Monsoon control over erosion patterns in the Western Himalaya: possible feed-back into the tectonic evolution (original) (raw)
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The Indus Delta is constructed of sediment eroded from the western Himalaya and since 20 ka has been subjected to strong variations in monsoon intensity. Provenance changes rapidly at 12-8 ka, although bulk and heavy mineral content remains relatively unchanged. Bulk sediment analyses shows more negative 1 Nd and higher 87 Sr/ 86 Sr values, peaking around 8 -9 ka. Apatite fission track ages and biotite Ar-Ar ages show younger grains ages at 8-9 ka compared to at the Last Glacial Maximum (LGM). At the same time d 13 C climbs from -23 to -20‰, suggestive of a shift from terrestrial to more marine organic carbon as Early Holocene sea level rose. U-Pb zircon ages suggest enhanced erosion of the Lesser Himalaya and a relative reduction in erosion from the Transhimalaya and Karakoram since the LGM. The shift in erosion to the south correlates with those regions now affected by the heaviest summer monsoon rains. The focused erosion along the southern edge of Tibet required by current tectonic models for the Greater Himalaya would be impossible to achieve without a strong summer monsoon. Our work supports the idea that although long-term monsoon strengthening is caused by uplift of the Tibetan Plateau, monsoon-driven erosion controls Himalayan tectonic evolution.
Holocene erosion of the Lesser Himalaya triggered by intensified summer monsoon
Geology, 2008
Climate is one of the principal controls setting rates of continental erosion. Here we present the results of a provenance analysis of Holocene sediments from the Indus delta in order to assess climatic controls on erosion over millennial time scales. Bulk sediment Nd isotope analysis reveals a number of changes during the late Pleistocene and early Holocene (at 14-20, 11-12 and 8-9 ka) away from erosion of the Karakoram and toward more sediment fl ux from the Himalaya. Radiometric Ar-Ar dating of muscovite and U-Pb dating of zircon sand grains indicate that the Lesser Himalaya eroded relatively more strongly than the Greater Himalaya as global climate warmed and the summer monsoon intensifi ed after 14 ka. Monsoon rains appear to be the primary force controlling erosion across the western Himalaya, at least over millennial time scales. This variation is preserved with no apparent lag in sediments from the delta, but not in the deep Arabian Sea, due to sediment buffering on the continental shelf.
Climate change and Late Pliocene acceleration of erosion in the Himalaya
Earth and Planetary Science Letters, 2006
Studies of active mountain ranges suggest that atmospheric and geodynamic processes may be strongly coupled through erosiona hypothesis that has led to a debate over the relative importance of climate and far-field tectonic forcing in influencing erosion. We addressed this debate by developing the detailed long-term erosional history of a transect in the central Annapurna Range of Nepal for comparison with the climate and tectonic forcing histories of the region. Patterns of apatite fission-track and muscovite 40 Ar/ 39 Ar apparent ages with elevation indicate a five-fold increase in apparent erosion rate between 2.5 and 0.9 Ma ago. The time frame for this change corresponds to that of global climate destabilization associated with the onset of Northern Hemisphere glaciation and an intensification of the Asian monsoon. There is no evidence for important changes in the farfield tectonics of the Himalayan-Tibetan orogenic system over that interval, suggesting a largely climatic driver for enhanced erosion at the Himalayan range front.
