Quantifying episodic erosion and transient storage on the western margin of the Tibetan Plateau, upper Indus River

Abstract

Transient storage and erosion of valley fills, or sediment buffering, is a fundamental but poorly quantified process that may significantly bias fluvial sediment budgets and marine archives used for paleoclimatic and tectonic reconstructions. Prolific sediment buffering is now recognized to occur within the mountainous upper Indus River headwaters and is quantified here for the first time using optically stimulated luminescence dating, petrography, detrital zircon U-Pb geochronology, and morphometric analysis to define the timing, provenance, and volumes of prominent valley fills. This study finds that climatically modulated sediment buffering occurs over 103–104yr time scales and results in biases in sediment compositions and volumes. Increased sediment storage coincides with strong phases of summer monsoon and winter westerlies precipitation over the late Pleistocene (32–25 ka) and mid-Holocene (~8–6 ka), followed by incision and erosion with monsoon weakening. Glacial erosion and periglacial frost-cracking drive sediment production, and monsoonal precipitation mediates sediment evacuation, in contrast to the arid Transhimalaya and monsoonal frontal Himalaya. Plateau interior basins, although volumetrically large, lack transport capacity and are consequently isolated from the modern Indus River drainage. Marginal plateau catchments that both efficiently produce and evacuate sediment may regulate the overall compositions and volumes of exported sediment from the Himalayan rain shadow.

Millennial and centennial variations in zircon U‐Pb ages in the quaternary indus submarine canyon

“…There are multiple opportunities for sediment buffering in the Indus basin, especially because the flood plains are long (>1,000 km; Figures 1 and 2). Sediment storage in mountain terraces is also well documented (Blöthe et al, 2014;Jonell, Owen, Carter, Schwenniger, & Clift, 2017;Munack et al, 2016), and a high fraction of the Holocene sediment supply appears to be derived by reworking from these terraces , as well as large-scale incision of the flood plains . Furthermore, the Indus River recycles sediment from the neighbouring Thar Desert (Figure 2), which itself is supplied by aeolian sediment transport from the delta, especially during interglacial times when the summer monsoon winds are powerful (East, Clift, Carter, Alizai, & VanLaningham, 2015).…”

Buffered, Incomplete, and Shredded: The Challenges of Reading an Imperfect Stratigraphic Record

“…The buffering agent of a sediment flux signal in real systems is the composite redistribution of sediment mass across the Earth's surface, integrated over a range of spatiotemporal scales that include the net effects of intermittent sediment transport and temporary or permanent deposition of sediment within distinct landforms (e.g., river bars, floodplains, alluvial fans, and catchment valleys). It is the cumulative effect of these processes, particularly the temporary storage and subsequent remobilization (or reworking) of sediment that enables landscapes to buffer environmental signals such as changes in sediment supply (e.g., Jonell et al, ; Métivier, ). Revisiting the diffusion analogy, buffering of a heat input signal as it travels through a solid medium is dependent on the ability of the solid medium to transmit heat (conductivity) and the ability of a solid medium to store it (specific heat capacity).…”

“…T, time since last event. From Duller et al (2014). changes in sediment supply (e.g., Jonell et al, 2018;Métivier, 1999). Revisiting the diffusion analogy, buffering of a heat input signal as it travels through a solid medium is dependent on the ability of the solid medium to transmit heat (conductivity) and the ability of a solid medium to store it (specific heat capacity).…”

Evolution of arid landscape in India and likely impact of future climate change

“…The aggradation and incision processes divided the Indus valley into two segments: (1) from Nyoma to Leh, characterized by one level of channel filling, and (2) from Leh to Dah Hanu, characterized by one fill and one strath terrace. Apart from the above, an older filling event along the Indus at 200 ka and a younger filling at ~8-6 ka in the Zanskar rivers were also identified (Blöthe et al, 2014;Jonell et al, 2018). In the Karakoram, valley filling along the Tangste River took place during intensified monsoon at 48 ka and 30-21 ka, especially through glacio-fluvial, fluvial and lacustrine sedimentation (Phartiyal et al, 2015).…”

“…5 A and B). As a result, the valley floors started to gradually fill up along the Indus and its tributaries from both north and south, and subsequently channel incision also took place through those in-filled valleys (Burbank et al, 1996;Leland et al, 1998;Phartiyal et al, 2013;Blöthe et al, 2014;Jonell et al, 2018). At least three pulses of aggradation have been identified from sediment dating, centred at ~52 ka, ~28 ka, and 16 ka (Blöthe et al, 2014;.…”