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Titolo:
Fluvial incision and tectonic uplift across the Himalayas of central Nepal
Autore:
Lave, J; Avouac, JP;
Indirizzi:
CEA, Geophys Lab, F-91680 Bruyeres Le Chatel, France CEA Bruyeres Le Chatel France F-91680 F-91680 Bruyeres Le Chatel, France Lab Geodynam Chaines Alpines, F-38041 Grenoble, France Lab Geodynam Chaines Alpines Grenoble France F-38041 41 Grenoble, France
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
fascicolo: B11, volume: 106, anno: 2001,
pagine: 26561 - 26591
SICI:
0148-0227(20011110)106:B11<26561:FIATUA>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
GPS MEASUREMENTS; RIVER INCISION; GRAVITY-ANOMALIES; BEDROCK INCISION; STREAM POWER; EROSION; PROFILES; MODEL; ASIA; CONVERGENCE;
Tipo documento:
Review
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
110
Recensione:
Indirizzi per estratti:
Indirizzo: Lave, J CEA, Geophys Lab, F-91680 Bruyeres Le Chatel, France CEA BruyeresLe Chatel France F-91680 Bruyeres Le Chatel, France
Citazione:
J. Lave e J.P. Avouac, "Fluvial incision and tectonic uplift across the Himalayas of central Nepal", J GEO R-SOL, 106(B11), 2001, pp. 26561-26591

Abstract

The pattern of fluvial incision across the Himalayas of central Nepal is estimated from the distribution of Holocene and Pleistocene terraces and from the geometry of modem channels along major rivers draining across the range. The terraces provide good constraints on incision rates across the Himalayan frontal folds (Sub-Himalaya or Siwaliks Hills) where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces. Farther north and upstream, in the Lesser Himalaya, prominent fill terraces were deposited, probably during the late Pleistocene, and were subsequently incised. The amount of bedrock incision beneath the fill deposits is generally small, suggesting a slow rate of fluvial incision in the Lesser Himalaya. The terrace record is lost in the high range where the rivers are cutting steep gorges. To complement the terrace study, fluvial incision was also estimated from the modem channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate. This approach allows quantification of the effect of variations in channel slope, width, and discharge on the incision rate of a river; the determination of incision rates requires an additional lithological calibration. The two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared. In the Sub-Himalaya, river incision israpid, with values up to 10-15 mm/yr. It does not exceed a few millimetersper year in the Lesser Himalaya, and rises abruptly at the front of the high range to reach values of similar to4-8 mm/yr within a 50-km-wide zone that coincides with the position of the highest Himalayan peaks. Sediment yield derived from the measurement of suspended load in Himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range. The observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat-ramp-flat geometry of the Main Himalayan Thrust fault. The morphology of the range reflects a dynamic equilibrium between present-day tectonics and surface processes. The sharp relief together with the high uplift rates in the Higher Himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the Tibetan Plateau driven by late Cenozoic climate change, or late Miocene reactivation of the Main Central Thrust.

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Documento generato il 09/07/20 alle ore 20:51:45