Here is a scene of some older, high elevation Carolina Bays near my parents house which is in the middle of a dense concentration of the structures. They formed high sandy rims which have been modified some by (cold dry glacial) wind to form secondary dunes roughly parallel to the crescent shaped bay rims—they look like eyebrows to me. Younger and lower elevation bays occasionally have eye brow dunes but not as frequently as these older bays. The high ground is the sand hills (cretaceous marine sediments about 80 million years old) with 200 to 300 feet of relief. Pinehurst in is the sand hills. I used 20X vertical exaggeration to accuentuate the bay rims so the hills are pumped up. The flat ground that the bays formed on used to be sand hills but was leveled by a Pleistocene sea level highstand about 2 million years ago which created the Orangeburg Scarp, visible in this image. There is a pile of beach front sand in the middle of the scene which James Conely calls the Pinehurst Formation. So the oldest of Carolina Bays are still young.