Chemistry of interstitial waters of ODP Leg 117 samples (Table 1)

Interstitial water analyses made at 12 sites during Leg 117 are used to define the nature of diagenetic reactions in organic-rich sediments on the Owen Ridge and Oman Margin. Minor variations in chloride concentration profiles are ascribed to past changes in bottom water salinity at two mid-depth margin sites and to upward migration of low salinity water at another. There is no evidence for subsurface brine movement, unlike the case on the Peru Margin. Dolomitization is widespread and accounts for the depletions of magnesium observed in pore waters at variable depths at nearly all sites. The mineral occurs both as disseminated euhedral limpid crystals and, in at least one location, in massive stringers. Formation of the latter is suggested to reflect precipitation during sea level transgressions when the sedimentation rate was low, but when productivity was high. Authigenic carbonate fluorapatite is also widespread, the phosphorus being derived from the breakdown of organic matter. Sulfate is quantitatively depleted at depth at most locations but the rate of depletion is markedly less than that observed on the Peru Margin where sedimentation is also similarly influenced by high rates of upwelling. The reason for this contrast is not clear and merits further investigation.

(Table 1) Oxygen isotopic composition of interstitial waters from ODP Hole 161-976

Interstitial waters recovered from Ocean Drilling Program, Leg 161, site 976 in the western Mediterranean Sea are used in conjunction with a numerical model to constrain the delta18O of seawater in the basin since the Last Glacial Maximum, including Sapropel Event 1. To resolve the oxygen isotopic composition of the deep Mediterranean, we use a model that couples fluid diffusion with advective transport, thus producing a profile of seawater delta18O variability that is unaffected by glacial-interglacial variations in marine temperature. Comparing our reconstructed seawater delta18O to recent determinations of 1.0 per mil for the mean ocean change in glacial-interglacial delta18O due to the expansion of global ice volume, we calculate an additional 0.2 per mil increase in Mediterranean delta18O caused by local evaporative enrichment. This estimate of delta18O change, due to salinity variability, is smaller than previous studies have proposed and demonstrates that Mediterranean records of foraminiferal calcite delta18O from the last glacial period include a strong temperature component. Paleotemperatures determined in combination with a stacked record of foraminiferal calcite depict almost 9°C of regional cooling for the Last Glacial Maximum. Model results suggest a decrease of ~1.1 per mil in seawater delta18O relative to the modern value caused by increased freshwater input and reduced salinity accompanying the formation of the most recent sapropel. The results additionally indicate the existence of isotopically light water circulating down to bottom water depths, at least in the western Mediterranean, supporting the existence of an 'anti-estuarine' thermohaline circulation pattern during Sapropel Event 1.

(Table 1) Age determination of Chukchi Sea sediments

Dinocysts from cores collected in the Chukchi Sea from the shelf edge to the lower slope were used to reconstruct changes in sea surface conditions and sea ice cover using modern analogue techniques. Holocene sequences have been recovered in a down-slope core (B15: 2135 m, 75°44'N, sedimentation rate of ~1 cm/kyr) and in a shelf core (P1: 201 m, 73°41'N, sedimentation rate of ~22 cm/kyr). The shelf record spanning about 8000 years suggests high-frequency centennial oscillations of sea surface conditions and a significant reduction of the sea ice at circa 6000 and 2500 calendar (cal) years B.P. The condensed offshore record (B15) reveals an early postglacial optimum with minimum sea ice cover prior to 12,000 cal years B.P., which corresponds to a terrestrial climate optimum in Bering Sea area. Dinocyst data indicate extensive sea ice cover (>10 months/yr) from 12,000 to 6000 cal years B.P. followed by a general trend of decreasing sea ice and increasing sea surface salinity conditions, superimposed on large-amplitude millennial-scale oscillations. In contrast, d18O data in mesopelagic foraminifers (Neogloboquadrina pachyderma) and benthic foraminifers (Cibicides wuellerstorfi) reveal maximum subsurface temperature and thus maximum inflow of the North Atlantic water around 8000 cal years B.P., followed by a trend toward cooling of the subsurface to bottom water masses. Sea-surface to subsurface conditions estimated from dinocysts and d18O data in foraminifers thus suggest a decoupling between the surface water layer and the intermediate North Atlantic water mass with the existence of a sharp halocline and a reverse thermocline, especially before 6000 years B.P. The overall data and sea ice reconstructions from core B15 are consistent with strong sea ice convergence in the western Arctic during the early Holocene as suggested on the basis of climate model experiments including sea ice dynamics, matching a higher inflow rate of North Atlantic Water.

