  We summarize recent results assessing the carbon and silicon abundances of
the intergalactic medium (IGM) using the `pixel optical depth' technique. We
briefly discuss the implications of these results for models of intergalactic
enrichment, focusing on distinguishing `early' z >> 4 enrichment by the first
generations of stars and objects from `late' enrichment by 2 < z < 5 Ly-break
galaxies. We then discuss the comparison of observed QSO spectra to simulated
spectra generated from cosmological simulations that self-consistently include
enrichment, and draw qualitative implications for the general picture of
intergalactic enrichment at z > 2.
