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What Difference Does a Eustatic Curve Make?

Abstract

Eustasy is thought to be a critical control on the distribution of sediment in basin margins and is used in conceptual stratigraphic models to predict the location of sand-rich deposits and explain basin development. We used a nonlinear, diffusion-based numerical forward stratigraphic model in a synthetic basin to test the impact of the widely cited eustatic curves of Haq et al. (1987) and Kominz et al. (2008) on sand distribution. These eustatic curves are distinctly different on the million-year scale in amplitude and frequency. The eustatic record of Haq et al. (1987) has higher amplitude, low frequency fluctuations compared to the Kominz et al. (2008) record. We hypothesize these dissimilarities should result in different loci of sand deposition. The question is: How different? Overall, the Haq model was marginally more effective than the Kominz model at delivering sand to deep water, particularly on the slope and distal part of the basin directly in front of the sediment point source. The large, low frequency short-term eustatic falls of the Haq model resulted in broad deep-water sediment and sand accumulation events. The low amplitude, high frequency short-term eustatic falls of the Kominz model resulted in more punctuated deposition of sediment, with a larger volume of sand distributed across the outer shelf and upper slope. This experimental framework quantitatively demonstrates the impact of two well-known eustatic curves on large-scale deposition and allows for investigation of the processes that lead to the development of the stratigraphic record.