(Table 1) Boron concentration and d11B values of interstitial water from IODP Holes 308-U1319A, U1320A, U1322B and U1324B

The Integrated Ocean Drilling Program Expedition 308 (IODP308) drilled normal-pressured sediments from the Brazos-Trinity Basin IV and over-pressured sediments from the Ursa Basin on the northern slope of the Gulf of Mexico. The interstitial water samples from the normal-pressured basin show B concentrations and B isotopic compositions ranging from 255 to 631 µM (0.6 to 1.5 times of seawater value) and from +29.1 to +42.7 per mil (relative to NIST SRM 951), respectively. A wider range is observed both for B concentrations (292 to 865 µM, 0.7 to 2.1 times of seawater value) and d11B values (+25.5 to +43.2 per mil) of the interstitial water in the over-pressured basin. The down-core distribution of B concentrations and d11B values in the interstitial waters are sensitive tracers for assessing various processes occurring in the sediment column, including boron adsorption/desorption reactions involving clay minerals and organic matter in sediments as well as fluid migration and mixing in certain horizons and in the sediment column. In the normal-pressured basin adsorption/desorption reactions in shallow sediments play the major role in controlling the B content and B isotopic composition of the interstitial water. In contrast, multiple processes affect the B content and d11B of the interstitial water in the over-pressured Ursa Basin. There, the stratigraphic level of the maxima of B and d11B correspond to seismic reflectors. The intruded fluids along the seismic reflector boundary from high to low-topography mix with local interstitial water. Fluid flow is inferred in the Blue Unit (a coarse sandstone layer, connecting the high- to low-pressured region) from the freshening of interstitial water in Ursa Basin Site U1322, and upward flow by the overpressure expels fluid from the overburden above the Blue Unit.

(Table 1) Radiocarbon dating of a lake sediment core, southern West Greenland

The dominant processes determining biological structure in lakes at millennial timescales are complex. In this study, we used a multi-proxy approach to determine the relative importance of in-lake versus indirect processes on the Holocene development of an oligotrophic lake in SW Greenland (66.99°N, 50.97°W). A 14C and 210Pb-dated sediment core covering approximately 8500 years BP was analyzed for organic-inorganic carbon content, pigments, diatoms, chironomids, cladocerans, and stable isotopes (d13C, d18O). Relationships among the different proxies and a number of independent controlling variables (Holocene temperature, an isotope-inferred cooling period, and immigration of Betula nana into the catchment) were explored using redundancy analysis (RDA) independent of time. The main ecological trajectories in the lake biota were captured by ordination first axis sample scores (18-32% variance explained). The importance of the arrival of Betula (ca. 6500 years BP) into the catchment was indicated by a series of partial-constrained ordinations, uniquely explaining 12-17% of the variance in chironomids and up to 9% in pigments. Climate influences on lake biota were strongest during a short-lived cooling period (identified by altered stable isotopes) early in the development of the lake when all proxies changed rapidly, although only chironomids had a unique component (8% in a partial-RDA) explained by the cooling event. Holocene climate explained less variance than either catchment changes or biotic relationships. The sediment record at this site indicates the importance of catchment factors for lake development, the complexity of community trends even in relatively simple systems (invertebrates are the top predators in the lake) and the challenges of deriving palaeoclimate inferences from sediment records in low-Arctic freshwater lakes.

(Table 1) Radiocarbon ages of foraminifera from a Piston and a Trigger Weight from Ceara Rise

Radiocarbon-age measurements on single species of foraminifera from a core on the Ceara Rise demonstrate the importance of the joint effect of bioturbation and variable rain abundance of foraminifera. The relatively high mixed layer ages for Pulleniatina obliquiloculata reflect, at least in part, an early Holocene peak in its abundance while the relatively young ages for Globorotalia menardii reflect the delay until mid Holocene of its reappearance in the Atlantic Ocean. These results clearly demonstrate that core-top sediment samples need not be representative foraminifera falling from today's surface ocean. Rather, at least on the Ceara Rise, such samples consist of a composite of changing species groupings. These results also reconfirm the pitfalls associated with attempts to reconstruct the radiocarbon age of deep ocean water on the basis of benthic-planktonic foraminiferal age differences.

