Improved determination of marine sedimentation rates using 230Thxs

Bourne, Mark D.; Thomas, Alexander L.; Niocaill, Conall Mac; Henderson, Gideon M.

doi:10.1029/2012gc004295

Cited by 30 publications

(39 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Lithogenic contributions to the total bulk concentration of 231 Pa and 230 Th were corrected by applying a detrital 238 U/ 232 Th activity ratio of 0.4 based on the lower ranges of bulk 238 U/ 232 Th from GeoB16206‐1 and the nearby GeoB16202‐1 [ Mulitza et al ., ] following the approach by Bourne et al . [] considering local values rather than basin wide averages. The uncertainty of the lithogenic background of the bulk 238 U/ 232 Th (0.4) has been accounted for by assuming an error of ±0.05 (based on the difference to the lowest measured total 238 U/ 232 Th at GeoB16206‐1 of 0.45), which has been included into the error propagation for the resulting 231 Pa/ 230 Th.…”

Section: Methodsmentioning

confidence: 88%

Variability in mid‐depth ventilation of the western Atlantic Ocean during the last deglaciation

et al. 2017

View full text Add to dashboard Cite

Negative stable carbon isotopic excursions have been observed throughout most of the mid‐depth (~1000–3000 m) Atlantic Ocean during Heinrich Stadial 1 (HS1) and the Younger Dryas (YD). Although there is an agreement that these mid‐depth excursions were in some way associated with a slowdown of the Atlantic Meridional Overturning Circulation (AMOC), there is still no consensus on the precise mechanism(s). Here we present benthic stable carbon and oxygen isotopic (δ13C and δ18O) records from five cores from the western equatorial Atlantic (WEA). Together with published benthic isotopic records from nearby cores, we produced a WEA depth transect (~800–2500 m). We compare HS1 and YD data from this transect with data from previously published North and South Atlantic cores and demonstrate that the largest negative δ13C excursions occurred in the WEA during these times. Moreover, our benthic δ18O records require the presence of two water masses flowing from the Southern Ocean, bisected by a Northern Component Water (NCW). Given that δ18O is a conservative water mass tracer, we suggest that δ13C was decoupled from water mass composition and does not correspond to simple alternations between northern and southern sourced waters. Instead, δ13C behaved non‐conservatively during HS1 and the YD. Consistently with our new 231Pa/230Th record from the WEA transect, that allowed the reconstruction of AMOC strength, we hypothesize that the negative δ13C excursions reflect an increase in the residence time of NCW in response to a weakened AMOC, allowing for a marked accumulation of 13C‐depleted respired carbon at the mid‐depth WEA.

show abstract

Section: Methodsmentioning

confidence: 88%

Variability in mid‐depth ventilation of the western Atlantic Ocean during the last deglaciation

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The corrections for detrital and authigenic contributions to ( 231 Pa/ 230 Th) xs, 0 followed the method of Henderson and Anderson [] refined by the suggestions by Bourne et al [].…”

Section: Methodsmentioning

confidence: 99%

“…Bourne et al [] noticed that in particular the correction of the detrital (or lithogenic) fraction demands more attention. Henderson and Anderson [] suggested to quantify Pa detr and Th detr by assuming a constant ( 238 U/ 232 Th) detr in lithogenic material of 0.6 ± 0.1 (activity ratio), which leads (in concert with the 232 Th concentration of purely lithogenic origin) to the lithogenic 235 U and 234 U concentrations.…”

Section: Methodsmentioning

confidence: 99%

“…Following this approach, we assumed a ( 238 U/ 232 Th) detr of 0.40 ± 0.03 due to the very low values in bulk 238 U/ 232 Th observed at this location (minimum 0.37) taking an uncertainty on the ( 238 U/ 232 Th) detr of ±0.03 into account when calculating the error for the 231 Pa/ 230 Th ratio. We note that at this location the approach by Bourne et al [] is crucially necessary, especially for the HS1 interval of our record. When for instance assuming 0.6 for ( 238 U/ 232 Th) detr the extreme input of detrital material would lead to unreasonable values, like 231 Pa/ 230 Th > 0.4.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Synchronous and proportional deglacial changes in Atlantic meridional overturning and northeast Brazilian precipitation

et al. 2017

View full text Add to dashboard Cite

Changes in heat transport associated with fluctuations in the strength of the Atlantic meridional overturning circulation (AMOC) are widely considered to affect the position of the Intertropical Convergence Zone (ITCZ), but the temporal immediacy of this teleconnection has to date not been resolved. Based on a high‐resolution marine sediment sequence over the last deglaciation, we provide evidence for a synchronous and near‐linear link between changes in the Atlantic interhemispheric sea surface temperature difference and continental precipitation over northeast Brazil. The tight coupling between AMOC strength, sea surface temperature difference, and precipitation changes over northeast Brazil unambiguously points to a rapid and proportional adjustment of the ITCZ location to past changes in the Atlantic meridional heat transport.

show abstract

“…Later studies argued that the minimum measured bulk sediment ( A 238U / A 232Th ) lith over the studied time series would be the closest estimate to the actual ( A 238U / A 232Th ) lith (Böhm et al, ; Costa & McManus, ; Lippold et al, ; Mulitza et al, ). Another approach has been to use ( A 234U / A 238U ) to identify sediment with no authigenic contribution, within which the bulk sediment ( A 238U / A 232Th ) would be a more accurate estimate for the local lithogenic value (Bourne et al, ). This approach assumes a seawater ( A 234U / A 238U ) of 1.1468 (Andersen et al, ) and a lithogenic ( A 234U / A 238U ) of 1 (i.e., secular equilibrium).…”

Section: Background: the Marine Geochemistry Of 230thmentioning

confidence: 99%

²³⁰Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

Costa

Hayes

Anderson

et al. 2020

Paleoceanog and Paleoclimatol

View full text Add to dashboard Cite

230Th normalization is a valuable paleoceanographic tool for reconstructing high‐resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of 230Th systematics, with regard to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the late Holocene (0–5,000 years ago, or 0–5 ka) and the Last Glacial Maximum (18.5–23.5 ka), and investigated the spatial structure of 230Th‐normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79–2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48–1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size‐dependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (>1,000 m water depth).

show abstract

Improved determination of marine sedimentation rates using ²³⁰Th_xs

Cited by 30 publications

References 23 publications

Variability in mid‐depth ventilation of the western Atlantic Ocean during the last deglaciation

Variability in mid‐depth ventilation of the western Atlantic Ocean during the last deglaciation

Synchronous and proportional deglacial changes in Atlantic meridional overturning and northeast Brazilian precipitation

²³⁰Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

Contact Info

Product

Resources

About

Improved determination of marine sedimentation rates using 230Thxs

Cited by 30 publications

References 23 publications

Variability in mid‐depth ventilation of the western Atlantic Ocean during the last deglaciation

Variability in mid‐depth ventilation of the western Atlantic Ocean during the last deglaciation

Synchronous and proportional deglacial changes in Atlantic meridional overturning and northeast Brazilian precipitation

230Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

Contact Info

Product

Resources

About

Improved determination of marine sedimentation rates using ²³⁰Th_xs

²³⁰Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean