Accumulation models of230Th and231Pa in deep sea sediments

Osmond, J.K.

doi:10.1016/0012-8252(79)90024-2

Cited by 19 publications

(5 citation statements)

References 90 publications

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“…The U and Th isotopes are listed in Table 2, in which the values are similar and the 230 Th content gradually decreased to the bottom, generally fulfilling the base of 230 Th-excess dating (Osmond, 1979;Xia, 1989;Edwards et al, 2003). Assuming that 230 Th ex flux is constant over the time of deposition, 230 Th ex decays exponentially with the depths, and the slope coefficient of the regression represents the sedimentation rate (Scholten et al, 1994).…”

Section: Th Resultsmentioning

confidence: 80%

Geochronology and Paleoenvironmental Changes of Late Pleistocene Sediments in the Ross Sea, Antarctica

Bu¹,

Long²,

Hu³

et al. 2022

Front. Earth Sci.

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The palaeoceanographic studies are largely limited by poor carbonate preservation in high-latitude regions. To improve our knowledge in this key area, we studied a sediment core (ANT32-RA05C) in terms of paleomagnetic and 230Th dating and geochemical properties, collected from the continental slope of the Ross Sea, Antarctica. The two major results are as follows: 1) the sedimentation rate based on 230Th isotopes is 1.37 cm/kyr, agreeing well with the correlation of the relative paleomagnetic intensity of the core ANT32-RA05C to changes in Earth’s magnetic intensity and 2) the sediments contain ice-rafted debris (IRD) over 30%, with a considerable contribution of siliceous deposits. Integrating geochronological and geochemical properties of the studied core, a correlation of the regional paleoenvironmental process to the EPICA Dome C (EDC) Antarctic temperature is established, inferring that the IRD input and primary productivity are both enhanced in a warm climate. Moreover, a leading phase of biogenic processes to changes in the ice sheet in the Ross Ice Shelf is observed, highlighting a dominant role of the oceanic circulation in the ice-sheet retreat during the last deglaciation. Overall, the sedimentary record in the Ross Sea documents some key features of the paleoenvironmental processes in the Late Pleistocene, which could be correlated with large-scale changes in Antarctica and thus are worthy of further investigation in the future.

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Section: Th Resultsmentioning

confidence: 80%

Geochronology and Paleoenvironmental Changes of Late Pleistocene Sediments in the Ross Sea, Antarctica

Bu¹,

Long²,

Hu³

et al. 2022

Front. Earth Sci.

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“…Both 230 Th and 231 Pa are fractionated from soluble U isotopes by ready adsorption onto the surfaces of detrital grains (e.g., clay minerals). Thus, at the oceanic sediment-water interface both 230 Th and 231 Pa are unsupported (out of secular equilibrium, or in excess) by their parent U isotopes, and thereafter decay to their own daughter products (e.g., Osmond, 1979;Dickin, 1997;Henderson and Anderson, 2003). Consequently, time-dependent dose-rate terms must be incorporated into the luminescence age equation (Huntley and Wintle, 1981;Huntley et al, 1986) for open-ocean sediments.…”

Section: Basic Concepts Of Luminescence Sediment Datingmentioning

confidence: 99%

Zeroing tests of luminescence sediment dating in the Arctic Ocean: Review and new results from Alaska-margin core tops and central-ocean dirty sea ice

Berger

2009

Global and Planetary Change

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“…The early history of this field has been reviewed by several authors (Ku, 1966(Ku, , 1976Thomson and Halton, 1972;Goldberg and Bruland, 1974;Osmond, 1979).…”

Section: Half-lives Arementioning

confidence: 99%

“…(230TI1 unsupported by its uranium parent) method of determining -17-sedimentation rates \.¡ere wen known (see Ku, 1976, andOsmond, 1979, for 230 1'h from seawater au,d variable sedimentation rates, were also discussed by Piggot and Urry (1942a). Kroll (1953Kroll ( , 1954 showed tha t…”

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confidence: 98%

The marine geochemistry of thorium and protactinium

Anderson¹

1980

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Suspended particulate matter was collected by sediment traps deployed in the Sargasso Sea (Site 82), the north equatorial Atlantic (Site E), the north equatorial Pacific (Site p), and the Panama Basin (STIE Site). Additional samples of suspended particles were obtained by in situ filtration at Site F., at the STIE Site, and in the GuatemalaBasin. Concentrations of dissolved Tn and Pa were determined by extraction onto manganese dioxide adsorbers at Site P, at a second site in the Sargasso Sea (Site D), at the STIE Site and in the Guatemala Basin. Sediment samples were obtained from cores taken near Sites E and P.Resul ts have shown uneauiv~cally that suspended particulate matter in the open ocean preferentially scavenges rh relative to Pa. This behavior could not Mave been predicted from the kno\m physical chemistry of Th and Pa. Dissolved 230Thl231pa activity ratios \.¡ere 3-5 at Sites P and D Particulate 230Th/23lpa ratios _,,!ere negatively correlated \i7ith the concentra tion of suspended particles. However, variable scavenging rates, as indicated by variable particle concentration, do not completely control the ratio at which 'Th and Pa are scavenged from solution. Major biogenic and inorganic components of trapped material were found in approximately the same proportions in the STIF. samples and in samples from Sites E and S2' Lower 230rh/23lpa ratios found in the SrIE samples must therefore result from subtle changes in the chemical properties of the particles. Consideration of 230Thl23lpa ratios in several depositional environments indicates that no single factor controls the ratio at which Th and Pa are adsorbed from seawater.Fluxes of 210'th and 2jlpa were less than their rates of production' in the overlying w'ater column in every trap at Sites S2, E,-3-and P. In the Panama .Basin, fluxes measured with the same traps ..¡ere greater than or tqual to their rates of production. These resul ts are a strong indication that even exti:emely reactive elements such as Th and Pa are redistributed within the oceans. Redistribution occurs because variable scavenging rates in different environments set up horizontal concentration gradients. Horizontal mixiug processes produce a net horizonUll transport of Tl: and Pa from areas of 10",1 scavenging -i-ates to areas of high scavengi,ng rates. Protactinium is redistrihuted to a gn:ater extent than Th. Fluxes of 230'1h can be used to set 1.ot"re1. 1 imits for liorizoiital transport of Pa even when absolute trapping efficiencies of the sediment traps are not known. Less than 50% of the Pa produced d t the open ocean sites is removed from the ""rater col uwn by scavenging to settling particles The remainder is removed by horizontal transport to other environments.At Sites E and P, 230'1h/23lpa ratios were identical in the deepest sediment tn1p sample and in surface sediments. Ho¡,rever, 230Th/232Tli and 23Lp~/232ih ratios were 2.5tirnes higher in trapped particlE!S than in surface sediments. The 2301'0/232'10 ratios "..ere 5.5 times higli.sr in particles filtered...

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Accumulation models of230Th and231Pa in deep sea sediments

Cited by 19 publications

References 90 publications

Geochronology and Paleoenvironmental Changes of Late Pleistocene Sediments in the Ross Sea, Antarctica

Geochronology and Paleoenvironmental Changes of Late Pleistocene Sediments in the Ross Sea, Antarctica

Zeroing tests of luminescence sediment dating in the Arctic Ocean: Review and new results from Alaska-margin core tops and central-ocean dirty sea ice

The marine geochemistry of thorium and protactinium

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