Complex Pattern of Sediment Erosion and Deposition under Sea-Level Changes: Insights from a Coupled Stratigraphic Experiments and Numerical Modelling for Fluvio-Deltaic Evolution
Presentation Type
Poster
Faculty Advisor
Jorge Lorenzo Trueba
Access Type
Event
Start Date
26-4-2024 11:15 AM
End Date
26-4-2024 12:15 PM
Description
The subsurface structure of the fluvial delta provides evidence of previous climate and sea-level (SL) changes, which can be reconstructed through stratigraphy. A key challenge when inverting stratigraphy is differentiating between external forcing signals, such as SL fluctuations, and internal processes, such as variations in the fluvial surface and channel network dynamics. A study on the Tulane Delta Basin, using an experimental run with oscillating SL conditions and constant sediment supply, revealed that the dynamics of the fluvial surface play an important role in delaying the response of the upper portion of the subaerial topset. To quantify this phenomenon, we couple this experiment with a numerical modeling framework that integrates the topset with a subaqueous offshore region or foreset. This model can explain the topset slope, convexity dynamics, and sediment partitioning between the topset and the foreset under SL variations. Specifically, it captures the subaerial slope decrease and convexity increase due to low sedimentation during sea-level rise (SLR) and the increase in slope and concavity due to high sedimentation during sea-level fall (SLF) near the center of the topset. Moreover, the model can explain the counterintuitive observation of higher sediment topset bypass to the foreset under SLR than SLF due to the reduction in subaerial slope, partially explained by a higher presence of active channels during SLR than SLF. These results underscore the importance of internal processes, which can result in net erosion during SLR and net deposition during SLF, potentially complicating the reconstruction of paleo sea-level from deltaic deposits.
Complex Pattern of Sediment Erosion and Deposition under Sea-Level Changes: Insights from a Coupled Stratigraphic Experiments and Numerical Modelling for Fluvio-Deltaic Evolution
The subsurface structure of the fluvial delta provides evidence of previous climate and sea-level (SL) changes, which can be reconstructed through stratigraphy. A key challenge when inverting stratigraphy is differentiating between external forcing signals, such as SL fluctuations, and internal processes, such as variations in the fluvial surface and channel network dynamics. A study on the Tulane Delta Basin, using an experimental run with oscillating SL conditions and constant sediment supply, revealed that the dynamics of the fluvial surface play an important role in delaying the response of the upper portion of the subaerial topset. To quantify this phenomenon, we couple this experiment with a numerical modeling framework that integrates the topset with a subaqueous offshore region or foreset. This model can explain the topset slope, convexity dynamics, and sediment partitioning between the topset and the foreset under SL variations. Specifically, it captures the subaerial slope decrease and convexity increase due to low sedimentation during sea-level rise (SLR) and the increase in slope and concavity due to high sedimentation during sea-level fall (SLF) near the center of the topset. Moreover, the model can explain the counterintuitive observation of higher sediment topset bypass to the foreset under SLR than SLF due to the reduction in subaerial slope, partially explained by a higher presence of active channels during SLR than SLF. These results underscore the importance of internal processes, which can result in net erosion during SLR and net deposition during SLF, potentially complicating the reconstruction of paleo sea-level from deltaic deposits.