A stratigraphic section of Ordovicianlimestone exposed in central Tennessee, U.S. The less-resistant and thinner beds are composed of shale. The vertical lines are drill holes for explosives used during road construction
A rhythmite is layers of sediment or sedimentary rock laid down in a repeated pattern. This pattern may be varves, which are an annual pattern, or shorter or longer-term rhymites. Tides in some places have left rhythmites.view more...