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
Abstract
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.