Publication Date:
2022-05-25
Description:
Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 229 (2005): 287-302, doi:10.1016/j.epsl.2004.11.008.
Description:
The Indus River has been progressively transformed in the last decades into a tightly-regulated system
of dams and channels, to produce food and energy for the rapidly growing population of Pakistan.
Nevertheless, Indus River sands as far as the delta largely retain their distinct feldspar- and amphibole-rich
composition, which is unique with respect to all other major rivers draining the Alpine-Himalayan belt
except for the Brahmaputra. Both the Indus and Brahmaputra Rivers flow for half of their course along the
India-Asia suture zone, and receive major contributions from both Asian active-margin batholiths and
upper-amphibolite-facies domes rapidly exhumed at the Western and Eastern Himalayan syntaxes.
Composition of Indus sands changes repeatedly and markedly in Ladakh and Baltistan, indicating
overwhelming sediment flux from each successive tributary as the syntaxis is approached. Provenance
estimates based on our integrated petrographic-mineralogical dataset indicate that active-margin units
(Karakorum and Transhimalayan arcs) provide ~81% of the 250±50 106 t of sediments reaching the Tarbela
reservoir each year. Partitioning of such flux among tributaries and among source units allows us to
tentatively assess sediment yields from major sub-catchments. Extreme yields and erosion rates are
calculated for both the Karakorum Belt (up to 12,500±4700 t/km2 yr and 4.5±1.7 mm/yr for the Braldu
catchment) and Nanga Parbat Massif (8100±3500 t/km2 yr and 3.0±1.3 mm/yr). These values approach
denudation rates currently estimated for South Karakorum and Nanga Parbat crustal-scale antiforms, and
highlight the major influence that rapid tectonic uplift and focused glacial and fluvial erosion of young
metamorphic massifs around the Western Himalayan Syntaxis have on sediment budgets of the Indus
system.
Detailed information on bulk petrography and heavy minerals of modern Indus sands not only
represents an effective independent method to constrain denudation rates obtained from temperature-time
histories of exposed bedrock, but also provides an actualistic reference for collision-orogen provenance, and
gives us a key to interpreting provenance and paleodrainage changes recorded by clastic wedges deposited
in the Himalayan foreland basin and Arabian Sea during the Cenozoic.
Description:
Financial support by FIRB 2002 and PRIN 2003 to E.Garzanti.
Keywords:
Modern sands
;
Bulk petrography
;
Heavy minerals
;
Sediment budgets
;
Collision orogens
;
Karakorum
;
Nanga Parbat
;
Himalaya
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
1103015 bytes
Format:
1221213 bytes
Format:
application/pdf
Format:
application/pdf