Geochemistry, Geophysics, Geosystems, 2017
Mineralogical and geochemical analyses conducted on cores located on the active channellevee system of the northern Bengal Fan are used to establish changes in the weathering pattern and the sediment transport of the Himalayan system, and evaluate the effect of Indian summer monsoon rainfall during the Holocene. Our data indicate that during the Holocene, sediments from the northern Bengal Fan originate mainly from the G-B river system without any significant changes in the relative contribution of these rivers. From 9.8 to around 6 ka, relatively low smectite/(illite1chlorite) ratios and relatively high K/Si* ratios indicate high physical denudation rates of the Himalayan highlands together with a rapid transfer of the detrital material to the Bengal Fan. The period between 9.2 and 7 ka is associated to lower values of K/ Si* and corresponds to the maximum of Indian monsoon rainfall which indicates a more important chemical weathering material that rapidly transits by the G-B river system without a long storage in the Indo-Gangetic plain. From 6.0 ka to present day, higher smectite/(illite1chlorite) ratio and lower K/Si* ratio document a gradual increase of sediments originated from the Indo-Gangetic plain, characterized by higher degree of chemical weathering. During the last 2.5 ka, the drastic increase in the smectite/(illite1chlorite) ratio could be associated to enhanced alteration of the plain soils due to anthropogenic activity. The comparison of mineralogical and geochemical data with previous reconstructions of the Indian monsoon dynamic indicates a rapid response of erosion and sediment transfer of the G-B river system to changes of monsoon rainfall intensity.
Link between climate and catchment erosion in the Himalaya during the late Quaternary
Chemical Geology, 2018
Few studies using geochemistry of sediments from plains and delta of the Himalayan river system have reported contrasting results on the shift in erosion of different lithotectonic units, across the strike of Himalayan orogen, in response to changes in the intensity of Indian summer monsoon (ISM) and glacial cover during the late Quaternary. Here we present records of the 143 Nd/ 144 Nd (ε Nd) and 87 Sr/ 86 Sr ratios and δ 13 C of sediment organic matter (δ 13 C SOM) in bulk sediment samples from two ~45 m long alluvial cores, collected from a paleo-Sutlej channel (in Sirhind, Punjab) at an upstream connection of a large river (Ghaggar-Hakra) with present-day Sutlej River in NW India. The isotopic variations are compared with the available proxy records that document changes in the ISM and Himalayan glacial extent. Significant covariation in down-core profiles of ε Nd (−14.1 to −22.2) and 87 Sr/ 86 Sr (0.72251–0.79456) reveals changing contributions of sediment derived from the Higher and Lesser Himalaya end-member sources in the catchment. Higher ε Nd (and lower 87 Sr/ 86 Sr) during early marine isotope stage (MIS) 1 and late MIS3 reflects increased contribution from the Higher Himalaya as a result of receding glacial cover as well as intense ISM that penetrates into the interior of the Higher Himalaya during warm periods. The δ 13 C SOM varies from −28.5‰ to −21.3‰ and shows a 5–7‰ increase from colder MIS2 to warmer early MIS1, implying an increase in C 4 plant abundance during the same period in response to intensification of the ISM in the post last glacial maximum period. These variations in sediment provenance and vegetation pattern thus highlight the pronounced influence of climate on distribution of erosion and vegetation types in the NW Himalaya.
Sr–Nd–Os evidence for a stable erosion regime in the Himalaya during the past 12 Myr
Earth and Planetary Science Letters, 2010
Modern erosion of the Himalaya, the world's largest mountain range, transfers huge dissolved and particulate loads to the ocean. It plays an important role in the long-term global carbon cycle, mostly through enhanced organic carbon burial in the Bengal Fan. To understand the role of past Himalayan erosion, the influence of changing climate and tectonic on erosion must be determined.
Quaternary Science Reviews, 2025
Over the millennial timescales, climate controls erosion rates and erosional fluxes in the Himalaya. However, the role of climate, particularly the strength of the Indian summer monsoon (ISM) and Himalayan glacial cover, on the distribution of erosion over the Himalaya is poorly understood. This study presents detrital radiogenic Sr-Nd isotope compositions in two ~48 m long cores representing sediment deposition in a paleo-Yamuna River channel, northwest India (Haryana), since marine isotope stage (MIS) 4. 87Sr/86Sr (0.7342–0.8066) and εNd (− 14.0 to − 19.7) values exhibit significant down-core variabilities and reveal varying proportions of sediments derived from the Higher and Lesser Himalayan sources. The down-core profiles show higher 87Sr/86Sr and lower εNd during MIS 4, mid-MIS 3, and last glacial maximum in MIS 2, which indicate reduced contribution of sediments from the Higher Himalaya during cold and arid periods typified by weaker ISM precipitation and increased glacial cover over the Himalaya. Further, the paleo-Yamuna record and a few available records on the Himalayan-derived sediments suggest that variations in local geology, topography, and location of the focused precipitation in a catchment could also influence erosion distribution.
