south. The pent-up waters of the inland sea found new outlets. The waters were lowered from terrace to terrace, and Niagara River was rapidly cut back till the present lake level was reached.

Terraces.-- Along Lake Erie, there are many fragmentary remains of old terraces, marking ancient higher levels of the lake surface. From the top of the bluff east of the Ohio line the land slopes up regularly and very gently, covered with a continuous beach sand and shore shingle to 225 feet above the present lake level. This sloping plain east of Erie, near Belle Valley, becomes a continuous flat at an elevation of 425 feet above the lake, covered in places with beach sand, etc. On the irregular escarpment of higher land, which rises from this flat on the south, no shore deposits were found. In Harbor Creek and western northwest townships, is the nearest approach to a series of terraces; three miles back from the lake, at 577 feet elevation, is a wide level, destitute of beach deposits; an abrupt descent to about 500 feet elevation reaches to the remnant of a terrace, covered with beach sand and shingle; then follows a rapid descent, wholly destitute of beach deposits to 300 feet elevation, to a broad sloping plain, covered with beach sand, etc. At the northern edge of this plain, 220 feet above the lake, is a genuine terrace of beach sand forty feet high, from the foot of which a plain one mile wide extends to the top of the bluff, 170 feet high, which descends steeply to the water's edge.

Dip of the Rocks.-- Everywhere throughout Erie County, the strate appear to be horizontal, but in reality they possess a slight dip southward and westward. Along the Corry meridian it is twenty-five feet per mile; from Erie to the Ohio River, it is twenty feet per mile, and farther west it is slighter. The dip westward along the parallel of Wattsburg is eleven feet per mile, and along the southern line of the county seven feet per mile. Two miles south of Middleboro, there is a slight northward fall of the rocks. Many other slight variations and undulations may exist, but if so they have not been detected.

The Shenango Group.-- This group probably representing the Pocono formation, No. X, is the highest geological strata found in Erie County, The Shenango Shale deposit generally consists of blue, gray and brown clay-shales and in Crawford County varies from thirty-six to sixty feet in thickness; if found in Erie County at all, its bottom layers are left on the highest hill-tops. The Shenango sandstone, immediately below the shale, is from fifteen to thirty-five feet thick in Crawford County, and in Erie County caps two or three isolated knobs in Concord Township.

The Meadville Group, immediately below, and with the Shenango corresponding to the Cuyahoga Shales of Ohio, in Crawford County, consists of Meadville Upper Shales, Meadville Upper Limestone, Meadville Lower Shales, Sharpsville Upper Sandstone, Meadville Lower Limestone, Sharpsville Lower Sandstone and Orangeville Shales. In Erie County they have scarcely an existence. The Sharpsville Upper Sandstone crops out in the eat end of the county in a few isolated knobs.

The Oil Lake Group, a part of Pocono Sandstone, No. X, and supposed by Mr. White to be identical with the Berea grit of Ohio, includes the Corry and the Cussewago Sandstones and the Cussewago Limestone and Shale. The Corry Sandstone is found in a few of the highest hills in the southern parts of Concord, Union and Le Boeuf Townships. One mile south of Corry, about 300 feet above the city, and 1,160 feet above Lake Erie, are two quarries. Only eight feet of the sandstone have escaped erosion, and four feet are so shattered that the lower four feet only can be used. The Cussewago Limestone is exposed in D. Matterson's ravine, near the center of Concord Township, where it is a foot thick.

Beneath the Cussewago sandstone and down to the Venango group, a distance of about eighty feet, occurs a series of very fossiliferous drab, bluish and gray sandy shales, sometimes shaly sandstone, called the Riceville Shale.

The Venango Oil Sand Group includes the most important strata of Erie County. It varies in thickness from 250 to 350 feet, and crops out over most of the surface south of the great divide. In the counties further south, it is this group buried far beneath the surface that yields petroleum. The First, Second and Third Oil Sands there correspond with the Venango Upper, Middle and Lower Sandstones.

