Recent dynamics of subarctic dunes as determined by tree-ring analysis of white spruce, Hudson Bay, Québec

The radial-growth patterns of white spruce were studied on a number of trees growing in subarctic dunes along the eastern coast of Hudson Bay to calculate the rates of accumulation, erosion, and migration of cold-climate sand dunes. The average rate of sand accumulation in sheltered dunes (forest sites) was 2.5 to 3.3 cm/yr, which is two to three times lower than in highly exposed dunes with a rate of sedimentation of 7.65 cm/yr. The average erosion rate was 1.4–1.7 cm/yr, about two times lower than the accumulation rate. The migration rate of sheltered dunes was 18 to 30 cm/yr, three to five times lower than for an exposed dune which advanced at a speed of 74 cm/yr. This migration rate established for highly exposed dunes in the Subarctic with tree-ring methods is about 10 times lower than that established for a barchan in the Sahara with other methods.     

Volkhovite: A new type of tektite-like glass

Volkhovites are tektite-like glasses of mafic and ultramafic composition discovered in the fluvioglacial drift of the Valdai glaciation (10–60 ka ago) along the right bank of the Volkhov River (59°27′ N, 32°01′ E). Volkhovite particles are small in size (0.1–3.0 mm) and irregular in shape, with various microtektite aerodynamics (globular, droplike, and dumbbell-like forms). They are perfectly preserved, and, thus, postglacial in age. Sporadic volkhovite grains (up to 20 items per 1 kg of loam) were detected over an area 1.0 × 1.5 km². Some samples from local spots 20 × 30 m² in size are anomalously enriched, up to 1700 volkhovite grains per 1 kg of loam. Tiny Ti-Fe, Fe, and Cu-Au spherules, particles of quenched glass and cinder, and fragments of the Precambrian and Paleozoic rocks are spatially associated with volkhovites. The suggested cryptomagmatic model assumes that the glass and cinder are pre-Holocene in age, whereas volkhovites were formed in the post-glacial time as a result of the outburst of the slag-stone-melt-mud-gas mixture that ascended from the asthenosphere to the surface. Drops of the melt solidified in the air instantaneously to form tectite-like glasses, and the tuffisite-like agglomerate mixed with the fluvioglacial drift.     

Corundum with Inclusions of Extremely Reduced Minerals from Explosive Rocks of the Ukrainian Shield

Doklady Earth Sciences - A study of specific aggregates of corundum from kimberlite and lamproite of the Ukrainian Shield has been carried out. The presence of unusual segregations of oxides,...     

The East Caledonian Current: A Case Example for the Intercomparison between AltiKa and In Situ Measurements in a Boundary Current

This paper presents an assessment of SARAL/AltiKa satellite altimeter for the monitoring of a tropical western boundary current in the south-western Pacific Ocean: the East Caledonian Current. We compare surface geostrophic current estimates obtained from two versions of AltiKa along-track sea level height (AVISO 1 Hz and PEACHI 40 Hz) with two kinds of dedicated in situ datasets harvested along the satellite ground tracks: one deep-ocean current-meter mooring deployed in the core of the boundary current and five glider transects. It is concluded that the AltiKa-derived current successfully captures the velocity of the boundary current, with a standard error of 11 cm/s with respect to the in situ data. It also appears important to reference AltiKa sea level anomaly to the latest mean dynamic topography available in our area. Doing so, Ka-band altimetry provides a satisfactory representation of the western boundary current. Thereby, it usefully contributes to observing its variability in such a remote and under-observed ocean region. However, the rather long repeat period of SARAL (35 days) in comparison to the high frequency variability seen in the flow velocity of the boundary current calls for a combined use of SARAL with the other satellite altimetry missions.     

The age of Spitsbergen basement consolidation: U–Pb dating of detrital zircons from the Upper Precambrian and Lower Carboniferous clastic rocks of the northwestern part of Nordenskiöld Land

The age distribution of detrital zircons from Upper Riphean and Early Carboniferous sandstones of the northwest part of Nordenskiöld Land (Spitsbergen Island) was studied. The results obtained supplement the previously known data on the rocks of Precambrian and Paleozoic masses of West Spitsbergen. Integrated consideration of these data showed that the time interval from the Middle Riphean to the Early Carboniferous inclusive might be subdivided into at least five stages characterized by quite different provinces supplying detritus to sedimentary basins. (The relics of these latter are represented in the present structure of western Svalbard.) The most ancient distinguished event of alteration of the sources of sedimentary matter (at the boundary of the Middle and Late Riphean) corresponds to the consolidation time of the ancient basement of Svalbard.     

Lethal and estrogenic effects of 4-nonylphenol in the cockle Cerastoderma glaucum

The lethal and sublethal effects of the xenoestrogen 4-nonylphenol (NP) were evaluated in the cockle Cerastoderma glaucum. In a 96-h lethality test, bivalves were exposed to 0, 0+ acetone, 0.19, 0.38, 0.75, 1.5 and 3.0 mg NP/l. The 96-h LC₅₀ value was 0.3 mg NP/l. No mortality was observed at 0.1 mg NP/l. The potential estrogenicity of NP was studied in both sexually undifferentiated (resting phase) and differentiated (pre-spawning phase) cockles, exposed for 7 and 14 days to 0, 0+ acetone, 0.0125, 0.025, 0.05, and 0.1 mg NP/l. Vitellogenin (Vg)-like protein levels were determined in both haemolymph and digestive gland by the alkali-labile phosphate (ALP) assay. In the resting phase, exposure for 7 days to 0.1 mg NP/l resulted in significant increases in ALP in both haemolymph and digestive gland, compared with controls. A significant increase was also observed in digestive gland of animals exposed to 0.0125 mg NP/l-exposed animals. After 14 days of exposure, haemolymph ALP levels were significantly increased in exposed animals at all NP concentrations tested, whereas no difference was recorded in digestive gland. In the pre-spawning phase, exposure for 7 days to NP significantly increased ALP levels in haemolymph from males exposed at all NP concentrations tested, whereas no significant variations were found in haemolymph from females. NP (0.05 and 0.1 mg/l) was also shown to increase ALP concentrations significantly in digestive gland of males, but not in those of females. Likewise, after 14 days’ exposure, ALP levels significantly increased in haemolymph from males only at 0.1 mg NP/l. Conversely, NP caused significant increases in ALP levels in digestive gland from both males (at all NP concentrations tested) and females (at 0.025 and 0.1 mg NP/l). These results demonstrate that NP induces Vg synthesis in C. glaucum. Interestingly, males were more responsive to NP than females.