(Table 1) Radiocarbon ages of core AB01/94 obtained in the Tromper Wiek, western Baltic Sea

In the Tromper Wiek northeast of Rügen, acoustical investigations using Air Gun, Boomer, Chirp Sonar and Sediment-Echosounder were carried out. Together with sediment core information, it allowed the identification of five seismostratigraphic units (E1 to E5). Conventional and AMS-14C-datings supported their chronostratigraphical classification. The uppermost till (E1) was incised by late glacial channels filled with glaciolacustrine sediments (E2) of the early Baltic Ice Lake stages. These were regionally overlain with a sharp unconformity by a thick (locally >20 m) sedimentary complex (E3) of acoustically laminated silts of freshwater origin. This lower part of the E3-complex (E3a) is overlain by fluvial to coastal silty fine sands (E3b) deeper towards the Arkona Basin. Fine plant debris in the uppermost part of sub-unit E3a yielded ages of 10,100 and 10,500 14C-years B.P., representing the final phase of the Baltic Ice Lake. The fine sands of sub-unit E3b were deposited after the final drainage of the Baltic Ice Lake. In the shallower central part of the bay, the silts of sub-unit E3a were covered by a younger unit (E4) of fine sand with plant debris. A sedge peat occurring at the basis of unit E4 yielded an age of 9,590 14C-years B.P. The fine sands overlying the unit E3 in the central part of Tromper Wiek were deposited in the Ancylus Lake. Their position at about 20 m below present sea level (b.s.l.) reflects the maximum highstand in this area. The character and distribution of the Early Holocene deposits at greater depth suggest a lake water level at about 30 m b.s.l. after this highstand. Below 25 m b.s.l. muddy Littorina Sea sediments are observed. The thickness of these muds and sandy muds increases gradually towards the Arkona Basin. Locally, they are found in a channel-like structure immediately north of Jasmund.

(Table S1) TEX86 and BIT record from sediment core PBBC-1

A molecular organic geochemical proxy (TEX86) for sea surface temperature (SST) is compared with a foraminifera-based SST proxy (Mg/Ca) in a decadal-resolution marine sedimentary record spanning the last 1000 years from the Gulf of Mexico. We assess the relative strengths of the organic and inorganic paleoceanographic techniques for reconstructing high-resolution SST variability during recent climate events, including the Little Ice Age (LIA) and the Medieval Warm Period (MWP). SST estimates based on the molecular organic proxy TEX86 show a similar magnitude and pattern of SST variability to foraminiferal Mg/Ca-SST estimates but with some important differences. For instance, both proxies show a cooling (1°C-2°C) of Gulf of Mexico SSTs during the LIA. During the MWP, however, Mg/Ca-SSTs are similar to near-modern SSTs, while TEX86 indicates SSTs that were cooler than modern. Using the respective SST calibrations for each proxy results in TEX86-SST estimates that are 2°C-4°C warmer than Mg/Ca-SST throughout the 1000 year record. We interpret the TEX86-SST as a summer-weighted SST signal from the upper mixed layer, whereas the Mg/Ca-SST better reflects the mean annual SST. Downcore differences in the SST estimates between the two proxies (DeltaT = TEX86 - Mg/Ca) are interpreted in the context of varying seasonality and/or changing water column temperature gradients.

d13C and d15N stable isotopes values, total nitrogen and C/N ratios of sediment core GeoB4801-1

Rising stable nitrogen isotope ratios (d15N) in dated sediment records of the German Bight/SE North Sea track river-induced coastal eutrophication over the last 2 centuries. Fully exploiting their potential for reconstructions of pristine conditions and quantitative analysis of historical changes in the nitrogen cycle from these sediment records requires knowledge on processes that alter the isotopic signal in non-living organic matter (OM) of sinking particles and sediments. In this study, we analyze the isotopic composition of particulate nitrogen (PN) in the water column during different seasons, in surface sediments, and in sediment cores to assess diagenetic influences on the isotopic composition of OM. Amino acid (AA) compositions of suspended matter, surface sediments, and dated cores at selected sites of the German Bight serve as indicators for quality and degradation state of PN. The d15N of PN in suspended matter had seasonal variances caused by two main nitrate sources (oceanic and river) and different stages of nitrate availability during phytoplankton assimilation. Elevated d15N values (> 20 per mil) in suspended matter near river mouths and the coast coincide with a coastal water mass receiving nitrate with elevated isotope signal (d15N > 10 per mil) derived from anthropogenic input. Particulate nitrogen at offshore sites fed by oceanic nitrate having a d15N between 5 and 6 per mil had low d15N values (< 2 per mil), indicative of an incipient phytoplankton bloom. Surface sediments along an offshore-onshore transect also reflect the gradient of low d15N of nitrate in offshore sites to high values near river mouths, but the range of values is smaller than between the end members listed above and integrates the annual d15N of detritus. Sediment cores from the coastal sector of the gradient show an increasing d15N trend (increase of 2.5 per mil) over the last 150 years. This is not related to any change in AA composition and thus reflects eutrophication. The d15N signals from before AD 1860 represent a good estimation of pre-industrial isotopic compositions with minimal diagenetic overprinting. Rising d13C in step with rising d15N in these cores is best explained by increasing productivity caused by eutrophication.