Venango Upper Sandstone.-- A coarse sandstone is the only reservoir of free petroleum, and a loose gravelly sandstone the only kind from which an oil producer expects a free flow in large quantities. The Upper and Middle Venango sands of Erie County are in the form of compact, fine grained, muddy flagstones, and consequently contain little or no oil. The Venango Upper Sandstone lies high up the hills and the flags are often grayish-white. Two miles west of Edinboro, at Anderson's quarry, they are bluish-white, smelling of petroleum. At Russell's quarry, just north of Corry, a bluish-white sandstone lies at 1,070 feet elevation above the lake, the seams and crevices of which hold petroleum. Underlying the Upper sand are pale blue shales, 90 to 100 feet thick, containing fossil shells of the Chemung type.

The Venango Middle Sandstone makes little show in Erie County, being merely marked by a greater number of sandy shales or flagstone layers in the mass of softer shales. At Harry Comer's quarry. however, in Washington Township, are exposed twelve feet of bluish-white sandstone, smelling strongly of petroleum. In the Maynard's Run bluffs, Amity Township, the same flags crop out 125 feet above the Le Boeuf Conglomerate. (Venango Lower Sandstone.) In the interval of from 100 to 125 feet between the Venango Middle and Lower Sandstones lie blue, gray and brown shales, very fossiliferous.

Venango Lower Sandstone.-- This famous "Third Sand" of the old oil regions outcrops on the great divide, and may also be seen in French and Le Boeuf Creek Valleys at the head of Elk Creek and Black Run and along Conneaut Creek, four miles above and below Spring Post Office. Its exposures always show it charged with petroleum, even where it is a sand and not a gravel rock. Its lower layers yield excellent building stone nearly everywhere, and it is the principal quarry rock of Erie County. There is often a division into an upper gravel or pebble rock and a lower sandstone. Petroleum pervades both, but there is more in the gravel rock. Among the quarries where it is taken out for building purposes are the Carroll quarries, Le Boeuf Township; Doolittle's quarry, Amity Township; Allen's quarry, two and one-half miles from Doolittle's; Reynolds' quarry, Summit Township; Howard's quarry, Franklin Township, and Goodman's, northeast from Howard's.

Its frequent exhibitions of petroleum with the numerous oil springs along its outcrop through Erie County have been a fruitful source of vain hope to explorers. Little supposing that the show came from the outcrop itself, and had nothing to do with the under rocks, explorers have drilled in almost every township to depths varying from 100 to 1,800 feet. Probably a half million dollars have been thus wasted in Erie County, sunk through measures underlying the exposed third oil sand, which the drillers were seeking far below. The whole petroleum deposit in Erie seems now to be practically voided, but a residuum of oil, lowered in gravity and partly oxidized, still remains, sufficient in places to unfit the stone for building purposes.

Below the Venango group are found 325 feet of typical Chemung strats, alternate groups of shale and sandstone, fossiliferous, with a thin limestone layer at the bottom. Some tolerably massive sandstone layers occur in the upper pat of the series, but no pebbles, nothing coarser than sand grains, have been noticed. It outcrops along the Lake Erie slope, and the top layers are exposed also in the valley of French Creek.

Beneath this is the Girard shale, a transition series between Chemung and Portage, a succession of ashen gray and bluish shales, with only an occasional sandy stratum. It is without fossils, except fucoids, and has a thickness of about 225 feet. It forms the drift-covered rock surface of Western Erie County facing the lake, and is finely exposed in every ravine which descends northward from the great divide, but especially along Elk Creek, above Girard. Seen from a distance, its blufs slopes look remarkably like the bowlder clay of the drift and sometime like vast banks of gray coal ashes. Its base or lowest laye is at lake level at Raccoon Creek, near the Ohio line, and 475 feet above lake level at the New York line.

The Portage Flags, the lowest strata of Erie County, consist of alternate layers of gray shale and thin layers of hard sandstone with no fossils except fucoids. The top layers rise from the water's edge two miles from the Ohio line, and slope up along the lake front until at the New York line they reach an elevation of 475 feet. Petroleum and gas issue from some of the thin sand layers. Collections of condensed gas undoubtedly exist, and in quarries not frequently cause explosions. The gas and oil wells of Erie vary in depth from 450 to 1,200 feet.

The following is a list of barometric elevations above Lake Erie of various points throughout the county: