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Low-gradient, single-threaded rivers prior to greening of the continents

Ganti, Vamsi and Whittaker, Alexander C. and Lamb, Michael P. and Fischer, Woodward W. (2019) Low-gradient, single-threaded rivers prior to greening of the continents. Proceedings of the National Academy of Sciences of the United States of America, 116 (24). pp. 11652-11657. ISSN 0027-8424. PMCID PMC6575162. doi:10.1073/pnas.1901642116.

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The Silurian-age rise of land plants is hypothesized to have caused a global revolution in the mechanics of rivers. In the absence of vegetation-controlled bank stabilization effects, pre-Silurian rivers are thought to be characterized by shallow, multithreaded flows, and steep river gradients. This hypothesis, however, is at odds with the pancontinental scale of early Neoproterozoic river systems that would have necessitated extraordinarily high mountains if such river gradients were commonplace at continental scale, which is inconsistent with constraints on lithospheric thickness. To reconcile these observations, we generated estimates of paleogradients and morphologies of pre-Silurian rivers using a well-developed quantitative framework based on the formation of river bars and dunes. We combined data from previous work with original field measurements of the scale, texture, and structure of fluvial deposits in Proterozoic-age Torridonian Group, Scotland—a type-example of pancontinental, prevegetation fluvial systems. Results showed that these rivers were low sloping (gradients 10^(−5) to 10^(−4)), relatively deep (4 to 15 m), and had morphology similar to modern, lowland rivers. Our results provide mechanistic evidence for the abundance of low gradient, single-threaded rivers in the Proterozoic eon, at a time well before the evolution and radiation of land plants—despite the absence of muddy and vegetated floodplains. Single-threaded rivers with stable floodplains appear to have been a persistent feature of our planet despite singular changes in its terrestrial biota.

Item Type:Article
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URLURL TypeDescription Information CentralArticle
Ganti, Vamsi0000-0003-2165-6052
Lamb, Michael P.0000-0002-5701-0504
Fischer, Woodward W.0000-0002-8836-3054
Additional Information:© 2019 National Academy of Sciences. Published under the PNAS license. Edited by Andrea Rinaldo, Swiss Federal Institute of Technology, Lausanne, Switzerland, and approved April 29, 2019 (received for review January 28, 2019). Code and Data Availability: All data generated or analyzed during this study are included in SI Appendix. We thank F. Macdonald, W. McMahon, and S. Gupta for useful discussions. V.G. acknowledges funding from the Imperial College London Junior Research Fellowship. Author contributions: V.G., A.C.W., M.P.L., and W.W.F. designed research; V.G. and A.C.W. performed research; V.G., A.C.W., and M.P.L. contributed new reagents/analytic tools; V.G., A.C.W., M.P.L., and W.W.F. analyzed data; and V.G., A.C.W., M.P.L., and W.W.F. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at
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Imperial College LondonUNSPECIFIED
Subject Keywords:prevegetation alluvium; cross-stratification; Neoproterozoic Era
Issue or Number:24
PubMed Central ID:PMC6575162
Record Number:CaltechAUTHORS:20190523-093030045
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Official Citation:Low-gradient, single-threaded rivers prior to greening of the continents. Vamsi Ganti, Alexander C. Whittaker, Michael P. Lamb, Woodward W. Fischer. Proceedings of the National Academy of Sciences Jun 2019, 116 (24) 11652-11657; DOI: 10.1073/pnas.1901642116
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95729
Deposited By: Tony Diaz
Deposited On:23 May 2019 17:09
Last Modified:16 Feb 2022 23:40

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