Growth rates of Fe-Mn nodules and age and sedimentation rates of host sediments from the Southeast Pacific

Growth rates of nine ferromanganese nodules collected from the Southeast Pacific were estimated using the alpha radiogpaphic technigue. Growth rates range from 1 to 16 mm per million years. In three nodules measurements were made on two opposite sides; two of them showed no growth in one of measured directions during the last 300 ky, whereas in the third nodule growth rates on the opposite sides differ by factor 2. Average sedimentation rate of deposits underlying the nodules estimated by the radiocarbon and excess 230Th methods, were 4 mm/1000 years with rather minor variations. Difference between sedimentation rates and nodule growth rates is caused by activity of benthic fauna, as suggested by inversion of radiocarbon dates with depth.

Age and chemical composition of dredged igneous rocks from the Vityaz Ridge, Pacific slope of the Kuril Island Arc

Original results of igneous rock studies are presented. The rocks were dredged during a marine expedition (cruise 37 of R/V Akademik M.A. Lavrent'ev in August-September, 2005) in the region of the submarine Vityaz Ridge and the Kuril Arc outer slope. Several age complexes (Late Cretaceous, Eocene, Late Oligocene, Miocene, and Pliocene-Pleistocene) are recognizable on the Vityaz Ridge. These complexes are characterized by a number of common geochemical features since all of them represent formations of island arc calc-alkali series. At the same time, they also have individual features reflecting different geodynamic settings. The outer slope of the Kuril Arc demonstrates submarine volcanism. Pliocene-Pleistocene volcanic rocks dredged here are similar to volcanites of the Kuril-Kamchatka Arc frontal zone.

(Table 1) K-Ar age and inert-gas-isotopes at DSDP Holes 68-501, 69-504B and 69-505B

Conventional K-Ar ages have been determined and inert-gas abundances have been measured on representative samples of altered rocks from Deep Sea Drilling Project Holes 501, 504B, and 505B in an attempt to correlate their degree of alteration with inert-gas and K-Ar data. Samples taken from the first 60 meters below the sediment/basalt interface give significantly higher ages than would be expected from the magnetic stratigraphy, though at greater depths the calculated ages are in broad agreement with the expected age. The inert gas ratios 20Ne/36Ar, 36Ar/84Kr, and 84Kr/130Xe also show a marked discontinuity at the 60-meter depth, and all these effects are interpreted as being a consequence of low-temperature alteration produced by burial metamorphism and by interaction with sea water (halmyrolysis).

Age and isotopes in bottom sediments from Core VER-99-1-St2, Baikal Lake

A simple, reliable, and efficient method has been elaborated for direct determination of isotopic composition of authigenic uranium in siliceous lacustrine sediments. The method is based on studying kinetics of selective extraction of authigenic uranium from sediments by weak solutions of ammonium hydrocarbonate followed by ICP-MS analysis of nuclides. To estimate contamination of authigenic uranium by terrigenous one contents of 232Th and some other clastogenic elements in the extracts were measured simultaneously. Selectivity of extraction of authigenic uranium from the sediments treated with 1% NH4HCO3 solution appeared to be no worse than 99%. The method was applied to analysis of isotopic composition of authigenic uranium at several key horizons of the earlier dated core from the Baikal Lake. Measurements directly show that 234U/238U values in Baikal water varied depending on climate, which contradicts existing hypotheses. Measured 234U/238U ratios in water of the paleo-Baikal match corresponding values reconstructed from isotopic data for total uranium in the sediments on supposition that U/Th ratio is constant in terrigenous fraction of the sediments. Direct experimental determination of total and authigenic nuclides in sediments enhances potentiality of the method for 234U-230Th dating of non-carbonate lacustrine sediments including those from the Baikal Lake within intervals corresponding to periods of glaciation, when sediments were rich in terrigenous components. Portions of terrigenous and authigenic uranium are well separated and we can study variability of sources of terrigenous matter and refine the earlier model for reconstructing climate humidity in the East Siberia.

(Table 1) Magnetozone boundaries, age and sedimentation rate at DSDP Hole 93-605

Natural Remanent Magnetization (NRM) was measured for regularly spaced samples from the 620-m-thick, lower middle Eocene to upper Maestrichtian section of DSDP Site 605. The total NRM of the Eocene chalks was too low (5-50 µA/m) to establish a reliable magnetic polarity stratigraphy. However, the results from the somewhat more clayrich Paleocene-upper Maestrichtian section are useful. A fourfold quality classification of the results of progressive demagnetization studies aided in determining the polarity of the original remanence. Two types (1 and 2a) showed a Characteristic Remanent Magnetization (ChRM) direction with reversed and normal polarity, respectively; the third type (2b) can be interpreted as having a reversed ChRM, which could not be cleaned, whereas the fourth type (3) is considered to be unreliable. The Site 605 magnetic polarity stratigraphy compares well with published sections, adding important detail to the correlation with planktonic microfossil zones and, hence, to the resolution of this portion of the time scale (C24-C32 on the Berggren et al., 1985, scale). The Cretaceous/Tertiary boundary occurs in a reversed polarity zone that has been correlated with Subchron C29r. We suspect the presence of an unconformity at the boundary between lithostratigraphic Units Va and IV a location which is also the level of Reflection Horizon A*.

Age and chemical composition of volcaniclastic rocks from the Sea of Japan

Petrographic and geochemical studies showed that Oligocene - Early Miocene volcaniclastic rocks from the southern part of the Sea of Japan are ascribed to high-potassium aluminous rocks of sub-alkaline volcanic series from active continental margins. A comparative analysis revealed spatiotemporal relation of Oligocene - Early Miocene subaerial volcanism of the Sea of Japan with Late Cretaceous and Eocene - Early Miocene ignimbrite volcanism of the East Eurasian margin. This allows to refer the volcaniclastic rocks of the Sea of Japan to the stage of ignimbrite volcanism that occurred during relative quiescence against general extension in the continental margin setting.

Old times and new /

Mode of access: Internet.

Medical Advisory Committee report and recommendations on the administration of the OASI disability freeze provision : preservation of rights of individuals with extended total disability, Social security amendments of l954.

"July 1955."

Old masters and new; essays in art criticism,

Reprinted from various periodicals.

Torah in the messianic age and/or the age to come.

Mode of access: Internet.

Five old friends and A young prince,

Title vignette.

Some performance effects of age and low blood alcohol levels on a computerized neuropsychological test.

Federal Aviation Administration, Office of Aviation Medicine, Washington, D.C.

Effects of age and low doses of alcohol on compensatory tracking during angular acceleration.

Federal Aviation Administration, Office of Aviation Medicine, Washington, D.C.

Hearts & arteries : what scientists are learning about age and the cardiovascular system /

Shipping list no.: 95-0031-P.