CONTRACTION AT HAZLETON.
One of the most singular instances of inversion of strata, or the effects of contraction, is found at the bottom of the Diamond mines, Hazleton. The Hazleton basin contains an anticlinal running through its centre, and, at the western end, at least two of these axes. At the Diamond mines, near the town of Hazleton, this middle axis is inverted, as shown in figure 102. The "Big Vein" is folded back over the north dip, so that the bottom slate of the first north dip becomes the top slate of the second north dip (really a south dip of the central axis), but passing over the sharp, inverted point of the axis or saddle, the second true north dip assumes its proper position and condition. This sharp folding of the strata in the Hazleton basin takes place at a depth of 900 feet vertical, where the breadth of the basin is 2600 feet between the outcrops of the lainmotil, and where the general dip of the measures is between 35° and 40°.
It is very evident that such could not have been the normal condition of the bed, since no sedimentary strata could have been formed in this inverted manner. It must, therefore, have resulted from subsequent causes;
and since we can find no cause so probable as the natural and irresistible forces of contraction, we conclude such to have been the power which has contorted and crushed not only the anthracite coal measures, but the long, parallel waves of inverted strata in which these measures exist, from the Blue Ridge to the Alleghanies.
Though the instance we have given in figure 102 is peculiar, it is not entirely singular; other instances of the same kind may be given; but we have selected the various forms of contracted strata in order to illustrate the subject fully, and as shown in our numerous sections.
Figure 70, representing this peculiarity in the Tamaqua Shaft colliery, is the nearest approach that we have given to the inversion displayed in figure 102.