Sedimentological, geochemical, micropaleontological and rock magnetic proxies of sediment core GeoB6211-2

Surface currents and sediment distribution of the SE South American upper continental margin are under influence of the South American Monsoon System (SAMS) and the Southern Westerly Wind Belt (SWWB). Both climatic systems determine the meridional position of the Subtropical Shelf Front (STSF) and probably also of the Brazil-Malvinas Confluence (BMC). We reconstruct the changing impact of the SAMS and the SWWB on sediment composition at the upper Rio Grande Cone off southern Brazil during the last 14 cal kyr combining sedimentological, geochemical, micropaleontological and rock magnetic proxies of marine sediment core GeoB 6211-2. Sharp reciprocal changes in ferri- and paramagnetic mineral content and prominent grain-size shifts give strong clues to systematic source changes and transport modes of these mostly terrigenous sediments. Our interpretations support the assumption that the SAMS over SE South America was weaker than today during most of the Late Glacial and entire Early Holocene, while the SWWB was contracted to more southern latitudes, resembling modern austral summer-like conditions. In consequence, the STSF and the BMC were driven to more southern positions than today's, favoring the deposition of Fe-rich but weakly magnetic La Plata River silts at the Rio Grande Cone. During the Mid Holocene, the northern boundary of the SWWB migrated northward, while the STSF reached its northernmost position of the last 14 cal kyr and the BMC most likely arrived at its modern position. This shift enabled the transport of Antarctic diatoms and more strongly magnetic Argentinean shelf sands to the Rio Grande Cone, while sediment contributions from the La Plata River became less important. During the Late Holocene, the modern El Niño Southern Oscillation set in and the SAMS and the austral tradewinds intensified, causing a southward shift of the STSF to its modern position. This reinforced a significant deposition of La Plata River silts at the Rio Grande Cone. These higher magnetic silts with intermediate Fe contents mirror the modern more humid terrestrial climatic conditions over SE South America.

Age determination and Sea surface temperature reconstruction for sediment core H214

We present sea surface temperature (SST) records with centennial-scale resolution from the Bay of Plenty, north of New Zealand. Foraminiferal assemblage-based paleo-SST estimates provide a deglacial record of SST since 16.5 14C ka. Average Holocene SSTs are 15.6°C for winter and 20.3°C for summer, whereas average glacial values were 14.2°C for winter and 19.5°C for summer. Compared to modern time, cooling of SSTs at the Last Glacial Maximum (LGM) was ~0.9°C in winter and ~1.5°C in summer. The shift from glacial to Holocene temperatures began at 14.25 14C ka, warming by ~2°C until 12.85 14C ka when temperatures dipped back to glacial values at 11.65 14C ka. The timing of this return to glacial-like SST correlates well with the Antarctic Cold Reversal (ACR) rather than the Younger Dryas and documents that the influence of the ACR extended into the subtropics of the Southern Hemisphere, at least in this region of the southwest Pacific. By 10.55 14C ka an SST maximum in summer SSTs of up to 3°C warmer than modern occurred (?24°C), after which SST dropped, remaining at present-day temperatures since 9.3 14C ka. This early Holocene climatic optimum has been widely noted in the Southern Ocean, and this record indicates that this phenomenon also extended into the subtropics to the north of New Zealand.

(Table 2) Radiocarbon age determination from the polar planktonic foraminifera Neogloboquadrina pachyderma s for sediment core HU90-013-029

An additional Heinrich ice-rafting event is identified between Heinrich events 5 and 6 in eight cores from the Labrador Sea and the northwest Atlantic Ocean. It is characterized by sediment rich in detrital carbonate (40% CaCO3) with high concentration of floating dropstones, high coarse-fraction (% > 150 µm) content, and has a sharp contact with the underlying but grades into the overlying hemipelagic sediment. It also shows lighter d18ONpl values, indicating freshening due to iceberg rafting and/or meltwater discharge. This event is correlated with Dansgaard-Oeschger event 14 and interpreted as an additional Heinrich event, H5a. The thickness of H5a in the Labrador Sea reaches up to 220 cm. This additional Heinrich event has also been reported in cores PS2644 and SO82-5 from the northern North Atlantic. With the recognition of H5a the temporal spacing between Heinrich events 1 to 6 becomes more uniform (~7 ka).

