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Alluvial-fan sedimentation from a glacial-outburst flood, Lone Pine, California, and contrasts with meteorological flood deposits

Blair, T. C Garzón, Guillermina ; Baker, Victor R ; Martini, I. Peter

Flood and Megaflood Processes and Deposits, 2002, Vol.17, p.111-140 [Periódico revisado por pares]

United Kingdom: John Wiley & Sons, Incorporated

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  • Título:
    Alluvial-fan sedimentation from a glacial-outburst flood, Lone Pine, California, and contrasts with meteorological flood deposits
  • Autor: Blair, T. C
  • Garzón, Guillermina ; Baker, Victor R ; Martini, I. Peter
  • Assuntos: alluvial‐fan floods ; alluvial‐fan sedimentation from glacial‐outburst flood, Lone Pine California ‐ and contrasting with meteorological flood deposits ; Environmental impact of natural disasters & phenomena ; facies C and D ; Geological surface processes (geomorphology) ; outburst floods versus meteorological floods on fans ; overview of Lone Pine Canyon fan and catchment ; sedimentary facies and reconstructed depositional processes of Lone Pine Canyon fan ; Soil science, sedimentology
  • É parte de: Flood and Megaflood Processes and Deposits, 2002, Vol.17, p.111-140
  • Descrição: Surficial deposits of the Lone Pine alluvial fan, Owens Valley, California, mostly accumulated during a catastrophic outburst flood. Sedimentation probably resulted from failure of a glacial moraine‐dammed lake in the steep (15°), high relief (2.4 km), and high elevation (to 4417 m a.s.l.) Sierra Nevada catchment. Glacial moraines (facies A) consist of unsorted sand through boulders and blocks. The principal flood facies (B) is texturally similar to the moraine, consisting of unsorted, mostly matrix‐supported, sandy, pebbly, cobbly, blocky, fine to very coarse boulder gravel in a unit 2–11 m thick distributed across the 13.6‐km‐long fan. Facies B was deposited during the initial phase of the outburst flood as a high‐volume, noncohesive sediment gravity flow (NCSGF) probably initiated by water rapidly descending over moraine sediment. The NCSGF deposits differ from the moraine by their planar bed geometry, slope‐transverse long‐axis alignment of coarse clasts, and by shadow zones formed from flow separation around boulders deposited early in the flood. Deposition of the NCSGF was directly followed by a water flood phase caused by drainage of the breached lake after removal of sediment in the flood path. This discharge eroded channels 3–40 m deep and 6–100 m wide around the margins and across the fan from various departure points along the main flood channel (Lone Pine Creek). Laminated pebbly sand (facies D) accumulated on the channel beds. This discharge expanded on the distal fan into a sheetflood that deposited 4+ m of cobbly and sandy pebble gravel in planar couplet beds 5–20 cm thick (facies E). The final flood phase entailed downcutting of Lone Pine Creek, concentrating there a thick unit of boulder–cobble gravel (facies C), and stranding the other channels high on the fan surface. Minor modification of these facies and channels since the flood result from aeolian deposition (facies F), clast weathering, bioturbation and soil development. Instigation of outburst floods in Owens Valley requires the glacial repositioning of colluvium from the steep catchment slopes to moraines on the valley floor, which dam drainage and form lakes. Outburst floods differ from meteorological floods in the valley by the high volume of water and sediment discharge, by deposition of massive NCSGF beds, and by large and rapid changes to the landscape such as the carving of channels. These differences produce fans with distinctive facies and potential hazards, the former providing diagnostic criteria for their recognition in both modern and ancient settings.
  • Editor: United Kingdom: John Wiley & Sons, Incorporated
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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