Fossilized Sand Ripples

As I was photographing the rapids and falls at Falls Park in Sioux Falls, SD, I came across this striking and beautiful example of fossilized sand ripples in the Sioux quartzite.

This wonderful stone is among the oldest rock in North America. It started out as sandstone and was gradually turned into quartzite. Much of what is now exposed across eastern South Dakota and western Minnesota was uncovered by the last glaciers in the region.

Normally this particular example would be difficult to reach or see as the Big Sioux River covers the riverbed around it. The river was low and I was able to walk out onto the dry riverbed and spotted this. It is incredible to think that this was already in existence millions of years before the dinosaurs!