Abstract

Patterns of delta progradation in rapidly subsiding basins have been used previously as a proxy for Quaternary sea-level change. Major transgression surfaces and maximum lowstand positions are readily recognizable in seismic reflection profiles. Quaternary sea-level change can be approximated by stacked and tuned oxygen isotope records, but significant departures from this proxy result from variation in isotopic composition of ice sheets, temperature variations in the deep sea, and the effect of bioturbation in degrading the isotopic record. We analyze the influence of rapid Quaternary sea-level change on delta progradation in the eastern Mediterranean using DELTA, a multi-process sediment transport model. Subsidence rates and sediment inputs may vary through time, but compared to Quaternary sea-level change, such variations were minor and had little effect on model results. For a variety of geologically reasonable sediment inputs and subsidence rates, the delta architecture observed in seismic profiles could not be reproduced when the sea-level estimates were taken directly from a scaled global oxygen isotopic curve. However, when this sea-level curve was corrected to include independent estimates of sea level from geological data elsewhere in the world, previously used sediment inputs and subsidence rates invariably predict the general form of the observed architecture. The difference between isotopic and geological estimates of sea level for the last 200 ka follows a linear trend that was applied to previous glacial-interglacial cycles, producing a corrected sea-level history for the last 540 ka. Using DELTA over this time span, the sea-level history based directly on the oxygen isotope curve was again less able to reproduce the observed delta architecture compared with a corrected sea-level history. This study shows the importance of modeling delta progradation as an avenue for testing and exploring Quaternary sea-level history.

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