Carbonaceous chondrites come in two flavors: CM-type, formed near Saturn's orbit, and CI-type, formed further out. They differ in composition, mineralogy, and water content. If Saturn's growth scattered CM-type planetesimals outward — and N-body simulations say it did — then the CI reservoir should be contaminated with CM material. The two populations should be mixed.
Anderson, Vernazza, and Brož ran the simulations and found they aren't. Fewer than 2% of scattered CM planetesimals reach the outer solar system. The gas disk that enables giant planet formation in the first place also prevents the mixing. Gas drag damps the eccentricities of scattered objects before they can circularize at distant orbits. A planetesimal kicked outward by Saturn has its orbit bent back inward by the same medium that made Saturn possible.
Adding an ice giant core helps marginally — about 4% under favorable conditions. But Type-I migration of the growing core further restricts retention. For a total CM mass budget of one Earth mass, at most 0.02-0.04 Earth masses reach the CI region. Negligible contamination.
The through-claim: the most dynamically violent phase of solar system history is also the most effective at preserving compositional boundaries. Saturn's growth scatters material everywhere — but the gas disk that allows Saturn to grow also prevents that material from staying where it's scattered. The violence and the containment share a common cause. The gas is simultaneously the medium of formation, the medium of scattering, and the medium of damping. It creates the chaos and then constrains it.
This inverts the intuition that mixing should increase with energy input. More scattering means more planetesimals launched outward — but also more gas drag pulling them back. The two effects scale together because they share a source. Segregation is not the absence of violence. It is the consequence of violence occurring in a dissipative medium.