Nutrient Trace Element Cycles in the Phanerozoic Ocean

Cycles of nutrient trace elements in the Phanerozoic ocean

Authors:

Large et al

Abstract:

Availability of nutrients in the ocean can be a major factor affecting bioproductivity, burial of carbon and release of oxygen. However, the nutrient trace element (TE) composition of the paleo-ocean cannot be measured directly. Here we present a comprehensive global dataset on the TE content of marine sedimentary pyrite in black shales, dating back 700 million years, and demonstrate a systematic cyclic evolution of pyrite TE composition with time. The nutrient TE, molybdenum, selenium, cadmium and thallium measured in pyrite, and phosphorus measured on whole rock, rise sharply at 560 to 550 Ma followed by several cycles of TE variation through the Paleozoic and into the Mesozoic. A number of factors could explain the trends. We suggest that variations in continental uplift, erosion and nutrient flux rates were possible drivers of the oceanic nutrient cycles. The cyclic patterns through the Phanerozoic suggest periods of nutrient-rich oceans, followed by nutrient-poor oceans that encompass several major mass extinction events.