Radiocarbon and 230Th data reveal rapid redistribution and temporal changes in sediment focussing at a North Atlantic drift

Mollenhauer, Gesine; McManus, Jerry F; Wagner, Thomas; McCave, I Nick; Eglinton, T. I.

doi:10.1016/j.epsl.2010.11.022

Cited by 19 publications

(10 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Habitat depth differences (Waelbroeck et al 2001), abundance variations (Manighetti et al 1995;Barker et al 2007), differential dissolution and fragmentation (Barker et al 2007), degree of ontogenetic encrustation (Kozdon et al 2009), sediment remobilization (Broecker et al 2006;Barker et al 2007), and morphologically dependent bioturbation (Peng and Broecker 1984) can dissociate 14 C ages of different species within the same sediment interval. Age offsets between foraminiferal species are generally no more than 1-3 kyr, but larger 14 C offsets on the order of 10 kyr have been observed between alkenones and foraminifera (Ohkouchi et al 2002;Mollenhauer et al 2003Mollenhauer et al , 2005Mollenhauer et al , 2006Mollenhauer et al , 2011Uchida et al 2005), between foraminiferal species within extremely bioturbated zoophycos channels (Löwemark and Werner 2001;Leuschner et al 2002;Löwemark and Grootes 2004), and between frosty and glassy tests of variably preserved foraminifera of the same species (Wycech et al 2016).…”

Section: Discussionmentioning

confidence: 99%

Radiocarbon and Stable Isotope Evidence for Changes in Sediment Mixing in the North Pacific over the Past 30 kyr

2017

View full text Add to dashboard Cite

Deep-sea sediment mixing by bioturbation is ubiquitous on the seafloor, and it can be an important influence on the fidelity of paleoceanographic records. Bioturbation can be difficult to quantify, especially in the past, but diffusive models based on radioactive tracer profiles have provided a relatively successful approach. However, a singular, constant mixing regime is unlikely to prevail in a region where dynamic oceanographic changes in the bottom water environment are a consequence of paleoclimatic variability. In this study, foraminiferal stable isotopes, radiocarbon (14C) dating, and 230Th fluxes are utilized to understand the sediment mixing history in the easternmost region of the North Pacific. In the uppermost sediment, a 12,000-yr offset between planktonic foraminifera species N. incompta and G. bulloides is observed that coincides with age plateaus at 2000–2500 yr for N. incompta and 15,000–16,000 yr for G. bulloides despite coincident glacial-interglacial shifts in δ18O of benthic species. These age plateaus, particularly for G. bulloides, are a result of changing foraminiferal abundance related to assemblage shifts and carbonate preservation changes since the last glacial period, providing a window into the extent of mixing in the past. The 14C and stable isotope results can be simulated using an iterative model that couples these changes in foraminiferal abundance with variability in mixing depth over time. The best-fit model output suggests that the deepest, or most intense, mixing of the past 30,000 yr (30 kyr) may have occurred during the Holocene. Even though changes in mixing affect the 14C and δ18O of planktonic species that have dramatically varying abundance, substantial age control is nevertheless provided by δ18O measurements on the more consistently abundant benthic foraminifera Uvigerina, thus allowing the construction of a reliable chronology for these cores.

show abstract

Section: Discussionmentioning

confidence: 99%

Radiocarbon and Stable Isotope Evidence for Changes in Sediment Mixing in the North Pacific over the Past 30 kyr

2017

View full text Add to dashboard Cite

show abstract

“…The advantages of 230 Th normalization are (1) quantification of absolute particle fluxes, (2) elimination of dilution effects, (3) insensitivity to small errors in age model (about 1%/kyr), and (4) correction for lateral sediment inputs (e.g., focusing and winnowing). Although 230 Th normalization has been a topic of considerable debate in the equatorial Pacific [ Lyle et al , , , ; Francois et al , ; Marcantonio et al , ], the applicability of this technique has been justified in extensive detail [ Mollenhauer et al , , ; McGee et al , ; Costa and McManus , ], including across the equatorial Pacific [ Pichat et al , ; Anderson et al , , ; Kienast et al , ; McGee et al , , , Winckler et al , , ] and particularly at the Line Islands [ Costa et al , ; Jacobel et al ., , ].…”

