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DOI	10.1016/j.epsl.2020.116643
	The fold illusion: The origins and implications of ogives on silicic lavas
	Andrews G.D.M.; Kenderes S.M.; Whittington A.G.; Isom S.L.; Brown S.R.; Pettus H.D.; Cole B.G.; Gokey K.J.
发表日期	2021
ISSN	0012821X
卷号	553
英文摘要	Folds on the surfaces of mafic lavas are among the most readily recognized geological structures and are used as first-order criteria for identifying ancient lavas on Earth and other planetary bodies. However, the presence of surface-folds on the surface of silicic lavas is contested in this study and we challenge the widely accepted interpretation that silicic lava surfaces contain folds using examples from the western United States and Sardinia, Italy. We interpret the ridges and troughs on their upper surfaces, typically referred to as ‘ogives’ or ‘pressure ridges’, as fracture-bound structures rather than folds. We report on the absence of large-scale, buckle-style folds and note instead the ubiquitous presence of multiple generations and scales of tensile fractures comparable to crevasses in glaciers and formed in ways similar to already recognized crease structures. We report viscosity data and results of stress analyses that preclude folding (ductile deformation in compression) of the upper surface of silicic lavas at timescales of emplacement (weeks to months). Therefore, analysis of fold geometry (wavelength, amplitude, etc.) is erroneous, and instead the signal produced reflects the strength and thickness of the brittle upper surface stretching over a ductile interior. The presence of ogives on the surfaces of lavas on other planetary bodies may help to elucidate their rheological properties and crustal thicknesses, but relating to their tensile strength, not viscosity. © 2020 The Author(s)
关键词	obsidian ogives silicic lava tensile fractures viscometry
英文关键词	Tensile strength; Viscosity; Bound structure; Ductile deformations; Geological structures; Planetary bodies; Pressure ridge; Rheological property; Tensile fractures; Western United States; Planets; crevasse; crustal thickness; emplacement; fold; folding; fracture; glacier; lava; obsidian; rheology; siliciclastic deposit; stress analysis; tensile strength; trough; viscosity; Italy; Sardinia; United States
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203020
作者单位	West Virginia University, United States; University of Missouri, United States; University of Texas at San Antonio, United States; West Virginia Geological and Economic Survey, United States
推荐引用方式 GB/T 7714	Andrews G.D.M.,Kenderes S.M.,Whittington A.G.,et al. The fold illusion: The origins and implications of ogives on silicic lavas[J],2021,553.
APA	Andrews G.D.M..,Kenderes S.M..,Whittington A.G..,Isom S.L..,Brown S.R..,...&Gokey K.J..(2021).The fold illusion: The origins and implications of ogives on silicic lavas.Earth and Planetary Science Letters,553.
MLA	Andrews G.D.M.,et al."The fold illusion: The origins and implications of ogives on silicic lavas".Earth and Planetary Science Letters 553(2021).