CaltechAUTHORS
  A Caltech Library Service

Autogenic Erosional Surfaces in Fluvio-deltaic Stratigraphy from Floods, Avulsions, and Backwater Hydrodynamics

Ganti, Vamsi and Lamb, Michael P. and Chadwick, Austin J. (2019) Autogenic Erosional Surfaces in Fluvio-deltaic Stratigraphy from Floods, Avulsions, and Backwater Hydrodynamics. Journal of Sedimentary Research, 89 (8). pp. 815-832. ISSN 1527-1404. https://resolver.caltech.edu/CaltechAUTHORS:20190920-081437779

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20190920-081437779

Abstract

Erosional surfaces set the architecture of fluvio-deltaic stratigraphy, and they have classically been interpreted in terms of changes in boundary conditions such as climate, tectonics, and base level (allogenic forces). Intrinsic dynamics of sedimentary systems (autogenic dynamics) can also create a rich stratigraphic architecture, and a major knowledge gap exists in parsing the relative roles of autogenic versus allogenic processes. Emerging theoretical and experimental work suggests that backwater hydrodynamics play an important role in driving transient channel incision in river deltas, even those experiencing net aggradation. Here, we identify and quantify two autogenic mechanisms that produce broad erosional surfaces in fluvio-deltaic stratigraphy, namely, floods and avulsions. Using a simple mass-balance model for single-threaded delta channel systems, we show that flood-induced scours begin near the shoreline, and avulsion-induced scours begin at the avulsion site, and both propagate upstream over a distance that scales with the backwater length, bed slope, and bed grain size. We also develop scaling relationships for the maximum scour depths arising from these mechanisms, which are functions of characteristic flow depth and formative flood variability. We test our theoretical predictions using a flume experiment of river delta evolution governed by persistent backwater hydrodynamics under constant relative sea level. Results indicate that autogenic dynamics of backwater-mediated deltas under conditions of constant base level can result in stratigraphic surfaces and shoreline trajectories similar to those often interpreted to represent multiple sea-level cycles. Our work provides a quantitative framework to decouple autogenic and allogenic controls on erosional surfaces preserved in fluvio-deltaic stratigraphy.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.2110/jsr.2019.40DOIArticle
ORCID:
AuthorORCID
Lamb, Michael P.0000-0002-5701-0504
Chadwick, Austin J.0000-0002-2552-0083
Additional Information:© 2019 SEPM (Society for Sedimentary Geology). Received 26 November 2018; accepted 3 May 2019. We thank Woodward Fischer and Elizabeth Trower for useful discussions. This work was supported by the Caltech Terrestrial Hazard Observation and Reporting program and National Science Foundation grant 1427177 to MPL. VG and MPL acknowledge additional support from the Junior Research Fellowship and the Royal Academy of Engineering Distinguished Visiting Professor Fellowship from the Imperial College London, respectively.
Funders:
Funding AgencyGrant Number
Caltech Terrestrial Hazard Observation and Reporting (THOR) CenterUNSPECIFIED
NSFEAR-1427177
Imperial College LondonUNSPECIFIED
Issue or Number:8
Record Number:CaltechAUTHORS:20190920-081437779
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190920-081437779
Official Citation:Vamsi Ganti, Michael P. Lamb, Austin J. Chadwick; Autogenic Erosional Surfaces in Fluvio-deltaic Stratigraphy from Floods, Avulsions, and Backwater Hydrodynamics. Journal of Sedimentary Research; 89(8): 815–832. doi: https://doi.org/10.2110/jsr.2019.40
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98768
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:20 Sep 2019 16:39
Last Modified:05 Nov 2019 17:56

Repository Staff Only: item control page