Geochemistry of buried river sediments from Ghaggar Plains, NW India: Multi-proxy records of variations in provenance, paleoclimate, and paleovegetation patterns in the Late Quaternary
Introduction
Interaction between tectonics and climate at variable spatial and temporal scales controls weathering and erosion in the catchment areas of major rivers in orogenic belts (Burbank et al., 2003, Clift et al., 2010). This influences fluvial processes such as river discharge, sediment flux, and channel migration that in turn shape the landscape in the region (Bookhagen et al., 2005). Both tectonic activities and climatic fluctuations have controlled the evolution of geomorphic landforms and sedimentary processes in the Himalayan hinterland as well as the Indus–Gangetic alluvial plains. Further, intensified monsoon phases and corresponding high sediment fluxes during the Late Quaternary suggest a link between millennial-scale climate change and surface processes in the northwest Himalaya (Bookhagen et al., 2005). Despite more than three decades of scientific studies suggesting the existence of a network of buried channels in the Ghaggar Plains in NW India, no effort has been made to obtain a detailed geochemical record of surface and in particular subsurface sediments from the Ghaggar Plains. Consequently, temporal changes in source weathering and provenance (as a result of climate change) for the Ghaggar alluvial sediments have not been established. Several studies have attempted to reconstruct the Quaternary paleoclimate of India using climate proxies in the alluvial sediments from the Ganga Plains (e.g., Galy and France-Lanord, 2001, Galy et al., 2008a, Singh et al., 2008, Lupker et al., 2012). Similar attempts have been made in the adjoining Thar region of Rajasthan, NW India using pedogenic calcretes, and lake and aeolian sediments (Singh et al., 1974, Bryson and Swain, 1981, Singhvi et al., 1982, Wasson et al., 1983, Wasson et al., 1984, Singh et al., 1990, Andrews et al., 1998, Jain and Tandon, 2003, Achyuthan et al., 2007). However, paleoclimatic reconstruction attempts on the basis of fluvial proxies in the NW India have been rather limited (e.g., Tripathi et al., 2004, Jain et al., 2005). A compilation of results on the strength of SW monsoon variability derived from continental (lake and desert sediments) proxies in the NW India and marine proxies in Arabian Sea is presented in Fig. 1.
Several researchers have used the temporal variations in 87Sr/86Sr and 143Nd/144Nd isotopic ratios in the bulk silicate fractions of alluvial sediments as a proxy to identify provenance and to infer catchment erosion in the Himalaya in response to climate change (Singh et al., 2008, Rahaman et al., 2009, Derry and France-Lanord, 1996). These studies demonstrated the climate-controlled erosion of the Himalayan sources. On the other hand, studies on the Ghaggar Plains (e.g., Tripathi et al., 2004) have not provided a clear picture of climate-controlled sedimentation dynamics. The objective of this study is to use the geochemical record of buried sediments from the Ghaggar Plains of NW India to infer temporal variations in sediment provenance, source weathering/erosion in response to climate change (glacial/interglacial periods), during the Late Quaternary. Two drilled sediment cores (~ 40–45 m deep), raised along a single transect across the buried channel and close to the modern Ghaggar river channel, near the Kalibangan village, Rajasthan, were analyzed to obtain multiple geochemical data. The 87Sr/86Sr and 143Nd/144Nd ratios in bulk silicates, δ13C and δ18O in carbonate nodules, and δ13C of sediment organic matter in the stratigraphically-controlled samples constrained by optically stimulated luminescence (OSL) ages are compared to the available geochemical records from the NW India and the Indo-Gangetic Plains. Detailed subsurface geochemical records of fluvial sediments from NW India presented here complement the readily available extensive fluvial record from the Ganga Plains.
Section snippets
Sampling and analytical methods
In this study, sediment samples were taken from two (~ 45 m deep) drill cores raised along a single transect across a buried channel, mapped by Sinha et al. (2013), near the village of Kalibangan in Rajasthan (Fig. 2a). The core sites are located on the trace of the buried channel (Yashpal et al., 1980, Sinha et al., 2013) of a large river system presumably sourced in the Himalayan hinterland (Oldham, 1893, Stein, 1942, Valdiya, 1996). The GS-10 drill core is located at the center of the trace of
Elemental geochemistry of bulk silicates
The concentrations of major oxides (wt.%) and selected trace elements (ppm) in the carbonate-free core sediments are provided in Supplementary Tables 3 to 6. All the major element data were normalized to 100% on an anhydrous basis and used in the relevant figures here. Fig. 3 shows the range of variations in major oxides against Al2O3 in the GS core sediments. The Al2O3 content in the GS sediments shows a strong negative correlation (r2 = 0.96) with SiO2, and positive correlations with Fe2O3 (r2 =
Inferences on fluvial depositional settings
The integration of resistivity data and drill cores has provided important insights for fluvial stratigraphy and depositional settings. The stratigraphic architecture reconstructed by Sinha et al. (2013), based on the resistivity data along the same transect on which the cores GS-10 and GS-11 lie, suggested changes in the fluvial setting from that of a wide-channel braided river system (high energy) to an incised channel system, and subsequently to a narrow-channel seasonal river system. These
Conclusions
This study presents a first detailed record of the geochemistry of buried channel sand down to ~ 40–45 m depths beneath the Ghaggar Plains in NW India. Sediment geochemistry is used to establish temporal variations in sediment provenance vis-à-vis climate variability. The 87Sr/86Sr and 144Nd/143Nd ratios in bulk silicate fractions of the core sediments plot between the Higher and Lesser Himalayan endmember sources. Isotopic ratios clearly indicate that the sediments representing buried channel
Acknowledgments
This paper is a part of the Ph.D. thesis of AS at IIT Kanpur. We thank Dr. Sunil K. Singh of PRL Ahmedabad, and Dr. David Hodell of Cambridge University for their help in isotope analyses. Thanks are also due to Mohd. Amir for doing the stable isotopic analyses at IIT Kanpur. We also thank Drs. Sampat K. Tandon and Christian France-Lannord for insightful discussions. Finally, we thank two anonymous reviewers and Prof. Thomas Algeo (Editor) for a thoughtful and thorough review.
References (100)
- et al.
Stable isotopic composition of pedogenic carbonates from the eastern margin of the Thar Desert, Rajasthan
India. Quat. Int.
(2007) - et al.
Variability of Indian monsoonal rainfall over the past 100 ka and its implication for C3–C4 vegetational change
Quat. Res.
(2012) - et al.
Sediment provenance, reworking and transport processes in the Indus River by U–Pb dating of detrital zircon grains.
Glob. Planet. Chang.
(2011) - et al.
Do stable isotope data from calcrete record Late Pleistocene monsoonal climate variation in the Thar Desert of India?
Quat. Res.
(1998) - et al.
Does burial diagenesis reset pristine isotopic compositions in paleosol carbonates?
Earth Planet. Sci. Lett.
(2010) - et al.
The Lu–Hf and Sm–Nd isotopic composition of CHUR: constraints from unequilibrated chondrites and implications for the bulk composition of terrestrial planets
Earth Planet. Sci. Lett.
(2008) - et al.
Holocene variations of monsoon rainfall in Rajasthan
Quat. Res.
(1981) - et al.
Neogene Himalayan weathering history and river 87Sr/86Sr: impact on the marine Sr record
Earth Planet. Sci. Lett.
(1996) - et al.
Variations of the monsoon regime during the upper quaternary: evidence from carbon isotopic record of organic matter in North Indian sediment cores
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(1986) - et al.
C4 plants decline in the Himalayan basin since the Last Glacial Maximum
Quat. Sci. Rev.
(2008)