In search of the late Miocene-early Pliocene biogenic bloom'' in the Atlantic Ocean (Ocean Drilling Program Sites 982, 925, and 1088)

[1] We reconstruct paleoproductivity at three sites in the Atlantic Ocean ( Ocean Drilling Program Sites 982, 925, and 1088) to investigate the presence and extent of the late Miocene to early Pliocene biogenic bloom'' from 9 to 3 Ma. Our approach involves construction of multiple records including benthic foraminiferal and CaCO3 accumulation rates, Uvigerina counts, dissolution proxies, and geochemical tracers for biogenic and detrital fluxes. This time interval also contains the so-called late Miocene carbon isotope shift, a well-known decrease in benthic foraminiferal delta C-13 values. We find that the timing of paleoproductivity maxima differs among the three sites. At Site 982 ( North Atlantic), benthic foraminifera and CaCO3 accumulation were both at a maximum at similar to 5 Ma, with smaller peaks at similar to 6 Ma. The paleoproductivity maximum was centered earlier ( similar to 6.6 - 6.0 Ma) in the tropical Atlantic ( Site 925). In the South Atlantic ( Site 1088), paleoproductivity increased even earlier, between 8.2 Ma and 6.2 Ma, and remained relatively high until similar to 5.4 Ma. We note that there is some overlap between the interval of maximum productivity between Sites 925 and 1088, as well as the minor productivity increase at Site 982. We conclude that the paleoproductivity results support hypotheses aiming to place the biogenic bloom into a global context of enhanced productivity. In addition, we find that at all three sites the delta C-13 shift is accompanied by carbonate dissolution. This observation is consistent with published studies that have sought a relationship between the late Miocene carbon isotope shift and carbonate preservation.