Search for supernova-produced 60Fe in a marine sediment

An (60)Fe peak in a deep-sea FeMn crust has been interpreted as due to the signature left by the ejecta of a supernova explosion close to the solar system 2.8 +/- 0.4 Myr ago [Knie et al., Phys. Rev. Lett. 93, 171103 (2004)]. In an attempt to confirm this interpretation with better time resolution and obtain a more direct flux estimate, we measured (60)Fe concentrations along a dated marine sediment. We find no (60)Fe peak at the expected level from 1.7 to 3.2 Myr ago. Possible causes for the discrepancy are discussed.