A major change in the ocean’s nutrient cycling in the late Miocene

Abstract:

The late Miocene epoch (roughly 7 million years ago) witnessed dramatic changes in the Earth system including the evolution and expansion of C4 plants in terrestrial ecosystems, global cooling and aridification of Africa and Asia, and an increase in the ocean’s productivity. It was hypothesized that the expansion of C4 plants on land and corresponding landscape changes triggered an increase in the delivery of nutrient-rich soil organic matter to the oceans, which might be responsible for the observed environmental changes in late Miocene time. Here, we present evidence for a major increase in the ocean’s nutrient content in the late Miocene, mainly based on the phosphorus and iron content of hydrothermal sediments from the deep South Pacific Ocean. A rise in the ocean’s nutrient content would have caused an increase in marine primary productivity and a sequestration of CO₂ from the atmosphere into the deep ocean, initiating the global cooling and other observed environmental and evolutionary changes during this interval.