24-8 Sediment Sources and Routing in the Ganges-Brahmaputra River System based on Detrital Zircon U-Pb Geochronology

Session: Advances and Applications in Geochronology for Interpreting Stratigraphic and Basin Records, Part I

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Abstract:

The Ganges and Brahmaputra Rivers (GB) represent one of Earths largest river systems. Understanding sediment dynamics in the GB River system requires an understanding of the source-to-sink sediment routing. This study utilizes detrital zircon (DZ) U-Pb age distributions from modern rivers throughout the GB system to reveal the sources, routing and spatial changes of sediment contributions from the upstream Himalayan regions to the downstream Bay of Bengal and is based on DZ U-Pb signature described by Blum et al., 2018 from the IODP 354 Bengal Fan samples.

Preliminary results show the signatures of the Himalayan source terrains which is more or less the same in the Brahmaputra and its tributaries, a major contribution from the Lhasa Gangdese arc (ca. 0-300 Ma), Greater Himalayan Sequence (GHS) or Lhasa (ca. 400-600 Ma) however the Ganges signatures show very little or no contribution of ca. 0-300 Ma and less contribution of ca. 400-600 Ma compared to the Brahmaputra signatures. Additionally, the DZ signatures after the two rivers merge indicate mixing of the upstream Brahmaputra contribution with the upstream Ganges contribution even though the contribution from these two rivers varies significantly. These changes result from tectonics, climate change and autogenic processes indicating uplifts and erosion from the Gangdese arc and GHS in the Himalayas and contribution to the Brahmaputra drainage whereas little or no contribution to the Ganges drainage and autogenic river avulsion or delta building downstream.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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