The unconsolidated sand of the Carolina Sandhills is mapped as the
Quaternary Pinehurst Formation, and is interpreted as eolian (wind-blown) sand sheets and dunes that were mobilized episodically from approximately 75,000 to 6,000 years ago. Most of the published
luminescence ages from the sand are coincident with the last
glaciation, a time when the southeastern United States was characterized by colder air temperatures, stronger winds, and less vegetation. The Carolina Sandhills region also contains
outcrops of
Cretaceous-age (~100 million years old) strata of sand, sandstone, and clay that are interpreted as fluvial (river) deposits. These Cretaceous strata are thought to be the source of the sand of the Pinehurst Formation. In South Carolina and North Carolina, these Cretaceous strata are mapped as the Middendorf Formation. A notable hill of these Cretaceous strata is
Sugarloaf Mountain in the Sand Hills State Forest in Chesterfield County, South Carolina. ==Soils==