Section: Methodsmentioning

confidence: 99%

Productivity patterns in the equatorial Pacific over the last 30,000 years

Costa

Jacobel

McManus

et al. 2017

Global Biogeochemical Cycles

Self Cite

View full text Add to dashboard Cite

The equatorial Pacific traverses a number of productivity regimes, from the highly productive coastal upwelling along Peru to the near gyre-like productivity lows along the international dateline, making it an ideal target for investigating how biogeochemical systems respond to changing oceanographic conditions over time. However, conflicting reconstructions of productivity during periods of rapid climate change, like the last deglaciation, render the spatiotemporal response of equatorial Pacific productivity ambiguous. In this study, surface productivity since the last glacial period (30,000 years ago) is reconstructed from seven cores near the Line Islands, central equatorial Pacific, and integrated with productivity records from across the equatorial Pacific. Three coherent deglacial patterns in productivity are identified: (1) a monotonic glacial-Holocene increase in productivity, primarily along the Equator, associated with increasing nutrient concentrations over time; (2) a deglacial peak in productivity~15,000 years ago due to transient entrainment of nutrient rich southern-sourced deep waters; and (3) possible precessional cycles in productivity in the eastern equatorial Pacific that may be related to Intertropical Convergence Zone migration and potential interactions with El Niño-Southern Oscillation dynamics. These findings suggest that productivity was generally lower during the glacial period, a trend observed zonally across the equatorial Pacific, while deglacial peaks in productivity may be prominent only in the east.

show abstract

“…What is most impressive about the alkenone SST records is the degree of concordance with independent isotopic records, including spe 500-08 1st pgs page 22 O isotope variations recorded in ice cores and foraminifera (e.g., Herbert et al, 2001). It has become clear that multiple approaches are needed to understand and constrain each proxy in terms of the robustness of paleotemperature records and the effects of lateral sediment redistribution (Mollenhauer et al, 2011).…”

Section: Elucidating Paleoenvironmental Recordsmentioning

confidence: 99%

“…Radiocarbon measurements of individual organic molecules have also led to new insights into the age structure of fossil lipid assemblages, and their transport from source to sedimentary sinks (Pearson et al, 2001). Thus, in contemporary environmental settings, it is possible to discern the age relations of multiple paleoclimate proxies (Mollenhauer et al, 2003), thereby resolving processes such as winnowing and lateral advection of organic matter (Kusch et al, 2010;Mollenhauer et al, 2011). The robustness, scope, and fi delity of organic SST proxies based on algal alkenones and archaeal ether lipids have been signifi cantly increased through knowledge gained from compound-specifi c radiocarbon measurements (Eglinton and Eglinton, 2008).…”

Section: Using Stable Isotopes To Better Understand the Origins Of Bimentioning

confidence: 99%

Smaller, better, more: Five decades of advances in geochemistry

McLennan

McSween

Summons

2013

The Web of Geological Sciences: Advances, Impacts, and Interactions

View full text Add to dashboard Cite

Many of the discoveries made in geochemistry over the last 50 yr have been driven by technological advances that have allowed analysis of smaller samples, attainment of better instrumental precision and accuracy or computational capability, and automation that has provided many more data. These advances occurred during development of revolutionary concepts, such as plate tectonics, which has provided an overarching framework for interpreting many geochemical studies. Also, spacecraft exploration of other planetary bodies, including analyses of returned lunar samples and remote sensing of Mars, has added an additional dimension to geochemistry. Determinations of elemental compositions of minerals and rocks, either through in situ analysis by various techniques (e.g., electron microprobe, secondary ion mass spectrometry [SIMS], synchrotron X-ray fl uorescence [XRF], laser ablation) or bulk analysis (e.g., XRF, inductively coupled plasma-atomic emission spectrometry [ICP-AES], inductively coupled plasma-mass spectrometry [ICP-MS]), have become essential approaches to many geochemical studies at levels of sensitivity and spatial resolution undreamed of fi ve decades ago. Although major-element distributions in igneous rocks have been understood at a basic level for some time, advances using major-element abundances to understand sedimentary provenance and processes have been especially noteworthy during the past half-century. The great diversity of trace elements in terms of geochemical behavior (e.g., lithophile, siderophile, etc.) has made them invaluable to many studies, providing unique constraints on redox conditions, mineral-melt and mineral-fl uid reactions, and planetary differentiation.

show abstract

Radiocarbon and 230Th data reveal rapid redistribution and temporal changes in sediment focussing at a North Atlantic drift

Cited by 19 publications

References 40 publications

Radiocarbon and Stable Isotope Evidence for Changes in Sediment Mixing in the North Pacific over the Past 30 kyr

Radiocarbon and Stable Isotope Evidence for Changes in Sediment Mixing in the North Pacific over the Past 30 kyr

Productivity patterns in the equatorial Pacific over the last 30,000 years

Smaller, better, more: Five decades of advances in geochemistry

Contact Info

Product

Resources

About