Accepted Article Gujarat, India India Gujarat, DH1 3LE, UK * 3 2 1 Densmore Alexander L. river morphology and evolution pigg Himalayan from release and storage Sediment Article type : Original Article Accepted Date : 16-Jan-2015 : 06-Jan-2015 Date Revised Received: Date 19-Jun-2014 This article This protectedis by Allcopyright. rights reserved. 10.1111/bre.12116 doi: lead to differences betweenversionthis and the Versionof Record. Please cite this article as through thebeen typesetting,copyediting, pa This article hasbeen accepted for publicationand undergone fullpeer review but has not abandonment of the depositional unit and a basinward shift of the active depocentre. Excavation of of Excavation depocentre. active of the shift basinward a and unit depositional of the abandonment to leading incision, fan-head rapid (apparently) and backfilling by followed was phases these of Each dun. the into fans sediment of progradation by accompanied ka, each 23-10 and ka, ka,34-21 ~41-33 threemajo for evidence we show dating, on OSL Based India. northwestern in front mountain theHimalayan along developed basin piggyback Dun, a the Dehra in release and storage sediment of volumes and timing the investigate we Here reaches. the affects basins piggyback in ofsediment release transient, sediment storesalongmajor systems. It isclear,river not however, how storagethe and and important, as act can orogens collisional of fronts mountain atthe developed basins Piggyback Abstract Corresponding author: email [email protected] [email protected] email author: Corresponding Division Sciences, of Indian Earth Instit 208016India (UP), Kanpur of Technology Kanpur, Sciences, Institute Indian Earth of Department Durham University, Durham Geography, of Department and Resilience and Risk ofHazard, Institute 1* , Rajiv Sinha

2 , Swati Sinha Swati , ute of Technology Ga Technology of ute r phases of aggradation in the dun, bracketed at at bracketed dun, the in ofaggradation phases r gination and process, which proofreading may 2 , S.K. Tandon , S.K. sediment flux and evolutionof downstream river yback basins and implications for downstream downstream for implications and basins yback ndhinagar, Ah ndhinagar, 2 , and Vikrant Jain Vikrant and , medabad 382424, medabad 3 Accepted Article other intermediate sediment stores is thus a critical control on long-term sediment efflux, not least least not efflux, sediment long-term on control critical a is thus stores sediment intermediate other or basins piggyback in of sediment release and trapping Temporary 2005). Strecker, and Hilley 1991; Himalayas, Ganga River basin, sediment transport, transport, sediment basin, River Ganga Himalayas, Keywords variations in collisionalother mountain belts. flux sediment understanding for important be may and Rivers, Kosi and Gandak the including front, Himalayan the along systems river major other of features morphological explain to appears model conceptual This capacity. transport or supply sediment hinterland in variations temporal amplify to acts dunthus The Basin. Ganga the export to sediment of periods major with coincide excavation, sediment ofdun times especially and aggradation, of dun stages that late but aggradation hinterland widespread of periods with coincides generally dun in the storage sediment that show Ganga the in aggradation and incision of records and downstream upstream with and release storage together comprise area that drainage of 1.5% the areas catchment from derived is sediment this dun; the of themargins traverse that rivers Yamuna su modern of the were ~1-2% that discharges sediment time-averaged produced of aggradation phases third and thesecond after dun sediment This article is protected by copyright. All rights reserved. time scales (10 ma basins piggyback that haveshown studies several buriedare the fold as belt and migratesthrust into the foreland (e.g., DeCelles and Horton, 2003), beessentially may basins such While depocentres. and Giles, 1996), and as links serve between hinterland areas of sediment production and foreland of forel features ubiquitous basins are Piggyback Introduction 3 –10 4 years), with repeated cycles of aggradat cycles repeated with years), spended-sediment discharges of the Ganga and and theGanga of discharges spended-sediment and basin systems (Ori and Friend, 1984;DeCelles systemsand basin Friend, and (Ori of these rivers.of the timingofof these Comparison dun sediment storage, erosion, sediment valley intermontane passive features that fill with sediment and then and sediment with thatfill features passive y be highly dynamic environments on shorter shorter on environments dynamic be highly y

ion and incision DeCelles (e.g., et al., Accepted Article along individual segmentsof the mountain front (Nakata, 1972; Raiverman, Powers1997; etal., ‘duns’ or basins piggyback frontal by characterized are which of portions front, mountain Himalayan the along release and storage sediment on focusing by this problem toaddress begin we Here, 2006). Clift, (e.g., scarce comparatively are systems river large in examples (e.g.,Lane and Richards, 1997;Malmon etal., 2005; Lancaster and Casebeer, 2007), but field scales spatial small atrelatively or 2005), Lucazeau, and Carretier 2000; Densmore, and Allen 2000; analogue experiments (e.g., Kim etal., 2006; Powell et al., 2012) and numerical simulations (Paola, remainsrelativelyof li sedimentstorage and release and Törnqvist, 2000; Bloethe and Korup, 2013), butour understanding of the downstream impacts produced in upstreamcatchment of a parts (e.g., sediment the of proportion a large for account can storage intermediate that known been long has It Driessche, 2003).den andvan (Castelltort conditions forcing external in changes against thesystem can buffer storage such because This article is protected by copyright. All rights reserved. systems. Himalayan large river of geomorphology on the dun a of absence or presence the of effects the and foreland, tothe supply sediment setting in duns of role the duns, the from evacuation and storage sediment of timing and rates the assess to opportunity an provides thus region This 1). (Fig. foreland the into directly –flow Kosi and Karnali, Ghaghra, the –including others whereas basin, foreland the into debouching before duns these across –flow Gandak and Ganga, Yamuna, the including – systems river Himalayan system (Nakata, 1989; Yeats etal., 1992; Wesnousky al.,et 1999;Thakur, 2013). Some of the main (HFT) Thrust Frontal Himalayan the on slip of distribution and geometry the in variations along-strike 1998; Thakur Pandey,and2004; Thakur etal., 2007) Meade, 1982; Walling, 1983; Phillips, Blum 1991; mited. These impacts have been investigated investigated in Theseimpacts have been mited. . These . These duns are formed inresponse to marked

Accepted Article foreland morphology and evolution of foreland rivers foreland of evolution and morphology foreland Ri Kosi and theGandak from observations against 2011; 2012). modelconceptual Gibling al., al., Finally, Roy we the (e.g., et et evaluate foreland and 2010) Srivastava, and (Ray hinterland the in Yamuna rivers and Ganga the for documented epis with thedun in events compare to and period, model toestimate thevolumes that of sediment this use ka. We ~40 since evolution dun of model conceptual a into dun the in deposits sedimentary of age and geometry the on data published and new combine We system. routing sediment Ganga the in of thedun role the evaluate to us allows and regions, these between gap the fills work Our plain. Ganga the in incision and accumulation sediment of records downstream with this and linked hinterla the mountain in incision and aggradation prov (2010) Srivastava and Ray system. river a large in discharge of sediment magnitude and timing the influence can basins piggyback proximal to which thedegree examine to this example use We rivers. Ganga and Yamuna the Basin, Ganga the of rivers thelargest of two by traversed is which India, northwestern in Dun Dehra the on initially focus We This article is protected by copyright. All rights reserved. They suggested basins. piggyback or wedge-top stable large thus and front thethrust of propagation Siwalik deposits and a slightly steeper (2 the HFT have propagated into the foreland. For example, Mugnier al. et showed (1999b) that thicker of strands which to extent the in differences to leading 1999b), 1999a, etal., (Mugnier properties lithosphere and(Yeats Lillie, 1991; Raiverman or 1993) etal., lateralvariations orogenicin wedge Indian theunderlying on structures including factors, different of number a to linked been has 1) (Fig. front mountain Himalayan ofthe segments all, not but some, along duns of development The Setting areaStudy store. dun sediment ° ) dip of the basal detachmentwould produce early have been stored and released over this time time over this released and been stored have nd of the Ganga Basin upstream of the Dehra dun, Dehra dun, of the upstream Basin Ganga the of nd vers, and show that fundamental differences in the in differences thatfundamental show and vers, odes of aggradation and incision that have been have been that incision and ofaggradation odes ided a comprehensive review of the evidence for for theevidence of comprehensive review a ided can be linked to the presence or absence of a a of absence or presence the to belinked can

Accepted Article the Mohand anticline over a ramp in the HFT, which has remained active into the Holocene Holocene the into active remained has which HFT, the in a ramp over anticline Mohand the northern state, Uttarakhand in 2), Dun (Fig. Dehra The The Dehra Dun 1). (Fig. rivers Himalayan major the of some only affects and front, Himalayan the along limited isspatially development dun isthat purposes our for important fr thethrust from frequently shifts deformation and is episodic faults individual on but activity basins, wedge-top of formation and theforeland into of slip propagation rapid to leads contrast, in detachment, Aweak front. thrust the at deformation of localization and wedge of the propagation regular to leads detachment (high-viscosity) frictional th controls coversequence, of the strength the extent a lesser to and detachment, basal ofthe thestrength that demonstrated contrast, in (2010), Simpson foreland. the into faulting of propagation and thetiming controlling by development, of th or deposition erosion that argued (2000) si a via form might duns Chitwan theDehraand that This article is protected by copyright. All rights reserved. 2010). al., (Sinha Ganga et and al., 2012) et (Dutta Yamuna both the along terraces fill of sequences by recorded is dun the within erosion and aggradation of history late-Quaternary complex A attheHFT. rivers Ganga and Yamuna the of discharge thesediment on impact direct a has dun the the thatdrain channels the for level base and set ma thelateral traverse rivers Ganga and Yamuna The (Fig. 2). (MBT) Thrust Boundary Main the and HFT the both on slip by controlled is thedun in generation Accommodation 2011). al., and dun formation isconstrained afterto kabefore~500 but 220ka (Thakur al., 2007;Barneset et Mi of conglomerates and sandstones Siwalik Upper (Wesnousky etal.,The 1999). anticline is an upright, asymmetric foldcomposed of Middle and e wedge could promote or suppress piggyback basin basin piggyback suppress or promote could wedge e e sequence and propagation of deformation. A deformation. of propagation and e sequence ont to structures in the hinterland. What is is What hinterland. the in structures to ont dun. Thus, any storage or erosion of sediments in in of sediments erosion or storage any Thus, dun. ocenePleistoceneonset to of age; the folding milar mechanism. More generally, Leturmy et al. etal. Leturmy generally, More mechanism. milar rgins of the dun before entering the foreland, theforeland, entering before thedun of rgins India, has developed in response to folding of of to folding response in developed has India,

