EFFECT OF INFLATING PLASMA BUBBLE DURING AN IMPACT CRATERING ON ROCK MAGNETISM

The shock exposure of the Santa Fe’s impact structure in New Mexico is evidenced by large human-size shatter cones. A new magnetic mechanism allows a magnetic detection of plasma’s presence during the impact processes. Rock fragments from the impactites were once magnetized by a geomagnetic field. Magnetic level of remanence revealed more than an order of magnitude lower magnetizations in the rocks that were exposed to the shockwave. A newly proposed mechanism is that the shock wave perturbation of magnetic stability plays in accord with the plasma magnetic shielding. This interplay of the two impact related processes allows keeping the magnetic grains in a superparamagnetic-like state shortly after the shock’s exposure, and leaves the individual magnetized grains in random orientations, significantly lowering the overall magnetic intensity. This clarifies how an impact process allows for a reduction of magnetic paleointensity and inspires a new direction of effort to study impact sites, using paleointensity reduction as a new impact proxy.