EGU25-10564, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-10564
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Reconstructing storminess from aeolian sand influx to peat bogs using X-ray computed tomography
Ylva Palmgren1,2, Matt O'Regan1,2, and Malin Kylander1,2
Ylva Palmgren et al.
  • 1Department of Geological Sciences, Stockholm University, Stockholm, Sweden
  • 2Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden

In recent years the use of aeolian sand influx (ASI) analyses on ombrotrophic peat sequences (c.f. Björck and Clemmensen, 2004) has become an increasingly popular method for reconstructing past storminess. This method is based on the assumption that all mineral grains deposited on the surface of the hydrologically isolated bog must have been brought to the site by wind. Thus, changes in the amount and size of the mineral grains found over time/depth can be related to past storm frequency and intensity. During the last two decades, several different methods of quantifying ASI have been developed. Three major drawbacks of these methods are that they are (i) often time- and labour intensive; (ii) rely on high temperature dry ashing to remove organic material from samples before ASI quantification and (iii) non-continuous, requiring discrete sampling.

In an attempt to address these issues, we investigate whether X-ray computed tomography (CT) can be used to count and measure sand grains in peat. Drawing from the methods used by Cederstrøm et al. (2021) for IRD quantification in marine sediments, we added known amounts of sand (manually counted) in certain grain size fractions (63-1000, 125-1000, 63-125, 125-250, 250-500 and 500-1000 µm) and with known grain size distributions (laser diffraction) to test peat samples. The samples were then CT-scanned at a voxel resolution of 27.5 µm, and in the resulting 3D imagery, sand grains were identified, counted and measured using basic image processing tools. Our preliminary results indicate that it is possible to reliably count and measure sand grains in peat using a CT-based method, especially for grain sizes larger than 4-5 voxels (≥125 µm in this study). Grain size distributions for peat samples with sand grains ≥125 µm acquired through the CT method are strongly correlated to standard laser diffraction results (r = 0.81–0.98, p < 0.01). Similarly, CT-based and manual grain counts show a strong correlation (r = 0.94–1.00, p < 0.01) and the number of grains counted using the CT method differs on average by only 4 % from manual counts. Early-stage trials with full peat sequences further indicate that CT could be a reliable and efficient method for quantifying ASI and reconstructing past storm variability.

References

Björck, S., Clemmensen, L., 2004. Aeolian sediment in raised bog deposits, Halland, SW Sweden: A new proxy record of Holocene winter storminess variation in southern Scandinavia? Holocene 14, 677–688. https://doi.org/10.1191/0959683604hl746rp

Cederstrøm, J.M., van der Bilt, W.G.M., Støren, E.W.N., Rutledal, S., 2021. Semi-automatic ice-rafted debris quantification with computed tomography. Paleoceanography and Paleoclimatology 36, e2021PA004293. https://doi.org/10.1029/2021PA004293

How to cite: Palmgren, Y., O'Regan, M., and Kylander, M.: Reconstructing storminess from aeolian sand influx to peat bogs using X-ray computed tomography, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10564, https://doi.org/10.5194/egusphere-egu25-10564, 2025.