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- Title
Timescales of Autogenic Noise in River Bedform Evolution and Stratigraphy.
- Authors
Ganti, Vamsi; Kelley, Madeline M.; Das, Debsmita; Mahon, Robert C.
- Abstract
Bedform evolution and preserved cross strata are known to respond to floods. However, it is unclear if autogenic dynamics mask the flood signal in bedform evolution and cross strata. To address this, we characterize the temporal structure of autogenic noise in steady‐state bedform evolution in a physical experiment. Results reveal the existence of bedform groups—quasi‐stable collections of bedforms—that migrate at a similar speed as bedforms. We find that bedform and bedform‐group turnover timescales are the key autogenic timescales of bed evolution that set the transition time‐periods between different noise regimes in bedform evolution. Results suggest that bedform‐group turnover timescale sets the lower limit for detecting flood signals in bedform evolution, and floods with duration shorter than bedform turnover timescale can be severely degraded in bedform evolution and cross strata. Our work provides a new framework for interrogating fluvial cross strata for reconstruction of past floods. Plain Language Summary: Bedforms are wavy features found regularly on the beds of rivers. Bedform deposits are the building blocks of the rock record on Earth and Mars. Bedforms and their deposits respond to floods; however, it is unclear if all floods are similarly represented in bedforms and their deposits. To address this, we identified the timescales over which bed elevation and sediment discharge are variable in a steady‐state experiment of bedform evolution using high‐resolution data. We investigated the time series of bed elevation to document the existence of bedform groups, which represent a collection of bedforms that have deep scours at their upstream and downstream end. We find that the turnover timescales (time required to move an entire land feature) of bedforms and bedform groups are the key controls on noise in bedform evolution. Results suggest that the signal of floods with duration less than bedform turnover timescale will not be found in bedform data and their deposits. However, floods with duration greater than the bedform‐group turnover timescale are likely to be expressed in bedform data and their deposits. These results provide a new theory for how floods are represented in river deposits. Key Points: We show the existence of bedform groups, which are quasi‐stable collections of bedforms, previously found in aeolian dune evolution modelsBedform and bedform group turnover timescales are key autogenic timescales that describe the temporal structure of noise in bed elevationFloods of duration shorter than bedform turnover timescale are expected to be unrecognizable in bed elevation and preserved cross strata
- Subjects
SAND dunes; RIVER channels; NOISE control; SOUND recordings; NOISE; TIME series analysis
- Publication
Geophysical Research Letters, 2024, Vol 51, Issue 11, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2024GL108965