Water discharge variations control fluvial stratigraphic architecture in the Middle Eocene Escanilla formation, Spain

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1038/s41598-023-33600-6. This is version 2 of this Preprint.

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Authors

Nikhil Sharma , Alexander C Whittaker, Stephen E. Watkins, Luis Valero, Jean Vérité, Cai Puigdefàbregas, Thierry Adatte, Miguel Garcés, François Guillocheau, Sebastien Castelltort 

Abstract

Ancient fluvial deposits typically display repetitive changes in their depositional architecture such as alternating intervals of coarse-grained highly amalgamated (HA), laterally-stacked, channel bodies, and finer-grained less amalgamated (LA), vertically-stacked, channels encased in floodplain deposits. Such patterns are usually ascribed to slower, respectively higher, rates of base level rise (accommodation). However, “upstream” factors such as water discharge and sediment flux also play a potential role in determining stratigraphic architecture, yet this possibility has never been tested despite the recent advances in the field of palaeohydraulic reconstructions from fluvial accumulations. Here, we chronicle riverbed gradient evolution within three Middle Eocene (~ 40 Ma) fluvial HA-LA sequences in the Escanilla Formation in the south-Pyrenean foreland basin. This work documents, for the first time in a fossil fluvial system, how the ancient riverbed systematically evolved from lower slopes in coarser-grained HA intervals, and higher slopes in finer-grained LA intervals, suggesting that bed slope changes were determined primarily by climate-controlled water discharge variations rather than base level changes as often hypothesized. This highlights the important connection between
climate and landscape evolution and has fundamental implications for our ability to reconstruct ancient hydroclimates from the interpretation of fluvial sedimentary sequences.

DOI

https://doi.org/10.31223/X56S7V

Subjects

Earth Sciences, Geology, Geomorphology, Hydrology, Sedimentology, Stratigraphy

Keywords

stratigraphy, Palaeohydraulics, fluvial sedimentology

Dates

Published: 2022-07-27 05:58

Last Updated: 2023-04-28 18:09

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License

CC BY Attribution 4.0 International

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Conflict of interest statement:
The authors declare no competing interests.