No modern Irrawaddy River until the late Miocene-Pliocene

Jonell, T. N. , Giosan, L., Clift, P. D., Carter, A., Bertschneider, L., Hathorne, E. C.,, Barbarano, M., Garzanti, E., Vezzoli, G. and Naing, T. (2022) No modern Irrawaddy River until the late Miocene-Pliocene. Earth and Planetary Science Letters, 584, 117516. (doi: 10.1016/j.epsl.2022.117516)

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The deposits of large Asian rivers with unique drainage geometries have attracted considerable attention due to their explanatory power concerning tectonism, surface uplift and upstream drainage evolution. This study presents the first petrographic, heavy mineral, Nd and Sr isotope geochemistry, and detrital zircon geochronology results from the Holocene Irrawaddy megadelta alongside modern and ancient sedimentary provenance datasets to assess the late Neogene evolution of the Irrawaddy River. Contrary to models advocating a steady post-middle Miocene river, we reveal an evolution of the Irrawaddy River more compatible with regional evidence for kinematic reorganization in Myanmar during late-stage India-Asia collision. Quaternary sediments are remarkably consistent in terms of provenance but highlight significant decoupling amongst fine and coarse fraction 87Sr/86Sr and due to hydraulic sorting. Only well after the late Miocene do petrographic, heavy mineral, isotope geochemistry, and detrital zircon U–Pb results from the trunk Irrawaddy and its tributaries achieve modern-day signatures. The primary driver giving rise to the geometry and provenance signature of the modern Irrawaddy River was regional late Miocene (≤10 Ma) basin inversion coupled with uplift and cumulative displacement along the Sagaing Fault. Middle to late Miocene provenance signatures cannot be reconciled with modern river geometries, and thus require significant loss of headwaters feeding the Chindwin subbasin after ∼14 Ma and the northern Shwebo subbasin after ∼11 Ma. Large-scale reworking after ∼7 Ma is evidenced by modern Irrawaddy River provenance, by entrenchment of the nascent drainage through Plio-Pleistocene inversion structures, and in the transfer of significant sediment volumes to the Andaman Sea.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Jonell, Dr Tara
Creator Roles:
Jonell, T. N.Conceptualization, Data curation, Formal analysis, Methodology, Visualization, Writing – original draft, Writing – review and editing
Authors: Jonell, T. N., Giosan, L., Clift, P. D., Carter, A., Bertschneider, L., Hathorne, E. C.,, Barbarano, M., Garzanti, E., Vezzoli, G., and Naing, T.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Earth and Planetary Science Letters
ISSN (Online):1385-013X
Published Online:04 April 2022
Copyright Holders:Copyright © 2022 The Authors
First Published:First published in Earth and Planetary Science Letters 584: 117516
Publisher Policy:Reproduced under a Creative Commons License

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