MARLIN RISE: A 20 MA RECORD OF DUST INPUTS TO THE SOUTH PACIFIC OCEAN

In order to better understand potential future climate changes, it is imperative to understand past climate variability, for example, rates of weathering and erosion and changes in atmospheric and oceanic circulation. These factors play an important role in dust systematics which provide trace nutrients to the open ocean. Trace nutrients, such as iron, frequently limit primary productivity in vast areas of the open ocean, and dust fluxes are thought to be the primary supply of new iron to the oceans. Since dust supply to the ocean is controlled by wind speed and strength, dust accumulation in ocean sediments may help to reconstruct paleo-wind patterns. For these reasons, elemental records from ocean sediments may provide useful information about ocean responses to past climate changes, including variability in provenance and nutrient fluxes. Bulk sediment geochemistry from a 17 meter long core (MV0502-1JC) recovered from Marlin Rise in the south Pacific (40S, 154W) provides a record of paleo-iron and phosphorus (an important macro-nutrient) burial over the last 20Ma. The Marlin Rise core is characterized by low sedimentation rates and predominantly red-clay sediments. Preliminary results illustrate temporal variability in nutrient and terrigenous elements. P concentrations average 35 µmol/g for the top 400 cm (~5 Ma), while larger amplitude variability and higher average concentrations are observed below 400 cm. Fe concentrations oscillate around an average of ~140 µmol/g for the entire core. Al/Ti ratios average 21 g/g; however, maximum values agree with average continental crust and minimum values are similar to ocean crust values, suggesting there has been significant variability in provenance.