New and Ancient Ripple Marks
May 12, 2003
On the photo at left, a brisk onshore breeze, blowing across a shallow tidal pool, created the long, parallel sets of asymmetrical ripple marks on a beach in Maine. This photo was taken in August of 2002 by Chris Kluge. Modern ripple marks provide clues to what the environment may have been like eons ago. On the photo at right, taken earlier this month, west of Denver, Colorado, ripples preserved in ancient sandstones (estimated to be 130 million years old) bear a remarkable similarity to those found on modern beaches. This area was once the shore of a vast sea -- ripples in the sands of that shoreline were preserved in the South Platte Formation of the Dakota Group. Today, those fossil ripple marks are exposed on the steeply dipping, eastern flank of Dinosaur Ridge near Morrison, Colorado. These Cretaceous sandstones also contain several very clear theropod and ornithopod dinosaur track-ways.