THE WOODBURY-MANCHESTER IMPACT STRUCTURE IN SOUTHEASTERN NORTH AMERICA: IMPLICATIONS FOR THE EARLY NEOPROTEROZOIC EARTH-MOON ASTEROID/COMET SHOWER AND SNOWBALL EARTH
Field and petrographic analyses of quartzite ridges that extend medially through the region of melt rocks have identified shatter cones, shatter cleavages, feather features, planar fracturing, and injected shear melts that occur in a map pattern that suggests that the ridges were uplifted in response to a very low-angle collision or successive closely-spaced impacts. The structure, including the medial ridge complex, is similar in size and morphology to the lunar crater Schiller and the Martian crater Hale, which have been argued to have formed by similar processes. The minimum size of the impacting body is calculated to be about 25 kilometers. The structure likely was preserved mostly intact beneath the Appalachian detachment and has been exhumed since the end of the Paleozoic.
Arnscheidt and Rothman (Proc. Royal Soc. A, 2020) showed that Earth's decline into Cryogenian cooling most likely was formed by a sudden dramatic reduction in solar insolation. Therefore, they postulate a volcanic trigger for the last Snowball Earth. Alternatively, we propose that the WMIS (especially if it represents a large low-angle oblique strike), in connection with the expected increase in interplanetary dust during an asteroid or comet storm (including the contribution from successive large lunar impacts), could be capable of starting the collapse.