Accepted Article volumetric discharge of 6.8 Mm 6.8 of discharge volumetric Mt/yr), respectively. Ganga sediment discharge estimates of 20-30 Mm of20-30 estimates discharge sediment Ganga used (2012) etal. and Lupker (2003) al. Vance et Mm Mt/yr bed Paonta,or sample 13±5 of sedimentdischarge from within5.3 total todun, a estimate the downstream of the HFT; assuming a solid grain density of 2650 kg/m of 2650 density grain solid a assuming HFT; of the downstream just Tajewala, at Mt/yr of 18 Yamuna forthe discharge sediment suspended a present-day estimate yearto a single for sediment suspended of measurements used (1988) al. et Jha scales. time different over several quantified been has basins, these of rates erosion thehinterland alternatively Sediment supply from theGanga and Yamuna rivers at the Himalayan mountain front, or 2010). and ka, ~18-11 with incision beginning soon after 11ka (Srivastava al.,et 2008;Ray and Srivastava, broadl which Basin, Ganga the in sites of upstream ma records These are 2010). 11-9.7 kaal., et (Sinha period span shorterterraces time a TheGanga 2012). etal., (Dutta theHolocene within cycles incision and aggradation minor several with along abandonment, terrace and incision by followed each ka, to12 >15 ka and 24 to >37 from aggradation of phases major record 2) (Fig. MBT of the footwall the in terraces Yamuna The This article is protected by copyright. All rights reserved. available for this estimate. These correspond to volumetric discharges of ~5 Mm ~5 of discharges volumetric to correspond These estimate. this for available 33 Mt/yr on the basisofGaly and France-Lanord (2001),but further supporting analysis isnot of value cited a Wasson (2003) and 2009), Saini, al., and Chakrapani 2005; Sinhaet Subramian, 1984; and (Abbas 13-14 Mt/yr or atRishikesh sediment are Haridwar measurements suspended 3 /yr. Values for the Ganga vary more widely. moreGanga vary /yr. the Valuesfor 3 /yr. Lupker al. used et (2012) cosmogenic radionuclide analysis of a , but also record aggradation to ~11 ka followed by incision from from incision by kafollowed ~11 to aggradation record also but , cosmogenic radionuclides to derive longer-term longer-term derive to radionuclides cosmogenic Reported present-day discharge estimates from estimates discharge present-day Reported 3 y indicate phases of aggradation from ~49-25 ka ~49-25 from aggradation of phases y indicate /yr 65-67 (or Mt/yr) and 52Mm tched by evidence from fill terraces at a number number ata fillterraces from evidence by tched

3 , this corresponds to a a to corresponds this , 3 /yr. In contrast, contrast, In /yr. 3 /yr (or 139±37 /yr (or Accepted Article and exposed Siwalik bedrock were collected using handheld GPS and 1:50,000 Survey of India India of Survey 1:50,000 and GPS handheld using collected were bedrock Siwalik and exposed field Inaddition, thicknesses. deposit minimum fan establish and transitions lithological major the map order to the dun in within locations for Nigam Jal Pradesh Uttar from logs borehole 118 of atotal obtained also We DEM. the from created raster a gradient and data,theDEM, LISS-3 the from created image (NDVI) Index Vegetation Difference Normal a images, composite false-colour the of basis the on done was surfaces terrace and fan green and red, near-infrared, data, using LISS-3 the cell size a with False-colour 90m. (DEM),elevation of model fromcomposite imageswereprepared digital 4 version Mission Topography Radar Shuttle CGIAR-CSI andthe 2004 from resolution) spatial Dehra showing Dun major fan the andsurfaces fill terraces, using satelliteLISS-3 images m (23.5 thedun storage sedimentvolumesTo in assess and Methods here. nomenclature this adopt we and 2) (Fig. fans Bhogpur and Dehradun, theDonga, are these east, to west from dun; the within fans depositional main three identified and classification this extended Ganga upstream of the (34,300HFT km Yamunaand the of area catchment thetotal of 1.5% about represents this MBT; the of upstream fill of the Dehra Dun, and classified it into classified itinto seve and Dun, theDehra fill of thesedimentary mapped (1972) andNakata (1971) Nossin 2). (Fig MBT the and fault Santaugarh the backfille have deposits fan of generation youngest over foldedthrust and MiddleSiwalik are dun, rocks cobbleconglomerates, atop Upperbedrock Siwalik (Singh Atthe et al., northern edge2001). of the flow and debris-flow fans that have deposited a thick sequence of sediment, ranging from silts to catchments that drain the hanging wall of the MBT (Fig. 2), with a total area of about 503 km 503 of about area total a with 2), (Fig. theMBT of wall hanging the drain that catchments of set a by rivers, Ganga and Yamuna the to thus and dun, the to supplied also is Sediment This article is protected by copyright. All rights reserved. 2 ). These dun catchments feed a set of coalescing stream- coalescing of set a feed catchments dun ). These ral discrete fan and terrace andterrace fan ral discrete d paleovalleys eroded into the hanging walls of thehanging into d paleovalleys eroded bands. Identification and correlation of different different of correlation and Identification bands. , we prepared geomorphic maps of the central geomorphic we prepared the of maps , data on elevations of the Quaternary surfaces surfaces elevations on theQuaternary data of the fan deposits (Thakur et al., 2007), et the while (Thakur fandeposits the

units. Singh et al. (2001) (2001) etal. units. Singh 2

Accepted Article units); we also ensured that the interpolated surfaces were bounded by the MBT and by the present- the by and MBT the by bounded were surfaces theinterpolated that ensured we also units); depositional older or bedrock (either topography higher older, below dipped they where truncated constr were surfaces These ArcGIS. in functions surfaces smooth interpolated then We constraints. age OSL available and vegetation, texture, image and morphology surface elevation, using correla we this, To do incision. by unit each from depositional of we volumes themajor estimated the Rivers, Ganga and theYamuna to evacuation and storage sediment of dun contribution the To assess dun. the in episodes aggradational major of geometry and timing the constrain the geomorphic withmaps and existing OSL dates (Singh etal., 2001; Thakur et al., 2007) to with integrated were data These procedures). analytical and methods for Material Supplementary (see deposits thefan within silt coarse and sand very fine to of fine beds from dating (OSL) geomorphicof Wecollected surfaces. mapped the si most of deposits sub-surface the characterise to prepared were logs Stratigraphic maps. topographic This article is protected by copyright. All rights reserved. subsur clear or incision of depth the of evidence elevatio present-day below dun the in elevations floors. previous volume assume that estimates The valley the along thicknesses sediment thepresent-day exceed not did and reasonable geologically boreho the from thicknesses fill sediment minimum against patterns our incision checked also We below. arereported interpolations polynomial order polynomials, and found that the estimated volumes differed by fifth-order and fourth, third, using interpolations of results the compared We abandonment. toyield the can summed be surface, which each into incision post-abandonment of pattern spatial and thedepth estimated we topography, present-day the from surfaces theinterpolated Bysubtracting fans. the of day boundaries volume of sediment that was removedduring sediment that of volume ained to include the mapped remnants, and were were and remnants, mapped the to include ained face distinctions between different depositional depositional different between distinctions face ted remnant depositional surfaces across the fans fans the across surfaces depositional ted remnant ns, and are thus minima; however, we lack any lack we however, minima; arethus and ns, episodes of incision did not lower thalweg thalweg lower not did incision of episodes polynomial using remnants thecorrelated across le logs,le toensureth units, and of the material that was removed x samples for optically-stimulated luminescence

≤ soonly results5%, using fourth- at the estimates were theestimateswere at Accepted Article of Singh (2001), etal. and unit Aof Thakur etal. (2007);‘proximal the (2) fan’ unit, which GD-I unit depositional and unit geomorphic Hills’ Siwalik ‘Pedimented the to corresponds which unit, hills’ ‘isolated the termed(1) here are 2) (Fig. units key depositional these youngest, to oldest From dun. thepresent-day of formation the clearly pre-date 2001),which Siwalik Singh al., et of Hills’ ‘Dissected (the fault Santaugarh of the wall hanging the in deposits older and the 1972) dun (Nakata, spatially-rest more younger, the both ignore and fans, units depositional important volumetrically most Singh etal. (2001), we focus here on the geometry and ages of deposits. the concentrate We on the Because detailedthe stratigraphy of the sedimentaryfill described Dun the by been Dehra has in units depositional of timing and Geometry Results dun. the out of discharges constraints sediment removal provided time the with of volumes our combined we Finally, be addressed. cannot limitation this present at so units, This article is protected by copyright. All rights reserved. also and fan, Dehradun the on unit this of base the kanear 38.3±9.4 and of40.3±3.9 ages OSL on based ka ~50 of age abasal inferred (2001) al. et Singh unknown. is unit this of thickness actual footwall in theimmediate wide, km 2-4 belt, narrow toa limited is unit this of Exposure 3). 2, (Fig. dun of the parts central and western in the River) theAsan and River, theSuarna Rao, (Sitla dun rivers major the flank m that 880 of620- elevations reach that hills rounded form deposits These 2001). al., et (Singh conglomerates toboulder pebble or matrix-supported clast- massive, composed of unit is hills isolated The (2007). etal. Thakur of C andunit (2001), etal. Singh of GD-IV and GD-III ‘distal f the (2007);and(3) al. et of Thakur unit B corresponds to the Piedmont geomorphic unit and depositional unitGD-II of Singh et al. (2001), and of the Santaugarh fault. The exposed thickness is at least 90 m, but the 90m,the but atleast thickness exposed The is fault. ofSantaugarh the an’ unit, which corresponds to depositional units depositional to corresponds which unit, an’ that comprise the Donga, Dehradun, and Bhogpur Bhogpur and Dehradun, Donga, the comprise that by the OSL dates to estimate average tosediment dates average estimate OSL by the ricted fill terrace deposits along streams in the the in streams along terracedeposits fill ricted

Accepted Article (Fig. 3A) and the Suarna River. In the Santaugarh fault hanging wall, deposits of the proximal fan unit unit fan proximal the of deposits wall, hanging fault Santaugarh the In River. theSuarna and 3A) (Fig. Nadi Koti the including drainages, dun major the of several along fault Santaugarh the of upstream km 1.5 to up continuously traced be can deposits underlying their and surfaces the Importantly, fault. Santaugarh the of footwall the in hills isolated underlying the of deposits onto onlap surfaces have typical slopessurface (averagedover 270mwindows) of 2-4 degrees, and appear to fan These fan). Bhogpur the (for theMBT or fans) Dehradun and Donga (for the fault Santaugarh the of km downstream 5-10 extend and 2), (Fig. fans Bhogpur and Dehradun, Donga, ofthe areas proximal the of cover most that 3A) (Fig. surfaces fan near-planar south-dipping smooth, underlies sandlayers(Sin with conglomerates some interbedded boulder to pebble matrix-supported or clast- of massive, consists unit fan proximal The 1). Table 2, (Fig. valley River of theSuarna flank east on the sediment hills isolated of exposure ofDonga the fan. Our sample IH/2yields an of age41.3±1.2 ka from 2.8mbelow thetop of an parts proximal from both unit, this kafrom 33.57±4.73 and 35.40±7.30 of ages OSL reported (2007) al. et Thakur certain. not is position its although fan, theDonga ka from 29.5±5.0 of anage reported This article is protected by copyright. All rights reserved. correla this basisalthough for the 2001), al., et (Singh valley River Suarna of the flank west the from ka of 29.4±1.7 age an with unit this correlated and B, unit their ka from 20.5±1.8 of age anOSL obtained (2007) al. et Thakur directly. observed be cannot width their that means of offsetfrom paleovalleysslightly are these deposits th of theunderlying m into 70-75 least at deposite were sediments fan proximal that indicate River Suarna and Nadi Koti both the along Exposures fault. Santaugarh the across deformation or offset of evidence no is there that show observations our but unit, hills isolated and the 2007) etal., (Thakur sandstones Siwalik Middle overturned to steeply-dipping atop unconformably lie tion is not clear. We obtained an OSL age of 21.2±1.3 ka from ka from 21.2±1.3 of age anOSL obtained We clear. not is tion those of the modern river drainage system, which which system, drainage river modern the of those e isolated hills (Fig. 3B). The axes and orientations orientations and axes hills 3B).The isolated e (Fig. d in steep-walled paleovalleys that were incised incised thatwere paleovalleys steep-walled d in gh et al., 2001; Thakur et al., 2007). unit Thakur 2001; The gh etal., et

