Small scale folding observed in the NEEM ice core
Disturbances on the centimeter scale in the layering of the NEEM ice core (North Greenland) can be mapped by means of visual stratigraphy as long as the ice does have a visual layering, such as, for example, cloudy bands. Different focal depths of the visual stratigraphy method allow, to a certain e...
Main Authors: | , , , , , , , |
---|---|
Format: | Conference Object |
Language: | unknown |
Published: |
EGU
2015
|
Subjects: | |
Online Access: | https://epic.awi.de/id/eprint/37799/ https://hdl.handle.net/10013/epic.45428 |
id |
ftawi:oai:epic.awi.de:37799 |
---|---|
record_format |
openpolar |
spelling |
ftawi:oai:epic.awi.de:37799 2023-05-15T16:30:13+02:00 Small scale folding observed in the NEEM ice core Jansen, Daniela Llorens, Maria-Gema Westhoff, Julien Steinbach, Florian Bons, Paul D. Kipfstuhl, Sepp Griera, Albert Weikusat, Ilka 2015 https://epic.awi.de/id/eprint/37799/ https://hdl.handle.net/10013/epic.45428 unknown EGU Jansen, D. orcid:0000-0002-4412-5820 , Llorens, M. G. , Westhoff, J. , Steinbach, F. , Bons, P. D. , Kipfstuhl, S. , Griera, A. and Weikusat, I. orcid:0000-0002-3023-6036 (2015) Small scale folding observed in the NEEM ice core , EGU General Assembly 2015, Vienna, Austria, 2015 - unspecified . hdl:10013/epic.45428 EPIC3EGU General Assembly 2015, Vienna, Austria, 2015EGU Conference notRev 2015 ftawi 2021-12-24T15:40:26Z Disturbances on the centimeter scale in the layering of the NEEM ice core (North Greenland) can be mapped by means of visual stratigraphy as long as the ice does have a visual layering, such as, for example, cloudy bands. Different focal depths of the visual stratigraphy method allow, to a certain extent, a three dimensional view of the structures. In this study we present a structural analysis of the visible folds, discuss characteristics and frequency and present examples of typical fold structures. With this study we aim to quantify the potential impact of small scale folding on the integrity of climate proxy data. We also analyze the structures with regard to the stress environment under which they formed. The structures evolve from gentle waves at about 1700 m to overturned z-folds with increasing depth. Occasionally, the folding causes significant thickening of layers. Their shape indicates that they are passive features and are probably not initiated by rheology differences between layers. Layering is heavily disturbed and tracing of single layers is no longer possible below a depth of 2160 m. Lattice orientation distributions for the corresponding core sections were analyzed 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 has more or less a single-maximum fabric at the depth where the folding occurs. We conclude from these data that folding is a consequence of deformation along localized shear planes and kink bands. The findings are compared with results from other deep ice cores. The observations presented are supplemented by micro-structural modeling using a crystal plasticity code that reproduces deformation, applying a Fast Fourier Transform (FFT), coupled with ELLE to include dynamic recrystallization processes. The model results reproduce the development of bands of grains with a tilted orientation relative to the single maximum fabric of the matrix and also the associated local deformation. Conference Object Greenland ice core North Greenland Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) Greenland |
institution |
Open Polar |
collection |
Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) |
op_collection_id |
ftawi |
language |
unknown |
description |
Disturbances on the centimeter scale in the layering of the NEEM ice core (North Greenland) can be mapped by means of visual stratigraphy as long as the ice does have a visual layering, such as, for example, cloudy bands. Different focal depths of the visual stratigraphy method allow, to a certain extent, a three dimensional view of the structures. In this study we present a structural analysis of the visible folds, discuss characteristics and frequency and present examples of typical fold structures. With this study we aim to quantify the potential impact of small scale folding on the integrity of climate proxy data. We also analyze the structures with regard to the stress environment under which they formed. The structures evolve from gentle waves at about 1700 m to overturned z-folds with increasing depth. Occasionally, the folding causes significant thickening of layers. Their shape indicates that they are passive features and are probably not initiated by rheology differences between layers. Layering is heavily disturbed and tracing of single layers is no longer possible below a depth of 2160 m. Lattice orientation distributions for the corresponding core sections were analyzed 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 has more or less a single-maximum fabric at the depth where the folding occurs. We conclude from these data that folding is a consequence of deformation along localized shear planes and kink bands. The findings are compared with results from other deep ice cores. The observations presented are supplemented by micro-structural modeling using a crystal plasticity code that reproduces deformation, applying a Fast Fourier Transform (FFT), coupled with ELLE to include dynamic recrystallization processes. The model results reproduce the development of bands of grains with a tilted orientation relative to the single maximum fabric of the matrix and also the associated local deformation. |
format |
Conference Object |
author |
Jansen, Daniela Llorens, Maria-Gema Westhoff, Julien Steinbach, Florian Bons, Paul D. Kipfstuhl, Sepp Griera, Albert Weikusat, Ilka |
spellingShingle |
Jansen, Daniela Llorens, Maria-Gema Westhoff, Julien Steinbach, Florian Bons, Paul D. Kipfstuhl, Sepp Griera, Albert Weikusat, Ilka Small scale folding observed in the NEEM ice core |
author_facet |
Jansen, Daniela Llorens, Maria-Gema Westhoff, Julien Steinbach, Florian Bons, Paul D. Kipfstuhl, Sepp Griera, Albert Weikusat, Ilka |
author_sort |
Jansen, Daniela |
title |
Small scale folding observed in the NEEM ice core |
title_short |
Small scale folding observed in the NEEM ice core |
title_full |
Small scale folding observed in the NEEM ice core |
title_fullStr |
Small scale folding observed in the NEEM ice core |
title_full_unstemmed |
Small scale folding observed in the NEEM ice core |
title_sort |
small scale folding observed in the neem ice core |
publisher |
EGU |
publishDate |
2015 |
url |
https://epic.awi.de/id/eprint/37799/ https://hdl.handle.net/10013/epic.45428 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland ice core North Greenland |
genre_facet |
Greenland ice core North Greenland |
op_source |
EPIC3EGU General Assembly 2015, Vienna, Austria, 2015EGU |
op_relation |
Jansen, D. orcid:0000-0002-4412-5820 , Llorens, M. G. , Westhoff, J. , Steinbach, F. , Bons, P. D. , Kipfstuhl, S. , Griera, A. and Weikusat, I. orcid:0000-0002-3023-6036 (2015) Small scale folding observed in the NEEM ice core , EGU General Assembly 2015, Vienna, Austria, 2015 - unspecified . hdl:10013/epic.45428 |
_version_ |
1766019934557569024 |