EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Bengal Fan sediment archive: a record of Himalayan tectonics, climate, and/or drainage routing change between source and sink?

Yani Najman1, Mike Blum2, Jamie Gleason3, Kimberly Rogers4, Devon Orme5, Chris Mark6, Dan Barfod7, Andy Carter8, Randy Parrish9, Dave Chew10, and Lorenzo Gemignani11
Yani Najman et al.
  • 1Lancaster University, LEC, Lancaster, United Kingdom of Great Britain and Northern Ireland (
  • 2University of Kansas, USA
  • 3University of Michigan, USA
  • 4University of Colorado, Boulder, USA
  • 5Montana State University, USA
  • 6University College Dublin, Ireland
  • 7SUERC, UK
  • 8Birkbeck, and UCL, London, UK
  • 9Portsmouth University, UK
  • 10Trinity College Dublin, Ireland
  • 11Free University, Berlin, Germany

The Bengal Fan IODP Exp 354 core provides a Neogene re­cord of eastern and central Himalayan exhu­mation. U-Pb analyses of detrital zircons from this sediment archive shows that from ~ 4 Ma, there was a major increase in grains aged <300 Ma, indicating a major increase in contribution from the Trans-Himalaya (Blum et al., Nature SR, 2018). Detrital rutile U-Pb and detrital zircon fission track data from the same archive (Najman et al, GSAB 2019) indicates an approximately coeval increase in exhumation rate from the Eastern Himalayan Syntaxis. Thus an attractive explanation to explain the increase in Transhimalayan input may be that it was caused by initiation of exhumation of the syntaxis from beneath its Transhimalayan cover. However, a similar dataset obtained from the proximal foreland basin Siwalik deposits (Govin et al., in review) indicates an earlier onset to syntaxial exhumation, compared to that recorded in the distal sediment archive. We consider therefore whether climate change may be responsible for the increased Transhimalayan input: onset of Northern Hemisphere glaciation may have increased the proportion of erosion in the higher, glaciated, regions of the Transhimalaya, compared to that part of the orogen south of the suture zone. Analyses of Hf isotopic composition of detrital zircons to assess the possibility that drainage basin changes may explain the increase in material at 4 Ma, are ongoing. The difference in timing of the syntaxial exhumational signal between the proximal and distal archives may be the result of downstream dilution, or may result from sequestration of material on the shelf, with release to the deep ocean during sea level low stands.

How to cite: Najman, Y., Blum, M., Gleason, J., Rogers, K., Orme, D., Mark, C., Barfod, D., Carter, A., Parrish, R., Chew, D., and Gemignani, L.: The Bengal Fan sediment archive: a record of Himalayan tectonics, climate, and/or drainage routing change between source and sink?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3798,, 2020

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