Atmospheric nitrate concentrations and isotope composition for samples collected in the marine boundary layer in 2006 and 2007

The comprehensive isotopic composition of atmospheric nitrate (i.e., the simultaneous measurement of all its stable isotope ratios: 15N/14N, 17O/16O and 18O/16O) has been determined for aerosol samples collected in the marine boundary layer (MBL) over the Atlantic Ocean from 65°S (Weddell Sea) to 79°N (Svalbard), along a ship-borne latitudinal transect. In nonpolar areas, the d15N of nitrate mostly deriving from anthropogenically emitted NOx is found to be significantly different (from 0 to 6 per mil) from nitrate sampled in locations influenced by natural NOx sources (-4 ± 2) per mil. The effects on d15N(NO3-) of different NOx sources and nitrate removal processes associated with its atmospheric transport are discussed. Measurements of the oxygen isotope anomaly (D17O = d17O - 0.52 × d18O) of nitrate suggest that nocturnal processes involving the nitrate radical play a major role in terms of NOx sinks. Different D17O between aerosol size fractions indicate different proportions between nitrate formation pathways as a function of the size and composition of the particles. Extremely low d15N values (down to -40 per mil) are found in air masses exposed to snow-covered areas, showing that snowpack emissions of NOx from upwind regions can have a significant impact on the local surface budget of reactive nitrogen, in conjunction with interactions with active halogen chemistry. The implications of the results are discussed in light of the potential use of the stable isotopic composition of nitrate to infer atmospherically relevant information from nitrate preserved in ice cores.

(Table 1) Conditions of vertical near-bottom profiling and the main parameters of the benthic boundary layer in several regions of the Black Sea shelf

Measurements of 14 vertical profiles of currents and hydrological parameters in the near-bottom layer with depth resolution of 0.1 m were carried out in several regions of the Black Sea shelf, at five points over the continental slope, and in three deep water regions. The upper boundary of the benthic boundary layer (BBL) was reliably determined at a point at distance from 5-7 to 35-40 m from the bottom where the gradients of density and current velocity changed. Experimental data obtained were used to determine the coefficient of bottom friction, friction velocity, coefficients of vertical diffusion of momentum and density, and vertical fluxes of temperature and salinity in the BBL.

Pollen record from Golkow, Poland

Janczyk-Kopikowa (1966): The series of the organic deposits, developed in the vicinity of Golkow near Warsaw as oil shales and peats, was laid down in a grough valley and now rests on the deposits of the Middle Polish Glaciation (Riss). The organic deposits are overlain by the fluviale deposits of the North Polish Glaciation (Würm). The locality Golkow occurs beyond the extent of the continental glacier of this glaciation. Polen analysis completed by microfloristic examinations allows to determine the age of the organic series that is thought to be Eemian. The pollen diagram from Golkow does not call in question the stratigraphical position of the deposits investigated mainly due to its characteristic features such as minimum content of coniferous trees in the climatic optimum - about 5%, high percentage of Corylus - 77.5% and well developed phase of hornbeam. It may be well compared with other Eemian diagrams from the area of Poland and reveals much similar features. The development of vegetation at Golkow has depended upon the prevailing climate. At first, the cool climate brings about the development of plants having small thermal requirements. Here belong thin, park-like forests with pine and birch (Pinus, Betula) accompanied by the heliophilic plants such as Hippohäe and Ephedra. Improvement of climate that becomes warm and humid provides for development of deciduous forests prevailing in the climatic optimum, of the interglacial. Decrease of temperature causes a repeated change in the type of forest. This latter changes into coniferous forest with prevailing spruce (Picea) and fir (Abies) at the beginning, and then with pine (Pinus) and birch (Betula). During the Eemian Interglacial, the development of plants at Golkow terminates with a new and long-lasting predominance of pine-birch forests. However, such a longevity may be apparent only. Apparent character of this phenomenon is proved by a fact that the pollen spectra of the warm climatic periods have found their reflex in the oil shale that increased considerably slower than the layers off feebly decomposed peat evidencing the existence of cool pine-birch forests from the decline of the Interglacial. The water basin, in which the polen grains were laid down from surrounding plants is characterized by a calm sedimentation as proved by the occurrence of the oil shale. An insignificant water flow left behind some thin sand laminae. The not too deep basin becomes shallower owing to the growing water vegetation, and marshy vegetation. The growing of the plants causes a complete shallowing of the basin and formation of peat bog in situ, as proved by the peat beds occurring in the section. ---- Gadomska (1966): In the vicinity of Golków a series of organic deposits occurs amounting to 6.5-9.3 m in thickness, and consisting of oil shales, lacustrine silts and sands, as well as peats and peaty silts. The organic deposits fill up an old, small, but fairly deep lake basin, probably of finger-lake origin. It may be seen to-day as a slight lowering of the relief, filled up with soaked ground, stretching from north to south. On the basis of palaeobotanical examinations the organic deposits considered are of Eemian Interglacial age (Z. Janczyk-Kopikowa, 1063). The lower part of the organic series consists of a compact oil shale horizon, the maximum thickness of which may attain up to 8 m. The oil shales contain particularly in their upper part, numerous intercalations of arenaceous silts, dark grey or black in colour, or of sands mainly of lacustrine provenance. At the top of the oil shales are found peats, up to 2.5 m in thickness, covered by black, humus silts with numerous plant remains. The Eemian Interglacial deposits are covered by a series of fluviatile sands belonging partly to the Baltic Glaciation (bottom part of the series), partly to the Holocene (top part of the series). The thickness of the sands is 0.5-3.7 m. Higher up, there are found the Holocene and present-day deposits developed as clayey alluvion, or arenaceous slide rocks, or arenaceous-silty soil.

