Concentrations of metals and POPs in liver tissue of wild sea bird chicks from the Norwegian arctic region

Lysosomal membrane stability, lipofuscin (LF), malondialdehyde (MDA), neutral lipid (NL) levels, as well as halogenated organic compounds (HOCs), Cr, Cd, Pb and Fe concentrations were analyzed in liver of black-legged kittiwake (BK), herring gull (HG), and northern fulmar (NF) chicks. There were significant species differences in the levels of NL, LF and lysosomal membrane stability. These parameters were not associated with the respective HOC concentrations. LF accumulation was associated with increasing Cr, Cd and Pb concentrations. HG presented the lowest lysosomal membrane stability and the highest. LF and NL levels, which indicated impaired lysosomes in HG compared to NF and BK. Lipid peroxidation was associated with HOC and Fe2+ levels. Specific HOCs showed positive and significant correlations with MDA levels in HG. The study indicates that contaminant exposure can affect lysosomal and lipid associated parameters in seabird chicks even at low exposure levels. These parameters may be suitable markers of contaminant induced stress in arctic seabirds.

Diatom biostratigraphy and datum levels of sediments from ODP Leg 167 sites

Ocean Drilling Program Leg 167 represents the first time since 1978 that the North American Pacific margin was drilled to study ocean history. More than 7500 m of Quaternary to middle Miocene (14 Ma) sediments were recovered from 13 sites, representing the most complete stratigraphic sequence on the California margin. Diatoms are found in most samples in variable abundance and in a moderately well-preserved state throughout the sequence, and they are often dominated by robust, dissolution-resistant species. The Neogene North Pacific diatom zonation of Yanagisawa and Akiba (1998, doi:10.5575/geosoc.104.395) best divides the Miocene to Quaternary sequences, and updated ages of diatom biohorizons estimated based on the geomagnetic polarity time scale of Cande and Kent (1995, doi:10.1029/94JB03098) are slightly revised to adjust the differences between the other zonations. Most of the early middle Miocene through Pleistocene diatom datum levels that have been proven to be of stratigraphic utility in the North Pacific appear to be nearly isochronous within the level of resolution constrained by sample spacing. The assemblages are characterized by species typical of middle-to-high latitudes and regions of high surface-water productivity, predominantly by Coscinodiscus marginatus, Stephanopyxis species, Proboscia barboi, and Thalassiothrix longissima. Latest Miocene through Pliocene assemblages in the region of the California Current, however, are intermediate between those of subarctic and subtropical areas. As a result, neither the existing tropical nor the subarctic (high latitude) zonal schemes were applicable for this region. An interval of pronounced diatom dissolution detected throughout the Pliocene sequence apparently correspond to a relatively warmer paleoceanographic condition resulting in a slackening of the southward flow of the California Current.

Sedimentology of cores from the continental rise west of the Antarctic Peninsula

The continental rise west of the Antarctic Peninsula includes a number of large sediment mounds interpreted as contourite drifts. Cores from six sediment drifts spanning some 650 km of the margin and 48 of latitude have been dated using chemical and isotopic tracers of palaeoproductivity and diatom biostratigraphy. Interglacial sedimentation rates range from 1.1 to 4.3 cm/ka. Glacial sedimentation rates range from 1.8 to 13.5 cm/ka, and decrease from proximal to distal sites on each drift. Late Quaternary sedimentation was cyclic, with brown, biogenic, burrowed mud containing ice-rafted debris (IRD) in interglacials and grey, barren, laminated mud in glacials. Foraminiferal intervals occur in interglacial stages 5 and 7 but not in the Holocene. Processes of terrigenous sediment supply during glacial stages differed; meltwater plumes were more important in stages 2-4, turbidity currents and ice-rafting in stage 6. The terrigenous component shows compositional changes along the margin, more marked in glacials. The major oxides Al2O3 and K2O are higher in the southwest, and CaO and TiO2 higher in the northeast. There is more smectite among the clay minerals in the northeast. Magnetic susceptibility varies along and between drifts. These changes reflect source variations along the margin. Interglacial sediments show less clear trends, and their IRD was derived from a wider area. Downslope processes were dominant in glacials, but alongslope processes may have attained equal importance in interglacials. The area contrasts with the East Antarctic continental slope in the SE Weddell Sea, where ice-rafting is the dominant process and where interglacial sedimentation rates are much higher than glacial. The differences in glacial setting and margin physiography can account for these contrasts.

