Oceanic stratified euphotic zone as elucidated by 234 Th: 238 U disequilibria1
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چکیده
منابع مشابه
PII S 0016 - 7037 ( 00 ) 00408 - 7 206 Pb – 230 Th – 234 U – 238 U and 207 Pb – 235 U geochronology of Quaternary opal , Yucca Mountain , Nevada
U–Th–Pb isotopic systems have been studied in submillimeter-thick outermost layers of Quaternary opal occurring in calcite–silica fracture and cavity coatings within Tertiary tuffs at Yucca Mountain, Nevada, USA. These coatings preserve a record of paleohydrologic conditions at this site, which is being evaluated as a potential high-level nuclear waste repository. The opal precipitated from gro...
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The (U/ U) ratio in surface waters is generally higher than secular equilibrium due to nuclide recoil during alpha-decay of U. The size of the deviation from secular equilibrium contains information about the environment in which the water is found. This potential tool for environmental reconstruction has previously been studied in rivers, groundwater, and sediment pore-water. Here we conduct a...
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Microbial biomass on suspended organic matter in seawater of the euphotic zone of Saanich Inlet was investigated. The viable microorganisms were measured by the glucose-uptake method. Microbial carbon on particulate organic matter in seawater was determined to be, on the average, 9.9 ,ug of C/liter, and there was a regression relationship as y = 0.0062 x 1.79 with an unbiased variance Vyx12= 0....
متن کاملUN CO RR EC TE D PR OO F Seawater ( 234 U / 238 U ) during the last 800 thousand years
Constraining the history of seawater (234U/238U) is important because this ratio is used to assess the validity of U/ Th ages, and because it provides information about the past rate of physical weathering on the continents. This study makes use of U-rich slope sediments from the Bahamas in an attempt to reconstruct seawater (234U/238U) for the last 800 kyr. For the last 360 kyr, U/Th dating of...
متن کاملNatural fractionation of 238 U / 235 U
The isotopic composition of U in nature is generally assumed to be invariant. Here, we report variations of the U/U isotope ratio in natural samples (basalts, granites, seawater, corals, black shales, suboxic sediments, ferromanganese crusts/ nodules and BIFs) of 1.3‰, exceeding by far the analytical precision of our method ( 0.06‰, 2SD). U isotopes were analyzed with MC-ICP-MS using a mixed U–...
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ژورنال
عنوان ژورنال: Limnology and Oceanography
سال: 1987
ISSN: 0024-3590
DOI: 10.4319/lo.1987.32.1.0189