Ichnological evidence for bottom water oxygenation during organic rich layer deposition in the westernmost Mediterranean over the Last Glacial Cycle

Casanova-Arenillas, Santiago; Rodrı́guez-Tovar, Francisco J.; Martı́nez-Ruiz, Francisca

doi:10.1016/j.margeo.2021.106673

Cited by 3 publications

(2 citation statements)

References 142 publications

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“…In oxygenated sediments that form the bulk of the marine sedimentary archives used for paleoclimate reconstruction, the deposited material is mixed by burrowing and feeding activities of the benthic fauna in the upper layer of sediment (Berger et al, 1979;Savrda and Bottjer, 1991;Casanova-Arenillas et al, 2022). As the rate of biological mixing, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, secondary modifications by trace fossils of different sizes, such as Chondrites, Planolites, Thalassinoides, Scolicia, and Zoophycos, result in vertical and horizontal variability as well (Figures 1B,C) (e.g. Dorador et al, 2020;Casanova-Arenillas et al, 2022). The impacts within the sediment are deep-reaching burrows and spreiten with fillings different from the surrounding sediment leading to considerable horizontal differences in age estimates on local (intra-sample, mm-to cm-scale) and regional (between different samples and cores, m-to km-scale) spatial scales (Anderson, 2001;Bard, 2001;Löwemark and Werner, 2001;Lougheed et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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Age-Heterogeneity in Marine Sediments Revealed by Three-Dimensional High-Resolution Radiocarbon Measurements

Zuhr

Dolman

et al. 2022

Front. Earth Sci.

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Marine sedimentary archives are routinely used to reconstruct past environmental changes. In many cases, bioturbation and sedimentary mixing affect the proxy time-series and the age-depth relationship. While idealized models of bioturbation exist, they usually assume homogeneous mixing, thus that a single sample is representative for the sediment layer it is sampled from. However, it is largely unknown to which extent this assumption holds for sediments used for paleoclimate reconstructions. To shed light on 1) the age-depth relationship and its full uncertainty, 2) the magnitude of mixing processes affecting the downcore proxy variations, and 3) the representativity of the discrete sample for the sediment layer, we designed and performed a case study on South China Sea sediment material which was collected using a box corer and which covers the last glacial cycle. Using the radiocarbon content of foraminiferal tests as a tracer of time, we characterize the spatial age-heterogeneity of sediments in a three-dimensional setup. In total, 118 radiocarbon measurements were performed on defined small- and large-volume bulk samples ( ∼ 200 specimens each) to investigate the horizontal heterogeneity of the sediment. Additionally, replicated measurements on small numbers of specimens (10 × 5 specimens) were performed to assess the heterogeneity within a sample volume. Visual assessment of X-ray images and a quantitative assessment of the mixing strength show typical mixing from bioturbation corresponding to around 10 cm mixing depth. Notably, our 3D radiocarbon distribution reveals that the horizontal heterogeneity (up to 1,250 years), contributing to the age uncertainty, is several times larger than the typically assumed radiocarbon based age-model error (single errors up to 250 years). Furthermore, the assumption of a perfectly bioturbated layer with no mixing underneath is not met. Our analysis further demonstrates that the age-heterogeneity might be a function of sample size; smaller samples might contain single features from the incomplete mixing and are thus less representative than larger samples. We provide suggestions for future studies, optimal sampling strategies for quantitative paleoclimate reconstructions and realistic uncertainty in age models, as well as discuss possible implications for the interpretation of paleoclimate records.

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Section: Introductionmentioning

confidence: 99%