Accepted Article while incisionon Dehradun the (Fig. 4)and Bhogpur fans has yielded 750Mm sample (FS1.1) yieldedOSL age of 33.8±3.2 an ka from 3mbelow thefan surface (Fig. 2, Table 1), A final 1). (Table FS2.1) ka(sample 13.8±0.9 and LIS-TOP) ka (sample 16.2±1.4 of ages OSL yielded 2), River (Fig. Suarna the of east from collected samples, other Two 1). Table 2, (Fig. surface fan an ageOSL of 14.4±0.6ka from sample on FS2.2 west flank the of Rao,Sitla the mbelow 5 distal the (2007) reported ages of 13.2±1.1 and 17.1±2.0 ka from distalthe DongaLikewise, fan. obtainedwe etal. Thakur while thetop, near ka and 10.7±2.4 9.4±0.6 of ages and unit, this of thebase from near windows) of to1.1degrees.0.2 Singh et reportedal. (2001) OSL ages of 22.8±2.3 and 20.3±7.5 ka m over270 (averaged slopes surface typical with fans, Dehradun and Donga the of expanses surfaces the proximalof isolated fan and surfaces hills units. These form the southern, distal that surfaces fan near-planar smooth, widespread, 2007). unitunderlies etal., The Thakur silt2001; discontinuous etal., and layers (Singh sand of some with conglomerates, cobble pebble ofwell-bedded to consists unit The fan distal River valley 2,(Fig. Table 1). Suarna the of flank east the on fault, theSantaugarh near surface fan the m below 10 FS3.1 sample This article is protected by copyright. All rights reserved. on Donga the fan (Fig. 4)has yielded Mm 1900 unit fan proximal the of Incision units. fan distal and proximal the of incision on only focus therefore We incision. post-depositional dueto beenremoved has that material of volume the estimate cannot we preserved, is not unit hills isolated the of surface depositional original the Because Erosional volume estimates pres but at fan unit, proximal the of exposure distal isolated an from collected was sample this that possible is it units, different the between difference textural clear of a the lack and units, depositional dun the of limit thesouthern near position its Given unit. fan distal forthe age otherreported any than older substantially is which ent we cannot resolve this apparent discrepancy. discrepancy. apparent this resolve cannot ent we 3 of sediment since abandonment of the surface, surface, the of abandonment since ofsediment occur south of, and appear to onlap against, against, onlap to appear and of, south occur

3 and 720Mm 3 , Accepted Article by major a basinward shiftof the active locusof deposition. This shift was followed bywidespread and thebasin into points entry sediment the near deposits hills isolated the of incision by occurred regi depositional hills isolated of the abandonment Based incised. and abandoned was unit depositional mate hills isolated the on dates use to impossible emplacement such th erosion, that morphological expression 41 ka.The thisunit of least byat starting and and MBT fault Santaugarh the on slip by produced thatwas accommodation In thismodel, theisolated mechanisms. hills unit 2008) etal., Duehnforth 2007; Davies andKorup, andallogenic (e.g., 2010) etal., et al., Pepin 2010; and triggeredmay be by autogenicboth (e.g., Kimand Muto, 2007;Kim and Jerolmack, 2008; Clarke experimental fans and fan deltas (Kim et al., 2006;Reitz and Jerolmack 2012; Powell etal., 2012), evolutio an Such depocenter. of the migration sequence repeatedof episodes deposition, of fan backfilling,head fan incision, and basinward deposi were that units thesedimentary interpret We Evolution of dunthe fill Discussion co remnant possible different of exploration through ±20% at estimated conservatively are and remnants, fansurface the mapping in uncertainties to largely aredue volumes these on estimates Error surface. fan distal of the abandonment dun. As deposition progressed, the unit began to backfill toward, and eventually across, the across, eventually and toward, backfill to began unit the progressed, deposition As dun. deposition of proximalthe fan unit, which filled much of the available accommodation within the incision of distal the unit onDonga the and Dehradun fanshasyielded Mm 1800 but fan, theBhogpur on exposed not is unit fan distal The fan unit. proximal the of by incision respectively. to3300 up Mm In total,add these This article is protected by copyright. All rights reserved. e original fan surface topography is not preserved. It is thus is thus It preserved. isnot topography surface fan original e nary sequence has been widely documented for for documented widely been has sequence nary 3 of sediment that has been evacuated from the dun thedun from been evacuated has that of sediment indicates that it has undergone widespread post- widespread undergone has thatit indicates represents thefirstpha represents rial to identify the precise time at this which at time theprecise rial to identify me appears to have taken place by 29-30 ka, and and ka, 29-30 by place have taken to appears me nfigurations with various levels various certainty. with levels of nfigurations on dates from the next-youngest unit, however, however, unit, next-youngest the from dates on ted in the Dehra Dun since ~41 ka a termsof ~41 in since Dun Dehra ted inthe

se of deposition,se of filling 3 since Accepted Article sediment storage along the river corridors within the dun. Likewise, abandonment of the distal fan fan distal ofthe abandonment Likewise, dun. the within corridors river the along storage sediment for available accommodation limited is only there because time period, this during dun the traversed they as rivers Yamuna and Ganga the of loads thesediment to added have been must discharge This assumption yields a time-averaged sediment discharge from the proximal fan unit of 0.26 Mm of0.26 unit fan proximal the from discharge sediment time-averaged a yields assumption This than that. shorter times several be may truevalue the that kyr, noting of 13 duration incision an estimate, conservative a as take, therefore ka. We 10 at surface fan distal later the of abandonment the before well concluded have been must it but known, not is episode incision this incision along the major dun rivers. This evacuation must have started at 20.5-23 ka. The duration of thus likely to be volumetricallyinsignificant be in likelythus to are and levels, bed river modern the m of 5-10 within thatare treads have Rao, andSitla Suarna the of themajordun rivers(Nakata, Singh1972; etal., These terraces,2001). while well-developed along to leading incision, and episodes of aggradation minor several been therehave ka, After10 network. valley and topography thepresent-day carved has that incision of phase major a entered network river the when ka, 10 by about abandoned was turn, in unit, fan distal The wall. hanging fault Santaugarh the in deposited were fan sediments distal no and unit, fan proximal of the deposition the during as north far as extend not did this so but if backfilling, to led eventually have may unit fan thedistal of Deposition unit). fan proximal the in age youngest ka (the 20.5 and fan unit) thedistal in age oldest (the ka 23 about between place took shift This fan unit. distal of the deposition to leading locus, of thedepositional shift basinward a second to appears deposit fan proximal of the Abandonment 3B, (Figs. 4). fault the of wall hanging the in sediment m of of >100 thedeposition to leading eventually fault, Santaugarh This article is protected by copyright. All rights reserved. Mm of 3300 evacuation to led unit fan proximal of the Abandonment fluxes Sediment comparisondepositional units. with threemajor the sequences of low Holocene fill terraces along along some fillterraces Holocene low of sequences have occurred by incision at the fan heads and and heads fan the at incision by have occurred

3 of sediment, primarily via via primarily sediment, of 3 /yr. /yr. Accepted Article regional-scale climatic variability; the latter cont the climatic variability; regional-scale and processes autogenic by of driven been combination some thedunhas and evacuation in storage likely seems more that temporal variability sediment onset next. of It in deposition the the of and unit one of abandonment the behind mechanism underlying the as generation accommodation appear both oftheproximal unit, fan deposition after to be notappear does thatthere our observation and emplaced, were Dehra in Dun the units depositional the which major over time scale short The records sedimentary and foreland hinterland to Comparisons discharge has varied through the late Quaternary. that how (2) or components, suspended-load and bedload both including discharge, sediment total corresponding the (1) either know not we do and values, discharge time-averaged the for context some toprovide simply made is values discharge sediment suspended present-day available with comparison our Also, estimates. conservative our than higher times many be could values th abandonment, following years of thousands few each depositional unit. For example, if incision and sediment evacuationwere focused in the first of abandonment during incision of duration the on bounds maximum only provide ages depositional true the underestimate certainly almost here catchment-averagedoverallthe values. Westresst Yamuna and Ganga the for source sediment important an represents thus excavation Dun area. drainage Yamuna and Ganga combined ofthe 1.5% discharge sediment suspended summed present-day the of 1-2% represent dun the from discharges sediment time-averaged these comparison, For This corresponds time-averaged to a 0.18Mm of sediment discharge unit led to evacuation of 1820 Mm 1820 of evacuation to led unit This article is protected by copyright. All rights reserved. 3 of sediment since 10 ka, directed into the Yamuna River only. only. Yamuna River the into directed ka, 10 since ofsediment sediment discharge from the dun, because our our because dun, the from discharge sediment rol has been argued convincingly for the Ganga Ganga for the convincingly beenargued has rol en the ‘true’ time-averaged sediment discharge discharge sediment ‘true’ time-averaged the en hat the time-averaged discharge values reported reported values discharge time-averaged hat the substantial slip on the Santaugarh fault during or or during fault Santaugarh on the slip substantial of the Ganga and Yamuna rivers, derived from from derived rivers, Yamuna and Ganga of the to rule out major changes in fault slip andrate rivers, with sediment yields comparable to to comparable yields sediment with rivers,

3 /yr over that time period. period. /yrtime that over Accepted Article indicating that the controls on sediment aggradation and incision in the hinterland oftheGanga thehinterland in incision and aggradation onsediment thecontrols that indicating framework, this with closely ka,agree 23-10 and 34-21, at~41-33, aggradation with Dehra Dun, andgeochemicalet al.,sedimentary (Juyal2009) (G ka,including 15 after discharge, river thus and strength, monsoonal forincreasing evidence of oflines on anumber based was inference This exhaustion. sediment post-LGM with combined ka, 9 15 at ka, after peaking monsoon toprecipitation (2010) increased by andSrivastava Ray transit toglacial-deglacial due supply sediment high on clustering of OSL ages in terrace fill deposits. attributed They these aggradational episodes to ka based ka and 18-11 at 49-25 aggradation ofvalley phases formajor dating, andargued new OSL of and Srivastava(2010) thedun, coRayUpstream study area. the of downstream and upstream both basin, Ganga the in episodes incision unit depositional our contrast and compare therefore 2005; Sinha and Sarkar, 2009; Roy etal., To 2012). understand widerthe context our of results, we al., et Gibling (e.g., andforeland 2010) Ray andSrivastava, al., 2009; et (e.g., Juyal hinterland basin This article is protected by copyright. All rights reserved. depositional to havegiven discrete events that rise units. distinct aggradational spatially they represent in overlap time, episodes ofour ranges aggradational possibilitywhilealsoofinterveningepisodes.erosional the Thus, age raised the (2014) Pandey al. et geometrical distinctiondepositiondifferent between that (2014) al. et Pandey by theconclusion with however, disagree, We ka. and 10 >40 between thedun in aggradation ofalluvial phases multiple for argued who etal. (2014), Pandey of summary and interpretation the with agree broadly also results Our variations. climatic tolarge-scale age of the constraints, uncertainties within the hinterland, with the near-synchronously andresponds catchment Ganga the of part integral an forms thus dun the Unsurprisingly, dun. the of response the set also catchment fan aggradation had been continuous over hadbeen fan aggradation mpiled a number of published studies, published anumberof along mpiled with ions. Widespread incision after 11 ka linked 11 was after incision Widespread ions. al al units et al., 2001)(Singh we note that – and aly et al., 2008) records.results fromaly the etal., Our 2008) chronology to the timing of valley filling and

