OBSERVATIONS CONCERNING THE POSSIBLE ORIGIN OF BARFIELD BAY: IS THERE EVIDENCE OF AN IMPACT EVENT?

Others have compared Barfield Bay, southwest Florida, to elliptical, sand-rimmed depressions called Carolina Bays. Barfield Bay is similar in size to larger Carolina Bays. Its high sand rim surrounds 88% of its perimeter, and its long axis points S 15°E subparallel to the dominant orientation of southern Carolina Bays. Most believe that rims of Carolina Bays are dominantly aeolian and our observations support an aeolian origin for the Barfield Bay rim. However, some favor an extraterrestrial impact origin for Carolina Bays. Firestone, et al. (2007) reported impact indicators including magnetic spherules and iridium content above background in a number of Carolina Bays as well as distinctive carbon spherules attributed to intense biomass burning. They noted that these features are shared with Younger Dryas (YD) Event beds which they attribute to continent-wide effects of an extraterrestrial impact over the Laurentide Ice Sheet. Although aware of evidence that some Carolina Bays are not of YD age, they believed their observations linking Carolina Bays to YD Event beds to be significant. To our knowledge no one has formerly proposed that Barfield Bay is an impact structure, but we are aware of informal speculation to that effect. We carried out a first-pass test for possible impact criteria by examining auger and vibracore samples of the Barfield Bay sand rim for magnetic and carbon spherules. In our samples paramagnetic grain content ranged from 0.2 to 1.2 g/kg, comparable to the low range for Carolina Bays. The Barfield Bay paramagnetic grains are mineralogically diverse and subrounded suggesting a detrital origin. We found no magnetic spherules of possible cosmic origin. Water floatation concentrated none of the distinctive carbon spherules or glassy carbon that might suggest unusually intense biomass burning. In our opinion, these negative results do not encourage more expensive geochemical tests for an impact origin of Barfield Bay.