AMS C-14 ages of coretops collected on RRS Charles Darwin cruise CD159, July 2004, N. Atlantic, for the NERC RAPID programme

Material and data were collected at 41 sites in the subpolar North Atlantic Ocean between Scotland and Newfoundland, during the RRS CharlesDarwin CD159 cruise in July 2004 (McCave, 2005). Sites were selected to reflect the major inputs of water that becomes the North Atlantic Deep Water (NADW); the Iceland-Scotland Overflow Water (ISOW), the Denmark Strait Overflow Water (DSOW) and the Labrador Sea Water (LSW). Areas cored were the south Iceland Rise, SE Greenland slope/rise and Eirik Drift, and the Labrador margin. A total of 29 box cores, 19 piston cores, 6 kasten cores, 9 short gravity cores and 20 CTD casts as well as 28 surface water samples were collected during the cruise. Here we present sediment core-top sample ages. The cores were sampled at 1 or 0.5 cm intervals and we used the top 1 or 2 cm, depending on availability of foraminifera in the samples. Sediment samples were disaggregated on an end-over-end wheel, wet sieved at >63 um, and dry sieved to 63-150 and >150 um. Accelerator Mass Spectrometer (AMS) radiocarbon dating was done for each core top based on between 900-1600 monospecific planktonic foraminifera (Globigerina bulloides or Neogloboquadrina pachyderma (sinistral)). All dates were of modern or late Holocene age except site RAPID-08-5B (9806 ± 38 uncorrected 14C years BP) and site RAPID-14-10B (11543 ± 40 uncorrected 14C years BP). The >150 um fraction was split until approximately 300 foraminifera remained and counted for number of lithic grains, benthic foraminifera, planktonic foraminifera and foraminifera fragments. In all but the shallowest sample (Greenland rise, 761m water depth) benthic foraminifera constituted less than 2% of the total >150 um fraction of the sample.

Sedimentology and stable carbon and oxygen isotope record of the Central Arctic

Stable oxygen and carbon isotope and sedimentological-paleontological investigations supported by accelerator mass spectrometry 14C datings were carried out on cores from north of 85°N in the eastern central Arctic Ocean. Significant changes in accumulation rates, provenance of ice-rafted debris (IRD), and planktic productivity over the past 80,000 years are documented. During peak glacials, i.e., oxygen isotope stages 4 and 2, the Arctic Ocean was covered by sea ice with decreased seasonal variation, limiting planktic productivity and bulk sedimentation rates. In early stage 3 and during Termination I, major deglaciations of the circum-Arctic regions caused lowered salinities and poor oxygenation of central Arctic surface waters. A meltwater spike and an associated IRD peak dated to ~14-12 14C ka can be traced over the southern Eurasian Basin of the Arctic Ocean. This event was associated with the early and rapid deglaciation of the marine-based Barents Sea Ice Sheet. A separate Termination Ib meltwater event is most conspicuous in the central Arctic and is associated with characteristic dolomitic carbonate IRD. This lithology suggests an origin of glacial ice from northern Canada and northern Greenland where lower Paleozoic platform carbonates crop extensively out.

Pollen record and age determinations of a profile at Cape Mamontov Klyk, Siberia

Non-glaciated Arctic lowlands in north-east Siberia were subjected to extensive landscape and environmental changes during the Late Quaternary. Coastal cliffs along the Arctic shelf seas expose terrestrial archives containing numerous palaeoenvironmental indicators (e.g., pollen, plant macro-fossils and mammal fossils) preserved in the permafrost. The presented sedimentological (grain size, magnetic susceptibility and biogeochemical parameters), cryolithological, geochronological (radiocarbon, accelerator mass spectrometry and infrared-stimulated luminescence), heavy mineral and palaeoecological records from Cape Mamontov Klyk record the environmental dynamics of an Arctic shelf lowland east of the Taymyr Peninsula, and thus, near the eastern edge of the Eurasian ice sheet, over the last 60 Ky. This region is also considered to be the westernmost part of Beringia, the non-glaciated landmass that lay between the Eurasian and the Laurentian ice caps during the Late Pleistocene. Several units and subunits of sand deposits, peat-sand alternations, ice-rich palaeocryosol sequences (Ice Complex) and peaty fillings of thermokarst depressions and valleys were presented. The recorded proxy data sets reflect cold stadial climate conditions between 60 and 50 Kya, moderate inderstadial conditions between 50 and 25 Kya and cold stadial conditions from 25 to 15 Kya. The Late Pleistocene to Holocene transition, including the Allerød warm period, the early to middle Holocene thermal optimum and the late Holocene cooling, are also recorded. Three phases of landscape dynamic (fluvial/alluvial, irregular slope run-off and thermokarst) were presented in a schematic model, and were subsequently correlated with the supraregional environmental history between the Early Weichselian and the Holocene.