this period, because of the clear clear because of the this period, Accepted Article through the river systems during 41-33 ka, perhaps combined with high hinterland sediment supply supply sediment high hinterland with ka, combined perhaps the river 41-33 through systems during volumetri are but these 2012), al., et (Roy recorded 37 to dated fills channel Minor valley. Ganga the modelled (1987), is but there by Prell andKutzbach li ka as ~40 around precipitation (Roy et al.,and declining 2012) plains in the Ganga floodplain the of lowering with dun coincides the in ka 41 by began that phase depositional hills isolated The below. ourchronology with observations compare these We of incision. by episodes ka ka, and 16-11 separated at30-23 phases accumulation major suggested and studies, existing number of a from results with HFT, the of downstream Roy et al. (2012)combined new stratigraphic observations in the central Ganga plains, about 300km kaatdifferent to7 from 13 varying incision of onset the with channel, Ganga present-day the toform byincision followed was pulse second The ka. at 13-6 asecond and al., 2007), et bySinha also (seen ka 26 onebefore foreland: to the delivery ofsediment pulses main argued fortwo (2010) andSrivastava thedun, Ray of Downstream This article is protected by copyright. All rights reserved. and Sarkar, Sinha 2006; al., et Tandon 2003; (Goodbred, plains Ganga the in dun the of downstream with a peri and overlaps fanunit, proximal the of development by the represented is ka) (34-21 dun the in aggradation major of phase second The systems. would which processes, mass-flow orother flow debris- of result the as this phase in deposits of the many interpreted etal. (2001) Singh that note fr extending oftransects analyses sedimentological to would need be careful This hypothesis tested with period. this during aggradation and local sedimen large to transport insufficient but was dun, the andin theHFT of upstream of sediment deposition led widespread to 2010), and Srivastava, (Ray locations between the HFT and Kanpur. More recently, More and Kanpur. theHFT between locations ka and levee deposits dated to 34 ka have been kahave 34 to dated deposits and levee ka od of widespread fluvial aggradation recorded recorded aggradation fluvial widespread of od om the dun into the northern foreland. We also also We foreland. northern the into dun the om not require high water discharges in the river t volumes leading theplains, to onlyinto minor callysmall. Itbe may that relatively weak flow mited, evidenceif any, aggradation for within

Accepted Article Ganga plains upstream of Kanpur (Gibling et al., 2005; et al., (Gibling Kanpur of upstream Ganga plains neverglaciated. andwas areas Himalayan Lesser in because this period the dun thedunduring occurred drains only catchment lower-elevation area whatfraction of the distal fan unit was emplacedduring thistime, but it may be that deposition know do not we et 2009); al., Rahaman (e.g., elevations high at cover glacial and supply sediment tolimited due perhaps 2010), Srivastava, and (Ray period this during limited was hinterland lower thedunbyemplacement in of the pa recorded is deposition (LGM), Maximum Glacial Last the ka,including to 16 28 from the period During theforeland. into directly supply of sediment rates high to and it supply that rivers by the dunaccommodation of tobypass full, leading essentially was stage this dun at of of unit on thefloor that thewide Given thefan extent the 1996). proximal dun, it the possible is Owen, and 2000; time(Taylor Himalaya andMitchell, atthis flux Sharma from the sediment high forel the in floods of high-intensity occurrence 2009; Ray and Srivastava, 2010; Roy et al., 2012). This article is protected by copyright. All rights reserved. exte the wide from this, from and infer We 2012). to as supply al. highinterpreted of due being rates (RoyRoy been et etal., again 2012),and has recorded between(Srivastava15.1 to11.7ka al., Giblinget al., Tandon 2003; et 2005; et al., 2006; al.,sediment transport (Pratt et 2002).In Ga the hillslope and failures slope extensive with along 2010) Srivastava, and (Ray supply hinterland of rates high by driven perhaps unit, fan distal the of deposition widespread for evidence is there relatively limited sediment transport into foreland. early In post-glacial the the ka),period (16-11 may led to of low have riverLGM discharges supply and rates oflow some combination that possible cold from relatively resulting as interpreted been Ga the in deposition channel for evidence no found and (Goodbred, 2003), while others have interpreted have others while 2003), and (Goodbred, , arid LGM conditions (Goodbred, 2003), and it is it and 2003), (Goodbred, LGM conditions , arid LGM-age sediments are not found in the central central the arenotfoundin sediments LGM-age nga plains, major channel aggradation has been has aggradation channel plains,nga major nga valley between 25 and 15 ka. This hiatus has has hiatus This ka. 15 and 25 between valley nga nt of the distal fan unit, that the dun may have thatthedunmayhave unit, fan distal of the nt Sinha et al., 2007); indeed, Roy et al. (2012) al. (2012) al., indeed, et Roy et 2007); Sinha Several ofSeveral thesestudies have inferred the rt ofthe distal unit.fan inthe Aggradation

Accepted Article ka. 15-12 kaand 34-21 at aggradation downstream widespread with concert in spilled’, and ‘filled dun the that we infer supply, hinterland andincreasing discharge rising of combination some to due however, Later, supply. hinterland of rates low or discharges river low of combination partial, a acted as have may dun the periods coincide 16 ka) with periodslimited of downstre ka, 23- (~41-33 thedun within aggradation widespread of thetimes of Several bypassed. and filled is thedun when supply hinterland high of periods during also and fill, thedun of incision and capacity sediment contrast, In supply. sediment hinterland of independent somewhat is aggradation dun but underfilled, is dun the when and perhaps capacity transport low of periods during sequestered tobe appears Sediment plains. Ganga to the hinterland the from flux sediment in variations climate-driven modulate to act may thedun sum, In theforeland. to discharge sediment high allowing again period, this during certainly bypassed unit and was fan thedistal of by stages of deposition thelater filled been This article is protected by copyright. All rights reserved. Narayangarh, the upstream at entrance the to near Gandak the of discharge sediment suspended present-day ofthe Estimates 2001). 2000, Avouac, and (Lavé HFT the of strands above developed sediments Siwalik of ridges anticlinal behind impounded Dun is Chitwan Dun, the Dehra the in As 5). (Fig. south the to system theHFT north and the to Dun Thrust Main and theMBT of strands between developed has which 1), (Fig. Dun Chitwan the through flows Nepal) southern in River theNarayani toas referred (also River Gandak The rivers. la other several from observations with results our compare we question, this answer To front? Himalayan the along duns other to applicable model this is extent what To rivers. Yamuna and Ganga the in flux sediment to contribution its of magnitude and thetiming on constraints place to Dun help Dehra the from results Our GandakComparison River to the transient sediment trap, perhaps due to some tosome due perhaps trap, sediment transient rge Himalayan river systems, the Gandak and Kosi Kosi and Gandak the systems, river Himalayan rge Chitwan Dun, are105-110 Mt/yr (Lavé and Avouac, am deposition, and we infer that during these these during that we infer and deposition, am is exported duinrg periods of high transport transport high of periods duinrg exported is

Accepted Article morphology, deposit geometry, and cross-cutting relationships between units, we tentatively tentatively we units, between relationships cross-cutting and geometry, deposit morphology, surface of basis the On units. depositional youngest two the for ka <10 ka and of26-16 ages No absolute ages are available for the Chitwan Dun deposits,fill although Kimura(1995) suggested 5). (Fig. beds river modern the mabove 10-70 surfaces, near-planar and into, inset clearly are that deposits) Kirtipur younger extensive, more a (2) beds, modern river to from the ~180 m above 300 range that surfaces slightly convex-up to quasi-planar deposits) with and Belani Barakot (the remnants fan of set older an (1) comprise broadly units youngest two correlatio in uncertainty by complicated somewhat be correlated across catchment-fanmultiple While systems. interpretation assignments of his is could that units depositional main three identified (1995) Kimura 1999). 1995, (Kimura, Dehra Dun terraces (Fig. 5), which extensiveform low-gradient depositional surfaces similar tothose theof fill and fans interfingering of series a in deposited been has hangingwall, Dun Thrust Main the drain that basins smaller from and Rivers, Rapti Gandak and the from sediment Dun, theChitwan Within full. nearly is dun the in accommodation that indicating perhaps floor, dun the into incised substantially not is Dun and Chitwan the rive the present, At comparable. directly not be may and model, mixing on a based are (2008) etal. Singh by Mt/yr 450-510 of estimates discharge Dehra Dun, and the younger fan remnants (Bishannagar and Kirtipur deposits) with the Dehra Dun Dun Dehra with the deposits) Kirtipur and (Bishannagar remnants fan younger the and Dehra Dun, the in unit fan proximal the with deposits) Belani and (Barakot fan remnants the older correlate equivalentvolumetric to discharges of Mm ~30-70 are values These Mt/yr. 79 of discharge sediment suspended estimated a (1994) and Friend Sinha downstream thedun, of near total the end 110-184 of Mt/yr. sediment discharge Tribeni, At 2001; Garzanti etal., while2007), Lupker et usedal. (2012) cosmogenic radionuclides to estimate This article is protected by copyright. All rights reserved. r occupies a wide, low-gradient meander belt across across belt meander low-gradient wide, a r occupies onlap, the older remnants, and form widespread set of planar fan remnants (the Bishannagar and and Bishannagar (the remnants fan planar of set 3 n between different lithostratigraphic units, the the units, lithostratigraphic different between n /yr. Note that the much larger sediment /yr. themuch larger that Note

Accepted Article ka. or16-11 34-21 at Dun Dehra for the inferred conditions bypass the to analogous may and be 2008), etal., Singh (e.g., Gandak the of discharge sediment modern high the may explain day present the at nearly full be to appears dun thatthe observation The 2014a). al., et the dun(Sinha in sediment of trapping episodic by caused hiatuses depositional dueto perhaps units, both in discontinuous are fills channel Importantly, mud layers. by separated bodies sand m)(>40 channel fills setinto thick muds,comprises that unit and upper an thinner, laterally-stacked narrowthick but by characterized unit lower a fan: 100mthe of upper lithological withinthe units document to resistivity Sinhaetal.two (2014a) used limited1997). and data surveys borehole Downstreamof the HFT, the Gandak has built ahighly avulsive fan system in the foreland (Gupta, indicative. remain must estimates such so and unconstrained, remains Dun theChitwan in and incision stre We discharge. sediment suspended Gandak modern removed 2400 removedMm 2400 fan remnants has removed a volume of 6300 Mm of 6300 a volume removed has remnants fan older the of incision that we find then Dun, Dehra the in used we as volumes erosional and depths If we accept correlations the of Kimuraand (1995) apply same the techniques todetermine incision Dun fill. Chitwan the of dating and mapping careful more with betested must correlation This relationships. geometrical similar and have settings spatial similar occupy thedeposits that only settings, two these in similar are ages depositional the that imply course, of not, does This fan unit. distal This article is protected by copyright. All rights reserved. evacuation would imply a time-averaged sediment discharge of ~0.2 Mm of ~0.2 discharge sediment time-averaged a imply would evacuation co the with as ka, 10 around at began remnants 3 from the dun (Fig. 5). If we further assume that incisionof the younger fan rrelative deposits in the Dehra Dun, then this Dun, thenthis Dehra rrelative deposits in the 3 , while incision of the younger fan remnants has has remnants fan theyounger of incision , while ss, however, that the timing of deposition deposition of timing thatthe however, ss,

