15 October 2011
This is a boulder of Cambrian-aged Flathead Sandstone, the unit overlying the Great Unconformity exposed in Wind River Canyon, Wyoming. Click to make it 5000 pixels wide. Swiss Army knife for scale. It shows a lovely example of multiple upside-down cross-beds. It also shows a heavy layer of caliche on what is (now) the upper surface – a phenomenon which typically occurs on the underside of sedimentary clasts. So not only was it deposited right-side-up, this boulder also sat out in this arid environment for some time in that same orientation to garner the layer of caliche, and then was flipped to its current orientation.