Geochemical Characterization and Provenance Study of Glacial Lake Deposits of the Badrinath Valley

Nayak, Kalyani (2015) Geochemical Characterization and Provenance Study of Glacial Lake Deposits of the Badrinath Valley. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Kalyani Nayak (10MS55)) Kalyani_Nayak-10MS55.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

In the Himalayan range imprint of Quaternary glaciations are preserved in the form of well-developed moraines, valley fills and relict lake deposits that exceed several tens of meters in thickness. Towards the growth of the valley glaciers in the Himalaya, the Indian Summer Monsoon (ISM) and Westerlies are major source of moisture. Hence changes in the extent of valley glaciers can be used to reconstruct the past precipitation and temperature. These changes are manifested in the pattern of distribution of the glacial sediments. In this study sediment samples were collected from a relict glacio-fluvial lake deposits found in both the bank of the Alaknanda river in Badrinath valley. The provenance, extent of weathering in the source and time of deposition of the sediments were estimated using textural, bulk mineralogy, major, trace, REE analysis and OSL dating of the sediment sample. During various processes of sediment production and transportation, distribution of several immobile trace elements such as Sc, Th, Zr, Cr, Ni Co and REEs are limited in the sediments, therefore, they used as provenance indicator. In addition to the provenance, the nature and extent of weathering at the source of the sediment, which reflects the prevailing climatic and tectonic condition, can be decipher from the different oxide and trace element ratio of the sediments. Grain size analysis of the sediment shows moderate to poorly sorted sediments and the textural group lies between fine-silt to slightly-fine-gravelly-medium-sand, indicating mixed sediment sizes. Based on the various immobile and mobile major oxide ratios it is inferred that the combination of different processes such as weathering and sorting have played a major role in progressively changing the geochemistry of the sediment from source rock. The ternary diagram of La, Th, Sc of sediments and different ratio plots indicate granitic to granodioritic source rocks mainly found in the HHCS. The fractionated REE patterns and the significant negative Eu anomalies indicate highly differentiated source rock. The CIA values of the sediment indicate moderate chemical weathering. Time of deposition of sediments indicates three phases of deposition and Comparison of the timing of depositions of the sediments with other geochemical studies it is clear that the weathering rate is slightly lower around LGM as compared to after LGM period.

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