EVENT-BASED STRATIGRAPHIC SIMULATION OF WAVE-DOMINATED SHALLOW-MARINE ENVIRONMENTS

Abstract

The presence of event beds in the shallow-marine stratigraphic record indicates formation is governed by high magnitude-low frequency processes rather than low magnitude-high frequency processes. In this paper, a 2-D multiple grain-size process-response model (BARSIM) is presented, which uses event deposition to simulate stratigraphic response to changes in sea level and sediment supply. BARSIM uses variable time steps to simulate individual storm (event) and fair-weather periods. Deposition during storm conditions solely consists of reworked shoreface sediment, while fair-weather deposits consist of reworked shoreface sediment combined with sediment supplied by littoral drift and suspension. Simulations using variations in sea level, sediment supply (both amount and grain-size) and wave-height regime result in distinct depositional patterns, stratal geometry and bed characteristics. Model results indicate that both wave-height regime and grain-size of supplied sediment have considerable effect on shoreface morphology and stratal characteristics. Unraveling coastal evolution from the shallow-marine stratigraphic record may therefore be more difficult than previously assumed, as both variables are expected to vary over geologic time scales.