(Appendix A) Abundance of selected coccolithophores in sediment core DS97-2P, North Atlantic

The calcareous nannofossil assemblages from sediment core DS97-2P from the Reykjanes Ridge have been investigated to document oceanographic changes in surface water during the Holocene. The recorded variations in coccolithophore species assemblages and accumulation rates indicate that the region was subjected to rapid changes of surface water masses throughout the entire Holocene. Coccolithophore assemblages generally are of low species diversity and consist mainly of Emiliania huxleyi and Coccolithus pelagicus ssp. pelagicus. Two major events occurred at 8.5-7 ka and at 4.5-3.5 ka, showing higher coccolith accumulation rates, suggesting that the influence of relatively warm Atlantic waters via the Irminger Current was strong in the investigated area. The coccolithophore assemblages have been compared with diatom, foraminifer and sedimentological records within the same core. These data, supported by a comparison with previously published proxy records, add credit to the hypothesis that Holocene changes did not occur uniformly across the North Atlantic. The results have highlighted the Holocene pattern in the North Atlantic, as a period influenced by strong regionalism with discrepancies in the hydrographical trends and in the distribution of the planktonic proxies.

Coccolithophore taxa and PCA factor analysis of ODP Site 1233

We provide high-resolution sea surface temperature (SST) and paleoproductivity data focusing on Termination 1. We describe a new method for estimating SSTs based on multivariate statistical analyses performed on modern coccolithophore census data, and we present the first downcore reconstructions derived from coccolithophore assemblages at Ocean Drilling Project (ODP) Site 1233 located offshore Chile. We compare our coccolithophore SST record to alkenone-based SSTs as well as SST reconstructions based on dinoflagellates and radiolaria. All reconstructions generally show a remarkable concordance. As in the alkenone SST record, the Last Glacial Maximum (LGM, 19-23 kyr B.P.) is not clearly defined in our SST reconstruction. After the onset of deglaciation, three major warming steps are recorded: from 18.6 to 18 kyr B.P. (~2.6°C), from 15.7 to 15.3 kyr B.P. (~2.5°C), and from 13 to 11.4 kyr B.P. (~3.4°C). Consistent with the other records from Site 1233 and Antarctic ice core records, we observed a clear Holocene Climatic Optimum (HCO) from ~8-12 kyr B.P. Combining the SST reconstruction with coccolith absolute abundances and accumulation rates, we show that colder temperatures during the LGM are linked to higher coccolithophore productivity offshore Chile and warmer SSTs during the HCO to lower coccolithophore productivity, with indications of weak coastal upwelling. We interpret our data in terms of latitudinal displacements of the Southern Westerlies and the northern margin of the Antarctic Circumpolar Current system over the deglaciation and the Holocene.

Census of calcareous nannofossil taxa expressed as percent of total number of individuals counted, ODP Legs 113, 114, 119, 120

Quantitative analysis of upper Eocene-upper Oligocene calcareous nannofossil assemblages from five Ocean Drilling Program sites in the Atlantic and Indian Ocean sectors of the Southern Ocean reveals an abrupt increase in cool-water taxa at the top of magnetic Subchron C13R ca. 35.9 Ma, coincident with an enrichment of ~1? d18O in the planktonic foraminifers at these sites. The synchrony of the abrupt increase in cool-water taxa in the Southern Ocean renders this event a useful biostratigraphic datum at southern high latitudes. This earliest Oligocene cool-water taxa increase was the sharpest and largest during the late Eocene-late Oligocene interval and indicates a drop in surface-water temperature of more than 3°C in the Southern Ocean. This suggests that the earliest Oligocene d18O shift represents primarily a temperature signal; a small portion (~0.2?) is attributable to a global ice-volume increase.

