THE CAROLINA BAYS

RESEARCH IMPLICATIONS OF A COMETARY MODEL

We have eliminated all but one of the extraterrestrial Carolina Bay forming possibilities on the basis of availability, orbital characteristics, physical attributes, and impact morphometry. We further refined the remaining possibility by suggesting that a bay forming comet did not need to be large to form half a million bays. However, it must have been volatile; it must have followed a flat northwest trajectory because rims are better developed in the southeast quadrant, and it must have been fragmented somewhere to the northwest and eventually explode near the surface but in the atmosphere. The physics of such a series of catastrophic atmospheric explosions added to impact velocities at possibly greater than 51 km/sec are very complex. To the best of our knowledge no one has speculated about the nature of, or the bay forming energies available with, such shock waves. Nor since 1936 (MacCarthy) has anyone speculated about the relationship between shock waves and Carolina Bay morphology. These two avenues of research are needed before a cometary bay forming mechanism could be widely accepted.

As happened when aerial photographs of Carolina Bays were first seen (Melton and Schriever, 1933), we were immediately struck by the too remarkable regularity and uniformity with which bay morphology repeated itself. As physical geographers we doubted that either simple or complex sets of terrestrial mechanisms could conspire to create exceedingly regular forms on one portion of the Atlantic Coastal Plain without forming similar and equally widespread features elsewhere in similar coastal environments. It seemed to us that either the area is unique or the causal mechanism is not terrestrial. Furthermore, if the cause is not terrestrial, it almost certainly was a comet. Neither the impact of a large asteroid nor the splash effects of a meteoritic shower could form Carolina Bays. This section, then, represents pure speculation about some of the terrestrial constraints concerned with such a unique event and suggests possible directions whereby this model can be tested.

If Carolina Bays represent residual scars of a truly singular extraterrestrial event, the bays must be young--an attribute accepted by many terrestrial theorists as well. For example, Price (1968) indicated one or more periods of late Pleistocene bay development, whereas Thom (1970) indicated either a Farmdalian (28,000 - 22,000 B.P.) or a Woodfordian (22,000 - 12,500 B.P.) age. Age is a more critical factor when an extraterrestrial mechanism is invoked. Bays formed virtually instantaneously by explosions of cometary fragments are residual features. Subsequent modifications of such scars by normal terrestrial processes would rapidly obliterate all traces in unconsolidated sediments such as the Coastal Plain. Study of bays in Figure 2 suggests that bays remain quite distinct, essentially unaltered except for infilling; thus, the bays must be quite young--either late Wisconsinan or early Holocene.

Very few samples of buried peat in the bays have been dated. Thom (1970) had a 6600 B.P. radiocarbon date from the basal peat in one South Carolina bay although he cited a greater than 38,000 B.P. date from the basal peat in a North Carolina bay. It is difficult to equate the two results. The bays may be Wisconsinan in age. On the other hand, anomalous dates do occur, so little reliance can be placed on the few dates which have been acquired. Sequential samples along a vertical profile in several bays need to be dated and at least one date from the basal organic fill in a large sample of bays should be taken. Such a dating program will permit the Carolina Bays to be more precisely defined in time, and, more particularly, may indicate the possibility of simultaneous origin.