Preprints
https://doi.org/10.5194/egusphere-2024-3817
https://doi.org/10.5194/egusphere-2024-3817
27 Jan 2025
 | 27 Jan 2025
Status: this preprint is open for discussion and under review for The Cryosphere (TC).

Folding due to anisotropy in ice, from drill core-scale cloudy bands to km-scale internal reflection horizons

Paul Dirk Bons, Yuanbang Hu, Maria-Gema Llorens, Steven Franke, Nicolas Stoll, Ilka Weikusat, Julien Wetshoff, and Yu Zhang

Abstract. Upright folds in ice sheets are observed on the cm-scale in cloudy bands in drill cores and on the km-scale in radargrams. We address the question of the folding mechanism for these folds, by analysing the power spectra of fold trains to obtain the amplitude as a function of wavelength signal. Classical Biot-type buckle folds due to a rheological contrast between layers develop a characteristic wavelength, visible as a peak in the power spectrum. Power spectra of ice folds, however, follow a power law with a steady increase in amplitude with wavelength. Such a power spectrum is also observed in a folded, highly anisotropic biotite schist and in a numerical simulation of the deformation of ice Ih with a strong alignment of the basal planes parallel to the shortening direction. This suggests that the folds observed in ice are primarily due to the strong mechanical anisotropy of ice that tends to have a strong lattice preferred orientation due to ice-sheet flow.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
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Paul Dirk Bons, Yuanbang Hu, Maria-Gema Llorens, Steven Franke, Nicolas Stoll, Ilka Weikusat, Julien Wetshoff, and Yu Zhang

Status: open (until 14 Mar 2025)

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Paul Dirk Bons, Yuanbang Hu, Maria-Gema Llorens, Steven Franke, Nicolas Stoll, Ilka Weikusat, Julien Wetshoff, and Yu Zhang
Paul Dirk Bons, Yuanbang Hu, Maria-Gema Llorens, Steven Franke, Nicolas Stoll, Ilka Weikusat, Julien Wetshoff, and Yu Zhang

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Short summary
What causes folds in ice layers from the km-scale down to the scale visible in drill core? Classical buckle folding due to variations in viscosity between layers, or the effect of mechanical anisotropy of ice due to an alignment of the crystal-lattice planes? Comparison of power spectra of folds in ice, a biotite schist, and numerical simulations show that folding in ice is due to the mechanical anisotropy, as there is no characteristic fold scale that would result from buckle folding.
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