Seismic origin of the Atacama Desert boulder fields

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dc.contributor.authorMatmon, Aen_AU
dc.contributor.authorQuade, Jen_AU
dc.contributor.authorPlaczek, CJen_AU
dc.contributor.authorFink, Den_AU
dc.contributor.authorArnold, Men_AU
dc.contributor.authorAumaître, Gen_AU
dc.contributor.authorBourlès, Den_AU
dc.contributor.authorKeddadouche, Ken_AU
dc.contributor.authorCopeland, Aen_AU
dc.contributor.authorNeilson, JWen_AU
dc.date.accessioned2015-09-08T05:35:31Zen_AU
dc.date.available2015-09-08T05:35:31Zen_AU
dc.date.issued2015-02-15en_AU
dc.date.statistics2015-09-03en_AU
dc.description.abstractExtensive fields of large boulders are common around the base of hills in the Atacama Desert. How these boulders are transported from nearby hillslopes is unclear given the lack of rainfall of the region. Here we document the central role of seismicity, not runoff, in transporting and smoothing >1 ton boulders all across the hyperarid core of the Atacama Desert. The generally granitoid boulders emerge as corestones on hillslopes at an erosion rate of 0.1-1 m Ma(-1). Thereafter, physical and cosmogenic isotopic evidence suggests that boulders slide and bounce rather than roll down hills and onto adjacent flats. In the transport process, the largest boulders are split and the smaller ones are weathered to grus, narrowing average boulder mass to similar to 2 tons (<1 m(3)). At the base of hills, the boulders bunch together and rub during the frequent earthquakes in the region, producing distinctive smoothing around boulder mid-sections, and silt moats around the boulder bases. Our measurements show a strong correlation between boulder field density and rubbing, and only when the density exceeds 60-70% does rubbing become common. Except for slow removal by rubbing, the boulders seem to undergo no further erosion while in the flats. Exposure times for some boulders are >12 Ma, making them among the oldest continuously exposed features on the Earth. Boulder rubbing is just one geologic feature among many in the Atacama that underscore the role that seismicity probably plays in shaping landscapes of the waterless worlds of the solar system. © 2015, Elsevier B.V.en_AU
dc.identifier.citationMatmon, A., Quade, J., Placzek, C., Fink, D., Arnold, M., Aumaître, G., Bourles, D., Keddadouche, K., Copeland, A., & Neilson, J. W. (2015). Seismic origin of the Atacama Desert boulder fields. Geomorphology, 231, 28-39. doi:10.1016/j.geomorph.2014.11.008en_AU
dc.identifier.govdoc6002en_AU
dc.identifier.issn0169-555Xen_AU
dc.identifier.journaltitleGeomorphologyen_AU
dc.identifier.pagination28-39en_AU
dc.identifier.urihttp://dx.doi.org/10.1016/j.geomorph.2014.11.008en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/6178en_AU
dc.identifier.volume231en_AU
dc.language.isoenen_AU
dc.publisherElsevier BVen_AU
dc.subjectIsotopesen_AU
dc.subjectOriginen_AU
dc.subjectDesertsen_AU
dc.subjectEarthquakesen_AU
dc.subjectErosionen_AU
dc.subjectRainen_AU
dc.titleSeismic origin of the Atacama Desert boulder fieldsen_AU
dc.typeJournal Articleen_AU
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