Observations of galaxies and star-forming regions suggest a metallicity floor: a lower bound on gas and stellar metallicities at a few thousandths to a few percent of solar that is rarely undercut, even in very low-mass systems and at high redshift (Kunth & Östlin 2000; Wise 2012; Jaacks 2018). ΛCDM simulations must impose a metallicity floor by hand to avoid forming unrealistically metal-free Population III stars that no observation has confirmed.
The standard model assumes the universe started from primordial BBN composition (H + He + Li-7 traces) with metals produced exclusively by stellar nucleosynthesis. Population III stars formed from pristine gas should leave detectable metallicity signatures below the observed floor. The absence of truly metal-free stars demands either widespread Pop III enrichment that uniformly raises the floor, or modifications to the stellar IMF, neither of which is parsimonious.
SCT replaces the hot-dense-center with a superluminal collision and the thermalized debris field. From this single change, the metallicity floor is the predicted in-cycle nucleosynthesis signature from cascade-seeded SMBH plus accelerated Population III stellar populations. The cascade-thermalized plasma cooled through standard BBN to primordial composition (P40, P42), but cascade-seeded structure (P22, P25) gave the proto-galactic gas reservoirs at very high density already at cascade-end, allowing rapid Pop III star formation in cascade-stream regions immediately after recombination.
Cascade-seeded SMBH seeds (P46) provided early AGN nucleosynthesis from accreting cascade-stream matter, contributing to the metal floor through high-energy nucleosynthetic channels accessible at the QCD-and-above accretion-disk temperatures around 10⁷ to 10⁹ M☉ SMBHs. Multi-stage cascade dynamics (P34, P36) sets the cosmic-web filament infrastructure where this rapid early enrichment occurs. The combination of cascade-seeded high-density gas plus cascade-seeded SMBH AGN activity produces the metallicity floor at greater than 10⁻⁴ Z☉ in our cosmic cycle, before the first observable stellar populations form on the post-floor enriched gas.
The metals are NOT inherited from prior cycles (the cascade-thermalization scale of T_QCD ≈ 10¹² K erases prior nuclei structure). Pre-existing matter (P25) supplies the baryon budget but not the metallicity. Standard BBN (P42) reproduces the primordial composition correctly. The metallicity floor is therefore an in-cycle product of cascade-seeded structure formation. The same M11 + M1 framework that resolves the JADES-GS-z14-0 oxygen abundance (recid 113) and the broader early-galaxy chemical evolution accounts for the floor.
Detection of truly metal-free Population III stars at greater than 5σ (with metallicity below 10⁻⁶ Z☉) would refute the in-cycle cascade-seeded floor, demonstrating that cascade-seeded enrichment did not uniformly process the observable cosmic gas. Equivalently, finding the floor at substantially below the predicted > 10⁻⁴ Z☉ level would indicate cascade-seeded enrichment is less efficient than M11 expects.