stone found in descending the scale. The Hillsborough sandstone, the Sylvania sandstone, and the Upper Helderberg sandstone, occur in infrequent and irregular deposits, interstratified with the limestones to which they respectively belong, and while they appear in one section, they are wanting in a thousand. The Berea grit, on the other hand, is absolutely continuous, and is always definitely characterized as a sandstone. It overlies the greatest shale formation of the entire state, viz., the Ohio shales, which, taken together, range in thickness from 300 to 2,000 feet. The Bedford shale is blue, or red in color, the latter color being, whenever it occurs, an excellent mark of the formation. The Ohio shale consists of interstratified black and blue or gray bands. This is the series that is found below the Berea grit. The formation is as definitely marked by the strata that cover it. Its immediate roof is the Berea shale, a firm, fine-grained, highly petroliferous black shale, the lower part of which generally carries a pyritous band of a few inches or one or two feet in thickness, and which is excessively hard. In thickness the Berea shale ranges from ten to fifty feet. Above the Berea shale is found the Cuyahoga shale, light-colored and compact, throughout which occasional courses of sandstone of fine or medium grain are distributed. There is generally an accumulation of the sandstone at or near the base of the formation. It thus frequently happens that there is a sandstone course overlying the Berea shale, as well as the sandstone formation that underlies it. The Cuyahoga shale has a thickness of 150 to 500 feet. The usual figures are about 350 feet. The Cuyahoga and Berea shales, taken together, are second only in importance to the great series of shale deposits that underlie the Berea grit. Above the Cuyahoga, the Logan group is found, which is composed of sandstones, conglomerates and shales, the sandstones and conglomerates being the more characteristic formations. It is thus seen that the setting of the Berea grit is very effective as far as affording means for recognizing and identifying the stratum are concerned. It lies buried in a composite mass of shales, and in the largest part of the area occupied it is absolutely the only sandstone that belongs in this portion of the scale. There is no stratum that can dispute with it the place in which it occurs. More than this, the roof of the sandstone is black and hard, while the floor is always soft and often red. In northeastern Ohio the series is somewhat complicated, both in outcrop and under cover, but there are points enough here to afford means for safe identification in most instances. Along its outcrop, throughout the drift-covered portions of the state, the Berea grit itself makes the summit of the sections to which it belongs. The soft cover of the Cuyahoga shale has given way under glacial erosion in most instances, leaving the sandstone projecting as a terrace on its western boundary. This state of things has greatly facilitated the working of the sandstone as a quarry rock. A number of sections taken along one marginal and three radial lines, that is, either on the outcrop of the Berea grit, or that extends from the outcrop towards the interior of its field, will here be introduced in illustration of the statements already made. These sections are mainly derived from the records of the deep wells that have been recently drilled for oil and gas so extensively through the eastern portion of the state. Beginning on the western outcrop of the formation, we find an excellent series of sections available on an approximately north and south line extending from the lake to the Ohio Valley through the counties of Erie, Huron, Richland, Knox, Licking, Fairfield, Vinton, Jackson and Lawrence. This series is indicated on the accompanying map of the Berea grit territory as line A, and the sections are all approximately marginal. A. (1) At Berlin Heights, in Erie county, there is a largely worked exposure of the Berea grit three or four miles back from the shore of Lake Erie. It constitutes, in fact, the best known head-land of this entire portion of the state. The formation here has a thickness ranging between forty and fifty feet, and it is, in all respects, normal. It is underlain by the Bedford shale, which here displays its characteristic red color. From the Berea grit to the Devonian limestone that crops out a few miles to the westward, the vertical interval in this district is about 600 feet, as has been proved by a number of wells that have recently been drilled. This interval consists, after the red Bedford is passed, of an alternating series of black and blue shales. The Berea grit can be followed southward without difficulty or question entirely through Erie and Huron counties. It forms the surface rock through all this region, and is worked in a large number of local quarries along the line. (2) At Plymouth, on the south line of Huron county, it goes under the surface, its uppermost beds lying level with the bed of the Huron river. A well recently drilled in this town has furnished the following record, viz.: Drift 12 feet. Berea grit...... 40 White soapstone....... Red rock and brown shale (Bedford and top of Ohio shale)..... The thickness of the shales that occupy the interval between the Berea grit and the limestone is here 648 feet, but as will presently be shown, the lowermost 40 feet may possibly be referred to the limestone series. The top of the Berea is about 990 feet above tide at Plymouth, lying as it does on the low arch that forms the west line of northeastern Ohio. In this record, as in similar ones that are to follow, the drillers' terms and divisions will be mainly followed, but they will be interpreted as far as is necessary by the introduction of the geological names of the formations represented. At Shelby, ten miles south, the sandstone has descended to 140 feet below the surface. An excellent section was obtained here from the record of the deep well that was drilled in 1885. The record is as follows: The lower section of shale, 64 feet, is quite calcareous, and may be the Olentangy or Hamilton shale of Newberry. In this case, the thickness of the lower shale series will be 593 feet. A like correction, as has been suggested, may be applied to the Plymouth section. (3) The next section is found at Mansfield, twelve miles to the southeast. The record of the well drilled in 1886, as far as it concerns these points, is as follows: ow er member of shale column is counted with limestone......... 580 The upper surface of the Berea grit is here 640 feet above tide. (4) The next section is found in the record of the well drilled in 1884 at Mt. Vernon, Knox county, thirty-seven miles south and a little east of Mansfield. The record of the well is as follows, but recent drilling has shown the lower portion of it unreliable: The sandstone reported 60 feet thick at 1,174 feet, is probably nothing more than a hard phase of the ordinary shale. The interval between the Berea grit and the limestone is here 867 feet, by corrected figures, showing the thickening that took place in this portion of the old basin. This figure is in keeping with all others obtained in this general region. The top of the Berea grit is here 426 feet above tide. (5) Newark furnishes the next section. Two wells have been drilled here within the last year. The record of the first is as follows: The top of the Berea grit is here about 285 feet above tide. The record of the second well agrees with that already given as far as the former goes, but it has been drilled much deeper, and is to be carried still further down. The Devonian limestone was struck at 1,430 feet or thereabouts, showing the shale series here to be about 900 feet in thickness. This whole section rises to day twenty or thirty miles to the westward, and is, therefore, particularly clear and satisfactory. |