Paleoproductivity of the Indian Ocean during the Tertiary Period

Abstract

Studies of oceanic paleoproductivity have lagged in part because of the absence of a suitable proxy for measuring paleoproductivity. A transfer function has recently been proposed which directly translates carbonate mass accumulation rates into a quantitative measure of productivity. This transfer function ha been applied at six ODP sites in the Indian Ocean in order to investigate temporal and spatial changes in Indian Ocean productivity during the Tertiary Period. Early Paleogene productivity in the Indian Ocean was considerably higher than in the late Paleogene and Neogene. A warmer, more confined sea, with large riverine nutrient input from close lying land masses may account for the generally higher early Paleogene productivity. Productivity increased dramatically at two times during the Paleogene: during early Paleocene calcareous nannofossil Zone NP5 and during early Eocene Zone NP11. These productivity increases may be related to abrupt climatic changes which reorganized oceanic circulation and stimulated major changes in productivity. Productivity began to fall in the Oligocene as a result of global cooling and the initiation of the modern Indian Ocean circulation system. This trend continued into the Neogene, which was characterized by generally low productivity, interspersed with occasionally higher levels, especially at the more northern sites in the Indian Ocean.