Abstract:
Eocene/Oligocene boundary paleoproductivity data from Ceara Rise,
Ocean Drilling Program Site 925: 4 12.25 N, 43 29 W, 3040m depth.
ABSTRACT (from the online documentation)
Paleoproductivity, nutrient burial and carbon cycling were
investigated across the Eocene/Oligocene (E/O) boundary (begin-end;
36.9 - 32.7 Ma at ~40-kyr resolution, timescale of Shackleton et
al. [1999]) at Ocean Drilling
... Program (ODP) Site 925 on the Ceara Rise
in the western equatorial Atlantic (3040 m present water depth; 748.26
- 850.70 mbsf). Downcore bulk sediment records of biogenic barium,
total reactive phosphorus, biogenic silica and calcium carbonate are
interpreted to represent export production, net nutrient burial,
biogenic opal production and inorganic carbon burial, respectively.
The global positive excursion in d13C subsequent to the E/O boundary
is recorded at Site 925. Export production appears to have been
externally forced by orbital parameters at eccentricity frequencies
during the study interval, based on spectral analysis of the biogenic
barium and reactive phosphorus records. Biogenic silica production or
preservation increased after the Eocene/Oligocene boundary to a higher
baseline, although overall productivity and nutrient burial did not
increase based on barium and reactive phosphorus records. Thus,
although absolute production did not increase at this site, a shift in
relative abundance of siliceous vs. carbonate productivity may have
resulted in a change in relative organic carbon burial. This may have
contributed to the positive excursion in global oceanic d13C
subsequent to the Eocene/ Oligocene boundary, although the silica
maximum persists after the carbon isotope excursion ends. 