Erosion is a key step in the destruction and recycling of the continental crust, yet its primary drivers continue to be debated. The relative balance between climatic and solid Earth forces in determining erosion patterns and rates, and in turn orogenic architecture, is unresolved. The monsoon-dominated frontal Himalaya is a classic example of how surface processes may drive focused denudation and potentially control structural evolution. We investigate whether there is a clear relationship between climate and erosion in the drier Himalayan rain shadow on the periphery of the Tibetan Plateau, where a coupled climate-erosion relationship is less clear. We present a new integrated data set combining bulk petrography, geomorphometric analysis, detrital U-Pb zircon geochronology, and bulk Nd and Sr isotope geochemistry from modern river sediments that provides constraints on spatial patterns of sediment production and transport in the Zanskar River. Zanskar River sands are dominated by Greater Himalayan detritus sourced from the glaciated Stod River catchment, which represents only 13% of the total basin area. Prevalent zircon peaks from Cambrian– Ordovician (440–500 Ma) and Mississippian– Permian (245–380 Ma) units indicate more abundant pre-Himalayan granitoids in the northwest Indian Himalaya than in the central and eastern Himalaya. Erosion from the widely exposed Tethyan Himalaya, however, appears modest. Spatial patterns of erosion do not correlate with highest channel steep
Climate control on erosion distribution over the Himalaya during the past ~100 ka
Geology, 2009
Sediment samples from a 50-m-long core representing ~100 ka of deposition, taken from the Ganga Plain on the campus of the Indian Institute of Technology, Kanpur, were analyzed for Sr and Nd isotope compositions. Both 87 Sr/ 86 Sr and ε Nd vary signifi cantly with depth in the core, 0.72701-0.76708 and-14.4 to-16.6, respectively, within the range for silicate rocks of the Higher and the Lesser Himalaya. The variations in the isotope compositions refl ect variations in the mixing proportion of sediments from the Higher and Lesser Himalaya, the two major sediment sources to the Ganga. The opposite trends in 87 Sr/ 86 Sr and ε Nd depth profi les further confi rm this hypothesis. The isotope profi les exhibit two major excursions, ca. 20 ka and ca. 70 ka ago, coinciding with periods of precipitation minima and larger glacial cover. These excursions are the result of a decrease in the proportion of sediment from the Higher Himalaya due to a decrease in monsoon precipitation and an increase in glacial cover that are in turn caused by lower solar insolation. This study highlights the signifi cant infl uence of climate on erosion in the Himalaya.
Regional Pliocene exhumation of the Lesser Himalaya in the Indus drainage
Solid Earth, 2019
New bulk sediment Sr and Nd isotopes, coupled with U-Pb dating of detrital zircon grains from sediment cored by International Ocean Discovery Program in the Arabian Sea, allow reconstruction of erosion in the Indus catchment since ca. 17 Ma. Increasing Nd values from 17 to 9.5 Ma imply relatively more erosion from the Karakoram/Kohistan, likely linked to slip on the Karakoram Fault and compression in the Southern and Eastern Karakoram. Long-term decreasing Nd values after 5.7 Ma correlate with increasing relative abundance of >300 Ma zircon grains that are most common in Himalayan bedrocks, precluding large-scale drainage capture as the cause of decreasing Nd values in the submarine fan. Although the initial increase in Lesser Himalayan derived 1500–2300 Ma zircons after 7.0 Ma is consistent with earlier records from the foreland basin the much greater rise after 1.9 Ma, shortly after a fall in Nd values after 3.4 Ma, has not previously been recognized and suggests that widespread unroofing of the Crystalline Lesser Himalaya and to a lesser extent Nanga Parbat did not occur until after 3.4 Ma. No simple links can be made between erosion and the development of the South Asian Monsoon, implying a largely tectonic control to Lesser Himalayan unroofing.