Re-assessing copper and nickel enrichments as paleo-productivity proxies

Copper (Cu) and nickel (Ni) are elements frequently enriched in sedimentary deposits rich organic matter (OM). In the marine environment, they mainly supplied to sediments association with OM (organo-metal complexes). modern environments, a good correlation between intensity of phytoplankton productivity quantities Cu Ni transferred made it possible establish paleo-productivity calculations based on contents ancient these two metals. The present study is re-evaluation significance that can be attributed metals as proxies. approach adopted here examination large database already available scientific literature. choice was favor amount data by simple means: comparisons total carbon (TOC) content, enrichment (or even other trace metals), value Fe:Al ratio makes assess availability reactive iron. basic idea number geological formations encompass all kinds paleo-environmental settings, thus comprising an extreme range factors conventionally involved mechanisms accumulation OM. aim identify strong trends, valid paleo-situations, which will have carefully taken into account future detailed reconstructions. It emerges from this that, many cases, cannot considered faithfully reflecting quantity initially deposited. Several acting loss identified, among them, (1) rapid linked decomposition before conditions conducive sulfate-reduction set in; (2) low abundance iron limits pyrite liable form, significantly hampers fixation sediments. If not reliably retained sediments, is, proportional sediment, reconstitutions involving concentrations may provide underestimated values paleoproductivity. An interesting clue quickly know whether enrichments likely “abnormally” low.