The potential of sedimentary foraminiferal rare earth element patterns to trace water masses in the past

Abstract

Dissolved rare earth element (REE) concentration data from intermediate and deep seawater form an array characterized by higher middle‐REE enrichments (MREE/MREE*) in the North Atlantic and a progressive increase in heavy‐to‐light REE ratios (HREE/LREE) as water masses age. The REEs in foraminifera are fractionated toward higher MREE/MREE* and lower HREE/LREE relative to seawater. Calculations based on a scavenging model show that the REE patterns in uncleaned core‐top foraminifera resemble those adsorbed onto calcite, particulate organic material, and hydrous ferric oxides but the full extent of the REE fractionation measured in foraminifera was not reproduced by the model. However, differences in the HREE/LREE and MREE/MREE* ratios and the cerium anomaly between ocean basins are preserved and are in agreement with the seawater REE distribution. Under oxic conditions, the HREE/LREE and MREE/MREE* compositions of uncleaned foraminifera at the sediment/seawater boundary are preserved during burial but the cerium anomaly is sensitive to burial depth. In suboxic sedimentary environments, all uncleaned foraminiferal REE concentrations are elevated relative to core‐top values indicating addition of REEs from pore waters. The HREE/LREE ratio is highest when sedimentation rates were greatest and when high Fe/Ca ratios in the uncleaned foraminifera indicate that Fe was mobile. In sediments that have not experienced suboxic conditions during burial, uncleaned foraminifera preserve the seawater signal taken up at the sediment/seawater interface and are therefore suggested to be a suitable archive of changes in the REE signal of past bottom waters.

The Influence of Basaltic Islands on the Oceanic REE Distribution: A Case Study From the Tropical South Pacific

“…Station 21-1 (this study) is also shown in order to evaluate differences with respect to SEqPIW, which dominates the intermediate water at this location. In general, all samples have lower LREE concentrations compared with original AAIW, which is expected as the more readily scavenged LREEs are preferentially removed from the water column as the water masses age (e.g., Osborne et al, 2017). The fact that the source AAIW normalized REEs are <1, especially for the LREEs, clearly indicates the importance of removal by particles during transit through the gyre, despite relatively low productivity.…”

“…All samples were filtered directly from the Niskin bottles using AcroPak500 filter cartridges with 0.8/0.2 µm pore size into acid-cleaned PE bottles and cubitainers, 125 ml for REE analysis and 10 L for Nd isotope compositions, respectively. All samples were acidified to pH 2 onboard using distilled 6 N HCl and were stored at 4 • C. REE concentrations for profile 21-1 (except for 5,172 m) and sample 53-4-3088 m were previously published in Osborne et al (2017).…”

Deepwater Expansion and Enhanced Remineralization in the Eastern Equatorial Pacific During the Last Glacial Maximum

“…The PAAS‐normalized distribution of rare earth elements at 2.37 km (TR163‐14) and 3.2 km (TR163‐20B) compared to published eastern equatorial Pacific core top data from cores TR163‐11, TR163‐14, and VM28‐139 (Osborne et al, ).…”

“…However, riverine input and alteration of basalts are also important sources and sinks of Li to sediments (Elderfield & Schultz, 1996) and high Figure 6. The PAAS-normalized distribution of rare earth elements at 2.37 km (TR163-14) and 3.2 km (TR163-20B) compared to published eastern equatorial Pacific core top data from cores TR163-11, TR163-14, and VM28-139 (Osborne et al, 2017).…”

Rare earth elements in oyster shells: provenance discrimination and potential vital effects

“…Several reasons for these interspecific differences can be advanced. It is known that oysters can be selective in their diet, composed mainly of diatoms (Yonge, 1928;Paulmier, 1971) of a specific size range, and preferentially digest specific species of diatoms over others (Shumway et al, 1985;Cognie et al, 2001). If food is a source of REEs, it may be possible that each oyster species does not feed on the same prey, which can present different abundances of these elements.…”