Rockyhock and Kimbel Carolina Bays: Extraterrestrial Impact or Terrestrial Genesis?

Evidence for the harsh climate prevalent during the Last Glacial Maximum (LGM) are seen in topographical features visible south of the ice sheet margin in the uplands and coastal regions of the southeastern United States. Among the features attributed to ice age climate are numerous elliptical, shallow depressions called collectively Carolina Bays, hypothesized to have been formed by “blow outs” of loose sediment by the strong, sustained winds and arid, cold climate characteristic of glacial epochs (Raisz, 1934, Johnson, 1942 and Kaczorowski, 1977). This view eclipsed the 1933 proposition by Melton and Schriever, and expanded by Prouty (1934, 1953), that extraterrestrial debris produced by an aerial meteorite or comet explosion in the vicinity of the Great Lakes during the late Pleistocene formed the bays. 12,900 years ago, post-LGM warming was interrupted by a return to a glacial climate that persisted for over 1,000 years. The events precipitating the cooling, known as the Younger Dryas (YD), are the subject of debate. Recently Firestone et. al. (2007) proposed that an impact in the Laurentide ice sheet by a fragmented comet might have simultaneously initiated the YD and formed the Carolina Bays. Carbon 14 dating and pollen analysis of core samples taken from Rockyhock Bay, in Chowan County, NC, by Whitehead (1980) indicate a pre-YD genesis. However, a number of the bays have been found to contain materiel associated with extraterrestrial impacts including carbon and magnetic spherules, glass-like carbon, charcoal and nanodiamonds (Firestone, et. al. 2007). The discoveries reinvigorated the debate over the bay’s origins. Were the bays created by an impact or were they merely receptacles for impact materiel injected into the environment. If created before the YD, the bays would have experienced episodic post-formation modification due to cold, dry, windy periods alternating with warm, moist and calmer climatic conditions. Carolina Bays would thus episodically fill with wind-blown or water-borne sediment or water. Some evidence of bay history should be evident in their stratigraphy. Rockyhock Bay’s proximity to ECSU motivated the attempt to establish a broad chrono-stratigraphic context to reveal whether Whitehead’s inferred bay-structure and age vs. depth correlation were mischaracterized. Core samples were taken from bay rim and center and a Ground Penetrating RADAR (GPR) survey was performed. Results will be compared with the cited earlier published results. Results will be compared to a similar survey performed for Kimbel Bay, near Fayetteville, NC, whose hydrologic history seems different than that of Rockyhock Bay.