Clay minerals as paleo-climate proxy in Quaternary Dun sediments, NW Himalaya, India
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Date
2023-10-17T00:00:00
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Springer Science and Business Media Deutschland GmbH
Abstract
Purpose: Clay mineral assemblages are widely used for deciphering paleoclimatic information, where diagenetic and detrital clays provide different signatures. The type and amount of clay present in the alluvial fan sediments account for the prevailing climate, topography, transport dynamics, diagenesis, and lithology of the catchment area. Clay mineral analysis of sediments collected from the younger lobe of Kiratpur Fan, Pinjaur dun, NW Himalaya, will help to understand the late-Quaternary climatic perturbations during marine isotope stage (MIS)-3 and to evaluate the suitability of clay minerals as paleoclimatic proxy. Materials and methods: Samples were collected from three sites along the Kiratpur Nadi near Paploha village, Haryana, where exposed sections had a total height of ~ 28�m. In this study, 31 samples from these sediment sections were collected and after initial processing, clay minerals were separated and oriented slides were prepared. These samples were analysed using X-ray diffractometer (XRD) with/without glycolation and heating treatments. One aliquot of dried clay from selected samples were used for FTIR to complement the XRD analysis. For FTIR analysis, about 1�mg of clay samples was mixed with ~ 10�mg of KBr and press pellets were prepared. Results and discussion: The clay fraction of these sediments constitute illite (~ 52 � 0.8%), kaolinite (~ 13 � 1.6%), and chlorite-montmorillonite interstratified clay (~ 35 � 1.5%). Shale and mudstone distributed in the catchment area might be the source of these clay minerals. Illite chemistry index of ~ 0.37 � 0.14, kaolinite/illite ratio (0.21�0.29), illite crystallinity (IC) (0.23 � 0.04), and kaolinite percentage suggest the dominance of physical weathering in the catchment area. These sediments are generated during a cold and dry period, and deposited during an aggradational phase associated with warm and wet phase within MIS-3 (40�30 Ka). Further, it was found that illite is the dominant clay throughout the Himalayas, Ganga plain, and Bay of Bengal (BoB) sediments, irrespective of their distance from the source. Hence, associating illite to younger and less-transported sediment does not work in this setting. Conclusion: Though the proxies based on clay percentage is very useful, only limited data is available. There is a significant difference in the value of IC in the Himalayan front and BoB sediments may be due to the modifications during the transportation of sediments. Overall, when sediments are transported for a longer distance, correlating clay mineral percentage with the maturity of sediment is not apparent. � 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
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Keywords
Clay minerals, Illite chemistry index (ICI), Illite crystallinity (IC), Pinjaur Dun, Quaternary climate