What do you see when you visit in Las Vegas?
A short drive northeast to Arrow Canyon reveals Pennsylvanian-age Bird Spring Formation. This exposure of bedded carbonates is in the east-dipping panel of a large anticline similar to those currently being explored in the Kurdish region of Iraq. The joints in this photo are perpendicular to bedding. Did they originally form vertically, prior to folding of the beds, then rotate to their current attitude? Or did they form normal to bedding after the anticline developed? Or something in-between? Notice that the distance between joints varies with bed thickness.