Transformation of high-relief canyon topography by an ancient rock avalanche, Hop Valley, Zion National Park, Utah, USA
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Datum
2021-05-01Typ
- Journal Article
ETH Bibliographie
yes
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Abstract
Zion National Park preserves a rich geological record of Holocene landslide-dammed canyons in its deeply incised topography, with 11 hypothesized valley-blocking deposits within the park boundaries. Despite consistent stratigraphic, tectonic, and climatic settings, the occurrence of and subsequent landscape response to these natural dams varies. As such, the region provides a unique natural laboratory for quantifying the effect and evolution of landslide dams in high-relief canyon topography. Here we present a detailed study of a rock avalanche deposited at the mouth of Hop Valley in Zion National Park, describing its age, size, emplacement conditions, impact on local geomorphology and sedimentology, as well as the subsequent usage of the valley by native Ancestral Puebloans. Topographic reconstructions indicate the original deposit was ~75 million m and 1.5 km long with a maximum thickness of 180 m. New ages from cosmogenic Be surface exposure dating indicate a single-event failure at 6.7 ± 0.7 ka. The rock avalanche impounded ~55 million m of sediment, transforming Hop Valley from a relatively narrow gorge to a broad flat-floored canyon. Stratigraphic sections of accumulated upvalley sediments, calculated sedimentation rates (averaging 8.2 ± 0.8 m/ky), and paleoclimate records suggest the deposit primarily dammed sediment, rather than water, to produce an extensive alluvial plain. This detailed case-history analysis, together with our review of other Holocene landslide dams in Zion National Park, helps clarify the legacy of valley-blocking mass movements in steep canyon topography. 3 10 3 Mehr anzeigen
Publikationsstatus
publishedExterne Links
Zeitschrift / Serie
The HoloceneBand
Seiten / Artikelnummer
Verlag
SAGEThema
Ancestral Puebloans; Cosmogenic nuclides; Geomorphology; Landslide dams; Rock avalanche; Zion National ParkOrganisationseinheit
08619 - Labor für Ionenstrahlphysik (LIP) / Laboratory of Ion Beam Physics (LIP)
ETH Bibliographie
yes
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