THE LEHIGH COAL-BASINS.
do not propose to include under this head the old Lehigh Summit mines or the Room Run mines : they belong properly to the first or Southern anthracite coal-field, in the eastern end of which they are located.
Under the general head of the Lehigh coal-basins we include those com paratively small fields or basins of coal lying between the first and third anthracite coal-fields, and to the east of the second or Middle coal-field, in which they are sometimes, though not properly, included. They have a separate and distinct existence, and are as peculiar in their form and features as any of our independent coalfields; but they resemble each other, in general structure, character, and quality of coal, very closely. They are all comparatively narrow, and generally shallow, containing only the lower or white-ash veins ; but these are in their most favorable conditions. They are large, uniform, and productive, and include the Mammoth and all the underlying veins.
Below we give a transverse section of the four principal parallel basins, with their undulations and intermediate basins or synclinal troughs.
The Green Mountain basin is comparatively small and not yet developed. The principal basins in the section, and in this, the Lehigh region, except the Lower Big Black Creek basin, are the Beaver Meadow, Hazleton, Big Black Creek, and Little Black Creek basins. The Lower Black Creek basin is a continuation of the Big and Little Black Creek basins, though their continuity is probably broken at the point of intersection by an ele vation of the conglomerate which " throws the coal over," in mining phraseology. A glance at the accompanying map will be necessary to obtain. a comprehensive and clear impression of this group.
There are three or four other small patches of coal within this cluster of Lehigh basins : one of these, the Dreck Creek basin, lying between the Beaver Meadow and Hazleton basins, we have not laid down on the map, on account of the uncertainty of its character and the insignificance of its size. We must here remark, however, that this narrow and shallow trough of coal has never been fairly tested, and we have neither data nor authority which would justify a condemnation of this basin.
Another of those small narrow basins exists on the Big Tomhickon Creek, which appears to be a continuation of the south fork of the Hazle ton basin, extending from its western extremity. This basin is of more importance than the Dreck Creek basin, but we believe it does not contain the Mammoth vein. There are several other small patches of coal in this vicinity, of which, however, nothing very definite is known. The McAuley Mountain deposit can scarcely be called a basin, as it is on the top of a mountain, yet has the basin-shape, and has only been preserved from the powerful denuding forces which broke up this portion of the region by the heavy conglomerates and sandstones which underlie the deposit, and which resisted the rush of waters. The McAuley basin is detached
from the main group, and exists as the most western of the series, and appears as a prolongation of a coal formation formerly existing in the Nes copeck Valley. The evidence of the former existence of coal to the west and northwest of the present Lehigh group is the numerous beds of con glomerate which cap the elevations throughout this region. The undu lating character of the Umbral or red shale strata, and their fine, soft, yielding nature tells the story of destruction which the rocks around so fully confirm.
The Lehigh group occupy part of a vast undulating plateau that formerly existed from the Nesquehoning to the Nescopeck Mountains, and which filled the deep wide valleys now occupied by the Quakeake and the Nescopeck streams. The blue color on the map distinguishes the existing portions of the conglomerate, as the black denotes the coal. The pink represents the red shale or Umbral ; and those wide areas shaded by this color were undoubtedly once covered by the blue, or base-rock of the coal measures, if not the coal itself. The elevation of this conglomerate plateau is about 2000 feet above the sea-level, while some of its deepest coal-basins are nearly 1000 feet below the surface, or only 1000 feet above the sea. Yet the lowest part of the deepest basins is far above the surface-level of the Pottsville basins, which are probably over 3000 feet deep, or 2500 feet below the level of the Atlantic. Port Carbon is 600 feet above tide water, and Hazleton about 2000 feet. The depth of the basin beneath Hazleton is 900 feet, which still leaves a difference of 500 feet between the bottom of the deepest Lehigh basin and the top of the deepest Schuylkill basin.
The Schuylkill basins were originally deeper than the Lehigh basins; but there can be but little doubt of the fact that the surface, or rather outcrop, of the coal at Pottsville was at one time on a level with the surface or outcrop of the coal at Hazleton. The depression has been since the formation of coal, or, perhaps, continued during its formation. The Lehigh basins have not been elevated, as some suppose; but, on the contrary, the Schuylkill basins have been depressed, as their steep angles and reversed or overtilted strata amply testify.
The area of the present conglomerate plateau, on which are located this group of basins, is between 150 and 200 square miles, while the coal area is between 35 and 50 square miles. The probable ancient or denuded area is not less than 1000 square miles.