Enhanced exhumation in the East Karakoram during themid-Pleistocene climate transition: A detrital provenance assessment
- 1Swedish Museum of Natural History, Department of Geosciences, Stockholm, Sweden (chris.mark@nrm.se)
- 2Department of Earth Sciences, University College London, London, UK
- 3Institut de Physique du Globe de Paris, Paris, France
- 4Geological Survey of Pakistan, Quetta, Pakistan
- 5Department of Earth and Environmental Sciences, Università di Milano-Bicocca, Milan, Italy
Around the Nanga Parbat-Haramosh massif in the west and the Namche Barwa massif in the east, the Himalayan orogen exhibits an abrupt strike change from roughly E-W to N-S, forming two structural syntaxes. Each syntaxis is drained by a major trans-orogenic river system: the Indus and Ganges-Brahmaputra, respectively. The syntaxial massifs record rapid exhumation rates (up to c. 10 mm/a), together with Plio-Pleistocene mineral (re)crystallisation and cooling ages (Bracciali et al, 2016; Crowley et al., 2009; Zeitler et al., 1993). The Namche Barwa massif supplies c. 65-74% of Brahmaputra bedload (Enkelman et al., 2011; Dong et al., 2023). In contrast, the Nanga Parbat massif supplies c. 10% of modern Indus bedload, which instead is dominantly sourced from the East Karakoram (Clift et al, 2022).
We present detrital rutile and zircon U-Pb data from the Indus fan, sampled by IODP expedition 355 and ODP leg 117. These data record abrupt increases in the proportion of sediment sourced from the Nanga Parbat massif between c. 8-6 Ma and again at c. 2 Ma, coherent with bedrock studies (Crowley et al., 2009; Zeitler et al., 1993). The Nanga Parbat massif then dominates sediment supply until c. 1.5-0.6 Ma, followed by an abrupt switch to East Karakoram sourcing.
The East Karakoram includes some of Earth’s highest peaks, and largest extra-polar glaciers. Therefore, a provocative possibility is that the jump in erosion focus was driven by the switch from c. 41 ka, obliquity-dominated, to 100 kyr, eccentricity-dominated orbital forcing (the Mid-Pleistocene Transition). This transition occurred at c. 1 Ma (Clark et al., 2006), and could have driven enhanced glacially-mediated erosion in the east Karakoram, outpacing Nanga Parbat exhumation. Approximately synchronous increases in exhumation rate are also documented at Nanga Parbat-Haramosh massif, and the Namche Barwa massif (Guevara et al., 2022; Govin et al., 2020; King et al., 2016;).
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How to cite: Mark, C., Clift, P., Paolucci, C., Alizai, A., and Garzanti, E.: Enhanced exhumation in the East Karakoram during themid-Pleistocene climate transition: A detrital provenance assessment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11893, https://doi.org/10.5194/egusphere-egu24-11893, 2024.
