气候变化领域集成服务门户(CCPortal): Small-scale disturbances in the stratigraphy of the NEEM ice core: Observations and numerical model simulations

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DOI	10.5194/tc-10-359-2016
	Small-scale disturbances in the stratigraphy of the NEEM ice core: Observations and numerical model simulations
	Jansen D.; Llorens M.-G.; Westhoff J.; Steinbach F.; Kipfstuhl S.; Bons P.D.; Griera A.; Weikusat I.
发表日期	2016
ISSN	19940416
卷号	10 期号:1
英文摘要	Disturbances on the centimetre scale in the stratigraphy of the North Greenland Eemian Ice Drilling (NEEM) ice core (North Greenland) can be mapped by an optical line scanner as long as the ice has visual layering, such as, for example, cloudy bands. Different focal depths allow, to a certain extent, a three-dimensional view of the structures. In this study we present a detailed analysis of the visible folds, discuss their characteristics and frequency, and present examples of typical fold structures. We also analyse the structures with regard to the deformation boundary conditions under which they formed. The structures evolve from gentle waves at about 1500 m to overturned z folds with increasing depth. Occasionally, the folding causes significant thickening of layers. Their similar fold shape indicates that they are passive features and are probably not initiated by rheology differences between alternating layers. Layering is heavily disturbed and tracing of single layers is no longer possible below a depth of 2160 m. C axes orientation distributions for the corresponding core sections were analysed, where available, in addition to visual stratigraphy. The data show axial-plane parallel strings of grains with c axis orientations that deviate from that of the matrix, which shows a single maximum fabric at the depth where the folding occurs. Numerical modelling of crystal viscoplastic deformation and dynamic recrystallisation was used to improve the understanding of the formation of the observed structures during deformation. The modelling reproduces the development of bands of grains with a tilted-lattice orientation relative to the single maximum fabric of the matrix, and also the associated local deformation. We conclude from these results that the observed folding can be explained by formation of these tilted-lattice bands. © Author(s) 2016.
学科领域	boundary condition; crystal; deformation; Eemian; folding; ice core; numerical model; recrystallization; rheology; stratigraphy
语种	英语
scopus关键词	boundary condition; crystal; deformation; Eemian; folding; ice core; numerical model; recrystallization; rheology; stratigraphy
来源期刊	Cryosphere
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/119704
作者单位	Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany; Department of Geosciences, Eberhard Karls University Tübingen, Tübingen, Germany; Departament de Geologia, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
推荐引用方式 GB/T 7714	Jansen D.,Llorens M.-G.,Westhoff J.,et al. Small-scale disturbances in the stratigraphy of the NEEM ice core: Observations and numerical model simulations[J],2016,10(1).
APA	Jansen D..,Llorens M.-G..,Westhoff J..,Steinbach F..,Kipfstuhl S..,...&Weikusat I..(2016).Small-scale disturbances in the stratigraphy of the NEEM ice core: Observations and numerical model simulations.Cryosphere,10(1).
MLA	Jansen D.,et al."Small-scale disturbances in the stratigraphy of the NEEM ice core: Observations and numerical model simulations".Cryosphere 10.1(2016).