The Impact-Sintered Mantle Replay (ISMR): A Unified Geodynamic Framework Linking the Chicxulub Hypervelocity Event to True Polar Wander, 670 km Conduit Shear, and the ~50 Ma Global Seamount Bends

The simultaneous directional shift across Earth's major mantle hotspot chains—most prominently the Hawaiian-Emperor (~47–50 Ma), Louisville (~50 Ma), and Réunion (~48–50 Ma) seamount tracks—represents one of the most significant, coeval geodynamic events in the Cenozoic record. Traditional plate tectonic models attribute this global phenomenon to simultaneous, local plate-boundary reorganizations, yet struggle to account for the spatial synchrony across opposing hemispheric plates, the ~16-million-year lag following the Cretaceous-Paleogene (K-Pg) boundary, and associated pulses of primitive mantle outgassing. Here, we present the Impact-Sintered Mantle Replay (ISMR) model: a unified geodynamic framework demonstrating that the oblique hypervelocity impact at Chicxulub (~66.04 Ma) delivered 10^24 to 10^25 J of total kinetic energy, coupling ~10^22 to 10^23 J of horizontal mechanical work tangentially upon the lithosphere across a transiently fluidized asthenosphere (eff/0 ≈ 10^-3). This impulse initiated a ~12° to 18° True Polar Wander (TPW) displacement around a North Pacific Euler Pole (55°N, 140°W). This rapid lateral displacement generated intense horizontal shear across the 670 km mantle transition zone, where a two-order-of-magnitude viscosity contrast severed upwelling lower-mantle plume stems under a shear stress of 3.37 MPa, exceeding the yield limit of bridgmanite assemblies. Utilizing standard thermal diapir upwelling equations (v ≈ 4.52 cm/yr across 570 km of upper mantle), we demonstrate that the severed diapiric heads required 13.5 to 16.0 million years to traverse the upper mantle. Re-emerging simultaneously at ~50 Ma along new lithospheric motion vectors, these primitive, un-degassed diapirs generated the observed global seamount bends, elevated 3He/4He isotopic ratios (>20 R/RA), unradiogenic osmium signatures (gamma_Os < 0), and the massive mantle carbon outgassing driving the Early Eocene Climatic Optimum (EECO).