Thorium 230 profiling in deep-sea sediments: high-resolution records of flux and dissolution of carbonate in the equatorial Atlantic during the last 24 000 years

R. Francois, M. P. Bacon, Daniel O Suman

Research output: Contribution to journalArticle

159 Citations (Scopus)

Abstract

Variations in carbonate flux and dissolution, which occurred in the equatorial Atlantic during the last 24 000 years, have been estimated by a new approach that allows the point-by-point determination of paleofluxes to the seafloor. An unprecedented time resolution can thus be obtained which allows sequencing of the relatively rapid events occurring during deglaciation. The method is based on observations that the flux of unsupported 230Th into deep-sea sediments is nearly independent of the total mass flux and is close to the production rate. Thus excess 230Th activity in sediments can be used as a reference against which fluxes of other sedimentary components can be estimated. The study was conducted at two sites (Ceara Rise; western equatorial Atlantic, and Sierra Leon Rise; eastern equatorial Atlantic) in cores raised from three different depths at each site. From measurements of 230Th and CaCO3, changes in carbonate flux with time and depth were obtained. A rapid increase in carbonate production, starting at the onset of deglaciation, was found in both areas. This event may have important implications for the postglacial increase in atmospheric CO2 by increasing the global carbonate carbon to organic carbon rain ratio and decreasing the alkalinity of surface waters (and possibly the North Atlantic Deep Water). -from Authors

Original languageEnglish (US)
Pages (from-to)761-787
Number of pages27
JournalPaleoceanography
Volume5
Issue number5
StatePublished - 1990
Externally publishedYes

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thorium isotope
deep-sea sediment
dissolution
carbonate
deglaciation
North Atlantic Deep Water
Postglacial
alkalinity
seafloor
organic carbon
surface water
carbon
sediment

ASJC Scopus subject areas

  • Oceanography
  • Palaeontology

Cite this

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title = "Thorium 230 profiling in deep-sea sediments: high-resolution records of flux and dissolution of carbonate in the equatorial Atlantic during the last 24 000 years",
abstract = "Variations in carbonate flux and dissolution, which occurred in the equatorial Atlantic during the last 24 000 years, have been estimated by a new approach that allows the point-by-point determination of paleofluxes to the seafloor. An unprecedented time resolution can thus be obtained which allows sequencing of the relatively rapid events occurring during deglaciation. The method is based on observations that the flux of unsupported 230Th into deep-sea sediments is nearly independent of the total mass flux and is close to the production rate. Thus excess 230Th activity in sediments can be used as a reference against which fluxes of other sedimentary components can be estimated. The study was conducted at two sites (Ceara Rise; western equatorial Atlantic, and Sierra Leon Rise; eastern equatorial Atlantic) in cores raised from three different depths at each site. From measurements of 230Th and CaCO3, changes in carbonate flux with time and depth were obtained. A rapid increase in carbonate production, starting at the onset of deglaciation, was found in both areas. This event may have important implications for the postglacial increase in atmospheric CO2 by increasing the global carbonate carbon to organic carbon rain ratio and decreasing the alkalinity of surface waters (and possibly the North Atlantic Deep Water). -from Authors",
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T1 - Thorium 230 profiling in deep-sea sediments

T2 - high-resolution records of flux and dissolution of carbonate in the equatorial Atlantic during the last 24 000 years

AU - Francois, R.

AU - Bacon, M. P.

AU - Suman, Daniel O

PY - 1990

Y1 - 1990

N2 - Variations in carbonate flux and dissolution, which occurred in the equatorial Atlantic during the last 24 000 years, have been estimated by a new approach that allows the point-by-point determination of paleofluxes to the seafloor. An unprecedented time resolution can thus be obtained which allows sequencing of the relatively rapid events occurring during deglaciation. The method is based on observations that the flux of unsupported 230Th into deep-sea sediments is nearly independent of the total mass flux and is close to the production rate. Thus excess 230Th activity in sediments can be used as a reference against which fluxes of other sedimentary components can be estimated. The study was conducted at two sites (Ceara Rise; western equatorial Atlantic, and Sierra Leon Rise; eastern equatorial Atlantic) in cores raised from three different depths at each site. From measurements of 230Th and CaCO3, changes in carbonate flux with time and depth were obtained. A rapid increase in carbonate production, starting at the onset of deglaciation, was found in both areas. This event may have important implications for the postglacial increase in atmospheric CO2 by increasing the global carbonate carbon to organic carbon rain ratio and decreasing the alkalinity of surface waters (and possibly the North Atlantic Deep Water). -from Authors

AB - Variations in carbonate flux and dissolution, which occurred in the equatorial Atlantic during the last 24 000 years, have been estimated by a new approach that allows the point-by-point determination of paleofluxes to the seafloor. An unprecedented time resolution can thus be obtained which allows sequencing of the relatively rapid events occurring during deglaciation. The method is based on observations that the flux of unsupported 230Th into deep-sea sediments is nearly independent of the total mass flux and is close to the production rate. Thus excess 230Th activity in sediments can be used as a reference against which fluxes of other sedimentary components can be estimated. The study was conducted at two sites (Ceara Rise; western equatorial Atlantic, and Sierra Leon Rise; eastern equatorial Atlantic) in cores raised from three different depths at each site. From measurements of 230Th and CaCO3, changes in carbonate flux with time and depth were obtained. A rapid increase in carbonate production, starting at the onset of deglaciation, was found in both areas. This event may have important implications for the postglacial increase in atmospheric CO2 by increasing the global carbonate carbon to organic carbon rain ratio and decreasing the alkalinity of surface waters (and possibly the North Atlantic Deep Water). -from Authors

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