Productivity and redox proxies of palaeo-oceans: An overview of elementary geochemistry

It is important for the study of palaeo-oceanography and palaeoclimatology to estimate the primary productivity in surface water and redox conditions in water columns. The study of primary productivity and redox conditions is usually carried out with the aid of elementary geochemistry. Since the availability of nutrients is the main limiting factor to planktonic productivity, the contents of bio-limiting nutrient elements(such as Fe and Si) and micro-nutrient elements(such as Cu, Ni and Zn) reflect the level of primary productivity. Ba and Mo which accumulate with the falling of organic matter setting are related to the organic-carbon flux. Therefore, Ba and Mo can also be used as primary productivity proxies. As for the redox-sensitive trace metal elements(such as Cr, V and U), their contents and elementary radios(such as V/(V + Ni), V/Cr, U/Th and V/Sc) can be usually used to reconstruct the redox conditions in water columns.