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To investigate the evolution of sediment provenances and transport processes in the central Bay of Bengal (BoB) since the Last Glacial Maximum, we present a comprehensive study on the grain size, clay minerals, rare earth elements, and accelerator mass spectrometry (AMS)14C analyses of the core BoB-24 sediments. Six AMS14C dates were obtained from planktonic foraminiferal Neogloboquedrina dutertrei (N. dutertrei) extracted from the core to reconstruct a reliable age model. The assemblage of clay minerals and the (La/Yb) UCC –δEu relationship indicated that the core contained a mixture of sediments from the Himalayas and Indian Peninsula. These results showed that the Himalayas were the main source of erosional materials during 25–6.5 ka BP, whereas those from the Indian Peninsula increased since the mid-Holocene. Between 25 ka BP and 12 ka BP, the sea level was relatively low, and a large amount of terrigenous detrital material were directly transported from the Himalayas and the Tibet Plateau to the study area by submarine canyons, forming a deposition center on the Bengal Fan. Between 12 ka BP and 6.5 ka BP, the sea level gradually rose and the Indian summer monsoon gradually strengthened, whereas the sedimentation rate and the amount of material transported from the Ganges–Brahmaputra River decreased greatly; the deposition center transferred from the Bengal Fan to the shelf of the BoB. Since 6.5 ka BP, the sea level has risen, reaching its present position. A high sea level and a strengthened East Indian Coastal Current resulted in an increase of material contribution from India, while the deposition center was on the shelf of the BoB. Overall, this study confirmed that both sea level fluctuations and variations of the Indian summer monsoon controlled the evolution of sediment provenances in the central BoB and transfer of the deposition center from the Bengal Fan to the continental shelf. This typical sedimentary pattern observed in the northeastern Indian Ocean improves our general understanding of past land–sea interactions. [Display omitted] [ABSTRACT FROM AUTHOR]

The interaction between climate and tectonics chiefly governs the erosion and sedimentary budget in the tectonically active Himalayan Mountain chain. In the present study, the relative contribution from the various litho-tectonic units of the Himalaya to the sedimentary budget of the Teesta River System (TRS) (a major tributary of the Brahmaputra system) has been deciphered using the Sr and Nd isotopic compositions (87Sr/86Sr, ε Nd) of bed sediments. The possible controlling factors for such observed sedimentary provenance have also been assessed. The discharge-weighted sediment transport amount has been translated into the quantification of the erosion rate in the basin. The 87Sr/86Sr and ε Nd values in the silicate fraction of bed sediments range from 0.74867 to 0.90529 and − 24.3 to −13.9, respectively. In the Teesta main channel, 87Sr/86Sr and ε Nd show large variability ranging from 0.74867 to 0.82288 and −21.8 to −13.9, respectively along its entire course. This large variability indicates changes in sediment sources i.e., Higher Himalaya and Lesser Himalaya. These data sets show that >60 % of TRS sediments are derived from the Lesser Himalaya, indicating a higher physical erosion over the catchments in the Lesser Himalaya. Our assessment suggests that the sedimentary budget of the Teesta Basin is chiefly governed by higher exhumation as well as the vertical uplift rate of the lesser Himalaya sector of the study area (due to the presence of Rangeet duplex) coupled with focused precipitations. Based on the sediment discharge method, we estimate the erosion rate in the Teesta basin to be 1.7 ± 0.5 mm/yr, which yields a total annual sediment flux of ~41.4 ± 12.4 Mtons. This estimate is comparable to other Himalayan River basins like the Ganga basin, however, lower than the erosion hotspots such as the Brahmaputra basin (Namche Barwa and eastern Syntaxis region) and Indus basin (western Syntaxis region). The obtained erosion rate of the Teesta basin seems to result from the active tectonics in the Sikkim sector of the Himalaya. • Teesta basin is a unique Himalayan River basin in terms of sedimentary provenance. • Erosion rate in the Teesta basin is estimated to be 1.7 ± 0.5 mm/yr. • Tectonics governs the first order control in sedimentary budget. [ABSTRACT FROM AUTHOR]