3 /yr, about 1% of the the of 1% about /yr, Accepted Article isolated channel bodies within the subsurface (Sinha al., et These 2014a). observations agree with more much and sizes grain overall finer with fan a built has yield, sediment suspended higher present-day (Sinha etal., and 2005) late Holocene (Lupker sediment et al., 2012) discharge and a comparable despite which, River, Gandak the with contrasts This thefan. of upstream storage sediment intermediate of thelack to due being as years), 24 (approx. River theKosi of timescale Sinha etal. interpreted (2014a) this depositional architecture, along with the short avulsion fan. proximal the in deposits gravel thick with m thick, 20-30 bodies, sand multi-story widespread 1982; Sinha etal., Subsurface 2014b). investigationof the top m ~100 by Sinha al. et reveals (2014a) (Chakraborty etal., 2010; Sinha etal., 2013), with evidence for rapid historical aggradation (Desai, Downstreamof the HFT, the Kosi Riverconstructed has alarge, highly avulsive fan system area). thedrainage twice from approximately derived (although Gandak the of those to comparable Parkash (1990), thesevalues equivalent are tovolumetric discharges of ~30-70 Mm and Gohain of estimate high the Mt/yr.from Apart 69-141 of discharge sediment total longer-term much valuehigher of 345Mt/yr. (2012) usedLupker etal. cosmogenic radionuclides to estimate a et al., 2005) to Mt/yr175 (Lave and Avouac, 2001), while Gohain and Parkash reported (1990) a Sinha 1994; Friend, and (Sinha respectively Baltara, and Barakhshetra at 43Mt/yr and from 95Mt/yr range Kosi ofthe discharge sediment suspended thepresent-day of km. Estimates 1 to ofup lengths) HFT hangingwall (Fig. with local6), relief km radius to (measured overa reflect typical1 hillslope the in rocks basin foreland Siwalik Lower and Middle weak of relatively composed is MBT and HFT the between sheet Thethrust 2001). Avouac, Laveand 1992; (Schelling, systems MBT and HFT the relati a and front mountain abrupt an in resulted has foreland the into propagation of lack the and 2001), Avouac, and (Lave front mountain the at system Late Quater 6). Fig. 1, (Fig. Nepal eastern in plain Ganga the into directly debouches River Kosi the Gandak, and Ganga, theYamuna, to contrast In Kosi River Comparison to the This article is protected by copyright. All rights reserved. nary deformation appears to be focused on the HFT HFT the on focused be to appears deformation nary vely short distance (as little as 5-8 km) between between km) 5-8 as little (as distance vely short

3 /yr, broadly /yr, broadly Accepted Article contrast, rivers without proximal storage are likely arelikely storage proximal without rivers contrast, In 7B). (Fig. theforeland into sediment of spilling and dun of the tofilling leading high, are capacity transport and supply hinterland both (2) or fill, dun the of incision in resulting high, is capacity transport (1) either when dun the evacuated from is Sediment 7A). (Fig. conditions underfilled to leading supply, hinterland low or high either and capacity low transport of periods dun during c transport in changes supply, sediment hinterland in changes through occur may This foreland. the to supply sediment the amplify and to modulate inference from the observations field is intermediate that dun sediment storage and release will act key Our 7). (Fig. dun of a absence, and presence, the both in foreland tothe supply sediment in variations temporal of model conceptual a in systems river all from results our summarise We model Conceptual foreland. the to discharge low sediment of periods during store sediment transient a as acting butalso values discharge high amplifying supply, sediment hinterland our interpretation from the Dehra Dun and Chitwan Dun that proximaldun storage can‘filter’ This article is protected by copyright. All rights reserved. rivers. these along stores sediment distal and proximal between thelinks of study careful and time scales, different over fluxes of sediment of importance therelative example. Unravelling depends on a range of factors (e.g., al., Sinha et systems river Himalayan major of the evolution and behaviour large-scale that recall to important (e.g., 1995;Mohrig 2000;Wickert etal., Bryant etal., 2014b).al., 2013;Sinhaet Itisal., et also is important tonote that avulsion frequency is subsequent avulsion, as modernthe in Kosi (Sinha, River 2009; Chakraborty al., 2010),et although it and aggradation bed to prone bemore also may duns without Rivers theforeland. in units channel leading 7C), (Fig. flux sediment temporally-variable dependent on a number of other variables as well well as variables other of anumber on dependent 2005), of which transient storage in a dun isbut one these factors will require enhanced understanding understanding enhanced require will factors these apacity, or both. Sediment is sequestered in the in the sequestered is Sediment both. or apacity, to be characterised by more a continuous, less perhaps to enhanced likelihood of ‘stacking’ of of ‘stacking’ of likelihood enhanced to perhaps

Accepted Article possible implications of episodic storage and release for spatial variations in specific sediment sediment specific in variations forspatial release and storage episodic of implications possible the explore to useful be would It Ganga Basin. the from data age and stratigraphic available using response fluvial downstream and supply sediment upstream between thelink inferred have We duns. Himalayan the bounding faults along uplift rock of pattern full of better assessment the needfor the to ourresultspoint 2013), structures associated (e.g.,the withHFT Wesnousky al.,et 1999;Kumar etal., 2006; Sapkota etal., on ofslip rates Holocene understand to effort beensome has there While faults. active by multiple bounded dun a of thepresence in lower be to likely is front mountain the to adjacent immediately su subsidence, foreland more spatially-distributed mountain atthe form to likely are depocentres local di front mountain the at uplift rock of distribution because Scherler etal., the but riversystems 2014), 2005; themajor of al., Sinhaet (e.g., hinterland and ofrates rock uplift. This templatecritical, is not just because helps it set erosionto the in rates understanding of theimportance highlights model This This article is protected by copyright. All rights reserved. the through thatdrain systems river major the of morphology thedownstream on source sediment this time-varying of theeffects understand to order in India, northwestern in basin piggyback a Dehra Dun, the from evacuation and storage sediment of magnitude timing and the investigate We Conclusions entire Ganga sediment routing system (e.g., Bloethe Korup,and 2013). large-scale our improve could help variations these of study systematic A more storage. upstream abundant with systems those than transfer the as such dun, a without systems river is whether question natural A rivers. Gandak and Ganga the in sediment bedload and suspended both times of characteristics. example,Granet (2007, For etal. used 2010) U-Th disequilibria estimate to transfer understanding of sediment movement the through of sediment understanding ctates whether or not pi not or whether ctates ch that the rate of accommodation generation generation accommodation rateof the that ch Kosi or Karnali, show evidence for more rapid more rapid evidence for show Karnali, or Kosi front. tectonicfront. Distributed activity implies also the tectonic ‘template’, or spatial distribution distribution or spatial ‘template’, tectonic the

ggyback basins or other other or basins ggyback Accepted Article evolution. and stratigraphy, morphology, river downstream determining specifically,which way the shortening in is distributed across different plays faults critical – a role in – front themountain at framework tectonic the that examples these from infer We bodies. channel multi-story stacked by characterised fan avulsive highly coarse-grained, a built has sediment upstrea of lack the and foreland, the into directly debouches River Kosi the contrast, In plains. Ganga the in fan mud-rich a of construction and front mountain theHimalayan of upstream sediment of and release storage toepisodic led has Gandak the dun along a of thepresence Nepal; central in systems Kosi river Gandak and of the features contrasting some explain to appears model This systems. river major tothe supply sediment in variations climate-induced amplify thus may dun The aggradation. downstream widespread of periods to correspond sediment, of dun evacuation and excavation subsequent and aggradation, dun of Later phases trap. sediment transient partial, a as may act thedun that indicating plains, hinterland the in aggradation upstream of periods with coincide to appear dun in the storage sediment of episodes two least at of stages early The on ~10 show that the dun highly fill is dynamic, changeswith major bothinvolumedepocentre and location combin the of 1.5% about from rivers, and Yamuna of the 1-2% thatare discharge palaeo-sediment of estimates yield incision, for available span time themaximum by divided when phases, incision these during released sediment of volumes The depocentre. the of shift abasinward and lobes, depositional active the of abandonment incision, fan-head by followed was phase progradation in at least stages the bylater deposition fill terrace along Ganga the and rivers.Yamuna Each accompanied dun, the into out built fans sediment phases, these of each During ka. and23-10 34-21, phase three least at for evidence shows dun The dun. This article is protected by copyright. All rights reserved. 4 yr scales. time modern suspended-sediment loads of the Ganga Ganga the of loads suspended-sediment modern m storage means that a more continuous supply of of supply continuous more a that means m storage and partial depositional hiatuses in hiatuses the Ganga depositional and partial ed catchment areas of th of catchment areas ed s of late Quaternary sedimentation, at ~41-33, at~41-33, sedimentation, Quaternary late of s

ese ese rivers. results Our Accepted Article CARRETIER, S., & LUCAZEAU, F. (2005) How does alluvial sedimentation at range fronts modify the modify fronts atrange sedimentation alluvial does How (2005) F. LUCAZEAU, & S., CARRETIER, ALLEN, DENSMORE,P.A., & SedimentL. A. (2000) flux from an uplifting block. fault basin River Ganges the in transport sediment and Erosion (1984) V. SUBRAMANIAN, N.,ABBAS, & References manuscript. the improve to helped reviewers, anonymous two and Attal by Mikael reviews constructive Geology assistance for with theOSL dating. Commen Himalayan of Institute theWadia at Suresh N. thank also We input. and perspectives their for Plains Ganga the in Dynamics River on Seminar International Society/DST Royal the of participants the and field, the in assistance and discussions useful for Pickering Jack and Dingle, Elizabeth Barnes, Jason thank We theproject. throughout ideas and guidance helpful very provided has Gupta Sanjeev This work was supported by grant a from the UK-India Education and Research Initiative (SA-07-06F). Acknowledgements This article is protected by copyright. All rights reserved. of rate and frequency avulsion of study Experimental (1995) C. PAOLA, & P., FALK, M., BRYANT, BLUM, M.D., & TÖRNQVIST, T.E. (2000) Fluvial responsesclimate to and sea-levelchange: areview BLOETHE, &KORUP, Millennial J. (2013) O. lag the Himalayanin times sedimentrouting system. Interplay (2011) S.K. TANDON, & V., JAIN, R., SINHA, M., MUKUL, A.L., DENSMORE, J.B., BARNES, erosional dynamics of mountain catchments? deposition. forward. look and (India). Earth and Planetary Science Letters Science Planetary and Earth Surface, Earth – Research Geophysical of Journal topography. fold frontal Himalayan of development the in level base and faulting between 12, 367-380. J. Hydrology Geology Sedimentology , 69, 173-182. , 23, 365-368. , 47, 2-48. , 382, 38-46. Basin Research ts by journal editor Peter van der Beek, and and derBeek, Peter van ts by journal editor 116, F03012, 116, doi:10.1029/2010JF001841.

