AN INCOMPREHENSIBLE COSMIC IMPACT AT THE MID PLEISTOCENE TRANSITION; SEARCHING FOR THE MISSING CRATER USING AUSTRALASIAN TEKTITE SUBORBITAL ANALYSIS AND CAROLINA BAYS' MAJOR AXES TRIANGULATION

Australasian (AA) tektites are distal ejecta of a cosmic impact into terrestrial sediments 788.1 ± 2.8 ka. Protracted explorations within the strewn field, as preferred by consensus opinion, have yielded neither an astrobleme nor a proximal imprint. In 3 lesser strewn fields correlated with progenitor astroblemes, tektites are strewn asymmetrically and their total masses and minimum loft distances scale with projectile kinetic energy (KE) partitioning yield. Pursuing an a priori astrobleme location within the uniquely expansive AA strewn field ignores such findings. Absent identification of proximal ejecta in the strewn field, workers are now inferring that indochinite tektites are proximal, dismissing their known devolatilization, weightless vacuum quench and their carefully derived re-entry speeds, ≥ 80% of Earth escape. A defendable guess 40 years ago, but promoting an a priori astrobleme in Indochina is now impeding progress.

Ironically, a cosmic link to the Carolina bays' genesis is considered soundly falsified by the same absence of a correlated astrobleme. We have measured ~50,000 of these shallow, oriented, ovoid basins, located around an annulus focused on Saginaw Bay, Michigan. We posit the ovoid planforms to be surficial manifestations of cavitation voids within an incomprehensible geophysical mass flow of volatiles and entrained target clastics.

Unifying both missing astroblemes, we propose an incomprehensible cosmic event on a hemisphere diametrically opposed to the AA distal tektite strewn field. We invoke a highly oblique, perhaps tangential, hypervelocity projectile ricocheting off the Earth’s limb along an extended footprint. Sub-horizontal shock to thick MIS 20 ice sheet overburden triggered endogenic comminution, as stored pressure potential within the substrate was released by phase change of pore water to steam, provisioning fluidized medial ejecta outflow for Carolina bay emplacement. Shocked ice plume expansion augmented tektite velocities, and dissipated significant partitioned KE, preventing another Chicxulub-style global conflagration. The KE partitioning process conspired with intervening ice age transgressions to dislocate proximal ejecta and obfuscate the cosmic signature.

AA tektite Suborbital Analysis with appropriate dynamical accounting supports a putative antipodal Saginaw impact site, as does a recent EIGEN 6C4 gravity field assessment. The hypothesis would be falsified if 26Al/10Be burial dating of terraces under Carolina bays disallows bay deposition circa 788 ka.

.