(Figure 2, page 940) K-T boundary enrichment for cerium and iridium chemical composition of layers inside the ZETES-3D manganese nodule in the Pacific Ocean

Hydrogenous manganese nodules form on the ocean floor by slow authigenic precipitation (1-6 mm/Ma) of the oxyhydroxides of manganese and iron that continuously scavenge trace elements from the marine environment. Consequently, these nodules represent independent marine deposits useful for the study of the chemical signatures of the paleomarine environments. The results presented are a continuation of a study of the Zetes-3D nodule from the Pacific Ocean. It is a large (24x17x10 cm) hydrogenous nodule whose slow growth rate of 1.3 mm/Ma was detremined using 10Be techniques. A positive cerium anomaly is observed throughout the nodule and its Ir content indicates a sharp spike at 54-62 Ma in fair agreement with the K-T event.