Summary

The Carolina Bay Survey has revealed shallow ovoid basins arrayed along an annulus around the Great Lakes, USA, with their major axis documenting a radial distribution from that area. Bay landforms are unlikely to be primary or secondary impact craters because of their shallow depth. We propose they were formed as voids in an ejecta blanket during a mass geophysical flow of pulverized sedimentary strata, where their primary axis documents the ejecta’s arrival vectors. Rather than being “wispy ephemeral” landforms, bay survival in hostile conditions supports a finding that they are very robust landforms, perhaps as a result of their high-energy emplacement. Our working hypothesis holds that a cosmic impact event occurred at the MPT. In the depths of MIS-20, the target in Michigan was encased in a ~2 km-thick Laurentian glacial ice sheet, providing a low-impedance shield [24] over the target sediments. Ironically, the “Australasian tektites” are considered by scientists to be ejecta from a cosmic impact, despite the failure to locate the impact site. We suggest the two events are the result of a single cosmic impact at 785 ka ±5 k. Future research goals include application of 26Al-10Be isotopic burial dating techniques to the surfaces beneath these landforms [6]. Samples of sandstones and shales from the Lower Michigan Peninsula have been collected for chemical and isotopic analysis, and will be compared with results of similar analysis on Carolina bay rim deposits and Australasian tektites.