Carbon and nitrogen provide a chemical and isotopic record of the immediate environmental effects of the terminal Cretaceous impact. At Woodside Creek, New Zealand, kerogen carbon is enriched 15-fold, and total sediment nitrogen 20-fold in the basal layer of the boundary clay. Both elements show marked changes in their isotopic compositions on a millimeter scale, which may reflect the rapid sweep-out of plankton by ejecta fallout. The enrichment of nitrogen may reflect a contribution of HNO₃ acid rain from a shock-induced combination of N₂ and O₂, but would not be expected from volcanism.

Ground truth for such sudden fallout on the oceans is obtained from the 9-cm-thick Toba ash layer in the Indian Ocean. The accumulation rates of organic carbon and carbonate rise by ~3 orders of magnitude at the base of the ash layer, but then drop by 1 to 4 orders of magnitude after 3 to 4 cm. Apparently 3 to 4 g/cm² of the Toba ash efficiently scavenged and buried virtually all the CaCO₃ and much of the particulate organic material in the ocean up to 2,000 km from the site of the eruption. Presumably the 2 to 5 g/cm² of Cretaceous/Tertiary (K/T) ejecta were no less efficient, in view of their much finer grain size. It is significant that the amounts of marine and land biomass at the K/T boundary are approximately equal to the steady-state global inventory (one generation), as are the amounts of other enriched terrestrial elements (As, Sb, Zn). This is expected in a catastrophic but not a gradualist scenario.