Copper and copper(II) porphyrins of the Cretaceous–Tertiary boundary at Stevns Klint (Denmark)

High levels of copper(II) (Cu2+) were found with the major part (>90%) of the total Cu located in the smectite (Cu: 175 ppm) and kerogen (Cu: up to 1000 ppm) of the basal black marl of the Cretaceous–Tertiary (KT) boundary informal type sedimentary rock: the Fish Clay at Stevns Klint, Denmark. Anomalous abundance (4000 ppm) of the kerogen Cu2+-porphyrins in this marl was detected by electron spin resonance. A model is proposed in which the enormous acid rains (caused by the KT asteroid impact) washed out the humics (already enriched with Cu2+/Cu2+-porphyrins) of the top horizon of the nearby oxic soil into the Fish Clay Basin during the KT event.