Hydrology, Cryosphere & Earth Surface Editors' Highlights

Formation of Sedimentary Deposits: Bypass Versus Mass Extraction

Grain size and sediment delivery pathways from the Ganges delta have been used to model downstream facies changes.

Source: Journal of Geophysical Research: Earth Surface


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Large river systems such as the Ganges and Brahmaputra carry vast amounts of sediment eroded from mountainous regions and deposit them in low lying areas. Patterns of sediment dispersal in these systems provide clues to tectonic and climatic events of the past. It is quite straight-forward to measure differences in grain size over a particular geographic area; more challenging is understanding the subsurface heterogeneity of sedimentary deposits.

Sincavage et al. [2019] couple data on grain size and sediment volumes with a similarity solution model to predict downstream facies changes. They apply models for sediment mass extraction and downstream fining to predict grain size trends observed from the mid-Holocene Ganges-Brahmaputra-Meghna Delta (GBMD), Bangladesh. This is one of few such studies to analyze sedimentary facies changes quantitatively at this scale in the field, and therefore makes an important scientific contribution towards facies prediction.

The authors find that the streamwise point at which approximately 80 percent of the sediment has been extracted corresponds to a transition from sand to mud-dominated facies. Mass extraction as a predictive tool for subsurface heterogeneity has the potential to be a significant analytical tool because it requires “simple” data collection about particle size and deposited sediment volume.

Possible applications of being able to better predict subsurface pathways for fluid flow, relevant to Bangladesh and many other densely-populated delta regions of the world, include the management of water resources as well as hydrocarbon reservoirs.

Citation: Sincavage, R. S., Paola, C., & Goodbred, S. L. [2019]. Coupling mass extraction and downstream fining with fluvial facies changes across the Sylhet basin of the Ganges‐Brahmaputra‐Meghna delta. Journal of Geophysical Research: Earth Surface, 124. https://doi.org/10.1029/2018JF004840

—Amy East, Editor-in-Chief, JGR: Earth Surface

Text © 2019. The authors. CC BY-NC-ND 3.0
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