Retreat of the Laurentide ice sheet tracked by the isotopic composition of Pb in western North Atlantic seawater during termination 1

Gutjahr, Marcus; Halliday, Alex N.; Keigwin, Lloyd D

doi:10.1016/j.epsl.2009.07.020

Cited by 36 publications

(33 citation statements)

References 59 publications

(35 reference statements)

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“…Winter et al (1997) concluded from data from the Alpha Ridge that at ∼3 Ma changes in provenance of the sediments carried by the waters and thus also the isotopic composition of the water itself coincided with a change in sediment transport mechanisms from sea ice to glacial ice caused by the development of the ice sheets on the continents. However, there is evidence that enhanced incongruent weathering during deglacial episodes (Vance et al, 2009;Gutjahr et al, 2009;Kurzweil et al, 2010) has most likely been the dominant process responsible for a shift to more radiogenic dissolved Pb isotope compositions in the western North Atlantic. von Blanckenburg and Nägler (2001) attributed the shift towards more radiogenic Pb isotope compositions beginning at ∼3 Ma recorded by the Fe-Mn crusts of the northwestern Atlantic to the transition from predominantly chemical to mechanical erosion due to the expansion of the ice sheets and enhanced glacial weathering on the North American continent and Greenland.…”

Section: Weathering Inputs From the Surrounding Continentsmentioning

confidence: 95%

The evolution of climatically driven weathering inputs into the western Arctic Ocean since the late Miocene: Radiogenic isotope evidence

Dausmann

Siebert

Christl

et al. 2015

Earth and Planetary Science Letters

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Section: Weathering Inputs From the Surrounding Continentsmentioning

confidence: 95%

The evolution of climatically driven weathering inputs into the western Arctic Ocean since the late Miocene: Radiogenic isotope evidence

Dausmann

Siebert

Christl

et al. 2015

Earth and Planetary Science Letters

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“…Previous studies of seawater Pb isotopes over the last glacial termination observed pronounced increases for all three Pb isotope systems [17][18][19][20] , which were interpreted as incongruent weathering of freshly eroded and exposed material on North America. Although our study focuses on weathering changes during glacial initiation rather than deglaciation, we also observe increasing seawater 206,207,208 Pb/ 204 Pb values across the glacial transition; albeit less pronounced variations than at Termination I.…”

mentioning

confidence: 96%

Antarctic weathering and carbonate compensation at the Eocene–Oligocene transition

Basak

Martin

2013

Nature Geosci

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During the Eocene-Oligocene transition about 34 million years ago, permanent ice cover developed on Antarctica. This pronounced climate transition was accompanied by the deepening of the carbonate compensation depth in the oceans 1 and perturbations in atmospheric carbon dioxide concentrations 2,3 . These changes may have been linked to continental weathering on Antarctica, but reconstructing which rock types were subject to weathering and the intensity of that weathering has proved challenging. Here we compare the lead (Pb) isotope values of seawater as recorded by extractions from decarbonated bulk sediments and those of silicate detrital fractions from deep-sea sediments from sites in the Southern Ocean that span the Eocene-Oligocene transition. These comparisons allowed us to assess local weathering inputs of Pb from Antarctica. The 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios suggest high rates of chemical weathering in the late Eocene, which would have helped draw down atmospheric CO 2 to levels necessary for glacial initiation. Mechanical weathering and the introduction of newly exposed material was enhanced during the establishment of the Antarctic ice sheet. We also observe a divergence of seawater 206 Pb/ 204 Pb from detrital values during the Eocene-Oligocene transition, which implies an additional source of weathered material. We argue that the weathering of carbonate basement rock from Antarctica could explain the 206 Pb/ 204 Pb trend, and could have contributed to the observed deepening of the carbonate compensation depth through contributions to ocean alkalinity.Weathering of silicate rock is a key component of the longterm carbon cycle. Previous studies demonstrated that incongruent chemical weathering of fresh silicate material produces weathering solutions with Pb isotopes that are more radiogenic than the parent source rocks owing to preferential release of radiogenic Pb from accessory minerals and/or sites of radiation damage 4-6 . In contrast, extensive congruent chemical weathering of older continental silicates/soils produces weathering solutions with Pb isotopic signatures that are similar to the parent rock composition. Applying a new approach, Pb isotopes of seawater and deep sea silicates extracted from southern Ocean Drilling Program sites represent weathering solutions and parent source materials respectively from Antarctica during the Eocene-Oligocene transition (EOT). Differences between these two proxies are interpreted in terms of weathering on Antarctica, which may have contributed to global processes marking the EOT.Seawater 206,207,208 Pb/ 204 Pb isotope ratios (representing weathering solutions) were extracted from decarbonated bulk deep sea sediment from Ocean Drilling Program sites 689 (64.. 2,080 m; Supplementary Fig. S1) and 738 (62.7 • S, 82.8 • E, 2,253 m; Supplementary Fig. S1) using a reducing hydroxylamine hydrochloride solution 7,8 . The remaining silicate detrital fractions (assumed to represent parent rock compositions) were then dissolved and both fra...

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“…The lead isotope composition of seawater is preserved in authigenic deposits, for example authigenic FeMn oxyhydroxides, that can be separated and studied using a selective leaching technique (Gutjahr et al, 2009(Gutjahr et al, , 2007. The variation in Pb isotope composition of these FeMn rich marine deposits can, in turn, be associated with increased continental export fluxes through iceberg calving at ice sheet margins.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Pb isotope ratios for the residues are generally lower than the corresponding leachates (Crocket et al, 2013;Gutjahr et al, 2009;Kurzweil et al, 2010). In both cores 149 and 151…”

Section: Pb Sr and Nd In Detrital Fractionmentioning

confidence: 99%

“…Complementary to the detrital investigations, the Pb isotopic composition in marine authigenic precipitates are used to reconstruct water mass circulation and continental weathering fluxes (Crocket et al, 2012;Foster and Vance, 2006;Gutjahr et al, 2009;Kurzweil et al, 2010;von Blanckenburg and Nägler, 2001). The dissolved Pb isotope composition in the water column is determined by the style of continental physical erosion and chemical weathering (Christensen et al, 1997;von Blanckenburg and Nägler, 2001) as a result of the preferential release of radiogenic Pb, relative to common Pb, during the incipient stages of continental chemical weathering (Erel and Morgan, 1992;Harlavan and Erel, 2002).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

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Weathering fluxes and sediment provenance on the SW Scottish shelf during the last deglaciation

et al. 2018

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Retreat of the Laurentide ice sheet tracked by the isotopic composition of Pb in western North Atlantic seawater during termination 1

Cited by 36 publications

References 59 publications

The evolution of climatically driven weathering inputs into the western Arctic Ocean since the late Miocene: Radiogenic isotope evidence

The evolution of climatically driven weathering inputs into the western Arctic Ocean since the late Miocene: Radiogenic isotope evidence

Antarctic weathering and carbonate compensation at the Eocene–Oligocene transition

Weathering fluxes and sediment provenance on the SW Scottish shelf during the last deglaciation

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