Any one familiar with our inverted dips and the peculiarities of the Shenandoah City, Coalcastle, Sharp Mountain, and other local irregulari ties, will comprehend at a glance the Wiconisco formation. There is no place, however, in the anthracite coal-regions so perplexing as this to the mere local observer: the more he investigates, the more will he be perplexed and mystified.
We have attempted to give an illustration in figure 93; but it is very difficult to convey a good impression of this singularly-contorted strata by word or design. If we are correct,—and we think there can be no doubt of it, for no other explanation is available,—the strata here are more inverted than at any other locality in the anthracite regions, and much like some of the inverted dips of the Blue Ridge formations in Virginia, or the gneissic strata at many points along the Atlantic slopes.
We do not pretend to give an exact delineation in figure 93, nor is it drawn to a correct and uniform scale; but we believe it to be generally a fair section across the coal formations of the North Fork at Bear Gap.
We would, however, call attention to one error, which has escaped our notice until too late to remedy it. The red shale ought to be represented between the conglomerates of the north and middle basins, where the thickness of this rock is, in consequence of this omission, much greater in appearance than it really is. We may also state that the lines drawn near the mouth of the tunnel, south of the middle basin, should represent con glomerate. With this explanation, the formation justifies, and the whole will appear plain.
This arm of the coal-field appears to have been originally a wide and rather shallow formation, containing three distinct basins: the middle one being smaller and much shallower than the outside basins. The process
of contraction, while it forced those basins closer together and elevated their edges, did not depress their on the contrary, elevated the whole mass, and, of course, affected the middle basin less than the deeper and longer outside basins.
The mines at Wiconisco are not deep; though we believe one slope is 600 feet long. Our notes say 300 feet; but our impression is that one of the slopes is of the above length, on an angle of about 25°. How far it may be to the bottom of this, the south or left-hand basin, we cannot say, but presume it cannot be less than 1500 feet. The miners and engineers of this place believe it to extend under the entire section, as shown by the dotted line. There are three seams in those basins, but only two are considered workable: their dimensions are respectively 5 and 11 feet. The coal is red-ash,—which proves them to be the lower beds; and we doubt not both belong to B, or the Buck Mountain bed, in its divided condition. This seam is always a red-ash in the anthracite regions, and, we understand, sometimes also in the bituminous fields; while the seams above B and below G are white-ash, and all above G, and sometimes inclusive of G, are red-ash,—or there are 10 red-ash seams and only 5 white-ash beds; but, nevertheless, there is perhaps more white-ash than red-ash coal, on account of the greater thickness of the Mammoth and the greater extent of the white-ash than the red-ash area, as may be noticed in figure 92, excepting the lower red-ash seams B and A, which occupy still larger areas.