Distribution of abundance of planktic foraminifera and calcareous nannofossils at DSDP Sites 17-167 and 62-463

New paleomagnetic and paleontologic data from Pacific DSDP Sites 463 and 167 define the magnetic reversals that predate the Cretaceous Normal Polarity Superchron (K-N). Data from Mid-Pacific Mountain Site 463 provide the first definition of polarity chron M0 in the Pacific deep-sea sedimentary record. Foraminiferal biostratigraphy suggests that polarity chron M0 is contained entirely within the lower Aptian Hedbergella similis Zone, in agreement with foraminiferal data from the Italian Southern Alps and Atlantic Ocean. Nannofossil assemblages also suggest an early Aptian age for polarity chron M0, contrary to results from the Italian Umbrian Apennines and Southern Alps, which place polarity chron M0 on the Barremian-Aptian boundary. Biostratigraphic dating discrepancies caused by the time-transgressive, preservational, or provincial nature of paleontological species might be reconciled by the use of magnetostratigraphy, specifically polarity chron M0 which lies close to the Barremian-Aptian boundary. At Magellan Rise Site 167, five reversed polarity zones are recorded in Hauterivian to Aptian sediments. Correlation with M-anomalies is complicated by synsedimentary and postsedimentary sliding about 25 m.y. after basement formation, producing gaps in, and duplications of, the stratigraphic sequence. The magnitude and timing of such sliding must be addressed when evaluating the stratigraphy of these oceanic-rise environments.

Cloride and bromide concentrations and Br-/Cl- molar ratios in pore fluids at ODP Site 134-833

Other than halite diagenesis and organic matter degradation, Cl- and Br- are considered to be conservative in marine pore fluids. Consequently, Br-/Cl- ratios should remain constant during most diagenetic reactions. Nonetheless, Br-/Cl- molar ratios decrease to 0.00127 (~18% less than seawater value) in pore fluids from Site 833 in the Aoba Basin of the New Hebrides convergent margin despite the lack of halite diagenesis and little organic matter. Sediment at this site is largely volcanic ash, which becomes hydrated with depth as it converts to clay and zeolite minerals. These hydration reactions remove sufficient water to increase the concentrations of most solutes including Cl- and Br-. The resulting concentration gradients drive diffusion, but calculations indicate that diffusion does not decrease the Br-/Cl- ratio. Some Cl- may be leached from the ash, but insufficient amounts are available to cause the observed decrease in Br-/Cl- ratio. The limited source of Cl- suggests that proportionately more Br- than Cl- is lost from the fluids to the diagenetic solids. Similar nonconservative behavior of Cl- and Br- may occur during fluid circulation at ridge crests and flanks, thereby influencing the halide distribution in the crust.

Carbonate record of ODP Leg 167 sites

One of the expected scientific results of Ocean Drilling Program Leg 167 was to reconstruct the Neogene history of biogenic calcium carbonate accumulation in the northeastern Pacific along the California margin (Lyle, Koizumi, Richter, et al., 1997). This aims to constrain inorganic carbon burial rates, deep-water hydrography in the North Pacific, and linkages between deep Atlantic and Pacific circulation and carbonate accumulation or dissolution patterns. Data are presented for four sites. Two of them are located in the California bight-East Cortez Basin (Site 1012: 32°16.970?N 118°23.024?W, 1773 m) and San Nicholas Basin (Site 1013: 32°48.040??, 118°53.992?W, 1564 m). The others are the dedicated Hole 1017E at Site 1017 (34°32.099?N, 121°6.430?W, 955 m) and Site 1019 in the Eel River Basin (41¢X40.972?N, 124°55.975?W, 977 m). Reconstruction of paleo-sea-surface temperatures (SST) by determining the alkenone unsaturation index of the extractable organic matter is an independent technique and helps to verify oxygen-isotope-based estimates. Results from the uppermost 600 cm of the dedicated Hole 1017E are expected to reveal the local temperature history of the last 30 k.y.