 photo credit: Craig Chesek, © American Museum of Natural History The surface of this sandstone from Elliot Lake, Ontario, Canada indicates the depositional environment in which the rock was formed. The wavy texture on the surface is called "ripple marks" and they indicate that the sandstone was deposited in a shallow marine environment where the ebb and flow of the tide sculpted the shallow sea floor. This rock tells us that this part of North America was submerged by a shallow sea [1.8] billion years ago. | 
