Quaternary climate modulation of Pb isotopes in the deep Indian Ocean linked to the Himalayan chemical weathering

Wilson, David J.; Galy, Αlbert; Piotrowski, Alexander M; Banakar, V.K.

doi:10.1016/j.epsl.2015.05.014

Cited by 21 publications

(18 citation statements)

References 83 publications

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“…The Pb isotope data were obtained using the nondecarbonated leach technique, but the absence of detrital Pb isotope data does not allow the evaluation of a possible detrital contamination from pore waters. However, the very high particle reactivity of Pb makes any mobilization from pore waters highly unlikely and the leaching method has been shown to yield reliable seawater Pb isotope data [ Gutjahr et al ., ; Stumpf et al ., ; Crocket et al ., ; Wilson et al ., ; Teschner et al ., ] and the consistent glacial‐interglacial variations, as well as the close agreement of our Pb isotope results with the ferromanganese crust data of Abouchami and Goldstein [] for the same region support the validity of our results.…”

Section: Discussionmentioning

confidence: 99%

Reduced admixture of North Atlantic Deep Water to the deep central South Pacific during the last two glacial periods

et al. 2016

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The South Pacific is a sensitive location for the variability of the global oceanic thermohaline circulation given that deep waters from the Atlantic Ocean, the Southern Ocean, and the Pacific basin are exchanged. Here we reconstruct the deep-water circulation of the central South Pacific for the last two glacial cycles (from 240,000 years ago to the Holocene) based on radiogenic neodymium (Nd) and lead (Pb) isotope records complemented by benthic stable carbon data obtained from two sediment cores located on the flanks of the East Pacific Rise. The records show small but consistent glacial/interglacial changes in all three isotopic systems with interglacial average values of -5.8 and 18.757 for ε Nd and 206

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Section: Discussionmentioning

confidence: 99%

Reduced admixture of North Atlantic Deep Water to the deep central South Pacific during the last two glacial periods

et al. 2016

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“…Important sources for both dissolved Nd and Pb in seawater are eolian and riverine inputs [e.g., Frank , , and references therein], as well as boundary exchange with the continental shelf sediments, during which the Nd and Pb isotopic compositions of the bottom waters near the continental margins can be significantly modified [e.g., Jeandel et al ., ; Lacan and Jeandel , ; Wilson et al ., , ]. It is still not well understood, however, which exact mechanisms control such changes of the Nd isotopic composition of the bottom waters and which sediment phases are involved.…”

Section: Introductionmentioning

confidence: 94%

“…In addition, planktonic foraminifera and their authigenic ferromanganese coatings were applied for the reliable reconstruction of the Nd isotope composition of bottom waters [Roberts et al, 2010Piotrowski et al, 2012;Kraft et al, 2013;Tachikawa et al, 2014]. Lead (Pb) has a much shorter residence time of only about 50 years in the Atlantic Ocean [Schaule and Patterson, 1981;Erel et al, 1994] and therefore provides a more localized dissolved seawater signal mainly reflecting the erosional input from nearby continental rocks and exchange processes with the continental margins [Frank, 2002;Gutjahr et al, 2009;Crocket et al, 2013;Wilson et al, 2015]. In addition, Pb experiences pronounced incongruent weathering as a consequence of the α-recoil effect causing fractionation of the Pb isotopes during formation of the chemical weathering solutions prior to transport to the oceans.…”

Section: Tracing Water Masses With Radiogenic Nd and Pb Isotopesmentioning

confidence: 99%

“…Lead (Pb) has a much shorter residence time of only about 50 years in the Atlantic Ocean [ Schaule and Patterson , ; Erel et al ., ] and therefore provides a more localized dissolved seawater signal mainly reflecting the erosional input from nearby continental rocks and exchange processes with the continental margins [ Frank , ; Gutjahr et al ., ; Crocket et al ., ; Wilson et al ., ]. In addition, Pb experiences pronounced incongruent weathering as a consequence of the α ‐recoil effect causing fractionation of the Pb isotopes during formation of the chemical weathering solutions prior to transport to the oceans.…”

Section: Introductionmentioning

confidence: 99%

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Plio-Pleistocene evolution of water mass exchange and erosional input at the Atlantic-Arctic gateway