, 17, 341-361. Basin Research Basin , Accepted Article DUEHNFORTH, M.,DENSMORE,ALLEN, Controls P.A. A.L., (2008) S., sediment on IVY-OCHS, & DUTTA, S., N.& SURESH, KUMAR, R. (2012). Climaticallycontrolled QuaternaryLate terrace staircase K.D., RIDGWAY, COLE, M.B., GRAY, P.G., DECELLES, the and development basin foreland Tertiary tomiddle Early (2003) B.K. HORTON, & P.G., DECELLES, DECELLES,P.G.,GILES, & K.A. (1996) Foreland basin systems. DAVIES, & KORUP, T., O.(2007)Persistent alluvial fanhead trenching resulting from infrequentlarge, CLIFT, P.Controls (2006) on the erosion of Cenozoic and fluxAsia ofthe clastic sediment to the CLARKE, L., QUINE, NICHOLAS, T.A., A.P. (2010)An experimental& investigation of autogenic CHAKRAPANI,G.J., & SAINI, R. (2009)Temporal K. and spatial variationswaterdischarge in and geo- records, Historical megafan: Kosi 2010. S., BASU, & P., GHOSH, R., KAR, T., CHAKRABORTY, sediment high-frequency are plausible How (2003) J. DRIESSCHE, DEN VAN & S., CASTELLTORT, This article is protected by copyright. All rights reserved. Sciences India. Himalaya, in Rivers Bhagirathi and Alaknanda the in load sediment River. Kosi the of avulsion recent the and morphology record? stratigraphic the cycles in supply-driven California. Nevada, Sierra theeastern in catchments unmodified and modified glacially from evacuation sediment inputs. inputs. sediment Palaeoclimatology, Palaeoecology Palaeoclimatology, bestofthe thefold-in Himalaya. andthrust Sub development Montana. and Wyoming (Palaeocene), Conglomerate Beartooth architecture, alluvial-fan synorogenic on Controls (1991) P. 77. Bolivia. in shortening crustal of Andean history ocean. ocean. evolution. fan alluvial during behavior Earth and Planetary Science Letters Science Planetary and Earth , 35, 545-553. Earth Surface Processes and Landforms Earth Surface Processes and Landforms and Processes Surface Earth , 356–357, Geomorphology Sedimentology , 241, 571-580 16-26. R.B., PIVNIK, D.A., PEQUERA,N. &SRIVASTAVA, Geological Society of America Bulletin Sedimentary Geology Sedimentary , 33, 1602-1613. , 33, , 38, 567-590. , Quaternary International, Quaternary , 115, 278-285. Basin Research Basin

, 32, 725-742. , 157, 3-13. , 8, 105-123. Journal of Asian Earth Palaeogeography, Palaeogeography, 227, 143–160. , 58– 115, Accepted Article GOHAIN,PARKASH, K., & (1990) Morphology B. Kosi of the Megafan. In: a towards sequences: alluvial valleys and Alluvial (2011) R. SINHA, & C.R., FIELDING, M.R., GIBLING, sequences alluvial Discontinuity-bounded (2005) JAIN, & R. M. SINHA, S.K., TANDON, M.R. GIBLING, GARZANTI, E., VEZZOLI,G., ANDO, S., LAVE, J., ATTAL,M., FRANCE-LANORD, C., & DECELLES, P. GALY, V., FRANCOIS, L., FRANCE-LANORD, C.,FAURE, P., KUDRASS, H., PALHOL, &SINGH, F., S.K. GALY, FRANCE-LANORD, A., & Higher (2001) C. This article is protected by copyright. All rights reserved. GUPTA, Himalayan S.(1997) drainage patterns and origin the of fluvial megafansGanges inthe U-series (2010) E. BLAES, & C., FRANCE-LANORD, A., DOSSETO, P., STILLE, F., CHABAUX, M., GRANET, of Time-scales (2007) E. PELT, & P., STILLE, C., FRANCE-LANORD, F., CHABAUX, M., GRANET, GOODBRED, (2003) S. ResponseGanges of the dispersal systemclimatechange: to asource-to-sink Approach geomorphic assessment, assessment, geomorphic strength. aggrada India: plains, Gangetic southern the of Letters Science Planetary Himalaya). Nepal River, (Marsyandi erosion and provenance sand Quantifying (2007) Reviews Science Maximum. Glacial theLast since basin the Himalayan in decline plants C4 (2008) constraints on riverine fluxes. foreland basin. basin. foreland theHimalayan of rivers. case the plains: alluvial in time transfer sediment for implication and sediments river suspended in disequilibria Himalayan rivers. the from clues nuclides: U-series from processes weathering and transfer sedimentary viewlast interstade. since the (Ed. by (Ed. A.H.Rackchoki and M. Church),pp. 151-178. John Wiley and Sons Ltd. Journal of Sedimentary Research Sedimentary of Journal Geology , 27,1396-1409. Earth and Planetary Science Letters , 25,11–14, , 258, 500-515. SEPM Special Publication Special SEPM Geology Sedimentary Geology Sedimentary , 29, 23–26. Geochimica et Cosmochimica Acta Cosmochimica et Geochimica erosion the rates Himalaya:in geochemical , 75, 373-389., tion and degradation in response to monsoonal to monsoonal response in degradation and tion , 97, 423–447. , 162, 83-104. , 261, 389-406.

Alluvial Fans: A Field Field A Fans: Alluvial , 2851-2865. 74, Quaternary Quaternary Earth and and Earth Accepted Article KUMAR, S., WESNOUSKY, S.G., ROCKWELL, T.K., BRIGGS, R.W., THAKUR, V.C., & Nepal. basins, piggyback sub-Himalayan of evolution Diachronous (1999) K. KIMURA, JUYAL, N., PANT, R.K., BASAVAIAH, N., BHUSHAN, R., JAIN, M. SAINI, N.K., YADAVA, M.G., & SINGHVI, SINGHVI, & M.G., YADAVA, N.K., SAINI, M. JAIN, R., BHUSHAN, N., BASAVAIAH, R.K., PANT, N., JUYAL, JHA, P.K., SUBRAMANIAN,V., & SITASAWAD, R. Chemical(1988) and sediment transfer mass in the HILLEY,G.E.,M.R. &STRECKER, Processes (2005) ofoscillatory basin filling and excavation a in This article is protected by copyright. All rights reserved. KIMURA, K. (1995) Terraced debris and alluvium as indicators of the Quaternary structural structural Quaternary the of indicators as alluvium and debris Terraced (1995) K. KIMURA, KIM, W., PAOLA, C., SWENSON, J.B., &VOLLER, V.R. (2006) Shoreline response toautogenic fan deltas. calm of pulse The (2008) D.J. JEROLMACK, & W., KIM, KIM, W., &MUTO, (2007) AutogenicT. response of alluvial-bedrock transition baseto level variation: along the Indian Himalaya. Indian the along earthquakes rupture surface great of evidence Paleoseismic (2006) R. JAYANGONDAPERUMAL, 8, 99-113. doi:10.1029/2004JB003309. sediment of the Higher Central Himalaya, Uttarakhand, India. India. Uttarakhand, Himalaya, Central Higher of the sediment A.K. Reconstruction(2009) Last of Glacial Holoceneearly to monsoon variability from lake relict system. Ganges the of atributary river- Yamuna America Bulletin Argentina. NW Basin, Toro del Quebrada orogen: active tectonically processes of sediment storage and release in the fluvial thefluvial system. releasein processes and sediment of storage doi:10.1029/2006JF000561. theory. and experiment 34, 437-449. Tohoku University, 7 University, Tohoku Nepal. central Dun, Chitwan thenorthwestern of development Surface Earth – , 111, F04013, doi:10.1029/2006JF000470. , 117, 887-901. th Series (Geography) Series Journal of Geophysical Research – Earth Surface Earth – Research Geophysical of Journal Journal of Geophysical Research –Solid Earth , 45,103-120. Journal of Hydrology

Journal of Geology of Journal Journal of Asian Earth Sciences Earth Asian of Journal The Science Reports of the Journal of Geophysical Research Research Geophysical of Journal Geological Society of of Society Geological , 104, 237-246. , 112, F03S14, , 111, B03304,, 111, , 116, 315-330. The Island Arc Island The , , Accepted Article LETURMY, P., MUGNIER, J.L., VINOUR,P., BABY, P., COLLETTA, B., &CHABRON,E. (2000) Piggyback central of Himalayas the across uplift tectonic and incision Fluvial (2001) J.P. AVOUAC, & J., LAVÉ, LAVÉ, J., & J.P.AVOUAC, (2000)Active folding of fluvial terraces across the Siwaliks Hills, Himalayas LANE, S.N., RICHARDS, & K.S. (1997) Linking riverchannel form and process: time, space, and LANCASTER, CASEBEER,S.T., N.E. & (2007) storageSediment and evacuationheadwater in valleys at This article is protected by copyright. All rights reserved. & L. HUSSON, G., VIDAL, E., CHALARON, P., HUYGHE, G., MASCLE, P., LETURMY, J.L., MUGNIER, MOHRIG, D., HELLER, PAOLA,P.L., LYONS, C., & W.J. (2000) Interpreting avulsion process from MEADE, R.H. Sources,(1982) sinks and storage of river sediment inthe Atlantic drainage of the MALMON, D.V., RENEAU,DUNNE, S.L., T., KATZMAN, D. DRAKOS, & P.G. (2005) Influence of LUPKER, M., FRANCE-LANORD, C., GALY, V., LAVÉ, J., GAILLARDET, J., GAJUREL, A.P., GUILMETTE, C., C., GUILMETTE, A.P., GAJUREL, J., GAILLARDET, J., LAVÉ, V., GALY, C., FRANCE-LANORD, M., LUPKER, (Bolivia). Zone theSubandean of case The transfer: mass superficial and tectonic between interactions of function a as levels detachment two with belt thrust thin-skinned a above development basin Nepal. of central Nepal. causality revisited. processes. fluvial and debris-flow between transition the doi:10.1130/0016-7606(2000)112<1787:IAPFAA>2.0.CO;2. Colorado). (western Formation Wasatch and Spain) (northern system Guadalope-Matarranya sequences; alluvial ancient States. United Research deli downstream on storage sediment 432. weathering of Himalayan sediments (Ganga basin). basin). (Ganga sediments Himalayan of weathering mountain over floodplain Predominant (2012) R. SINHA, & S.K., SINGH, M., RAHMAN, Journal of Geophysical Research – Solid Earth , 41, W05008, doi:10.1029/2004WR003288. Tectonophysics, Tectonophysics, Journal of Geology of Journal JournalGeophysical of Research – Solid Earth Earth Surface Processes and Landforms and Processes Surface Earth 320, 45-67. Geological Society America of Bulletin , 90, 235-252. very of contaminated sediment. contaminated very of , 106, 26561-26591. Geochemica Cosmochemica Acta Cosmochemica Geochemica

