Weird Fault

Just below the dark coal the hard layer of sandstone has been offset by about several feet of overlap. Running diagonally down to the left from this area of overlap is what appears to be the track of a reverse fault. As I interpret the evidence, it seems that as the rocks were being subjected to intense compressive forces they began to buckle into a downward fold forming the Sideling Hill syncline. As the rocks were bent, different layers began to slip past each other (just as the pages of a thick phone book will slip past each other if the book is folded). The more ductile coal and shales could deform fairly easily, however, the more resistant rocks like this thin hard sandstone must have developed a severe kink that eventually ruptured. (Imagine a piece of stiff shirt cardboard inserted between the pages of the aforementioned phone book.) The really unusual aspect of the rock is the fact that the sandstone layer overlapped with the right-hand part on top of the left-hand part, yet below it the rocks on the left appear to have been thrust up and to the right on a diagonal line in what I would call an intraformational reverse fault that absorbed some of the compression. This causes some interesting and anomalous geometry in the rocks. While in the process of creating the overlap a portion of the ductile coal that normally lies above the sandstone layer looks to have been forced into a pocket below and to the right of the overlap.

Done