New insights into the variety of zebra (stone) stripes in the Atacama Desert – reconsidering geomorphic processes and (palaeo-)activity

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Main Title: New insights into the variety of zebra (stone) stripes in the Atacama Desert – reconsidering geomorphic processes and (palaeo-)activity

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Abstract: The hyperarid parts of the Atacama Desert, N Chile, are among the driest places on Earth, and a number of studies have emphasized the remarkable slowness of earth surface processes in the Atacama since the late Tertiary. Nevertheless, geomorphic processes such as overland flow or flash flood activity generated by rare precipitation events, salt-driven shrink-swell processes, dust deposition, or seismic shaking have significantly contributed to the formation of the characteristic landscape. Although the relative dominance of these processes generally reflects the long duration of (hyper-)aridity, regional precipitation rates, and the amount of dust and salt accumulation in the hyperarid soils, process mechanisms and rates under the absence of water are still poorly understood, and a number of landforms may be regarded as fossil evidence of past geomorphic activity. Perhaps one of the most prominent hillslope forms are the Atacama-specific zebra (stone) stripes, covering slopes between the eastern coastal range and the pre-Andean cordilleras. Early studies had related the garland-like rock debris accumulations to salt-driven hillslope processes, but hitherto the study of Owen et al. (2013) represents the only study with detailed investigations on zebra-type stone stripes in the Atacama. According to these authors, zebra stripes “appear to be a feature unique to the Atacama Desert”, may represent a special type of reorganized desert pavement, and are contour-parallel, thin lateral bands of rather angular gravels on hillslopes, which are characterized by grain sorting and a specific wavelength. Due to sorting, wavelength, and regional distribution, zebra stripes are suggested to represent fossil evidence of overland flow, rather than resulting from salt-driven shrink-swell processes or seismic shaking. However, recent investigations on the formation of the Atacama boulder fields emphasized the significance of seismicity in shaping Atacama landscapes in general, thereby challenging the water-related evolution of zebra stripes as well. Based on UAV-derived high-resolution aerial photos, geomorphological surveys and sediment sampling during two field campaigns in the hyperarid core of the Atacama in September 2017 and February/March 2018 as well as the interpretation of Google Earth satellite images, this contribution adds important new and contrary data on zebra stripe patterns, which may be conducive in their better understanding. We document a wider distribution of zebra-type stone stripes than previously published, and a rather high variability of zebra stripe characteristics with regard to stripe orientation, sorting-patterns and bedding properties of stripe-confining surface gravel units. In addition to the findings of Owen et al. (2013), stripes may be poorly to well sorted, and surface gravel units may be multi-layered and up to 10 cm thick, loosely bedded, and entirely uncemented. At some locations, stripe orientation and sorting may be consistent with wind directions rather than with contour lines, and thick gravel accumulations may characterize downslope sections of zebra-striped hills. The investigated stone stripes clearly belong to the inventory of the Atacama-specific zebra stripes and illustrate the variability of zebra-type stripe forms and patterns. As such, our findings may complicate the geomorphic interpretation of zebra stripes and the inference of related geomorphic processes, ultimately raising questions regarding the discussion of zebra-stripe origin and formation. Our findings suggest that a variety of processes rather than one single process may be involved in the formation of zebra-striped hillslopes, and that some stripes do not only represent palaeo-landforms.

Responsible Party

*Creators:*	Matthias May (Author), Dirk Hoffmeister (Author), Dennis Wolf (Author), Marie Gröbner (Author), Florian Steininger (Author), Lennart Meine (Author), Olaf Bubenzer (Author)
*Publisher:*	CRC1211 Database (CRC1211DB)
*Publication Year:*	2019

Topic

*CRC1211 Topic:*	Surface
*Related Subproject:*	C3
*Subject:*	Keyword: Geomorphology
*Geogr. Information Topic:*	Environment

File Details

*Filename:*	MayetalAKGZebraStripes.pptx
*Data Type:*	Event - Event
*File Size:*	12.4 MB
*Date:*	Available: 31.10.2018
*Mime Type:*	application/vnd.openxmlformats-officedocument.presentationml.presentation
*Data Format:*	MS PowerPoint
*Language:*	English
*Status:*	Completed

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*Download Permission:*	Only Project Members
*General Access and Use Conditions:*	According to the CRC1211DB data policy agreement.
*Access Limitations:*	According to the CRC1211DB data policy agreement.
*Licence:*	[CRC1211DB] Data policy agreement

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Specific Information - Presentation

*Presenter:*	Simon Matthias May
*Presentation Date:*	25th of September, 2018
*Presentation Type:*	Talk
*Event:*	Central European Conference on Geomorphology and Quaternary Sciences
*Event Type:*	Conference
*Event Location:*	Giessen, Germany
*Event Duration:*	23rd of September, 2018 - 27th of September, 2018
*Event Website:*	http://www.uni-giessen.de/fbz/fb07/fachgebiete/geographie/bereiche/physisch/akg-deuqua2018

Metadata Details

*Metadata Creator:*	Simon Matthias May
*Metadata Created:*	28.10.2019
*Metadata Last Updated:*	28.10.2019
*Subproject:*	C3
*Funding Phase:*	1
*Metadata Language:*	English
*Metadata Version:*	V50

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