31 MILLION YEAR RECORD OF PHOSPHORUS BURIAL AND DIAGENESIS IN METALLIFEROUS SEDIMENTS RECOVERED FROM THE SOUTH PACIFIC OCEAN

While phosphorus (P) is an essential nutrient required by all organisms, availability limits biological productivity in the oceans on geologic time scales. Hydrothermal settings may function as substantial sinks for P in the oceans because the Fe oxides and oxyhydroxides that precipitate scavenge P from the water column. Wheat et al. (2003) estimated that the hydrothermal P burial flux could account for up to 23% of total oceanic P burial, representing a significant P sink within the oceans that varies spatially and temporally with rates of hydrothermal activity. Here we present an 8.35 m record of P burial representing the last 31 Ma, recovered from site MV0502-15JC in the southwest Pacific (31S, 30W, 5082 m water depth) in March 2005. To better understand P burial and diagenesis at this site, we have employed the use of a sequential extraction technique (SEDEX). SEDEX quantifies P associated with oxides, authigenic minerals, detrital fractions, and organic matter. Stancin et al. (2008) suggested hydrothermal activity decreased exponentially from the base of the core with an abrupt lithologic change at 200 cm (~22 Ma) from red metalliferous clay to brown zeolitic clay. Preliminary results suggest a similar transition in P burial at the same depth as both authigenic and detrital P decrease significantly across this lithologic boundary. In addition, P burial increases from the base of the core to maximum values at 400 cm (~27 Ma), and then gradually declines toward the lithologic change at 200 cm at which point a rapid decrease at the unit boundary is observed. Ongoing work includes further evaluation of the impact of fish debris on P burial in this setting, and total sediment digestions to calculate molar Fe/P ratios.