Fluvio-Deltaic Response to Tectonic and Sea-Level Perturbations

Abstract:

Fluvio-deltaic deposits result from the interplay of upstream and downstream environmental conditions, such as upstream tectonic and downstream sea-level settings, making them prime records of past environments. Environmental conditions are far from static, and changes to these conditions create perturbations, or signals, that can propagate from both the upstream hinterlands and from the downstream receiving basin to the fluvio-deltaic realm. Our ability to interpret past environmental conditions from fluvio-deltaic deposits thus hinges on our understanding of fluvio-deltaic response to, and preservation of, environmental perturbations. Recent work suggests the internal dynamics of fluvio-deltaic systems can modify or completely destroy these signals, making them difficult or impossible to interpret from the sedimentary deposits. It has been shown that such signal modification or destruction is a function of both the signal timescales and system response timescales. However, it remains unclear which aspects of the fluvio-deltaic system most significantly control the interaction of these timescales and the extent to which the environmental signals are ultimately preserved in the deposits. To answer these questions, we numerically simulate fluvio-deltaic growth using a physics-based source-to-sink model of sediment transfer from upland source areas to coastal depositional basins. Preliminary results demonstrate that grain size and length scales of the fluvial system affect propagation of both tectonic and sea-level forcings, as well as the preservation style of the resulting signal in the architecture of the fluvio-deltaic deposits. Future work will focus on determining if these results are set by a relationship between grain size and fluvial system size with system response time.