| Summary: | Biogenic components of sediment accumulated at high rates beneath frontal zones of the Indian and Pacific oceans during the late Miocene and early Pliocene. The δ<sup>13</sup>C of bulk and foraminiferal carbonate also decreased during this time interval. Although the two observations may be causally linked, and signify a major perturbation in global biogeochemical cycling, no site beneath a frontal zone has independent records of export production and δ<sup>13</sup>C on multiple carbonate phases across the critical interval of interest. Deep Sea Drilling Project (DSDP) site 590 lies beneath the Tasman Front (TF), an eddy-generating jetstream in the southwest Pacific Ocean. To complement previous δ<sup>13</sup>C records of planktic and benthic foraminifera at this location, late Neogene records of CaCO<sub>3</sub> mass accumulation rate (MAR), Ca/Ti, Ba/Ti, Al/Ti, and of bulk carbonate and foraminiferal δ<sup>13</sup>C were constructed at site 590. The δ<sup>13</sup>C records include bulk sediment, bulk sediment fractions (<63 µm and 5-25 µm), and the planktic foraminifera <i>Globigerina bulloides</i>, <i>Globigerinoides sacculifer</i> (with and without sac), and <i>Orbulina universa</i>. Using current time scales, CaCO<sub>3</sub> MARs, Ca/Ti, Al/Ti and Ba/Ti ratios are two to three times higher in upper Miocene and lower Pliocene sediment relative to overlying and underlying units. A significant decrease also occurs in all δ<sup>13</sup>C records. All evidence indicates that enhanced export production - the 'biogenic bloom' - extended to the southwest Pacific Ocean between ca. 9 and 3.8 Ma, and this phenomenon is coupled with changes in δ<sup>13</sup>C - the 'Chron C3AR carbon shift'. However, CaCO<sub>3</sub> MARs peak ca. 5 Ma whereas elemental ratios are highest ca. 6.5 Ma; foraminiferal δ<sup>13</sup>C starts to decrease ca. 8 Ma whereas bulk carbonate δ<sup>13</sup>C begins to drop ca. 5.6 Ma. Temporal discrepancies between the records can be explained by changes in the upwelling regime at the TF, perhaps signifying a link between changes in ocean-atmosphere circulation change and widespread primary productivity.
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