ALBERT

Description: The core descriptions (chapter 7) summarize the most important results of the analysis of each sediment core following procedures applied during ODP/IODP expeditions. All cores were opened, described, and color-scanned. In the core descriptions the first column displays the lithological data that are based on visual analysis of the core and are supplemented by information from binocular and smear slide analyses. The sediment classification largely follows ODP/IODP convention. Lithological names consist of a principal name based on composition, degree of lithification, and/or texture as determined from visual description and microscopic observations. In the structure column the intensity of bioturbation together with individual or special features (turbidites, volcanic ash layers, plant debris, shell fragments, etc.) is shown. The hue and chroma attributes of color were determined by comparison with the Munsell soil color charts and are given in the color column in the Munsell notation. A GretagMacbethTM Spectrolino spectrophotometer was used to measure percent reflectance values of sediment color at 36 wavelength channels over the visible light range (380-730 nm) on all of the cores. The digital reflectance data of the spectrophotometer readings were routinely obtained from the surface (measured in 1 cm steps) of the split cores (archive half). The Spectrolino is equipped with a measuring aperture with folding mechanism allowing an exact positioning on the split core and is connected to a portable computer. The data are directly displayed within the software package Excel and can be controlled simultaneously. From all the color measurements, for each core the red/blue ratio (700 nm/450 nm) and the lightness are shown together with the visual core description. The reflectance of individual wavelengths is often significantly affected by the presence of minor amounts of oxyhydroxides or sulphides. To eliminate these effects, we used the red/blue ratio and lightness.

Description: The d15N of surface and down-core sediments spanning the last 20-200 kyr from the entire South China Sea (SCS) ranges only from ~3.0 to ~6.5 per mil, with no correlation with discernible paleoclimatic/oceanographic changes. Detailed profiles of the uppermost sediment column, including fluff samples, indicate a minor diagenetic overprint of 0.3-1.2 per mil at the sediment-water interface. The absence of any correlation with reconstructed (glacial-interglacial) changes in primary production, terrigenous input, and/or sea level related basin configuration is attributed to a complete consumption of nitrate during primary production in this marginal basin during at least the last 140,000 years. This, in turn, implies that the d15N of the nitrate used during primary production remained approximately constant during the last climatic cycle. The proposed scenario infers an unchanged nitrogen isotopic composition of the western Pacific subsurface nitrate between glacial and interglacial stages as well as during terminations and thus constrains proposed changes in the oceanic N inventory.

Description: In this study we examined a wide range of paleo-productivity proxies along a latitudinal transect (36-58°S) of 6 cores in the SW Pacific during the early Holocene climatic optimum, to explore regional patterns of productivity in a slightly warmer-than present world. We used a range of sedimentological, geochemical and paleontological proxies including carbonate content and mass accumulation rates, opal content and mass accumulation rates, alkenone concentrations, a foraminiferal productivity index and dinoflagellate cyst productivity index, nitrogen isotopes and elemental concentrations from micro-XRF. During the early Holocene there is a small increase in productivity in the subtropical waters, no change at the subtropical frontal zone, and conflicting evidence in records immediately south of the subtropical front, where an increase is inferred from one core site, but not at the other. Evidence for an increase in productivity in Antarctic Surface Waters south of the polar front, is also equivocal. We infer a small increase in productivity in subtropical waters and the ocean just south of the subtropical front was associated with changes in the ocean circulation of the SW Pacific, driven by changes in the Southern Hemisphere Westerly Winds split jet structure in this region.

Description: We present lithogenic grain-size composition, high-resolution XRF bulk chemistry records, weighted coarse bulk fraction (〉150 μm) and the isotopic record of benthic foraminifera (C.wuellestorfi) of gravity sediment cores P457-905 and P57-909 from the southwestern flank of the Iceland-Faroe Ridge.

Description: This dataset includes the results of the analysis of 4 marine sediment downcore records recovered from the Labrador Sea: core MD99-2227 (58° 12.38 N, 48° 22.22 W, 3460 m); core HU08-029-004 (61°27.49 N, 58°02.11 W, 2674 m); HU84-030-021 (58°22.06 N, 57°30.42 W, 2853 m); core HU91-045-094,(50°12.26 N, 45°41.14 W, 3448 m) as well as a set of surface sediment samples. Analysis includes measurement of the radiogenic Nd isotope signatures in the authigenic Fe-Mn oxyhydroxide fraction of the bulk sediment (leachates) and of the totally dissolved residual silicate (detrital) as well as analysis of uncleaned foraminifera. Data complemented by measurements of the Rare Earth Element concentrations, some major elements (Fe, Mg, Ca, Al) and radiogenic Nd isotope signatures of the dolostone grains, picked from wet-sieved 〈 63µm sediment fraction of marine sediment downcores. The downcore records were sampled with resolution of about 1 kyr and cover roughly the last 33 ka.

Description: Sea surface temperatures (SSTs), reconstructed from two Globigerinoides ruber (white) morphotypes (G. ruber sensu stricto, (s.s.); G. ruber sensu lato, ( s.l.)) Mg/Ca and alkenones (UK'37) from core MD01-2390 from the tropical South China Sea (SCS) during the last deglaciation reveal a proxy-dependent discrepancy in the temporal pattern of the deglacial warming. Alkenone data suggest that the deglacial warming is punctuated by a decrease in temperature between not, vert, similar17 and 15 ka BP, corroborating previously published alkenone UK'37 SST records from the southern SCS. Within dating uncertainties, this cooling is coeval with the Heinrich Event 1 (H1) time interval in the North Atlantic region, underscoring the imprints of northern hemisphere forcing on tropical SCS ocean temperatures. The deglacial UK'37 SST minimum is also paralleled by a maximum in G. ruber morphotype-specific d18O. G. ruber Mg/Ca SST estimates suggest a morphotype-specific record of SSTs during the time interval of H1. Whereas G. ruber s.s. imply a continuous warming starting around 18 ka BP without any marked response to H1, G. ruber s.l.-based Mg/Ca SST estimates reveal a cooling around not, vert, similar17-15 ka BP similar to the H1 interval cooling seen in the alkenone SST record. Similar proxy-dependent differences in deglacial surface water warming have been recorded in the eastern equatorial Pacific, implying a common pattern on both sides of the tropical Pacific Ocean. We submit that this discrepancy could be due to differences in seasonality of planktonic foraminifera G. ruber morphotypes and alkenone-producing algae.