Description of sampling sites in Northern Russia

The youngest ice marginal zone between the White Sea and the Ural mountains is the W-E trending belt of moraines called the Varsh-Indiga-Markhida-Harbei-Halmer-Sopkay, here called the Markhida line. Glacial elements show that it was deposited by the Kara Ice Sheet, and in the west, by the Barents Ice Sheet. The Markhida moraine overlies Eemian marine sediments, and is therefore of Weichselian age. Distal to the moraine are Eemian marine sediments and three Palaeolithic sites with many C-14 dates in the range 16-37 ka not covered by till, proving that it represents the maximum ice sheet extension during the Weichselian. The Late Weichselian ice limit of M. G. Grosswald is about 400 km (near the Urals more than 700 km) too far south. Shorelines of ice dammed Lake Komi, probably dammed by the ice sheet ending at the Markhida line, predate 37 ka. We conclude that the Markhida line is of Middle/Early Weichselian age, implying that no ice sheet reached this part of Northern Russia during the Late Weichselian. This age is supported by a series of C-14 and OSL dates inside the Markhida line all of >45 ka. Two moraine loops protrude south of the Markhida line; the Laya-Adzva and Rogavaya moraines. These moraines are covered by Lake Komi sediments, and many C-14 dates on mammoth bones inside the moraines are 26-37 ka. The morphology indicates that the moraines are of Weichselian age, but a Saalian age cannot be excluded. No post-glacial emerged marine shorelines are found along the Barents Sea coast north of the Markhida line.

Age determination of sediment from Lake Komi

Beach and shoreface sediments deposited in the more than 800-km long ice-dammed Lake Komi in northern European Russia have been investigated and dated. The lake flooded the lowland areas between the Barents-Kara Ice Sheet in the north and the continental drainage divide in the south. Shoreline facies have been dated by 18 optical stimulated luminescence (OSL) dates, most of which are closely grouped in the range 80-100 ka, with a mean of 88 +/- 3 ka. This implies that that the Barents-Kara Ice Sheet had its Late Pleistocene maximum extension during the Early Weichselian, probably in the cold interval (Rederstall) between the Brørup and Odderade interstadials of western Europe, correlated with marine isotope stage 5b. This is in strong contrast to the Scandinavian and North American ice sheets, which had their maxima in isotope stage 2, about 20 ka. Field and air photo interpretations suggest that Lake Komi was dammed by the ice advance, which formed the Harbei-Harmon-Sopkay Moraines. These has earlier been correlated with the Markhida moraine across the Pechora River Valley and its western extension. However, OSL dates on fluvial sediments below the Markhida moraine have yielded ages as young as 60 ka. This suggests that the Russian mainland was inundated by two major ice sheet advances from the Barents-Kara seas after the last interglacial: one during the Early Weichselian (about 90 ka) that dammed Lake Komi and one during the Middle Weichselian (about 60 ka). Normal fluvial drainage prevailed during the Late Weichselian, when the ice front was located offshore.

Mineralogy and diagenesis of slope sediments at DSDP Leg 84 holes

The distribution and composition of minerals in the silt and clay fraction of the fine-grained slope sediments were examined. Special interest was focused on diagenesis. The results are listed as follows. (1) Smectite, andesitic Plagioclase, quartz, and low-Mg calcite are the main mineral components of the sediment. Authigenic dolomite was observed in the weathering zones of serpentinites, together with aragonite, as well as in clayey silt. (2) The mineralogy and geochemistry of the sediments is analogous to that of the andesitic rocks of Costa Rica and Guatemala. (3) Unstable components like volcanic glass, amphiboles, and pyroxenes show increasing etching with depth. (4) The diagenetic alteration of opal-A skeletons from etching pits and replacement by opal-CT to replacement by chalcedony as a final stage corresponds to the typical opal diagenesis. (5) Clinoptilolite is the stable zeolite mineral according to mineral stability fields; its neoformation is well documented. (6) The early diagenesis of smectites is shown by an increase of crystallinity with depth. Only the smectites in the oldest sediments (Oligocene and early Eocene) contain nonexpanding illite layers.