Geology , 22,249-260. , 105, 5735-5770. , 35, 1027-1030. , 35, , 112, 1787-1803,, 112, Water Resources , 84, 410- Accepted Article POWELL, E. J., W. KIM, & T. MUTO (2012) Varying discharge controls on timescales of autogenic ofautogenic timescales on controls discharge Varying (2012) MUTO T. & W.KIM, J., E. POWELL, 231-241. Piedmont. Carolina North PHILLIPS, Fluvial sedimentbudgetsinthe J.D. (1991) PEPIN, E., CARRETIER, S., & HERAIL, G. (2010) Erosion dynamics modelling in a coupled catchment- coupled a in modelling dynamics Erosion (2010) G. HERAIL, & S., CARRETIER, E., PEPIN, PAOLA, Quantitative (2000) C. models of sedimentarybasin filling. PANDEY, A.K.,PANDEY, P.,SINGH, G.D., JUYAL, & N. (2014) Climate footprints Late in the OVERPECK, J., ANDERSON, D., TRUMBORE, S., & PRELL, W. (1996) The southwest Indian monsoon monsoon Indian southwest The (1996) W. PRELL, & S., D., TRUMBORE, ANDERSON, J., OVERPECK, ORI, G.G., &FRIEND, Sedimentary P.F. (1984) basins formed and carried piggybackon active thrust NOSSIN, J.J. (1971) Outline of the geomorphology of the Doon valley, northern U.P., India. India. U.P., northern valley, Doon the of geomorphology the of Outline (1971) J.J. NOSSIN, This article is protected by copyright. All rights reserved. NAKATA, T. (1989) Active faults of the Himalaya of India and Nepal. In: In: Nepal. and India of Himalaya ofthe faults Active (1989) T. NAKATA, NAKATA T.(1972) Geomorphiccrustal history and movements of foothillsthe the Himalayas. of MUKHOPADHYAY, D.MISHRA, K., & The P.(2004) Main Frontal Thrust (MFT), northwestern MUGNIER, J.L.,LETURMY, P., HUYGHE, P., &CHALARON, E. (1999b) Siwaliks The of western Nepal II: fan system with constant external forcing. external constant forcing. with fan system 253. India. Himalaya, NW Valley, Dun of landforms Quaternary-Holocene sheets. over the last 18000 years. lastover 18000 the Geomorphology N.F Himalayas University, Tohoku Reports, Science Journal of the Geological Society of India of Society Geological the of Journal Himalayas: Thrust trajectory and hanging wall fold geometry from balancedcross sections. wedge. thrust the of Mechanics Asian Earth Sciences kinematics. and Geometry I. Nepal: western of Siwaliks The (1999a). B. DELCAILLAU, Geology (Ed. by L. (Ed. L. by L. MalinconicoLillie), J. and R. , 475-478.12, ., 12,18-50. , 629-642.17, Climate Dynamics, Journal of Asian Earth Sciences 22,39-177. , 64, 739-746. 739-746. , 64, Geomorphology 12, 213–225. 12, Spec. Pap. Geol. Soc. Am Soc. Geol. Pap. Spec.

, 122, 78-90. Sedimentology , 17, 643-657. Tectonics of the Western Western of the Tectonics Current Science Current Geomorphology, Geomorphology, ., 232,., pp. 243-264. , 47, 121-178. , , 106, 245- Journal of of Journal Zeitschrift 4, Accepted Article SAPKOTA, S.N., BOLLINGER, L., KLINGER, TAPPONNIER, Y., GAUDEMER,P., Y.,&TIWARI, D. (2012) datin On (1997), V. RAIVERMAN, RAHAMAN, W., SINGH, SINHA,S.K., TANDON, R.,S.K. & (2009)Climate controlonerosion PRELL, W.L., &KUTZBACH,J.E. Monsoon (1987) variability overthe 150,000 past years. This article is protected by copyright. All rights reserved. ROY, N.G., SINHA, GIBLING, R., & M.R.Aggradation, (2012) incision, and interfluve flooding in the REITZ, M.D., JEROLMACK, & D.J. (2012) Experimental alluvial fan evolution: Channel dynamics, slope RAY, Y.,&SRIVASTAVA, P. (2010)Widespread aggradation inthe mountainouscatchment of the RAIVERMAN, V., SRIVASTAVA,PRASAD, A.K., & D.N. On foothill (1993) the thrust of the PRATT, BURBANK, B., D.W., HEIMSATH,(2002) OJHA, A., Impulsive & T. alluviation during early POWERS, P.M.,LILLIE, & YEATS, R.J.,R.S. (1998) Structure and shortening ofKangra the and Dehra Geophysical Research – Solid Earth, Solid – Research Geophysical Holocene strengthened monsoons, central Nepal Himalaya. Himalaya. Nepal central monsoons, strengthened Holocene Geoscience 1255. and 1934 in earthquakes thegreatHimalayan of ruptures surface Primary ka. ~100 past the during theHimalaya over distribution Palaeogeography, Palaeoclimatology, Palaeoecology Palaeoclimatology, Palaeogeography, Ganga Valley over the past 100,000 years: testing the influenceof monsoonal precipitation. doi:10.1029/2011JF002261. growth. shoreline and controls, relationships. hinterland-foreland to implications and timescales River System: Alaknanda-Ganga Himalaya. Northwestern India. Sub-Himalaya, Dun reentrants, Surface Earth – Research Geophysical Experiments. Tank Environments: fluvio-deltaic in processes release and storage , 6, 71-76. Quaternary Science Reviews J. Himalayan Geology Himalayan J. g of the Himalayan Thrusts. g of theHimalayan Thrusts. Journal of Geophysical Research – Earth Surface Earth – Research Geophysical of Journal 92, 8411-8425. 92, , 117, F02011, doi:10.1029/2011JF002097. F02011,, 117, Geological Society of America Bulletin America of Society Geological , 29, 2238-2260. , 4, 237-256. , 356-357, 38-53. Himalayan Geology Himalayan Geology

Geology , 37,559-562. 30, 911-914. , 1010-1027. 110, , 18, 63-79. , 117, F02021, F02021, , 117, Nature Nature Journal of Journal Journal of Journal Accepted Article SINHA, R., BHATTACHARJEE,P., SANGODE, S.J., GIBLING, M.R., TANDON, S.K., JAIN, M.,GODFREY, & SINHA, R., JAIN, V.,PRASAD GHOSH,G.,BABU, & Geomorphic S. (2005) characterization and diversity SINHA, va Climate-induced SARKAR, S.(2009) & R., SINHA, R., & FRIEND, P.F. River (1994) systems and theirsediment flux, Indo-Gangetic plains, SINHA, R. SCHERLER, D., BOOKHAGEN, B., & STRECKER, M.R. (2014) Tectonic control on on control Tectonic (2014) M.R. STRECKER, & B., BOOKHAGEN, D., SCHERLER, SINGH, S.K., RAI, S.K., & KRISHNASWAMI, and (2008)Sr S. Nd isotopes inriver sediments from the SINGH,PARKASH, A.K., MOHINDRA, B., THOMAS, A., J.V., &SINGHVI, Quaternary(2001) A.K. alluvial SIMPSON, G.Influence (2010) mechanicalof the behaviour of brittle-ductile fold-thrust belts on the SHARMA, Quaternary L.A. (1996) M.C., OWEN, & glacial history Garhwal of the Himalaya, India. SCHELLING, D. (1992) The tectonostratigraphy tectonostratigraphy The (1992) D. SCHELLING, This article is protected by copyright. All rights reserved. and magnetic signatures. signatures. magnetic and the Valley sedimentsin D. andinterfluve (2007) of the fluvial systems of the Gangetic Plains. India. plains, Ganga the in successions fluvio-deltaic and India. Bihar, Northern 113, F03006, doi:10.1029/2007JF000909. doi:10.1029/2013JF002955. India. Himalaya, Garhwal in the rates Ganga Basin: sediment provenance and spatial variability in physical erosion. erosion. physical in variability spatial and provenance sediment Basin: Ganga palaeoclimatic implications. and tectonic Himalaya: NW Basin, Piggyback Valley Dehradun the in sedimentation fan developmentforeland of basins. Reviews Science Quaternary Tectonics

(2009) , 11, 925-943.

The The Great avulsionof on Kosi 18 August 2008. Sedimentology Sedimentary Geology Sedimentary , 335-365. 15, Basin Research Basin Basin Research Basin , 41,825-845. Journal of Geophysical Research – Earth Surface Earth – Research Geophysical of Journal and structure of the eastern Nepal Himalaya. Himalaya. Nepal theeastern of structure and , 13, 449-471. Geomorphology riability in the Late Pleistocene-Holocene fluvial fluvial Late Pleistocene-Holocene riability the in ,386-411. 201, , 22, 139-156. southern Ganga plains, I plains, Ganga southern

Geomorphology Current Science Current , 70, 207-225. , 70, ndia: exploring facies facies exploring ndia: , 113, 173-188. 10 , 97, 429-433 Be-derived erosion erosion Be-derived J. Geophys. Res Geophys. J. , 119, . ., Accepted Article SINHA, R., AHMAD,GAURAV, J., &MORIN, K., G. Shallow (2014a) subsurface stratigraphy and alluvial TANDON, S.K., GIBLING, M.R., SINHA, R., SINGH, V., GHAZANFARI, P., DASGUPTA, A., JAIN, A., DASGUPTA, P., GHAZANFARI, V., SINGH, R., SINHA, M.R., GIBLING, S.K., TANDON, SRIVASTAVA, P., TRIPATHI, J.K., ISLAM, R.,JAISWAL, & M.K. (2008) Fashion and phases of late SRIVASTAVA, P., SINGH, I.B., SHARMA, M., &SINGHVI, A.K. Luminescence (2003) chronometry and SINHA, SURESH,S., N.,DUTTA, KUMAR, R., S.&ARORA, Sedimentologic(2010) B.R. and geomorphic planform and threshold Avulsion (2014b) M. AND MUKUL, V., JAIN, K., SRIPRIYANKA, R., SINHA, SINHA, R., GAURAV, K., CHANDRA, S., & TANDON, S.K. (2013) Exploring the channel SINHA, GAURAV, connectivitychannel &TANDON,K., S.K.(2013)ExploringCHANDRA, the S., R., This article is protected by copyright. All rights reserved. THAKUR, (2013) Active V.C. tectonicsHimalayan of Frontal system.Fault their and orogeny Himalayan-Tibetan the of Active structures (2009) A. YIN, & M., TAYLOR, north- range, theZanskar of history glacial Quaternary The (2000) A.W. MITCHELL, & P.J., TAYLOR, Palaeoclimatology, Palaeoecology, India. Plain, Ganga the of history geomorphic Quaternary Late Sedimentary Geology Sedimentary India. basin, foreland Himalayan the in megafans Gandak and Kosi the of architecture Quaternary Research Quaternary India. Himalaya, western River Valley, Alaknanda the in incision and aggradation Pleistocene International exit. Ganga the along terracedeposits and fan alluvial Quaternary onthe studies Nepal. and (India) Bihar north in River Kosi of the dynamics JAIN, assessment. assessment. risk flood to application India: River, Kosi the of belt avulsion 2008 theAugust of structure Geosphere volcanism. Cenozoic and field, strain contemporary distribution, earthquake to relationships Himalaya. Indian west Incised Valleys inTime Spaceand

V. (2006) Alluvial valleys of the Gangetic Plains, India:causes and timingof incision. In: , 199-214. 5, Geology , 227, 87-103 , 41,1099-1102. , 70, 68-80. , 133-149. 301, Quaternary International Quaternary , SEPM SpecialPublication 197, 15-41. , 65, 81-99. 81-99. , 65,

, 85, 15-35. Geomorphology Palaeogeography, Palaeogeography, International Journal of of Journal International , 157-170. 216, Quaternary Quaternary