Calcareous nannofossils of ODP Leg 103 holes

Ocean Drilling Program Leg 103 occupied five sites on the Galicia margin, northwest of the Iberian Peninsula. Two holes (Holes 637A and 638B) yielded significant Cenozoic sedimentary sections ranging from late Miocene to late Pleistocene in age. From the nannofossil stratigraphy, one hiatus is recognized in Hole 637A (2.35-2.4 Ma), whereas two hiatuses (one at 1.9-2.6 Ma and another at 3.5-3.7 Ma) are recognized in Hole 638B. Sediment-accumulation rates for the Cenozoic portions of these two holes have been calculated based on the nannofossil datums. The abundance ratios of Coccolithus pelagicus to Discoaster brouweri for Hole 637A show relatively low values and small fluctuations from 2.5 to 6.5 Ma but sharply increase and then widely fluctuate beginning at about 2.5 Ma. This may indicate relatively warmer, more stable surface-water temperatures from 2.5 to 6.5 Ma and cooler, variable surface-water temperatures after 2.5 Ma at Site 637. C. pelagicus/D. brouweri ratios from Hole 638B also show a trend of increasing values with time from late Miocene to late Pliocene, but with more fluctuations and a different pattern from that of Hole 637A.

Calcareous nannofossil stratigraphy of sediments from ODP Holes 186-1150A and 186-1151C, Japan Trench

To assess the paleoceanographic potential of Leg 186 sediments, we investigated Quaternary calcareous nannofossil flora at Sites 1150 and 1151 in the Japan Trench. Because of the frequent occurrence of barren intervals and the lack of oxygen isotope data, a detailed paleoceanography is not feasible for these cores. We limited our study to the upper 26.07 m of the section from Hole 1150A and the upper 21.01 m of the section from Hole 1151C. The studied samples from Cores 186-1150A-1H through 3H are younger than 0.085 Ma. Core 186-1151C-1H (upper 1.92 meters below seafloor [mbsf]) is younger than 0.085 Ma, and samples between 2H-7, 5-7 cm, and 3H-CC, 5-7 cm, (9.99-21.01 mbsf) are older than 0.245 Ma and younger than 0.408 Ma.

Age determination and faunal composition of sediments off northern Greenland

We present a record encompassing marine isotope stages 7-1 from a hitherto unexplored and heavily ice-covered area of the Arctic Ocean, the Lomonosov Ridge off the northern Greenland-Canada continental margin, using nannofossil and benthic foraminifera stratigraphy. Planktic foraminifera assemblages are used as a key paleoceanographic proxy, and a surprisingly large variability is found for an interior Arctic Ocean site. Abundant small (63-125 µm) subpolar Turborotalita quinqueloba occur in two sections, possibly representing substages 5e (last interglacial) and 5a (warm interstadial). However, the present-day circulation pattern and the very distant location of high productive regions cannot explain such high abundances of subpolar specimens in the interior, perennially sea ice-covered Arctic Ocean. Hence our proxy record indicates that last interglacial sea ice concentrations were reduced off some areas of northern Greenland-Canada. Whether this was part of a larger regional pattern or it represents the influence of polynya areas with locally increased productivity remains to be solved. With respect to glacial conditions, increased ice-rafted debris (IRD) deposition in the area appears to be associated with glacial stages 6, 4, and late 3. Stage 2 sediments (including the Last Glacial Maximum) are condensed with a sparse IRD content only.

Calcareous nannofossil abundance estimates and datums of ODP Leg 189 sites

A major objective of Leg 189 was to date the opening of the Australia-Antarctic Gateway to shallow-water circulation and subsequently to deepwater circulation in the Paleogene. Calcareous nannofossils are the most consistently present, although not necessarily the most abundant fossil group in Paleogene sections, and the shipboard study (Exon, Kennett, Malone, et al., 2001, doi:10.2973/odp.proc.ir.189.2001) showed that they generally provided the most useful age information. This report presents documentation of the stratigraphic distribution of nannofossils in the Paleogene and summarizes useful nannofossil datums, which should facilitate construction of age-depth curves and contribute to an integrated chronology for Leg 189 sediments. Previous Paleogene nannofossil study in this area is that of Edwards and Perch-Nielsen (1975, doi:10.2973/dsdp.proc.29.113.1975).