The flexural isostatic response of climatically driven sea-level changes on continental-scale deltas

Abstract. The interplay between climate-forced sea-level change, sediment erosion and deposition, and flexural adjustments in deep time on passive margin deltas remains poorly understood. We performed a series of conceptual simulations to investigate flexural isostatic responses to high-frequency fluctuations in water and sediment load associated with climatically driven sea-level changes. We model a large drainage basin that discharges to a continental margin to generate a deltaic depocenter, then prescribe synthetic and climatic-driven sea-level curves of different frequencies to assess flexural response. Results show that flexural isostatic adjustments are bidirectional over 100–1000 kyr timescales and are in sync with the magnitude, frequency, and direction of sea-level fluctuations, and that isostatic adjustments play an important role in driving along-strike and cross-shelf river-mouth migration and sediment accumulation. Our findings demonstrate that climate-forced sea-level changes produce a feedback mechanism that results in self-sustaining creation of accommodation into which sediment is deposited and plays a major role in delta morphology and stratigraphic architecture.