M., & Accepted Article This article is protected by copyright. All rights reserved. WICKERT, A.D., MARTIN, J.M., TAL, M., KIM, W., SHEETS, B., & PAOLA, C. (2013) River channel lateral lateral channel River (2013) C. PAOLA, & B., SHEETS, W., KIM, M., TAL, J.M., MARTIN, A.D., WICKERT, along convergence and Uplift (1999) V.C. THAKUR, & R., MOHINDRA, S., KUMAR, S.G., WESNOUSKY, catchment. Ganga-Brahmaputra WASSON, A the R.J. sedimentbudgetfor (2003) delivery problem. sediment The (1983) D.E. WALLING, VANCE, D.,BICKLE, M., IVY-OCHS, KUBIK, S., & P.W. (2003)Erosion and exhumation inthe Himalaya Dun of evolution Quaternary–Holocene Late (2007) N. SURESH, & A.K., PANDEY, V.C., THAKUR, fault in Dun of evolution Latetectonic Quaternary (2004) A.K. PANDEY, V.C., & THAKUR, YEATS, R.S., NAKATA, T., FARAH, A., FORT, M., MIRZA, M.A., PANDEY, M.R., & STEIN, R.S. (1992) The The (1992) R.S. STEIN, & M.R., PANDEY, M.A., MIRZA, M., FORT, A., FARAH, T., NAKATA, R.S., YEATS, YEATS, R.S., &LILLIE, R.J. Contemporary (1991) tect mobility:controls. metrics, timescales, and of thrust India. Frontal Himalayan the 1041-1047. 206, 273-288. sediments. river of inventories isotope cosmogenic from Earth Sci., India. NW Sub-Himalaya, Garhwal the of zone Fault Frontal theHimalayan and structure Sub-Himalaya. Garhwal system, fold bend/propagated Earth Science (Geol. Rundsch.) Himalayan frontal fault system. system. fault frontal Himalayan earthquake. Kangra 1905 the and thrusts blind 10.1029/2012JF002386. 118, 29,305-319. , 102, 1791-1810. Annales Tectonicae, Spec. Issue, Suppl. to Vol. VI Vol. to Suppl. Issue, Spec. Tectonicae, Annales Tectonics Journal of Geophysical Research – Earth Surface Earth – Research Geophysical of Journal onics of the Himalayan frontal system: frontal Himalayan fault folds, of onicsthe J. Structural Geol Structural J. , 18, 967-976. Journal of Hydrology of Journal Current Science

Earth and Planetary Science Letters, Science Planetary and Earth ., 13, 215-225. 13, ., , 87,1567-1576. , 65, 209-237. Current Science Current , 85-98. J. Asian Asian J. , 84, , 84, ,

Accepted Article This article is protected by copyright. All rights reserved. overlie Middle Siwalik rocks in the fault hangingwall; in turn, both of these units are unconformably are unconformably units these of both turn, in hangingwall; fault the in rocks Siwalik Middle overlie of Santaugarh the Fig. fault. 2for See locations.Deposits A, of the isolatedhills unit unconformably thehangingwall in Nadi, oftheKoti headwaters the near units depositional between Relationships 3. 3. Fig. in of photos viewpoints show fault Santaugarh of hangingwall in symbols Eye thicknesses. deposit fan minimum establish to used of boreholes locations mark dots Red 1. Table in given are surface below depths and ages, positions, sample (2001); etal. Singh by published ages mark circles grey while study, this in determined ages mark OSL circles White fault. Santaugarh SF, units. fan distal and fan, proximal hills, isolated the on focused is Our analysis fans. Dehradun and Donga the units on Depositional B, (2001). etal. Singh of fans Bhogpur and Dehradun, theDonga, mark BP and DD, DO, (2010). al. et Sinha from taken are River Ganga the along those while (2012), et al. Dutta from taken are River Yamuna the along those yellow; pale in shown are deposits terrace Holocene dun. the into flow that whil catchments, Yamuna and Ganga the show lines white Heavy system. Thrust Frontal Himalayan HFT, system; Thrust Boundary Main MBT, DEM. SRTM 2. A, Overview and geomorphic map of theDehra Dun area, overlain on ahillshade image of the here. discussed threeregions of the thelocations show boxes White (2009). Yin and andTaylor (1992) etal. Yeats from simplified Faults block. theupthrown mark faults on Barbs aredeveloped. duns major the where andHFT MBT the between region the highlight areas shaded light while systems, fault (HFT) Thrust Frontal Himalayan and (MBT) Thrust Boundary Main the of trace simplified show lines black Heavy and Nepal. 1. Location map showing major rivers (white) and duns along the Himalayan mountain front, India proximal fan unit is clearly visible, and can be traced continuously across the Santaugarh fault (out of of (out fault theSantaugarh across continuously traced be can and visible, clearly is unit fan proximal the surface of Thenear-planar west-southwest. the to is View unit. fan proximal bythe draped Figure Captions e white shaded areas indicate the Catchments Catchments the indicate areas shaded white e

Accepted Article 750 Mm 750 south. tothe tapers and footwall fault immediate the widespread more the into incision of depth the thedun of margin northern the along preserved are (1995) of Kimura units depositional (orange) Barakot-Belani and (yellow) Bishannagar-Kirtipur The foreland. the into flowing and Tribeni at HFT the crossing eventually dun, the across west-southwest simplifiedLave from and Avouac The (2001). Gandak Riverenters the dun at Narayangarh and flows systems to the north, and Himalayan the Frontal system Thrust (HFT) to the south. Faults are fault (MDT) Thrust Dun Main and (MBT) Thrust Boundary Main the of strands between formed onoverlain area, Chitwan5. Overview Dun of the Faults simplifiedFaults are Avouac 2001). Lave Kosi MBT and from (2000, The the strandsof flows across 6. Overview Kosiof exit. the River Background image 7ETM+ withLandsat is bandcombination 732. downstream. This is equivalent to the removal of 1900 Mm 1900 of removal to the is equivalent This downstream. to0 tapers and rivers, andAsan Suarna the particularly valleys, themajor of theheadwaters near indi Shading extent. depositional likely original the interpolate to used were that unit fan theproximal of extents mapped the show areas Orange fans. (DD) Dehradun (DO)and Donga the on fan unit proximal the into incision of depth Estimated 4. camera). the (toward westerly more trends valley new the and incised, and abandoned ofpaleovalley a incised into the isolated hills unit. Subsequently, the proximal unit was fan are separated from the underlying isolated hills unitby an angular uniformity that marks the margin direction thewallseast. recordedtheKotiof of Deposits unit istoproximal Nadi. in View the fan the transport sediment in changes spatial B, Nadi. theKoti of bank south the on left) tothe photo the This article is protected by copyright. All rights reserved. 3 from the Dehradun fan since abandonment of the proximal fan unit. unit. fan proximal of the abandonment since fan Dehradun the from cates the depth of incision, whichreaches m incision, depthof ~180 cates the Bishannagar-Kirtipur unit, which reaches ~70 m in m ~70 in reaches which unit, Bishannagar-Kirtipur a hillshade image of the SRTM DEM. The dun is is Thedun DEM. theSRTM of image ahillshade , in the footwall of the MDT. Shading indicates footwall MDT. the of , inthe 3 of sediment from the Donga fan and and fan Donga the from sediment of

Accepted Article discharge to the foreland Q foreland the to discharge sediment the that means material eroded this of Theaddition hangingwall. fault immediate the from supply sediment of rates high and deposits basin foreland easily-erodible recycled, of uplift rock rapid to leading front, thrust atthe concentrated is Deformation dun. a of absence the in evolution front C, Mountain ka. 10 since observed thedun in incision represents phase evolution during times of sediment accumu sediment of times during evolution front Mountain A, supply. and sediment climate in variations externally-imposed of theface in discharge to the foreland Q foreland the to discharge sediment and bebypassed can dun the point which at fills, thedun until trap sediment transient partial, a as acts thedun in deposition Fan rivers. hinterland large-scale and systems river local both from sediment for accommodation provides dun The structures. individual above and incision uplift rock of rates moderate to leading dun, the of margins downstream and upstream the on faults active between is distributed Deformation or both. thesystem, in capacity transport low hinterland, the from supply sediment increasing or low of combination tosome due arise could mismatch hangingwall Q evacuation from the dun, such that Q Mountai ka. B, 23-16 and 41-33 during observed incision and sediment evacuation from the dun is likely to cause an increase Q in increase an cause to likely is dun the from evacuation sediment and incision Fan both. or capacity, transport increasing or high hinterland, the from supply sediment of high dun. Insets show hypothetical evolution of sediment discharge into (Q into discharge sediment of evolution hypothetical show Insets dun. a (C)of absence B)and (A, thepresence in theforeland to supply sediment of model Conceptual 7. visible image. in the thefo fanin sediment broad a constructed have bytheKosi avulsions frequent and supply sediment High Chatra. at foreland the enters and and HFT This article is protected by copyright. All rights reserved. foreland, so that Q that so foreland, s in . The intermediate of storagelack . The toof leads toefficient the export sediment s out tracks Q tracks s out s out is greater than the sediment discharge delivered to the immediate immediate the to delivered discharge thesediment than is greater dun the in aggradation represents phase This (inset). rise may s in closely (inset). closely s in

s in ) and out of (Q of out ) and s in > Q s out s out (inset). This This (inset). . This s out ) the dun dun ) the Accepted Article a results analytical and samples OSL 1. Table This article is protected by copyright. All rights reserved.

LIS-TOP Sample (LD114 (LD103 (LD104 (LD104 (LD104 (LD114 Depth below surface of depositional unit, in m m in unit, depositional of surface below Depth code) FS1.1 FS3.1 FS2.2 FS2.1 IH/2 (Lab 8) 9) 2) 1) 0) 7) Isolated Proxim Proxim Depo. Distal Distal Distal al fan al fan unit hills hills fan fan fan Position 77° 57 30° 24 77° 51 30° 26 77° 56 30° 24 77° 56 30° 24 77° 57 30° 24 30 77 46.2” 18.9” 46.7” 29.7" 29.7" 35.5" 35.5" 41.9" 55.5" 20.4" 56.8" 56.8" 35.3" 35.3" 39.6" 39.6" 28.6" 28.6" ˚ ˚ 21 56 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′

Elev. 843 2.8 618 5 790 4 789 2.8 855 10 606 3 (m) (m) (m) pth pth De a

(ppm) 3.1±0. 3.3±0. 2.43± 2.23± 1.89± 4.56± 0.02 0.02 0.02 0.05 03 03 U (ppm) 18.4± 16±0. 15.3± 18.1± 16.4± 21.4± 0.18 0.15 0.18 0.16 0.21 Th 16 3.08± 2.46± 2.91± 3.02± 2.21± 2.65± K (%) K (%) 0.03 0.02 0.03 0.03 0.02 0.03

cont. Mois 1.36 13.5 3.44 1.27 18.1 14.3 (%) (%) t. 3 6 8 Weight 51.46± 207.20 65.71± 59.68± 80.72± 150.87 mean Equivalent dose ±5.47 ±14.2 ±14.2 1.87 3.62 3.96 6.82 ed De (Gy) 44.36± 208.6± 66.36± 45.26± 72.23± 128.9± Least 5.44 3.41 7.62 15.4 6.2 3.8 (Gy/k 3.58± 5.02± 3.10± 4.33± 4.99± 4.47± Dose 0.06 0.06 0.06 0.05 0.06 0.08 rate a)

Weigh mean 14.4± 41.3± 21.2± 13.8± 16.2± 33.8± ted 0.6 1.2 1.3 0.9 1.4 3.2 Age (ka) 12.4± 41.6± 21.4± 10.5± 14.5± 28.8± Least 1.5 1.3 1.3 0.8 1.5 3.5 Accepted Article

This article is protected by copyright. All rights reserved.

Accepted Article

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Accepted Article

This article is protected by copyright. All rights reserved.

Accepted Article

This article is protected by copyright. All rights reserved.

Accepted Article

This article is protected by copyright. All rights reserved.

Accepted Article

This article is protected by copyright. All rights reserved.

Accepted Article This article is protected by copyright. All rights reserved.