[Display omitted] • The influence of geology, soil, vegetation, and climate in fluvial carbon transport was assessed. • The annual DOC flux in rivers from Lesser Himalaya and Siwaliks (LHS) is higher than POC flux. • The concentration of lignin phenols is higher in suspended sediments compared to bedload sediments in rivers from LHS. • The lignin ratios indicate higher degradation in rivers from trans and Higher Himalayas than LHS. The Himalayan rivers yield the most significant flux of continental sediments into the ocean. Organic matter (OM) transported by these rivers provides a peek at the influence of diverse geological terrains, soil types, vegetation, and climate on carbon cycling within a narrow boundary. We analyzed suspended and bedload sediments from four Himalayan rivers to trace their sources, elucidate their fate during fluvial transport, and estimate the organic carbon (OC) flux. Hence, total OC (TOC), dissolved organic carbon (DOC), C:N ratios, and lignin phenols were measured. Consistent with the erosional intensity in the rivers, suspended sediment load input followed the order: Kaligandaki > Myagdikhola > Aadhikhola > Tinahukhola. C:N values in rivers from the Lesser Himalayas and Siwalik indicate sediments from mixed biogenic sources. In contrast, high TOC and C/N values in the trans-Himalaya rivers flowing through barren landscapes reflect the erosion of catchment sediments yielding petrogenic carbon. The suspended matter in rivers from the Lesser Himalayas and Siwalik has higher lignin phenol concentrations than the trans -Himalaya and Higher Himalaya rivers. The lignin phenol ratios indicate higher degradation in rivers from the trans and Higher Himalaya sections. This implies that only a small fraction of the terrestrial OM transported by these rivers deposits in the ocean sink. In contrast, rivers from the Lesser Himalayas and Siwaliks sequester a significant amount of OM bound to their bedload. As a result, these rivers transferred lower particulate OC (POC) but higher DOC than similar rivers worldwide. Rivers from Lesser Himalayas and Siwaliks transfer > 90 % of annual POC flux during monsoons. Finally, although Himalayan rivers transport less OC than other global rivers traversing densely vegetated landscapes, the sheer number of these rivers has significant implications on the fate and transport of total OC from catchments sediments. [ABSTRACT FROM AUTHOR]

Sediment in the flowing water are normally considered an obstacle for hydropower plants (HPPs). The operation and management of HPPs have been a significant challenge in sediment-laden rivers. In mountainous regions like the Himalayas, frequent rainfalls and glacial and sub-glacial hydrological activities during the monsoon season transport high sediment in streams. In these regions, HPPs face high erosion of the hydraulic turbines due to sediment abrasion, resulting in efficiency losses, frequent maintenance and shut down of power plants. The present study covers a comprehensive review of the recently developed techniques for the continuous measurement of suspended sediment concentration (SSC), and particle size distribution (PSD). Further, the study discusses the measurement strategies of suspended sediment properties, sediment erosion in the hydraulic turbine, its efficiency loss, and financial implications, focusing mainly on the Himalayas. Finally, the research gaps of the study are discussed, and its future scope is recommended. [ABSTRACT FROM AUTHOR]

It has been proposed that at short timescales of 102–105 yr, climatic variability can explain variations in sediment flux, but in orogens with pronounced climatic gradients rate changes caused by the oscillating efficiency in rainfall, runoff, and/or sediment transport and deposition are still not well-constrained. To explore landscape responses under variable climatic forcing, we evaluate time windows of prevailing sediment aggradation and related paleo-erosion rates from the southern flanks of the Dhauladhar Range in the western Himalaya. We compare past and present 10Be-derived erosion rates of well-dated Late Pleistocene fluvial landforms and modern river sediments and reconstruct the sediment aggradation and incision history based on new luminescence data. Our results document significant variations in erosion rates ranging from 0.1 to 3.4 mm/yr over the Late Pleistocene. We find that, during times of weak monsoon intensity, the moderately steep areas (hillslope angles of 27 ± 13°) erode at lower rates of 0.1–0.4 mm/yr compared to steeper (>40°) crestal regions of the Dhauladhar Range that erode at 0.8−1.3 mm/yr. In contrast, during several millennia of stronger monsoon intensity, both the moderately steep and high slope areas record higher erosion rates (>1-3.4 mm/yr). Lithological clast-count analysis shows that this increase of erosion is focused in the moderately steep areas, where Lesser Himalayan rocks are exposed. Our data thus highlight the highly non-linear response of climatic forcing on landscape evolution and suggest complex depositional processes and sedimentary signals in downstream areas. • Paleo-erosion rates in the Himalaya are modulated by climate forcing. • Erosion rates are higher during episodes of strong monsoon. • Topographic response to climate change is non-linear. • Rapid erosion during short-lived strong monsoon phases result in valley aggradation. [ABSTRACT FROM AUTHOR]