DOI: 10.57760/sciencedb.07471
title: Chemical weathering in the Himalayan system in response to the evolution of the Indian summer monsoon since 37 ka
title: 37 ka以来喜马拉雅系统风化过程对印度季风演化的响应记录

description: Based on clay mineralogy, siliciclastic grain sizes and geochemical records from deep-sea sediments in the central Bay of Bengal (BoB), the evolutionary history of the Indian summer monsoon and associated weathering process in the Himalayan system since 37 ka were reconstructed. Clay minerals and Th-La elements indicate a mixture of sediments originating from the Ganges-Brahmaputra (G-B) Rivers, Indo-Burman ranges/Irrawaddy River and Godavari-Krishna (G-K) Rivers. The Th-La quantitative reconstruction revealed that sediment supply from the G-B Rivers was reduced during a series of millennial-scale cold climate events (i.e., Younger Dryas and Heinrich Events) and the Last Glacial Maximum. By removing the control of sea-level factors on the percentage of clay minerals in the sediments, we suggest that the marked decrease in the illite chemistry index and the increase in the (illite+chlorite)/smectite ratio during cold climate periods reflect enhanced physical weathering and weakened chemical weathering in the Himalayan system. Comparing the contribution from the G-B Rivers and the sedimentation rates in different regions of the BoB, it was inferred that the sediments of the G-B Rivers were mostly deposited in the upper and middle Bengal Fan. During the Holocene, the Active Channel played a crucial role in delivering sediments from the G-B Rivers to the lower Bengal Fan. The decreased chemical index of alteration (CIA) and increased K₂O/TiO₂ ratio indicated the weakening of the Indian summer monsoon. At that moment, the Himalayan system was involved in cold climatic conditions accompanied by glacial extension, which led to enhanced physical weathering and increased sediment contributions from the highlands.
description: Based on clay mineralogy, siliciclastic grain sizes and geochemical records from deep-sea sediments in the central Bay of Bengal (BoB), the evolutionary history of the Indian summer monsoon and associated weathering process in the Himalayan system since 37 ka were reconstructed. Clay minerals and Th-La elements indicate a mixture of sediments originating from the Ganges-Brahmaputra (G-B) Rivers, Indo-Burman ranges/Irrawaddy River and Godavari-Krishna (G-K) Rivers. The Th-La quantitative reconstruction revealed that sediment supply from the G-B Rivers was reduced during a series of millennial-scale cold climate events (i.e., Younger Dryas and Heinrich Events) and the Last Glacial Maximum. By removing the control of sea-level factors on the percentage of clay minerals in the sediments, we suggest that the marked decrease in the illite chemistry index and the increase in the (illite+chlorite)/smectite ratio during cold climate periods reflect enhanced physical weathering and weakened chemical weathering in the Himalayan system. Comparing the contribution from the G-B Rivers and the sedimentation rates in different regions of the BoB, it was inferred that the sediments of the G-B Rivers were mostly deposited in the upper and middle Bengal Fan. During the Holocene, the Active Channel played a crucial role in delivering sediments from the G-B Rivers to the lower Bengal Fan. The decreased chemical index of alteration (CIA) and increased K₂O/TiO₂ ratio indicated the weakening of the Indian summer monsoon. At that moment, the Himalayan system was involved in cold climatic conditions accompanied by glacial extension, which led to enhanced physical weathering and increased sediment contributions from the highlands.