Sedimentation rates calculated on surface sediment samples from different site of the Atlantic and Pacific Oceans (Table 1)

Radiocarbon ages on CaCO3 from deep-sea cores offer constraints on the nature of the CaCO3 dissolution process. The idea is that the toll taken by dissolution on grains within the core top bioturbation zone should be in proportion to their time of residence in this zone. If so, dissolution would shift the mass distribution in favor of younger grains, thereby reducing the mean radiocarbon age for the grain ensemble. We have searched in vain for evidence supporting the existence of such an age reduction. Instead, we find that for water depths of more than 4 km in the tropical Pacific the radiocarbon age increases with the extent of dissolution. We can find no satisfactory steady state explanation and are forced to conclude that this increase must be the result of chemical erosion. The idea is that during the Holocene the rate of dissolution of CaCO3 has exceeded the rain rate of CaCO3. In this circumstance, bioturbation exhumes CaCO3 from the underlying glacial sediment and mixes it with CaCO3 raining from the sea surface.

(Table 1) Age determination of sediment cores south of the Faeroe Islands

A study was made of three cores from the Faeroe-Shetland gateway, based on planktonic foraminifera, oxygen isotopes, accelerator mass spectrometry 14C dates, magnetic susceptibility, and counts of ice rafted debris (IRD). The data, covering the period 30-10 ka, show that during the Last Glacial Maximum the Arctic Front occupied a position close to the Faeroes, allowing a persisting inflow of Atlantic surface water into the Faeroe-Shetland Channel. The oceanographic environment during deposition of two IRD layers is influenced by Atlantic surface water masses during the lower IRD layer, with transport of icebergs from N-NW. Polar surface water conditions prevailed only during deposition of the upper IRD layer. There is no indication of surface meltwater influence in the region during the deglaciation, but there is a persistent influence of Atlantic surface water masses in the region. Thus we conclude that during almost the entire period (30-10 ka) the Faeroe-Shetland Channel was a gateway for transport of Atlantic surface water toward the Norwegian Sea.

Performance tests for the evaluation of computerized gas chromatography/mass spectrometry equipment and laboratories /

"April 1980"--Cover.

The determination of uranium isotope abundances and reactor fuel burnup by mass spectrometry /

April 17, 1963--page 11.

Investigation of solid surfaces by field emission microscopy and mass spectrometry; final report.

"Contract no. AF 49 (638)-748. Division file 30-4. AFOSR-2273."

Method of analysis and quality-assurance practices for determination of pesticides in water by solid-phase extraction and capillary-column gas chromatography/mass spectrometry at the U.S. Geological Survey California District Organic Chemistry Laboratory, 1996-99 /

Mode of access: Internet.

Method Development and Validation of Vitamin D2 and Vitamin D3 using Mass Spectrometry

Thesis (Master's)--University of Washington, 2016-06

Measurement of free drug and clinical end-point by high-performance liquid chromatography-mass spectrometry: Applications and implications for pharmacokinetic and pharmacodynamic studies

Free drug measurement and pharmacodymanic markers provide the opportunity for a better understanding of drug efficacy and toxicity. High-performance liquid chromatography (HPLC)-mass spectrometry (MS) is a powerful analytical technique that could facilitate the measurement of free drug and these markers. Currently, there are very few published methods for the determination of free drug concentrations by HPLC-MS. The development of atmospheric pressure ionisation sources, together with on-line microdialysis or on-line equilibrium dialysis and column switching techniques have reduced sample run times and increased assay efficiency. The availability of such methods will aid in drug development and the clinical use of certain drugs, including anti-convulsants, anti-arrhythmics, immunosuppressants, local anaesthetics, anti-fungals and protease inhibitors. The history of free drug measurement and an overview of the current HPLC-MS applications for these drugs are discussed. Immunosuppressant drugs are used as an example for the application of HPLC-MS in the measurement of drug pharmacodynamics. Potential biomarkers of immunosuppression that could be measured by HPLC-MS include purine nucleoside/nucleotides, drug-protein complexes and phosphorylated peptides. At the proteomic level, two-dimensional gel electrophoresis combined with matrix-assisted laser desorption/ionisation time-of-flight (TOF) MS is a powerful tool for identifying proteins involved in the response to inflammatory mediators. (C) 2003 Elsevier Science B.V. All rights reserved.