NEBRASKA'S CAROLINA BAYS

The Carolina Bays of the Atlantic Coastal Plain are one of the more enigmatic geomorphological features in North America. These elliptical depressions occur in a variety of sizes, are oriented NW-SE, and have rims most visible on the southeast edge. They have often inspired flights of fancy as scientists and the public have sought ways to explain them. Part of the fascination stems from the perception that they are unique to the Coastal Plain. South of the Platte River in east central Nebraska, USGS DOQs reveal a multitude of oval shaped features that share SW-NE orientation. They occur in a variety of sizes and have rims on the southeast edge. Locally they are called Rainwater Basins. Bays occur in Coastal Plain sandy sediments; however, the Basins of Nebraska occur in a loess-mantled landscape. Orientation of Bays and Basins is opposite, but both are perpendicular to regional prevailing wind directions. Prior work of Kuzila suggested that the Nebraska Basins exist where a loess dated at ~27000 radiocarbon years before present provides a pre-existing topography. Soil survey maps of the area show that some rims of the Basins are sandy. Cores from the area indicate that a sandy landscape was buried by loess. Upper parts of these sandy deposits are well sorted; fluvial sands and gravels occur below these sorted sands. Using coring and OSL dating we are currently documenting the age of this sandy surface. Our hypothesis is that the Basins on the current land surface originally formed as blowouts or low spots in abandoned Platte River fluvial sands and gravels. The ~27000 radiocarbon years and later loess actually draped a pre-existing topography formed in these sands. We also offer that these features would be recognized as an analog of the Carolina Bays if not for their loess cover. This suggests that Carolina Bays are not unique features, and any explanation for their existence should also help explain Nebraska's Rainwater Basins.