2016

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Water mass exchange between the Arctic Ocean and the Norwegian-Greenland Seas has played an important role for the Atlantic thermohaline circulation and Northern Hemisphere climate. We reconstruct past water mass mixing and erosional inputs from the radiogenic isotope compositions of neodymium (Nd), lead (Pb), and strontium (Sr) at Ocean Drilling Program site 911 (leg 151) from 906 m water depth on Yermak Plateau in the Fram Strait over the past 5.2 Myr. The isotopic compositions of past bottom waters were extracted from authigenic oxyhydroxide coatings of the bulk sediments. Neodymium isotope signatures obtained from surface sediments agree well with present-day deepwater ε Nd signature of À11.0 ± 0.2. Prior to 2.7 Ma the Nd and Pb isotope compositions of the bottom waters only show small variations indicative of a consistent influence of Atlantic waters. Since the major intensification of the Northern Hemisphere Glaciation at 2.7 Ma the seawater Nd isotope composition has varied more pronouncedly due to changes in weathering inputs related to the waxing and waning of the ice sheets on Svalbard, the Barents Sea, and the Eurasian shelf, due to changes in water mass exchange and due to the increasing supply of ice-rafted debris (IRD) originating from the Arctic Ocean. The seawater Pb isotope record also exhibits a higher short-term variability after 2.7 Ma, but there is also a trend toward more radiogenic values, which reflects a combination of changes in input sources and enhanced incongruent weathering inputs of Pb released from freshly eroded old continental rocks.

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“…The records presented here are, to the best of our knowledge, the first evidence that authigenic Pb isotope records preserve precessional cyclicity. Other locations, which might have been expected to show similar frequencies, have not (for example, the Indian Ocean; Wilson et al, ). This suggests the phenomenon may be restricted to the Mediterranean, though since Neogene stratigraphy is pinned exclusively to Mediterranean sediments, this result has global implications.…”

Section: Discussionmentioning

confidence: 99%

Precessional Cyclicity of Seawater Pb Isotopes in the Late Miocene Mediterranean

Modestou

Gutjahr

Schee

et al. 2019

Paleoceanog and Paleoclimatol

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Astronomical tuning in the Mediterranean region is primarily based on organically-mediated proxies, such as cyclicity of organic rich layers or changes in foraminiferal assemblages. Both during and post deposition, organic proxies can be affected by complex processes not immediately related to the changes in precession (insolation) they are assumed to reflect. Here we present an isotopic proxy which exhibits precessional cyclicity yet is inorganic. Seawater lead (Pb) isotope records over four precessional cycles between 6.6 and 6.5 Ma, from bulk sediment leachates of three Messinian, circum-Mediterranean marginal locations, show variations consistent with precessional cyclicity. During insolation minima, the Pb isotope signatures from all three sites converge to similar values, suggesting a regional process is affecting all three locations at that time. Data from the marginal sites are compared with new data from ODP Site 978 and published data from a variety of geological archives from the Mediterranean region to determine the mechanism(s) causing the observed variability. While the comparisons are not fully conclusive, the timing of events suggest that increased dust production from North Africa during insolation minima is the most likely control. This hypothesis implies that authigenic marine Pb isotope records have the potential to provide a reliable inorganic tie point for Mediterranean cyclostratigraphy where sub-precessional resolution is required. An inorganic tie point could also provide the means to resolve long-standing problems in Mediterranean stratigraphy on precessional and sub-precessional timescales which have been obscured due to post-depositional changes (e.g., sapropel burn-down) or suboptimal ecological conditions (e.g., the Messinian Salinity Crisis). Plain Language SummaryResearch into the geological and climate history of the Mediterranean region has been important globally, partly because the geologic timescale, back to about 23 million years ago, is pinned to the geological record of this region and partly because the water exiting the Mediterranean into the Atlantic is an important component of global ocean circulation. In this paper, we examine changes through time in the isotope ratios of the trace metal lead (Pb), which is present in tiny amounts even in unpolluted seawater. Our Pb isotope records, covering~100 thousand years at about 6.5 million years ago, show distinctive regular cyclicity with time, with "peaks" at approximately 20 thousand year intervals. We hypothesize that wet-dry climate cycles in North Africa produced these peaks by supplying more dust to the Mediterranean during the driest part of the cycle, when Pb from dust would have more strongly influenced the seawater Pb isotope composition. This hypothesis is exciting because it suggests that seawater Pb isotopes have the potential to improve our understanding of the passage of time in the Mediterranean region, in particular at times and locations where existing techniques are inadequate.

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Quaternary climate modulation of Pb isotopes in the deep Indian Ocean linked to the Himalayan chemical weathering

Abstract: We use reductive sediment leaching to extract lead (Pb) from the authigenic fraction 3 of marine sediments and reconstruct the Pb isotope evolution of the deep central Indian Ocean 4 over the past 250 thousand years at ~3 kyr resolution.

Cited by 21 publications

References 83 publications

Reduced admixture of North Atlantic Deep Water to the deep central South Pacific during the last two glacial periods

Reduced admixture of North Atlantic Deep Water to the deep central South Pacific during the last two glacial periods

Plio-Pleistocene evolution of water mass exchange and erosional input at the Atlantic-Arctic gateway

Precessional Cyclicity of Seawater Pb Isotopes in the Late Miocene Mediterranean

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